THE SCIENCE OF DISCWORLD...DISCWORLD IS REAL. It's the way worlds should work. Admittedly, it is...

301

Transcript of THE SCIENCE OF DISCWORLD...DISCWORLD IS REAL. It's the way worlds should work. Admittedly, it is...

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THESCIENCEOFDISCWORLD

3

Darwin'sWatch

TERRYPRATCHETT

JACKCOHEN

IANSTEWART

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CONCERNINGROUNDWORLD

DISCWORLDISREAL.It'sthewayworldsshouldwork.Admittedly,itisflatandgoesthroughspaceonthebacksoffourelephantswhichstandontheshelofagiantturtle,butconsiderthealternatives.Consider,forexample,aglobularworld,amerecrustuponaninfernoofmoltenrockandiron.Anaccidentalworld,madeofthewreckageofoldstars,thehomeoflifewhich,nevertheless,inamostunhomelyfashion,isregularlyscythedfromitssurfacebyice,gas,inundationorfalingrockstravelingat20,000

milesanhour.

Suchanimprobableworld,andtheentirecosmosthatsurroundsit,wasinfactaccidentalycreatedbythewizardsofUnseenUniversity.[1]ItwastheDeanofUnseenUniversitywhoinfactdestabilisedtherawfirmamentbyfiddlingwithit,possiblyleadingtothebelief,iffolkmemoryextendstosub-sub-sub-sub-atomicparticlelevel,thatitwasindeedaldonebysomebodywithabeard.

Infiniteinsizeontheinside,butaboutafootacrossontheoutside,theuniverseofRoundworldisnowkeptinaglassglobeinUU,whereithasbeenthesourceofmuchinterestandconcern.

Mostly,it'sthesourceofconcern.Alarmingly,itcontainsnonarrativium.

Narrativiumisnotanelementintheacceptedsense.Itisan[1]ThegreatestschoolofmagicontheDiscworld.Butsurelyyouknowthis?

attributeofeveryotherelement,thusturningtheminto,inanoccultsense,molecules.Ironcontainsnotjustiron,butalsothestoryofiron,thehistoryofiron,thepartofironthatensuresthatitwilcontinuetobeironandhasaniron-likejobtodoandisnot,forexample,cheese.Withoutnarrativium,thecosmoshasnostory,nopurpose,nodestination.

Nevertheless,undertheancientmagicalruleofAsAbove,SoBelow,thecrippleduniverseofRoundworldstrivesatsomeleveltocreateitsownnarrativium.Ironseeksoutotheriron.Thingsspin.Intheabsenceofanygodstodothecreatingoflife,lifehasmanaged,againsttheodds,tocreateitself.Yetthehumanswhohaveevolvedontheplanetbelieveintheirheartsthattherearesuch

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thingsasgods,magic,cosmicpurposeandmilion-to-onechancesthatcropupninetimesoutoften.Theyseekstoriesintheworldwhichtheworld,regrettably,isnotequippedtotel.

Thewizards,feelingsomewhatguiltyaboutthis,haveintervenedseveraltimesinthehistoryofRoundworldwhenitseemedtothemtobeonthewrongtrack.Theyencouragedfish(orfish-likecreatures)toleavetheseas,theyvisitedtheproto-civilisationsofdinosaur-descendantsandcrabs,theydespairedatthewayiceandfalingcometswipedouthigherlifeformssooften-andtheyfoundsomemonkeyswhowereobsessedwithsexandwerequicklearners,especialyifsexwasinvolvedorcould,byconsiderableingenuity,bemadetobeinvolved.

Againthewizardsintervened,teachingthemthatfirewasnotforhavingsexwithandingeneralencouragingthemtogetofftheplanetbeforethenextbigextinction.

InthistheyhavealbeenguidedbyHex,UU'smagicalthinkingengine,whichisimmenselypowerfulinanycase,andwithRoundworld,whichfromHex'spointofviewisameresub-routineofDiscworldandispracticalygodlike,althoughmorepatient.

Thewizardsthink'theyhavesorteditalout.ThemonkeyshavelearnedabouttheirpermanentlythreatenedworldviaatypeoftechnomancycaledScienceandmayyetescapefrozendoom.

Andyet...

Thethingaboutbestlaidplansisthattheydon'toftengowrong.Theysometimesgowrong,butnotoften,becauseofhavingbeen,asaforesaid,thebestlaid.Thekindofplanslaidbywizards,whobargein,shoutalot,trytosortitaloutbylunchtimeandhopeforthebest,ontheotherhand...

wel,theygowrongalmostinstantly.

ThereisakindofnarrativiumonRoundworld,ifyourealylook.

OnDiscworld,thenarrativiumofafishtelsitthatitisafish,wasafish,andwilcontinuetobeafish.OnRoundworld,somethinginsideafishtelsitthatitisafish,wasafish...andmighteventualybesomethingelse...

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...perhaps.

ONE

ANYOTHERBUSINESS

ITWASRAINING.THISWOULD,ofcourse,begoodfortheworms.

ThroughthetricklesthatcourseddownthewindowCharlesDarwinstaredatthegarden.

Worms,thousandsofthem,outthereunderthesoftrain,turningthedetritusofwinterintoloam,buildingthesoil.How...convenient.

TheploughsofGod,hethought,andwinced.ItwastheharrowsofGodthatplaguedhimnow.

Strangehowtherustleoftherainsoundsverymuchlikepeoplewhispering...

Atwhichpoint,hebecameawareofthebeetle.Itwasclimbinguptheinsideofthewindow,agreenandbluetropicaljewel.

Therewasanotherone,higherup,bangingfruitlesslyagainstthepane.

Onelandedonhishead.

Theairfiledupwiththerattleandslitherofwings.Entranced,Darwinturnedtolookattheglowingcloudinthecorneroftheroom.Itwasformingashape...

ItisalwaysusefulforauniversitytohaveaVeryBigThing.Itoccupiestheyoungermembers,tothereliefoftheirelders(especialyiftheVBTisbasedatsomedistancefromtheseatoflearningitself)anditusesupalotofmoneywhichwouldotherwiseonlyliearoundcausingtroubleorbespentbythesociologydepartmentor,probably,both.Italsohelpsinpushingbackboundaries,anditdoesn'tmuchmatterwhatboundariestheseare,sinceasanyresearcherwiltelyouit'sthepushingthatmatters,nottheboundary.

It'sagoodidea,too,ifit'sabiggerVBTthananyoneelse'sand,inparticular,sincethiswasUnseenUniversity,thegreatestmagicaluniversityintheworld,ifit'sabiggeronethantheonethosebastardsarebuildingatBraseneckColege.

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Ìnfact,'saidPonderStibbons,HeadofInadvisablyAppliedMagic,`theirsisrealyonlyaQBT,orQuiteBigThing.Actualy,they'vehadsomanyproblemswithit,it'sprobablyonlyaBT!'

Theseniorwizardsnoddedhappily.

Àndoursiscertainlybigger,isit?'saidtheSeniorWrangler.

Òh,yes,'saidStibbons.`BasedonwhatIcandeterminefromchattingtothepeopleatBraseneck,ourswilbecapableofpushingboundariestwiceasbiguptothreetimesasfar.'

'Ihopeyouhaven'ttoldthemthat,'saidtheLecturerinRecentRunes.`Wedon'twantthembuildinga...a...anEBT!'

Àwhat,sir?'saidPonderpolitely,histonesaying,ÌknowaboutthissortofspecialthingandI'dratheryoudidnotpretendthatyoudotoo.'

Ùm...anEvenBiggerThing?'saidRunes,awarethathewasedgingintounknownterritory.

`No,sir,'saidPonder,kindly.`ThenextoneupwouldbeaGreatBigThing,Sir.It'sbeenpostulatedthatifwecouldeverbuildaGBT,wewouldknowthemindoftheCreator.'

Thewizardsfelsilent.Foramoment,aflybuzzedagainstthehigh,stone-mulionedwindow,withitsstained-glassimageofArchchancelorSlomanDiscoveringtheSpecialTheoryofSlood,andthen,afterdepositingasmalflyspeckonArchchancelorSloman'snose,exitedwithprecisionthoughatinyholeinonepanewhich

hadbeencausedtwocenturiesagowhenastonehadbeenthrownupbyapassingcart.Originalytheholehadstayedtherebecausenoonecouldbebotheredtohaveitfixed,butnowitstayedtherebecauseitwastraditional.

TheflyhadbeenborninUnseenUniversityandbecauseofthehigh,permanentmagicalfield,wasfarmoreinteligentthantheaveragefly.

Strangely,thefieldneverhadthiseffectonwizards,perhapsbecausemostofthemweremoreinteligentthanfliesinanycase.

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Ìdon'tthinkwewanttodothat,dowe?'saidRidculy.

Ìtmightbeconsideredimpolite,'agreedtheChairofIndefiniteStudies.

ÈxactlyhowbigwouldaGreatBigThingbe?'saidtheSeniorWrangler.

`Thesamesizeastheuniverse,sir,'saidPonder.Èveryparticleoftheuniversewouldbemodeledwithinit,infact.'

`Quitebig,then...'

`Yes,Sir.'

Àndquitehardtofindroomfor,Ishouldimagine.'

Ùndoubtedly,sir,'saidPonder,whohadlongagogivenuptryingtoexplainBigMagictotherestoftheseniorfaculty.

`Verywel,then,'saidArchchancelorRidculy.`Thankyouforyourreport,MisterStibbons.'Hesniffed.`Soundsfascinatin'.Andthenextitem:AnyOtherBusiness.'Heglaredaroundthetable.Àndsincethereisnootherbusi-'

Èr...

Thiswasabadwordatthispoint.Ridculydidnotlikecommitteebusiness.

Hecertainlydidnotlikeanyotherbusiness.

`Wel,Rincewind?'hesaid,glaringdownthelengthofthetable.

Ùm...'saidRincewind.Ìthinkthat'sProfessorRincewind,Sir?'

`Verywel,professor,'saidRidculy.`Comeon,it'spasttimeforEarlyTea.'

`Theworld'sgonewrong,Archchancelor.'

Asonewizard,everyonelookedoutatwhatcouldbeseenoftheworldthroughArchchancelorSlomanDiscoveringtheSpecialTheoryofSlood.

`Don'tbeafool,man,'saidRidculy.`Thesun'sshining!It'saniceday!'

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`Notthisworld,sir,'saidRincewind.`Theotherone.'

`Whatotherone?'saidtheArchchancelor,andthenhisexpressionchanged.

`Not-'hebegan.

`Yes,sir,'saidRincewind.`Thatone.It'sgonewrong.Again.'

Everyorganisationneedssomeonetodothosejobsitdoesn'twanttodoorsecretlythinksdon'tneeddoing.Rincewindhadnineteenofthemnow,includingHealthandSafetyOfficer.[1]

ItwasasEgregiousProfessorofCruelandUnusualGeographythathewasresponsiblefortheGlobe.Thesedays,itwasonhisdeskoutinthegloomycelarpassagewhereheworked,worklargelyconsistingofwaitinguntilpeoplegavehimsomecruelandunusualgeographytoprofess.

`Firstquestion,'saidRidculy,asthefacultysweptalongthedankflagstones.`Whyareyouworkingouthere?What'swrongwithyouroffice?'

Ìt'stoohotinmyoffice,sir,'saidRincewind.`Youusedtocomplainitwastoocold!'

`Yes,Sir.Inthewinteritis.Icefreezesonthewals,sir.'`Wegiveyouplentyofcoal,don'twe?'

Àmple,Sir.Onebucketperdayperpostheld,aspertradition.That'sthetrouble,realy.Ican'tgettheporterstounderstand.Theywon'tgivemelesscoal,onlynocoalatal.Sotheonlywaytobesureofstayingwarminthewinteristokeepthefiregoingal

[1]TheN'tuitivtribeofHowondalandcreatedthepostofHealthandSafetyOfficerevenbeforethepostofWitchDoctor,andcertainlybeforetamingfireorinventingthespear.Theyhuntbywaitingforanimalstodropdead,andeatthemraw.

summer,whichmeansit'ssohotintherethatIcan'tworkin-don'topenthedoor,sir!'

Ridculy,who'djustopenedtheofficedoor,slammeditagain,andwipedhisface

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withahandkerchief.

`Snug,'hesaid,blinkingthesweatoutofhiseyes.Thenheturnedtothelittleglobeonthedeskbehindhim.

Itwasaboutafootacross,atleastontheoutside.Inside,itwasinfinite;mostwizardshavenoproblemwithfactsofthissort.Itcontainedeverythingtherewas,foragivenvalueof`containedeverythingtherewas',butinitsdefaultstateitfocusedononetinypartofeverythingtherewas,asmalplanetwhichwas,currently,coveredinice.

PonderStibbonsswiveledtheomniscopethatwasattachedtothebaseoftheglassdome,andstareddownatthelittlefrozenworld.Justdebrisattheequator,'hereported.`Theyneverbuiltthebigskyhookthingthatalowedthemtoleave.[1]Theremusthavebeensomethingwemissed.'

`No,wesorteditalout,'saidRidculy.`Remember?Althepeopledidgetawaybeforetheplanetfroze.'

`Yes,Archchancelor,'saidStibbons.Ànd,thenagain,no.'

ÌfIaskyoutoexplainthat,wouldyoutelmeinwordsIcanunderstand?'

saidRidculy.

Ponderstaredatthewalforamoment.Hislipsmovedashetriedoutsentences.`Yes,'hesaidatlast.`Wechangedthehistoryoftheworld,sendingittowardsafuturewherethepeoplecouldescapebeforeitfroze.

Itappearsthatsomethinghashappenedtochangeitbacksincethen.'

Àgain?Elvesdiditlasttime!'[2]

'Idoubtifthey'vetriedagain,sir.'

`Butweknowthepeopleleftbeforetheice,'saidtheLecturerin[1]SeeTheScienceofDiscworld(EburyPress,1999,revd2000).

[2]SeeTheScienceofDiscworldI(EburyPress,RecentRunes.Helookedfromfacetoface,andaddeduncertainly,`Don'twe?'

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`Wethoughtweknewbefore,'saidtheDean,gloomily.

Ìnaway,sir,'saidPonder.`ButtheRoundworlduniverseissomewhat...

softandmutable.Eventhoughwecanseeafuturehappen,thepastcanchangesothatfromthepointofviewofRoundworldersitdoesn't.It'slike...

takingoutthelastpageofabookandputtinganewonein.Youcanstilreadtheoldpage,butfromthepointofviewofthecharacters,theendinghaschanged,or...possiblynot.'

Ridculyslappedhimontheback.`Weldone,MrStibbons!Youdidn'tmentionquantumevenonce!'hesaid.

`Nevertheless,Isuspectitmaybeinvolved,'sighedPonder.

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TWO

PALEY'SWATCH

THESCENE:ARADIOCHAT-SHOWintheBibleBeltoftheUnitedStates,afewyearsago.Thehostisrunningaphone-inaboutevolution,aconceptthatisanathematoeveryGod-fearingsouthernfundamentalist.

Theconversationrunssomethinglikethis:HOST:So,Jerry,whatdoyouthinkaboutevolution?ShouldwetakeanynoticeofDarwin'stheories?

JERRY:ThatDarwinguynevergotaNobelPrize,didhe?Ifhe'ssogreat,howcomehedon'tgetnoNobel?

HOST:Ithinkyouhaveaverygoodpointthere,Jerry.

Suchaconversationdidoccur,andthehostwasnotbeingironic.ButJerry'spointisnotquitetheknock-downargumenthethoughtitwas.

CharlesRobertDarwindiedin1882.ThefirstNobelPrizewasawardedin1901.

Ofcourse,wel-meaningpeopleareoftenignorantaboutfinepointsofhistoricaldetail,anditisunfairtoholdthatagainstthem.Butitisperfectlyfairtoholdsomethingelseagainstthem:thehostandhisguestdidn'thavetheirbrainsingear.Afteral,whyweretheyhavingthatdiscussion?

Because,aseveryGod-fearingsouthernfundamentalistknows,virtualyeveryscientistviewsDarwinasoneoftheal-timegreats.Itwasthisassertion,infact,thatJerrywasattemptingtoshootdown.Now,itshouldbeprettyobviousthatwinnersofNobelprizes(forscience)areselectedbyaprocessthatreliesheavilyonadvicefromscientists.Andthose,wealreadyknow,areoverwhelminglyoftheopinionthatDarwinwassomewherenearthetopofthescientifictree.SoifDarwindidn'tgetaNobel,itcouldn'thavebeen(aslistenerswereintendedtoinfer)becausethecommitteedidn'tthinkmuchofhiswork.Therehadtobeanotherreason.Asithappens,themainreasonwasthatDarwinwasdead.

Asthisstoryshows,evolutionisstilahotissueintheBibleBelt,whereitissometimesknownas'evilution'andgeneralyviewedastheworkoftheDevil.

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Moresophisticatedreligiousbelievers-especialyEuropeanones,amongthemthePope-workedoutlongagothatevolutionposesnothreattoreligion:itissimplyhowGodgetsthingsdone,inthiscase,themanufactureoflivingcreatures.ButtheBible-Belters,intheirunsophisticatedfundamentalistmanner,recogniseathreat,andthey'reright.ThesophisticatedreconciliationofevolutionwithGodisawishy-washycompromise,acop-out.Why?BecauseevolutionknocksanenormousholeinwhatotherwisemightbethebestargumentyetdevisedforconvincingpeopleoftheexistenceofGod,andthatistheàrgumentfromdesign'.[1]

Theuniverseisawesomeinitssize,astonishinginitsintricacy.Everypartofitfitsneatlywitheveryotherpart.Consideranant,ananteater,anantirrhinum.Eachisperfectlysuitedtoitsrole(or'purpose').Theantexiststobeeatenbyanteaters,theanteaterexiststoeatants,andtheantirrhinum...wel,beeslikeit,andthat'sagoodthing.Eachorganismshowsclearevidenceof`design',asifithadbeenmadespecificalytocarryoutsomepurpose.Antsarejusttherightsizeforanteaters'tonguestolickup,anteatershavelongtonguestogetintoants'nests.Antirrhinumsareexactlytheshapeto

[1]Socaledbecauseitstartsfromthephenomenonofdesignanddeducestheexistenceofacosmicdesigner.

bepolinatedbyvisitingbees.Andifweobservedesign,thensurelyadesignercan'tbefaraway.

Manypeoplefindthisargumentcompeling,especialywhenitisdevelopedatlengthandindetail,and`designer'isgivenacapital`D'.ButDarwin's`dangerousidea',asDanielDennettcharacteriseditinhisbookwiththattitle,putsaverybigspokeintothewheelofcosmicdesign.Itprovidesanalternative,veryplausible,andapparentlysimpleprocess,inwhichthereisnorolefordesignandnoneedforadesigner.Darwincaledthatprocess`naturalselection';nowadayswecalitèvolution'.

Therearemanyaspectsofevolutionthatscientistsdon'tyetunderstand.

ThedetailsbehindDarwin'stheoryarestilupforgrabs,andeveryyearbringsnewshiftsofopinionasscientiststrytoimprovetheirunderstanding.Bible-Beltersunderstandevenlessaboutevolution,andtheytypicalydistortitintoacaricature:`blindchance'.Theyhavenointerestwhatsoeverinimprovingtheir

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understanding.Buttheydounderstand,farbetterthaneffeteEuropeans,thatthetheoryofevolutionconstitutesaverydangerousattackonthepsychologyofreligiousbelief.

Notonitssubstance(becauseanythingthatsciencediscoverscanbeattributedtotheDeityandviewedasHismechanismforbringingtheassociatedeventsabout)butonitsattitude.OnceGodisremovedfromtheday-to-dayrunningoftheplanet,andinstaledsomewherebehindDNAbiochemistryandtheSecondLawofThermodynamics,itisnolongersoobviousthatHemustbefundamentaltopeople'sdailylives.Inparticular,thereisnospecialreasontobelievethatHeaffectsthoselivesinanyway,orwouldwishto,sothefundamentalistpreacherscouldwelbeoutofajob.WhichishowDarwin'slackofaNobelcanbecomeadebatingpointonAmericanlocalradio.ItisalsothegenerallinealongwhichDarwin'sownthinkingevolved-hebeganhisadultlifeasatheologystudentandendeditasasomewhattormentedagnostic.

Seenfromoutside,andevenmoresofromwithin,theprocessofscientificresearchisdisorderlyandconfusing.Itistemptingtodeducethatscientiststhemselvesaredisorderlyandconfused.Inaway,theyare-

that'swhatresearchinvolves.Ifyouknewwhatyouweredoingitwouldn'tberesearch.Butthat'sjustanapology,andtherearebetterreasonsforexpecting,indeed,forvaluing,thatkindofconfusion.Thebestreasonisthatit'sanextremelyeffectivewayofunderstandingtheworld,andhavingafairdegreeofconfidenceinthatunderstanding.

InherbookDefendingScience-ReasonthephilosopherSusanHaackiluminatesthemessinessofsciencewithasimplemetaphor,thecrosswordpuzzle.Enthusiastsknowthatsolvingacrosswordpuzzleisamessybusiness.Youdon'tsolvethecluesinnumericalorderandwritethemintheirproperplace,converginginanorderlymannertoacorrect-

solution,unless,perhaps,it'saquickcrosswordandyou'reanexpert.

Instead,youattackthecluesratherrandomly,guidedonlybyavaguefeelingofwhichoneslookeasiesttosolve(somepeoplefindanagramseasy,othershatethem).Youcross-checkproposedanswersagainstothers,tomakesureeverythingfits.Youdetectmistakes,rubthemout,writeincorrections.

Itmaynotsoundlikearationalprocess,buttheendresultisentirelyrational,

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andthechecksandbalances-dotheanswersfittheclues,dothelettersalfittogether?-arestringent.Afewmistakesmaystilsurvive,wherealternativewordsfitboththeclueandthewordsthatintersectthem,butsucherrorsarerare(andarguablyaren'trealyerrors,justambiguityonthepartofthecompiler).

Theprocessofscientificresearch,saysHaack,isratherlikesolvingacrosswordpuzzle.Solutionstonature'sriddlesarriveerraticalyandpiecemeal.Whentheyarecross-checkedagainstothersolutionstootherriddles,sometimestheanswersdon'tfit,andthensomethinghastobechanged.Theoriesthatwereoncethoughttobecorrectturnouttobenonsenseandarethrownout.Afewyearsago,thebestexplanationoftheoriginofstarshadonesmalflaw:itimpliedthatthestarswereolderthantheuniversethatcontainedthem.Atanygiventime,someofscience'sanswersappeartobeverysolid,somelessso,somearedubious...andsomearemissingentirely.

Again,itdoesn'tsoundlikearationalprocess,butitleadstoarationalresult.Indeed,althatcross-checking,backtracking,andrevisionincreasesourconfidenceintheresult.Remembering,always,thatnothingisprovedtothehilt,nothingisfinal.

Criticsoftenusethisconfusedandconfusingprocessofdiscoveryasareasontodiscreditscience.Thosestupidscientistscan'tevenagreeamongthemselves,theykeepchangingtheirminds,everythingtheysayisprovisional-whyshouldanyoneelsebelievesuchamuddle?Theytherebymisrepresentoneofscience'sgreateststrengthsbyportrayingitasaweakness.Arationalthinkermustalwaysbepreparedtochangehisorhermindiftheevidencerequiresit.Inscience,thereisnoplacefordogma.Ofcourse,manyindividualscientistsfalshortofthisideal;theyareonlyhuman.Entireschoolsofscientificthoughtcangettrappedinanintelectualblindaleyandgointodenial.Onthewhole,though,theerrorsareeventualyexposed-byotherscientists.

Scienceisnottheonlyareaofhumanthoughttodevelopinthisflexibleway.Thehumanitiesdosimilarthings,intheirownmanner.Butscienceimposesthiskindofdisciplineuponitselfmorestrongly,moresystematicaly,andmoreeffectively,thanvirtualyanyotherstyleofthinking.

Anditusesexperimentsasarealitycheck.

Religions,cults,andpseudoscientificmovementsdonotbehavelikethat.Itis

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extremelyrareforreligiousleaderstochangetheirmindsaboutanythingthatisalreadyintheirHolyBook.Ifyourbeliefsareheldtoberevealedtruth,directfromthemouthofGod,it'strickytoadmittoerrors.AlthemorecredittotheCatholics,then,foradmittingthatinGalileo'sdaytheygotitwrongabouttheEarthbeingthecentreoftheuniverse,anduntilrecentlytheygotitwrongaboutevolution.

Religions,cultsandpseudoscientificmovementshaveadifferentagendafromscience.Science,atitsbest,keepslinesofenquiryopen.Itisalwaysseekingnewwaystotestoldtheories,evenwhentheyseemwelestablished.Itdoesn'tjustlookatthegeologyoftheGrandCanyonandsettleonthebeliefthattheEarthishundredsofmilionsofyearsold,orolder.Itcross-checksbytakingnewdiscoveriesintoaccount.Afterradioactivitywasdiscovered,itbecamepossibletoobtainmoreaccuratedatesforgeologicalevents,andtocomparethosewiththeapparentrecordofsedimentationintherocks.Manydateswerethenrevised.Whencontinentaldriftcameinfromleftfield,entirelynewwaystofindthosedatesarrived,andwerequicklyused.Moredateswererevised.

Scientists-colectively-wanttofindtheirmistakes,sothattheycangetridofthem.

Religions,cults,andpseudoscientificmovementswanttoclosedownlinesofenquiry.Theywanttheirfolowerstostopaskingquestionsandacceptthebeliefsystem.Thedifferenceisglaring.Suppose,forinstance,thatscientistsbecameconvincedthattherewassomethingworthtakingseriouslyinthetheoriesofErichvonDaniken,thatancientruinsandstructuresmusthavebeentheworkofvisitingaliens.Theywouldthenstartaskingquestions.Wheredidthealienscomefrom?Whatsortofspaceshipsdidtheyhave?Whydidtheycomehere?Doancientinscriptionssuggestonekindofalienormany?Whatisthepatterntothevisitations?WhereasbelieversinvonDaniken'stheoriesaresatisfiedwithgenericaliens,andasknomore.Aliensexplaintheruinsandstructures-

that'scrackedit,problemsolved.

Similarly,toearlyproponentsofdivinedesignandtheirmodernreincarnationscreationismandìnteligentdesign',thelatestquasireligiousfad,onceweknowthatlivingcreatureswerecreated(eitherbyGod,analien,oranunspecifiedinteligentdesigner)thentheproblemissolvedandweneedlooknofurther.Wearenotencouragedtolookforevidencethatmightdisproveourbeliefs.Justthings

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thatconfirmthem.Acceptwhatwetelyou,don'taskquestions.

Ah,yes,butsciencediscouragesquestionstoo,saythecultsandreligions.Youdon'ttakeourviewsseriously,youdon'talowthatsortofquestion.Youtrytostopusputtingourideasintoschoolsciencelessonsasalternativestoyourworldview.

Tosomeextent,that'strue-especialythebitaboutsciencelessons.Buttheyaresciencelessons,sotheyshouldbeteachingscience.Whereastheclaimsofthecultsandthecreationists,andtheclosettheistswhoespouseinteligentdesign,arenotscience.Creationismissimplyatheisticbeliefsystemandoffersnocrediblescientificevidencewhatsoeverforitsbeliefs.Evidenceforalienvisitationsisweak,incoherent,andmostofitisreadilyexplainedbyentirelyordinaryaspectsofancienthumanculture.Inteligentdesignclaimsevidenceforitsviews,butthoseclaimsfalapartunderevencasualscientificscrutiny,asdocumentedinthe2004

booksWhyInteligentDesignFails,editedbyMattYoungandTanerEdis,andDebatingDesign,editedbyWiliamDembskiandMichaelRuse.Andwhenpeople(noneoftheabove,wehastentopointout)claimthattheGrandCanyonisevidenceforNoah'sflood-anotoriousrecentincident-

it'snotterriblyhardtoprovethemwrong.

Theprincipleoffreespeechimpliesthattheseviewsshouldnotbesuppressed,butitdoesnotimplythattheyshouldbeimportedintosciencelessons,anymorethanscientificalternativestoGodshouldbeimportedintothevicar'sSundaysermon.Ifyouwanttogetyourworldviewintothesciencelesson,you'vegottoestablishitsscientificcredentials.Butbecausecults,religionsandalternativebeliefsystemsstoppeopleaskingawkwardquestions,there'snowaytheycanevergetthatkindofevidence.

It'snotonlychancethatisblind.

Thescientificvisionoftheplanetthatiscurrentlyouronlyhome,andofthecreatureswithwhichweshareitandtheuniversearoundit,hasattaineditspresentformoverthousandsofyears.Thedevelopmentofscienceismostlyanincrementalprocess,alakeofunderstandingfiledbytheconstantaccumulationofinnumerabletinyraindrops.Likethewaterinalake,thepoolofunderstandingcanalsoevaporateagain-forwhatwethinkweunderstandtoday

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canbeexposedasnonsensetomorrow,justaswhatwethoughtweunderstoodyesterdayisexposedasnonsensetoday.

Weusethewordùnderstanding'ratherthan,`knowledge'becausescienceisbothmorethan,andlessthanacolectionofimmutablefacts.Itismore,inthatitencompassesorganisingprinciplesthatexplainwhatweliketothinkofasfacts:thestrangepathsoftheplanetsintheskymakeperfectsenseonceyouunderstandthatplanetsaremovedbygravitationalforces,andthattheseforcesobeymathematicalrules.Itisless,becausewhatmaylooklikeafacttodaymayturnouttomorrowtohavebeenamisinterpretationofsomethingelse.OnDiscworld,whereobviousthingstendtobetrue,atinyandinsignificantSundoesindeedrevolveroundthegrand,importantworldofpeople.Weusedtothinkourworldwaslikethattoo:forcenturies,itwasàfact',andanobviousone,thattheSunrevolvedroundtheEarth.

Thebigorganisingprinciplesofsciencearetheories,coherentsystemsofthoughtthatexplainhugenumbersofotherwiseisolatedfacts,whichhavesurvivedstrenuoustestingdeliberatelydesignedtobreakthemiftheydonotaccordwithreality.Theyhavenotbeenmerelyacceptedassomeactofscientificfaith:instead,peoplehavetriedtofalsifythem-toprovethemwrong-buthavesofarfailed.Thesefailuresdonotprovethatthetheoryistrue,becausetherearealwaysnewsourcesofpotentialdiscord.IsaacNewton'stheoryofgravitation,inconjunctionwithhislawsofmotion,was-

andstilis-goodenoughtoexplainthemovementsoftheplanets,asteroidsandotherbodiesofthesolarsysteminintricatedetail,withhighaccuracy.Butinsomecontexts,suchasblackholes,ithasnowbeenreplacedbyAlbertEinstein'stheoryofgeneralrelativity.

Waitafewdecades,andsomethingelsewilsurelyreplacethat.Thereareplentyofsignsthatalisnotwelatthefrontiersofphysics.

Whencosmologistshavetopostulatebizarrèdarkmatter'toexplainwhygalaxiesdon'tobeytheknownlawsofgravity,andthenthrowinevenweirder`darkenergy'toexplainwhygalaxiesaremovingapartatanincreasingrate,andwhentheindependentevidenceforthesetwopowersofdarknessisprettymuchnon-existent,youcansmelthecomingparadigmshift.

Mostscienceisincremental,butsomeismoreradical.Newton'stheorywasone

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ofthegreatbreakthroughsofscience-notashowerofraindisturbingthesurfaceofthelake,butanintelectualstormthatunleashedaragingtorrent.Darwin'sWatchisaboutanotherintelectualstorm:thetheoryofevolution.DarwindidforbiologywhatNewtonhaddoneforphysics,butinaverydifferentway.Newtondevelopedmathematicalequationsthatletphysicistscalculatenumbersandtestthemtomanydecimalplaces;itwasaquantitativetheory.Darwin'sideaisexpressedinwords,notequations,anditdescribesaqualitativeprocess,notnumbers.

Despitethat,itsinfluencehasbeenatleastasgreatasNewton's,possiblyevengreater.Darwin'storrentstilragestoday.

Evolution,then,isatheory,oneofthemostinfluential,farreachingandimportanttheorieseverdevised.Inthiscontext,it'sworthpointingoutthattheword`theory'isoftenusedinaquitedifferentsense,tomeananideathatisproposedinordertobetested.Strictlyspeaking,thewordthatshouldbeusedhereis`hypothesis',butthat'ssuchafussy,pedantic-soundingwordthatpeopletendtoavoidit.Evenscientists,whoshouldknowbetter.Ìhaveatheory,'theysay.No,youhaveahypothesis.Itwiltakeyears,possiblycenturies,ofstringenttests,toturnitintoatheory.

Thetheoryofevolutionwasonceahypothesis.Nowitisatheory.

Detractorsseizeonthewordandforgetitsdualuse.Ònlyatheory,'theysaydismissively.Butatruetheorycannotbesoeasilydismissed,becauseithassurvivedsomuchrigoroustesting.Inthisrespectthereisfarmorereasontotakethetheoryofevolutionseriouslythananyexplanationoflifethatdependson,say,religiousfaith,becausefalsificationisnothighonthereligiousagenda.Theories,inthatsense,arethebestestablished,mostcrediblepartsofscience.Theyare,byandlarge,considerablymorecrediblethanmostotherproductsofthehumanmind.Sowhatthesepeoplearethinkingofwhentheychanttheirdismissivesloganshouldactualybeònlyahypothesis'.

Thatwasadefensiblepositionintheearlydaysofthetheoryofevolution,buttodayitismerelyignorant.Ifanythingcanbeafact,evolutionis.Itmayhavetobeinferredfromcluesdepositedintherocks,andmorerecentlybycomparingtheDNAcodesofdifferentcreatures,ratherthanbeingseendirectlywiththenakedeyeinrealtime,butyoudon'tneedaneyewitnessaccounttomakelogicaldeductionsfromevidence.Theevidence,fromseveralindependentsources

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(suchasfossilsandDNA),isoverwhelming.

Evolutionhasbeenestablishedsofirmlythatourplanetmakesnosenseatalwithoutit.Livingcreaturescan,anddo,changeovertime.Thefossilrecordshowsthattheyhavechangedsubstantialyoverlongperiodsoftime,totheextentthatentirelynewspecieshavearisen.Smalerchangescanbeobservedtoday,overperiodsasshortasayear,ormeredaysinbacteria.

Evolutionhappens.

Whatremainsopentodispute,especialyamongscientists,ishowevolutionhappens.Scientifictheoriesthemselvesevolve,adaptingtofitnewobservations,newdiscoveries,andnewinterpretationsofolddiscoveries.Theoriesarenotcarvedintabletsofstone.Thegreateststrengthofscienceisthatwhenfacedwithsufficientevidence,scientistschangetheirminds.Notalofthem,forscientistsarehumanandhavethesamefailingsastherestofus,butenoughofthemtoalowsciencetoimprove.

Eventodaytherearediehards-notamajority,despitethenoisetheymake,butasignificantminority-whodenythatevolutionhaseveroccurred.MostofthemareAmerican,becauseaquirkofhistory(coupledwithsomeidiosyncratictaxlaws)hasmadeevolutionintoamajoreducationalissueintheUnitedStates.There,thebattlebetweenDarwin'sfolowersandhisopponentsisnotjustabouttheintelectualhighground.Itisaboutdolarsandcents,anditisaboutwhoinfluencestheheartsandmindsofthenextgeneration.Thestrugglemasqueradesasareligiousandscientificone,butitsessenceispolitical.Inthe1920sfourAmericanstates(Arkansas,Mississippi,Oklahoma,andTennessee)madeitilegaltoteachchildrenaboutevolutioninpublicschools.Thislawremainedinplacefornearlyhalfacentury:itwasfinalybannedbytheSupremeCourtin1968.Thishasnotstoppedadvocatesof`creationscience'fromtryingtofindwaysroundthatdecision,oreventogetitreversed.Largely,however,theyhavefailed,andonereasonisthatcreation`science'isnotscience;itlacksintelectualrigour,itfailsobjectivetests,andattimesitisplainnutty.

ItispossibletomaintainthatGodcreatedtheEarth,andnoonecanproveyouwrong.Inthatsense,itisadefensiblethingtobelieve.Scientistsmayfeelthatthisèxplanation'doesn'tgreatlyhelpusunderstandanything,butthat'stheirproblem;foralanyonecanprove,itcouldhavehappenedthatway.ButitisnotsensibletofolowtheAnglo-IrishprelateJamesUssher'sbiblicalchronologyand

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maintainthattheactofcreationhappenedin4004

BC,becausethereisoverwhelmingevidencethatourplanetisfarolderthanthat-4.5bilionyearsratherthan6000.EitherGodisdeliberatelytryingtomisleadus(whichisconceivable,butdoesnotfitwelwiththeusualreligiousmessages,andmaywelbeheretical)orwearestandingonaveryoldlumpofrock.Alegedly,50percentofAmericansbelievethattheEarthwascreatedlessthan10,000yearsago,whichiftruesayssomethingrathersadaboutthemostexpensiveeducationsystemintheworld.

Americaisfighting,aloveragain,abattlethatwasfoughttoafmishinEuropeacenturyago.TheEuropeanoutcomewasacompromise:PopePiusXIdidacceptthetruthofevolutioninanencyclicalof1950,butthatwasn'tatotalvictoryforscience.[1]In1981asuccessor,JohnPaulI,gentlypointedoutthat`TheBible...doesnotwishtoteachhowtheheavensweremade,buthowonegoestoheaven.'Sciencewasvindicated,inthatthetheoryofevolutionwasgeneralyaccepted,butreligiouspeoplewerefreetointerpretthatprocessasGod'swayofmakinglivingcreatures.Andit'saverygoodway,asDarwinrealised,soeveryonecanbehappyandstoparguing.Creationists,incontrast,seemnottohaveappreciatedthatiftheypintheirreligiousbeliefstoa6000-year-oldplanet,theyaredoingthemselvesnofavoursandleavingthemselvesnorealwayout.

Darwin'sWatchisaboutaVictoriansocietythatneverhappened-wel,oncethewizardsinterfered,itstoppedhavinghappened.Itisnotthesocietythatcreationistsarestilattemptingtoarrange,whichwouldbefarmorèfundamentalist',fulofself-righteouspeopletelingeveryoneelsewhattodoandstiflinganytruecreativity.TherealVictorianerawasaparadox:asocietywithaverystrongbutratherflexiblereligiousbase,whereitwastakenforgrantedthatGodexisted,butwhichgavebirthtoawholeseriesofmajorintelectualrevolutionsthatled,fairlydirectly,totoday'ssecularWesternsociety.LetusnotforgetthatevenintheUSAthereisaconstitutionalseparationofthestatefromtheChurch.(Strangely,theUnitedKingdom,whichinpracticeisoneofthemostsecularcountriesintheworld-hardlyanyoneattendschurch,exceptforchristenings,weddings,andfunerals-hasitsownstatereligion,andamonarchwhoclaimstobeappointedbyGod.UnlikeDiscworld,Roundworlddoesn'thavetomakesense.)Atanyrate,therealVictorianswereaGod-fearingrace,buttheirsocietyencouragedmaverickslikeDarwintothinkoutsidetheloop,withfarreachingconsequences.

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[1]AccordingtoIsaacAsimov,themostpracticalanddramaticvictoryofscienceoverreligionoccurredintheseventeenthcentury,whenchurchesbegantoputuplightningconductors.

Thethreadofclocksandwatchesrunsrightacrossthemetaphoricallandscapeofscience.Newton'svisionofasolarsystemrunningaccordingtoprecisemathematical`laws'isoftenreferredtoasàclockworkuniverse'.It'snotabadimage,andtheorrery-amodelsolarsystem,whosecogwheelsmakethetinyplanetsrevolveinsomesemblanceofreality-doeslookratherlikeapieceofclockwork.Clockswereamongthemostcomplicatedmachinesoftheseventeenthandeighteenthcenturies,andtheywereprobablythemostreliable.Eventoday,wesaythatsomethingfunctions`likeclockwork';wehaveyettoamendthistoàtomicaccuracy'.

BytheVictorianage,theepitomeofreliablegadgetryhadbecomethepocket-watch.Darwin'sideasareintimatelyboundupwithawatch,whichagainplaysthemetaphoricalroleofintricatemechanicalperfection.ThewatchinquestionwasintroducedbytheclergymanWiliamPaley,whodiedthreeyearsafterDarwinwasborn.ItfeaturesintheopeningparagraphofPaley'sgreatworkNaturalTheology,firstpublishedin1802.[1]Thebestwaytogainafeelingforhislineofthinkingistousehisownwords:

Incrossingaheath,supposeIpitchedmyfootagainstastone,andwereaskedhowthestonecametobethere;Imightpossiblyanswer,thatforanythingIknewtothecontrary,ithadlainthereforever:norwoulditperhapsbeveryeasytoshowtheabsurdityofthisanswer.ButsupposeIhadfoundawatchupontheground,anditshouldbeinquiredhowthewatchhappenedtobeinthatplace;IshouldhardlythinkoftheanswerwhichIhadbeforegiven,that,foranythingIknew,thewatchmighthavealwaysbeenthere.Yetwhyshouldnotthisanswerserveforthewatchaswelasforthestone?Whyisitnotasadmissibleinthesecondcase,asinthefirst?Forthisreason,andfornoother,viz.that,whenwecometoinspectthewatch,we

[1]Itisoldenoughtousetheelongateds'sparodiedinDiscworldasis.

Wehaveresistedtemptationexceptinthisfootnote.Though'manifestationofdesign'doeshaveabitofacachet.

perceive(whatwecouldnotdiscoverinthestone)thatitsseveralpartsare

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framedandputtogetherforapurpose,e.g.thattheyaresoformedandadjustedastoproducemotion,andthatmotionsoregulatedastopointtothehouroftheday;thatifthedifferentpartshadbeendifferentlyshapedfromwhattheyare,ofadifferentsizefromwhattheyare,orplacedafteranyothermanner,orinanyotherorder,thanthatinwhichtheyareplaced,eithernomotionatalcouldhavebeencarriedoninthemachine,ornonewhichwouldhaveansweredtheusethatisnowservedbyit.

Paleygoesontoelaboratethecomponentsofawatch,leadingtothecruxofhisargument:

Thismechanismbeingobserved...theinference,wethink,isinevitable;thatthewatchmusthavehadamaker;thattheremusthaveexisted,atsometime,andatsomeplaceorother,anartificerorartificers,whoformeditforthepurposewhichwefinditactualytoanswer;whocomprehendeditsconstruction,anddesigneditsuse.

Therethenfolowsalongseriesofnumberedparagraphs,inwhichPaleyqualifieshisargumentmorecarefuly,extendsittocaseswhere,forinstance,somepartsofthewatcharemissing,anddismissesseveralobjectionstohisreasoning.Thesecondchaptertakesupthestorybydescribingahypothetical`watch'thatcanproducecopiesofitself-aremarkableanticipationofthetwentieth-centuryconceptofaVonNeumannmachine.Therewouldstilbegoodreason,Paleystates,toinfertheexistenceofa'contriver';infact,ifanything,theeffectwouldbetoenhanceone'sadmirationforthecontriver'sskil.Moreover,theinteligentobserverwouldreflect,thatthoughthewatchbeforehimwere,insomesense,themakerofthewatchwhichwasfabricatedinthecourseofitsmovements,yetitwasinaverydifferentsensefromthatinwhichacarpenter,forinstance,isthemakerofachair.

Hecontinuestodevelopthisthought,anddisposesofonepossiblesuggestion:that,justasastonemightalwayshaveexisted,foralheknew,soawatchmighthavealwaysexisted.Thatis,theremighthavebeenachainofwatches,eachmadebyitspredecessor,goingbackinfinitelyfarintothepast,sothatthereneverwasanyfirstwatch.However,hetelsus,awatchisverydifferentfromastone:itiscontrived.Perhapsstonescouldalwayshaveexisted:whoknows?Butnotwatches.Otherwisewewouldhavècontrivance,butnocontriver;proofsofdesign,butnodesigner'.

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Rejectingthissuggestiononvariousmetaphysicalgrounds,Paleystates:Theconclusionwhichthefirstexaminationofthewatch,ofitsworks,construction,andmovement,suggested,was,thatitmusthavehad,forthecauseandauthorofthatconstruction,anartificer,whounderstooditsmechanism,anddesigneditsuse.Thisconclusionisinvincible.Asecondexaminationpresentsuswithanewdiscovery.Thewatchisfound,inthecourseofitsmovement,toproduceanotherwatch,similartoitself:andnotonlyso,butweperceiveinitasystemororganisation,separatelycalculatedforthatpurpose.Whateffectwouldthisdiscoveryhave,oroughtittohave,uponourformerinference?What,ashathalreadybeensaid,buttoincrease,beyondmeasure,ouradmirationoftheskilwhichhadbeenemployedintheformationofsuchamachine!

Wel,wecanalseewherethegoodreverendisleading,andhehomesinonhistargetinhisthirdchapter.Insteadofawatch,consideraneye.Notlyingonaheath,butinananimal,whichperhapsdoeslieonaheath.Whathedoessayis:comparetheeyetoatelescope.Therearesomanysimilaritiesthatweareforcedtodeducethattheeyewas`madeforvision',justasthetelescopewas.Some

thirtypagesofanatomicaldescriptionreinforcethecontentionthattheeyemusthavebeendesignedforthepurposeofseeing.Andtheeyeisjustoneexample:considerabird,afish,asilkworm,oraspider.Now,finaly,Paleystatesexplicitlywhatalhisreadersknewwascomingfrompageone:

Weretherenoexampleintheworldofcontrivanceexceptthatoftheeye,itwouldbealonesufficienttosupporttheconclusionwhichwedrawfromit,astothenecessityofaninteligentCreator.

Therewehaveit,inanutshel.Livingcreaturesaresointricate,andfunctionsoeffectively,andfittogethersoperfectly,thattheycanhavearisenonlybydesign.Butdesignimpliesadesigner.Ergo:Godexists,anditwasHewhocreatedEarth'smagnificentpanoplyoflife.Whatmoreistheretosay?Theproofiscomplete.

THREE

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THEOLOGYOFSPECIES

ITWASTHREEHOURSLATER...

TheseniorwizardstrodcarefulyintheHighEnergyMagicBuilding,partlybecauseitwasn'ttheirnaturalhabitat,butalsobecausemostofthestudents

whofrequenteditusedthefloorasafilingcabinetand,distressingly,asalarder.Pizzaisquitehardtoremovefromasole,especialythecheese.

Inthebackground-alwaysinthebackgroundintheHighEnergyMagicBuilding-wasHex,theuniversity'sthinkingengine.

Occasionaly,bitsofit,orpossibly`him',moved.PonderStibbonshadlongagogivenuptryingtounderstandhowHexworked.PossiblyHexwastheonlyentityintheuniversitywhounderstoodhowHexworked.

SomewhereinsideHexmagichappened.Spelswerereduced,nottotheircomponentcandlesandwandsandchants,buttowhattheymeant.Ithappenedtoofasttosee,andperhapstoofasttounderstand.AlthatPonderwascertainaboutwasthatlifewasintimatelyinvolved.WhenHexwasthinkingdeeplytherewasanoticeablehumfromthebeehivesalongthebackwal,whereslotsgavethemaccesstotheoutsideworld,andeverythingcompletelyceasedtoworkiftheantcolonywasremovedfromitsbigglassmazeintheheartofthemachine.

Ponderhadsetuphismagiclanternforapresentation.Helikedmakingpresentations.Forabriefmomentinthechaosoftheuniverse,apresentationmadeeverythingsoundasifitwasorganised.

`HexhasrunthehistoryofRoundworldagainstthelastcopy,'heannounced,asthelastwizardsatdown.'Hehasfoundsignificantchangesbeginninginwhatwasknownasthenineteenthcentury.Slide,please,Rincewind.'Therewassomemuffledgrumblingbehindthemagiclanternandapictureofaplumpandelderlyladyappearedonthescreen.`ThisladyisQueenVictoria,ruleroftheEmpireoftheBritish.'

`Whyissheupsidedown?'saidtheDean.

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Ìtcouldbebecausewithaglobethereistechnicalynorightwayup,'saidPonder.`ButI'mhazardingthatitgotputinwrong.Nextslide,please.Withcare.'Grumble,click.'Ah,yes,thisisasteamengine.ThereignofVictoriawasnotableforgreatdevelopmentsinscienceandengineering.Itwasaveryexcitingtime.Except...nextslide,please.'Grumble,click.

`Wrongslide,thatman!'saidRidculy.Ìt'sjustblank.'

'Aha,no,sir,'saidPonder,gleefuly.`ThatisadynamicwayofshowingyouthattheperiodIjustdescribedturnsoutnot,infact,tohavehappened.Itshouldhave,butitdidn't.OnthisversionoftheGlobe,theEmpireoftheBritishdidnotbecomeasbig,andtheotherdevelopmentswerealrathermuted.Thegreatwaveofdiscoveryflattenedout.Theworldsettleddowntoaperiodofstabilityandpeace.'

`Soundsgoodtome,'saidRidculy,andgotachorusof`hear,hears'fromtheotherwizards.

`Yes,Archchancelor,'saidPonder.Ànd,thenagain,no.Gettingofftheplanet,remember?Thebigfreezeinfivehundredyears'time?Nolandlifeformsurvivingthatwasbiggerthanacockroach?'

`Noonebotheredaboutthat?'saidRidculy.

`Notuntilitwastoolate,sir.Inthatworldasweleftit,thefirsthumanswalkedontheMoonlessthanseventyyearsaftertheyflewatal.'

Ponderlookedattheirblankfaces.

`Whichwasquiteanachievement,'hesaid.

`Why?We'vedonethat,'saidtheDean.

Pondersighed.`Thingsaredifferentonaglobe,sir.Therearenobroomsticks,nomagiccarpets,andgoingtotheMoonisnotjustacaseofpushingoffovertheedgeandtryingtoavoidtheTurtleonthewaydown.'

`Howdidtheydoit,then?'saidtheDean.

Ùsingrockets,sir.'

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`Thethingsthatgoupandexplodewithlotsofcolouredlights?'

Ìnitialy,sir,butfortunatelytheyfoundouthowtostopthemdoingthat.Nextslide,please...'Apicturethatmighthavebeenapairofold-fashionedpantaloonsappearedonthescreen.Àh,thisisouroldfriend,theTrousersofTime.Wealknowthis.It'swhatyougetwhenhistorygoestwoways.

Whatwehavetodonowisfindoutwhytheysplit.ThatmeansIshalhaveto-'

Àrewenearthepointwhereyoumentionquantum?'saidRidculy,quickly.

Ì'mafraiditislooming,sir,yes.'

Ridculystoodup,gatheringhisrobesabouthim.Àh.IthinkIheardthegongfordinner,gentlemen.Justaswel,realy.'

Themoonrose.Atmidnight,PonderStibbonsreadwhatHexhadwritten,wanderedacrossthedewylawntotheLibrary,woketheLibrarian,andaskedforacopyofabookcaledTheOriginofSpecies.

Twohourslaterhewentback,woketheLibrarianagain,andaskedforTheologyofSpecies.Asheleftwithit,heheardthedoorbeinglockedbehindhim.

Laterstil,hefelasleepwithhisfaceinacoldpizzaandbothbooksopenonhisdesk,drippingwithbookmarksandstraypiecesofanchovy.

Besidehim,Hex'swritingtablewhirred.Twentyquilpensflashedbackandforthandgyratedonspring-loadedarms,makingthetablelooklikeseveralgiantspidersontheirbacks.And,everyminute,apagedroppedontothepilethatwasformingonthefloor...

Ponderdreamedfitfulyofdinosaurstryingtofly.Theyalwayssplashedwhentheyreachedthebottomofthecliff.

Hewokeupathalfpasteight,readtheaccumulatedpapers,andvoidedasmalscream.

Alright,alright,hethought.Thereisnoactualhurry,assuch.Wecanchangeitbackanytimewelike.That'swhattimetravelmeans.

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Butalthoughthebraincanthinkthat,thepanicglandneverbelievesit.Hesnatchedupthebooksandasmanynotesashecouldcarryandhurriedout.

Wehaveheardthechimesofmidnight,thesayinggoes.Thewizardshadnotonlyheardthembutalsotheonesatone,twoandthreea.m.Theycertainlyweren'tinterestedinhearinganythingathalfpasteight,however.

TheonlyoccupantofthetablesintheGreatHalwasArchchancelorRidculy,wholikedanunhealthybreakfastafterhisearlymorningrun.Hewasaloneatthetrestletablesinthebighal.

Ì'vefoundit!'Ponderannounced,withacertainnervoustriumph,anddroppedthetwobooksinfrontoftheastonishedwizard.

`Foundwhat?'saidRidculy.Àndmindwhereyou'reputtingstuff,man!Younearlyhadthebacondishover!

'Ihaveputmyfinger,'Ponderdeclared,òntheprecisesplitintheTrousersofTime!'

`Goodman!'saidRidculy,reachingfortheflagonofbrownsauce.`Telmeaboutitafterbreakfast,wilyou?'

Ìt'sabook,sir!Twobooksinfact!Hewrotethewrongone!Look!'

Ridculysighed.Againsttheenthusiasmofwizardstherewasnodefence.

HenarrowedhiseyesandreadthetitleofthebookPonderStibbonswasholding:

`TheologyofSpecies.And?'

Àrchchancelor,itwaswrittenbyaCharlesDarwin,andcausedratherarowwhenitwaspublished,sinceitpurportedtoexplainthemechanismofevolutioninamannerwhichupsetsomewidelyheldbeliefs.Vestedinterestsrailedagainstit,butitprevailedandhadasignificanteffectonhistory.Er...thewrongone.'

`Why?Whatisitabout?'saidRidculy,carefulytakingthetopoffaboiledegg.

Ì'veonlyglancedatit,Archchancelor,butitappearstodescribetheprocessof

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evolutionasoneofpermanentinvolvementbyanomnipotentdeity.'

Ànd?'Ridculyselectedapieceoftoastandbegantocutitintosoldiers.

`That'snothowitworksonRoundworld,sir,'saidPonder,patiently.

`That'showitdoeshere,moreorless.There'sagodwhoseestoit.

`Yes,sir.But,asIamsureyouwilremember,'saidPonder,usingthewordsinthesenseofàsIknowyouhaveforgotten',`wehavenotfoundanytracesofDeitiumonRoundworld.'

`Wel,alright,'theArchchancelorconceded.`ButIdon'tseewhythemanshouldn'thavewrittenit,evenso.Goodsolidbook,bythelookofit.Tooksomethinkin'about,I'lbebound.'

`Yes,sir,'saidPonder.`Butthebookheshouldhavewritten...'hethumpedanothervolumeontothebreakfasttable,`...wasthis.'

Ridculypickeditup.Ithadamuchmorecolourfulcoverthan`Theology',andthetitle:

DarwinRevisited

THEORIGINOFSPECIES

byTheRev.RichardDawkins

`Sir,IthinkIcanprovethatbecauseDarwinwrotethewrongbooktheworldtookadifferentlegoftheTrousersofTime,andhumanitydidn'tleavetheplanetbeforethebigfreeze,'saidPonder,standingback.

`Whydidhedothat,then?'saidRidculy,mystified.

Ìdon'tknow,sir.AlIknowisthat,untilafewdaysago,thisCharlesDarwinwroteabookthatsaidthatevolutionalworkednaturaly,withoutagod.Nowitturnsoutthathedidn't.Instead,hewroteabookthatsaiditworkedbecauseagodwasinvolvedateverystage.'

Àndthisotherfela,Dawkins?'

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`HesaidDarwinhadprettymuchgotitrightexceptthegodpart.Youdidn'tneedone,hesaid.'

`Didn'tneedagod?Butitsaysherehe'sapriestofsomesort!'

Èr...sortof,sir.Inthe...historywhereCharlesDarwinwroteTheologyofSpecies,ithadbecomemoreorlesscompulsorytotakeholyordersinordertoattenduniversity.Dawkinssaidevolutionhappenedalbyitself.'

Heshuthiseyes.Ridculyalonewasamuchbetteraudiencethantheseniorfaculty,who'dtakencross-purposestothestatusofafineart,buthisArchchancelorwasapractical,sensiblemanandthereforefoundRoundworlddifficult.Itwasn'tasensibleplace.

`You'vefoxedmethere.Howcanitjusthappen?'saidRidculy.Ìtmakesnosenseifthereisn'tsomeonewhoknowswhat'sgoingon.There'sgottobeareason.'

`Quiteso,sir.ButthisisRoundworld,'saidPonder.`Remember?'Butsurelythisotherfeler,Dawkins,madeitalrightagain?'

Ridculyfloundered.`Youdidsayitwastherightbook.'

`Butatthewrongtime.Itwastoolate,sir.Hedidn'twritehisbookuntilmorethanahundredyearslater.Itcausedahugerow-'

Ànungodlyone,Isuspect?'saidRidculycheerfuly,dippingthetoastintheegg.

'Haha,sir,yes.Butitwasstiltoolate.Humanitywaswelontheroadtoextinction.'

RidculypickedupTheologyandturneditoverinhishands,gettingbutteronit.

`Seemsinnocentenough,'hesaid.`Godsmakingitalhappen...

wel,that'scommonsense.'Heheldupahand.Ìknow,Iknow!

ThisisRoundworld,Iknow.Butwherethere'ssomethingascomplicatedasawatch,youknowtheremustbeawatchmaker.'`That'swhattheDarwinwhowrotetheTheologybooksaid,sir,exceptthathestatedthatthewatchmaker

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remainedpartofthewatch,'saidPonder.

'Oilin'it,andsoforth?'saidRidculy,cheerfuly.`Sortof,sir.Metaphoricaly.'

`Hah!'saidRidculy.`Nowondertherewasarow.Priestsdon'tlikethatsortofthing.Theyalwayssquirmwhenthingsgetmystical.'Òh,thepriests?Theylovedit,'saidPonder.`What?Ithoughtyousaidvestedinterestswereagainstit!'

`Yes,Sir.Imeantthephilosophersandscientists,'saidPonderStibbons.

`Thetechnomancers.Buttheylost.'

FOUR

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PALEYONTOLOGY

PALEY'sMETAPHOROFTHEWATCH,aludedtobyRidculy,stilremainspowerful;powerfulenoughforRichardDawkinstotitlehisneo-Darwinianriposteof1986TheBlindWatchmaker.Dawkins[1]madeitclearthat

inhisview,andthoseofmostevolutionarybiologistsoverthepastfiftyyears,therewasnowatchmakerforlivingorganisms,inPaley'ssense:'Paley'sargumentismadewithpassionatesincerityandisinformedbythebestbiologicalscholarshipofhisday,butitiswrong,gloriouslyandutterlywrong.'But,saysDawkins,ifwemustgivethewatchmakerarole,thenthatrolemustbetheprocessofnaturalselectionthatDarwinexpounded.Ifso,thewatchmakerhasnosenseofpurpose:itisblind.It'saneattitlebuteasilymisunderstood,anditopensthewaytoreplies,suchastherecentbookbyWiliamDembski,HowBlindIstheWatchmaker?Dembskiisanadvocateofìnteligentdesign',amodernreincarnationofPaleywithupdatedbiologywhichrepeatstheoldmistakesinnewcontexts.[2]

[1]Thatistosay,theRichardDawkinsofourlegofthefamousTrousersofTime,whois,inaverydefiniteway,notinholyorders.

[2]Fordetailedandthoughtfulrebuttalsofthemaincontentionsoftheinteligentdesigners,plussomeresponses,seeMattYoungandTanerEdis,WhyInteligentDesignFails(RutgersUniversityPress,2004),andWiliamDembskiandMichaelRuse,DebatingDesign(CambridgeUniversityPress,2004).Andit'sonlyamatteroftimebeforesomeonewritesHowInteligentIstheDesigner?

Ifyoudidfindawatchonaheath,yourfirstthoughtwouldprobablynotbethattheremusthavebeenawatchmaker,butawatch-owner.Youwouldeitherwishtogettheowner'spropertybacktothem,orlookguiltilyaroundtomakesuretheyweren'tanywherenearbybeforeyousnaffledit.Paleytelsusthatifwefind,say,aspideronthepath,thenwearecompeledtoinfertheexistenceofaspider-maker.Buthefindsnosuchcompulsiontoinfertheexistenceofaspider-owner.Whyisonehumansocialroleemphasised,buttheothersuppressed?

Moreover,weknowwhatawatchisfor,andthiscoloursourthinking.

Suppose,instead,thatournineteenth-centuryheath-walkerchancedupona

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mobilephone,lefttherebysomecarelesstimetravelerfromthefuture.

Hewouldprobablystilinfer`design'fromitsintricateform...butpurpose?

Whatconceivablepurposewouldamobilephonehaveinthenineteenthcentury,withnosupportingnetworkoftransmissiontowers?Thereisnowaytolookatamobilephoneandinfersomeevidentpurpose.Ifitsbatteryhasrundown,itdoesn'tdoanything.Andifwhatwasfoundonthepathwasacomputerchip-say,theenginemanagerofacar-theneventheelementofdesignwouldbeundetectable,andthechipmightwelbedismissedassomeobscurecrystalinerock.Chemical'analysiswouldconfirmthediagnosisbyshowingthatitwasmostlysilicon.Ofcourse,weknowthatthesethingsdohaveadesigner;butintheabsenceofanyclearpurpose,Paley'sheath-walkerwouldnotbeentitledtomakeanysuchinference.

Inshort,Paley'slogicisheavilybiasedbywhatahumanbeingwouldknowaboutawatchanditsmaker.Andhisanalogybreaksdownwhenweconsiderotherfeaturesofwatches.Ifitdoesn'tevenworkforwatches,whichwedounderstand,there'snoreasonforittoapplytoorganisms,whichwedon't.

Heisalsoratherunfairtostones.

SomeoftheoldestrocksintheworldarefoundinGreenland,ina25-mile-longbandknownastheIsuasupracrustalbelt.TheyaretheoldestknownrocksamongthosethathavebeenlaiddownonthesurfaceoftheEarth,insteadofrisingfromthemantlebelow.Theyare3.8bilionyearsold,unlesswecannotreliablymakeinferencesfromobservations,inwhichcasetheevidenceforcosmicdesignhastobethrownoutalongwiththeevidenceoftherocks.Weknowtheiragebecausetheycontaintinycrystalsofzircon.WementionthemherebecausetheyshowthatPaley'slackofinterestin`stones',andhiscasualacceptancethattheymighthavèlainthereforever',areunjustified.ThestructureofastoneisnowherenearassimpleasPaleyassumed.Infact,itcanbejustasintricateasanorganism,thoughnotasobviouslyòrganised'.Everystonehasastorytotel.

Zirconsareacaseinpoint.

Zirconiumisthe40thelementintheperiodictable,andzirconiszirconiumsulphate.Itoccursinmanyrocks,butusualyinsuchtinyamountsthatitspresenceisignored.Itisextremelyhard-notashardasdiamond,butharder

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thanthehardeststeel.Jewelerssometimesuseitasadiamondsubstitute.

Zircons,then,arefoundinmostrocks,butinthisinstancetheimportantrockisgranite.Graniteisanigneousrock,whichwelsupfromthemoltenlayersbeneaththeEarth'scrust,forcingapaththroughtheoverlyingsedimentaryrockthathasbeendepositedbywindorwater.Zirconsformingranitethatsolidifiesabout12miles(20km)downinsidetheEarth.Thecrystalsaretrulytiny:one10,000thofaninch(2microns)istypical.

Overthelastfewdecadeswehavelearnedthatourapparentlystableplanetishighlydynamic,withcontinentsthatwanderaroundoverthesurface,carriedbygigantic`tectonicplates'whichare60miles(100km)thickandfloatontheliquidmantle.Sometimestheyevencrashintoeachother.Theymovelessthananinch(about2cm)peryear,onaverage,andonageologicaltimescalethat'sfast.

Thenorth-westofScotlandwasoncepartofNorthAmerica,whentheNorthAmericanplatecolidedwiththeEurasianplate;whentheplateslatersplitapart,apieceofAmericawasleftbehind,formingtheMoinethrust.

Whenplatescolide,theyslideovereachother,oftencreatingmountains.

ThehighestmountainsonEarthtoday,theHimalayas,formedwhenIndiacolidedwiththeAsianmainland.Theyarestilrisingtodaybymorethanhalfaninch(1.3cm)ayear,thoughareoftenweatheredawayfaster,andIndiaisstilmovingnorthwards.

Atanyrate,granitedeepwithintheEarthmaybeupliftedbythecolisionofcontinentalplates,toappearatthesurfaceaspartofamountainrange.

Beingahardrock,itsurviveswhenthesoftersedimentaryrocksthatsurrounditweatheraway.Buteventualy,evengraniteweathers,sothemountainerodes.Thezirconcrystalsareevenharder,sotheysurviveweathering;theyseparateoutfromthegranite,tobewasheddowntothecoastbystreamsandrivers,depositedonthesandyshore,andincorporatedintothenextlayerofsedimentaryrock.

Aswelasbeingveryhard,zirconischemicalyverystable,anditresistsmostchemicalchanges.So,asthesedimentbuildsup,andthezirconcrystalisburiedunderaccumulatingquantitiesofincipientrock,thecrystalisrelativelyimmune

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totheincreasingheatandpressure.Evenwhentherockiscookedbydeepheat,becomingmetamorphic-changingitschemicalstructure-thecrystalofzirconsurvives.Itsoneconcessiontotheextremeenvironmentarounditisthateventualyitbuildsanewlayer,likeaskin,onitssurface.This`rim',asitiscaled,isroughlythesameageasthesurroundingrock;theinnercoreisfarolder.

Nowtheprocessmayrepeat.Thecoreofzircon,withitsnewrim,maybepushedupwiththesurroundingrockstomakeanewmountainrange.

Whenthosemountainsweather,thezirconmayreturntothedepths,toacquireasecondrim.Thenathird,afourth...Justastreeringsindicatethegrowthofatree,sòzirconrims'reflectasequenceofmountain-buildinganderosion.Themaindifferenceisthateachringonatreecorrespondstoaperiodofoneyear,whereastherimsonthetinyzirconcrystalcorrespondtogeologicalcyclesthattypicalylasthundredsofmilionsofyears.But,justasthewidthsoftreeringstelussomethingabouttheclimateintheyearsthatarerepresented,sothezirconrimstelussomethingabouttheconditionsthatoccurredduringagivengeologicalcycle.

ByoneofthoseneatcoincidencesthatPaleywouldinterpretastheHandofGodbutnowadayswerecogniseasaninevitableconsequenceofthesheerrichnessoftheuniverse(yes,wedoseethatthosestatementsmightbethesame),thezirconiumatomhasthesameelectriccharge,andismuchthesamesize,asanatomofuranium.Souraniumimpuritiescaneasilysneakintothatzirconcrystal.Thisisgoodforscience,becauseuraniumisradioactive.Overtime,itdecaysintolead.Ifwemeasuretheratioofuraniumtoleadthenwecanestimatethetimethathaselapsedsinceanygivenpartofthezirconcrystalwaslaiddown.Nowwehaveapowerfulobservationaltool,ageologicalstopwatch.Andwealsohaveasimplepredictionthatgivesusconfidenceinthehypothesisthatthezirconcrystalformsinsuccessivestages.Namely,thecoreshouldbetheoldestpartofthecrystal,andsuccessiverimsshouldbecomeconsistentlyyounger,inseparatestages.

Atypicalcrystalmighthave,say,fourlayers.Thecoremightdateto3.7

bilionyearsago,thenextto3.6bilionyears,thethirdto2.6bilionyears,andthelastoneto2.3bilionyears.Sohere,inasimplèstone',wehaveevidenceforgeologicalcyclesthatlastbetween100milionandonebilionyears.Theorderoftheagesagreeswiththeorderinwhichthecrystalmusthavebeendeposited.

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Ifthegeneralscenarioenvisagedbygeologistswerewrong,thenitwouldtakeonlyasinglegrainofsandtodisproveit.Ofcoursethatdoesn'tconfirmthehugegeologicalcycles:thosearededucedfromotherevidence.Scienceisacrosswordpuzzle.

Zirconscanteachusmore.Itisthoughtthattheratiooftwoisotopesofcarbon,carbon-12andcarbon-13,maydistinguishorganicsourcesofcarbonfrominorganicones.ThereiscarbonintheIsuaformation,andtheratiotheresuggeststhatlifemayhaveexisted3.8bilionyearsago,surprisinglysoonaftertheEarth'ssurfacesolidified.Butthisconclusioniscontroversial,andmanyscientistsarenotconvincedthatotherexplanationscanbeexcluded.

Atanyrate,fortheIsuazirconsweknowthatitisnotanoptionforthemtohavèlainthereforever'.Stonesarefarmoreinterestingthantheymightseem,andanyonewhoknowshowtoreadtherockscandeducemanythingsabouttheirhistory.PaleybelievedthathecoulddeducetheexistenceofGodfromthecomplexityofaneye.Wecan'tgetGodfromazircon,butwecangetvastgeologicalcyclesofmountain-buildinganderosion...andjustpossibly,evidenceforexceedinglyancientlife.

Neverunderestimatethehumblestone.Itmaybeawatchindisguise.

Paley'spositionisthatwhatyouseeiswhatyouget.Theappearanceisthereality.HistitleNaturalTheologysaysasmuch,andhissubtitlecouldscarcelybeplainer.Organismslookdesignedbecausetheyaredesigned,byGod;theyappeartohaveapurposebecausetheydohaveapurpose:God's.EverywherePaleylooked,hesawtracesofGod'shandiwork;everythingaroundhimwasevidencefortheCreator.

Thatkindofèvidence'existsinsuchabundancethatthereisnodifficultyinaccumulatingexamples.Paley'scentralexamplewastheeye.Henoteditssimilaritytoatelescope,anddeducedthatsinceatelescopeisdesigned,somustaneyebe.Thecameradidnotexistinhisday,[1]butifithadexisted,hewouldhavefoundevenclosersimilarities.Theeye,likeatelescopeoracamera,hasalenstobring[1]Onlythecameraobscura,aroomwithapinholeinthewal.Paleyfirstwroteabouttheeyein1802,whereasgenuinephotographydatesfrom1826.

incominglighttoasharpfocus,forminganimage.Theeyehasaretinato

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receivethatimage,justasatelescopehasanobserver,orascreenontowhichtheimageisprojected.

Thelensoftheeyeisuselesswithouttheretina;theretinaisuselesswithoutthelens.Youcan'tputaneyetogetherpiecemeal-youneedalofit,atonce,oritcan'twork.LatersupportersoftheistexplanationsoflifeturnedPaley'ssubtleargumentsintoasimplisticslogan:`Whatuseishalfaneye?'

OnereasontodoubtPaley'sexplanationof`design'isthatinscience,youveryseldomgetwhatyousee.Natureisfarfromobvious.Thewavesontheoceanmayseemtobetraveling,butthewaterismainlygoingroundandroundintinycircles.(Ifitwasn't,thelandwouldquicklybeswamped.)TheSunmayappeartoorbittheEarth,butactualyit'stheotherwayround.

Mountains,apparentlysolidandstable,riseandfalovergeologicaltimescales.Continentsmove.Starsexplode.Sotheexplanationìtappearsdesignedbecauseitisdesigned'isabittootrite,abittooobvious,abittooshalow.Thatdoesn'tproveit'swrong,butitgivesuspause.

Darwinwasoneofaselectgroupofpeoplewhorealisedthattheremightbeanalternative.Insteadofsomecosmicdesignercreatingtheimpressiveorganisationoforganisms,thatorganisationmightcomeintobeingofitsownaccord.Or,moreaccurately,asaninevitableconsequenceofthephysicalnatureoflife,anditsinteractionswithitsenvironment.Livingcreatures,Darwinsuggested,arenottheproductofdesign,butofwhatwenowcalèvolution'-aprocessofslow,incrementalchange,almostimperceptiblefromonegenerationtothenext,butcapableofaccumulatingoverextensiveperiodsoftime.Evolutionisaconsequenceofthreethings.Oneistheabilityoflivingcreaturestopassonsomeoftheirattributestotheiroffspring.Thesecondistheslightlyhit-and-missnatureofthatability:whattheypassonisseldomaprecisecopy,thoughitusualycomesclose.Thethirdis`naturalselection'-creaturesthatarebetteratsurvivalaretheonesthatmanagetobreed,andpassontheirsurvivalattributes.

Naturalselectionisslow.

Asanaccomplishedstudentofgeology-Victorian-stylefieldgeology,whereyoutraipseaboutthelandscapetryingtoworkoutwhatrockslieunderyourfeet,orhalfwayupthenextmountain,andhowtheygotthere-

Darwinwaswelawareofthesheerabyssaldepthofgeologicaltime.Therecord

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oftherocksofferedcompelingevidencethattheEarthmustbevery,veryoldindeed:tensorhundredsofmilionsofyears,maybemore.

Today'sfigureof4.5bilionyearsisevenlongerthantheVictoriangeologistsdaredimagine,butprobablywouldnothavesurprisedthem.

Evenafewmilionyearsisaverylongtime.Smalchangescanturnintohugeonesoversuchaperiodoftime.Imagineaspeciesofwormfourinches(10cm)long,whoselengthincreasesbyonethousandthofapercenteveryyear,sothatevenveryaccuratemeasurementswouldnotdetectanychangeonayearlybasis.Inahundredmilionyears,thedescendantsofthatwormwouldbe30feet(10m)long.Fromannelidtoanaconda.Thelongestwormalivetodaysometimesreacheslengthsof150feet(50m),butitisamarineworm:Lineuslongissimus,whichlivesintheNorthSeaandcanbefoundunderbouldersatlowtide.Earthwormsarealotshorter,buttheMegascolecidwormsofAustraliacangrowtoalengthof10feet(3m),whichisstilimpressive.

We'renotsuggestingthatevolutionhappenswithquitethatdegreeofsimplicityorregularity,butthere'snoquestionthatgeologicaltimealowshugechangestooccurbyimperceptiblesteps.Infact,mostevolutionarychangesarealotfaster.Observationsof`Darwin'sfinches',13speciesofbirdthatinhabittheGalapagosIslands,revealmeasurablechangesfromoneyeartothenext-forexample,intheaveragesizesofthebirds'beaks.

IfwewanttoexplaintherichpanoplyoflifeonEarth,itisnotenoughtoobservethatlivingcreaturescanchangeasthegenerationspass.Theremustalsobesomethingthatdrivesthosechangesinàcreative'direction.

TheonlydrivingforcethatPaleycouldimaginewasGod,makingconscious,inteligentchoicesanddesigningtheminfromthebeginning.Darwinwasmoreacutelyawarethatorganismscananddochangefromeachgenerationtothenext.Boththefossilrecordandhisexperiencewiththebreedingofnewvarietiesofplantsanddomesticanimalsmadethatfactplain.Butbreedingisalsoachoiceimposedfromoutside,bythebreeder,soifanything,domesticanimalslooklikeevidenceinfavourofPaley.

Ontheotherhand,nohumanagencyeverbreddinosaurs.DoesthatimplythattheagencywasGod-ordidthedinosaurssomehowbreedthemselvesintonewforms?Darwinrealisedthatthereisanotherkindof`choice',imposednotby

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inteligentwilbutbycircumstanceandcontext.

Thisis`naturalselection'.Inthevast,ongoingcompetitionforfood,livingspace,andtheopportunitytobreed,naturewilautomaticalyfavourwinnersoverlosers.Competitionintroducesakindofratchet,whichmostlymovesinonedirection:towardswhateverworksbetter.Soweshouldnotbesurprisedthattinyincrementalchangesfromonegenerationtothenextshouldpossesssomesortofoveral`direction',ordynamic,withchangesaccumulatingcoherentlyacrosstheaeonstoproducesomethingentirelydifferent.

Thiskindofdescriptioniseasilymisunderstoodasakindofinbuilttendencytowards'progress'-everonwards,everupwards.Evermorecomplex.ManyVictorianstookthemessagethatthepurposeofevolutionwastobringhumanityintobeing.Wearethehighestformofcreation,weareatthetopoftheevolutionarytree.Withus,evolutionhasarrived;itwilnowstop,havingachieveditsultimategoal.

Rubbish.`Worksbetter'isnotanabsolutestatement.Itappliesinacontextthatisitselfchanging.Whatworksbettertodaymightnotdosoinamilionyears'time-oreventomorrow.Maybeforatime,abird'sbeakwil`workbetter'ifitisbiggerandstronger.Ifso,that'showitwilchange.Notbecausethebirdsknowwhatkindofbeakwilworkbetter:becausethekindofbeakthatworksbetteristhekindthatsurvivesmoreeffectivelyandisthereforemorelikelytobeinheritedbysucceedinggenerations.Buttheresultsofthecompetitionmaychangetherulesofthegame,sothatlateron,bigbeaksmaybecomeadisadvantage;forinstance,suitablefoodmaydisappear.Sonowsmalerbeakswilwin.

Inshort,thedynamicofevolutionisnotprescribedinadvance:itisèmergent'.Itcreatesitsowncontext,andreactstothatcontext,asitproceeds.Soatanygiventimeweexpecttofindsomesensibledirectionalitytoevolutionarychange,consistentovermanygenerations,butoftentheuniverseitselfonlyfindsoutwhatthatdirectionisbyexploringwhat'spossibleanddiscoveringwhatworks.Overalongertimescale,thedirectionitselfcanchange.It'slikeariverthatflowsthroughanerodinglandscape:atanygiventimethereisacleardirectiontotheflow,butinthelongrunthepassageoftherivercanslowlychangeitsowncourse.

Itisalsoimportanttoappreciatethatindividualorganismsdonotcompetein

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isolation,oragainstafixedbackground.Bilionsofcompetitionsgoonalthetime,andtheiroutcomemaybeaffectedbytheresultsofothercompetitions.It'snotliketheOlympics,wherethejavelinthrowerspolitelywaitforthemarathon-runnerstostreampast.It'smorelikeaversionoftheOlympicswherethejavelinthrowerstrytospearasmanymarathon-runnersastheycan,whilethesteeplechasersaretryingtostealtheirjavelinstoturneachhurdleintoaminiaturepolevault,andthemarathon-runners'mainaiminlifeistodrinkthewater-jumpbeforethesteeplechasersgettoitanddrinkitfirst.ThisistheEvolympics,whereeverythinghappensatonce.

Theevolutionarycompetitions,andtheiroutcomes,alsodependoncontext.Climate,inparticular,playsabigrole.IntheGalapagos,selectionforbeaksizeinDarwin'sfinchesdependsonhowmanybirdshavewhatsizeofbeak,andonwhatkindsoffood-seeds,insects,cactus-areavailableandinwhatquantities.Theamountandtypeoffooddependonwhichplantsandinsectsarecompetingbestinthestruggletosurvive-notleastfrombeingeatenby

finches-andbreed.Andalofthisisplayedoutagainstabackgroundofclimaticvariations:wetordrysummers,wetordrywinters.Observationspublishedin2002byPeterandRosemaryGrantshowthatthemainunpredictablefeatureoffinchevolutionintheGalapagosisclimate.Ifwecouldforecasttheclimateaccurately,wecouldpredicthowthefincheswouldevolve.Butwecan'tpredicttheclimatewelenough,andtherearereasonstothinkthatthismayneverbepossible.

Thatdoesn'tpreventevolutionfrombeing`predictive',henceascience,anymorethanitpreventsmeteorologyfrombeingascience.Buttheevolutionarypredictionsarecontingentuponthebehaviouroftheclimate.

Theypredictwhatwilhappeninwhatcircumstances,notwhenitwilhappen.

DarwinalmostcertainlyreadPaley'smasterworkasayoungman,andinlaterlifehemaywelhaveuseditasatouchstoneforhisown,moreradicalandfarmoreindirect,views.PaleysuccinctlyexpressedmanyofthemosteffectiveobjectionstoDarwin'sideas,longbeforeDarwinarrivedatthem.

IntelectualhonestydemandedthatDarwinshouldfindconvincinganswerstoPaley.SuchanswersarescatteredthroughoutDarwin'sepictreatiseTheOriginofSpecies,thoughPaley'snamedoesnotappear.

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Inparticular,Darwinfounditnecessarytotacklethethornyquestionoftheeye.Hisanswerwasthatalthoughthehumaneyeappearstobeaperfectedmechanism,withmanyinterdependentparts,thereareplentyofdifferentèyes'intheanimalkingdom,andalotofthosearerelativelyrudimentary.Theycanevenbearrangedinaroughprogressionfromsimplelightsensingpatchestopinholecamerastocomplexlenses(thoughthisarrangementshouldnotbeinterpretedasanactualevolutionarysequence).Insteadofhalfaneye,wefindaneyethatishalfaseffectiveatdetectinglight.Andthisisfar,farbetterthannoeyeatal.

Darwin'sapproachtotheeyeiscomplementedbysomecomputerexperimentspublishedbyDanielNilssonandSuzannePelger[1]in1994.

Theystudiedasimplemodeloftheevolutionofalightsensingpatchofcels,whosegeometrycouldchangeslightlyatevery`generation',andwhichwasequippedwiththecapacitytodevelopaccessoriessuchasalens.Intheirsimulations,amere100,000generationswereenoughtotransformalightsensingpatchintosomethingapproachingthehumaneye,includingalenswhoserefractiveindexvariedfromplacetoplace,toimproveitsfocus.Thehumaneyepossessesjustsuchalens.Moreover,andcrucialy,ateveryoneofthose100,000steps,theeye'sabilitytosenselightgotbetter.

Thissimulationwasrecentlycriticisedonthegroundsthatitgetsoutwhatitputsin.Itdoesn'texplainhowthoselightsensingcelscanappeartobeginwith,orhowtheeye'sgeometrycanchange.Anditusesarathersimplisticmeasureoftheeye'sperformance.Thesewouldbeimportantcriticismsifthemodelwerebeingusedassomekindofproofthateyesmustevolve,andasanaccuratedescriptionofhowtheydidit.However,thatwasneverthepurposeofthesimulation.Ithadtwomainaims.Onewastoshowthatinthesimplifiedcontextofthemodel,evolutionconstrainedbynaturalselectioncouldmakeincrementalimprovementsandgettosomethingresemblingarealeye.Itwouldn'tgetstuckalongthewaywithsomedead-endversionoftheeyethatcouldbeimprovedonlybyscrappingitandstartingafresh.Thesecondaimwastoestimatethetimerequiredforsuchaprocesstotakeplace(lookatthetitleofthepaper),ontheassumptionthatthenecessaryingredientswereavailable.

Someofthemodel'sassumptionsareeasilyjustified,asithappens.Lightcarriesenergyandenergyaffectschemicalbonds,soitisnot[1]'Apessimisticestimateofthetimerequiredforaneyetoevolve',ProceedingsoftheRoyalSocietyofLondonB,volume256(1994),pp.53-8.

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surprisingthatmanychemicalsrespondtolight.Evolutionhasanimmenserangeofmoleculestodrawon-proteinsspecifiedbyDNAsequencesingenes.Thecombinatorialpossibilitiesherearetrulyvast:theuniverseisnotbigenough,andhasnotlastedlongenough,tomakeonemoleculeofeachpossibleproteinascomplexas,say,haemoglobin,theoxygen-carrierinblood.Itwouldbeutterlyastonishingifevolutioncouldnotcomeupwithatleastonelightsensingpigment,andincorporateitintoacel.

Thereareevensomeideasofhowthismayhavehappened.InDebatingDesign,BruceWeberandDavidDepewpointoutthatlightsensitiveenzymesystemscanbefoundinbacteria,andthesesystemsareprobablyveryancient.Thebacteriadon'tusethemforvision,butaspartoftheirmetabolic(energy-gaining)processes.Proteinsinthehumanlensareverysimilartometabolicenzymesfoundintheliver.Sotheproteinsthatmaketheeyedidnotstartoutascomponentsofasystemwhosepurposewasvision.Theyaroseelsewhereandhadquitedifferent`functions'.Theirformandfunctionwerethenselectivelymodifiedwhentheirrudimentarylightsensingpowersturnedouttoofferanevolutionaryadvantage.

Althoughwenowknowquitealotaboutthegeneticsofthehumaneye,nobiologistclaimstoknowexactlyhowitevolved.Thefossilrecordispoor,andhumanoideyesdon'tfossilise(thoughtrilobiteeyesdo).Butbiologistscanoffersimplereasonswhyandhowtheeyecouldhaveevolved,andthesealonearesufficienttodemolishclaimsthatitsevolutionisimpossibleinprinciplebecausetheeye'scomponentsareinterdependentandremovinganyoneofthemcausestheeyetomalfunction.Theeyedidnotevolveonecomponentatatime.Itsstructureevolvedinparalel.

TheinstigatorsofmorerecentrevivalsofPaley'sdoctrine,albeitinlessovertlytheisttones,havetakenonboardthemessageoftheeyeasaspecificcase...butitsmoregenericaspectsseemtohaveeludedthem.Darwin'sdiscussionoftheeye,andtheNilsson-Pelgercomputerexperiment,arenotlimitedtoeyes.Hereisthedeepermessage.Whenconfrontedwithacomplexliving`mechanism',donotassumethattheonlywayitcanevolveiscomponentbycomponent,piecebypiece.Whenyouseeawatch,donotthinkofhookingupspringsandaddingcogwheelsfromsomestandardboxofspareparts.ThinkmoreofaSalvadorDalìsoftwatch'thatcanflowanddistort,deform,splitapart,andrejoin.Thinkofawatchwhosecogwheelscanchangeshape,grownewteeth,andwhoseaxlesandsupportsevolvealongwiththecogssothatateverystagethewholething

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fitstogether.Thinkofawatchthatmayhavestartedoutasapaperclip,andalongthewaybecameapogo-stick.Thinknotofawatchthatdoesandalwaysdidhaveasinglepurpose,whichwastotelthetime.Thinkofawatchthatonceheldsheetsofpapertogetherandcouldalsobestraightenedouttoformatoothpick,andwhichlaterturnedouttobegreatforbouncing,andstartedtobeusedformeasuringtimeonlywhensomeonenoticedthatitsrhythmicmovementscouldchartthepassingseconds.

Yes,proponentsofinteligentdesignunderstandtheeye...butonlyasoneexample,notasthebasisofageneralprinciple.Òh,yes,weknowalabouttheeye,'theysay(weparaphrase).`We'renotgoingtoaskwhatusehalfaneyeis.That'ssimple-mindednonsense.'Soinstead,theyaskwhatusehalfabacterialflagelumis,andtherebyrepeattheidenticalerrorinadifferentcontext.

WeowethisexampletoMichaelBehe,abiochemistwhowasbaffledbythecomplexityofbacterialflagela.Thesearethètails'thatbacteriausetomovearound,tiny`screws'likeaship'spropeler,drivenbyarotarymolecularmotor.Somefortyproteinsareinvolvedinmakingsuchamotor,andifyoumissanyofthemout,itwon'twork.Inhis1996Darwin'sBlackBox,Beheclaimedthattheonlypossiblewaytomakeaflagelumwastoencodethewholestructure,inadvance,inbacterialDNA.Thiscodecouldnothaveevolvedfromanythingsimpler,becausetheflagelumisìrreduciblycomplex'.

Anorganorbiochemicalsystemissaidtobeirreduciblycomplexifremovinganyofitspartscausesittofail.Behededucedthatnoirreduciblycomplexsystemcanevolve.Theexampleofthebacterialflagelumquicklybecameacornerstoneoftheinteligentdesignmovement,andBehe'sprincipleofirreduciblecomplexitywaspromotedasanunavoidablebarriertotheevolutionofcomplexstructuresandfunctions.

Thereareseveralexcelentbooksthatdebateinteligentdesign:we'vementionedtwoearlierinafootnote.It'sfairtosaythattheantisarewinningthedebatehandsdown-eveninbookseditedbythepros,suchasDebatingDesign.PerhapsthebiggestproblemfortheprosisthatBehe'sfundamentalconceptofìrreduciblecomplexity'hasfatalflaws.Withhisdefinition,thedeductionthatanirreduciblycomplexsystemcannotevolveisvalidonlyifevolutionalwaysconsistsofaddingnewparts.Ifthatwerethecase,thenthelogicisclear.Supposewehaveanirreduciblycomplexsystem,andsupposethatthereisanevolutionaryrouteleadingtoit.Focusonthefinalstep,wherethelastpartis

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added.Thenwhatevercamebeforemusthavebeenafailure,soitcouldn'thaveexisted.Thisisabsurd:endofstory.

However,evolutionneednotmerelyaddidentifiablecomponents,likeafactory-workerassemblingamachine.Itcanalsoremovethem-likeabuilderusingscaffoldingandthentakingitdownonceit'sdoneitsjob.Ortheentirestructurecanevolveinparalel.Eitherpossibilityalowsanirreduciblycomplexsystemtoevolve,becausethenexttolaststepnolongerhastostartfromasystemthatlacksthatfinal,vitalpiece.Instead,itcanstartfromasystemwithanextrapiece,andremoveit.Oraddtwovitalpiecessimultaneously.NothinginBehe'sdefinitionofirreduciblecomplexityprohibitseitherofthese.

Moreover,`fail'isaslipperyconcept:awatchthatlackshandsisafailureattelingthetime,butyoucanstiluseittodetonateatimebomb,orhangitonastringtomakeaplumb-line.Organsandbiochemicalsystemsoftenchangetheirfunctionsastheyevolve,aswe'vejustseeninthecontextoftheeye.Nosatisfactorydefinition

ofìrreduciblecomplexity'-onethatrealydoesconstituteabarriertoevolution-hasyetbeensuggested.

AccordingtoKennethMilerinDebatingDesign:`thegreatironyoftheflagelum'sincreasingacceptanceasaniconoftheantievolutionistmovementisthefactthatresearchhaddemolisheditsstatusasanexampleofirreduciblecomplexityalmostattheverymomentitwasfirstproclaimed'.Removingpartsfromtheflagelumdonotcauseittòfail'.Thebaseofthebacterialmotorisremarkablysimilartoasystemthatbacteriausetoattackotherbacteria,thètypeIIsecretorysystem'.Soherewehavethebasisofanentirelysensibleandplausibleevolutionaryroutetotheflagelum,inwhichproteincomponentsdogetaddedon.Whenyouremovethemagain,youdon'tgetaworkingflagelum-butyoudogetaworkingsecretorysystem.Thebacterialmethodofpropulsionmaywelhaveevolvedfromanattackmechanism.

Totheircredit,proponentsofinteligentdesignareencouragingthiskindofdebate,buttheyhavenotyetconcededdefeat,eventhoughtheirentireprogrammerestsonshakyfoundationsandiscolapsinginruins.

Creationists,desperatetosnatchatanystrawofscientificrespectabilityfortheirpoliticalprogrammetoleverreligionintotheAmericanstateschoolsystem,[1]

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havenotyetnoticedthatwhattheyarecurrentlytakingastheirscientificsupportisfalingapartattheseams.Thetheoryofinteligentdesignitselfisnotovertlytheist-indeeditsproponentstryveryhardnottodrawreligiousconclusions.Theywantthescientificargumentstobeconsideredasscience.Ofcoursethat'snotgoingtohappen,becausethetheistimplicationsarealittletooobvious-eventoatheists.

Therearesomethingsthatevolutiondoesnotexplain-whichwilgladdentheheartofanyonewhofeelsthat,Darwinnotwithstanding,therearesomeissuesthatsciencecannotaddress.

[1]'Theythemselvesrefertothisprogrammeasthe'wedgestrategy'.

ItisperfectlypossibletoagreewithDarwinandhissuccessorsthattheEarthis4.5bilionyearsold,andthatlifehasevolved,bypurelyphysicalandchemicalprocesses,frominorganicbeginnings-yetstilfindaplaceforadeity.Yes,inarichandcomplexuniverse,althesethingscanhappenwithoutdivineintervention.But...howdidthatrichandcomplexuniversecomeintobeing?

Here,today'scosmologyoffersdescriptionsofhow(BigBang,variousrecentalternatives)andwhen(about13bilionyearsago),butnotwhy.

Stringtheory,arecentinnovationatthefrontiersofphysics,makesaninterestingattemptat`why?'However,itleavesanevenbigger`why?'

unanswered:whystringtheory?Sciencedevelopstheconsequencesofphysicalrules(`laws'),butitdoesn'texplainwhythoserulesapply,orhowsuchaset-upcametoexist.

Thesearedeepmysteries.Atthemoment,andprobablyforever,theyarenotaccessibletothescientificmethod.Herereligionscomeintotheirown,offeringanswerstoriddlesaboutwhichsciencechoosestoremainmute.

Ifyouwantanswers,theyareavailable.

Ratheralotofdifferentones,infact.Choosewhicheveronemakesyoufeelmostcomfortable.

Feelingcomfortable,however,isnotacriterionrecognisedbyscience.Itmaymakeusfeelwarmandfuzzy,butthehistoricaldevelopmentofscientific

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understandingshowsthat,timeandagain,warmandfuzzyisjustapolitewayofsaying`wrong'.

Beliefsystemsrelyonfaith,notevidence.Theyprovideanswers-buttheydon'tprovideanyrationalprocesstoassessthoseanswers.Soalthoughtherearequestionsbeyondthecapacityofsciencetoanswer,that'smostlybecausesciencesetsitselfhighstandardsforevidence,andholdsitstonguewhenthereisn'tany.Thealegedsuperiorityofbeliefsystemscomparedtoscience,whenitcomestothesedeepmysteries,stemsnotfromafailureofscience,butfromthewilingness.ofbeliefsystemstoacceptauthoritywithoutquestion.

Sothereligiouspersoncantakecomfortthathisorherbeliefsprovideanswerstodeepquestionsofhumanexistencethatarebeyondthepowersofscience,andtheatheistcantakecomfortthatthereisabsolutelynoreasontoexpectthoseanswerstoberight.Butalsonowaytoprovethemwrong,sowhydon'twejustcoexistpeacefuly,stayoffeachother'sturf,andeachgetonwithourownthing?Whichiseasytosaybuthardertodo,especialywhensomepeoplerefusetosticktotheirownturf,andusepoliticalmeans,orviolence,topromotetheirviews,whenrationaldebatelongagodemolishedthem.

Someaspectsofsomebeliefsystemsaretestable,ofcourse-theGrandCanyonisnotevidenceforNoah'sflood,unlessGodishavingaquietjokeatourexpense,whichadmittedlywouldbeaveryDiscworldthingtodo.

AndifHeis,thenalbetsareoff,becauseHisrevealedwordin[insertyourpreferredHolyBook]maywelbeajoketoo.Otheraspectsarenottestable:thedeeperissuesstrayintointelectualterritorywhere,intheend,youhavetosettleforwhateverexplanationyourtypeofmindfindsconvincing,orjuststopaskingthatkindofquestion.

Butremember:what'smostinterestingaboutyourbeliefs,toanyonewhodoesnotsharethem,isnotwhetheryou'reright-it'sthatwhatyoubelieveisawindowintotheworkingsofyourmind.Àh,soyouthinklikethat,doyou?'

Thisiswherethegreatmysteryofhumanexistenceleads,andwherealexplanationsaretrue-foragivenvalueof`true'.

FIVE

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THEWRONGTROUSERSOFTIME

THEGLASSGLOBEOFROUNDWORLDhadbeeninstaledonapedestalinfrontofHexbythetimemostoftheseniorfacultywereupandmilingaround.TheywerealwaysatabitofalooseendwhenSecondBreakfast

hadfinishedanditwasn'tyettimeforElevenses,andthislookedlikeentertainment.

Òneasksoneselfwhetheritrealyisworthsaving,'saidtheChairofIndefiniteStudies.Ìt'shadhugeiceagesbefore,hasn'tit?Ifthehumansaretoostupidtoleaveintime,thenthere'sboundtobeanotherinterestingspeciesaroundinhalfamilionyearsorso.'

`Butextinctionisso...sortof...final,'saidtheLecturerinRecentRunes.

`Yes,andwecreatedtheirworldandhelpedthembecomeinteligent,'saidtheDean.`Wecan'tjustletthemfreezetodeath.It'dbelikegoingonholidayandnotfeedingthehamster.'

Awatchmakeraspartofthewatch,thoughtPonder,adjustingtheuniversity'sbiggestomniscope;notjustmakingtheworld,buttweakingitalthetime...

Wizardsdidnotbelieveingods.Theydidn'tdenytheirexistence,ofcourse.Theyjustdidn'tbelieve.Itwasnothingpersonal;theyweren'tactualyrudeaboutit.Godswereavisiblepartofthenarrativiumthatmadethingswork,thatgavetheworlditspurpose.Itwasjustthattheywerebestavoidedcloseup.

Roundworldhadnogodsthatthewizardshadbeenabletofind.Butonethatwasbuiltin...thatwasanewidea.Agodinsideeveryflowerandstone...notjustagodwhowaseverywhere,butagodwhowaseverywhere.

ThelastchapterofTheologyofSpecieshadbeenveryimpressive...

Hestoodback.Hexhadbeenbusyalmorning.SohadtheLibrarian.RightnowhewascarefulydustingbooksandfeedingthemintoHex'shopper.

Hexhadmasteredthesecretofosmoticreading,normalyonlyeverattempted

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bystudents.

AndtheLibrarianhadlocatedacopyoftherightOriginofSpecies,thebookDarwinoughttohavewritten.IthadapictureofDarwinasafrontispiece.Withapointyhathewouldhavepassedforawizardanywhere.Ifitcametothat,hecouldhavepassedfortheArchchancelor.

Ponderwaiteduntilthewizardshadsettleddownandopenedtheirpopcorn.

`Gentlemen,'hesaid,Ìdohopeyou'vealreadmyanalysis...?'

Thewizardsstaredathim.

Ìworkedveryhardonitalmorning,'saidPonder.Ànditwasdeliveredtoalyouroffices....'

Therewasmorestaring.

Ìthadagreencover....'Ponderprompted.

Thestaringwasquiteintensenow.Pondergavein.

`PerhapsIshouldremindyouoftheimportantpoints?'hesaid.

Thefaceslitup.

`Justjogourmemories,'saidtheDean,cheerfuly.

Ìdiscussedalternatetimelinesinphasespace,'[1]saidPonder.Thatwasamistake,hecouldsee.Hisfelowwizardsweren'tstupid,butyouhadtobecarefultoshapeideastofittheholesintheirheads.

[1]Phasespace,inagivencontext,isthespaceofeverythingthatmighthavehappened,notjustwhatdid.SeeTheScienceofDiscworld.

`TwodifferentlegsintheTrousersofTime,'saidPonder.Ìntheyear1859,bythecountingsystemcommonlyinuseinthatpartofRoundworld,abookchangedthewayalotofpeoplethoughtabouttheworld.Itjusthappenedtobethewrongbook-'

`Proveit,'saidtheChairofIndefiniteStudies.

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`Pardon,sir?'

`Wel,correctmeifI'mwrong,butsupposingTheologyofSpecieswastherightbook?'saidtheChair.

Ìtmutedscientific-thatis,technomantic-progressforalmostahundredyears,sir,'saidPonder,wearily.Ìtsloweddownhumanity'sunderstandingofitsplaceintheuniverse.'

`Youmeanthatitwasbuiltbywizardsandleftonashelfinacorridor?'saidtheChair.

`That'sonlytrueontheoutside,sir,'saidPonder.`Mypointis,somethinghappenedtoMrDarwinatsometimeinhislifethatcausedhimtowritethewrongbook.Anditwaswrong.Yes,itwouldhavebeentherightbookhereonDiscworld,sir.WeknowthereisaGodofEvolution.'

`That'sright.Skinnyoldchap,livesonanisland,'saidRidculy.`Decentsort,inhisway.Remember?Hewasredesigningtheelephantwhenwewerethere.Withwheels,veryclever.Verykeenonbeetles,too,asIrecal.'

`Sowhy'dDarwinwritethistheologybookinstead?'theChairofIndefiniteStudiespersisted.

Ìdon'tknow,sir,butasIwroteonpage4,I'msureyourecal,itwasthewrongbookatexactlytherighttime.Nevertheless,itmadesense.Therewassomethinginitforeveryone.Althetechnomancershadtodowasleaveaplaceintheirscienceforthelocalgod,andalthepriestshadtogiveupwereafewbeliefsthatnoneofthesensibleonesbelievedanyway-

'

`Suchaswhat?'saidtheDean.

`Wel,thattheworld·wascreatedinaweekandisn'tveryold,'saidPonder.

`Butthat'strue!'

Ònceagain,onlyontheoutside,Dean,'saidPondersmoothly.Àsfaraswecantel,TheologyofSpeciespolarisedintelectualopinioninacuriousway.Infact,

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haha,itequatorialisedit,youmightsay.'

Ìdon'tthinkwewould,'saidRidculy.`Whatdoesthewordmean?'

Àh...er,onaglobe,theequatorisanimaginarylinearoundthemiddle,'

saidPonder.`WhathappenedwasthatthebulkofthetechnomancersandthepriestsgotbehindtheideasexpressedinDarwin'sbook,becausetheygaveeveryoneprettymuchwhattheywanted.Quiteoffewofthetechnomancershadastrongbeliefinthegod,andmostofthebrighterpriestscouldseebigflawsinthedogma.Together,theywereaverylargeandinfluentialforce.Thehard-linereligionistsandtheunbendingtechnomancersweremarginalised.Outinthecold.Polarised,infact.'Thisratherneatpun,althoughhesaidithimself,failedtogetevenagroanofacknowledgement,sohewenton:`Theydidn'tagreewiththeunitedgroupandtheycertainlydidn'tagreewithoneanother.And,thus,happycompromiseruled.Forweloversixtyyears.'

`That'snice,'saidtheLecturerinRecentRunes.

Èr...yes,sir,andthenagain,no,'saidPonder.`Technomancydoesn'tworkwelinthosecircumstances.Itcan'tmakerealprogressbyconsensus.Hah,beingledbyabunchofself-satisfiedoldmenwhoaremoreinterestinginbigdinnersthanaskingquestionsisarecipeforstagnation,anyonecanseethat.'

Thewizardsnoddedsagely.

`Verytrue,'saidArchchancelorRidculy,narrowinghiseyes.`Thatwasanimportantpointwhichneededtobemade.'

`Thankyou,Archchancelor.'

Àndnowitneedstobeapologisedfor.'

`Sorry,Archchancelor.'

`Good.So,MrStibbons,whatdo-'

TherewasarattlefromHex'swritingengine.Thespideryarmswoveacrossthepaperandwrote:

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+++TheChairofIndefiniteStudiesiscorrect+++Thewizardsclusteredround.

`Rightaboutwhat?'saidPonder.

+++CharlesDarwinofTheologyofSpecieswasformuchofhislifeaRectorintheChurchofEngland,asub-setoftheBritishnation+++thecomputerscrawled.+++Thechieffunctionofthepriestsofthatreligionatthetimewastofurthertheartsofarchaeology,localhistory,lepidoptery,botany,palaeontology,geologyandthemakingoffireworks+++

`Priestsdidthat?'saidtheDean.`Whatabouttheprayingandsoon?'

+++Someofthemdidthattoo,yes,althoughitwasconsideredtobeshowingoff.TheGodoftheEnglishdidnotrequiremuchinthewayofsacrifice,onlythatpeopleacteddecentlyandkeptthenoisedown.Beingapriestinthatchurchwasanaturaljobforayoungmanofgoodbreedingandeducationbutnoveryspecifictalent.Intheruralareastheyhadmuchfreetime.MycalculationssuggestthatTheologyofSpecieswasthebookthathewasdestinedtowrite.Inalthehistoriesofthird-levelphasespace,thereisonlyoneinwhich

hewritesTheOriginofSpecies+++

`Whyisthat?'saidPonder.

+++Theexplanationiscomplex+++

`Wel,outwithit,'saidRidculy.`We'realsensiblemenhere.'

AnotherpieceofpaperslidoffHex'stray.Itread:+++Yes.Thatistheproblem.Youunderstandthateverypossibilityofchoicegivesbirthtoanewuniverseinwhichthatchoiceismanifest?+++

`ThisistheTrousersofTimeagain,isn'tit?'saidRidculy.

+++Yes.ExceptthateverylegoftheTrousersofTimebranchesintomanyotherlegs,andsodothoselegsandeveryfolowingleg,untileverywhereisfuloflegs,whichoftenpassthroughoneanotherorjoinupagain+++

ÌthinkI'mlosin'track,'saidRidculy.

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+++Yes.Languageisnotgoodatthis.Evenmathematicsgetslost.

Butalittlestorymightwork.Iwiltelyouthestory.Itwilbenotcompletelyinaccurate+++

`Goahead,'saidRidculy.

+++Imagineanunimaginablylargenumber+++

`Right.Noproblemthere,'saidRidculy,afterthewizardshadconsultedamongthemselves.

+++Verywel+++Hexwrote.+++FromthemomentthattheRoundworlduniversewasmade,itbegantosplitintoalmostidenticalcopiesofitself,bilionsoftimesasecond.ThatunimaginablylargenumberrepresentsalpossibleRoundworlduniversesthatthereare+++

`Doaltheseuniversesrealyexist?'saidtheDean.

+++Impossibletoprove.Assumethattheydo.InalthoseuniversestherearehardlyanyinwhichamancaledCharlesDarwinexists,takesamomentousoceanvoyage,andwritesahugelyinfluentialbookabouttheevolutionoflifeontheplanet.Nevertheless,thatnumberisstilunimaginablylarge+++

`Butimaginedbyasmalerimagination?'saidRidculy.Ìmean,isithalfasmanyastheotherunimaginablenumber?'

+++No.Itisunimaginablylarge.Butcomparedtothefirstnumber,itisunimaginablysmal+++

Thewizardsdebatedthisinwhispers.

`Verywel,'saidRidculy,atlast.`Keepgoin'andwe'lkindofjoininwhenwecan.'

+++Evenso,itisnotsounimaginableasthenumberofuniversesinwhichthebookwasTheOriginofSpecies.Thatnumberisquitestrangeandcanonlybeimaginedatalinveryunusualcircumstances+++

Ìt'sunimaginablylarger?'saidRidculy.

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+++justunimaginablyunique.Thenumberone.Gentlemen.Albyitself.

Oneisoneandalalone.One.Yes.Inthird-levelphasespacethereisonlyonehistorywherehegetsontheboat,completesthevoyage,considersthefindingsandwritesthatbook.AltheotheralternativeDarwinseitherdidnotexist,didnotstayontheboat,didnotsurvivethejourney,didnotwriteanybookatalorwrote,inalargenumberofcases,TheologyofSpeciesandenteredtheChurch+++

`Boat?'saidPonder.`Whatboat?What'veboatsgottodowithit?'

+++Iexplained,inthesuccessfultimelinewhichledtohumanityleavingtheplanet,MrDarwinmakesasignificantvoyage.Itisoneofnineteenpivotaleventsinthehistoryofthespecies.ItisalmostasimportantasJoshuaGoddelsonleavinghishousebythebackdoorin1734+++

`Whowashe?'saidPonder.Ìdon'trecalthename.'

+++AshoemakerlivinginHamburg,Germany+++wroteHex.

+++Hadhelefthishousebythefrontdoorthatday,commercialnuclearfusionwouldnothavebeenperfected283yearslater+++`Thatwasimportant,wasit?'saidRidculy.

+++Vastly.Majortechnomancy+++

`Diditneedmuchinthewayofshoes,then?'saidRidculy,mystified.

+++No.Butthechainofcausality,thoughcomplex,isclear+++`Howhardisittogetonthisboat?'saidtheDean.+++InthecaseofCharlesDarwin,veryhard+++`Wherediditgo?'

+++ItsailedfromEnglandtoEngland.Buttherewerecrucialstopsalongtheway.Eveninthosehistorieswherehedidembarkontheboat,hedidnotcompletethevoyageandcompleteTheOriginofSpeciesineverycasebutone+++

`Justoneversionofhistory,yousay,'saidPonderStibbons.`Doyouknowwhy?'

+++Yes.Itistheonewhereyouintervene+++`Butwehaven'tintervened,'

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saidRidculy.

+++Inaprimitivesubjectivesensethisisthecase.However,youaregoingtowilhavealreadysoon+++Hexwrote.

`What?AndIamnotaprimitivesubject,MrHex!'

+++Iamsorry.Itishardtoconveyfive-dimensionalideasinalanguageevolvedtoscreamdefianceatthemonkeysinthenexttree+++

Thewizardslookedatoneanother.

`Gettingamanonashipcan'tbehard,surely?'saidtheDean.

ÌsitdangerousinDarwin'stime?'saidRincewind.

+++Inevitably.ThecentreoftheGlobeisaninferno,humanityisprotectedfrombeingfriedalivebynothingmorethanaskinofairandmagneticforces,andthechanceofanasteroidstrikeiseverpresent+++

ÌthinkRincewindwasreferringtomoreimmediateconcerns,'saidRidculy.

+++Understood.Themajorcityyoumustvisithasmanysqualidareasandopensewers.Theriverbisectingitisnoxious.Yourdestinationcouldbeconsideredahigh-crimedrainageditchinadangerousanddirtyworld+++

`Prettymuchlikehere,youmean?'

+++Thesimilarityisnoticeable,yes+++

Thewritingarmsstoppedmoving.BitsofHexrattledandshook.Theantsceasedtheirpurposefulscurryingandbegantomilaboutaimlesslyintheirglasstubing.Hexappearedtohavesomethingonhismind.

Thenonewritingarmdippeditspenintotheinkandwrote,slowly:+++Thereisanadditionalproblem.ItisnotcleartomewhyDarwindidnotwriteOriginsomewhereinthemultipleuniverseswithoutyourforthcomingassistance+++

`Wehaven'tdecidedthatwewil-'Ridculybegan.

+++Butyouaregoingtohavedone+++

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`Wel,probably-'

+++AcrosstheentirephasespaceofthisworldCharlesDarwindidmanythings.Hebecameanexpertwatchmaker.Heranapotteryfactory.Inmanyworldshewasacountrypriest.Inothers,hewasageologist.Inyetothers,hedidmaketheimportantvoyageand,asaresultwroteTheologyofSpecies.InsomehebegantowriteTheOriginofSpeciesonlytogiveup.OnlyinonetimelinewasOriginpublished.Thisshouldnotbepossible.

Idetect...+++

+++Idetect...+++

Thewizardswaitedpolitely.

`Yes?'saidPonder.

Thesinglepenmovedacrossthepaper.

+++MALIGNITY+++

SIX

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BORROWEDTIME

THEEVER-BRANCHINGLEGSOFtheTrousersofTimeareametaphor(unlessyouareaquantumphysicist,inwhichcasetheyrepresentacertainmathematicalviewofreality)forthemanypathsthathistorymighthavetakenifeventshadbeenslightlydifferent.Later,we'lthinkaboutalthoselegs,butfornow,werestrictattentiontoonetrouser.Onetimeline.Whatexactlyistime?

WeknowwhatitisonDiscworld.`Time',statesTheNewDiscworldCompanion,ìsoneoftheDiscworld'smostsecretiveanthropomorphicpersonifications.Itishazardedthattimeisfemale(shewaitsfornoman)butshehasneverbeenseeninthemundaneworlds,havingalwaysgonesomewhereelsejustamomentbefore.Inherchronophoniccastle,madeupofendlessglassrooms,shedoesat,er,times,materialiseintoatalwomanwithdarkhair,wearingalongred-and-blackdress.'

Tick.

EvenDiscworldhastroublewithtime.InRoundworldit'sworse.Therewasatime(therewego)whenspaceandtimewereconsideredtobetotalydifferentthings.Spacehad,orwas,extension-itsortofspreaditselfaround,andyoucouldmovethroughitatwil.Withinreason,maybe20

miles(30km)adayonagoodhorseifthetracksweren'ttoomuddyandthehighwaymenweren'ttooobtrusive.

Tick.

Time,incontrast,movedofitsownvolitionandtookyoualongwithit.Timejustpassed,atafixedspeedofonehourperhour,alwaysinthedirectionofthefuture.Thepasthadalreadyhappened,thepresentwashappeningrightnow-oops,gonealready-andthefuturehadyettohappen,butbyjingo,itwould,youmarkmywords,whenitwasgoodandready.

Tick.

Youcouldchoosewhereyouwentinspace,butyoucouldn'tchoosewhenyouwentintime.Youcouldn'tvisitthepasttofindoutwhathadrealyhappened,or

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visitthefuturetofindoutwhatfatehadinstoreforyou;youjusthadtowaitandfindout.Sotimewascompletelydifferentfromspace.

Spacewasthree-dimensional,withthreeindependentdirections:left/right,back/forward,up/down.Timejustwas.

Tick.

ThenalongcameEinstein,andtimestartedtogetmixedupwithspace.

Timelikedirectionswerestildifferentfromspace-likeones,insomeways,butyoucouldmixthemupabit.Youcouldborrowtimehereandpayitbacksomewhereelse.Evenso,youcouldn'theadoffintothefutureandfindyourselfbackinyourownpast.Thatwouldbetimetravel,whichplayednopartinphysics.

Whatscienceabhors,theartscrave.Timetravelmaybeaphysicalimpossibility,butitisawonderfulnarrativedeviceforwriters,becauseitalowsthestorytomovetopast,present,orfuture,atwil.Ofcourseyoudon'tneedatimemachinetodothat-theflashbackisastandardliterarydevice.Butit'sfun(andrespectfultonarrativium)tohavesomekindofrationalethatfitsintothestoryitself.Victorianwriterslikedtousedreams;agoodexampleisCharlesDickens'sAChristmasCarolof1843,withitsghostsofChristmaspast,present,andyet-to-come.Thereisevenaliterarysubgenreof'timeslipromances',someofthemrealyquitesteamy.

TheFrenchones.

Timetravelcausesproblemsifyoutreatitasmorethanjustaliterarydevice.Whenaliedtofreewil,itleadstoparadoxes.Theultimateclichehereisthègrandfatherparadox',whichgoesbacktoReneBarjavel'sstoryLeVoyageurImprudent.Yougobackintimeandkilyourgrandfather,butbecauseyourfatheristhennotborn,neitherareyou,soyoucan'tgobacktokilhim...Quitewhyit'salwaysyourgrandfatherisn'tclear(exceptasasignthatit'sacliche,alow-bredformofnarrativium).

Kilingyourfatherormotherwouldhavethesameparadoxicalconsequences.AndsomighttheslaughterofaCretaceousbutterfly,asinRayBradbury's1952shortstoryÀSoundofThunder',inwhichabutterfly'saccidentaldemiseatthehands[1]ofanunwittingtimetravelerchangespresent-daypoliticsforthe

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worse.

Anothercelebratedtimeparadoxisthecumulativeaudienceparadox.

Certainevents,thestandardonebeingtheCrucifixion,aresoendowedwithnarrativiumthatanyself-respectingtimetouristwilinsistonseeingthem.TheinevitableconsequenceisthatanyonewhovisitstheCrucifixionwilfindChristsurroundedbythousands,ifnotmilions,oftimetravelers.Athirdistheperpetualinvestmentparadox.Putyourmoneyinabankaccountin1955,takeitoutin2005,withaccumulatedinterest,thentakeitbackto1955andputitinagain...Becarefultousesomethinglikegold,notnotes-notesfrom2005won'tbevalidin1955.RobertSilverberg'sUptheLineisabouttheTimeService,aforceoftimepolicewhosejobistopreventsuchparadoxesfromgettingoutofhand.AsimilarthemeoccursinIsaacAsimov'sTheEndofEternity.

Anentireclassofparadoxesarisesfromtimeloops,closedloopsofcausalityinwhicheventsonlygetstartedbecausesomeonecomesfromthefuturetoinitiatethem.Forexample,theeasiestwayfortoday'shumanitytogetholdofatimemachineisifsomeoneispresentedwithonebyatimetravelerfromthefarfuture,whensuch[1]Actualy,foot.

machineshavealreadybeeninvented.Heorshethenreverseengineersthemachinetofindouthowitworks,andtheseprincipleslaterformthebasisforthefutureinventionofthemachine.TwoclassicstoriesofthistypeareRobertHeinlein's'ByHisBootstraps'andÀlyouZombies',thesecondbeingnoteworthyforaprotagonistwhobecomeshisownfatherandhisownmother(viaasexchange).DavidGerroldtookthisideatoextremesinTheManWhoFoldedHimself.

Science-fictionauthorsaredividedonwhethertimeparadoxesalwaysneatlyunwrapthemselvestoproduceconsistentresults,orwhetheritisgenuinelypossible,intheirfictionalsetting,tochangethepastorthepresent.(Nooneworriesmuchaboutchangingthefuture,mindyou,presumablybecausèfreewil'amountstopreciselythat.Wealchangethefuture,fromwhatitmighthavebeentowhatitactualybecomes,thousandsoftimeseveryday.Orsowefondlyimagine.)Sosomeauthorswriteofattemptstokilyourgrandfatherthat,bysomeneattwist,bringyouintoexistenceanyway.Forexample,yourtruefatherwasnothissonatal,butamanhekiled.Bymistakenlyeliminatingthewronggrandfather,youensurethatyourtruefathersurvivestosireyou.Others,like

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AsimovandSilverberg,setupentireorganisationsdedicatedtomakingsurethatthepast,hencethepresent,remainsintact.Whichmayormaynotwork.

Theparadoxesassociatedwithtimetravelarepartofthesubject'sfascination,buttheydoratherpointtowardstheconclusionthattimetravelisalogicalimpossibility,letaloneaphysicalone.SowearehappytoalowthewizardsofUnseenUniversity,whoseworldrunsonmagic,thefacilitytowanderatwilupanddowntheRoundworldtimeline,switchinghistoryfromoneparaleluniversetoanother,tryingtogetCharlesDarwin-

orsomebody-towriteThatBook.ThewizardsliveinDiscworld,theyoperateoutsideRoundworldconstraints.Butwedon'trealyimaginethatRoundworldpeoplecoulddothesame,withoutexternalassistance,usingonlyRoundworld

science.

Strangely,manyscientistsatthefrontiersoftoday'sphysicsdon'tagree.

Tothem,timetravelhasbecomeanentirelyrespectable[1]researchtopic,paradoxesnotwithstanding.Itseemsthatthereisnothinginthèlaws'ofphysics,aswecurrentlyunderstandthem,thatforbidstimetravel.Theparadoxesareapparentratherthanreal;theycanbèresolved'withoutviolatingphysicallaw,aswewilseeinChapter8.Thatmaybeaflawintoday'sphysics,asStephenHawkingmaintains;his`chronologyprotectionconjecture'statesthatasyetunknownphysicallawsconspiretoshutdownanytimemachinejustbeforeitgetsassembled-abuilt-incosmologicaltimecop.

Ontheotherhand,thepossibilityoftimetravelmaybeaprofoundstatementabouttheuniverse.Weprobablywon'tknowforsureuntilwegettotackletheissueusingtomorrow'sphysics.Andit'sworthremarkingthatwedon'trealyunderstandtime,letalonehowtotravelthroughit.

Although(apparently)thelawsofphysicsdonotforbidtimetravel,itturnsoutthattheydomakeitverydifficult.Onetheoreticalschemeforachievingthatgoal,whichinvolvestowingblackholesaroundveryfast,requiresrathermoreenergythaniscontainedintheentireuniverse.Thisisabitofabummer,anditdoesseemtoruleoutthetypicalsciencefictiontimemachine,aboutthesizeofacar[2]

ThemostextensivedescriptionsofDiscworldtimearefoundinThiefofTime.

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TheingredientsforthisnovelincludeamemberoftheGuildofClockmakers,JeremyClockson,whoisdeterminedtomakeacompletelyaccurateclock.However,heisupagainstatheoreticalbarrier,theparadoxesoftheEphebianphilosopherXeno,whicharefirstWel,let'snotexaggerate.Youcanpublishpapersonitwithoutriskinglosingyourjob.It'scertainlybetterthanpublishingnothing,whichdefinitelywilloseyouyourjob.

[2]Indeed,intheBacktotheFuturemoviesequence,itwasacar.ADelorean.Thoughitdidneedtheassistanceofarailwaylocomotiveatonepoint.

mentionedinPyramids.ARoundworldphilosopherwithanoddlysimilarname,ZenoofElea,bornaround490BC,statedfourparadoxesabouttherelationbetweenspace,timeandmotion.HeisXeno'sRoundworldcounterpart,andhisparadoxesbearacuriousresemblancetotheEphebianphilosopher's.Xenoprovedbylogicalonethatanarrowcannothitarunningman,[1]andthatthetortoiseisthefastestanimalontheDisc.[2]Hecombinedbothinoneexperiment,byshootinganarrowatatortoisethatwasracingagainstahare.Thearrowhittheharebymistake,andthetortoisewon,whichprovedthathewasright.InPyramids,Xenodescribesthethinkingbehindthisexperiment.

"squitesimple,'saidXeno.`Look,let'ssaythisolivestoneisanarrowandthis,andthis-'hecastaroundaimlessly-'andthisstunnedseagulisthetortoise,right?Now,whenyoufirethearrowitgoesfromheretotheseag-thetortoise,amIright?'

Ìsupposeso,but-'

`But,bythistime,theseagu-thetortoisehasmovedonabit,hasn'the?

AmIright?'

'Isupposeso,'saidTeppic,helplessly.Xenogavehimalookoftriumph.

`Sothearrowhastogoabitfurther,doesn'tit,towherethetortoiseisnow.Meanwhilethetortoisehasflow-movedon,notmuch,I'lgrantyou,butitdoesn'thavetobemuch.AmIright?Sothearrowhasabitfurthertogo,butthepointisthatbythetimeitgetstowherethetortoiseisnowthetortoiseisn'tthere.Soifthetortoisekeepsmoving,thearrowwilneverhitit.It'lkeepgettingcloserandcloser,butit'lneverhitit.QED.'

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[1]Provideditisfiredbysomeonewhohasbeeninthepubsincelunchtime.

[2]Actualythisistheambiguouspuzuma,whichtravelsatnear-lightspeed(whichontheDiscisaboutthespeedofsound).Ifyouseeapuzuma,it'snotthere.Ifyouhearit,it'snotthereeither.

Zenohasasimilarset-up,thoughhegarblesitintotwoparadoxes.Thefirst,caledtheDichotomy,statesthatmotionisimpossible,becausebeforeyoucangetanywhere,youhavetogethalfway,andbeforeyoucangetthere,youhavetogethalfwaytothat,andsoonforever...soyouhavetodoinfinitelymanythingstogetstarted,whichissily.Thesecond,AchilesandtheTortoise,isprettymuchtheparadoxenunciatedbyXeno,butwiththeharereplacedbytheGreekheroAchiles.Achilesrunsfasterthanthetortoise-faceit,anyonecanrunfasterthanatortoise-buthestartsabitbehind,andcannevercatchupbecausewheneverhereachestheplacewherethetortoisewas,it'smovedonabit.Liketheambiguouspuzuma,bythetimeyougettoit,it'snotthere.Thethirdparadoxsaysthatamovingarrowisn'tmoving.Timemustbedividedintosuccessiveinstants,andateachinstantthearrowoccupiesadefiniteposition,soitmustbeatrest.Ifit'salwaysatrest,itcan'tmove.ThefourthofZeno'sparadoxes,theMovingRows(orStadium),ismoretechnicaltodescribe,butitboilsdowntothis.Supposethreebodiesarelevelwitheachother,andinthesmalestinstantoftimeonemovesthesmalestpossibledistancetotheright,whiletheothermovesthesmalestpossibledistancetotheleft.Thenthosetwobodieshavemovedapartbytwicethesmalestdistance,takingthesmalestinstantoftimetodothat.Sowhentheywerejustthesmalestdistanceapart,halfwaytotheirfinaldestinations,timemusthavechangedbyhalfthesmalestpossibleinstantoftime.Whichwouldbesmaler,whichiscrazy.

ThereisaseriousintenttoZeno'sparadoxes,andareasonwhytherearefourofthem.TheGreekphilosophersofRoundworldantiquitywerearguingwhetherspaceandtimewerediscrete,madeupofindivisibletinyunits,orcontinuous-infinitelydivisible.Zeno'sfourparadoxesneatlydisposeofalfour

combinations

of

continuous/discrete

for

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space

with

continuous/discretefortime,neatlystuffingeveryoneelse'stheories,whichishowyoumakeyourmarkinphilosophicalcircles.Forinstance,theMovingRowsparadoxshowsthathavingbothspaceandtimediscreteiscontradictory.

Zeno'sparadoxesstilshowuptodayinsomeareasoftheoreticalphysicsandmathematics,althoughAchilesandtheTortoisecanbedealtwithbyagreeingthatifspaceandtimearebothcontinuous,theninfinitelymanythingscan(indeedmust)happeninafinitetime.TheArrowparadoxcanberesolvedbynotingthatinthegeneralmathematicaltreatmentofclassicalmechanics,knownasHamiltonianmechanicsafterthegreat(anddrunken)IrishmathematicianSirWiliamRowanHamilton,thestateofabodyisgivenbytwoquantities,notone.Aswelaspositionitalsohasmomentum,adisguisedversionofvelocity.Thetwoarerelatedbythebody'smotion,buttheyareconceptualydistinct.Alyouseeisposition;momentumisobservableonlythroughitseffectonthesubsequentpositions.Abodyinagivenpositionwithzeromomentumisnotmovingatthatinstant,andsowilnotgoanywhere,whereasoneinthesamepositionwithnon-zeromomentum-whichappearsidentical-ismoving,eventhoughinstantaneouslyitstaysinthesameplace.

Gotthat?

Anyway,weweretalkingaboutThiefofTime,andthankstoXenowe'venotyetgotpastpage21.ThemainpointisthatDiscworldtimeismaleable,sothelawsofnarrativeimperativesometimesneedalittlehelptomakesurethatthenarrativedoeswhattheimperativesaysitshould.

Tick.

LadyMyriaLejeanisanAuditorofreality,whohastemporarilyassumedhumanform.Discworldisrelentlesslyanimistic;virtualyeverythingisconsciousonsomelevel,includingbasicphysics.TheAuditorspolicethelawsofnature;theywouldverylikelyfineyouforexceedingthespeedoflight.Theynormalytaketheformofsmalgreyrobeswithacowl-andnothinginside.Theyaretheultimatebureaucrats.LejeanpointsouttoJeremythattheperfectclockmustbeabletomeasureXeno'ssmalestunitoftime.Ìtmustexist,mustn'tit?Considerthepresent.Itmusthavealength,becauseoneendofitisconnectedtothepast

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andtheotherisconnectedtothe

future,andifitdidn'thavealengththenthepresent.couldn'texistatal.

Therewouldbenotimeforittobethepresentin.'

Herviewscorrespondrathercloselytocurrenttheoriesofthepsychologyoftheperceptionoftime.Ourbrainsperceiveanìnstant'asanextended,thoughbrief,periodoftime.Thisisanalogoustothewaydiscreterodsandconesintheretinaseemtoperceiveindividualpoints,butactualysampleasmalregionofspace.Thebrainacceptscoarse-grainedinputsandsmoothsthemout.

LejeanisexplainingXenotoJeremybecauseshehasahiddenagenda:ifJeremysucceedsinmakingtheperfectclock,thentimewilstop.ThiswilmaketheAuditors'taskasclerksoftheuniversemuchsimpler,becausehumansarealwaysmovingthingsaround,whichmakesitdifficulttokeeptrackoftheirlocationsintimeandspace.

Tick.

NeartheDiscworldHub,inahigh,greenvaley,liesthemonasteryofOiDong,wherelivethefightingmonksoftheorderofWen,otherwiseknownasHistoryMonks.Theyhavetakenuponthemselvesthetaskofensuringthattherighthistoryhappensintherightorder.ThemonksknowwhatisrightbecausetheyguardtheHistoryBooks,whicharenotrecordsofwhatdidhappen,butinstructionsforwhatshould.

AyoungsternamedLudd,afoundlingbroughtupbytheThieves'Guild,wherehewasanexceptionalytalentedstudent,hasbeenrecruitedtotheranksoftheHistoryMonksandgiventhenameLobsang.Themonks'maintechnologicalaidsareprocrastinators,hugespinningmachinesthatstoreandmovetime.Withaprocrastinator,youcanborrowtimeandpayitbacklater.Lobsangwouldn'tdreamoflivingonborrowedtime,though-butifitwasn'tnaileddown,hewouldalmostcertainlystealit.Hecanstealanything,andusualydoes.And,thankstotheprocrastinators,timeisnotnaileddown.

Ifyouhaven'tgotthejokebynow,takeanotherlookatthetitle.

Lejean'splanworks;Jeremybuildshisclock.

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Timestops,whichiswhattheAuditorswanted.NotonlyonDiscworld:temporalstasisexpandsacrosstheuniverseatthespeedoflight.Soon,everythingwilstop.TheHistoryMonksarepowerless,forthey,too,havestopped.OnlySusanStoHelit,Death'sgranddaughter,cangettimestartedagain.AndRonnieSoak,whousedtobeKaos,theFifthHorsemanoftheApocralypse,butleftbecauseofartisticdisputesbeforetheybecamefamous...Fortunately,theAuditorslikeobeyingrules,andDONOTFEEDTHEELEPHANTrealyperplexesthemwhenthereisnoelephanttofeed.Fataly,theyalsohavealove-haterelationshipwithchocolate.Theyarelivingonstolentime.

Aprocrastinatorisasortoftimemachine,butitmovestimeitself,insteadofmovingpeoplethroughtime.Moreover,it'sfact,notfiction,asisalofDiscworldtothosewholivethere.OnRoundworld,thefirstfictionaltimemachine,asopposedtodreamsornarrativetimeslip,seemstohavebeeninventedbyEdwardMitchel,aneditorfortheNewYorkSunnewspaper.In1881hepublishedananonymousstory,`TheClockThatWentBackward',inhispaper.ThemostcelebratedtimetravelgadgetappearsinHerbertGeorgeWels'snovelTheTimeMachineof1895,andthissetastandardforalthatfolowed.ThenoveltelsofaVictorianinventorwhobuildsatimemachineandtravelsintothefarfuture.Therehefindsthathumanityhasspeciatedintotwodistincttypes-thenastyMorlocks,wholivedeepinsidecaverns,andtheetherealEloi,whoarepreyedonbytheMorlocksandaretooindolenttodoanythingaboutit.Severalmovies,alfairlyghastly,havebeenbasedonthebook.

Thenovelhadinauspiciousbeginnings.Welsstudiedbiology,mathematics,physics,geology,drawing,andastrophysicsattheNormalSchoolofScience,whichbecametheRoyalColegeofScienceandeventualymergedwithImperialColegeofScienceandTechnology.Whileastudentthere,hebegantheworkthatleduptoTheTimeMachine.Hisfirsttimetravelstory`TheChronicArgonauts'appearedin1888intheScienceSchoolsJournal,whichWelshelpedtofound.Theprotagonistvoyagesintothepastandcommitsamurder.Thestoryoffersnorationalefortimetravelandismoreofamad-scientisttaleinthetraditionofMarySheley'sFrankenstein,butnowherenearaswelwritten.Welslaterdestroyedeverycopyofithecouldlocate,becauseitembarrassedhimsomuch.Itlackedeventheparadoxicalelementofthe1891Tourmalin'sTimeChequesbyThomasAnsteyGuthrie,whichintroducedmanyofthestandardtimetravelparadoxes.

Overthefolowingthreeyears,Welsproducedtwomoreversionsofhis

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timetravelstory,nowlost,butalongthewaythestorylinemutatedintoafar-futurevisionofthehumanrace.Thenextversionappearedin1894intheNationalObservermagazine,asthreeconnectedtaleswiththetitlèTheTimeMachine'.Thisversionhasmanyfeaturesincommonwiththefinalnovel,butbeforepublicationwascomplete,theeditorofthemagazinemovedtotheNewReview.Therehecommissionedthesameseriesagain,butthistimeWelsmadesubstantialchanges.Themanuscriptsincludemanyscenesthatwereneverprinted:theherojourneysintothepast,runningintoaprehistorichippopotamus[1]andmeetingthePuritansin1645.Thepublishedmagazineversionisverysimilartotheonethatappearedinbookformin1895.InthisversiontheTimeTravelermovesonlyintothefuture,wherehefindsoutwhatwilhappentothehumanrace,whichsplitsintothelanguidEloiandthehorridMorlocks-bothequalydistasteful.

[1]Asonedoes.Palaeontologistshavejustannouncedthattheyhavefoundremarkablywel-preservedfossilsinanEastAnglianquarry,showingthatgianthipposweighingsixorseventons-roughlytwicetheweightofmodemhippos-walowedintheriversofNorfolk600,000yearsago.Itwasawarmperiodsandwichedbetweentwoiceages,probablyafewdegreeswarmerthanthepresentday(youcantelthatfrominsectfossils)andhyenasprowledthebanksinsearchofcarrion.

WheredidWelsgettheidea?ThestandardSFwriter'sreplytothisquestionisthat`youmakeitup',butwehavesomefairlyspecificinformationinthiscase.Inaforewordtothe1932edition,Welssaysthathewasmotivatedby`studentdiscussionsinthelaboratoriesanddebatingsocietyoftheRoyalColegeofScienceintheeighties'.AccordingtoWels'sson,theideacamefromapaperonthefourthdimensionreadbyanotherstudent.Intheintroductiontothenovel,theTimeTraveler(heisnevernamed,butintheearlyversionheisDrNebo-gipfel,soperhapsit'sjustaswel)invokesthefourthdimensiontoexplainwhysuchamachineispossible:

`Butwaitamoment.Cananinstantaneouscubeexist?'`Don'tfolowyou,'

saidFilby.

`Canacubethatdoesnotlastforanytimeatal,havearealexistence?'

Filbybecamepensive.

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`Clearly,'theTimeTravelerproceeded,ànyrealbodymusthaveextensioninfourdirections:itmusthaveLength,Breadth,Thickness,and-

Duration...

..Therearerealyfourdimensions,threewhichwecalthethreeplanesofSpace,andafourth,Time.Thereis,however,atendencytodrawanunrealdistinctionbetweentheformerthreedimensionsandthelatter,becauseithappensthatourconsciousnessmovesintermittentlyinonedirectionalongthelatterfromthebeginningtotheendofourlives...

..Butsomephilosophicalpeoplehavebeenaskingwhythreedimensionsparticularly-whynotanotherdirectionatrightanglestothethree?-andhaveeventriedtoconstructaFour-Dimensionalgeometry.ProfessorSimonNewcombwasexpoundingthistotheNewYorkMathematicalSocietyonlyamonthorsoago.'

ThenotionoftimeasafourthdimensionwasbecomingcommonscientificcurrencyinthelateVictorianera.Themathematicianshadstartedit,bywonderingwhatadimensionwas,anddecidingthatitneednotbeadirectioninrealspace.Adimensionwasjustaquantitythatcouldbevaried,andthenumberofdimensionswasthelargestnumberofsuchquantitiesthatcouldalbevariedindependently.ThustheDiscworldthaum,thebasicparticleofmagic,isactualycomposedofresons,whichcomeinatleastfiveflavours:up,down,sideways,sexappeal,andpeppermint.Thethaumisthereforeatleastfive-dimensional,assumingthatupanddownareindependent,whichislikelybecauseit'squantum.

Inthe1700sthefoundlingmathematicianJeanleRondD'Alembert(hismiddlenameisthatofthechurchwherehewasabandonedasababy)suggestedthinkingoftimeasafourthdimensioninanarticleintheReasonedEncyclopaediaorDictionaryofSciences,Arts,andCrafts.

Anothermathematician,Joseph-LouisLagrange,usedtimeasafourthdimensioninhisAnalyticalMechanicsof1788,andhisTheoryofAnalyticFunctionsof1797explicitlystates:`Wemayregardmechanicsasageometryoffourdimensions.'

Ittookawhilefortheideatosinkin,butbyVictoriantimesmathematicianswereroutinelycombiningspaceandtimeintoasingleentity.Theydidn't(yet)

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calitspacetime,buttheycouldseethatithadfourdimensions:threeofspaceplusoneoftime.Journalistsandthelaypublicsoonbegantorefertotimeasthefourthdimension,becausetheycouldn'tthinkofanotherone,andtotalkasifscientistshadbeenlookingforitforagesandhadjustfoundit.Newcombwroteaboutthescienceoffour-dimensionalspacefrom1877,andspokeaboutittotheNewYorkMathematicalSocietyin1893.

Wels'smentionofNewcombsuggestsalinktooneofthemorecolourfulmembersofVictoriansociety,thewriterCharlesHowardHinton.Hinton'sprimaryclaimtofameishisenthusiasticpromotionof`the'fourthdimension.Hewasatalentedmathematicianwithagenuineflairforfour-dimensionalgeometry,andin1880hepublished`WhatistheFourthDimension?'intheDublinUniversityMagazine,whichwasreprintedintheCheltenhamLadies'Gazettea

yearlater.In1884itreappearedasapamphletwiththesubtitlèGhostsExplained'.Hinton,somethingofamystic,relatedthefourthdimensiontopseudoscientifictopicsrangingfromghoststotheafterlife.Aghostcaneasilyappearfrom,anddisappearalong,afourthdimension,forinstance,justasacoincanappearon,anddisappearfrom,atabletop,bymovingalong`the'thirddimension.

CharlesHintonwasinfluencedbytheunorthodoxviewsofhissurgeonfatherJames,acolaboratorofHavelockElis,whooutragedVictoriansocietywithhisstudiesofhumansexualbehaviour.Hintontheelderadvocatedfreeloveandpolygamy,andeventualyheadedacult.Hintontheyoungeralsohadaneventfulprivatelife:in1886hefledtoJapan,havingbeenconvictedofbigamyattheOldBailey.In1893heleftJapantobecomeamathematicsinstructoratPrincetonUniversity,whereheinventedabasebal-pitchingmachinethatusedgunpowdertopropelthebals,likeacannon.AfterseveralaccidentsthedevicewasabandonedandHintonlosthisjob,buthiscontinuingeffortstopromotethefourthdimensionweremoresuccessful.HewroteaboutitinpopularmagazineslikeHarper'sWeekly,McClure's,andScience.Hediedsuddenlyofacerebralhaemorrhagein1907,attheannualdinneroftheSocietyofPhilanthropicEnquiry,havingjustcompletedatoasttofemalephilosophers.

ItwasprobablyHintonwhoputWelsontothenarrativepossibilitiesoftimeasthefourthdimension.Theevidenceisindirectbutcompeling.

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NewcombdefinitelyknewHinton:heoncegotHintonajob.Wedon'tknowwhetherWelsevermetHinton,butthereiscircumstantialevidenceofacloseconnection.Forexample,theterm`scientificromance'wascoinedbyHintonintitlesofhiscolectedspeculativeessaysin1884and1886,andWelslaterusedthesamephrasetodescribehisownstories.

Moreover,WelswasaregularreaderofNature,whichreviewedHinton'sfirstseriesofScientificRomances(favourably)in1885andsummarisedsomeofhisideasonthefourthdimension.

Inallikelihood,HintonwasalsopartialyresponsibleforanotherVictoriantransdimensionalsaga,EdwinA.Abbott'sFlatlandof1884.ThetaleisaboutA.Square,wholivesintheEuclideanplane,atwodimensionalsocietyoftriangles,hexagonsandcircles,anddoesn'tbelieveinthethirddimensionuntilapassingspheredropshiminit.Byanalogy,Victorianswhodidn'tbelieveinthefourthdimensionwereequalyblinkered.AsubtextisasatireonVictoriantreatmentofwomenandthepoor.ManyofAbbott'singredientscloselyresembleelementsfoundinHinton'sstories.[1]

Mostofthephysicsoftimetravelisgeneralrelativity,withadashofquantummechanics.AsfarasthewizardsofUnseenUniversityareconcerned,althisstuffis`quantum'-auniversalintelectualgetout-of-jailcard-soyoucanuseittoexplainvirtualyanything,howeverbizarre.

Indeed,themorebizarre,thebetter.You'reabouttogetasoliddoseofquantuminChapter8.Herewe'lsetthingsupbyprovidingaquickprimeronEinstein'stheoriesofrelativity:specialandgeneral.

AsweexplainedinTheScienceofDiscworld,`relativity'isasilyname.Itshouldhavebeen'absolutivity'.Thewholepointofspecialrelativityisnotthatèverythingisrelative',butthatonething-thespeedoflight-isunexpectedlyabsolute.Shineatorchfromamovingcar,saysEinstein:theextraspeedofthecarwilhavenoeffectonthespeedofthelight.Thiscontrastsdramaticalywithold-fashionedNewtonianphysics,wherethelightfromamovingtorchwouldgofaster,acquiringthespeedofthecarinadditiontoitsowninherentspeed.Ifyouthrowabalfromamovingcar,that'swhathappens.Ifyouthrowlight,itshoulddothesame,butitdoesn't.

Despitetheshocktohumanintuition,experimentsshowthatRoundworldrealy

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doesbehaverelativisticaly.Wedon'tnoticebecausethedifferencebetweenNewtonianandEinsteinian

[1]SeeTheAnnotatedFlatlandbyEdwinA.AbbottandIanStewart(BasicBooks,2002).

physicsbecomesnoticeableonlywhenspeedsgetclosetothatoflight.

Specialrelativitywasinevitable;scientistswereboundtothinkofit.Itsseedswerealreadysownin1873whenJamesClerkMaxwelwrotedownhisequationsforelectromagnetism.Thoseequationsmakesenseinàmovingframe'-whenobservationsaremadebyamovingobserver-onlyifthespeedoflightisabsolute.Severalmathematicians,amongthemHenriPoincareandHermannMinkowski,realisedthisandanticipatedEinsteinonamathematicallevel,butitwasEinsteinwhofirsttooktheideasseriouslyasphysics.Ashepointedoutin1905,thephysicalconsequencesarebizarre.Objectsshrinkastheyapproachthespeedoflight,timeslowstoacrawl,andmassbecomesinfinite.Nothing(wel,nothing)cantravelfasterthanlight,andmasscanturnintoenergy.

In1908Minkowskifoundasimplewaytovisualiserelativisticphysics,nowcaledMinkowskispacetime.InNewtonianphysics,spacehasthreefixedcoordinates-left/right,front/back,up/down.Spaceandtimewerethoughttobeindependent.Butintherelativisticsetting,Minkowskitreatedtimeasanextracoordinateinitsownright.Afourthcoordinate,afourthindependentdirection...afourthdimension.Three-dimensionalspacebecamefour-dimensionalspacetime.ButMinkowski'streatmentoftimeaddedanewtwisttotheoldideaofD'AlembertandLagrange.Timecould,tosomeextent,beswappedwithspace.Time,likespace,becamegeometrical.

Wecanseethisintherelativistictreatmentofamovingparticle.InNewtonianphysics,theparticlesitsinspace,andastimepasses,itmovesaround.Newtonianphysicsviewsamovingparticlethewayweviewamovie.Relativity,though,viewsamovingparticleasthesequenceofstilframesthatmakeupthatmovie.Thislendsrelativityanexplicitairofdeterminism.Themovieframesalreadyexistbeforeyourunthemovie.

Past,presentandfuturearealreadythere.Astimeflows,andthemovieruns,wediscoverwhatfatehasinstoreforus-butfateisrealydestiny,inevitable,inescapable.Yes-themovieframescouldperhapscomeintoexistenceoneby

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one,withthenewestonebeingthepresent,butit'snotpossibletodothisconsistentlyforeveryobserver.

Relativisticspacetime=geometricnarrativium.

Geometricaly,amovingpointtracesoutacurve.Thinkoftheparticleasthepointofapencil,andspacetimeasasheetofpaper,withspacerunninghorizontalyandtimeverticaly.Asthepencilmoves,itleavesalinebehindonthepaper.So,asaparticlemoves,ittracesoutacurveinspacetimecaleditsworldline.Iftheparticlemovesataconstantspeed,theworldlineisstraight.Particlesthatmoveveryslowlycoverasmalamountofspaceinalotoftime,sotheirworldlinesareclosetothevertical;particlesthatmoveveryfastcoveralotofspaceinverylittletime,sotheirworldlinesarenearlyhorizontal.Inbetween,runningdiagonaly,aretheworldlinesofparticlesthatcoveragivenamountofspaceinthesameamountoftime-measuredintherightunits.Thoseunitsarechosentocorrespondviathespeedoflight-sayyearsfortimeandlight-yearsforspace.Whatcoversonelight-yearofspaceinoneyearoftime?Light,ofcourse.Sodiagonalworldlinescorrespondtoparticlesoflight-photons-

oranythingelsethatcanmoveatthesamespeed.

Relativityforbidsbodiesthatmovefasterthanlight.Theworldlinesthatcorrespondtosuchbodiesarecaledtimelikecurves,andthetimelikecurvespassingthroughagiveneventformacone,caledits`lightcone'.

Actualy,thisisliketwoconesstucktogetherattheirsharptips,onepointingforward,theotherbackward.Theforwardpointingconecontainsthefutureoftheevent,althepointsinspacetimethatitcouldpossiblyinfluence.Thebackward-pointingconecontainsitspast,theeventsthatcouldpossiblyinfluenceit.Everythingelseisforbiddenterritory,elsewheresandelsewhensthathavenopossiblecausalconnectionstothechosenevent.

Minkowskispacetimeissaidtobèflat'-itrepresentsthemotionofparticleswhennoforcesareactingonthem.Forceschangethemotion,andthemostimportantforceisgravity.Einsteininventedgeneralrelativityinordertoincorporategravityintospecialrelativity.InNewtonianphysics,gravityisaforce:itpulsparticlesawayfromthestraightlinesthattheywouldnaturalyfolowifnoforcewereacting.Ingeneralrelativity,gravityisageometricfeatureoftheuniverse-aformofspacetimecurvature.

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InMinkowskispacetime,pointsrepresentevents,whichhavealocationinbothspaceandtime.Thèdistance'betweentwoeventsmustcapturehowfaraparttheyareinspace,andhowfaraparttheyareintime.Itturnsoutthatthewaytodothisis,roughlyspeaking,totakethedistancebetweentheminspaceandsubtractthedistancebetweenthemintime.Thisquantityiscaledtheintervalbetweenthetwoevents.If,instead,youdidwhatseemsobviousandaddedthetime-distancetothespace-distance,thenspaceandtimewouldbeonexactlythesamephysicalfooting.

However,therearecleardifferences:freemotioninspaceiseasy,butfreemotionintimeisnot.Subtractingthetime-differencereflectsthisdistinction;mathematicalyitamountstoconsideringtimeasimaginaryspace-spacemultipliedbythesquarerootofminusone.Andithasaremarkableeffect:ifaparticletravelswiththespeedoflight,thentheintervalbetweenanytwoeventsalongitsworldlineiszero.

Thinkofaphoton,aparticleoflight.Ittravels,ofcourse,atthespeedoflight.Asoneyearoftimepasses,ittravelsonelight-year.Thesumof1

and1is2,butthat'snothowyougettheinterval.Theintervalisthedifference1-1,whichis0.Sotheintervalisrelatedtotheapparentrateofpassageoftimeforamovingobserver.Thefasteranobjectmoves,theslowertimeonitappearstopass.Thiseffectiscaledtimedilation.Asyoutravelcloserandclosertothespeedoflight,thepassageoftime,asyouexperienceit,slowsdown.Ifyoucouldtravelatthespeedoflight,timewouldbefrozen.Notimepassesonaphoton.

InNewtonianphysicsfparticlesthatmovewhennoforcesareactingfolowstraightlines.Straightlinesminimisethedistancebetweenpoints.Inrelativisticphysics,freelymovingparticlesminimisetheinterval,andfolowgeodesics.Finaly,gravityisincorporated,notasanextraforce,butasadistortionofthestructureofspacetime,whichchangesthesizeoftheintervalandalterstheshapesofgeodesics.Thisvariableintervalbetweennearbyeventsiscaledthemetricofspacetime.

Theusualimageistosaythatspacetimebecomes`curved',thoughthistermiseasilymisinterpreted.Inparticular,itdoesn'thavetobecurvedroundanythingelse.Thecurvatureisinterpretedphysicalyastheforceofgravity,anditcauseslightconestodeform.

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Oneresultis`gravitationallensing',thebendingoflightbymassiveobjects,whichEinsteindiscoveredin1911andpublishedin1915.HepredictedthatgravityshouldbendlightbytwicetheamountthatNewton'sLawsimply.In1919thispredictionwasconfirmed,whenSirArthurStanleyEddingtonledanexpeditiontoobserveatotaleclipseoftheSuninWestAfrica.AndrewCrommelinofGreenwichObservatoryledasecondexpeditiontoBrazil.TheexpeditionsobservedstarsneartheedgeoftheSunduringtheeclipse,whentheirlightwouldnotbeswampedbytheSun'smuchbrighterlight.Theyfoundslightdisplacementsofthestars'apparentpositions,consistentwithEinstein'spredictions.Overjoyed,Einsteinsenthismumapostcard:`DearMother,joyousnewstoday...theEnglishexpeditionshaveactualydemonstratedthedeflectionoflightfromtheSun.'theTimesrantheheadline:REVOLUTIONINSCIENCE.NEW

THEORYOFTHEUNIVERSE.NEWTONIANIDEASOVERTHROWN.

Halfwaydownthesecondcolumnwasasubheading:SPACÈWARPED'.

Einsteinbecameanovernightcelebrity.

Itwouldbechurlishtomentionthattomoderneyestheobservationaldataaredecidedlydodgy-theremightbesomebending,andthenagain,theremightnot.Sowewon't.Anyway,later,betterexperimentsconfirmedEinstein'sprediction.Somedistantquasarsproducemultipleimageswhenaninterveninggalaxyactslikealensandbendstheirlight,tocreateacosmicmirage.

Themetricofspacetimeisnotflat.

Instead,nearastar,spacetimetakestheformofacurvedsurfacethatbendstocreateacircular`valey'inwhichthestarsits.Lightfolowsgeodesicsacrossthesurface,andis`puleddown'intothehole,becausethatpathprovidesashortcut.Particlesmovinginspacetimeatsublightspeedsbehaveinthesameway;theynolongerfolowstraightlines,butaredeflectedtowardsthestar,whencetheNewtonianpictureofagravitationalforce.

Farfromthestar,thisspacetimeisverycloseindeedtoMinkowskispacetime;thatis,thegravitationaleffectfalsoffrapidlyandsoonbecomesnegligible.SpacetimesthatlooklikeMinkowskispacetimeatlargedistancesaresaidtobeàsymptoticalyflat'.Rememberthatterm:it'simportantformakingtimemachines.Mostofourownuniverseisasymptoticalyflat,becausemassive

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bodiessuchasstarsarescatteredverythinly.

Whensettingupaspacetime,youcan'tjustbendthingsanywayyoulike.

ThemetricmustobeytheEinsteinequations,whichrelatethemotionoffreelymovingparticlestothedegreeofdistortionawayfromflatspacetime.

We'vesaidalotabouthowspaceandtimebehave,butwhatarethey?Tobehonest,wehaven'taclue.Theonethingwe'resureofisthatappearancescanbedeceptive.

Tick.

Somephysiciststakethatprincipletoextremes.JulianBarbour,inTheEndofTime,arguesthatfromaquantum-mechanicalpointofview,timedoesnotexist.

In1999,writinginNewScientist,heexplainedtheidearoughlythisway.Atanyinstant,thestateofeveryparticleintheentireuniversecanberepresentedbyasinglepointinagiganticphasespace,whichhecalsPlatonia.BarbourandhiscoleagueBrunoBertottifoundouthowtomakeconventionalphysicsworkinPlatonia.Astimepasses,theconfigurationofalparticlesintheuniverseisrepresentedinPlatoniaasamovingpoint,soittracesoutapath,justlikearelativisticworldline.APlatoniandeitycouldbringthepointsofthatpathintoexistencesequentialy,andtheparticleswouldmove,andtimewouldseemtoflow.

QuantumPlatonia,however,isamuchstrangerplace.Here,'quantummechanicskilstime',asBarbourputsit.Aquantumparticleisnotapoint,butafuzzyprobabilitycloud.AquantumstateoftheuniverseisafuzzycloudinPlatonia.Thèsize'ofthatcloud,relativetothatofPlatoniaitself,representstheprobabilitythattheuniverseisinoneofthestatesthatcomprisethecloud.SowehavetoendowPlatoniawithàprobabilitymist',whosedensityinanygivenregiondetermineshowprobableitisforacloudtooccupythatregion.

But,saysBarbour,`therecannotbeprobabilitiesatdifferenttimes,becausePlatoniaitselfistimeless.Therecanonlybeonce-and-foralprobabilitiesforeachpossibleconfiguration.'Thereisonlyoneprobabilitymist,anditisalwaysthesame.Inthisset-up,timeisanilusion.Thefutureisnotdeterminedbythepresent-notbecauseoftheroleofchance,butbecausethereisnosuchthingasfutureorpresent.

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Byanalogy,thinkofthechildhoodgameofsnakesandladders.Ateachrolofthedice,playersmovetheircountersfromsquaretosquareonaboard;traditionalythereareahundredsquares.Somearelinkedbyladders,andifyoulandatthebottomyouimmediatelyrisetothetop;othersarelinkedbysnakes,andifyoulandatthetopyouimmediatelyfaltothebottom.Whoeverreachesthefinalsquarefirstwins.

Tosimplifythedescription,imaginesomeoneplayingsolosnakesandladders,sothatthereisonlyonecounterontheboard.Thenatanyinstant,thèstate'ofthegameisdeterminedbyasinglesquare:whicheveroneiscurrentlyoccupiedbythecounter.Inthisanalogy,theboarditselfbecomesthephasespace,ouranalogueofPlatonia.

Thecounterrepresentstheentireuniverse.Asthecounterhopsaround,accordingtotherulesofthegame,thestateoftheùniverse'changes.Thepaththatthecounterfolows-thelistofsquaresthatitsuccessivelyoccupies-isanalogoustotheworldlineoftheuniverse.Inthisinterpretation,timedoesexist,becauseeachsuccessivemoveofthecountercorrespondstoonetickofthecosmicclock.

Quantumsnakesandladdersisverydifferent.Theboardisthesame,butnowalthatmattersistheprobabilitywithwhichthecounteroccupiesanygivensquare-notjustatonestageofthegame,butoveral.Forinstance,theprobabilityofbeingonthefirstsquare,atsomestageinthegame,is1,becauseyoualwaysstartthere.Theprobabilityofbeingonthesecondsquareis1/6,becausetheonlywaytogetthereistothrowa1withthediceonyourfirstthrow.Andsoon.Oncewehavecalculatedaltheseprobabilities,wecanforgetabouttherulesofthegameandtheconceptofàmove'.Nowonlytheprobabilitiesremain.Thisisthequantumversionofthegame,andithasnoexplicitmoves,onlyprobabilities.Sincetherearenomoves,thereisnonotionofthènext'move,andnosensibleconceptoftime.

Ouruniverse,Barbourtelsus,isaquantumone,soitislikequantumsnakesandladders,and`time'isameaninglessconcept.Sowhydowenaivehumansimaginethattimeflows;thattheuniverse(atleast,thebitnearus)passesthroughalinearsequenceofchanges?

ToBarbour,theapparentflowoftimeisanilusion.HesuggeststhatPlatonianconfigurationswhichhavehighprobabilitymustcontainwithinthemàn

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appearanceofhistory'.Theywillookasthoughtheyhadapast.

It'sabitlikethephilosophers'oldchestnut:maybetheuniverseisbeingcreatedaneweveryinstant(asinThiefofTime),butateachmoment,itiscreatedalongwithapparentrecordsofalengthypasthistory.SuchapparentlyhistoricalcloudsinPlatoniaarecaledtimecapsules.Now,amongthosehigh-probabilityconfigurationswefindthearrangementofneuronsinaconsciousbrain.Inotherwords,theuniverseitselfistimeless,butourbrainsaretimecapsules,high-probabilityconfigurations,andtheseautomaticalycomealongwiththeilusionthattheyhavehadapasthistory.

It'saneatidea,ifyoulikethatsortofthing.ButithingesonBarbour'sclaimthatPlatoniamustbetimelessbecausètherecanonlybeonce-and-for-alprobabilitiesforeachpossibleconfiguration'.ThisstatementisremarkablyreminiscentofoneofXeno's-sorry,Zeno's-paradoxes:theArrow.Which,yourecal,saysthatateachinstantanarrowhasaspecificlocation,soitcan'tbemoving.Analogously,Barbourtelsusthatateachinstant(ifsuchathingcouldexist)Platoniamusthaveaspecificprobabilitymist,anddeducesthatthismistcan'tchange(soitdoesn't).

WhatwehaveinmindasanalternativetoBarbour'stimelessprobabilitymistisnotamistthatchangesastimepasses,however.Thatwouldfalfoulofthenon-Newtonianrelationbetweenspaceandtime;differentpartsofthemistwouldcorrespondtodifferenttimesdependingonwhoobservedthem.No,we'rethinkingofthemathematicalresolutionoftheArrowparadox,viaHamiltonianmechanics.Here,thestateofabodyisgivenbytwoquantities,positionandmomentum,insteadofjustposition.

Momentumisàhiddenvariable',observableonlythroughitseffectonsubsequentpositions,whereaspositionissomethingwecanobservedirectly.Wesaid:àbodyinagivenpositionwithzeromomentumisnotmovingatthatinstant,whereasoneinthesamepositionwithnon-zeromomentumismoving,eventhoughinstantaneouslyitstaysinthesameplace'.Momentumencodesthenextchangeofposition,anditencodesitnow.Itsvaluenowisnotobservablenow,butitis(wilbe)observable.Youjusthavetowaittofindoutwhatitwas.Momentumisàhiddenvariable'

thatencodestransitionsfromonepositiontoanother.

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Canwefindananalogueofmomentuminquantumsnakesandladders?

Yes,wecan.Itistheoveralprobabilityofgoingfromanygivensquaretoanyother.Thesètransitionprobabilities'dependonlyonthesquaresconcerned,notonthetimeatwhichthemoveismade,soinBarbour'ssensetheyarètimeless'.Butwhenyouareonsomegivensquare,thetransitionprobabilitiestelyouwhereyournextmovecanlead,soyoucanreconstructthepossiblesequencesofmoves,therebyputtingtimebackintothephysics.

Forexactlythesamereason,asinglefixedprobabilitymistisnottheonlystatisticalstructurewithwhichPlatoniacanbeendowed.Platoniacanalsobeequippedwithtransitionprobabilitiesbetweenpairsofstates.TheresultistoconvertPlatoniaintowhatstatisticianscalàMarkovchain',whichisjustlikethelistoftransitionprobabilitiesforsnakesandladders,butmoregeneral.IfPlatoniaismadeintoaMarkovchain,eachsequenceofconfigurationsgetsitsownprobability.Themostprobablesequencesarethosethatcontainlargenumbersofhighlyprobablestates-theselookoddlylikeBarbour'stimecapsules.Soinsteadofsingle-statePlatoniawegetsequentialstateMarkovia,wheretheuniversemakestransitionsthroughwholesequencesofconfigurations,andthemostlikelytransitionsaretheonesthatprovideacoherenthistory-narrativium.

ThisMarkovianapproachofferstheprospectofbringingtimebackintoexistenceinaPlatonianuniverse.Infact,it'sverysimilartohowSusanStoHelitandRonnieSoakmanagedtooperateinthecracksbetweentheinstants,inThiefofTime.

Tick.

SEVEN

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THEFISHISOFF

TwoHOURSLATERASINGLEsheetofpaperslidoffHex'swritingtable.

Ponderpickeditup.

`ThereareabouttenpointswherewemustintervenetoensurethatTheOriginiswritten,'hesaid.

'wel,thatdoesn'tseemtoobad,'saidRidculy.`WegotShakespeareborn,didn'twe?[1]Wejusthavetotinker.'

`Theselookalittlemorecomplicated,'saidPonder,doubtfuly.

`ButHexcanmoveusaround,'saidRidculy.Ìtcouldbefun,especialyifsomethingorsomeoneisplayinglesbuggeursrisibles.Itcouldbeeducational,MrStibbons.'

Àndtheydorealygoodbeer,`saidtheDean.Àndthefoodwasexcelent.Rememberthatgoosewehadlasttime?I'veseldomeatenbetter.'

`Wewilbesettingouttosavetheworld,'saidRidculy,severely.`Wewilhaveotherthingsonourminds!'

`Buttherewilbemealtimes,yes?'saidtheDeanSecondLunchandMid-afternoonSnackwentpastalmostunnoticed.

Perhapsthewizardswerealreadyleavingspaceforgoose...

[1]Yes,theydid-inTheScienceofDiscworldI.

Itwasturningouttobealongday.EaselshadbeensetuparoundHex.

Paperwasstrewnacrosseverytable.TheLibrarianhadpracticalybuiltupabranchlibraryinonecorner,andwasstilfetchingbooksfromthedistantreachesofL-Space.

Andthewizardshadchangedtheirclothes,readyforhands-onintervention.Therehadbarelybeenadiscussionaboutit,notaftertheDeanhadmentioned

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thegoose.HexhadagreatdealofcontrolovertheGlobe,butwhenitcametothefinedetailyouneededtobehands-on,especialyhandsoncutlery.Hexhadnohands.Besides,he'dexplainedatlength,therewasnosuchthingasabsolutecontrol,notinafulyfunctioninguniverse.Therewasjustavariableamountoflackofcontrol.Infact,Ponderthought,HexwasaGreatBigThingasfarasRoundworldwasconcerned.Almost...godlike.Buthestilcouldn'tcontroleverything.Evenifyouknewwhereeverytinyspinningparticleofstuffwas,youcouldn'tknowwhatit'ddonext.

Thewizardswouldhavetogoin.Theycoulddothat.They'ddoneitbefore.

Notroubleistoomuchifitsavessomeexcelentchefsfromextinction.

Clothing,atleast,wouldnotbeaproblem.Giveortaketheoddpointyhatandstaff,thewizardswouldbeabletowalktheRoundworldstreetswithoutattractingasecondglance.

`Howdowelook?'saidtheArchchancelor,astheyreassembled.

`Very...Victorian,'saidPonder.Àlthoughtechnicaly,atthemoment,veryGeorgian.Very...tweedy,anyway.Areyoutotalyhappywiththebishoplook,Dean?'

Ìsn'tthatappropriateforthetime?'saidtheDean,lookingworried.`WelookedthroughthebookoncostumesandIthought...'Hisvoicetrailedoff.

Ìt'sthemitre,isn'tit...'

Àndthecrozier,'saidPonder.

'Iwantedtofitin,yousee.'

Ìnacathedral,yes..I'mafraidit'splainblacksuitwithgaitersforstreetwear.However,youcandoanythingyoulikewithyourbeardandyoucanwearhatsasmalchildcouldstandupinside.Butonthestreets,bishopsarequitedul.'

`Where'sthefuninthat?'saidtheDean,sulkily.

PonderturnedtoRincewind.

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Àsforyou,Rincewind,canIaskwhyyouarewearingnothingbutaloinclothandapointyhat?

'Ah,wel,yousee,ifyoudon'tknowwhatyou'regettinginto,nakedalwaysworks,'saidRincewind.Ìt'stheal-purposesuit.Athomeineveryculture.

Admittedlyyousometimesget-'

Ìntweed,thatman!'barkedRidculy.Àndnopointyhat!'AgainstabackgroundofgrumblingheturnedthentotheLibrarian.Àndasforyou,sir...asuittoo.Andastovepipehat.Youneedtheheight!'

'Ook!'saidtheLibrarian.

ÌamtheArchchancelor,sir!Iinsist!Andafalsebeard,Ithink.Falseeyebrows,too.LetMrDarwinbeyourmodelhere!TheseVictorianswereverycivilisedpeople!Haireverywhere!Keeptheknucklingtoaminimumandthey'lmakeyouPrimeMinister!Verywel,gentlemen.Backhereinhalfanhour!

Thewizardsassembled.Acircleofwhitelightappearedonthefloor.Theysteppedinside,therewasachangeinthesoundsmadebyHex,andtheyvanished.

Theylandedknee-deepinthemireofapeatbog,causingbubblesoffoulairtoburstaroundthem.

`MrStibbons!'Ridculybelowed.

`Sorry,sir,sorry,'saidPonderquickly.`Hex,raiseusbytwofeet,please.'

`Yes,butwe'restilsoaked,'grumbledtheDean,astheyfloatedupintheair.`Youseemtohave,ah,"muckedup",MrStibbons!''No,sir,IwantedtoshowyouaCharlesDarwininthewild,'saidPonder.'Herehecomesnow...

Alargeandenergeticyoungmanboundedoutoftheweedsandwenttoclearablackpoolwithavaultingpole.Thepoleimmediatelysankone-thirdofitslengthintothesuckinggroundanditsathleticownersailedoffintothemud.Hecameupholdingasmalwaterplant.Obliviousofthenoisomebubblingaroundhim,hewavedtheplanttriumphantlyatsomedistantcompanions,puledhispoleoutofthepeatwithsomeeffort,andsplashedaway.

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`Didheseeus?'saidRincewind.

`No,notyet.That'syoungDarwin,'saidPonder.`Verykeenoncolectingalsortsofwildlife.ColectingwasenormouspopularamongtheEnglishofthiscentury.Bones,shels,butterflies,birds,otherpeople'scountries...alsortsofthings.'

`Manaftermyownheart!'saidRidculy,cheerfuly.ÌhadthebestpressedlizardcolectioneverwhenIwasthatage!'

`Can'tseeabeagleanywhere,though,'saidRincewind,gloomily.Hegotedgyintheabsenceofhishat,andtriedtostandunderthings.

TheChairofIndefiniteStudieslookedupfromthethaumometerinhishand.

`Nomagicdisturbance,nonothing,'hesaid,lookingaroundatthemarshes.ÌsHexsure?Theonlystrangethinghereisus.'

`Let'sgetstarted,shalwe?'saidRidculy.`Wheretonext?'`Hex,moveustoLondon,wilyou?'saidPonder.`Location7.'Thewizardsdidn'tapparentlymove,butthelandscapearoundthemwaveredandchanged.

Itbecameanaleyway.Therewerealotofstreetnoisesnearby.Ì'msureyoualreadthebriefingIpreparedthismorning.'saidPonder,brightly.

ÀreyoualsosurewerenotbackinAnkh-Morpork?'saidRidculyloudly.

Ì'dswearIcansmeltheriver!'

Àh,thenperhapsI'dbetterjustremindyouoftheimportantpoints,'saidPonderwearily.`ThelistofmajorthingsthatmightimpedeDarwin'sprogress-'

Ìrememberaboutthegiantsquid,'Rincewindvolunteered.

`Hexcanhandlethegiantsquid,'saidPonder.

Òh,shame.Iwaslookingforwardtothat,'saidRidculy.

`No,sir,'saidPonder,aspatientlyaspossible.`Wehavetodealwithpeople.Remember?Weagreedlasttimeit'snotethicaltoleavethattoHex.Remembertherainoffatwomen?[1]

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`Thatneveractualyhappened,'saidtheLecturerinRecentRunes,wistfuly.

`Quiteso,'saidRidculy,firmly.Àndjustaswel.Leadon,MrStibbons.'

`Somuchtodo,somuchtodo,'mutteredPonder,leafingthroughthepaperwork.Ìsupposewe'dbetterdothingsinorder...sofirst,wemustseethatMrHabbakukSouser'scookthrowsawaythefish.'

Itwasasculeryboywhoopenedthebackdoor,inastreetofquiteprosperous-lookinghouses.PonderStibbonsraisedhisverytalhat.

`Wewishtosee-'heconsultedtheclipboard`-MrsBoddy,'hesaid.`Sheisthecookhere,Ibelieve?TelherwearetheCommitteeforPublicSanitation,andthematterisurgent,solooksharpaboutit!'

Ìhopeyouknowwhatyou'redoing,Stibbons,'hissedRidculyastheboyscurriedaway.

`Totaly,Archchancelor.Hexsaysthelineofcausalityis-ah,MrsBoddy?'

Thiswastoaskinny,worriedwomanwhowasadvancingonthemfromthediminterior,wipingherhandsonherapron.

'Iam,sir,'saidthecook.`TheboysaidyougentlemenwasHygienic?'

`MrsBoddy,youhadsomefishdeliveredthismorning?'saidPonder,sternly.

[1]AraremeteorologicalphenomenondiscussedbrieflyinTheScienceofDiscworldÌYessir.Nicepieceo'hake.'Suddenuncertaintyseizedherfeatures.Èr...

thatwasalright,wasn'tit?

'Alasitwasnot,MrsBoddy!'saidPonder.`Wehavejustcomefromthefishmonger.Alhishakeiscompletelyoff.Wehavehadmanycomplaints.

Someofthemwerefromnextofkin,MrsBoddy!'

Òh,whatshalwedotobesaved!'thecookburstout.Ì'vegotitcookin'!Itsmeledalright,sir!'

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`Thankfuly,then,thereisnoharmdone,'saidPonder.`ShalIgiveittothecat?

'Doyoulikethecat?'saidPonder.`No,wrapitinsomepaperandbringitouttousrightnow!I'msureMrSouserwilunderstandwhenyougivehimsomeofthecoldhamfromyesterday.'

`Yessir!'Thecookscurriedaway,andreturnedshortlywithaparcelofveryhot,verydampfish.PondergrabbeditfromherandthrustitintoRincewind'sarms.

`Scourthepanthoroughly,MrsBoddy!'saidPonder,asRincewindtriedtojugglehake.`Gentlemen,wemusthurry!'

Hestartedtowalkveryfasttowardstheendofthestreet,thewizardsjoggingalongbehindhim,andturnedsharplyintoanaleywayjustaheadofashoutof`Sir?Sir?Howdidyouknowaboutthecoldham?'

`Location9,Hex,'saidPonder.Àndremovethefish,please!'

`Wasalthatabout?'saidRidculy.`Whydidwetakethatpoorwoman'sfish?'

Rincewindsaidòw!'asthefishdisappeared.

`MrSouserwiltravel,er,tomorrowtomeetsomebusinessmen,'saidPonder,asacircleformedonthegroundaroundthewizards.ÒneofthemwilbeamancaledJosiahWedgwood,afamousindustrialist.MrSouserwiltelhimabouthissonJames,whoiscurrentlyworkingwiththeNavy.Ithasmadeamanofhim,MrSouserwilsay.MrWedgwoodwillistenwithinterest,andformtheopinionthattheadventureofalongseavoyageinrespectablecompanymaywelbeofbenefittoayoungmanonthevergeofadultlife.Atleast,hewilnow.IfMrSouserhadeatenthatfish,hewouldhavebeentooiltotraveltomorrow.'

`Wel,that'sgoodnewsforMrSouser,butwhat'sitgottodowithus?'saidtheDean.

'MrWedgwoodisCharlesDarwin'suncle,'saidPonder,astheairwavered.`Hewilhaveaninfluenceonhisnephew'scareer.Andnowforournextcal...'

`Goodmorning!MrsNightingale?'

`Yes?'saidthewoman,asifshewasnowdoubtingit.Shetookinthegroupof

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peopleinfrontofher,hereyerestingontheverybeardedonewhoseknucklestouchedtheground.Besideher,thehousemaidwho'dopenedthedoorlookedonnervously.

`MynameisMrStibbons,MrsNightingale.IamthesecretaryofTheMissiontoDeepSeaVoyagers,acharitableorganisation.IbelieveMrNightingaleisshortlytoembarkonaperilousmissiontothestorm-tossed,current-mazed,ship-eatinggiant-squidinfestedwatersoftheSouthAmericas?'

Thewoman'sgazetoreitselfawayfromtheLibrarianandhereyesnarrowed.

`Heneversaidanythingtomeaboutgiantsquid,'shesaid.

Ìndeed?I'mverysorrytohearthat,MrsNightingale.BrotherBookmeisterhere,'PonderpattedtheLibrarianontheshoulder,`wouldtelyouaboutthemhimselfwereitnotthatthedireexperiencequiterobbedhimofthepowerofspeech.'

'Ook!'saidBrotherBookmeisterplaintively.

`Realy?'saidthewoman,settingherjawfirmly.`Wouldyougentlemencaretostepintotheparlour?'

`Wel,thebiscuitswerenice,'saidtheDean,asthewizardsstroledoutintothestreethalfanhourlater.Àndnow,Stibbons,wouldyoucaretoteluswhatalthatwasabout?'

`Gladly,Dean,andmayIsayyourstoryabouttheseasnakewasveryuseful?'saidPonder.`ButRincewind,thattaleaboutthekilerflyingfishwasratheroverthetop,Ithought.'

Ìdidn'tmakeitup!'Rincewindsaid.`Theyhadteethonthemlike-'

`Wel,anyway...DarwinwasthesecondchoiceforthepostontheBeagle,'

saidPonder.'MrNightingalewasthecaptain'sinitialchoice.Historywilrecordthatafterhiswife'spleadinghedeclinedtheoffer.Thishewildowithinaboutfiveminutesofwhenhegetshometonight.'

Ànotherfineruse?'saidRidculy.

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Ì'mratherpleasedwithit,asamatteroffact,'saidPonder.

'Hmm,'saidRidculy.Cunninginyoungerwizardsisnotautomaticalyapplaudedintheirelders.`Veryclever,Stibbons.Youareawizardtowatch.'

`Thankyou,sir.Mynextquestionis:doesanyonehereknowanythingaboutshipbuilding?Wel,perhapsthatwon'tbenecessary.Hex,takeustoPortsmouth,please.TheBeagleisbeingrefitted.Youwilneedtobenavalinspectorswhich,ahaha,I'msureyou'lbegoodat.Infactyouwilbethemostobservantinspectorstherehaveeverbeen.Location3,please,Hex.'

EIGHT

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FORWARDTOTHEPAST

WELL,THEWIZARDSHAVEMADEagoodstart.AndwiththemightofHexbehindthem,thewizardscantravelatwilalongtheRoundworldtimeline.We'rehappyforthemtodothat,inafictionalcontext-butcouldwedothesamething,inafactualone?

Toanswerthat,wemustdecidewhatatimemachinelookslikewithintheframeworkofgeneralrelativity.Thenwecantalkaboutbuildingone.

Travelintothefutureiseasy:wait.It'sgettingbackthat'shard.Atimemachineletsaparticleorobjectreturntoitsownpast,soitsworldline,atimelikecurve,mustcloseintoaloop.Soatimemachineisjustaclosedtimelikecurve,abbreviatedtoCTC.Insteadofasking,Ìstimetravelpossible?'weask,`CanCTCsexist?'

InflatMinkowskispacetime,theycan't.Forwardandbackwardlightcones-thefutureandpastofanevent-neverintersect(exceptatthepointitself,whichwediscount).Ifyouheadoffacrossaflatplane,neverdeviatingmorethan45°fromduenorth,youcanneversneakuponyourselffromthesouth.

Butforwardandbackwardlightconescanintersectinothertypesofspacetime.ThefirstpersontonoticethiswasKurtGodel,betterknownforhisfundamentalworkinmathematicallogic.In1949heworkedouttherelativisticmathematicsofarotatinguniverse,anddiscoveredthatthepastandfutureofeverypointintersect.Startwhereverandwheneveryoulike,travelintoyourfuture,andyou'lendupinyourownpast.However,observationsindicatethattheuniverseisnotrotating,andspinningupastationaryuniverse(especialyfrominside)doesn'tlooklikeaplausiblewaytomakeatimemachine.Though,ifthewizardsweretogiveRoundworldatwirl...

ThesimplestexampleoffuturemeetingpastarisesifyoutakeMinkowskispacetimeandrolitupalongthèvertical'timedirectiontoformacylinder.

Thenthetimecoordinatebecomescyclic,asinHindumythology,whereBrahmarecreatestheuniverseeverykalpa,aperiodof4.32bilionyears.

Althoughacylinderlookscurved,thecorrespondingspacetimeisnotactualy

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curved-notinthegravitationalsense.Whenyourolupasheetofpaperintoacylinder,itdoesn'tdistort.Youcanflattenitoutagainandthepaperisnotfoldedorwrinkled.Anantthatisconfinedpurelytothesurfacewon'tnoticethatspacetimehasbeenbent,becausedistancesonthesurfacehaven'tchanged.Inshortthelocalmetricdoesn'tchange.Whatchangesistheglobalgeometryofspacetime,itsoveraltopology.

RolingupMinkowskispacetimeisanexampleofapowerfulmathematicaltrickforbuildingnewspacetimesoutofoldones:cut-and-paste.Ifyoucancutpiecesoutofknownspacetimes,andgluethemtogetherwithoutdistortingtheirmetrics,thentheresultisalsoapossiblespacetime.Wesay`distortingthemetric'ratherthan`bending',forexactlythereasonthatwesaythatroled-upMinkowskispacetimeisnotcurved.We'retalkingaboutintrinsiccurvature,asexperiencedbyacreaturethatlivesinthespacetime,notaboutapparentcurvatureasseenbysomeexternalviewer.

Theroled-upversionofMinkowskispacetimeisaverysimplewaytoprovethatspacetimesthatobeytheEinsteinequationscanpossessCTCs-andthusthattimetravelisnotinconsistentwithcurrentlyknownphysics.Butthatdoesn'timplythattimetravelispossible.Thereisaveryimportantdistinctionbetweenwhatismathematicalypossibleandwhatisphysicalyfeasible.

AspacetimeismathematicalypossibleifitobeystheEinsteinequations.

Itisphysicalyfeasibleifitcanexist,orcouldbecreated,aspartofourownuniverseoranadd-on.There'snoverygoodreasontosupposethatroled-upMinkowskispacetimeisphysicalyfeasible:certainlyitwouldbehardtorefashiontheuniverseinthatformifitwasn'talreadyendowedwithcyclictime,andrightnowveryfewpeople(otherthanHindus)thinkthatitis.ThesearchforspacetimesthatpossessCTCsandhaveplausiblephysicsisasearchformoreplausibletopologies.Therearemanymathematicalypossibletopologies,but,aswiththeIrishmangivingdirections,youcan'tgettoalofthemfromhere.

However,youcangettosomeremarkablyinterestingones.Alyouneedisblackholeengineering.Oh,andwhiteholes,too.Andnegativeenergy.

And-

Onestepatatime.Blackholesfirst.TheywerefirstpredictedinclassicalNewtonianmechanics,wherethereisnolimittothespeedofamovingobject.

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Particlescanescapefromanattractingmass,howeverstrongitsgravitationalfield,bymovingfasterthantheappropriateèscapevelocity'.

FortheEarth,thisis7milespersecond(11kps),andfortheSun,itis26

milespersecond(41kps).InanarticlepresentedtotheRoyalSocietyin1783,JohnMichelobservedthattheconceptofescapevelocity,combinedwithafinitespeedoflight,impliesthatsufficientlymassiveobjectscannotemitlightatal-becausethespeedoflightwilbelowerthantheescapevelocity.In1796PierreSimondeLaplacerepeatedtheseobservationsinhisExpositionoftheSystemoftheWorld.Bothofthemimaginedthattheuniversemightbelitteredwithhugebodies,biggerthanstars,buttotalydark.

Theywereacenturyaheadoftheirtime.

In1915KarlSchwarzschildtookthefirststeptowardsansweringtherelativisticversionofthesamequestion,whenhesolvedtheEinsteinequationsforthegravitationalfieldaroundamassivesphereinavacuum.

Hissolutionbehavedverystrangelyatacriticaldistancefromthecentreofthesphere,nowcaledtheSchwarzschildradius.Itisequaltothemassofthestar,multipliedbythesquareofthespeedoflight,multipliedbytwicethegravitationalconstant,ifyoumustknow.

TheSchwarzschildradiusfortheSunis1.2miles(2km),andfortheEarth0.4inches(1cm)-bothburiedinaccessiblydeepwheretheycan'tcausetrouble.Soitwasn'tentirelyclearhowsignificantthestrangemathematicalbehaviourwas...orevenwhatitmeant.

WhatwouldhappentoastarthatissodensethatitliesinsideitsownSchwarzschildradius?

In1939RobertOppenheimerandHartlandSnydershowedthatitwouldcolapseunderitsowngravitationalattraction.Indeedawholeportionofspacetimewouldcolapsetoformaregionfromwhichnomatter,notevenlight,couldescape.Thiswasthebirthofanexcitingnewphysicalconcept.

In1967JohnArchibaldWheelercoinedthetermblackhole,andthenewconceptwaschristened.

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Howdoesablackholedevelopastimepasses?AninitialclumpofmattershrinkstotheSchwarzschildradius,andthencontinuestoshrinkuntil,afterafinitetime,althemasshascolapsedtoasinglepoint,caledasingularity.Fromoutside,though,wecan'tobservethesingularity:itliesbeyondtheèventhorizon'attheSchwarzschildradius,whichseparatestheobservableregion,fromwhichlightcanescape,andtheunobservableregionwherethelightistrapped.

Ifyouweretowatchablackholecolapsefromoutside,youwouldseethestarshrinkingtowardstheSchwarzschildradius,butyou'dneverseeitgetthere.Asitshrinks,itsspeedofcolapseasseenfromoutsideapproachesthatoflight,andrelativistictimedilationimpliesthattheentirecolapsetakesinfinitelylongwhenseenbyanoutsideobserver.Thelightfromthestarwouldshiftdeeperanddeeperintotheredendofthespectrum.Thenameshouldbèredhole'.

Blackholesareidealforspacetimeengineering.Youcancut-andpasteablackholeintoanyuniversethathasasymptoticalyflatregions,suchasourown.[1]Thismakesblackholetopologyphysicalyplausibleinouruniverse.Indeed,thescenarioofgravitationalcolapsemakesitevenmoreplausible:youjusthavetostartwithabigenoughconcentrationofmatter,suchasaneutronstarorthecentreofagalaxy.Atechnologicalyadvancedsocietycouldbuildblackholes.

Ablackholedoesn'tpossessCTCs,though,sowehaven'tachievedtimetravel.Yet.However,we'regettingclose.Thenextstepusesthetime-reversibilityofEinstein'sequations:toeverysolutiontherecorrespondsanotherthatisjustthesame,exceptthattimerunsbackwards.Thetimereversalofablackholeiscaledawhitehole.Ablackhole'seventhorizonisabarrierfromwhichnoparticlecanescape;awhitehole'seventhorizonisoneintowhichnoparticlecanfal,butfromwhichparticlesmayemergeatanymoment.So,seenfromtheoutside,awhiteholewouldappearasthesuddenexplosionofastar'sworthofmatter,comingfromatime-reversedeventhorizon.

Whiteholesmayseemratherstrange.Itmakessenseforaninitialconcentrationofmattertocolapse,ifitisdenseenough,andthustoformablackhole;butwhyshouldthesingularityinsideawhiteholesuddenlydecidetospewforthastar,havingremainedunchangedsincethedawnoftime?Perhapsbecausetimerunsbackwardsinsideawhitehole,socausalityrunsfromfuturetopast?Let'sjustagreethatwhiteholesareamathematicalpossibility,andnoticethattheytooareasymptoticalyflat.Soifyouknewhowtomakeone,youcouldglueit

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neatlyintoyourownuniverse,too.

Notonlythat:youcanglueablackholeandawhiteholetogether.Cutthemalongtheireventhorizons,andpastealongthesetwohorizons.Theresultisasortoftube.Mattercanpassthroughthetube[1]Thisisamathematician'swayofsayingthatyoucanputablackholeanywhereyouwant.(Or,likeagorilainaMini,itcangoanywhereitwants.)

inonedirectiononly:intotheblackholeandoutofthewhite.It'sakindofmatter-valve.Thepassagethroughthevalvefolowsatimelikecurve,becausematerialparticlescanindeedtraverseit.

Bothendsofthetubecanbegluedintoanyasymptoticalyflatregionofanyspacetime.Youcouldglueoneendintoouruniverse,andtheotherendintosomebodyelse's;oryoucouldgluebothendsintoours-

anywhereyoulikeexceptnearaconcentrationofmatter.Nowyou'vegotawormhole.Thedistancethroughthewormholeisveryshort,whereasthatbetweenthetwoopenings,acrossnormalspacetime,canbeasbigasyoulike.

Awormholeisashortcutthroughtheuniverse.Butthat'smatter-transmission,nottimetravel.Nevermind:we'renearlythere.

Thekeytowormholetimetravelisthenotorioustwinparadox,pointedoutbythephysicistPaulLangevinin1911.Recalthatinrelativity,timepassesmoreslowlythefasteryougo,andstopsaltogetheratthespeedoflight.

Thiseffectisknownastimedilation.WequotefromTheScienceofDiscworld:

SupposethatRosencrantzandGuildenstemarebornonEarthonthesameday.Rosencrantzstaystherealhislife,whileGuildenstemtravelsawayatnearlylightspeed,andthenturnsroundandcomeshomeagain.

Becauseoftimedilation,onlyoneyear(say)haspassedforGuildenstern,whereas40yearshavegonebyforRosencrantz.SoGuildensternisnow39yearsyoungerthanhistwinbrother.

It'scaledaparadoxbecausethereseemstobeapuzzle:fromGuildenstern'sframeofreference,itisRosencrantzwhohaswhizzedoffatnear-lightspeed.Surely,bythesametoken,Rosencrantzshouldbe39

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yearsyounger,notGuildenstern?Buttheapparentsymmetryisfalacious.

Guildenstern'sframeofreferenceissubjecttoaccelerationanddeceleration,especialywhenheturnsroundtoheadforhome;Rosencrantz'sisn't.Inrelativity,accelerationsmakeabigdifference.

In1988MichaelMorris,KipThorne,andUlviYurtseverrealisedthatcombiningawormholewiththetwinparadoxyieldsaCTC.Theideaistoleavethewhiteendofthewormholefixed,andtozigzagtheblackonebackandforthatjustbelowthespeedoflight.Astheblackendzigzags,timedilationcomesintoplay,andtimepassesmoreslowlyforanobservermovingwiththatend.Thinkaboutworldlinesthatjointhetwowormholesthroughnormalspace,sothatthetimeexperiencedbyobserversateachendarethesame.Atfirstthoselinesarealmosthorizontal,sotheyarenottimelike,anditisnotpossibleformaterialparticlestoproceedalongthem.

Butastimepasses,thelinegetsclosertothevertical,andeventualyitbecomestimelike.Oncethis`timebarrier'iscrossed,youcantravelfromthewhiteendofthewormholetotheblackthroughnormalspace-folowingatimelikecurve.Becausethewormholeisashortcut,youcandosoinaveryshortperiodoftime,effectivelytravelinginstantlyfromtheblackendtothecorrespondingwhiteone.Thisisthesameplaceasyourstartingpoint,butinthepast.

You'vetraveledintime.

Bywaiting,youcanclosethepathintoaCTCandendupatthesameplaceandtimethatyoustartedfrom.Notbacktothefuture,butforwardtothepast.Thefurtherintothefutureyourstartingpointis,thefurtherbackintimeyoucantravelfromthatpoint.Butthere'sonedisadvantageofthismethod:youcannevertravelbackpastthetimebarrier,andthatoccurssometimeafteryoubuildthewormholes.Nohopeofgoingbacktohuntdinosaurs.OrtotreadonCretaceousbutterflies.

Couldwerealymakeoneofthesedevices?Couldwerealygetthroughthewormhole?

Thereareothertimemachinesbasedonthetwinparadox,butalofthemarelimitedbythespeedoflight.Theywouldworkbetter,andperhapsbeeasiertobuildandoperate,ifyoucouldfolowStarTrekandengageyourwarpdrive,travelingfasterthanlight.

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Butrelativityforbidsthat,right?

Wrong.

Specialrelativityforbidsthat.Generalrelativity,itturnsout,permitsit.TheamazingthingisthatthewayitpermitsitturnsouttobestandardSF

gobbledegook,invokedbyinnumerablewriterswhoknewaboutrelativisticlimitationsbutstilwantedtheirstarshipstotravelfasterthanlight.

`Relativityforbidsmattertravelingfasterthanlight,'theywouldincant,`butitdoesn'tforbidspacetravelingfasterthanlight.'Putyourstarshipinaregionofspace,andleaveitstationaryrelativetothatregion.NoviolationofEinsteinthere.Nowmovetheentireregionofspace,starshipinside,withsuperluminal(faster-than-light)speed.Bingo!

Ha-ha,mostamusing.Except...

Inthecontextofgeneralrelativity,that'sexactlywhatMiguelAlcubierreMoyacameupwithin1994.HeprovedthatthereexistsolutionsofEinstein'sfieldequationsinvolvingalocal`warping'ofspacetimetoformamobilebubble.Spacecontractsaheadofthebubbleandexpandsbehindit.Putastarshipinsidethebubble,anditcan'surf'agravitationalwave,cocoonedinsideastaticsheloflocalspacetime.Thespeedofthestarshiprelativetothebubbleiszero.Onlythebubble'sboundarymoves,andthat'sjustemptyspace.

TheSFwriterswereright.Thereisnorelativisticlimittothespeedwithwhichspacecanmove.

Warpdriveshavethesamedrawbackaswormholes.Youneedexoticmattertocreatethegravitationalrepulsionneededtodistortspacetimeinthisunusualway.Otherschemesforwarpdriveshavebeenproposed,whichalegedlyovercomethisobstacle,buttheyhavetheirowndrawbacks.SergeiKrasnikovnoticedoneawkwardfeatureofAlcubierre'swarpdrive:theinsideofthebubblebecomescausalydisconnectedfromthefrontedge.Thestarship'scaptain,insidethebubble,can'tsteerit,andshecan'teventurnitonoroff.Heproposedadifferentmethod,a'superluminalhighway'.Ontheoutwardtrip,thestarshiptravelsbelowlightspeedandleavesatubeofdistortedspacetimebehindit.Onthewayback,ittravelsfasterthanlightalongthetube.Thesuperluminalhighwayalsoneedsnegativeenergy;infact,KenOlumandothershaveprovedthatanytype

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ofwarpdrivedoes.

Therearelimitstothelifetimeofanygivenamountofnegativeenergy.Forwormholesandwarpdrivestheselimitsimplythatsuchstructuresmusteitherbeverysmal,orelsetheregionofnegativeenergymustbeextremelythin.Forexample,awormholewhosemouthisthreefeet(1m)acrossmustconfineitsnegativeenergytoabandwhosethicknessisonemilionthofthediameterofaproton.Thetotalnegativeenergyrequiredwouldbeequivalenttothetotaloutput(inpositiveenergy)of10bilionstarsforoneyear.Ifthemouthwereonelightyearacross,thenthethicknessofthenegativeenergybandwouldstilbesmalerthanaproton,andnowthenegativeenergyrequirementwouldbethatof10quadrilionstars.

Warpdrives,ifanything,areworse.Totravelat10timeslightspeed(amereStarTrekWarpFactor2)thethicknessofthebubble'swalmustbe10-32metres.Ifthestarshipis200yards(200m)long,theenergyrequiredtomakethebubblehastobe10biliontimesthemassoftheknownuniverse.

Engage.

Roundworldnarrativiumcansometimesbedocumented.WhenRonaldMalettwastenyearsoldhis33-year-oldfatherdiedofheartfailure,broughtonbydrinkingandsmoking.Ìtcompletelydevastatedme,'heisreportedtohavesaid.'Soonafter,hereadWels'sTheTime[1]MichaelBrooks,`TimeTwister',NewScientist,19May2001,27-9.

Machine.AndhereasonedthatÌfIcouldbuildatimemachine,Imightbeabletowarnhimaboutwhatwasgoingtohappen.'

Thechildishideafaded,buttheinterestintimetraveldidnot.Asanadult,Malettinventedanentirelynewtypeoftimemachine,onethatusesbentlight.

MorrisandThornebentspacetomakeawormholeusingmatter.Massiscurvedspace.Levi-Civitabentspaceusingmagnetism.Magnetismhasenergy,energyis(soEinsteintelsus)mass.Malettpreferstobendspaceusinglight.Light,too,hasenergy.Soitcanactlikemass.In2000,hepublishedapaperonthedeformationofspacebyacircularbeamoflight.

Thenithithim.Ifyoucandeformspace,yououghttobeabletodeformtimetoo.Andhiscalculationsshowedthataringoflightcouldcreatearingoftime-

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aCTC.

WithaMalettbent-lighttimemachine,youcanwalkintoyourpast.Atimetravelermakeshisorherwayintotheclosedloopoflight,space,andtime.Walkingroundtheloophasthesameeffectasmovingbackwardsintime.Themoretimeshewalksroundtheloop,thefurtherbackhegoes,tracingoutahelicalworldline.Whenhehasgonesufficientlyfarintohispast,heexitstheloop.Easy.

Yes,but...we'vebeenherebefore.Ittakeshugeamountsofenergytomakeacircularbeamoflight.

That'strue...unlessyoucanslowthelightdown.Aringofrealyslowlight,Discworld-speed,likethatofsoundonRoundworld,ismucheasiertomake.Thereasonisthataslightslowsdown,itgainsinertia.Thisgivesitmoreenergy,andthewarpingeffectisfargreaterforlesseffortonthepartofthebuilder.

Relativitytelsusthatthespeedoflightisconstant-inavacuum.Inothermedia,lightslowsdown;thisiswhyglassrefractslight,forexample.Intherightmedium,lightcanbeslowedtowalkingpace,orevenstoppedaltogether.ExperimentsbyLeneHaudemonstratedthiseffectin2001,usingamediumknownasaBose-Einsteincondensate.Thisisafurious,degenerateformofmatter,occurringattemperaturesnearabsolutezero;itconsistoflotsofatomsinexactlythesamequantumstate,forminga'superfluid'withzeroviscosity.

SomaybeWels'stimetravelercouldhaveincludedsomerefrigerationequipmentandalaserinhismachine.ButaMalettbent-lighttimemachinesuffersfromthesamelimitationasawormholeone.Youcan'ttravelbacktoanytimebeforethemachinewasconstructed.

Welswasprobablyrighttoeliminatethatencounterwithagianthippopotamus.

Thesearepurelyrelativistictimemachines,buttheuniversehasquantumfeaturestoo,andtheseshouldbetakenintoaccount.Thesearchforaunificationofrelativityandquantumtheory-respectablyknownas`quantumgravity'andoftenderidedasaTheoryofEverything-hasturnedupabeautifulmathematicalproposal,stringtheory.Inthistheory,insteadoffundamentalparticlesbeingpoints,theyarevibratingmultidimensionalloops.Thebest-knownversionusessix-dimensionalloops,soitsmodelofspacetimeisrealytendimensional.Whyhasnoonenoticed?Perhapsbecausetheextrasixdimensionsarecurledupso

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tightlythatnoonehasobservedthem-verypossibly,canobservethem.Orperhaps-theIrishmanagain-wecan'tgothatwayfromhere.

Manyphysicistshopethatstringtheory,aswelasunifyingrelativityandquantummechanics,wilalsosupplyaproofofHawking'schronologyprotectionconjecture-thattheuniverseconspirestokeepeventshappeninginthesametemporalorder.Inthisconnection,thereisafive-dimensionalstring-theoreticrotatingblackholecaledaBMPV[1]blackhole.Ifthisrotatesfastenough,ithasCTCsoutsidetheblackholeregion.

Theoreticaly,youcanbuildonefromgravitationalwavesandesotericstring-theoreticgadgetscaled'D-branes'.

[1]JasonBreckenridge,RobMyers,AmandaPeet,andCumrunVafa.

AndhereweseeahintofHawking'scosmologicaltimecops.LisaDysontookacarefullookatjustwhathappenswhenyouputthegravitationalwavesandD-branestogether.Justastheblackholeiswithinagnat'swhiskerofturningintoatimemachine,thecomponentsstopcolectingtogetherinthesameplace.Instead,theyformashelofgravitons(hypotheticalparticlesofgravity,analogoustophotonsforlight).TheD-branesaretrappedinsidetheshel.Thegravitonscan'tbepersuadedtocomeanycloser,andtheBMPVcan'tbemadetospinrapidlyenoughtocreateanaccessibleCTC.

Thelawsofphysicswon'tletyouputthiskindoftimemachinetogether,unlesssomecleverkindofscaffoldingcanbeinvented.

Quantummechanicsaddsanewspintothewholetimetravelgame.Forastart,itmayopenupawaytocreateawormhole.Ontheverytinylengthscaleofthequantumworld,knownasthePlancklength(around10-35

metres),spacetimeisthoughttobeaquantumfoam-aperpetualychangingmassoftinywormholes.Quantumfoamisakindoftimemachine.Timeissloppingaroundinsidethefoamlikespindriftbobbingontheoceanwaves.Youjusthavetoharnessit.Anadvancedcivilisationmightbeabletousegravitationalmanipulatorstograbaquantumwormholeandenlargeittomacroscopicsize.

Quantummechanicsalsoshedslight,orpossiblydark,ontheparadoxesoftimetravel.Quantummechanicsisindeterminate-manyevents,suchasthedecayof

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aradioactiveatom,arerandom.Onewaytomakethisindeterminacymathematicalyrespectableisthèmanyworlds'

interpretationofHughEverettII.ThisviewoftheuniverseisveryfamiliartoreadersofSF:ourworldisjustoneofaninfinitefamilyof`paralelworlds'

inwhicheverycombinationofpossibilitiesoccurs.Thisisadramaticwaytodescribequantumsuperpositionofstates,inwhichanelectronspincanbebothupanddownatthesametime,and(alegedly)acatcanbebothaliveanddead.'

It'sOKforelectronsandprobablynonsenseforcats.SeeGreebo'scameoappearanceinTheScienceofDiscworld.

In1991DavidDeutscharguedthat,thankstothemanyworldsinterpretation,quantummechanicaltimetravelposesnoobstaclestofreewil.Thegrandfatherparadoxceasestobeparadoxical,becausegrandadwilbe(orwilhavebeen)kiledinaparalelworld,notintheoriginalone.

Wefindthisabitofacheat.Yes,itresolvestheparadox,butonlybyshowingthatitwasn'trealytimetravelatal.Itwastraveltoaparalelworld.

Fun,butnotthesame.Wealsoagreewithanumberofphysicists,amongthemRogerPenrose,whoacceptthatthèmanyworlds'interpretationofquantumtheoryisaneffectivemathematicaldescription,butdenythattheparalelworldsinvolvedareinanysensereal.Here'sananalogy.UsingamathematicaltechniquecaledFourieranalysisyoucanresolveanyperiodicsound,suchasthenoteplayedbyaclarinet,intoasuperpositionof`pure'soundsthatinvolveonlyonevibrationalfrequency.Inasense,thepuresoundsformaseriousof`paralelnotes',whichtogethercreatetherealnote.Butyoudon'tfindanyoneassertingthattheremustthereforeexistacorrespondingsetofparalelclarinets,eachproducingoneofthepurenotes.Themathematicaldecompositionneednothavealiteralphysicalanalogue.

Whataboutparadoxesofgenuinetimetravel,nofaffingaboutwithparalelworlds?Intherelativisticsetting,whichiswheresuchquestionsmostnaturalyarise,thereisaninterestingresolution.Ifyousetupasituationwithparadoxicalpossibilities,itautomaticalyleadstoconsistentbehaviour.

Atypicalthought-experimenthereistosendabiliardbalthroughawormhole,sothatitemergesinitsownpast.Withcare,youcansenditinsothatwhenit

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comes(came)outitbashesintoitsearlierincarnation,deflectingitsothatitneverentersthewormholeinthefirstplace.Thisisthegrandfatherparadoxinlessviolentform.Thequestionforaphysicistis:canyouactualysetsuchparadoxicalstatesup?Youhavetodosobeforethetimemachineisbuilt,thenbuildit,andseewhatphysicalbehaviouractualyoccurs.

Itturnsoutthat,atleastinthesimplestmathematicalformulationofthisquestion,theusualphysicallawsselectaunique,logicalyconsistentbehaviour.Youcan'tsuddenlyplonkabiliardbaldowninsideapre-existingsystem-thatactinvolveshumanintervention,`freewil',anditsrelationtothelawsofphysicsismoot.Ifyouleaveituptothebiliardbal,itfolowsapaththatdoesnotintroducelogicalinconsistencies.Itisnotyetknownwhethersimilarresultsholdinmoregeneralcircumstances,buttheymayweldo.

Thisisalverywel,butitdoesbegthèfreewil'question.It'sadeterministicexplanation,validforidealisedphysicalsystemslikebiliardbals.Now,itispossiblethatthehumanmindisactualyadeterministicsystem(ignoringquantumeffectstokeepthediscussionwithinbounds).

Whatweliketothinkofasmakingafreechoicemayactualybewhatitfeelslikewhenadeterministicbrainworksitswaytowardstheonlydecisionthatitcanactualyreach.Freewilmaybethe'quale'ofdecision-making-thevividfeelingweget,likethevividsenseofcolourwegetwhenwelookataredflower.'Physicsdoesnotyetexplain.howthesefeelingsarise.Soitisusualtodismisseffectsoffreewilwhendiscussingpossibletemporalparadoxes.

Thissoundsreasonable,butthere'sacatch.Thewholediscussionoftimemachines,inphysicsterms,isaboutthepossibilityofpeopleconstructingthevariouswarpedspacetimesthatareinvolved.`Getablackhole,joinittoawhiteone...'Specificaly,itisaboutpeoplechoosingordecidingtoconstructsuchadevice.Inadeterministicworld,eithertheyareboundtoconstructitfromthebeginning,inwhichcasèconstruct'isn'taveryappropriateword,orthethingjustputsitselftogether,andyoufindoutwhatsortof

[1]SeeIanStewart,JackCohen,FigmentsofReality:theoriginsofthecuriousmind(CambridgeUniversityPress,universeyouarein.It'sjustlikeGodel'srotatinguniverse:eitheryou'reinit,oryou'renot,andyoudon'tgettochangeanything.Youcan'tbringatimemachineintobeingunlessitwasalreadyimplicitintheunfoldingofthatuniverseanyway.

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Thestandardphysicsviewpointrealyonlymakessenseinaworldwherepeoplehavefreewilandcanchoosetobuild,ornottobuild,astheyseefit.Sophysics,notforthefirsttime,hasadoptedinconsistentviewpointsfordifferentaspectsofthesamequestion,andhasgotitsphilosophicalknickersinatwistasaresult.

Foraltheclevertheorising,thedreadfultruthisthatwedonotyethavethefoggiestideahowtomakeapracticaltimemachine.Theclumsyandenergy-wastefuldevicesofrealphysicsareapaleshadowoftheelegantmachineofWels'sTimeTraveler,whoseprototypewasdescribedasàglitteringmetalicframework,scarcelylargerthanasmalclock,verydelicatelymade.Therewasivoryinit,andsometransparentcrystalinesubstance.'

There'sstilsomeR&Dneeded.

ProbablythisisaGoodThing.

NINE

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AVOIDINGMADEIRA

THEJOINERWASAMAZED,Ashetoldhismatesinthepubafterwork-soIwasjustfinishing,andthisfelercomesdowntheladderandsaysbeggin'yourpardon,sir,butI'djustliketocheckthatbulkhead,please.

Nothingwrongwithit,saysI,it'sassoundasabel.Thenhesays,right,right,ofcourse,butI'vejustgottochecksomething.Hepulsthispieceofpaperoutofhispocketandreadsitcareful,andsayshe'sgottocheckthatthenewtimberhasn'tgotararetropicalwormthat'lleaveitlookinglikegoodwoodbutweakenitsomuchthattheshipwiltakeintoomuchwaterandwilhavetoputintoMadeiraforrepairs,orsomething,possibly.I'lsoonseeaboutthat,saysIandwhacksitwithmyhammerand,blowme,itcracksinhalf.I'dhaveswornitwasprimetimber,too.Littlewormseverywhere!'

`Funnyyoushouldsaythat,'saidthemanopposite.Òneof'emcameupwhenIwasworkingandaskedifhecouldlookatthecoppernailsIwasusin'.Wel,hetakesoutaknife,scrapesawayatone,it'sabitofrubbishironunderaskin'ocopper!Hadtodohalfaday'sworkagain!Beatsmehowheknew.Tomsaidthechandlersworetheywerealcopperwhenhesupplied'em.'

`Hah,'saidathirdman,ònecameuptomeandsaidwhatwouldIdoifagiantsquidpuledtheshipunder.ItoldhimI'ddonothing,beingasIliveinPortsmouth.'Hedrainedhismug.`Damnedthorough,theseinspectors.'

`Yeah,'saidthefirstman,reflectively.`Theythinkofeverything...'

Àgooseisaninconvenientbird,I'vealwaysthought,'saidMustrumRidculy,carvingit.Justabittoomuchforonebutnotquiteenoughfortwo.'

Heextendedafork.Ànyoneelsewantsome?Rincewind,justgetthemantosendupsomemoreoysters,wilyou?Whatdoyousay,gentlemen?

Anothersixdozen?Let'spushtheboatout,eh?Hahah...'

Thewizardshadtakenroomsataninn,andtheowner,watchingthebustlingstaffdowninhiskitchen,wasalreadythinkinghappilyofanearlyretirement.

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Moneyhadnotbeenaproblem.Hexhadmerelyteleportedsomefromadistantbank.Thewizardshaddebatedthemoralimplicationsofthisforsometime,withtheirmouthsful,buthadcomedowninfavouroftheidea.

Theywere,afteral,DoingTheRightThing.

OnlyPonderwasn'teatingmuch.Henibbledabiscuitandupdatedhisnotes,beforeannouncing:`Wehavecoveredeverything,Archchancelor.

Thenails,theleakingwaterbarrels,thedefectivecompass,thebadmeat...therewereninereasonswhytheBeaglewouldhavecaledinattheislandofMadeira.Hexbelievesthegiantsquidmaybearedherring.Asforthenine...yes,Ithinkwehaveassuredthattheywilnolongeroccur.'

`Remindmewhythat'simportant,wilyou?'saidtheDean.Àndpassthewine,Mustrum.'

`Withoutthisinterventionit'smorethanlikelythatDarwinwilleavetheshipatMadeira,shouldtheBeaglecalthere,'saidPonder.`Hewilbeterriblyseasickonthevoyage.'

`Madeirabeing-?'saidtheDean.

'Oneofagroupofislandsontheway,Dean.Afterthatit'salonghauldowntotheSouthAtlantic,roundthebottomofSouthAmericawithafewstops,andstraightuptotheGalapagosIslands.'

`Down,bottom,up,'mutteredtheDean.`Howcananyonegetthehangofglobularnavigation?'

`ThephenomenonwecalTheLoveOfIron,sir,'saidPonder,smoothly.

'Weonlyfinditinraremetalsthatdropfromthesky,butit'sverycommonhere.Ironheretriestopointnorth.'

Silencefelaroundthetable.

`North?Isthatthebitatthetop?'saidRidculy.

`Conventionaly,sir,yes,'saidPonder,andratherfoolishlyadded,`butona

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globeitdoesn'trealymatter,ofcourse.'

`Yegods,'mutteredtheDean,puttinghishandoverhiseyes.`Howdoestheironknowwhichwaytopoint?'Ridculypersisted.

`Metalcan'tthink.'

Ìt'sabitlike...likepeasturningtofolowtheSun,sir,'hazardedPonder,notsureiftheyactualydid;perhapsitwaspeafarmers.

`Yes,butpeasarelivingthings,'saidRidculy.`They...knowabouttheSun,right?'

`Peasaren'texactlyrenownedfortheirbrains,Archchancelor,'saidtheChairofIndefiniteStudies,`hencethetermpea-brained.'

`Butapeamustbeabloodygeniuscomparedtoalumpofiron,yes?'saidRidculy.

Ponderknewhehadtoputastoptothis.ThewizardswerestildeterminedtoapplycommonsensetoRoundworld,andthatwouldgetthemnowhere.

Ìt'saforcethatcanoccuronglobe-shapedworlds,'hesaid.Ìt'scausedbythemoltenironcorespinning,andhelpspreventlifeonthesurfacebeingfriedbytheSun.'

`SoundslikeDeitiumindisguise,doesn'tit,'saidRidculy.`Planetgetsthisbigmagicalumbrelasothatlifecansurvive?Showsforethought.'Ìtdoesn'tworkquitelikethat,Archchancelor,'saidPonder.`Lifeevolvedbecauseconditionsalowedittodoso.'

Àh,butifconditionshadn'tbeenright,therewouldn'thavebeenanylife,'

saidRidculy.`Thereforethewholeexercisewouldhavebeenpointless.'

`Notrealy,sir.Therewouldn'thavebeenanyonetopointoutthepointlessnessofit,'saidPonder.Ìwasabouttoaddthatsomebirds,likepigeons,useTheLoveOfirontohelpthemnavigatelongdistances.Theyhavetinythingscaled"magnets"intheirhead,saysHex.They're...littlebitsofironthatknowwheretheNorthPoleisÀh,Iknowthatbit,'saidtheLecturerinRecentRunes.`The

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NorthandSouthPolesarethosebitsonaglobewherethespindlecomesout.Butthey'reinvisible,ofcourse,'headded.

Ùm,'saidPonder.

`Justaminute,canwegetbacktothesebirds?'saidRidculy.`Birdswithmagnetheads?'

`Yes?'saidPonder,knowingthatthiswasgoingtobeloaded.`How?'saidRidculy,flourishingagooseleg.Ònthisglobe,birdsgrewoutofgreatbigmonstrouslizardbeasts,isn'tthatso?'

Èr...smalgreatmonstrousbeasts,sir,'saidPonder,wishingnotforthefirsttimethathisArchchancelordidnothaveaknackforrememberinginconvenientdetails.

`Didtheyhavetoflylongdistancesthroughfogandbadweather?'saidtheArchchancelor.

Ìdoubtit,sir,'saidPonder.

'Sodidtheyalreadyhavethesemagnetsintheirheadsfromdayone,ordidtheyturnupbysomegodlyhand?WhatdoesMrDarwinofTheOriginsayaboutthat?

'Notverymuch,sir,'saidPonder.Ithadbeenalongday.

`Butitsuggests,doesitnot,thatTheOlogyhaha,isrightandTheOriginiswrong.Perhapsthemagnetswereaddedwhenneeded?'`Couldbe,sir,'saidPonder.Justdon'tlethimstartontheeyebal,hethought.

Ì'vegotaquestion,'saidRincewind,fromtheendofthetable.`Yes?'saidPonder,quickly.

`There'sgoingtobemonstercreaturesontheseislandswe'reheadingfor,yes?'

`Howdidyouknowthat?'saidPonder.

Ìtjustcametome,'saidRincewindgloomily.`Sotherearemonsters?'

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Òh,yes.Giantsoftheirkind.'

`Withbigteeth?'

`No,notrealy.They'retortoises.'

`Howbig?'

Àboutthesizeofaneasychair,Ithink.'

Rincewindlookedsuspicious.

`Howfast?'

Ìdon'tknow.Notveryfast.'

Àndthat'sit?

'FromaDarwinianperspective,theislandsarefamousfortheirmanyspeciesoffinches.'

Ànyofthemcarnivorous?'

`Theyeatseeds.'

`So...there'snothingdangerouswherewe'regoing?'

`No.Anyway,wedon'thavetogothere.AlwehavetodonowisfindthepointwherehedecidestowriteTheOlogyinsteadofTheOrigin.'

Rincewindpuledthedishofpotatoestowardshim.'Sezyou,'hesaid.

+++Ineedtocommunicategravenews+++

Thewordscameoutoftheair.InRoundworld,Hexhadavoice.`We'rehavingabitofacelebrationhere,'saidRidculy.Ì'msureyournewscanwait,MrHex!'

+++Yes.Itcan+++

`Good.Inthatcase,Deanwouldyoupassme-'

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+++Iwouldnotwishtospoilyourappetite+++Hexwenton.`Gladtohearit.'

+++Thedestructionofthehumanracecanwaituntilafterthepudding+++.

Ridculy'sforkhoveredbetweenhisplateandhismouth.Thenhesaid:`Wouldyoucaretoexplainthis,please,MrStibbons?'

Ìcan't,sir.Whatishappening,Hex?Wecompletedalthosetasksproperly,didn'twe?'

+++Yes.But,pauseforsignificance,haveyouheardofamythicalcreaturecaleda,pauseagain,hydra?+++

`Themonsterwithmanyheads?'saidPonder.`Youdon'tneedtoteluswhenyoupause,bytheway.'

+++Thankyou.Yes.Cutoffoneheadandadozengrowinitsplace.Thishistoryisahydra+++

RincewindnoddedatPonder.`Toldyou,'hesaid,withhismouthful.

+++Iamunabletoexplainwhythisisthecase,buttherearenow1457

reasonswhyDarwindidnotwriteTheOriginofSpecies.Thebookhasneverbeenwritteninthishistory.Thevoyagehasnevertakenplace+++

`Don'tbesily!Weknowitdid!'saidtheDean.

+++Yes.Itdid.Butnow,ithasn't.CharlesDarwinthescientisthasbeenremovedfromthishistorywhileyouate.Hewas,andnowhewasnot.Hebecamealittle-rememberedpriestwhocaughtbutterflies.Hewrotenobook.Thehumanracediesinfivehundredyears+++

`Butyesterday-'Ridculybegan.

+++Considertimenotasacontinuousprocessbutasasuccessionofdiscreteevents.Darwin'sscientificcareerhasbeenexcised.Yourememberhim,butthatisbecauseyouarenotpartofthisuniverse.Todenythisissimplytoscreamatthemonkeysinthenexttree+++

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`Whodidit?'saidRincewind.

`Whatsortofquestionisthat?'saidPonder.`Noonedidit.Thereisn'tanyonetodothings.Thisissomekindofstrangephenomenon.'

+++No.Theactshowsinteligence+++saidHex.+++Remember,Idetectedmalignity.Isurmisethatyourinterferenceinthishistoryhasledtosomecounter-measure+++

Èlvesagain?'saidRidculy.

+++No.Theyarenotcleverenough.Icandetectnothingexceptnaturalforces+++

`Naturalforcesaren'tanimate,'saidPonder.`Theycan'tthink!'+++pausefordramaticeffect...Perhapstheonesherehavelearnedto+++saidHex.

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TEN

WATCH-22

INTHESTANDARDVERSIONOFRoundworldhistory,CharlesDarwin'spresenceontheBeaglecameaboutonlybecauseofahighlyimprobableseriesofcoincidences-soimprobablethatitistemptingtoviewthemaswizardlyintervention.WhatDarwinexpectedtobecomewasnotaglobetrottingnaturalistwhorevolutionisedhumanity'sviewoflivingcreatures,butacountryvicar.

AnditwasalPaley'sfault.

NaturalTheologysseductiveandbeautifulyarguedlineofreasoningfoundconsiderablefavourwiththedevoutpeopleofGeorgian(IIandIV)England,andafterthem,theequalydevoutsubjectsofWiliamIVandVictoria.BythetimeVictoriaascendedtothethrone,in1837,itwasindeedalmostcompulsoryforcountryvicarstobecomeexpertsinsomelocalmoth,orbird,orflower,andtheChurchactivelyencouragedsuchactivitiesbecausetheywerecontinuingrevelationsofthegloryofGod.TheSuffolkrectorWiliamKirbywasco-author,withthebusinessmanWiliamSpence,ofalavishfour-volumetreatiseAnIntroductiontoEntomology,forexample.Itwasfineforaclergymantointeresthimselfinbeetles.Orgeology,arelativelynewbranchofsciencethathadgrabbedtheyoungCharlesDarwin'sattention.

Thebigbreakthroughingeology,whichturneditintoafulyfledgedscience,wasCharlesLyel'sdiscoveryofDeepTime-theideathattheEarthisenormouslyolderthanUssher's6000years.LyelarguedthattherocksthatwefindattheEarth'ssurfacearetheproductofanongoingsequenceofphysical,chemical,andbiologicalprocesses.Bymeasuringthethicknessoftherocklayers,andestimatingtherateatwhichthoselayerscanform,hededucedthattheEarthmustbeextraordinarilyancient.

Darwinhadapassionforgeology,andabsorbedLyel'sideaslikeasponge.However,Charleswasbasicalyratherlazy,andhisfatherknewit.

Healsoknew,toquoteAdrianDesmondandJamesMoore'sbiographyDarwin,that:

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TheAnglicanChurch,fat,complacent,andcorrupt,livedluxuriouslyontithesandendowments,asithadforacentury.Desirableparisheswereroutinelyauctionedtothehighestbidder.Afinerural`living'withacommodiousrectory,afewacrestorentorfarm,andperhapsatithebarntoholdthelocallevyworthhundredsofpoundsayear,couldeasilybeboughtasaninvestmentbyagentlemanofDr.Darwin'smeansandheldforhisson.

That,atleast,wastheplan.

Andatfirst,theplanseemedtobeworking.In1828CharleswasadmittedtotheUniversityofCambridge,takinghisoathofmatriculationonecoldJanuarymorning,swearingtoupholdtheuniversity'sancientstatutesandcustoms,`sohelpmeGodandhisholyGospels'.HewasenroledatChrist'sColegeforadegreeintheology,alongsidehiscousinWiliamDarwinFoxwhohadstartedthepreviousyear.(CharleshadpreviouslyattemptedmedicineinEdinburgh,folowinginthefootstepsofhisfatherandgrandfather,buthebecamedisilusionedandleftwithoutadegree.)AftergettinghisBatchelorofArtsdegree,hemightspendafurtheryearreadingtheology,readytobeordainedinthe,AnglicanChurch.Hecouldbecomeacurate,marry,andtakeuparuralpositionnearShrewsbury.

Itwasalarranged.

ShortlyafterstartingatChrist's,Charleswasbittenbythebeetlebug,asitwere.AnIntroductiontoEntomologysparkedoffanintenseinterestinbeetles,whenseeminglyhalfthenationwasoutsearchingthewoodsandhedgerowstofindnewspecies.Sincethereweremorespeciesofbeetleintheworldthananythingelse,thiswasaseriousprospect.CharlesandhiscousinscouredthebywaysofruralCambridgeshire,pinningtheircatchesinneatrowsonlargesheetsofcardboard.Hedidn'tfindanewspeciesofbeetle,buthefoundarareGermanone,seenonlytwicebeforeinthewholeofEngland.

Towardstheendofhissecondyearatuniversity,examsloomed.DarwinhadbeentoointentonbeetlesandayoungladynamedFannyOwenandhadneglectedhisacademicstudies.Nowhehadameretwomonthslefttodotheworkoftwoyears.Inparticular,therewouldbetenquestionsonthebookEvidencesofChristianity,byoneWiliamPaley.Darwinhadalreadyreadthebook,butnowhereaditagainwithnewattention-andlovedit.Hefoundthelogicfascinating.Moreover,Paley'spoliticalleaningsweredistinctlyleftwing,

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whichappealedtoCharles'sinnatesenseofsocialjustice.BolsteredbyhisstudiesofPaley,Darwinscrapedthrough.

Nextinlinewerethefinalexams.AnotherofPaley'sbookswasonthesylabus:PrinciplesofMoralandPoliticalPhilosophy.Thebookwasoutdated,andsailedclosetothewindof(political)heresyandwelintotheshalowsofunorthodoxy;thatwaswhyitwasonthesylabus.Youhadtobeabletoarguethecaseagainstit,whereapplicable.Itsaid,forexample,thatanestablishedChurchformednopartofChristianity.Darwin,thenaveryconventionalChristian,wasn'tsurewhattothink.Heneededtobroadenhisreading,andinsodoingheselectedyetanotherbookbyhisidolPaley:NaturalTheology.HeknewthatmanyintelectualsderidedPaley'sstanceondesignasnaive.Heknewthathisowngrandfather,ErasmusDarwin,hadheldaradicalydifferentview,speculatingaboutspontaneous

changesinorganismsinhisownbookZoonomia.Darwin'ssympathieswerewithPaley,buthestartedwonderinghowscientificlawswereestablished,andwhatkindofevidencewasacceptable,aquestthatledhimtoabookbySirJohnHerschelwiththemind-numbingtitlePreliminaryDiscourseontheStudyofNaturalPhilosophy.HealsopickedupacopyofAlexandervonHumboldt'sPersonalNarrative,a3754-pageblockbusterabouttheintrepidexplorer'striptoSouthAmerica.

Darwinwasentranced.Herschelstimulatedhisinterestinscience,andHumboldtshowedhimhowexcitingscientificdiscoveriescouldbe.Hedetermined,thenandthere,tovisitthevolcanoesoftheCanaryIslandsandseeforhimselftheGreatDragonTree.HisfriendMarmadukeRamsayagreedtoaccompanyhim.TheywouldleaveforthetropicsonceDarwinhadsignedthe39ArticlesoftheAnglicanChurchathisdegreeceremony.

Toprepareforthejourney,CharleswenttoWalestocarryoutgeologicalfieldwork.HediscoveredthattherewasnoOldRedSandstoneintheValeofClwyd,contrarytothecurrentnationalgeologicalmap.Hehadwonhisgeologists'spurs.

Thenamessagearrived.Ramsayhaddied.TheCanaryschemeshudderedtoahalt.Thetropicsseemedfurtherawaythanever.CouldCharlesgoitalone?HewasstiltryingtodecidewhenabulkypackagearrivedfromLondon.Insidewasaletter,offeringhimtheopportunitytojoinavoyageroundtheworld.Theship

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wouldsailinamonth.

TheBritishNavywasplanningtoexploreandmapthecoastofSouthAmerica.Itwastobeachronometricsurvey,meaningthatalnavigationwouldbedoneusingtherelativelynewandnotfulytrustedtechniqueoffindinglongitudewiththeaidofaveryaccuratewatchorchronometer.A26-year-oldseacaptain,RobertFitzRoy,wouldheadtheexpedition;hisshipwouldbetheBeagle.

FitzRoywasworriedthatthesolitudeofhiscommandmightdrivehimtosuicide.Theriskwasnotfar-fetched:theBeagle'sformercaptainPringleStokeshadshothimselfwhilemappingaparticularlyconvolutedbitofthecoastofSouthAmerica.Further,oneofFitzRoy'suncleshadslithisownthroatinafitofdepression.'[1]Sohehaddecidedthatheneededsomeonetotalkto,tokeephimsane.ItwasthispositionthatwasnowbeingofferedtoDarwin.Thejobwouldbeespecialysuitableforsomeonewithaninterestinnaturalhistory,andtheshiphadthenecessaryscientificequipment.Technicaly,Darwinwouldnotbèship'snaturalist',aslaterhesometimesclaimed,andthatpresumptionwouldeventualyleadtoanalmightyrowwiththeBeagle'ssurgeonRobertMcCormick,becausebytraditionthesurgeondidthejobofnaturalistinhissparetime.Darwinwasbeinghiredasàgentlemancompanion'forthecaptain.

Charlesdecidedtoaccepttheoffer,buthisfather,forewarnedbyCharles'ssisters,refusedpermission.Darwincouldhavegoneagainsthisfather'swishes,butthethoughtmadehimfeelveryuncomfortable,sohewrotetotheNavyandturnedthejobdown.Then,uncharacteristicaly,hisfatheropenedaloophole-ourfirstexampleofwhatlookssuspiciouslylikewizardlyinterference.Charlesmightyetbealowedtogo,hesaid,provided`somepersonofgoodstanding'recommendedit.BothCharlesandhisfatherknewwhowasmeant:UncleJos(Wedgwood,grandsonofthefounderofthepotterycompany).Joswasanindustrialist,andDrDarwintrustedhisjudgement.SoCharlesandhisunclesatupverylate,composingasuitableletter.JostoldDr.Darwinthatsuchavoyagewouldbethemakingoftheyoungman.And,slyly,headdedthatitwouldimprovehisknowledgeofnaturalhistory,whichwouldbeveryusefulforasubsequentcareerintheclergy.

DarwinSeniorrelented(scoreonetothewizards).Excitedbeyondmeasure,CharleshurriedlywroteanotherlettertotheNavy,thistimeaccepting.ButthenheheardfromFitzRoy,whotoldhimthatthepostwasnolongervacant.Thecaptainhadgivenittoafriend.

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[1]In1865FitzRoydidexactlythesame.havingbeenturneddownforapromotion.Narrativiumatwork?

However,Darwinwastopofthelistifhisfriendchangedhismind.

DarwinwenttoLondon,tomakecontingencyplansincasehegotlucky,andtokeepanappointmentwithFitzRoy.Hearrivedtobetoldthatthecaptain'sfriendhadchangedhismind,notfiveminutesearlier.(Wizardsagain?)Hiswifehadobjectedtothelengthofthevoyage,thenplannedtobethreeyears.DidDarwinstilwantthejob?

Lostforwords,Charlesnodded.

Darwin'sheartsankwhenhesawtheship.TheBeaglewasarotting,eleven-year-oldbrig,withtenguns.Itwasbeingrebuilt,partlyatFitzRoy'sownexpense,soitwouldbeseaworthyenough.Buttheshipwascramped,amere90feet(30m)longby24feet(8m)wide.Couldhiscompanionshipwiththecaptainsurvivesuchalengthyvoyageinsuchclosecontact?Fortunately,hewasalocatedoneofthelargercabins.

TheBeagle'sassignmentwastosurveythesouthernendofSouthAmerica,inparticularthecomplicatedislandsaroundTierradelFuego.

TheAdmiraltyhadprovided11chronometersfornavigation,becausethetripwouldbethefirstattempttocircumnavigatetheGlobeusingmarinechronometerstofindlongitude.FitzRoyborrowedfivemore,thenboughtsixhimself.SotheBeaglesailedwithamassive22chronometersonboard.

Thevoyagestartedbadly.Darwinwassickasadog,crossingtheBayofBiscay,andhadtoendurethesoundofsailorsbeingfloggedashelaynauseatedinhishammock.FitzRoywashotondiscipline,especialyatthebeginningofavoyage.Privately,thecaptainexpectedhis`companion'tojumpshipthemomentittouchedland,andhotfootitbacktoEngland.TheshipwassupposedtoputinatMadeiratotakeonfreshfood,whichwouldbetheperfectopportunity.ButtheMadeiralandingwascanceledbecausetheseawastooheavyandtherewasnopressingneed(score3tothewizards?).

Instead,theBeagleheadedforTenerifeintheCanaries.IfCharlesjumpedshipthere,hecouldseethevolcanoesandtheGreatDragonTree.ButtheconsulinSantaCruzwasscaredthatvisitorsfromEnglandmightintroducecholeratohis

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islands,andherefusedtheBeaglepermissiontoputintoportwithoutundergoingquarantine(score4?We'lsee).Unwilingtowaitofflandfortherequiredtwoweeks,FitzRoyorderedtheBeaglesouth,totheCapeVerdeIslands.

Itmaynothavebeenthewizardsatwork,butsomethingwasdeterminedthatCharlesshouldstayontheBeagle.Andnow,afifthcoincidence,involvinghisgreatlove,geology,madeitimpossibleforhimtodoanythingelse.AstheBeaglesailedwestward,theoceangrewcalm,theairwarm.

Darwincouldtrawlforplanktonandjelyfishwithhome-madegauzenets.

Thingswerelookingup.Andwhentheyfinalytouchedland,theislandofStJagointheCapeVerdeIslands,Darwinfoundithardtobelievehisluck.StJagowasaruggedvolcanicoutcrop,withconicalvolcanoesandlushvaleys.Charlescoulddogeology.Andnaturalhistory.

Hecolectedeverything.Henoticedthatanoctopuscanchangecolour,andmistakenlythoughtthiswasanewdiscovery.Aftertwodays,hehadworkedoutthegeologicalhistoryoftheisland,usingtheprincipleshehadlearnedfromLyel.Lavahadflowedovertheseabed,trappingshelsandotherdebris,andhadlaterbeenraisedtothesurface.Alofthismusthavehappenedrelativelyrecently,becausetheshelswerejustlikethefreshoneslyingonthebeach.Thiswasnottheconventionaltheoryoftheday,whichheldthatvolcanicstructureswereincrediblyold.

Theyoungmanwascomingintohisown.

Intheend,thevoyagelastedfiveyears,andinthewholeofthattime,poorDarwinneverfoundhissea-legs.Evenonthefinalrunhome,hewasstilseasick.Buthecontrivedtospendmostofthevoyageonland,andonly18

monthsatsea.Andwhileonland,hemadediscoveryafterdiscovery.HefoundfifteennewspeciesofflatworminBrazil.Hestudiedrheas,giantflightlessbirdsrelatedtotheostrich,inArgentina.There,too,hefoundfossils,includingtheheadofagiantarmadilo-likeglyptodont.InTierradelFuegoheturnedanthropologist,andstudiedthepeople.Ìshalneverforgethowsavage&wildonegroupwas,'hewrote,onencountering`nakedsavages'.Hefoundmorefossils,amongthembonesofthegroundslothMegatheriumandthelama-likeMacrauchenia.InChile,hestudiedthegeologyoftheAndesanddecidedthat

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they,andtheplainsbeyond,hadbeenthrustskywardinsomegiganticgeologicalupheaval.

FromtheSouthAmericanmainland,theBeaglewentnorth-westtotheGalapagos,atightgroupofadozenorsoislands,faroutintothePacificocean.Theislandshadfascinatinggeology,mainlyvolcanic,andagreatvarietyofanimalsthatwerenotfoundanywhereelse.Therewerethespectaculargianttortoisesthathadgiventheislandstheirname.Darwinmeasuredthecircumferenceofoneassevenfeet(2m).Therewereiguanas,andbirds-boobies,warblers,finches.Thefincheshadbeaksofdifferentshapesandsizes,dependingonthefoodtheyate,andDarwindividedthemupintoaseriesofsubfamilies.Hedidnotnoticethatdifferenttypesofanimalsoccurredondifferentislands,untilNicholasLawsonpointedthisout.(Thewizardsagain?Ohyes,thiswilhavehappenedsoon...)ButhedidnoticethatthemockingbirdsofCharlesandChathamislands(nowSantaMariaandSanCristobal)weredifferentspecies,andwhen,nowalerted,helookedonJamesIsland(SanSalvador),hefoundyetathirdspecies.ButDarwinwasnotgreatlyinterestedinsmalvariationsinspecies,orhowthosevariationscorrespondedtothelocalgeography.Hewasvaguelyawareofsometheorisingaboutspecieschange,or`transmutation',ifonlyfromhisgrandfatherErasmus,butthetopicdidn'tinteresthimandhesawnoreasontocolectevidenceforor,againstit.

AndsotheBeaglecontinuedtoTahiti,NewZealand,andAustralia.

Darwinhadseenwondersthatwouldshortlyrevolutionisetheworld.Buthedidnotyetunderstandwhathehadseen.

InTahiti,though,heglimpsedhisfirstcoralreef.BeforeleavingAustralia,hewasdeterminedtofindouthowcoralislandscameintobeing.Lyelhadsuggestedthatbecausethecoralanimalsliveonlyinshalowwaters,withamplesunlight,thereefsmustbebuiltontopofsubmergedvolcanoes.

Thisalsoexplainedtheirringedshape.Darwindidn'tbelieveLyel'stheory.

`Theideaofalagoonisland,30milesindiameterbeingbasedonasubmarinecraterofequaldimensions,hasalwaysappearedtometobeamonstroushypothesis.'Instead,hehadhisowntheory.Healreadyknewthatlandcouldrise,he'dseenthatintheAndes.Hereasonedthatifsomelandwentup,thenotherlandoughttogodown,tomaintainthebalanceoftheEarth'scrust.

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Supposethatwhenthereefstartedtoform,thewaterwasshalow,butthentheoceanfloorstarteddescendingslowly,whilethecoralpolypsatthesurfacecontinuedbuildingthereef.Theneventualyyouwouldgetahugemountainofcoralrisingfromwhatwasnowtheoceandepths-

albuiltbytinycreatures,alwaysinshalowwaterwhilethebuildingwasgoingon.Theshape?Thatwastheresultofanislandwithafringingreefcolapsing.Theislandwouldsink,leavingaholeinthemiddle,butthereefwouldcontinuetogrow.

FiveyearsandthreedaysaftertheBeaglesetsailfromPlymouth,Darwinwalkedintothefamilyhome.Hisfatherglancedupfromhisbreakfast.

`Why,'hesaid,`theshapeofhisheadisquitealtered.'

DarwindidnotcomeupwiththeconceptofevolutionduringhisBeaglevoyage.Hewastoobusyamassingspecimens,mappinggeology,takingnotes,andbeingseasick,tohavetimetoorganisehisobservationsintoacoherenttheory.Butwhenthevoyagewasover,hewaspromptlyelectedtotheRoyalGeologicalSociety.InJanuary1837hepresentedhisinauguralpaper,onthegeologyofChile'scoast.HesuggestedthattheAndesmountainshadoriginalybeentheoceanfloor,buthadlaterbeenuplifted.Hisdiaryrecordsamazementat`thewonderfulforcewhichhasupheavedthesemountains,&evenmoresothecountlessagesneededtohavebrokenthrough,removed&leveledwholemassesofthem'.Muchlater,theChileancoastbecamepartoftheevidencefor`continentaldrift':wenowthinkthatthesemountainsresultfromsubduction,astheNazcatectonicplateslidesunderneaththeSouthAmericanplate.

Darwincouldcertainlyspotthem.

Hisinterestingeologyhadother,lessobvious,implications.HewasstartingtowonderaboutthefinchesoftheGalapagos.TheyseemedtocontradictLyel'sviewthatlocalgeologicalconditionsdeterminedwhatspecieswerecreated.Itwasapuzzle.

Infact,itwasmoreofapuzzlethanDarwinthought,becausehehadmisunderstoodthefinchescompletely.Hethoughttheyalfedonthesamefood,inbigflocks.Hehadnotnoticedimportantdifferencesamongtheirbeaks,andheevenhadtroubleidentifyingdifferentspecies.Some,hebelieved,werenotfinchesatal,butwrensandblackbirds.Hewassobaffledbythebirds,andso

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indifferenttothespecimenshehadcolected,thathedonatedthelottotheZoologicalSociety.WithintendaystheSociety'sbirdexpertJohnGouldhadworkedoutthattheywerealfinches,alverycloselyrelated,formingatightlyknitgroupingthatnonethelesscontainedtwelve[1]distinctspecies.Thisnumberwassurprisinglylargeforsuchasmalgroupoftinyislands.Whathadcausedsuchdiversity?

Gouldwantedtoknow,butDarwindidn'tcare.

By1837,Paley'slogicwasnolongerinvogue.ThescientificalyliteratetheistnowbelievedthatGodhadsetupthelawsofnatureatthetimeofCreation,andthatthoselawsincludednotjustthèbackground'lawsofphysics,towhichPaleysubscribed,butalso[1]Nowconsideredtobethirteen,plusafourteenthontheCocosIslands.

(Look,peoplewriteandcomplainifwedon'tpointthiskindofthingout.)thedevelopmentoflivingcreatures,whichPaleyhaddenied.Thelawsoftheuniversewerefixedforaleternity.Theyhadtobe,otherwiseGod'screationwasflawed.Paley'sanalogieswereusedagainsthim.WhatkindofartificermadesuchbadmachinerythatHehadtokeeptinkeringwithitalthetimetokeepitworking?

Scienceandtheologywererippingasunder.ThepoliticalcorruptionoftheChurchwasbecomingundeniable;nowitsintelectualclaimswerealsocomingunderfire.Andsomeradicalthinkers,oftenmedicswhohadstudiedcomparativeanatomyandnoticedremarkablesimilaritiesbetweenthebonesofentirelydifferentanimals,wereengagedinspeculationthatchangedtheviewofcreationitself.AccordingtotheBible,Godhadcreatedeachtypeofanimalasaone-offitem-whalesandwingedfowlonthefifthday,cattleandcreepingthingsandhumansonthesixth.Butthesemedicaltypeswerestartingtothinkthatspeciescouldchange,`transmute'.Specieswerenotfixedforaltime.Theyrealisedthattherewasaratherbiggapbetween,say,abananaandafish.Youcouldn'tcrossthatgapinonestep.Butgivenenoughtime,andenoughsteps...

Darwinslowlybecamecaughtupintheflow.HisRedNotebook,whereherecordedanythingthathesaworthatcametomind,begantohintatthèmutabilityofspecies'.Thehintswereincompleteandil-assorted.

Deformedbabiesresemblednewspecies.ThebeaksofGalapagosfincheswere

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ofdifferentshapesandsizes.Rheaswereapuzzle,though:twodistinctspeciesofthegiantbirdshadoverlappingrangesinPatagonia.Whydidn'ttheymergeintoasinglespecies?

ByJuly,hehadsecretlystartedanewnotebook,hisBNotebook.

Itwasonthetransmutationofspecies.

By1839Darwinwasbuildingupacompletepicture,andhewrotea35-pagesummaryofhisthinking.AcrucialinfluencewasThomasMalthus,whose1826EssayonthePrincipleofPopulationpointedoutthattheuncheckedgrowthoforganismsisexponential(or'geometric',intheold-fashionedphraseofthetime),whereasthatofresourcesislinear(àrithmetic').Exponentialgrowthoccurswheneachstepmultipliesthesizebysomefixedamount,forexample1,2,4,8,16,32,whereeachnumberistwicethepreviousone.Lineargrowthaddssomefixedamountateachstep,forinstance2,4,6,8,10,whereeachnumberexceedsthepreviousoneby2.Howeversmalthemultiplierisinexponentialgrowth,provideditisbiggerthan1,andhoweverlargethenumberaddedinlineargrowthmaybe,itturnsoutthatinthelongrunexponentialgrowthalwaysbeatslinear.Thoughitdoestakesometimeifthemultiplieriscloseto1andthenumberbeingaddedishuge.

DarwinhadtakenonboardMalthus'sargument,andhehadrealisedthatinpracticewhatkeepspopulationsdowniscompetitionforresources,suchasfoodandaplacetolive.Thiscompetition,hewrote,leadstònaturalselection',inwhichthosecreaturesthatarevictoriousinthèwarofnature'aretheonesthatproducethenextgeneration.Individualcreatureswithinaspeciesarenotexactlyidentical;thosedifferencesmakeitpossiblefortheforceofnaturalselectiontoproduceslow,gradualchanges.Howfarmightsuchchangesgo?InDarwin'sview,veryfarindeed.Farenoughtoleadtoentirelynewspecies,givenenoughtime.

Andthankstogeology,scientistsnowknewthattheEarthwasvery,veryold.

Darwin,folowingfamilytradition,wasaUnitarian.ThisparticularbranchofChristianityhasbeenaptlydescribedas`peoplewhobelieveinatmostoneGod'.AsasoundUnitarian,hebelievedthattheDeitymustworkonthegrandestofscales.SohefinishedhissummarywithapowerfulappealtotheUnitarianviewoftheDeity:

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ItisderogatorythattheCreatorofcountlesssystemsofworldsshouldhavecreatedeachofthemyriadsofcreepingparasitesandslimywormswhichhaveswarmedeachdayoflifeonlandandwateronthisoneglobe.Weceasebeingastonished,howevermuchwemaydeplore,thatagroupofanimalsshouldhavebeendirectlycreatedtolaytheireggsinbowelsandfleshofothers-thatsomeorganismsshoulddelightincruelty...Fromdeath,famine,rapine,andtheconcealedwarofnaturewecanseethatthehighestgood,whichwecanconceive,thecreationofthehigheranimalshasdirectlycome.

Godsurelyhasbettertastethantocreatenastyparasitesdirectly.Theyexistonlybecausetheyareanecessarystepalongthepaththatleadstocats,dogs,andus.

Darwinhadhishypothesis.

Nowhebegantoagoniseabouthowtobringittothewaitingworld.

ELEVEN

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WIZARDSONTHEWARPATH

INTHEGLOOMOFTHEHighEnergyMagicbuilding,Hexwrote.Everyminuteanotherpageslidoffthewritingtable.

"`BoatsunkbycolisionwithSpanishfishingvessel",'PonderStibbonsreadout,atremorinhisvoice."`BoatshipwreckedonunchartedreefnearMadeira.Boatfounddriftingminusalcrew,withthetablelaidforameal.

Boatcatchesfire,allost.Boatstruckbymeteorite.Darwinaccidentalyshotbyship'ssurgeonandnaturalistduringacolectingexpeditionontheislandofStJago.Darwinaccidentalyshotbyship'scaptain.Darwinaccidentalyshotbyhimself.Darwinlosesplaceonboat.Darwinleavesboatbecauseofseasickness.Darwinlosesnotebooks.Darwinstungtodeathbywasps!Darwinbangsheadonundersideoftableandlosesmemory..."'Heputdownthepaper.Àndthesearethemoresensiblecauses.'

`Thestonedroppingoutoftheskywassensible?'saidRidculy.

`Comparedtotheattackofthegiantsquid,Archchancelor,Iwouldsayso,'

saidPonder.Àndtheenormouswaterspout.AndtheshipwreckoffthecoastofNorway.'

`Wel,shipsdogetwrecked,'saidtheDean.

`Yes,sir.ButthecountryknownasNorwayisinthewrongdirection.TheBeaglewouldonlygettherebysailingbackwards.Hexisright,sir.Thisisinsane.Themomentthatwedecidedtochangeonesimplelittlehistory,thewholeoftheuniverseistryingtostopthevoyagehappening!Andmathematicalyspeaking,thisisilegal!'

Ponderthumpedthetable,hisfacered.Theseniorwizardsshied.Thiswasasunnervingashearingasheeproar.

'Myword!'saidRidculy.Ìsit?

'Yes!TheremustberoominphasespaceforthepossibilitythatOrigingets

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written!It'snotagainstthephysicallawsofthisuniverse!'

`Thatayounginexperiencedmantakesavoyagearoundthisworldandhasaninsightthatchangesmankind'sviewofitself?'saidtheDean.`Youmustadmititlooksabitunlikely-sorry,sorry,sorry!'HebackedawayasPonderadvanced.

ÒneofthebiggestreligionsonRoundworldwasfoundedbyacarpenter'sson!'Pondersnarled.`Foryears,themostpowerfulpersonontheplanetwasanactor!There'sgottoberoomforDarwin!'

Hestampedbacktothetableandpickedupahandfulofpapers.`Lookatthisstuff!"Darwinbittenbypoisonousspider...Darwinsavagedbykangaroo...stungbyjelyfish...eatenbyshark...Beaglefoundfloating,tablelaidforameal,thistimeinadifferentocean,stilnooneonboard...

Darwinstruckbylightning...kiledbyvolcanicactivity...Beaglesunkbyfreakwave"...doesanyoneexpectustobelievethisforoneminute?'

Therewasaringingsilence.

Ìcanseethisisworryingyou,MrStibbons,'saidRidculy.

`Wel,yes,Imean,yes,it'sso...wrong!Themultiverseisnotsupposedtochangetherules.Anythingthat'spossibletohappenhasauniverseforittohappenin!Imean,here,yes,therulescanbebentinalkindsofways,butinRoundworldthere'snoonetobendthem!'

Ì'vegotanidea,'saidRincewind.Theotherwizardsturned,amazedatthisrevelation.

`Yes?'saidPonder.

`Whynotjusttakeitforgrantedthatsomeoneisouttogetyou?'saidRincewind.`That'swhatIdo.Don'tbothertoworkoutthefinedetail.Look,whenyoufirststartedtotinker,itwasalgoingtobeplainsailing,right?

Makeafewlittleadjustments,pinchafish,andit'dalbeOK?Butnowtherearenearlyfifteenhundrednewreasons-'

Witharattle,Hex'swritingdeskstartedup.Thepenswrote:+++3563

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reasonsnow+++

`They'rebreeding!'saidRidculy.

`Thereyouare,then,'saidRincewind,almostcheerfuly.`Somethingdownthereisfrightened.It'ssofrightenedthatit'snotevengoingtolethimgetontheboat.Imean,hehastotakethevoyagewhateverbookhewrites,isn'tthatright!'

`Yes,ofcourse,'saidPonder.TheologyofSpeciesgetstakenseriouslybecauseit'swrittenbyarenownedandrespectedscientistwhoseresearchwasmeticulous.SowasTheOrigin.Eitherway,heneedstobeonthatboat.Butthemomentwetakeaninterest,thevoyagedoesn'thappen!'

`Thenifitwasme,I'dsaythatsomething'sgotrealyworried,'saidRincewind.`Theydon'tmindifTheOlogydoesn'tgetwritteninjustoneuniverse,buttheyhatetheideaofTheOriginbeingwrittenatal.

Òh,realy?'saidRidculy.`Thenerve!Iamthemasterofthiscolege,andthat-'hepointedtothelittleglobe'-isuniversityproperty!NowI'mgettingangry.We'regoingtofightback,MrStibbons!'

Ìdon'tthinkyoucanfightawholeuniverse,sir!'It'stheprerogativeofeverylifeform,MrStibbons!'

Galesroaredforthreeweeks.Roundworldtimewasmutableforthewizards;itonlyaffectedthemiftheywanteditto.

Somethingorsomeonedidn'twanttheBeagletosail,andtheycouldinfluencetheweather.Theycouldinfluenceanything.Butofthem,therewasstilnosign.

TheDeanwatchedthestorminthebigomniscopeintheHEM.

`That'swhathappenedwhenDarwingetsonboardinthisuniverse,'saidPonder,adjustingtheomniscope.Ìfhehadn'tgone,hisplaceistakenbyanartist,whoproducedafamousportfolioasaresult.HisnamewasPreservedJ.Nightingale.Youmethiswife.'

`Preserved?'saidtheDean,watchingthedismalgale.

`ShortforPreserved-by-God,'saidPonder.`Hewasfoundasachildinthe

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wreckageofaship.Hisadoptedparentswereveryreligious.And...ahyes...thisistheweathertheygetwhenheisonboard.'

Theomniscopeflickered.

`Nogale?'saidtheDean,lookingatthebluesky.

`Briskwindsfromthenorth-east.They'rebal-worlddirections,sir.Forthepurposesofthevoyage,theyareideal.Iseeyouhaveyour"BorntoRune"

jacketon,sir.'

`We'vegotafightonourhands,Stibbons,'saidtheDean,severely.Ìt'salongtimesinceI'veseentheArchchancelorsoangryatanyonebutme!

Haveyoufinished?'

'Justfinishing,sir,'saidPonder.

TheHEMhadadesertedlook.Thatwasbecauseithadbeen,byandlarge,deserted.ThicktubesledoutfromHex,acrossthefloorandoutoverthelawntowardsUU'sGreatHal.

Thewizardsweregoingtowar.Ittookalottomakethathappen,butyoucouldn'tletanyolduniversepushyouaround.Gods,demonsandDeathwereonething,butmindlessmattershouldn'tbealowedtogetideas.

`Couldn'twejustfindawaytobringDarwinbackhere?'saidtheDean,watchingPonderprodbuttonsonHex'skeyboard.

`Quiteprobably,sir,'saidPonder.

`Wel,then,whydon'twejustbringhimhere,explainthesituation,anddrophimoffonhisisland?Wecouldevengivehimacopyofhisbook.'

Pondershuddered.

`Therearequitealotofreasonswhythatcourseofactionmightnot,withease,berescuedinanycoherentwayfromthecategoryoftheinsanelyunwise,Dean,'hesaid,havingworkedoutthattheseniorwizardslostinterestinanysentence

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thatwentonpasttwentywords.`Foronething,he'dknow.'

`Wecouldbophimonthehead,'saidtheDean.Òrputa'fluenceonhim.

Yes,that'dbeagoodidea,'hesaid,becauseitwashis.`Wecouldsithiminacomfychairandreadouttherightbooktohim.He'dwakeupbackhomeandthinkhe'smadeitalup.'

`Buthewouldn'thavebeenthere,'saidPonder.Hewavedahand.Intheairoverhead,alittlebalofmulticolouredlightappeared.Itlookedlikeatangleofglowingstrings,orthematingofrainbows.

Òh,wecouldsortthatout,'saidtheDeanairily.`Sticksomesandinhisboots,afewfinchfeathersinhispocket...wearewizards,afteral.'

`Thatwouldbeunethical,Dean,'saidRidculy.`Why?We'retheGoodGuys,aren'twe?'

`Yes,butthatratherhingesondoingcertainthingsandnotdoingothers,sir,'saidPonder.`Playingaroundwithpeople'sheadsagainsttheirwilisalmostcertainlyoneofthenots.Youshouldgetreadytomovequickly,sir.'

`Whatareyoudoing,Stibbons?'

Ì'vegotHextocastathaumaticglyphinconditionalDarwinspace,'saidPonder.`ButtoresolveitproperlyHexwilhavetorunthethaumicreactoralittlehigherthanusual.'

`Howmuchhigher?'saidtheDeansuspiciously.Àbout200percent,sir.'

Ìsthatsafe?'

Àbsolutelynot,sir.Hex,glyphicresolutionintwentyseconds.Dean,run!

Run,sir!'

FromthedirectionoftheOldSquashCourtcameasoundthathadbeentherealthetime,unheeded,andwasnowgrowinglouder.Itwasthewhumwhumofdyingthaums,eachoneyieldingupitsintrinsicmagic...

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Wizardshaveawonderfulturnofspeed.

PonderandtheDeanreachedtheGreatHalintwelveseconds,theDeanslightlyinthelead.Thebalofrainbowshadgottherebeforethem,though,andhunghighovertheblackandwhiteflagstonesofthefloor.

Thehalwaspackedwithwizards.Teamshadbeensentouttothefurthestcornersoftheuniversity,whichwereprettyfar.Spaceandtimehadlongagobeenwarpedbytheancientmagicalstones,andtherewerewizardsatUUwhohadhappilyoccupiednooksandcornersfordecadesorlonger,regardingtheGreatHalandsurroundingbuildingsasthecolonistsonsomefarawaycontinentmightregardtheancientmothercountry.Distantstudieshadbeenbrokenintoandtheiroccupantsdraggedoutor,insomeunfortunatecases,sweptup.WizardsthatPonderhadneverseenbeforewereinthethrong,blinkinginthelightofcommonday.

Pantingslightly,PonderhurriedovertoRidculy.

`Yousaidyouwantedamap,sir,'hesaid.

`Yes,Stibbons.Can'tplanacampaignwithoutamap!'

`Thenlookupnow,sir!Hereitcomes!'

Theairwaveredforamoment,andthenthematedrainbowsgavebirth.

Frozenstreamersoflightloopedthroughthehazyairofthehal.Theytwistedandtangledandcurvedinwaysthatsuggestedmorethantheeverydayfourdimensionswereinvolved.

`Looksverypretty,'saidtheArchchancelor,blinking.'Er...'

Ìthoughtitwouldhelpussortoutfurthernodalities,'saidPonder.

Àhyes,goodidea,'saidRidculy.`Noonewantsunsortednodalities.'Theotherseniorwizardsnoddedsagely.

`BywhichImean,'Ponderadded,ìtwilshowusthosepointswhereourinterventionwilhavebeengoingtobewasessential,ifIcanputitthatway.'

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Òh,'saidtheArchchancelor.Èr...whatdoesthecolouredlinemean,exactly?'

`Whichone,sir?'

Àlofthem,man!'

`Wel,thepointsofinterventionthatrequireahumanshowupasredcircles.ThosethatcanbelefttoHexarewhite.Thebluelinesrepresenttheauthorof,ahem,TheOlogy,theyelowlinesistheoptimumpathfortheauthorofTheOrigin,andthegreenlinerepresentslippagebetweenfutures.Knownthaumicocclusionsarepurple,butIexpectyouworkedthatoutalready.'

`What'sthatone?'saidtheDean,pointingtoaredcirclewithhisstaff.

`Wemustmakecertainhedoesn'tgetofftheboatatanislandcaledTenerife,'saidPonder.`Seasicknessagain,yousee.QuiteafewDarwinsgotoffthere.'

Thetipofthestaffmoved.Àndthatone?'

`HemustgetofftheboatattheislandofStJago.Hehasvaluableinsightsthere.'

`Seesthingsevolvin',thatkindofthing?'saidRidculy.

`No,sir.Youcan'tseethingsevolving,evenwhenthey'redoingit.'`WesawthemonMonoIsland,'saidtheLecturerinRecentRunes.

`Youcouldpracticalyhearthem!'

`Yes,sir.Butwehaveagodofevolution.Godsaren'tpatient.OnRoundworld,evolutiontakestime.Lotsoftime.DarwinwasraisedinthebeliefthattheRoundworlduniversewascreatedinsixdays-'

`Whichiscorrect,asIhavepointedout,'saidtheDeanproudly.

`Yes,'saidPonder,`butIhavealsopointedoutthatontheinsideittookbilionsofyears.ItisvitalthatDarwinrealisesthatevolutionhasgotlotsoftimetoworkin.'

BeforetheDeancouldprotest,Ponderturnedbacktotheshining,twistingtangleoflight.

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'ThereiswherethemastfalsonhisheadintheportofBuenosAires,'hesaid,pointing.`TheBeaglewasshotat.Itwasmeanttoheablank,firedfromacannon,butforsomereasonithadbeenloaded.TheBritishwereveryupsetaboutit,andissuedasterndiplomaticprotestbysendingawarshiptobombardtheporttorubble.ThisoneiswhereDarwinbludgeonshimselfintounconsciousnesswithhisownbolasinArgentina.

Thisoneiswherehe'sseverelyinjuredputtingdownaninsurrection-'

`Hegotaboutabitforamanwhocolectedflowersandthings,'saidRidculy,withatouchofadmiration.

`Look,I'vebeenthinkingaboutalthis,'saidtheDean.`This"science"isalaboutthesearchfortruth,yes?Whydon'twejusttelthemthetruth?'

`Youmeantelthemthattheiruniversewasaccidentalystartedbyyou,Dean,stickingyourhandintosomerawfirmamentcreatedtouseupsparepowerfromthethaumicreactor?'saidRidculy.

`Putlikethatitseemsabitunlikely,Iadmit,but-'

`Nodirectcontact,Dean,weagreedaboutthat,'saidRidculy.`Wejustclearhisway.What'sthatnodality,Stibbons?It'sflashing.'

PonderlookedatwheretheArchchancelor'sstaffwaspointing.

`That'satrickyone,sir.WewilhavetoensurethatEdwardLawson,aBritishofficialintheGalapagosIslands,isn'tstruckbyameteorite.It'sanewmalignity,Hexsays.Inanumberofhistories,ithappensafewdaysbeforehemeetsDarwin.Remember,sir?Imentioneditinmyyelowfolderthatwasdeliveredtoyourofficethismorning.'Pondersighed.`HedrawsDarwin'sattentiontosomeinterestingfacts.'

Àh,Ireadthatone,'saidRidculy,hishappytoneindicatingthatthiswasaluckycoincidence.`Darwinseemedtobetoobusyrunnin'aroundlikeamonkeyinabananaplantationtospottheclues,eh?'

Ìtwouldbetruetosaythathisfultheoryofnaturalselectionwasevolvedonmaturereflectionsometimeafterhisvoyage,yes,'saidPonder,carefulyansweringaslightlydifferentquestion.

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ÀndthischapLawsonwasimportant?'

`Hexbelievesso,sir.Inaway,everyoneDarwinmetwasimportant.Andeverythinghesaw.'

Àndthenwhoosh,thischapwashitbyarock?Icalthatsuspicious.'

`Hexdoestoo,sir.'

Ì'lbejolygladwhenwe'vegotthisDarwintothedamnislands,then,'saidtheArchchancelor.`We'lneedaholidayafterthis.Ohwel,I'laddressthewizardsnow.Ihopewe'lhaveenoughfor-'

Èr,wehaven'tjustgottogethimtotheislands.We'vegottogethimalthewayhome,sir,'saidPonder.`He'lbeawayfromhomefornearlyfiveyears.'

`Fiveyears?'saidtheDean.Ìthoughtvisitingthewretchedislandswaswhatitwasalabout!'

`Yesandthenagain,inaveryrealsense,no,Dean,'saidPonder.Ìtwouldbemorecorrecttosaytheylaterbecamewhatitwasalabout.Hewasactualythereforalittlemorethanamonth.Itwasaverylongvoyage,sir.

Theywentalaroundtheworld.I'msorry,Ihadn'tmadethatclear.Hex,showtheentiretimelines,please.'

Thedisplaybegantorecede,drawingfromnowheremoreandmoretanglesandloops,asifhalfadozencosmickittenshadbeengivenstarstoplaywithinsteadofbalsofwool.Therewasagaspfromthethrongofwizards.

ThetangleswerestilstreamingawayoverheadwhentheDeansaid:`There'smilionsofthewretchedthings!'

`No,Dean,'saidPonder.Ìtlookslikethat,butthereareonly21,309

importantnodalitiesatthispoint.Hexcandealwithalmostalofthem.Theyinvolvequiteminutechangesatthequantumlevel.'

Thewizardscontinuedtostareupwardsasthewhorlsandloopsflashedbyanddwindled.

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`Someonerealydoesn'twantthatbook,'saidtheLecturerinRecentRunes,hisfaceiluminatedbythemulticolouredglow.

Ìntheorythereisn'tasomeoneincharge,'saidPonder.

`ButtheoddsagainstDarwinwritingOriginaregettingbiggerbytheminute!'

`Theoddsagainstanythingactualyhappeningarehuge,whenyoucometothinkaboutit,'saidRidculy.`Takepoker,forexample.Theoddsagainstfouracesarehuge,buttheoddsofhavinganyfourcardsatalarerealybig.'

`Welput,Archchancelor!'saidPonder.`Butthisisacrookedgame.'

RidculystrodeoutintothecentreoftheGreatHal,hisfaceiluminatedbytheglowingmap.

`Gentlemen!'hebelowed.`Someofyoualreadyknowwhatthisisabout,eh?We'regoingtoforceahistoryonRoundworld!It'sonethatshouldbetherealready!Somethingistryingtokilit,gentlemen.Soifsomeonewantstostopithappening,wewanttomakeithappenalthemore!YouwilbesentintoRoundworldwithaseriesoftaskstodo!Mostofthemhavebeenmadeverysimplesothatwizardscanunderstandthem!Shortlyourmissionsfortomorrow,shouldyouchosetoacceptthem,wilbegiventoyoubyMrStibbons.Ifyoudonotchoosetoacceptthem,youarefreetochoosedismissal!We'restartingatdawn!Dinner,SecondDinner,MidnightSnack,SomnambulisticNibblesandEarlyBreakfastwilbeservedintheOldRefectory!TherewilbenoSecondBreakfast!'

Overachorusofprotesthewenton:`Wearetakingthisseriously,gentlemen!'

TWELVE

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THEWRONGBOOK

OURFICTIONALDARWINHASAlotmoreincommonwiththèreal'one-

theDarwinoftheparticulartimelinethatyouinhabit,theonewhowroteTheOriginandnotTheOlogy-thanmightatfirstbeapparent.Orplausible.TheirresistibleforceofnarrativiuminducesustoimagineCharlesDarwinasanoldmanwithabeard,astick,andafaintbutdefinitehintofgorila.Andsohewas,inhisoldage.Butasayoungmanhewasvigorous,athletic,andengagedinthekindofexuberantandnotalwayspoliticalycorrectactivitiesthatweexpectofyoungmen.

We'vealreadylearnedoftherealDarwin'samazingfortuneingettingonboardtheBeagleandremainingthere,culminatinginhisboundlessdelightatthegeologyofthecoralislandofStJago.Butthereareothercrucialnodalities,pointsofintervention,andthaumicocclusionsinthatversionofRoundworld'shistoricalrecord,andthewizardsareexercisingextremecareandattentioninthehopeofsteeringhistorythrough,past,andaroundthesecausalsingularities.

Forexample,theBeaglerealydidcomeunderfirefromacannon.WhentheshiptriedtoentertheharbouratBuenosAiresin1832,oneofthelocalguardshipsfiredatit.Darwinwasconvincedthatheheardacannonbalwhistleoverhishead,butitturnedoutthattheshotwasablank,intendedasawarning.FitzRoy,muttering

angrilyaboutinsultstotheBritishflag,sailedon,butwasstoppedbyaquarantineboat:theharbourauthoritieswereworriedaboutcholera.

Incensed,FitzRoyloadedalofthecannonsononesideofhisship.Ashesailedbackoutoftheharbourheaimedthemalattheguardship,informingitscrewthatiftheyeverfiredattheBeagleagain,hewouldsendtheir`rottenhulk'totheseabed.

Darwinrealydidlearntothrowabolas,too,onthepampasofPatagonia.

Heenjoyedhuntingrheas,andwatchingthegauchosbringthemdownbyentanglingabolasintheirlegs.Butwhenhetriedtodothesame,alhemanagedwastotripuphisownhorse.TheOriginmighthavevanishedfromhistory's

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timelinethenandthere,butDarwinsurvived,withonlyhispridehurt.Thegauchosfoundthewholethinghugelyamusing.

Charleseventookpartinsuppressinganinsurrection.WhentheBeaglereachedMontevideo,shortlyafterthecannonbalincident,FitzRoycomplainedtothelocalrepresentativeofHerMajesty'sRoyalNavy,whopromptlysetsailforBuenosAiresinhisfrigateHMSDruidtosecureanapology.Nosoonerhadthewarshipdisappearedfromviewthantherewasarebelion,withblacksoldierstakingoverthetown'scentralfort.ThechiefofpoliceaskedFitzRoyforhelp,andhedispatchedasquadoffiftysailors,armedtotheteeth...withDarwinhappilybringinguptherear.Themutineers

immediately

surrendered,

and

Darwin

expressed

disappointmentthatnotashothadbeenfired.

Noexpense,then,hasbeensparedtobringyouhistoricaltruth,inasmuchassoweightyacharacteristicastruthcanbeattributedtosomethingasetherealashistory.Exceptforthegiantsquid,ofcourse.Thathappenedinadifferenttimeline,whenthemalignforcesweregettingextremelydesperateandstrayedintoTwentyThousandLeaguesUndertheSeathroughsomeobscurewarpinL-space.

ThemostimportantsimilaritybetweenthetwoDarwinsislessexciting,butessentialtoourtale.TherealCharlesDarwin,likehisfictionalcounterpart,beganbywritingthewrongbook.Infact,hewroteeightwrongbooks.Theywereverynicebooks,veryworthy...ofgreatscientificvalue...andtheydidhisreputationnoharmatal....buttheyweren'taboutnaturalselection,histermforwhatlaterscientistswouldcalèvolution'.Stil,thatbookwasbrewingmerrilyawayinthebackofhismind,anduntilhewasreadytobringitoffthebackburner,hehadplentyofotherthingstowriteabout.

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IthadbeenFitzRoywhohadputtheideaofauthorshipintohishead.TheBeagle'scaptainhadsignedhimselfuptowritethestoryofhisround-the-worldvoyage,basedontheship'slog.Hehadalsoagreedtoeditanaccompanyingbookaboutaprevioussurveybythesamevessel-theonewhereStokeshadshothimself.AstheBeagleheadednorth-westfromCapetown,stoppedbrieflyatBahiainBrazil,andturnednorth-eastacrosstheAtlantictowardsitsfinaldestinationinFalmouth,FitzRoysuggestedtoDarwinthatthelatter'sdiarymightformthebasisofathirdvolumeonthenaturalhistoryofthevoyage,completingthetrilogy.

Darwinwasnervousbutexcitedattheprospectofbecominganauthor.Hehadanotherbookinmind,too,ongeology.He'dbeenthinkingaboutiteversincehisrevelationontheislandofStJago.

AssoonastheshiphadreturnedtoEngland,FitzRoygotmarriedandwentonhoneymoon,buthealsomadeanimpressivestarttohisbook.

Darwinbegantoworrythathisownslowwritingwoulddelaythewholeproject,butFitzRoy'searlyenthusiasmsoongroundtoahalt.BetweenJanuaryandSeptember1837Charlesworkedflatout,overtookthecaptain,andtowardstheyear'sendhesenthisfinishedmanuscripttotheprinter's.IttookFitzRoymorethanayeartocatchup,soDarwin'scontributionwasheldback,finalyseeingthelightofdayin1839asvolume3oftheNarrativeoftheSurveyingVoyagesofHMS.AdventureandBeagle,BetweentheYears1826and1836,withthesubtitleVolume3:JournalandRemarks,1832-1836.AfterafewmonthsthepublishersreissueditonitsownasjournalofResearchesintotheGeologyandNaturalHistoryoftheVariousCountriesVisitedbyH.M.S.Beagle.Itmayhavebeenthewrongbook,

butwritingithadoneveryusefuleffectonDarwin'sthinking.Itforcedhimtotrytomakesenseofalthethingshehadseen.Wastheresomeoverarchingprinciplethatcouldexplainital?

Nextcamehisgeologybook,whicheventualyturnedintothree:oneoncoralreefs,oneonvolcanicislands,andoneonthegeologyofSouthAmerica.TheseestablishedhisscientificcredentialsandledtohimwinningamajorRoyalSocietyprize.Darwinwasnowrecognisedasoneoftheleadingscientistsintheland.

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Hewasalsomakingevermoreextensivenotesonthetransmutationofspecies,buthestilwasinnohurrytopublish.Quitethecontrary.

Elsewhere,politicalforceswereatworkaimingtodestroytheinfluenceoftheChurch,andoneoftheirkeypointswasthatlivingcreaturescouldeasilyhavearisenwithouttheinterventionofacreator.Darwin,being(atthatpointinhislife)agoodChristian,wastotalyaversetoanythingthatmightseemtoalyhimwithsuchpeople.HecouldnotpubliclyespousetransmutationwithoutriskingseriousdamagetotheAnglicanChurch,andnothingintheworldwouldinducehimtocontemplatethat.Buthisdeepinsightaboutnaturalselectionwouldn'tgoaway,sohecontinueddevelopingitasakindofhobby.

Hedidmentiontheinsighttovariousscientificfriendsandacquaintances,amongthemLyel,andalsoJosephDaltonHooker,whodidn'tdismisstheideaoutofhand.ButhedidtelDarwin,Ìshalbedelightedtohearhowyouthinkthischangemayhavetakenplace,asnopresentlyconceivedopinionssatisfymeonthissubject.'Andhelatersaid,ratheracerbicaly,that`Noonehashardlyarighttoexaminethequestionofspecieswhohasnotminutelyexaminedmany.'Darwintookthisadvicetoheartandcastaroundfornewspeciestobecomeanexperton.In1846hesentthefinalproofsofhisgeologybooksbacktotheprinterandcelebratedbycolectingthelastbottleofpreservedspecimensfromtheBeaglevoyage.

AtthetopofthebottlehenoticedacrustaceanfromtheChonosArchipelago-abarnacle.

Thatwoulddo.Itwasasgoodasanythingelse.

HookerhelpedDarwinsetuphismicroscopeandmakesomepreliminaryanatomicalobservations.DarwinaskedHookertonamethenewbeast,andtogethertheydecidedonArthrobalanus.[1]`MrArthrobalanus',astheyprivatelycaledit,turnedouttobesomewhatunusual.ÌbelieveArthrobalanushasnoovisacatal!'Charleswrote.`Theappearanceofoneisentirelyowingtothesplitting&tuckingupoftheposteriorpenis.'Toresolvethemysteryhetookotherbarnaclesfromthebottleandlookedatthem,too.Nowhewasdoingcomparativeanatomyofbarnacles,andenjoyingthehands-onexperienceimmensely.Thiswasbetterthanwriting.

ByChristmashehaddecidedtostudyeverybarnacleknowntohumanity-

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theentireorderofCirripedia.Whichturnedouttoberatheralot,sohesettledfortheBritishones.Eventhesewereratheralot,andintheendthetasktookeightyears.

Hemighthavefinishedearlier,butin1848hegotinterestedinbarnaclesex,andthatwasverypeculiarindeed.Mostbarnacleswerehermaphrodites,abletoassumeeithersex.Butsomespecieshadgoodold-fashionedmalesandfemales.Exceptthatthemalesspentmuchoftheirlivesembeddedinthefemales.

Notonlythat:somesupposedlyhermaphroditespeciesalsohadtinymalesthatsomehowassistedinthereproductiveprocess.

NowDarwinbecameveryexcited,becausehehadconvincedhimselfthatwhathewasobservingwasarelicofevolution,asahermaphroditeancestorgradualydevelopedseparatesexes.Àmissinglink'forbarnaclesex.Hecouldreconstructthebarnacles'familytree,andwhathethoughthesawreinforcedhisviewsonnaturalselection.Soevenwhenhetriedtodorespectablescience,andbecomeataxonomist,transmutationinsistedingettinginontheact.Infact,ifanythingconvincedDarwinhewasrightabouttransmutation,itwasbarnacles.

[1].Literaly,'jointedacorn'

Hebecameil,butcontinuedworkingonbarnacles.In1851hepublishedtwobooksaboutthem-oneonfossilbarnaclesforthePalaeontographicalSociety,theotheronthelivingonesfortheRoyalSociety.By1854hehadproducedasequeltoeachofthem.

ThesewereDarwin'seightwrongbooks:1839JournalofResearchesintotheGeologyandNaturalHistoryoftheVariousCountriesVisitedbyH.M.S.Beagle1842TheStructureandDistributionofCoralReefs1844GeologicalObservationsontheVolcanicIslandsVisitedDuringtheVoyageofH.M.S.Beagle

1846GeologicalObservationsofSouthAmerica1851AMonographontheFossilLepadidae,or,PedunculatedCirripedesofGreatBritain

1851AMonographontheSub-classCirripediavolume1

1854AMonographontheFossilBalanidaeandVerrucidaeofGreatBritain

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1854AMonographontheSub-classCirripediavolume2

Notahintoftransmutationofspecies,thestruggleforlife,ornaturalselection.

Yet,inastrangeway,alofhisbooks-eventhegeologicalones-werecrucialstepstowardstheworkthatwasnowputtingitselftogetherinsidehishead.Darwin'sninthbookwouldbepuredynamite.Hewanteddesperatelytowriteit,buthehadalreadydecidedthatitwouldbefartoodangeroustobepublished.

Itisacommondilemmainscience:whethertopublishandbedamned,ornottopublishandbepre-erupted.Youcanhavethecreditforatrulyrevolutionaryidea,oraquietlife,butnotboth.

Darwinwaswaryofpublicity,andhewasscaredthatputtinghisviewsintoprintmightdamagetheChurch.Butthereisnothingthatmoreeffectivelygalvanisesascientistthanthefearthatsomebodyelsewilpipthemtothewinningpost.Inthiscase,thatsomebodywasAlfredRusselWalace.

WalacewasanotherVictorianexplorer,equalykeenonnaturalhistory.

Mostlybecausehecouldselit.UnlikeDarwin,hewasnot`gentry',andhadnoindependentincome.Hewasthesonofanimpecuniouslawyer[1]andhadbeentakenonatagefourteenasabuilder'sapprentice.HespenthiseveningsdrinkingfreecoffeeintheHalofScienceoffTottenhamCourtRoadinLondon.Thiswasasocialistorganisation,dedicatedtotheoverthrowofprivatepropertyandthedownfaloftheChurch.Walace'sexperiencesasayouthreinforcedaleftwingviewofpolitics.Hefinancedhisowntravels,andmadealivingbyselingthespecimenshecolected-

butterflies,beetles(athousandlabeledspecimensperbox,thedealersdemanded),[2]evenbirdskins.HewentonacolectingexpeditiontotheAmazonin1848,andagaintotheMalayArchipelagoin1854.There,inBorneo,hesoughtorang-utans.Theideathathumansweresomehowrelatedtothegreatapeswassimmeringawayinthecolectivesubconscious,andWalacewantedtoinvestigateapotentialhumanancestor.[3]

OnemiserableBorneoday,whenatropicalmonsoonragedoutsideandWalacewasstuckindoors,heputtogetheralittlescientificpaperoutliningsomemodestideasthathadjustpoppedintohishead.IteventualyappearedintheAnnalsandMagazineofNaturalHistory,aratherordinarypublication,anditwasaboutthe

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'introduction'ofspecies.Lyel,awareofDarwin'ssecretinterestinsuchmatters,pointedthepaperouttohim,andCharlesbegantoreadit.ThenanotherofCharles'sregularcorrespondents,EdwardBlyth,

[1]Yes,weknowitsoundsunlikely,butapparentlytherearesuchthings.

[2]ItwasagoodjobthatGodhadsuchafondnessforbeetles.

[3]ItspotentialforLibrarianshipwasnotwidelyrecognisedatthattime.

wrotefromCalcuttawiththesamerecommendation.`WhatdoyouthinkofWalace'spaperintheAnnM.N.H.?Good!Uponthewhole!'DarwinhadmetWalaceshortlybeforeoneofthelatter'sexpeditions-hecouldn'trememberwhich-andhecouldseethattheAnnM.N.H.paperhadusefulthingstosayaboutrelationshipsbetweensimilarspecies.Especialytheroleofgeography.Butapartfromthat,hefeltthatthepapercontainednothingnew,andmadeanentrytothateffectinoneofhisnotebooks.

Anyway,itseemedtoDarwinthatWalacewastalkingaboutcreation,notevolution.Nevertheless,hewrotetoWalace,encouraginghimtocontinuedevelopinghistheory.

ThiswasaRealyBadIdea.

EncouragedbyLyelandothers,whowerenowwarninghimthatifhedelayedtoolong,othersmightsnatchtheprize,Darwinwasputtingtogetherevermoreelaborateessaysonnaturalselection,buthecontinuedtoditheraboutpublication.AlthatchangedinaninstantinJune1858,whenthepostmandroppedabombshelthroughCharles'sletterbox.ItwasapackagefromWalace,containingatwenty-pageletter,sentfromtheMoluccas.WalacehadtakenDarwin'sadvicetoheart.Andhehadcomeupwithaverysimilartheory.Verysimilarindeed.

Calamity.Darwindeclaredthathislife'sworkwas`smashed'.`Yourwordshavecometruewithavengeance,'hewrotetoLyel.ThemorehereadWalace'snotes,theclosertheideasseemedtohisown.ÌfWalacehadmyMSmanuscriptsketchwrittenoutin1842,hecouldnothavemadeabettershortabstract!'DarwinmoanedinalettertoLyel.

StaidVictorianswouldsoonconsiderbothWalaceandDarwintobeoutoftheir

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minds,andWalacecertainlycameclose,forhewassufferingfrommalariawhenhecomposedhislettertoDarwin.Asagoodsocialist,WalacehadbeentaughtnottotrustthereasoningofMalthus,whohadarguedthattheworld'sabilitytofeeditselfgrewlinearly,whilethepopulationgrewexponentialy-implyingthateventualythepopulationwouldwinandtherewouldbetoolittlefoodtogoround.Socialistsbelievedthathumaningenuitycouldpostponesuchaneventindefinitely.

Butbythe1850sevensocialistswerebeginningtoviewMalthusinamorefavourablelight;afteral,thethreatofoverpopulationwasaverygoodreasontopromotecontraception,whichmadeexcelentsensetoeverygoodsocialist.Half-deliriouswithfever,Walacethoughtabouttherichvarietyofspecieshehadencountered,wonderedhowthatfittedinwithMalthus,puttwoandtwotogether,andrealisedthatyoucouldhaveselectivebreedingwithouttheneedforabreeder.

Asitturnedout,hedidn'thavequitethesameviewasDarwin.Walacethoughtthatthemainselectivepressurecamefromthestruggletosurviveinahostileenvironment-drought,storm,flood,whatever.Itwasthisstrugglethatremovedunfitcreaturesfromthebreedingpool.Darwinhadaratherblunterviewoftheselectionmechanism:competitionamongtheorganismsthemselves.Itwasn'tquitèNatureredintoothandclaw'asTennysonhadwritteninhisInMemoriamof1850,buttheclawswereunsheathedandtherewasacertainpinknesstotheteeth.ToDarwin,theenvironmentsetabackgroundoflimitedresources,butitwasthecreaturesthemselvesthatselectedeachotherforthechopwhentheycompetedforthoseresources.Walace'spoliticalleaningsmadehimdetectapurposeinnaturalselection:tòrealisetheidealofaperfectman'.

Darwinrefusedeventocontemplatethiskindofutopianhogwash.

Walacehadn'tmentionedpublishinghistheory,butDarwinnowfeltobligedtorecommendittohim.AtthatpointitlookedasifCharleshadcompoundedhisRealyBadidea,butforoncetheuniversewaskind.Lyel,searchingforacompromise,suggestedthatthetwomenmightagreetopublishtheirdiscoveriessimultaneously.Darwinwasconcernedthatthismightmakeitlookasifhe'dpinchedWalace'stheory,worriedhimselftodistraction,andfinalyhandedthenegotiatingovertoLyelandHookerandwashedhishandsofit.

Fortunately,Walacewasatruegentleman(theaccidentofbreeding

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notwithstanding)andheagreedthatitwouldbeunfairtoDarwintodoanythingelse.Hehadn'trealisedthatDarwinhadbeenworkingonexactlythesametheoryformanyyears,andhehadnowishtostealsuchaneminentscientist'sthunder,perishtheverythought.Darwinquicklyputtogetherashortversionofhisownwork,andHookerandLyelgotthetwopapersinsertedintothescheduleoftheLinnaeanSociety,arelativelynewassociationfornaturalhistory.TheSocietywasabouttoshutupshopforthesummer,butthecouncilfittedinanextrameetingatthelastminute,andthetwopapersweredulyreadtoanaudienceofaboutthirtyfelows.

Whatdidthefelowsmakeofthem?ThePresidentreportedlaterthat1858

hadbeenaratherdulyear,not`markedbyanyofthosestrikingdiscoverieswhichatoncerevolutionise,sotospeak,ourdepartmentofscience'.

Nomatter.Darwin'sfearofcontroversywasnowirrelevant,becausethecatwasoutofthebag,andtherewasnochancewhatsoeverthatthebeastcouldbestuffedbackin.Yet,asithappened,theanticipatedcontroversydidn'tquitematerialise.ThemeetingoftheLinnaeanSocietyhadbeenrushed,andthefelowshaddepartedmutteringvaguelyundertheirbreaths,feelingthattheyoughttobeoutragedbysuchblasphemousideas...yetpuzzledbecausetheenormouslyrespected(andrespectable)HookerandLyelclearlyfeltthatbothpapershadsomemerit.

Andtheideasstruckhomewithsome.Inparticular,theVicePresidentpromptlyremovedalmentionofthefixityofspeciesfromapaperhewasworkingon.

NowthatDarwinhadbeenforcedtoputhisheadabovetheparapet,hewouldlosenothingbypublishingthebookthathehadpreviouslydecidednottowrite,buthadconstantlybeenthinkingaboutanyway.Hehadintendedittobeavast,multi-volumetreatisewithextensivereferencestoscientificliterature,examiningeveryaspectofhistheory.ItwasgoingtobecaledNaturalSelection(aconsciousorsubconsciousreferencetoPaley'sNaturalTheology?).Buttimewaspressing.Hepolisheduphisexistingessay,changingthetitletoOntheOriginofSpeciesandVarietiesbyMeansofNaturalSelection.Then,ontheinsistentadviceofhispublisherJohnMurray,hecutouttheàndVarieties'.Thefirstprintrunof1250

copieswentonsaleinNovember1859.DarwinsentWalaceacomplimentary

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copy,withanote:`Godknowswhatthepublicwilthink.'

Intheevent,thebooksoldoutbeforepublication.Over1500advanceorderscameinforthose1250copies,andDarwinpromptlystartedworkingonrevisionsforasecondedition.CharlesKingsley,authorofTheWater-Babies,countryrector,andChristiansocialist,lovedit,andwrotealavishletter:ÌtisjustasnobleaconceptionofDeity,tobelievethatHecreatedprimalformscapableofselfdevelopment...astobelievethatHerequiredafreshactofinterventiontosupplythelacunas[1]whichHehimselfhadmade.'Kingsleywassomethingofamaverick,becauseofhissocialistviews,sopraisefromthissourcewassomethingofapoisonedchalice.

Thereviews,steadfastintheirChristianorthodoxy,weredistinctlylessfavourable.EventhoughOriginhardlymentionshumanity,altheusualcomplaintsaboutmenandmonkeys,andinsultstoGodandHisChurch,weretrottedout.Whatparticularlygaledthereviewerswasthatordinarypeoplewerebuyingthething.Itwasalrightfortheupperclassestotoywithradicalviews,ithadanattractivefrissonofnaughtinessandwasperfectlyharmlessamonggentlemenofbreeding,thoughnotladiesofcourse;butthosesameviewsmightputideasintothecommonfolk'sheads,iftheywereexposedtothem,andupsettheestablishedorder.ForHeaven'ssake,thebookwasevenselingtocommutersoutsideWaterloorailwaystation!Itmustbesuppressed!

[1]No,notlong-hairedSouthAmericanbeastsofburden,butLatinfor`gaps'.

Toolate.Murraygeareduptoprint3000copiesofthesecondedition,whoselikelysaleswerenotgoingtosufferfrompubliccontroversy.AndthepeoplewhomatteredmosttoDarwin-Lyel,Hooker,andtheanti-religiousèvangelist'ThomasHenryHuxley-wereimpressed,andprettymuchconvinced.WhileCharlesstayedoutofthepublicdebate,Huxleysettowithawil.Hewasdeterminedtoadvancethecauseofatheism,andOrigingavehimapointofleverage.Theradicalatheistslovedthebook,ofcourse:itsoveralmessageandscientificweightinesswereenoughforthem,andtheyweren'ttooconcernedaboutfinepoints.HewettWatsondeclaredDarwintobèthegreatestrevolutionistinnaturalhistoryofthiscentury'.

IntheintroductiontoOrigin,Darwinbeginsbytelinghisreadersthebackgroundtohisdiscovery:

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WhenonboardH.M.S.Beagle,asnaturalist,Iwasmuchstruckwithcertainfacts,inthedistributionoftheinhabitantsofSouthAmerica,andinthegeologicalrelationsofthepresenttothepastinhabitantsofthatcontinent.

Thesefactsseemedtometothrowsomelightontheoriginofspecies-

thatmysteryofmysteries,asithasbeencaledbyoneofourgreatestphilosophers.Onmyreturnhome,itoccurredtome,in1837,thatsomethingmightperhapsbemadeoutofthisquestionbypatientlyaccumulatingandreflectingonalsortsoffactswhichcouldpossiblyhaveanybearingonit.

Apologisingprofuselyforlackofspace,andtime,towritesomethingmorecomprehensivethanhis150,000-wordtome,Darwinthenmovestowardsashortsummaryofhismainidea.Writersonsciencegeneralyappreciatethatitisseldomenoughtodiscusstheanswertoaquestion:itisalsonecessarytoexplainthequestion.Andthat,ofcourse,shouldbedonefirst.

Otherwiseyourreaderswilnotappreciatethecontextintowhichtheanswerfits.Darwinwasclearlyawareofthisprinciple,sohebeginsbypointingoutthat:

Itisquiteconceivablethatanaturalist,reflectingonthemutualaffinitiesoforganicbeings,ontheirembryologicalrelations,theirgeographicaldistribution,geologicalsuccession,andothersuchfacts,mightcometotheconclusionthateachspecieshadnotbeenindependentlycreated,buthaddescended,likevarieties,fromotherspecies.Neverthelesssuchaconclusion,evenifwelfounded,wouldbeunsatisfactory,untilitcouldbeshownhowinnumerablespeciesinhabitingthisworldhavebeenmodified,soastoacquirethoseperfectionsofstructureandcoadaptationwhichmostjustlyexcitesouradmiration.

AlreadyweseeagesturetowardsPaley-'perfectionsofstructure'isaclearreferencetothewatch/watchmakerargument,and`hadnotbeenindependentlycreated'showsthatDarwindoesn'tbuyPaley'sconclusion.

ButwealsoseesomethingthatcharacterisesthewholeofOrigin:Darwin'swilingnesstoacknowledgedifficultiesinhistheory.Timeandagainheraisespossibleobjections-notasstrawmen,tobeknockedflatagain,butasseriouspointstobeconsidered.Morethanonceheconcludesthatthereismoretobelearned,beforetheobjectioncanberesolved.Paley,tohiscredit,didsomethingsimilar,thoughhedidn'tgoasfarasadmittingignorance:heknewthathewas

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right.Darwin,arealscientist,notonlyhadhisdoubts-hesharedthemwithhisreaders.Hewouldnothavearrivedathistheorytobeginwithifhehadfailedtoseektheweaknessesofthehypothesesuponwhichitwasbased.

Healso,ofcourse,makesitclearwhathisownworkisaddingtothespeculationsofearlier'transmutationists'.Namely:hehascomeupwithamechanismforspecieschange.Thereareadvantagesinbeinghonestabout,yourownlimitations:yougaintherighttotalkaboutthelimitationsofothers.Andnowhetelsuswhatthatmechanismis.Species,weknow,arevariable-thedomesticationofwildspecieslikechickens,cows,anddogsisclearevidenceofthat.Althoughthatisdeliberateselectionbyhumans,itopensthedoortoselectionbynaturewithouthumanaid:

Iwilthenpassontothevariabilityofspeciesinastateofnature...Weshal,however,beenabledtodiscusswhatcircumstancesaremostfavourabletovariation.InthenextchaptertheStruggleforExistenceamongstalorganicbeingsthroughouttheworld,whichinevitablyfolowsfromtheirhighgeometricalpowersofincrease,wilbetreatedof...ThefundamentalsubjectofNaturalSelectionwilbetreatedatsomelengthinthefourthchapter;andweshalthenseehowNaturalSelectionalmostinevitablycausesmuchExtinctionofthelessimprovedformsoflife,andinduceswhatIhavecaledDivergenceofCharacter.

Hethenpromisesfourchapterson`themostapparentandgravestdifficultiesofthetheory',prominentamongthesebeingtounderstandhowasimpleorganismororgancanchangeintoahighlycomplexone-

anothernodtoPaley.Theintroductionendswithaflourish:Icanentertainnodoubt...thattheviewwhichmostnaturalistsentertain,andwhichIformerlyentertained-namely,thateachspecieshasbeenindependentlycreated-iserroneous.Iamfulyconvincedthatspeciesarenotimmutable;butthatthosebelongingtowhatarecaledthesamegeneraarelinealdescendentofsomeotherandgeneralyextinctspecies...Furthermore,IamconvincedthatNaturalSelectionhasbeenthemainbutnotexclusivemeansofmodification.

Inessence,Darwin'stheoryofnaturalselection,whichsoonbecameknownasevolution,[1]isstraightforward.Mostpeoplethinkthey[1]ThetermwasaroundinVictoriantimes,asaphenomenonbutnotaspecificmechanism.Darwindidn'tuseitinOrigin,norinthelaterTheDescentofMan.However,thefinalwordin

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Originis'evolved'.

understandit,butitssimplicityisdeceptive,anditssubtletiesareeasilyunderestimated.Manyofthestandardcriticismsofevolutionarytheorystemfromcommonmisunderstandings,notfromwhatthetheoryactualyproposes.Theongoingscientificdebateaboutdetailsisoftenmisrepresentedasdisagreementwiththegeneraloutline,whichisanerrorbasedontoosimple-mindedaviewofhowsciencedevelopsandwhat`knowledge'is.

Briefly,Darwin'stheorygoeslikethis.

1.Organisms,eventhoseinthesamespecies,arevariable.Somearebiggerthanothers,orbolderthanothers,orprettierthanothers.

2.Thisvariabilityistosomeextenthereditary,passedontooffspring.

3.Uncheckedpopulationgrowthwouldquicklyexhaustthecapacityoftheplanet,sosomethingchecksit:competitionforlimitedresources.

4.Thereforeastimepasses,theorganismsthatdosurvivelongenoughtobreedwilbemodifiedinwaysthatimprovetheirchanceofsurvivingtobreed,aprocesscalednaturalselection.

5.Ongoingslowchangescanlead,inthelongrun,tobigdifferences.

6.Thelongrunhasbeenverylongindeed-hundredsofmilionsofyears,maybemore.Sobynowthosedifferencescanhavebecomehuge.

It'srelativelysimpletoputthesesixingredientstogetheranddeducethatnewspeciescanarisewithoutdivineintervention-providedwecanjustifyeachingredient.

Eventhoughdifferentspeciesseemtostayprettymuchthesame-thinklions,tigers,elephants,hippos,whatever-itisactualyratherobviousthat,ingeneral,speciesarenotfixedforaltime.Thechangesarerelativelyslow,whichiswhywedon'tnoticethem.Buttheydohappen.We'vealreadyseenthatinDarwin'sfinches,evolutionarychangescanbeandhavebeenobservedonatimescaleofyears,andinbacteriatheyoccuronatimescaleofdays.

Themostobviousevidenceforthevariabilityofspecies,inDarwin'sdayand

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ours,wasthedomesticationofanimals-sheep,cows,pigs,chickens,dogs,cats...

...andpigeons.Darwinwasratherknowledgeableaboutpigeons,hebelongedtotwoLondonpigeonclubs.Everypigeon-fancierknowsthatbyselectivelybreedingparticularcombinationsofmaleandfemalepigeons,itispossibletoproducèvarieties'ofpigeonswithparticularcharacteristics.`Thediversityofthebreedsissomethingastonishing,'

saysDarwininthefirstchapterofOrigin.TheEnglishcarrierpigeonhasawidemouth,largenostrils,elongatedeyelids,alongbeak.Theshort-facedtumblerhasashortstubbybeaklikeafinch.Thecommontumblerflieshighupinatightlyknitflock,andhasanoddhabitoffalingaboutinthesky,whenceitsname.Therunt(despiteitsname)ishuge,withalongbeakandlargefeet.Thebarbislikethecarrierbutwithashort,broadbeak.Thepouterhasaninflatablecropandcanpuffoutitschest.Theturbithasashortbeakandalineofreversedfeathersonitschest.TheJacobinhassomanyreversedfeathersonitsneckthattheyformahood.Thentherearethetrumpeter,laugher,fantail...Thesearenotseparatespecies:theycaninterbreed,toproduceviablèhybrids'-cross-breeds.

Theenormousvarietyofdogsissowelknownthatwedon'tevenneedtomentionexamples.It'snotthatthedogspeciesisexceptionalymaleable,justthatdog-breedershavebeenunusualyactiveandimaginative.Thereisadogforeverypurposethatadogcancarryout.Again,they'realdogs,notnew(albeitrelated)species.Theycanmostly(barringrealybigsizedifferences)interbreed,andartificialinseminationcantakecareofmeresize.Dogspermplusdogeggmakesfertiledogzygote,and,eventualy,dog-independentlyofbreed.That'swhypedigreepoochesneedapedigree,toguaranteethattheirparentageispure.Ifthedifferentvarietiesofdogweredifferentspecies,thatwouldn'tbenecessary.

Inmodemtimes,ithasbecomeclearthatcatsarejustasmaleable,butthecat-breedershaveonlyjustgotgoingonexoticcats.Thesamegoesforcows,pigs,goats,sheep...andwhataboutflowers?Thenumberofvarietiesofgardenflowersisimmense.

Byavoidingthecreationofhybrids,thebreedercanmaintaintheindividualvarietiesovermanygenerations.Pouterpigeonsbreedwithpouterstoproduce(asubstantialproportionof)pouters.Carriersmatedwithcarriersproduce(mostly)carriers.Theunderlyinggenetics,aboutwhichDarwinandhiscontemporaries

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knewnothing,iscomplicatedenoughthatapparenthybridscansometimesarisefromwhatseemstobepurestock,justastwobrown-eyedparentscannonethelesshaveablue-eyedchild.

Sopigeon-breedershavetoeliminatethehybrids.

Theexistenceofthesecross-bredvarietiesdoesnot,ofitself,explainhownewspeciescanariseoftheirownaccord.Varietiesarenotspecies;moreover,theguidinghandofthebreederisevident.Butvarietiesdomakeitclearthattheremustbeplentyofvariabilitywithinaspecies.Infact,thevariabilityissogreatthatonecanreadilyimagineselectivebreedingleadingtoentirelynewspecies,givenenoughtime.Andtheavoidanceofhybridscanmaintainvarietiesfromonegenerationtothenext,sotheircharacters(biologeseforthefeaturesthatdistinguishthem)areheritable(biologeseforàbletobepassedfromonegenerationtothenext').SoDarwinhashisfirstingredient:heritablevariability.

Thenextingredientwaseasier(thoughstilcontroversialinsomequarters).

Itwastime.Oodlesandoodlesoftime,theDeepTimeofgeologists.Notafewthousandyears,butmilions,tensofmilions...bilions,infact,thoughthatwasfurtherthantheVictorianswerewilingtogo.DeepTime,aswe'vepreviouslyobserved,iscontrarytothebiblicalchronologyofBishopUssher,whichiswhytheidearemainscontroversialamongcertainChristianfundamentalists,whohavebizarrelychosentofighttheircornerontheweakestofgrounds,completelyneedlessly.DeepTimeissupportedbysomuchevidencethatatrulycommittedfundamentalisthastobelievethathisGodisdeliberatelytryingtofoolhim.Worse,ifwecan'ttrusttheevidenceofourowneyes,thenwecan'ttrusttheapparentelementof`design'inlivingcreatureseither.Wecan'ttrustanything.

LyelrealisedthattheageoftheEarthmustbemanymilionsofyears,whenhelookedatsedimentaryrocks.Thesearerockslikelimestoneorsandstonewhichforminlayers,andhavebeendepositedeitherunderwater,asmuddysediments,orindeserts,asaccumulatingsand.

(Independentevidencefortheseprocessescomesfromthefossilsfoundinsuchrocks.)Bystudyingtherateatwhichmodernsedimentsaccumulate,andcomparingthatwiththethicknessofknownbedsofsedimentaryrock,Lyelcouldestimatethetimeithadtakenforthelayersofrocktobedeposited.Somethingintherange1000-10,000yearswouldproducealayeraboutametre

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thick.Butthechalkcliffsofthesouthcoast,aroundDover,arehundredsofmetresthick.Sothat'sseveralhundredthousandyearsofdeposition,andwe'veonlydealtwithoneofthenumerouslayersofrockthatmakeupthegeologicalcolumn-thehistoricalsequenceofdifferentrocks.

Wenowhavemanyotherkindsofevidenceforthegreatageofourplanet.

Therateofdecayofradioactiveelements,whichwecanmeasuretodayandextrapolatebackwards,isingeneralagreementwiththeevidenceoftherocklayers.Therateofmovementofthecontinents,whencombinedwiththedistancestheyhavemoved,isagainconsistentwithotherestimates.We'veseenthatIndiawasonceattachedtoAfrica,butabout200milionyearsagoitbrokeoff,andby40milionyearsagoithadmovedalthewaytoitscurrentposition,buttingupagainstAsiaandpushinguptheHimalayas.

Whencontinentsmoveapart-asAfricaandSouthAmerica,orEuropeandNorthAmerica,aredoingnow-newmaterialformsontheoceanfloor,flowingoutfromthemantlebeneathtoformhugemid-oceanridges.TherocksintheridgescontainarecordofthechangesintheEarth'smagneticfield,`frozenin'astherockcooled.Theyshowalongseriesofrepeatedreversalsofthefieldpolarity.Sometimesthènorth'magneticpoleisatthenorthernendoftheEarth,asnow,buteverysooftenthepolarityflips,sothatthemagneticpolenearthenorthernendisthèsouth'one.

MathematicalmodelsoftheEarth'smagneticfieldpredictthatsuchreversalsoccurroughlyonceeveryfivemilionyears.Countthenumberofreversalsintheocean-ridgerocks,multiplybyfivemilion...again,thenumbersfitreasonablywel,andcarefulcomparisonsandalotofdisputationbyexpertsleadtorevisednumbersthatfitevenbetter.

TheGrandCanyonisadeepgashthroughlayersofrockonemile(1.6km)thick.Youhaveachoice.Youcanunderstandwhattherecordoftherocksistelingyouhere:ittookaverylongtimetolaydownthoserocks,andquitealongtime-thoughless-forflashfloodingintheColoradorivertoerodethemagain.Oryoucanfolowonebookthatuntilrecentlywasdisplayedinthèscience'sectionoftheGrandCanyonbookstore,untilalotofscientistscomplained,andassertthattheGrandCanyonisevidenceforNoah'sflood.Thefirstchoicefitshugeamountsofevidenceandgeologicalunderstanding.Thesecondisanexcelenttestoffaith,becauseitfitsabsolutelynothing.Afloodthatlastedonly40days

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couldneverhaveproducedthatkindofgeologicalformation.Amiracle?Inthatcase,theSaharadesertcouldequalywelbehailedasevidenceforNoah'sflood,miraculouslynotformingadeepcanyon.Onceyouadmitmiracles,youcan'tpursuealogicalthread.

Anyway,that'sthesecondingredient-DeepTime.Ittakeshugeamountsoftimetochangeorganismsintoentirelynewspecies,ifalyoucando-asDarwinbelieved-ismakeverygradualchanges.ButevenDeepTime,whencombinedwithheritablevariation,isnotenoughtoleadtothekindoforganised,coherentchangesthatareneededtocreatenewspecies.

Therehastobeareasonforsuchchangestooccur,aswelasopportunityandtime.Darwin,aswe'veseen,foundhisreasoninMalthus'scontentionthattheuncheckedgrowthoforganismsisexponential,whereasthatofresourcesislinear.Inthelongrun,exponentialgrowthalwayswins.

Thefirstassertionisprettymuchcorrect,thesecondhighlydebatable.Thequalifierùnchecked'iscrucial,andrealpopulationsonlygrowexponentialyifthereareplentyofresourcesavailable.Typicaly,thegrowthstartsexponentialywithasmalpopulationandthenlevelsoffasthepopulationsizeincreases.Butinmostspecies,twoparents(let'sthinksexualspecieshere)producesomelargernumberofoffspring.Abreedingfemalestarlinglaysabout16eggsinherlife,andwithùnchecked'growth,thestarlingpopulationwouldmultiplyby8everylifetime.Itwouldnotbelongbeforetheplanetwasknee-deepinstarlings.So,ofnecessity,14ofthose16offspring(onaverage)failtobreed-usualybecausesomethingeatsthem.Justtwobecomeparentsintheirturn.Afemalefrogmaylay10,000eggsinherlife,andnearlyaldieinvariousgrotesquewaystoachieveeachtwoparents;afemalecodcontributesfortymilionorthereaboutsofheroffspringtoplanktonicfoodchains,foreachtwothatbreed.Herethemultiplier,withùnchecked'growth,wouldbe20milionpercod-lifetime.Uncheckedgrowthsimplydoesn'tbearthinkingaboutasarealisticprospect.

WesuspectthatMalthusplumpedforlineargrowthofresourcesforaslightlysilyreason.Victorianschool-textbookmathematicsdistinguishedtwomaintypesofsequence:geometric(exponential)andarithmetic(linear).Therewereplentyofotherpossibilities,buttheydidn'tgetintothetextbooks.Havingalreadyassignedgeometricgrowthtoorganisms,Malthuswasleftwitharithmeticgrowthforresources.Hismainpointdoesn'tdependontheactualgrowthrate,inanycase,aslongasitislessthanexponential.Asthestarlingexampleshows,

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mostoffspringdiebeforebreeding,andthat'sthemainpointhere.

Giventhatmostyoungstarlingscannotpossiblybecomeparents,thequestionarises:whichoneswil?Darwinfeltthattheonesthatsurvivedtobreedwouldbetheonesbestsuitedforsurvival,whichmakessense.Ifonestarlingisbetteratfindingfood,orhangingontoit,thananotherone,thenit'sclearwhichoneismorelikelytodobestiffoodsuppliesbecomelimited.Thebetteronemightbeunluckyandgeteatenbyahawk;butacrossthepopulation,starlingsthatarebetterequippedtosurvivearegeneralytheonesthatdosurvive.

Thisprocessof`naturalselection'ineffectplaystheroleofanexternalbreeder.Itchoosescertainorganismsandeliminatestherest.Thechoiceisnotconscious-thereisnoconsciousnesstodothechoosing,andnopreconceivedpurpose-buttheendresultisverysimilar.Themaindifferenceisthatnaturalselectionmakessensiblechoices,whereashumanselectioncanmakeridiculousones(likedogswithfacessoflattenedtheycanhardlybreathe).Sensiblechoicesleadtosensibleanimalsandplants,onesthatarebeautifulyadaptedforsurvivalinwhateverenvironmenttheyhappenedtobeinwhennaturalselectionwasmouldingthem.

Itisjustlikebreedingnewvarietiesofpigeon,butwithoutahumanbreeder.Naturalselectionexploitsthesamevariabilityoforganismsthatpigeon-breedingdoes.Itmakeschoicesbasedonsurvivalvalue(insomeenvironment)ratherthanwhim.Itistypicalymuchslowerthanhumanintervention,butthetimescaleissovastthatthisslownessdoesn'tmattermuch.Heritablevariationplusnaturalselectioninevitablylead,overDeepTime,totheoriginationofspecies.

Naturedoesitalonherown.Thereisnoneedforaseriesofactsofspecialcreation.Thatdoesn'timplythatspecialcreationhasnotoccurred.

Itjustremovesanylogicalimperativeforit.

Paleywaswrong.

Thewatchesdon'tneedawatchmaker.

Theycanmakethemselves.

THIRTEEN

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INFINITYISABITTRICKY

ITWASJUSTGONEHALFfiveinthemorning,toolateforNibblesandyetnottimeforEarlyBreakfast.Joggingthroughthegreymist,ArchchancelorRidculysawthelightsonintheGreatHal.SteelinghimselfincasePonderhadstudentsinthere,hepushedopenthedoor.

Therewereafewstudentsaround.Oneofthemwasasleepunderthecoffeespigot.

PonderStibbonswasstilonthestepladder,wavinghishandsthroughthetimelines.

`Gettinganywhere,Stibbons?'saidRidculy,runningonthespot.

Pondermanagedtosteadyhimselfjustintime.

Èr...generalprogress,sir,'hesaid,andclimbeddown.

`Bitofabigjob,eh?'saidRidculy.

`Rathertaxing,sir,yes.We'vedonetheinstructions,though.We'renearlyready.'

`Hit'emhard,that'sthestyle,'saidRidculy,punchingtheair.

`Quiteprobably,sir,'saidPonder,yawning.

ÌwasthinkingwhileIwasrunning,Stibbons,asismywont,'saidRidculy.

It'sgoingtobeabouttheeyebal,isn'tit,Ponderthought.I'mprettygoodontheeyebalnow,butthenhe'laskabouttheparasiticwaspandthat'sapuzzler,andthenhe'laskhowexactlyisevolutionpassedonandthere'sagod-spacerightthere.Andthenhe'laskhowdoyougetfromablobintheoceantopeoplebyaddingnothingbutsunlightandtime?Andhe'lprobablysay:peopleknowthey'repeople,didblobsknowtheywereblobs?Whatbitofablobknowsthat?Wheredidconsciousnesscomefrom,then?Didthebiglizardshaveit?What'sitfor?Whataboutimagination?AndevenifIcanthinkupsomekindofanswerstoalthose,he'lsay:look,Stibbons,whatyou'vegotthereisalotofclockworkanswers,andifIaskyouhowyoucangetfromabigbangtoturtlesandspoons

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andDarwin,alyou'lbeabletocomeupwithismoreclockwork.

Howdidalthishappen?Whowounditup?Howcannothingexplode?

TheologyofSpeciesmakessomuchsensewhen'Areyoualright,Stibbons?'HewasawareoftheArchchancelorlookingathimwithuncharacteristicconcern.

`Yes,sir,justabittired.'

Only,yourlipsweremoving.'

Pondersighed.`Whatwasityouwerethinkingabout,sir?'`LotsofDarwinsgetthroughthisvoyage,right?'`Yes.Aninfinitenumber.'

`Wel,inthatcase-'theArchchancelorbegan.

`ButHexdidsayit'samuchsmalerinfinitenumberthatthenumberthatdon't,'saidPonder.Àndthat'sanevensmalernumberthantheverylargeinfinitywhenhenevergoesonthevoyage.Andthenumberofinfinitieswherehe'sneverevenbornis-'

Ìnfinite?'Ridculyasked.

Àtleast,'saidPonder.`However,thereisapositivesidetothis.'`Dotel,Stibbons.'

`Wel,sir,onceOriginispublished,thenumberofuniversesinwhichitispublishedwilalsobecomeinfiniteinaninfinitelysmalspaceoftime.Soeventhoughthebookmayonlybewrittenonce,itwil,byhumanstandards,immediatelyhavebeenwritteninuntoldbilionsofadjacentuniverses.'

Àninfinitenumber,Isuspect?'saidRidculy.

`Yes,sir.Sorryaboutthat.Infinityisabittricky.'

`Youcan'timaginehalfofit,foronething.'

`That'strue.It'snotrealyanumberatal.Youcan'tgettoitstartingfromone.Andthat'stheproblem,sir.Hexisright,theoddestnumberinthemultiverseisn'tinfinity,it'sone.JustoneCharlesDarwinwritingTheOriginofSpecies...it's

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impossible.'

Ridculysatdown.Ì'lbedamngladwhenhefinishesthebook,'hesaid.

`We'lgetalthosenodythingssortedandgethimbackandIpersonalywilhandhimthepen.'

Èr...thatdoesn'thappenimmediately,sir,'saidPonder.`Hedidn'twriteituntilhewasbackhome.'

`Fairenough,'saidRidculy.`Probablyabittricky,writin'onaboat.'

`Hethoughtaboutitalotfirst,sir,'saidPonder.Ìdidmentionthat.'

`Howlong?'saidRidculy.

Àbouttwenty-fiveyears,sir.'

`What?'

`Hewantedtobesure,sir.Heresearchedandwroteletters,lotsofletters.

Hewantedtoknoweverythingabout,wel,everything-silkworms,sheep,jaguars...Hewantedtobesurehewasright.'Ponderthumbedthroughthepapersonhisclipboard.`Thisinterestedme.Itwasfromaletterhewrotein1857,andhesays"whatajumpitisfromawel-markedvariety,producedbyanaturalcause,toaspeciesproducedbytheseparateactoftheHandofGod".

`That'stheauthorofTheOrigin?SoundsmoreliketheauthorofTheOlogy.'

Ìtwasabigthinghewasgoingtodo,sir.Itworriedhim.'

Ì'vereadTheOlogy,'saidRidculy.`Wel,someofit.Makesalotofsense.

`Yes,sir.'

Ìmean,ifwehadn'twatchedtheworldalhappenfromDayOne,we'dhavethought-'

Ìknowwhatyoumean,sir.Ithinkthat'swhyTheOlogywassopopular.'

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`Darwin-ImeanourDarwin-thoughtthatnogodwouldmakesomanykindsofbarnacle.It'ssowasteful.Aperfectbeingwouldn'tdoit,hethought.ButtheotherDarwins,thereligiousones,saidthatwasthewholepoint.Theysaidthatjustasmankindhadtostriveforperfection,somustthewholeanimalkingdom.Plants,too.SurvivaloftheWorthiest,theycaledit.Thingsweren'tmadeperfect,buthadaninbuilt,er,strivingtoachieveperfection,asifpartofthePlanwasinsidethem.Theycouldevolve.Infact,thatwasagoodthing.Itmeanttheyweregettingbetter.'

`Seemslogical,'saidRidculy.`Bygodlogic,atleast.'

Àndthere'sthewholethingabouttheGardenofEdenandtheendoftheworld,'saidPonder.

Ìmust'vemissedthatchapter,'saidRidculy.

`Wel,sir,it'syourbasicmythofagoldenageatthestartoftheworldandterribledestructionattheendofit,butcodifiedinsomeveryinterestinglanguage.Darwinsuggestedthattheearlychroniclershadgotthingsmixedup.Liketrols,youknow?Theythinkthepastisaheadofthembecausetheycanseeit?Theterribledestructionwasinfactthebirthoftheworld-'

'Oh,youmeantheredhotrocks,planetssmackingtogether,thatsortofthing?'

Èxactly.Andtheendoftheworld,wel,asexperienced,wouldbetheassemblyofperfectcreaturesandplantsinaperfectgarden,belongingtothegod.'

`Togetcongratulated,andsoon?Prizeshandedout,marksawarded?'

`Couldbe,sir.'

`Likeaneverlastingpicnic?'

`Hedidn'tputitlikethat,butIsupposeso.'

`Whatabouttheperfectwasps?'saidRidculy.`Youalwaysgetthem,youknow.Andants.'

Ponderhadbeenreadyforthis.

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`Therewasalotofdebateaboutthatsortofthing,'hesaid.

Ànditconcludedhow?'saidtheArchchancelor.

,itwasdecidedthatitwasthekindofsubjectonwhichtherecouldbealotofdebate,andthatearthlyconsiderationswouldnotapply.'

`Hah!AndDarwingotalthispastthepriests?'

Òh,yes.Mostofthem,anyway,'saidPonder.

`Buthewasturningtheirwholeworldupsidedown!'

Ùm,thatwashappeninganyway,sir.Butthisway,thegoddidn'tdropoutofthebottom.Peoplewerepokingaroundandprovingthattheworldrealywasveryold,thatseabedshadbecomemountaintops,thatalkindsofstrangeanimalshadlivedalong,longtimeago.Lotsofpeoplealreadyacceptedtheideaofevolution.Theideaofnaturalselection,asDarwincaledit,oflifejustevolvingitself,washoveringintheair.Itwasabigthreat.ButTheologyofSpeciessaidtherewasaPlan.Ahuge,divinePlan,unfoldingacrossmilionsofyears!Itevenincludedtheplanetitself!

Althatturmoilandvolcanoesanddrowninglands,thatwasaworldevolving,yousee?Aworldthatwouldendupwithtopsoil,andtherightkindofatmosphere,andmineralsthatwereeasilyaccessible,andseasfuloffish-'

Àworldforhumans,inotherwords.'

`Gotitinone,sir,'saidPonder.`Humans.Thetopofthetree.Acreaturethatknewwhatitwas,thatgavethingsnames,thathadaconceptofepiphany.ThatDarwinlaterwroteanotherbook,caledTheAscentofMan.

Oddlyenough,ourDarwinisgoingtowriteasimilarbookcaledTheDescentofMan-'

Àh,Icanseeabadchoiceofwordsrightthere,'saidRidculy.

`Quite,'saidPonder.`TheOlogyDarwinwasconsidereddaringbut...

acceptable.Andtherewassomuchevidencethatthiswasaplanetmadefor

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humans.Thereligionchangedquitealot,butsodidthetechnomancy.

Thegodwasstilincharge.'

'Alveryneat,'saidtheArchchancelor.`So...whataboutthedinosaurs?'

Sorry,sir?'

'MrStibbons,youknowwhatI'mtalkingabout.Wesawthem,remember?

Notthebigones,thelittleoneswhopaintedtheirbodiesandherdedanimals?Andtheoctopusesbuildingcitiesunderthesea?Nottomentionthecrabs!Oh,yes,thecrabs.Theywererealydoingwel,thecrabs.Theywerebuildingraftswithsailsandenslavingothercrabnations.That'spracticalycivilisation!Buttheyalgotwipedout.Wasthatpartofadivineplan?'

Ponderhesitated.

`Theydidworshipacrab-shapedgod,'hesaid,asaholdingstatementuntilactualthoughthappened.

`Wel,theywould,wouldn'tthey?'saidRidculy.`Theywerecrabs.'Ùm.

Perhapstheyjustweren't...satisfactory?'saidPonder.Ìnsomeway?'

`Theywereprettyclever,'saidRidculy.

Pondersquirmed.`Darwindidn'tknowaboutthem,'hesaid.`Theydidn'tbuildanythingthatlasted.IsupposetheDarwinwhowroteTheOlogywouldhavetakentheviewthattheysimplyfailed,orwerewickedinsomeway.Oneofthemajorreligioustextsdoesmentionadivinefloodthatdrownedeverythingintheworldexceptonefamilyandaboatloadofanimals.'

`Why?'

`Becausetheywerealwicked,Ibelieve.'

`Howcananimalsbewicked?Howcanacrabbewicked,forthatmatter?

'Idon'tknow,Archchancelor!'Ponderburstout.`Maybeiftheyeatforbiddenseaweed?Digaburrowonthewrongday?I'mnotatheologian!'

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Theysatindespondentsilence.

Ìt'sabitofmess,isn'tit?,'saidRidculy.

`Yes,sir.'

`We'verealygottoseetoitthatTheOrigingetswritten.'`Wehaveindeed,sir.'

`Butyou'dliketothinkthere'ssomeoneincharge,yes?'saidRidculy,gently.Òfeverything,Imean.'

`Yes!Yes,Iwould,sir!Notabigbeardinthesky,but...something!Somekindofframe,somesensethatgoodandbadhaverealmeanings!IcanseewhyTheOlogywassopopular.Itwrappedeverythingup!Buthowdoesevolutiongetpassedon?Wheredoesordercomefrom?Ifyoustartwithalotofexplodingfirmament,howdoyouendupwithbutterflies?Werebutterfliesbuiltinfromthestart?How?Whatbitofburninghydrogencarriedtheplansforpeople?EventheDarwinwhowroteTheOrigincaledonagodtostartlife.It'sbenicetoknowthatunderneathitalissomekindof...sense.'

`Youdidn'tusedtotalklikethis,MrStibbons.'

Pondersagged.`Sorry,sir.It'salgettingmedown,Ithink.'

`Wel,Icanseewhy,'saidRidculy.`SurelytheremustbesomeDeitiumhere.Somethingscan'tjusthappen.Now,theeyebal-'

Pondergavealittleyelp.

`-iseasy,'saidRidculy.Àreyoualright,Stibbons?'

Èr,fine,fine,sir.I'mfine.Easy,isit?

'Seeingkeepsyoualive,'saidRidculy.Ànykindofseeingisbetterthannothing.Icansee,ha,whattheOriginDarwinisgettingatthere.Youdon'thavetohaveagod.Butthere'sakindofwaspthat'sparasiticalonaspider...unlessI'mthinkingaboutakindofspiderthatisparasiticalonawasp...anyway,whatitdoesis,itwaitsuntil-'

Àh,'saidPonderbrightly,`wasn'tthatthegongforEarlyBreakfast?'

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Ìdidn'thearanything,'saidRidculy.

Ì'mpositive,'saidPonder,edgingtowardsthedoor.Ì'ltelyouwhat,sir,I'ljustgoandcheck.'

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FOURTEEN

ALEPHUMPTYPLEX

THEWIZARDSARENOTONLYgrapplingwiththeapparentabsurditiesof`quantum',theircatch-alphraseforadvancedphysicsandcosmology,butwiththeexplosivephilosophical/mathematicalconceptofinfinity.

Intheirownway,theyhaverediscoveredoneofthegreatinsightsofnineteenth-centurymathematics:thattherecanbemanyinfinities,someofthembiggerthanothers.

Ifthissoundsridiculous,itis.Nonetheless,thereisanentirelynaturalsenseinwhichitturnsouttobetrue.

Therearetwoimportantthingstounderstandaboutinfinity.Althoughtheinfiniteisoftencomparedwithnumberslike1,2,3,infinityisnotitselfanumberinanyconventionalsense.AsPonderStibbonssays,youcan'tgettherefrom1.Theotheristhat,evenwithinmathematics,therearemanydistinctnotionsthatalbearthesamelabelìnfinity'.Ifyoumixuptheirmeanings,alyou'lgetisnonsense.

Andthen-sorry,threeimportantthings-youhavetoappreciatethatinfinityisoftenaprocess,notathing.

But-oh,fourimportantthings-mathematicshasahabitofturningprocessesintothings.

Oh,and-alright,fiveimportantthings-onekindofinfinityisanumber,thoughaslightlyunconventionalone.

Aswelasthemathematicsofinfinity,thewizardsarealsocontendingwithitsphysics.IstheRoundworlduniversefiniteorinfinite?Isittruethatinanyinfiniteuniverse,notonlycananythinghappen,buteverythingmust?Couldtherebeaninfiniteuniverseconsistingentirelyofchairs...immobile,unchanging,wildlyunexciting?Theworldoftheinfiniteisparadoxical,orsoitseemsatfirst,butweshouldn'tlettheapparentparadoxesputusoff.Ifwekeepaclearhead,wecansteerourwaythroughtheparadoxes,andturntheinfinite

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intoareliablethinkingaid.

Philosophersgeneralydistinguishtwodifferent`flavours'ofinfinity,whichtheycalàctual'and`potential'.Actualinfinityisathingthatisinfinitelybig,andthat'ssuchamouthfultoswalowthatuntilrecentlyitwasratherdisreputable.Themorerespectableflavourispotentialinfinity,whichariseswheneversomeprocessgivesusthedistinctimpressionthatitcouldbecontinuedforaslongaswelike.Themostbasicprocessofthiskindiscounting:1,2,3,4,5...Doweeverreach`thebiggestpossiblenumber'andthenstop?Childrenoftenaskthatquestion,andatfirsttheythinkthatthebiggestnumberwhosenametheyknowmustbethebiggestnumberthereis.Soforawhiletheythinkthatthebiggestnumberissix,thentheythinkit'sahundred,thentheythinkit'sathousand.Shortlyafter,theyrealisethatifyoucancounttoathousand,thenathousandandoneisonlyasinglestepfurther.

Intheir1949bookMathematicsandtheImagination,EdwardKasnerandJamesNewmanintroducedtheworldtothegoogol-thedigit1folowedbyahundredzeros.Bearinmindthatabilionhasamereninezeros:1000000000.Agoogolis

100000000000000000000000000000000000000000000000000

00000000000000000000000000000000000000000000000000

andit'ssobigwehadtosplititintwotofitthepage.ThenamewasinventedbyKasner'snine-year-oldnephew,andistheinspirationfortheinternetsearchengineGoogleTM

Eventhoughagoogolisverybig,itisdefinitelynotinfinite.Itiseasytowritedownabiggernumber:

100000000000000000000000000000000000000000000000000

00000000000000000000000000000000000000000000000001

Justadd1.Amorespectacularwaytofindabiggernumberthanagoogolistoformagoogolplex(namealsocourtesyofthenephew),whichis1

folowedbyagoogolofzeros.Donotattempttowritethisnumberdown:theuniverseistoosmalunlessyouusesubatomic-sizeddigits,anditslifetimeistoo

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short,letaloneyours.

Eventhoughagoogolplexisextraordinarilybig,itisapreciselydefinednumber.Thereisnothingvagueaboutit.Anditisdefinitelynotinfinite(justadd1).Itis,however,bigenoughformostpurposes,includingmostnumbersthatturnupinastronomy.KasnerandNewmanobservethatàssoonaspeopletalkaboutlargenumbers,theyrunamuck.Theyseemtobeundertheimpressionthatsincezeroequalsnothing,theycanaddasmanyzerostoanumberastheypleasewithpracticalynoseriousconsequences,'asentencethatMustrumRidculyhimselfmighthaveuttered.Asanexample,theyreportthatinthelate1940sadistinguishedscientificpublicationannouncedthatthenumberofsnowcrystalsneededtostartaniceageisabiliontothebilionthpower.`This,'theytelus,ìsverystartlingandalsoverysily.'Abiliontothebilionthpoweris1folowedbyninebilionzeros.Asensiblefigureisaround1folowedby30zeros,whichisfantasticalysmaler,thoughstilbiggerthanBilGates'sbankbalance.

Whateverinfinitymaybe,it'snotaconventional`counting'number.Ifthebiggestnumberpossiblewere,say,umpty-umpgazilion,thenbythesametokenumpty-umpgazilionandonewouldbebiggerstil.Andevenifitweremorecomplicated,sothat(say)thebiggestnumberpossiblewereumpty-umpgazilion,twomilion,ninehundredandsixty-fourthousand,sevenhundredandfifty-eight...thenwhataboutumpty-umpgazilion,twomilion,ninehundredandsixty-fourthousand,sevenhundredandfifty-nine?

Givenanynumber,youcanalwaysaddone,andthenyougetanumberthatis(slightly,butdistinguishably)bigger.

Thecountingprocessonlystopsifyourunoutofbreath;itdoesnotstopbecauseyou'verunoutofnumbers.Thoughanearimmortalmightperhapsrunoutofuniverseinwhichtowritethenumbersdown,ortimeinwhichtoutterthem.

Inshort:thereexistinfinitelymanynumbers.

Thewonderfulthingaboutthatstatementisthatitdoesnotimplythatthereissomenumbercaledìnfinity',whichisbiggerthananyoftheothers.

Quitethereverse:thewholepointisthatthereisn'tanumberthatisbiggerthananyoftheothers.Soalthoughtheprocessofcountingcaninprinciplegoonforever,thenumberyouhavereachedatanyparticularstageisfinite.`Finite'meansthatyoucancountuptothatnumberandthenstop.

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Asthephilosopherswouldsay:countingisaninstanceofpotentialinfinity.

Itisaprocessthatcangoonforever(oratleast,soitseemstoournaivepattern-recognisingbrains)butnevergetstòforever'.

Thedevelopmentofnewmathematicalideastendstofolowapattern.Ifmathematicianswerebuildingahouse,theywouldstartwiththedownstairswals,hoveringunsupportedafootorsoabovethedampproofcourse...orwherethedampproofcourseoughttobe.Therewouldbenodoorsorwindows,justholesoftherightshape.Bythetimethesecondfloorwasadded,thequalityofthebrickworkwouldhaveimproveddramaticaly,theinteriorwalswouldbeplastered,thedoorsandwindowswouldalbeinplace,andthefloor

wouldbestrongenoughtowalkon.Thethirdfloorwouldbevast,elaborate,fulycarpeted,withpicturesonthewals,hugequantitiesoffurnitureofimpressivebutinconsistentdesign,sixtypesofwalpaperineveryroom...Theattic,incontrast,wouldbesparsebutelegant-

minimalistdesign,nothingoutofplace,everythingthereforareason.Then,andonlythen,wouldtheygobacktogroundlevel,digthefoundations,filthemwithconcrete,stickinadampproofcourse,andextendthewalsdownwardsuntiltheymetthefoundations.

Attheendofitalyou'dhaveahousethatwouldstandup.Alongtheway,itwouldhavespentalotofitsexistencelookingwildlyimprobable.Butthebuilders,intheirexcitementtopushthewalsskywardsandfiltheroomswithinteriordecor,wouldhavebeentoobusytonoticeuntilthebuildinginspectorsrubbedtheirnosesinthestructuralfaults.

Whennewmathematicalideasfirstarise,nooneunderstandsthemterriblywel,whichisonlynaturalbecausethey'renew.Andnooneisgoingtomakeagreatdealofefforttosortoutalthelogicalrefinementsandmakesenseofthoseideasunlessthey'reconvincedit'salgoingtobeworthwhile.Sothemainthrustofresearchgoesintodevelopingthoseideasandseeingiftheyleadanywhereinteresting.Ìnteresting',toamathematician,mostlymeans`canIseewaystopushthisstufffurther?',buttheacidtestis`whatproblemsdoesitsolve?'Onlyaftergettingasatisfactoryanswertothesequestionsdoafewhardyandpedanticsoulsdescendintothebasementandsortoutdecentfoundations.

Somathematicianswereusinginfinitylongbeforetheyhadacluewhatitwasor

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howtohandleitsafely.In500BcArchimedes,thegreatestoftheGreekmathematiciansandaseriouscontenderforaplaceintheal-timetopthree,workedoutthevolumeofasphereby(conceptualy)slicingitintoinfinitelymanyinfinitelythindiscs,likeanultra-thinslicedloaf,andhangingaltheslicesfromabalance,tocomparetheirtotalvolumewiththatofasuitableshape

whosevolumehealreadyknew.Oncehe'dworkedouttheanswerbythisastonishingmethod,hestartedagainandfoundalogicalyacceptablewaytoprovehewasright.Butwithoutalthatfaffingaroundwithinfinity,hewouldn'thaveknownwheretostartandhislogicalproofwouldn'thavegotofftheground.

BythetimeofLeonhardEuler,anauthorsoprolificthatwemightconsiderhimtobetheTerryPratchettofeighteenth-centurymathematics,manyoftheleadingmathematiciansweredabblinginìnfiniteseries'-theschoolchild'snightmareofasumthatneverends.Here'sone:1+1/2+1/4+1/8+1/16+1/32+.-

wherethè...'means`keepgoing'.Mathematicianshaveconcludedthatifthisinfinitesumaddsuptoanythingsensible,thenwhatitaddsuptomustbeexactlytwo.[1]Ifyoustopatanyfinitestage,though,whatyoureachisslightlylessthantwo.Buttheamountbywhichitislessthantwokeepsshrinking.Thesumsortofsneaksuponthecorrectanswer,withoutactualygettingthere;buttheamountbywhichitfailstogettherecanbemadeassmalasyouplease,byaddingupenoughterms.

Remindyouofanything?ItlookssuspiciouslysimilartooneofZeno/Xeno'sparadoxes.Thisishowthearrowsneaksuponitsvictim,howAchilessneaksuponthetortoise.Itishowyoucandoinfinitelymanythingsinafinitetime.Dothefirstthing;dothesecondthingoneminutelater;dothethirdthinghalfaminuteafterthat;thenthefourththingaquarterofaminuteafterthat...andsoon.Aftertwominutes,you'vedoneinfinitelymanythings.

Therealisationthatinfinitesumscanhaveasensiblemeaningisonlythestart.Itdoesn'tdispelaloftheparadoxes.Mostly,itjust[1]Toseewhy,doubleit:theresultnowis2+1+V2+'/+y8+'A+...,whichis2morethantheoriginalsum.Whatnumberincreasesby2whenyoudoubleit?There'sonlyonesuchnumber,andit's2.

sharpensthem.Mathematiciansworkedoutthatsomeinfinitiesareharmless,

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othersarenot.

Theonlyproblemleftafterthatbriliantinsightwas:howdoyoutel?Theansweristhatifyourconceptofinfinitydoesnotleadtologicalcontradictions,thenit'ssafetouse,butifitdoes,thenitisn't.Yourtaskistogiveasensiblemeaningtowhateverìnfinity'intriguesyou.Youcan'tjustassumethatitautomaticalymakessense.

Throughouttheeighteenthandearlynineteenthcenturies,mathematicsdevelopedmanynotionsofìnfinity',alofthempotential.Inprojectivegeometry,thèpointatinfinity'waswheretwoparalellinesmet:thetrickwastodrawtheminperspective,likerailwaylinesheadingofftowardsthehorizon,inwhichcasetheyappeartomeetonthehorizon.Butifthetrainsarerunningonaplane,thehorizonisinfinitelyfarawayanditisn'tactualypartoftheplaneatal-it'sanopticalilusion.Sothepointàt'infinityisdeterminedbytheprocessoftravelingalongthetraintracksindefinitely.

Thetrainneveractualygetsthere.Inalgebraicgeometryacircleendedupbeingdefinedasàconicsectionthatpassesthroughthetwoimaginarycircularpointsatinfinity',whichsureputsapairofcompassesintheirplace.

Therewasanoveralconsensusamongmathematicians,anditboileddowntothis.Wheneveryouusethetermìnfinity'youarerealythinkingaboutaprocess.Ifthatprocessgeneratessomeweldeterminedresult,byhoweverconvolutedaninterpretationyouwish,thenthatresultgivesmeaningtoyouruseofthewordìnfinity',inthatparticularcontext.

Infinityisacontext-dependentprocess.Itispotential.

Itcouldn'tstaythatway.

avidHilbertwasoneofthetoptwomathematiciansintheworldattheendofthenineteenthcentury,andhewasoneofthegreatenthusiastsforanewapproachtotheinfinite,inwhich-contrarytowhatwe'vejusttoldyou-

infinityistreatedasathing,notasaprocess.ThenewapproachwasthebrainchildofGeorgCantor,aGermanmathematicianwhoseworkledhimintoterritorythatwasfraughtwithlogicalsnares.Thewholeareawasaconfusedmessforaboutacentury(nothingnewthere,then).Eventualyhedecidedtosortitoutforgoodandalbyburrowingdownwardsratherthanbuildingever

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upwards,andputtinginthosepreviouslynon-existentfoundations.Hewasn'ttheonlypersondoingthis,buthewasamongthemoreradicalones.Hesucceededinsortingouttheareathatdrovehimtotheselengths,butonlyattheexpenseofcausingconsiderabletroubleelsewhere.

ManymathematiciansdetestedCantor'sideas,butHilbertlovedthem,anddefendedthemvigorously.`Noone,'hedeclaimed,`shalexpelusfromtheparadisethatCantorhascreated.'Itis,tobesure,asmuchparadoxasparadise.HilbertexplainedsomeoftheparadoxicalpropertiesofinfinityalaCantorintermsofafictitioushotel,nowknownasHilbert'sHotel.

Hilbert'sHotelhasinfinitelymanyrooms.Theyarenumbered1,2,3,4andsoonindefinitely.Itisaninstanceofactualinfinity-everyroomexistsnow,they'renotstilbuildingroomumpty-umpgazilionandone.Andwhenyouarrivethere,onSundaymorning,everyroomisoccupied.

Inafinitehotel,evenwithumpty-umpgazilionandonerooms,you'reintrouble.Noamountofmovingpeoplearoundcancreateanextraroom.(Tokeepitsimple,assumenosharing:eachroomhasexactlyoneoccupant,andhealthandsafetyregulationsforbidmorethanthat.)InHilbert'sHotel,however,thereisalwaysroomforanextraguest.Notinroominfinity,though,forthereisnosuchroom.Inroomone.

Butwhataboutthepoorunfortunateinroomone?Hegetsmovedtoroomtwo.Thepersoninroomtwoismovedtoroomthree.Andsoon.Thepersoninroomumpty-umpgazilionismovedtoroomumpty-umpgazilionandone.Thepersoninroomumpty-umpgazilionandoneismovedtoroomumpty-umpgazilionandtwo.Thepersoninroomnismovedtoroomn+1,foreverynumbern.

Inafinitehotelwithumpty-umpgazilionandonerooms,thisprocedurehitsasnag.Thereisnoroomumpty-umpgazilionandtwointowhichtomoveitsinhabitant.InHilbert'sHotel,thereisnoendtotherooms,andeveryonecanmoveoneplaceup.Oncethismoveiscompleted,'thehotelisonceagainful.

That'snotal.OnMonday,acoachloadof50peoplearrivesatthecompletelyfulHilbertHotel.Noworries:themanagermoveseverybodyup50places-room1to51,room2to52,andsoon-whichleavesrooms1-50vacantforthepeopleoffthecoach.

OnTuesday,anInfinityTourscoacharrivescontaininginfinitelymanypeople,

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helpfulynumberedA1,A2,A3,....Surelytherewon'tberoomnow?Butthereis.Theexistingguestsaremovedintotheeven-numberedrooms:room1movestoroom2,room2toroom4,room3toroom6,andsoon.Thentheodd-numberedroomsarefree,andpersonA1goesintoroom1,A2intoroom3,A3intoroom5...Nothingtoit.

ByWednesday,themanagerisrealytearinghishairout,becauseinfinitelymanyInfinityTourscoachesturnup.ThecoachesarelabeledA,B,C,...fromaninfinitelylongalphabet,andthepeopleinthemareA1,A2,A3,...,B1,B2,B3,...C1,C2,C3,.

..andsoon.Butthemanagerhasabrainwave.Inaninfinitelylargecorneroftheinfinitelylargehotelparkinglot,hearrangesalthenewguestsintoaninfinitelylargesquare:

AlA2A3A4A5...

B1B2B3B4B5...

C1C2C3C4C5...

D1D2D3D4D5...

E1E2E3E4E5...

Thenherearrangesthemintoasingleinfinitelylongline,intheorderA1-A2B1-A3B2C1-A4B3C2D1-A5B4C3D2El...

(Toseethepattern,lookalongsuccessivediagonalsrunningfromtoprighttolowerleft.We'veinsertedhyphenstoseparatethese.)Whatmostpeoplewouldnowdoismovealtheexistingguestsintotheeven-numberedrooms,andthenfiluptheoddroomswithnewguests,intheorderoftheinfinitelylongline.Thatworks,butthereisamoreelegantmethod,andthemanager,beingamathematician,spotsitimmediately.

HeloadseverybodybackintoasingleInfinityTourscoach,filingtheseatsintheorderoftheinfinitelylongline.Thisreducestheproblemtoonethathasalreadybeensolved.[1]

Hilbert'sHoteltelsustobecarefulwhenmakingassumptionsaboutinfinity.It

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maynotbehavelikeatraditionalfinitenumber.Ifyouaddonetoinfinity,itdoesn'tgetbigger.Ifyoumultiplyinfinitybyinfinity,itstildoesn'tgetbigger.Infinityislikethat.Infact,it'seasytoconcludethatanysuminvolvinginfinityworksoutasinfinity,becauseyoucan'tgetanythingbiggerthaninfinity.

That'swhateverybodythought,whichisfairenoughiftheonlyinfinitiesyou'veeverencounteredarepotentialones,approachedasasequenceoffinitesteps,butinprinciplegoingonforaslongasyouwish.Butinthe1880sCantorwasthinkingaboutactual[1]Ifyou'veneverencounteredthemathematicaljoke,hereitis.Problem1:akettleishangingonapeg.Describethesequenceofeventsneededtomakeapotoftea.Answer:takethekettleoffthepeg,putitinthesink,turnonthetap,waittilthekettlefilswithwater,turnthetapoff...andsoon.

Problem2:akettleissittinginthesink.Describethesequenceofeventsneededtomakeapotoftea.Answer:not`turnonthetap,waittilthekettlefilswithwater,turnthetapoff...andsoon'.Instead:takethekettleoutofthesinkandhangitonthepeg,thenproceedasbefore.Thisreducestheproblemtoonethathasalreadybeensolved.(Ofcoursethefirststepputsitbackinthesink-that'swhyit'sajoke.)infinities,andheopenedupaveritablePandora'sboxofever-largerinfinities.Hecaledthemtrans-finitenumbers,andhestumbledacrossthemwhenhewasworkinginahalowed,traditionalareaofanalysis.Itwasrealyhard,technicalstuff,anditledhimintopreviouslyunchartedbyways.Musingdeeplyonthenatureofthesethings,Cantorbecamedivertedfromhisworkinhisentirelyrespectableareaofanalysis,andstartedthinkingaboutsomethingmuchmoredifficult.

Counting.

Theusualwaythatweintroducenumbersisbyteachingchildrentocount.

Theylearnthatnumbersarèthingsyouuseforcounting'.Forinstance,`seven'iswhereyougettoifyoustartcountingwithòne'forSundayandstoponSaturday.Sothenumberofdaysintheweekisseven.Butwhatmannerofbeastisseven?Aword?No,becauseyoucouldusethesymbol7instead.Asymbol?Butthen,there'stheword...anyway,inJapanese,thesymbolfor7isdifferent.Sowhatisseven?It'seasytosaywhatsevendays,orsevensheep,orsevencoloursofthespectrumare...butwhataboutthenumberitself?Youneverencounteranaked`seven',italwaysseemstobeattachedtosomecolectionofthings.

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Cantordecidedtomakeavirtueofnecessity,anddeclaredthatanumberwassomethingassociatedwithaset,orcolection,ofthings.Youcanputtogetherasetfromanycolectionofthingswhatsoever.Intuitively,thenumberyougetbycountingtelsyouhowmanythingsbelongtothatset.

Thesetofdaysoftheweekdeterminesthenumber`seven'.ThewonderfulfeatureofCantor'sapproachisthis:youcandecidewhetheranyothersethassevenmemberswithoutcountinganything.Todothis,youjusthavetotrytomatchthemembersofthesets,sothateachmemberofonesetismatchedtopreciselyoneoftheother.If,forinstance,thesecondsetisthesetofcoloursofthespectrum,thenyoumightmatchthesetslikethis:SundayRed

MondayOrange

TuesdayYelow

WednesdayGreen

ThursdayBlue

FridayViolet[1]

SaturdayOctarine

Theorderinwhichtheitemsarelisteddoesnotmatter.Butyou'renotalowedtomatchTuesdaywithbothVioletandGreen,orGreenwithbothTuesdayandSunday,inthesamematching.Ortomissanymembersofthesetsout.

Incontrast,ifyoutrytomatchthedaysoftheweekwiththeelephantsthatsupporttheDisc,yourunintotrouble:SundayBerilia

MondayTubul

TuesdayGreatT'Phon

WednesdayJerakeen

Thursday?

Moreprecisely,yourunoutofelephants.Eventhelegendaryfifthelephantfails

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totakeyoupastThursday.

Whythedifference?Wel,therearesevendaysintheweek,andsevencoloursofthespectrum,soyoucanmatchthosesets.Butthereareonlyfour(perhapsoncefive)elephants,andyoucan'tmatchfourorfivewithseven.

Thedeepphilosophicalpointhereisthatyoudon'tneedtoknowaboutthenumbersfour,fiveorseven,todiscoverthatthere'snowaytomatchthesetsup.Talkingaboutthenumbersamountstobeingwiseaftertheevent.

Matchingislogicalyprimary

[1]Yes,traditionalyÌndigo'goeshere,butthat'ssily-Indigoisjustanothershadeofblue.Youcouldequalywelinsert`Turquoise'betweenGreenandBlue.Indigowasjustincludedbecausesevenismoremysticalthansix.

Rewritinghistory,wefindthatwehaveleftaplaceforOctarine,theDiscworld'seighthcolour.Wel,seventh,actualy.Septarine,anyone?

tocounting.[1]Butnow,alsetsthatmatcheachothercanbeassignedacommonsymbol,or`cardinal',whicheffectivelyisthecorrespondingnumber.Thecardinalofthesetofdaysoftheweekisthesymbol7,forinstance,andthesamesymbolappliestoanysetthatmatchesthedaysoftheweek.Sowecanbaseourconceptofnumberonthesimpleroneofmatching.

Sofar,then,nothingnew.But`matching'makessenseforinfinitesets,notjustfiniteones.Youcanmatchtheevennumberswithalnumbers:21

42

63

84

105

andsoon.Matchingslikethisexplainthegoings-oninHilbert'sHotel.

That'swhereHilbertgottheidea(roofbeforefoundations,remember).

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Whatisthecardinalofthesetofalwholenumbers(andhenceofanysetthatcanbematchedtoit)?Thetraditionalnameis'infinity'.Cantor,beingcautious,preferredsomethingwithfewermentalassociations,andin1883

henamedit'aleph',thefirstletteroftheHebrewalphabet.Andheputasmalzerounderneathit,forreasonsthatwilshortlytranspire:aleph-zero.

Heknewwhathewasstarting:Ìamwelawarethatbyadopting[1]Thisiswhy,eventodaywhenthelustreof`thenewmathematics'hasalbutworntodust,smalchildreninmathematicsclassesspendhoursdrawingsquigglylinesbetweencirclescontainingpicturesofcatstocirclescontainingpicturesofflowers,busily`matching'thetwosets.

Neitherthechildrennortheirteachershavethefoggiestideawhytheyaredoingthis.Infacttheyredoingitbecause,decadesago,abunchofdementededucatorscouldn'tunderstandthatjustbecausesomethingislogicalypriortoanother,itmaynotbesensibletoteachtheminthatorder.

Realmathematicians,whoknewthatyoualwaysputtheroofonthehousebeforeyoudugthefoundationtrench,lookedoninbemusedhorror.

suchaprocedureIamputtingmyselfinoppositiontowidespreadviewsregardinginfinityinmathematicsandtocurrentopinionsonthenatureofnumber.'Hegotwhatheexpected:alotofhostility,especialyfromLeopoldKronecker.`Godcreatedtheintegers:alelseistheworkofMan,'

Kroneckerdeclared.

Nowadays,mostofusthinkthatMancreatedtheintegerstoo.

Whyintroduceanewsymbol(andHebrewatthat?).IftherehadbeenonlyoneinfinityinCantor'ssense,hemightaswelhavenameditìnfinity'likeeveryoneelse,andusedthetraditionalsymbolofafigure8lyingonitsside.Buthequicklysawthatfromhispointofview,theremightwelbeotherinfinities,andhewasreservingtherighttonamethosealeph-one,aleph-two,aleph-three,andsoon.

Howcantherebeotherinfinities?Thiswasthebigunexpectedconsequenceofthatsimple,childishideaofmatching.Todescribehowitcomesabout,weneedsomewaytotalkaboutrealybignumbers.Finiteonesandinfiniteones.Tolul

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youintothebeliefthateverythingiswarmandfriendly,we'lintroduceasimpleconvention.

If'umpty'isanynumber,ofwhateversize,then'umptyplex'wilmean10umpty,whichis1folowedbyumptyzeros.So2plexis100,ahundred;6plexis1000000,amilion;9plexisabilion.Whenumpty=100wegetagoogol,sogoogol=100plex.Agoogolplexisthereforealsodescribableas100plexplex.

InCantorianmode,weidlystarttomuseaboutinfinityplex.Butlet'sbeprecise:whataboutaleph-zeroplex?Whatis10^aleph-zero?

Remarkably,ithasanentirelysensiblemeaning.Itisthecardinalofthesetofalrealnumbers-alnumbersthatcanberepresentedasaninfinitelylongdecimal.RecaltheEphebianphilosopherPthagonal,whoisrecordedassaying,`Thediameterdividesintothecircumference...Itoughttobethreetimes.Butdoesit?No.Threepointonefourandlotsofotherfigures.

There'snoendtothebuggers.'This,ofcourse,isareferencetothemostfamousrealnumber,onethatrealydoesneedinfinitelymanydecimalplacestocaptureitexactly:n('pi').Toonedecimalplace,nis3.1.Totwoplaces,itis3.14.Tothreeplaces,itis3.141.Andsoon,adinfinitum.

Thereareplentyofrealnumbersotherthann.Howbigisthephasespaceofalrealnumbers?

Thinkaboutthebitafterthedecimalpoint.Ifweworktoonedecimalplace,thereare10possibilities:anyofthedigits0,1,2,...,9.Ifweworktotwodecimalplaces,thereare100possibilities:00upto99.Ifweworktothreedecimalplaces,thereare1000possibilities:000upto999.

Thepatternisclear.Ifweworktoumptydecimalplaces,thereare10^umptypossibilities.Thatis,umptyplex.

Ifthedecimalplacesgoon`forever',wefirstmustask`whatkindofforever?'Andtheansweris`Cantor'saleph-zero',becausethereisafirstdecimalplace,asecond,athird...theplacesmatchthewholenumbers.

Soifweset'umpty'equalto'aleph-zero',wefindthatthecardinalofthesetofalrealnumbers(ignoringanythingbeforethedecimalpoint)isaleph-zeroplex.Thesameistrue,forslightlymorecomplicatedreasons,ifweincludethebitbefore

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thedecimalpoint.'[1]

Alverywel,butpresumablyaleph-zeroplexisgoingtoturnouttobealeph-zeroinheavydisguise,sincealinfinitiessurelymustbeequal?No.

They'renot.Cantorprovedthatyoucan'tmatchtherealnumberswiththewholenumbers.Soaleph-zeroplexisabiggerinfinitythanaleph-zero.

Hewentfurther.Muchfurther.Heproved[2]thatifumptyisanyinfinitecardinal,theumptyplexisabiggerone.Soaleph-zeroplexplexis[1]Briefly:sincethebitbeforethedecimalpointisawholenumber,takingthatintoaccountmultipliestheanswerbyaleph-zero.Nowaleph-zeroxaleph-zeroplexislessthanorequaltoaleph-zeroplexxaleph-zeroplex,whichis(2xaleph-zeroplex,whichisaleph-zeroplex.OK?

[2]Theproofisn'thard,butit'ssophisticated.Ifyouwanttoseeit,consultatextbookonthefoundationsofmathematics.

biggerstil,andaleph-zeroplexplexplexisbiggerthanthat,and...

ThereisnoendtothelistofCantorianinfinities.Thereisno'hyperinfinity'

thatisbiggerthanalotherinfinities.

Theideaofinfinityas`thebiggestpossiblenumber'istakingsomehardknockshere.Andthisisthesensiblewaytosetupinfinitearithmetic.

Ifyoustartwithanyinfinitecardinalalephumpty,thenalephumptyplexisbigger.Itisnaturaltosupposethatwhatyougetmustbealeph-(umpty+1),astatementdubbedtheGeneralisedContinuumHypothesis.In1963PaulCohen(noknownrelationeithertoJackortheBarbarian)provedthat...

wel,itdepends.Insomeversionsofsettheoryit'strue,inothersit'sfalse.

Thefoundationsofmathematicsarelikethat,whichiswhyit'sbesttoconstructthehousefirstandputthefoundationsinlater.Thatway,ifyoudon'tlikethem,youcantakethemoutagainandputsomethingelseininstead.Withoutdisturbingthehouse.

This,then,isCantor'sParadise:anentirelynewnumbersystemofalephs,of

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infinitiesbeyondmeasure,never-ending-inaverystrongsenseof`never'.Itarisesentirelynaturalyfromonesimpleprinciple:thatthetechniqueof`matching'isalyouneedtosetupthelogicalfoundationsofarithmetic.MostworkingmathematiciansnowagreewithHilbert,andCantor'sinitialyastonishingideashavebeenwovenintotheveryfabricofmathematics.

Thewizardsdon'tjusthavethemathematicsofinfinitytocontendwith.

Theyarealsogettingtangledupinthephysics.Here,entirelynewquestionsabouttheinfinitearise.Istheuniversefiniteorinfinite?Whatkindoffiniteorinfinite?Andwhataboutalthoseparaleluniversesthatthecosmologistsandquantumtheoristsarealwaystalkingabout?Evenifeachuniverseisfinite,couldtherebeinfinitelymanyparalelones?

Accordingtocurrentcosmology,whatwenormalythinkofastheuniverseisfinite.ItstartedasasinglepointintheBigBang,andthenexpandedatafiniterateforabout13bilionyears,soithastobefinite.Ofcourse,itcouldbeinfinitelyfinelydivisible,withnolowerlimittothesizesofthings,justlikethemathematician'slineorplane-butquantum-mechanicalyspeakingthereisadefinitegraininessdownatthePlancklength,sotheuniversehasaverylargebutfinitenumberofpossiblequantumstates.

Thèmanyworlds'versionofquantumtheorywasinventedbythephysicistHughEverettasawaytolinkthequantumviewoftheworldtooureveryday`sensible'view.Itcontendsthatwheneverachoicecanbemade-forexample,whetheranelectronspinisupordown,oracatisaliveordead-

theuniversedoesnotsimplymakeachoiceandabandonalthealternatives.That'swhatitlooksliketous,butrealytheuniversemakesalpossiblechoices.Innumerableàlternative'or`paralel'worldsbranchofffromtheonethatweperceive.Inthoseworlds,thingshappenthatdidnothappenhere.Inoneofthem,AdolfHitlerwontheSecondWorldWar.Inanother,youateoneextraoliveatdinnerlastnight.

Narrativelyspeaking,themanyworldsdescriptionofthequantumrealmisadelight.Noauthorinsearchofimpressivescientificgobbledegookthatcanjustifyhurlingcharactersintoalternativestorylines-wepleadguilty-

canpossiblyresist.

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Thetroubleisthat,asscience,themany-worldsinterpretationisratheroverrated.Certainly,theusualwaythatitisdescribedismisleading.Infact,rathertoomuchofthephysicsofmultipleuniversesisusualyexplainedinamisleadingway.Thisisapity,becauseittrivialisesaprofoundandbeautifulsetofideas.Thesuggestionthatthereexistsarealuniverse,somehowadjacenttoours,inwhichHitlerdefeatedtheAlies,isabigturn-offforalotofpeople.Itsoundstooabsurdeventobeworthconsidering.Ìfthat'swhatmodernphysicsisabout,I'dprefermytaxdolarstogotowardssomethinguseful,likereflexology.'

Thescienceof`the'multiverse-therearenumerousalternatives,whichisonlyappropriate-isfascinating.Someofitisevenuseful.

Andsome-notnecessarilytheusefulbit-mightevenbetrue.Thoughnot,wewiltrytoconvinceyou,thebitaboutHitler.

ItalstartedwiththediscoverythatquantumbehaviourcanberepresentedmathematicalyasaBigSum.Whatactualyhappensisthesumofalofthethingsthatmighthavehappened.RichardFeynmanexplainedthiswithhisusualextremeclarityinhisbookQED(QuantumElectroDynamics,notEuclid).Imagineaphoton,aparticleoflight,bouncingoffamirror.Youcanworkoutthepaththatthephotonfolowsbyàddingup'alpossiblepathsthatitmighthavetaken.Whatyourealyaddisthelevelsofbrightness,thelightintensities,notthepaths.Apathisaconcentratedstripofbrightness,andherethatstriphitsthemirrorandbouncesbackatthesameangle.

This`sum-over-histories'techniqueisadirectmathematicalconsequenceoftherulesofquantummechanics,andthere'snothingobjectionableoreventerriblysurprisingaboutit.Itworksbecausealofthèwrong'pathsinterferewitheachother,andbetweenthemtheycontributevirtualynothingtotheoveralsum.Althatsurvives,asthetotalscomein,isthèright'path.

Youcantakethisunobjectionablemathematicalfactanddressitupwithaphysicalinterpretation.Namely:lightrealytakesalpossiblepaths,butwhatweobserveisthesum,sowejustseetheonepathinwhichthelight`ray'hitsthemirrorandbouncesoffagainatthesameangle.

Thatinterpretationisalsonotterriblyobjectionable,philosophicalyspeaking,butitvergesintoterritorythatis.Physicistshaveahabitoftakingmathematicaldescriptionsliteraly-notjusttheconclusions,butthestepsemployedtoget

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them.Theycalthis`thinkingphysicaly',butactualyit'sthereverse:itamountstoprojectingmathematicalfeaturesontotherealworld-`reifying'abstractions,endowingthemwithreality.

We'renotsayingitdoesn'twork-oftenitdoes.Butreificationtendstomakephysicistsbadphilosophers,becausetheyforgetthey'redoingit.

Oneproblemwith`thinkingphysicaly'isthattherearesometimesseveralmathematicalyequivalentwaystodescribesomething-differentwaystosayexactlythesamethinginmathematicallanguage.Ifoneofthemistrue,theyalare.But,theirnaturalphysicalinterpretationscanbeinconsistent.

Agoodexamplearisesinclassical(non-quantum)mechanics.Amovingparticlecanbedescribedusing(oneof)Newton'slawsofmotion:theparticle'saccelerationisproportionaltotheforcesthatactonit.

Alternatively,themotioncanbedescribedintermsofàvariationalprinciple':associatedwitheachpossibleparticlepaththereisaquantitycaledtheàction'.Theactualpaththattheparticlefolowsistheonethatmakestheactionassmalaspossible.

ThelogicalequivalenceofNewton'slawsandtheprincipleofleastactionisamathematicaltheorem.Youcannotacceptonewithoutacceptingtheother,onamathematicallevel.Don'tworrywhatàction'is.Itdoesn'tmatterhere.Whatmattersisthedifferencebetweenthenaturalinterpretationsofthesetwologicalyidenticaldescriptions.

Newton'slawsofmotionarelocalrules.Whattheparticledoesnext,hereandnow,isentirelydeterminedbytheforcesthatactonit,hereandnow.

Noforesightorinteligenceisneeded;justkeeponobeyingthelocalrules.

Theprincipleofleastactionhasadifferentstyle:itisglobal.IttelsusthatinordertomovefromAtoB,theparticlemustsomehowcontemplatethetotalityofalpossiblepathsbetweenthosepoints.Itmustworkouttheactionassociatedwitheachpath,andfindwhicheveroneofthemhasthesmalestaction.This`computation'isnon-local,becauseitinvolvestheentirepath(s),andinsomesenseithastobecarriedoutbeforetheparticleknowswheretogo.Sointhisnaturalinterpretationofthemathematics,theparticleappearstobeendowedwithmiraculousforesightandtheabilitytochoose,arudimentarykindofintel

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igence.

Sowhichisit?Amindlesslumpofmatterwhichobeysthelocalrulesasitgoesalong?Oraquasi-inteligententitywithvastcomputationalpowers,whichhastheforesighttochoose,amongalthepossiblepathsthatitcouldhavetaken,preciselytheuniqueonethatminimisestheaction?

Weknowwhichinterpretationwe'dchoose.

Interestingly,theprincipleofleastactionisamechanicalanalogueofFeynman'ssum-over-historiesmethodinoptics.Thetworealyareextremelyclose.Yes,youcanformulatethemathematicsofquantummechanicsinawaythatseemstoimplythatlightfolowsalpossiblepathsandaddsthemup.Butyouarenotobligedtobuythatdescriptionastherealphysicsoftherealworld,evenifthemathematicsworks.

Themany-worldsenthusiastsdobuythatdescription:infact,theytakeitmuchfurther.Notthehistoryofasinglephotonbouncingoffamirror,butthehistoryoftheentireuniverse.That,too,isasumofalpossibilities-

usingtheuniverse'squantumwavefunctioninplaceofthelightintensityduetothephoton-sobythesametoken,wecaninterpretthemathematicsinasimilarlydramaticway.Namely:theuniverserealydoesdoalpossiblethings.Whatweobserveiswhathappenswhenyouaddalthosepossibilitiesup.

Ofcoursethere'salsoalessdramaticinterpretation:theuniversetrundlesalongobeyingthelocallawsofquantummechanics,anddoesexactlyonething...whichjusthappens,forpurelymathematicalreasons,toequalthesumofalthethingsthatitmighthavedone.

Whichinterpretationdoyoubuy?

Mathematicaly,ifoneis`right'thensoistheother.Physicaly,though,theycarryverydifferentimplicationsabouthowtheworldworks.Ourpointisthat,asfortheclassicalparticle,theirmathematicalequivalencedoesnotrequireyoutoaccepttheirphysicaltruthasdescriptionsofreality.AnymorethantheequivalenceofNewton'slawswiththeprincipleofleastactionobligesyoutobelieveininteligentparticlesthatcanpredictthefuture.

Themany-worldsinterpretationofquantummechanics,then,isrestingondodgy

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groundeventhoughitsmathematicalfoundationsareimpeccable.

Buttheusualpresentationofthatinterpretationgoesfurther,byaddingaheftydoseofnarrativium.ThisispreciselywhatappealstoSFauthors,butit'sapitythatitstretchestheinterpretationwelpastbreaking-point.

Whatweareusualytoldisthis.Ateveryinstantoftime,wheneverachoicehastobemade,theuniversesplitsintoaseriesof`paralelworlds'inwhicheachofthechoiceshappens.Yes,inthisworldyougotup,hadcornflakesforbreakfast,andwalkedtowork.Butsomewhereòutthere'inthevastnessofthemultiverse,thereisanotheruniverseinwhichyouhadkippersforbreakfast,whichmadeyouleavethehouseaminutelater,sothatwhenyouwalkedacrosstheroadyouhadanargumentwithabus,andlost,fataly.

What'swronghereisnot,strangelyenough,thecontentionthatthisworldis`realy'asumofmanyothers.Perhapsitis,onaquantumlevelofdescription.Whynot?Butitiswrongtodescribethosealternativeworldsinhumanterms,asscenarioswhereeverythingfolowsanarrativethatmakessensetothehumanmind.Asworldswherèbus'or`kipper'haveanymeaningatal.Anditisevenlessjustifiabletopretendthateverysingleoneofthoseparalelworldsisaminorvariationonthisone,inwhichsomehuman-levelchoicehappensdifferently.

Ifthoseparalelworldsexistatal,theyaredescribedbychangingvariouscomponentsofaquantumwavefunctionwhosecomplexityisbeyondhumancomprehension.Theresultsneednotresemblehumanlycomprehensiblescenarios.Justasthesoundofaclarinetcanbedecomposedintopuretones,butmostcombinationsofthosetonesdonotcorrespondtoanyclarinet.

Thenaturalcomponentsofthehumanworldarebusesandkippers.Thenaturalcomponentsofthequantumwavefunctionoftheworldarenotthequantumwavefunctionsofbusesandkippers.Theyarealtogetherdifferent,andtheycarveuprealityinadifferentway.Theyflipelectronspins,rotatepolarisations,shiftquantumphases.

Theydonotturncornflakesintokippers.

It'sliketakingastoryandmakingrandomchangestotheletters,shiftingwordsaround,probablychangingtheinstructionsthattheprinterusestomaketheletters,sothattheycorrespondtonoalphabetknowntohumanity.InsteadofstartingwiththeAnkh-MorporknationalanthemandgettingtheHedgehog

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Song,youjustgetameaninglessjumble.Whichisperhapsaswel.

AccordingtoMaxTegmark,writingintheMay2003issueofScientificAmerican,physicistscurrentlyrecognisefourdistinctlevelsofparaleluniverses.Atthefirstlevel,somedistantregionoftheuniversereplicates,almostexactly,whatisgoingoninourownregion.Thesecondlevelinvolvesmoreorlessisolated`bubbles',babyuniverses,inwhichvariousattributesofthephysicallaws,suchasthespeedoflight,aredifferent,thoughthebasiclawsarethesame.ThethirdlevelisEverett'smany-worldsquantumparalelism.Thefourthincludesuniverseswithradicalydifferentphysicallaws-notmerevariationsonthethemeofourownuniverse,buttotalydistinctsystemsdescribedbyeveryconceivablemathematicalstructure.

Tegmarkmakesaheroicattempttoconvinceusthataloftheselevelsrealydoexist-thattheymaketestablepredictions,arescientificalyfalsifiableifwrong,andsoon.HeevenmanagestoreinterpretOccam'srazor,thephilosophicalprinciplethatexplanationsshouldbekeptassimpleaspossible,tosupporthisview.

Alofthis,speculativeasitmayseem,isgoodfrontiercosmologyandphysics.It'sexactlythekindoftheorisingthataScienceofDiscworldbookoughttodiscuss:imaginative,mind-boggling,cutting-edge.We'vecometothereluctantconclusion,though,thattheargumentshaveseriousflaws.

Thisisapity,becausetheconceptofparalelworldsisdrippingwithenoughnarrativiumtomakeanySFauthorout-salivatePavlov'sdogs.

We'lsummariseTegmark'smainpoints,describesomeoftheevidencethathecitesintheirfavour,offerafewcriticisms,andleaveyoutoformyourownopinions.

Level1paralelworldsariseif-because-spaceisinfinite.Notsofarbackwetoldyouitisfinite,becausetheBigBanghappenedafinitetimeagosoit'snothadtimetoexpandtoaninfiniteextent.[1]Apparently,though,dataonthecosmicmicrowavebackgrounddonotsupportafiniteuniverse.Eventhoughaverylargefiniteonewouldgeneratethesamedata.

Ìsthereacopyofyoureadingthisarticle?'Tegmarkasks.Assumingtheuniverseisinfinite,hetelsusthatèventhemostunlikelyeventsmusttakeplacesomewhere'.Acopyofyouislikelierthanmany,soitmusthappen.

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Where?Astraightforwardcalculationindicatesthat`youhaveatwininagalaxyabout10tothepower10^21metresfromhere'.Not10^21metres,whichisalready25timesthesizeofthecurrentlyobservableuniverse,but1folowedby1028zeros.Notonlythat:acompletecopyof(theobservablepartof)ouruniverseshouldexistabout10tothepower10^118

metresaway.Andbeyondthat...

Weneedagoodwaytotalkaboutverybignumbers.Symbolslike10^118

aretooformal.Writingoutalthezerosispointless,andusualyimpossible.Theuniverseisbig,andthemultiverseissubstantialybigger.

Puttingnumberstohowbigisnotentirelystraightforward,andfindingsomethingthatcanalsobetypesetisevenharder.

[1]Curiously,itcouldexpandtoinfinityinafinitetimeifitacceleratedsufficientlyrapidly.Expandbyonelight-yearafteroneminute,byanotherlight-yearafterhalfaminute,byanotherafteraquarterofaminute...doaZeno,andaftertwominutes,youhaveaninfiniteuniverse.Butit'snotexpandingthatfast,andnoonethinksitdidsointhepast,either.

Fortunately,we'vealreadysolvedthatproblemwithourearlierconvention:ifùmpty'isanynumber,thenùmptyplex'wilmean10^umpty,whichis1

folowedbyumptyzeros.

Whenumpty=118weget118plex,whichisroughlythenumberofprotonsintheuniverse.Whenumptyis118plexweget118plexplex,whichisthenumberthatTegmarkisaskingustothinkabout,10tothepower10tothepower118.ThosenumbersarisebecauseàHubblevolume'ofspace-

onethesizeoftheobservableuniverse-hasalargebutfinitenumberofpossiblequantumstates.

Thequantumworldisgrainy,withalowerlimittohowfarspaceandtimecanbedivided.SoasufficientlylargeregionofspacewilcontainsuchavastnumberofHubblevolumesthateveryoneofthosequantumstatescanbeaccommodated.Specificaly,aHubblevolumecontains118plexprotons.Eachhastwopossiblequantumstates.Thatmeansthereare2tothepower118plex

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possibleconfigurationsofquantumstatesofprotons.

Oneoftheusefulrulesinthistypeofmega-arithmeticisthatthèlowest'

numberintheplexifiedstack-here2-canbechangedtosomethingmoreconvenient,suchas10,withoutgreatlyaffectingthetopnumber.So,inroundnumbers,aregion118plexplexmetresacrosscancontainonecopyofeachHubblevolume.

Level2worldsariseontheassumptionthatspacetimeisakindoffoam,inwhicheachbubbleconstitutesauniverse.Themainreasonforbelievingthisisìnflation',atheorythatexplainswhyouruniverseisrelativisticalyflat.Inaperiodofinflation,spacerapidlystretches,anditcanstretchsofarthatthetwoendsofthestretchedbitbecomeindependentofeachotherbecauselightcan'tgetfromonetotheotherfastenoughtoconnectthemcausaly.Sospacetimeendsupasafoam,andeachbubbleprobablyhasitsownvariantofthelawsofphysics-withthesamebasicmathematicalform,butdifferentconstants.

Level3paralelworldsarethosethatappearinthemany-worldsinterpretationofquantummechanics,whichwe'vealreadytackled.

Everythingdescribedsofarpalesintoinsignificancewhenwecometolevel4.Here,thevariousuniversesinvolvedcanhaveradicalydifferentlawsofphysicsfromeachother.Alconceivablemathematicalstructures,Tegmarktelsus,existhere:

Howaboutauniversethatobeysthelawsofclassicalphysics,withnoquantumeffects?Howabouttimethatcomesindiscretesteps,asforcomputers,insteadofbeingcontinuous?Howaboutauniversethatissimplyanemptydodecahedron?InthelevelNmultiverse,althesealternativerealitiesactualyexist.

Butdothey?

Inscience,yougetevidencefromobservationsorfromexperiments.

DirectobservationaltestsofTegmark'shypothesisarecompletelyoutofthequestion,atleastuntilsomeremarkablespacefaringtechnologycomesintobeing.Theobservableuniverseextendsnomorethan27plexmetresfromtheEarth.Anobject(eventhesizeofourvisibleuniverse)thatis118plexplex

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metresawaycannotbeobservednow,andnoconceivableimprovementontechnologycangetroundthat.Itwouldbeeasierforabacteriumtoobservetheentireknownuniversethanforahumantoobserveanobject118plexplexmetresaway.

Wearesympathetictotheargumentthattheimpossibilityofdirectexperimentaltestsdoesnotmakethetheoryunscientific.Thereisnodirectwaytotestthepreviousexistenceofdinosaurs,orthetiming(oroccurrence)oftheBigBang.Weinferthesethingsfromindirectevidence.

Sowhatindirectevidenceisthereforinfinitespaceanddistantcopiesofourownworld?

Spaceisinfinite,Tegmarksays,becausethecosmicmicrowavebackgroundtelsusso.Ifspacewerefinite,thentracesofthatfinitudewouldshowupinthestatisticalpropertiesofthecosmicbackgroundandthevariousfrequenciesofradiationthatmakeitup.

Thisisacuriousargument.Onlyayearorsoago,somemathematiciansusedcertainstatisticalfeaturesofthecosmicmicrowavebackgroundtodeducethatnotonlyistheuniversefinite,butthatitisshapedabitlikeafootbal.*Thereisapaucityofverylong-wavelengthradiation,andthebestreasonfornotfindingitisthattheuniverseistoosmaltoaccommodatesuchwavelengths.Justasaguitarstringametrelongcannotsupportavibrationwithawavelengthof100metres-thereisn'troomtofitthewaveintotheavailablespace.

Themainotheritemofevidenceisofaverydifferentnature-notanobservationassuch,butanobservationabouthowweinterpretobservations.Cosmologistswhoanalysethemicrowavebackgroundtoworkouttheshapeandsizeoftheuniversehabitualyreporttheirfindingsintheform`thereisaprobabilityofoneinathousandthatsuchandsuchashapeandsizecouldbeconsistentwiththedata'.Meaningthatwith99.9

percentprobabilityweruleoutthatsizeandshape.TegmarktelsusthatonewaytointerpretthisisthatatmostoneHubblevolumeinathousand,ofthatsizeandshape,wouldexhibittheobserveddata.`Thelessonisthatthemultiversetheorycanbetestedandfalsifiedevenwhenwecannotseetheotheruniverses.Thekeyistopredictwhattheensembleofparaleluniversesisandtospecifyaprobabilitydistributionoverthatensemble.'

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Thisisaremarkableargument.Fataly,itconfusesactualHubblevolumeswithpotentialones.Forexample,ifthesizeandshapeunderconsiderationisàfootbalabout27plexmetresacross[1]-afairguessforourownHubblevolume-thentheòneinathousand'probabilityisacalculationbasedonapotentialarrayofonethousandfootbalsofthatsize.Thesearenotpartofasingleinfiniteuniverse:theyaredistinctconceptual`points'inaphasespaceofbig[1]ActualyamoresophisticatedgadgetcaledthePoincaredodecahedralspace,aslightlyweirdshapeinventedmorethanacenturyagotoshowthattopologyisnotassimpleaswe'dlikeittobe.Butpeopleunderstand'footbal'.

footbals.Ifyoulivedinsuchafootbalandmadesuchobservations,thenyou'dexpecttogettheobserveddataonaboutoneoccasioninathousand.

Thereisnothinginthisstatementthatcompelsustoinfertheactualexistenceofthosethousandfootbals-letalonetoembedthelotinasingle,biggerspace,whichiswhatwearebeingaskedtodo.Ineffect,Tegmarkisaskingustoacceptageneralprinciple:thatwheneveryouhaveaphasespace(statisticianswouldsayasamplespace)withawel-

definedprobabilitydistribution,theneverythinginthatphasespacemustbereal.

Thisisplainwrong.

Asimpleexampleshowswhy.Supposethatyoutossacoinahundredtimes.YougetaseriesoftossessomethinglikeHHTTTHH...THH.Thephasespaceofalpossiblesuchtossescontainsprecisely2100suchsequences.Assumingthecoinisfair,thereisasensiblewaytoassignaprobabilitytoeachsuchsequence-namelythechanceofgettingitisonein2100.Andyoucantestthat`distribution'ofprobabilitiesinvariousindirectways.Forinstance,youcancarryoutamilionexperiments,eachyieldingaseriesof100tosses,andcountwhatproportionhas50headsand50tails,or49headsand51tails,whatever.Suchanexperimentisentirelyfeasible.

IfTegmark'sprincipleisright,itnowtelsusthattheentirephasespaceofcoin-tossingsequencesrealydoesexist.Notasamathematicalconcept,butasphysicalreality.

However,coinsdonottossthemselves.Someonehastotossthem.

Ifyoucouldtoss100coinseverysecond,itwouldtakeabout24plexyearsto

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generate2100experiments.Thatisroughly100triliontimestheageoftheuniverse.Coinshavebeeninexistenceforonlyafewthousandyears.

Thephasespaceofalsequencesof100cointossesisnotreal.Itexistsonlyaspotential.

SinceTegmark'sprincipledoesn'tworkforcoins,itmakesnosensetosupposethatitworksforuniverses.

Theevidenceadvancedinfavouroflevel4paralelworldsiseventhinner.ItamountstoamysticalappealtoEugeneWigner'sfamousremarkabout`theunusualeffectivenessofmathematics'asadescriptionofphysicalreality.Ineffect,Tegmarktelsusthatifwecanimaginesomething,thenithastoexist.

WecanimagineapurplehippopotamusridingabicyclealongtheedgeoftheMilkyWaywhilesingingMonteverdi.Itwouldbelovelyifthatmeantithadtoexist,butatsomepointarealitycheckisinorder.

Wedon'twanttoleaveyouwiththeimpressionthatweenjoypouringcoldwaterovereveryimaginativeattempttoconveyafeelingforsomeoftheremarkableconceptsofmoderncosmologyandphysics.Sowe'lendwithaveryrecentadditiontothestableofparalelworlds,whichhasquiteafewthingsgoingforit.Perhapsunsurprisingly,themainthingnotcurrentlygoingforitisashredofexperimentalevidence.

Thenewtheoryontheblockisstringtheory.Itprovidesaphilosophicalysensibleanswertotheage-oldquestion:whyarewehere?Anditdoessobyinvokinggiganticnumbersofparaleluniverses.

Itisjustmuchmorecarefulhowithandlesthem.

Oursourceisanarticle,`TheStringTheoryLandscape'byRaphaelBoussoandJosephPolchinski,intheSeptember2004issueofScientificAmerican-aspecialissueonthethemeofAlbertEinstein.

Ifthereisasingleproblemthatoccupiesthecoreofmodernphysics,itisthatofunifyingquantummechanicswithrelativity.Thissearchforàtheoryofeverything'isneededbecausealthoughbothofthosetheoriesareextraordinarilysuccessfulinhelpingustounderstandandpredictvariousaspectsofthenaturalworld,theyarenottotalyconsistentwitheachother.

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Findingaconsistent,unifiedtheoryishard,andwedon'tyethaveone.Butthere'sonemathematicalyattractiveattempt,stringtheory,whichisconceptualyappealingeventhoughthere'snoobservationalevidenceforit.

Stringtheoryholdsthatwhatweusualyconsidertobeindividualpointsofspacetime,dimensionlessdotswithnointerestingstructureoftheirown,areactualyvery,verytinymultidimensionalsurfaceswithcomplicatedshapes.Thestandardanalogyisagardenhose.Seenfromsomewayoff,ahoselookslikealine,whichisaonedimensionalspace-thedimensionbeingdistancealongthehose.Lookmoreclosely,though,andyouseethatthehosehastwoextradimensions,atrightanglestothatline,andthatitsshapeinthosedirectionsisacircularband.

Maybeourownuniverseisabitlikethathosepipe.Unlesswelookveryclosely,alweseeisthreedimensionsofspaceplusoneoftime-relativity.

Anawfullotofphysicsisobservedinthosedimensionsalone,sophenomenaofthattypehaveanicefour-dimensionaldescription-relativityagain.Butotherthingsmighthappenalongextràhidden'dimensions,likethethicknessofthehose.Forinstance,supposethatateachpointoftheapparentfour-dimensionalspacetime,whatseemstobeapointisactualyatinycircle,stickingoutatrightanglestospacetimeitself.Thatcirclecouldvibrate.Ifso,thenitwouldresemblethequantumdescriptionofaparticle.Particleshavevarious`quantumnumbers'suchasspin.Thesenumbersoccuraswholenumbermultiplesofsomebasicamount.Sodovibrationsofacircle:eitheronewavefitsintothecircle,ortwo,orthree...

butnottwoandaquarter,say.

Thisiswhyit'scaled`stringtheory'.Eachpointofspacetimeisreplacedbyatinyloopofstring.

Inordertoreconstructsomethingthatagreeswithquantumtheory,however,wecan'tactualyuseacircularstring.Therearetoomanydistinctquantumnumbers,andplentyofotherproblemsthathavetobeovercome.

Thesuggestionisthatinsteadofacircle,wehavetouseamorecomplicated,higher-dimensionalshape,knownasàbran'.[1]Thinkofthisasasurface,onlymoreso.Therearemany[1]Derivedfromapun:m-branfor`membrane'.Openingupjokesaboutno-branesandp-branes.Ohwel.

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distincttopologicaltypesofsurface:asphere,adoughnut,twodoughnutsjoinedtogether,threedoughnuts...andinmoredimensionsthantwo,therearemoreexoticpossibilities.

Particlescorrespondtotinyclosedstringsthatlooparoundthebrane.

Therearelotsofdifferentwaystoloopastringroundadoughnut-oncethroughthehole,twice,threetimes...Thephysicallawsdependontheshapeofthebraneandthepathsfolowedbytheseloops.

Thecurrentfavouritebranehassixdimensions,makingteninal.Theextradimensionsarethoughttobecurledupverytightly,smalerthanthePlancklength,whichisthesizeatwhichtheuniversebecomesgrainy.Itisvirtualyimpossibletoobserveanythingthatsmal,becausethegraininessblurseverythingandthefinedetailcannotbeseen.Sothere'snohopeofobservinganyextradimensionsdirectly.However,thereareseveralwaystoinfertheirpresenceindirectly.Infact,therecentlydiscoveredaccelerationintherateofexpansionoftheuniversecanbeexplainedinthatmanner.Ofcourse,thisexplanationmaynotbecorrect:weneedmoreevidence.

Theideasherechangealmostbytheday,sowedon'thavetocommitourselvestothecurrentlyfavouredsix-dimensionalset-up.Wecancontemplateanynumberofdifferentbranesanddifferentlyarrangedloops.

Eachchoice-calitaloopybrane-hasaparticularenergy,relatedtotheshapeofthebrane,howtightlyitiscurledup,andhowtightlytheloopswindroundit.Thisenergyisthe'vacuumenergy'oftheassociatedphysicaltheory.Inquantummechanics,avacuumisaseethingmassofparticlesandantiparticlescomingintoexistenceforabriefinstantbeforetheycolideandannihilateeachotheragain.Thevacuumenergymeasureshowviolentlytheyseethe.Wecanusethevacuumenergytoinferwhichloopybranecorrespondstoourownuniverse,whosevacuumenergyisextraordinarilysmal.Untilrecentlyitwasthoughttobezero,butit'snowthoughttobeabout1/120plexunits,whereaunitisonePlanckmasspercubicPlancklength,whichisagoogolgrammespercubicmetre.

Wenowencounteracosmic`threebears'story.MachoDaddyBearprefersavacuumenergylargerthan+1/118plexunits,butsuchaspacetimewouldbesubjecttolocalexpansionsfarmoreenergeticthanasupernova.WimpyMummy

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Bearprefersavacuumenergysmalerthan-

1/120plexunits(notetheminussign),butthenspacetimecontractsinacosmiccrunchanddisappears.BabyBearandGoldilocksliketheirvacuumenergytobèjustright':somewhereintheincrediblytinyrangebetween+1/118plexand-1/120plexunits.ThatistheGoldilockszoneinwhichlifeasweknowitmightpossiblyexist.

ItisnocoincidencethatweinhabitauniversewhosevacuumenergyliesintheGoldilockszone,becausewearelifeasweknowit.Ifwelivedinanyotherkindofuniverse,wewouldbelifeaswedon'tknowit.Notimpossible,butnotus.

Thisisouroldfriendtheanthropicprinciple,employedinanentirelysensiblewaytorelatethewaywefunctiontothekindofuniversethatweneedtofunctionin.Thedeepquestionhereisnot`whydoweliveinauniverselikethat?',but`whydoesthereexistauniverselikethat,forustolivein?'Thisisthevexedissueofcosmologicalfine-tuning,andtheimprobabilityofarandomuniversehittingjusttherightnumbersisoftenusedtoprovethatsomething-theyalwayssay`Wedon'tknow,couldbeanalien,'butwhatthey'realthinkingis:'God'-musthavesetouruniverseuptobejustrightforus.

Thestringtheoristsaremadeofsternerstuff,andtheyhaveamoresensibleanswer.

In2000BoussoandPolchinskicombinedstringtheorywithanearlierideaofStevenWeinbergtoexplainwhyweshouldn'tbesurprisedthatauniversewiththerightlevelofvacuumenergyexists.Theirbasicideaisthatthephasespaceofpossibleuniversesisabsolutelygigantic.Itisbiggerthan,say,500plex.Those500plexuniversesdistributetheirvacuumenergiesdenselyintherange-1to+1units.Theresultingnumbersaremuchmorecloselypackedthanthe1/118plexunitsthatdeterminethescaleoftheàcceptable'rangeofvacuumenergiesforlifeasweknowit.

Althoughonlyaverytinyproportionofthose500plexuniversesfalinsidethatrange,therearesomanyofthemthatthatatinyproportionisstilabsolutelygigantic-here,around382plex.Soawhackinggreat382plexuniverses,fromaphasespaceof500plexloopybranes,arecapableofsupportingourkindoflife.

However,that'sstilaverysmalproportion.Ifyoupickaloopybraneatrandom,theoddsareoverwhelminglygreatthatitwon'tfalinsidetheGoldilocksrange.

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Notaproblem.Thestringtheoristshaveananswertothat.Ifyouwaitlongenough,suchauniversewilnecessarilycomeintobeing.Infact,aluniversesinthephasespaceofloopybraneswileventualybecomethèreal'universe.Andwhentherealuniverse'sloopybranegetsintotheGoldilocksrange,theinhabitantsofthatuniversewilnotknowaboutalthatwaiting.Theirsenseoftimewilstartfromtheinstantwhenthatparticularloopybranefirstoccurred.

Stringtheorynotonlytelsusthatwe'reherebecausewe'rehere-itexplainswhyasuitablèhere'mustexist.

Thereasonwhyalofthose500plexorsouniversescanlegitimatelybeconsidered`real'instringtheorystemsfromtwofeaturesofthattheory.

Thefirstisasystematicwaytodescribealthepossibleloopybranesthatmightoccur.Thesecondinvokesabitofquantumtoexplainwhy,inthelongrun,theywiloccur.Briefly:thephasespaceofloopybranescanberepresentedasanènergylandscape',whichwe'lnamethebranescape.

Eachpositioninthelandscapecorrespondstoonepossiblechoiceofloopybrane;theheightatthatpointcorrespondstotheassociatedvacuumenergy.

Peaksofthebranescaperepresentloopybraneswithhighvacuumenergy,valeysrepresentloopybraneswithlowvacuumenergy.Stableloopybraneslieinthevaleys.Universeswhosehiddendimensionslooklikethoseparticularloopybranesarethemselvesstable...sothesearetheonesthatcanexist,physicaly,formorethanasplitsecond.

Inhilydistrictsoftheworld,thelandscapeisrugged,meaningthatithasalotofpeaksandvaleys.Theygetclosertogetherthanelsewhere,buttheyarestilgeneralyisolatedfromeachother.Thebranescapeisveryruggedindeed,andithasahugenumberofvaleys.Butalofthevaleys'vacuumenergieshavetofitinsidetherangefrom-1unitsto+1units.Withsomanynumberstopackin,theygetsquashedveryclosetogether.

Inorderforauniversetosupportlifeasweknowit,thevacuumenergyhastolieintheGoldilockszonewhereeverythingisjustright.Andtherearesomanyloopybranesthatahugenumberofthemmusthavevacuumenergiesthatfalinsideit.

Vastlymorewilfaloutsidethatrange,butnevermind.

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Thetheoryhasonemajoradvantage:itexplainswhyouruniversehassuchasmalvacuumenergy,withoutrequiringittobezero-which,wenowknow,itisn't.

Theupshotofalthemaths,then,isthateverystableuniversesitsinsomevaleyofthebranescape,andanawfullotofthem(thoughatinyproportionofthewhole)lieintheGoldilocksrange.Butalofthoseuniversesarepotential,notactual.Thereisonlyonerealuniverse.Soifwemerelypickaloopybraneatrandom,thechanceofhittingtheGoldilockszoneisprettymuchzero.Youwouldn'tbetonahorseatthoseodds,letaloneauniverse.

Fortunately,goodoldquantumgalopstoourrescue.Quantumsystemscan,anddo,`tunnel'fromoneenergyvaleytoanother.Theuncertaintyprincipleletsthemborrowenoughenergytodothat,andthenpayitbacksoquicklythatthecorrespondinguncertaintyabouttimingpreventsanyonenoticing.So,ifyouwaitlongenough-umptyplexplexplexyears,perhaps,orumptyplexplexplexplexifthat'stooshort-thenasinglequantumuniversewilexploreeveryvaleyintheentirebranescape.Alongtheway,atsomestageitfindsitselfinaGoldilocksvaley.Lifelikeoursthenarises,andwonderswhyit'sthere.

It'snotawareoftheumptyplexplexplexplexyearsthathavealreadypassedinthemultiverse:justofthefewbilionthathavepassedsincethewanderinguniversetunneleditswayintotheGoldilocksrange.Now,andonlynow,doitshumanlikeinhabitantsstarttoaskwhyit'spossibleforthemtoexist,givensuchridiculousoddstothecontrary.Eventualy,ifthey'rebrightenough,theyworkoutthatthankstothebranescapeandquantum,thetrueoddsareadeadcertainty.

It'sabeautifulstory,evenifitturnsouttobewrong.

FIFTEEN

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AUDITORSOFREALITY

ITWASONEHOURLATER.WizardswererangedinrowsacrossthewidthoftheGreatHalinavarietyofcostumes,butmostlyinwhatmightbecaledEarlyTrouser;despiteRincewind'sviewonnudity,agrubbyshirtandpantswouldpasswithoutcommentinmanyagesandcountriesandleadtofewerarrests.

'Right,then,'saidRidculy,stridingalongtheranks'We'vekeptalthisverysimplesothatevenprofessorscanunderstand!PonderStibbonshasgivenalofyouyourtasks!'Hestoppedinfrontofamiddle-agedwizard.

'You,sir,whoareyou?'

'Don'tyouknow,sir?'saidthewizard,takenaback.

'Slippedm'mind,man!'saidRidculy.'Biguniversity,can'tbeexpectedtorecogniseeveryone!'

'It'sPennysmart,sir.ProfessorofExtremeHorticulture.''Anygoodatit?'

'Yes,sir!'

'Anystudents?'

'No,sir!'saidPennysmart,lookingoffended.

'That'swhatIliketohear!Andwhatwilyoubedoin'today?''First,itappears,Ishalbedroppedwaist-deepinalagooninthe,the-'hestopped,andfumbledapieceofpaperoutofhispocket'-Keelingislands,whereIshalattackthesandbottomroundmewiththisrake,'hehelduptheimplement,'andthenreturnhereassoonasIseeanyhumans.'

'Andhowwilyoudothat?'

'Sayaloud,"ReturnMe,Hex",'saidPennysmart,smartly.

'Weldone,goodman,'saidtheArchchancelor.Heraisedhisvoice.

'Rememberthat,everyone!Exactlythosewords!Writethemdownifyoucan't

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rememberthem.Hexwilbringyoubackonthelawnoutsidethebuilding.Therewilbehundredsofyouandmanyofyouhaveseveraltasks,sowedon'twantanycolisions!Now,if-'

'Excuseme,'saidPennysmart,raisingahand.'Yes?'

'WhywilIbestandinginalagoonflailingaroundwitharake,please?'

'Becauseifyoudon'tdothat,Darwinwiltreadonthedorsalspineofanextremelypoisonousfish,'saidPonderStibbons.`Now-''Excusemeagain,please,'Pennysmartsaid.'Yes?'

'Whywon'tItreadonthisfish?'

'Becauseyouwilbelookin'whereyouaretreadin',MrPennysmart,'roaredRidculy.

Butaforestofotherhandshadgoneup.AbouttheonlywizardwithoutahandaloftwasRincewind,whowasstaringgloomilyathisfeet.

'What'salthisabout?'saidtheArchchancelor,irritably.'Why.haveIgottomoveachairsixinches?'

'WhyhaveIgottofilupaholeinthemiddleofaprairie?''WhyhaveIgottobideapairoftrousers?''WhyhaveIgottostuffaletterboxfulofstarvedsnails?'Ponderwavedhisclipboardwildlytosilencetheclamour.

'BecauseotherwiseDarwinwouldhavefalenoffachairorbeenthrownfromahorseorwouldhavebeenstruckbyastonehurledbyarioteroranunwiseletterwouldhavereacheditsdestination,'hesaid.

'Buttherearemorethantwothousandtasks,soIcan'texplaineveryone.

Someofthemarethestartofaquiteastonishingcausalchain.'

`Wearesupposedtodevelopquestioningminds,youknow,'someonemuttered.

`Yes,butnotregardinguniversitypolicy!'saidRidculy.`Youalhaveverysimplejobstodo!Gentlemen,MrStibbonswilcaloutyournames,andyouwilstepsmartlyintothecircle!Overtoyou,MrStibbons!'

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PonderStibbonspickedupadifferentclipboard.Hewasbeginningtocolectclipboards.Theyproclaimedorderinanincreasinglyhard-to-understandworld.That'salI'veeverrealywanted,hethought.Ijustwanttofeelthatthingsarebeingtickedoffproperly.

`Now,chaps,'hesaid.`Thisshouldnotbehard,astheArchchancelorhassaid.Ifatalpossibledon'ttalktoanyoneanddon'ttouchanything.Inandout,that'stheticket.Iwantthisdonefast.Ihavea...theoryaboutthat.Sodon'twastetime,whereveryougo.Arewealready?Verywel...

Aardvarker,ProfessorA...'

Onebyone,withconfidenceortrepidationoramixtureofboth,wizardssteppedintoHex'scircleoflightandvanished.Astheydidso,littlepointy-hattedwizardsymbolsappearedatpointsinthetangleoflightsabove.

Rincewindwatchedgloomily,anddidn'tjoinintheraggedcheeras,onebyone,redcirclesbegantowinkout.

Ponderhadtakenhimasideearlierandhadexplainedthat,sinceRincewindwassoexperiencedatthissortofthing,hewasgoingtobegivenfourofthemost,er,interestingtasks.Thatwashowhehadputit:'er,interesting'.Rincewindknewalabout'er,interesting'.Therewasagiantsquidouttherewithhisnameonit,that'swhatitmeant.

Amovementattheendonthehalmadehimlookaround.Itwasachest,ametal-boundboxofthekindfavouredbypeoplewhoburytreasure,anditwalkedonhundredsoflittlepinklegs.Hegroaned.He'dleftitasleeponthewardrobeinhisbedroom,withitsfeetintheair.

'Hmm?'hesaid.

`Rincewind!Offyougo,bestofluck!'Ponderrepeated.`Hurryup!'Therewasnothingforit.Rincewindwalkedintothecircle,andfeloverastheshipmovedgentlyunderhim.

Itwasdawn,andaclammyseamistwasdriftingacrossthedeck.Riggingcreaked,thewaterlappedfarbelow.Therewasnoothersound.Theairsmeledwarmandexotic.

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Therewasasmalcannononlyafewfeetaway.Rincewindknewaboutthem.Hewastheonlywizardtohaveseenone,overintheAgateanEmpire,wheretheywereknownas`BarkingDogs'.Hewassurethatoneoftherulesassociatedwiththemwas`donotstandinfront'.

Slowly,hereachedinsidehisshirtandpuledouthispointyhat.Itwasred,orrather,itwasthecolourthatredbecomesafterbeingwashed,eaten,retrieved,scorched,buried,crushed,engulfed,washedagainandwrungoutfar,fartoooften.

Nowearingofpointyhats?Weretheymad?Hepuledatitabittogetitbacktoitscomfortableshapelessshape,andputiton.Thatfeltmuchbetter.Apointyhatmeantyouweren'tjustanyone.

Heunroledhisinstructions.

1.Removebalfrom`cannon'

Therewasnoonearound.Therewasastackofmetalbalsbythecannon.

Rincewindpuledthebarrelaroundwithsomeeffort,feltdownthehole,andgruntedashisfingerstouchedthetopofanotherbalatthefarend.

Howcouldhegetitout?ThewaytogetabaloutofaBarkingDogwastosetamatchtoitstail,butPonderhadsaidthiswasn'tanoption.Hecastaround,andsawabundleoftoolsbythestack;onewasarodwithanendlikeasuper-corkscrew.

Carefuly,hepusheditdownthecannon,wincingateveryclink.Twicehefeltthecurvedspringybitsengagewiththebal,andtwiceitcameawayandroledbackwithathud.

Atthethirdattempthewasabletogetthetappedbalalmostoutofthemouthofthebarrel,andslidhisfingersunderit.

Wel,thatwasn'ttoohard,wasit?Hedroppeditovertheside,wheretheseaswaloweditwitha'plomp!'

Thiscausednostiranywhere.Jobdone,andnothinghorriblehadhappenedatal!Hepuledascrapofpaperoutofhispocket.Itwasimportanttogetthewords

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right.

`Return-'hebegan,andstopped.Withalittlemetalicgrindingnoise,anotherbalroledgentlyoffthepile,acrossthedeck,andleaptintothecannon'smouth.

Ò-kay,'saidRincewindslowly.Ofcourse.Obviously.Whyhadhethoughtotherwiseforevenonesecond?

Sighing,hepickedupthebalgrasper,rammeditdownthebarrel,caughtthebal,andjerkeditoutsohardthatitwouldhavemadeagiveawaynoisehittingthedeck.Fortunately,itlandedonRincewind'sfoot.

Alittlemetalicsounddisturbedhimwhilehewaslyingacrossthebarrelmakingthetraditional'gheeee'noiseofthosewhoarescreamingthroughclenchedteeth.

Itwasthenoiseofanothercannonbalrolingacrossthedeck.Hejumpedonit,pickeditup,andfeltaslightresistancetryingtotugitoutofhishands.Hewrenchedagainsttheinvisibleforce,spunaroundandthebalflewoutofhishandsandovertherail.

Thistimethe'plomp!'causedaninterrogatorymumblefrombelowdecks.

Thelastremainingbalstartedtoroltowardsthecannon.

Òhnoyoudon't!'snarledRincewind,andgrabbedit.Againtheforcetriedtopulthebalawayfromhim,butheclungontightly.

Therewasthesoundoffootstepsclimbingstairs.Somewhereclose,inthefog,someonesoundedangry.

TheninthebilowsinfrontofRincewindtherewas...something.Hecouldn'tmakeouttheshape,butitdisturbedthefog,makinganoutlineofsorts.Itlookedlike

Itletgoassomeonehurriedcloser.Rincewindgrowledintriumph,staggeredbackwards,tippedovertherailand,stilclutchingthecannonbal,went`plomp!'

`Lookattheredcircles,sir!'shoutedPonder.

Erraticaly,inthedriftingtangleoflights,theredcircleswerewinkingout.

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Theyelowlinewasextending.

`That'sthestyle,MrStibbons!'theArchchancelorroared.`Keeppoundingaway!'

Wizardswerescuttlingthroughthehal,gettingfreshinstructions,catchingtheirbreathanddisappearinginthecircleagain.

RidculynoddedatthestretchercontainingthescreamingPennysmart,asitwashurriedawaytotheInfirmary.

`Neverseenthatshadeofpurpleonaleg,'hesaid.Ìtoldhimtolookwherehewasgoing.Youheardme,didn'tyou?'

`Hesayshewasdroppedrightontopofthefish,'saidPonder.Ì'mafraidHexisrunningattheverylimitofhispower,sir.We'rebendinganentiretimeline.You'vegottoexpectsomeaccidents.Afewofthereturningwizardsarereappearinginthefountain.Wejusthavetoacceptthatit'sbetterthanthemreappearinginsidewals.'

Ridculysurveyedthethrong,andsaid:`Herecomesonefromthefountain,bythelookofit...'

Rincewindlimpedin,hisfacelikethunder,waterstilstreamingoffhim,withsomethinggraspedinhishands.Halfwayacrossthehalafishfeloutofhisrobe,inobediencetotheunbreakablelawsofhumour.

HereachedPonder,anddroppedthecannonbalonthefloor.

`Doyouknowhowharditistoshoutunderwater?'hedemanded.

`ButIseeyouweresuccessful,Rincewind,'saidRidculy.

Rincewindlookedup.Aloverthestreaminglines,littlepointywizardsymbolswereappearinganddisappearing.

`Noonetoldmeitwouldfightback!Itfoughtback!Thecannontriedtoloaditself.'

'Aha!'saidRidculy.`Theenemyisrevealed!We'renearlythere!Iftheyare

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breakingthe-'

'ItwasanAuditor,'saidRincewind,flatly.ÌtwastryingtobeinvisiblebutIsawitoutlinedinthefog.'

Ridculysaggedalittle.Acertainexuberancefadedfromhisface.Hesaid,Òh,darn,'becauseanamusingmisunderstandinginhisyouthhadledhimtobelievethatthiswastheworstpossiblewordyoucouldsay.

`We'vefoundnoevidenceofthem,'saidPonderStibbons.

`Here?Didwelook?Wewouldn'tfindanyanyway,wouldwe?'

saidRidculy.`They'dshowupasnaturalforces.'

`Buthowcouldtheyexisthere?Althosethingsworkbythemselveshere!'

`Samewaywedid?'saidRincewind.Àndthey'lmeddlewithanything.

Youknowthem.Andtheyrealy,realyhatepeople...'

Auditors:personificationsofthingsthathavenopersonalitythatcanbeimagined.Windandrainareanimate,andthushavegods.Butthepersonificationofgravity,forexample,isanAuditoror,ratherAuditors.Inuniversesthatrunonnarrativiumratherthanautomatic,theyarethemeansbywhichthemostbasicthingshappen.

Auditorsarenotonlyunimaginative,theyfinditimpossibletoimaginewhatimaginationis.

Theyareneverfoundingroupsoflessthanthree,atleastforlong.Inonesandtwostheyquicklydeveloppersonalitytraitsthatmakethemdifferent,whichtothemisfatal.ForanAuditortohaveanopinionthatdiffersfromthatofitscoleaguesiscertain...cessation.ButwhileindividualAuditorscannotholdanopinion(becausethatwouldmakethemindividual),Auditorsasawholecertainlycan,andwithgrimcertaintytheyholdthatthemultiversewouldbealotbetteroffwithnolifeinit.Lifegetsintheway,tendstobemessy,actsunpredictablyandreversesentropy.

Life,theybelieve,isanunwantedby-product.Themultiversewouldbemore

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reliableiftherewasn'tany.Unfortunately,therearerules.Gravityisnotalowedtoincreaseamilionfoldandlaminateallocallifeformstothebedrock,highlydesirablethoughthatwouldappeartobe.Simplymugginglifeformsmerelywalking,flying,swimmingoroozingpastwouldattractattentionfromhigherauthority,whichAuditorsdread.

Theyareweak,notverycleverandalwaysafraid.Buttheycanbesubtle.

Andthewonderfulthingaboutinteligentlife,theyhavediscovered,isthatwithsomecareitcanbepersuadedtodestroyitself.

SIXTEEN

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MANIFESTDESTINY

THEWIZARDSAREDISCOVERINGTHATchanginghistoryisnotsoeasy,evenwhenyou'vegotatimemachine.TheAuditorsaren'thelping,buthistoryhasitsownmetaphoricalAuditor,oftencaled`historicalinertia'.

Inertiaistheinnatetendencyofmovingobjectstocontinuemovingalongmuchthesametrack,evenifyoutrytodivertthem;itisaconsequenceofNewton'slawsofmotion.Historicalinertiahasasimilareffectbutadifferentcause:changingasinglehistoricalevent,howeverimportantitmayappear,mayhavenosignificanteffectonthesocialcontextthatdirectsthepathofhistory.

Imaginewe'vegotatimemachine,andgobacktothepast.Nottoofar,justtotheassassinationofAbrahamLincoln.Inourhistory,thePresidentlivedtilthefolowingmorning,soatinydeflectionoftheassassin'sbuletcouldmakealthedifference.Sowearrangeasmaldeflection,andheishitbutrecovers,withnonoticeablebraindamage.Hecutsacoupleofappointmentswhileherecuperates,andthenhegoesontodo...what?

Wedon'tknowanythingaboutthatnewversionofhistory.

Ordowe?Ofcoursewedo.Hedoesn'tturnintoahippopotamus,forastart,oraFordModelTOrdisappear.HegoesonbeingPresidentAbrahamLincoln,hedgedinbyalthepoliticalexpedienciesandimpossibilitiesthatexistedinourversionofhistoryandstilexistinhis.

Thecounterfactual[1]scenarioofaliveLincolnraisesmanyquestions.

HowmuchdoyouthinkbeingtheAmericanPresidentislikedrivingacar,goingwhereyouwantto?Orsittinginatrain,observingtheterrainthatothersdriveyouthrough?

Somewhereinbetween,nodoubt.

Ordinarily,wedon'thavetothinkmuchaboutcounterfactuals,preciselybecausetheyarecontrarytofact.Butmathematiciansthinkaboutthemalthetime-'ifwhatIthinkhappensiswrong,whatcanIdeducethatmightproveitwrong?'Anyconsiderationofphasespacesautomaticalygetstangledupinworldsofif.

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Youdon'trealyunderstandhistoryunlessyoucantakeastabatwhatmighthavehappenedifsomemajorhistoricaleventhadnotoccurred.That'sagoodwaytoappreciatethesignificanceofthatevent,forastart.

Inthatspirit,let'sthinkaboutthataltered`now':thebeginningoftheWest'sthirdmilenniumofhistory,butwithoutLincolnhavingbeenassassinatedinitspast.Whatwouldyourmorningnewspaperbecaled?Woulditbedifferent?Wouldyoustilbehavingmuchthesamebreakfastritual,baconandeggsandasausageperhaps?WhatabouttheWorldWars?

Hiroshima?

Averylargenumberofstorieshavebeenwrittenwiththiskindoftheme:WilsonTucker'sTheLincolnHuntersissetinsuchan'alternat(iv)euniverse'andtacklestheLincolnquestion.

Curiousthingshappeninourmindswhentheyarepresentedwithanyfictionalworld.ConsiderforamomenttheLondonofthelatenineteenthcentury.ItdidhaveJacktheRipper,andwecanwonderaboutthereal-worldpuzzleofwhohewas.IthadDarwin,HuxleyandWalace,too.ButitdidnothaveSherlockHolmes,Dracula,NicholasNickleby,orMrPoly.

Nevertheless,someofthebest

[1]Counterfactual:amoreacceptablewordforwhathasforalongtimebeenaverycommonfeatureofsciencefiction,the'alternateworld'or'worldsofifstory(therewasapulpSFmagazineinthe1950scaledWorldsofIf,infact).'Counterfactual'isnowusedwhensaidstoriesarewrittenbyrealwritersandhistorians,tosavethemtheindignityofsharingagenrewithalthosestrangesci-fipeople.

portrayalsoftheVictorianworldarecentredaroundthosecharacters.

Sometimesthefictionalportrayalsareintendedtopaintahumorousglossonthesocietyoftheperiod.TheFlintstonesputjustsuchaglossonhumanprehistory,somuchsothatinordertothinkrationalyaboutourevolutionwemustexcisealthoseimages,whichisprobablyanimpossibletask.

SherlockHolmesandMrPolywereVictoriansinjustthesamesensethatthetyrannosaurandtriceratopsinJurassicParkweredinosaurs.Whenweenvisage

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Triceratops,wecannotavoidthememoryofthatwartypurple-spottedJurassicParkskin,asthebeastliesonitsside,breathingstertorously.AndTyrannosaur,inourmind'seye,isrunningafterthejeep,bobbingitsheadlikeabird.Whenweenvisagelatenineteenth-centuryBakerStreetit'sverydifficultnottoseeHolmesandWatson(probablyinoneoftheirfilmicversions)hailingafour-wheeler,offtosolveanothercrime.Ourpicturesofthepastareamixtureofrealhistoricalfiguresandscenariospeopledbyfictionalentities,andit'sdifficulttokeepthemapart,especialyasfilmsandTVseriesacquirebettertechnologiestolatchintothosespuriouspicturesinourheads.

The1930sphilosopherGeorgeHerbertMeadmademuchoftheratherobviouspointthatthepresent,inacausalworld,doesnotonlydetermine(`constrain'ifyouprefer)thefuture,italsoaffectsthepast,injustthissense:ifIdiscoveranewfactaboutthepresent,thenthe(conceptual)pastthatleduptothenewpresentmustalsohavebeendifferent.MeadtherebyenabledarathercutewayofseeinghowgoodtheportrayalsofSherlockHolmes,oroftheJurassicParktyrannosaur,are.Ifmypictureofthepresentisn'talteredatalbythepresenceorabsenceofSherlockHolmesinthe1880s,orifmyconstructionofthepresentbyevolutionaryprocessesisn'talteredatalbyseeingJurassicPark,thentheseareconsistentinventions.

DraculaandtheFlintstonesareinconsistentinventions:iftheyrealyexistedinourpast;thenthepresentisn'twhatwethinkitis.Muchofthefunof`worldsofif'stories,andofmanyconsistentfictionslikeTheThreeMusketeers,isthattheyshowclosed-loopcausalitiesinourapparentpast.

WhetherornotD'ArtagnanhadaggregatedtheMusketeersandtherebybroughtintobeingmuchofthecausalhistoryofseventeenth-centuryFrance,childrenoflatercenturieswouldlearnthesamehistoryinthetextbooks.Ultimately,consistenthistoricalfictionsmakenodifference.

InTheScienceofDiscworldIweplayedwiththisideainseveralways:the,presenceoftheElveswas,surprisingly,consistentwithourhistory;stoppingthemledtostagnationofhumansandhadtobereversed.InthisbookthemeddlingoftheUnseenUniversitywizards,inVictorianhistorythistime,istryingtocreateanapparentlyinternalycausedhistoryinwhichDarwinwroteTheOriginofSpeciesandnotTheologyofSpecies.Wearegoingtousethistricktoiluminatethecausalitiesofhumanhistory.

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Inordertodothisconvincingly,wemustmaketheDiscworldintrusionsconsistent,buteventhenwemustaddresstheconvergence/divergenceproblem,whichisthis.Wouldsuchameddled-withworldconvergeontoours,demonstratingthathistoryisstable,orwouldanytinydifferencestartadivergencethatbecamewiderandwider,provinghistorytobeunstable?

Mostpeoplethinkthelatter.Indeed,eventhewildlyimaginativephysicistswhobelievethatanewworldhistoryiscreatedbyeachandeverydecisioninthisuniverse,spawningnewuniversesinwhichtheotherchoiceswereimplemented,don'timaginethatthehistoriesconverge.No,eachuniversegoesitsownway,spittingoutnewanddivergentuniversesasitgoes.TheTrousersofTimeareatree:theirlegscanbranchbutnevermerge.

TheWorldsofIfstoriesweredividedonthisissue.Somehadeachtinychangeinthepastgettingamplified,resultinginvastchangesnow:we'vementionedBradbury'sstorywhereyoutrodonabutterflyinthefarpast,onadinosaurhunt,andcamebacktofindafascistregime.Orthechangesyoumadewerealwipedout,becausetherewasagigantical-powerfulinertia-of-eventsKismetthatyoucouldn'tchange.Howeveryoutriedtoavoidyourfate,thatonlymadeitmorecertaintohappen.Andsomestoriestookamiddleway;somethingsconvergedandothersdidn't.

This,wethink,istherationalwaytothinkabouttimetravelandalteringthepast.

Afteral,wedon'tchangetherulesbywhichthepastworks.Gravitystiloperates,sodiumchloridecrystalsarestilcubical,peoplefalinandoutoflove,misershoardandspendthriftssquander.Whatwechangeiswhatphysicistscaltheìnitialconditions'.WechangethepositionsofafewofthepiecesontheGreatChessboardofLife,TheUniverseandEverything,butwestilkeeptotherulesofchess.That'showthewizardsoperatedinTheScienceofDiscworldI.TheywentbackintimetoremovetheElvesfromthegameboard;thentheywentbackagaintostopthemselvesmakingthatmistake.

Wearenowreadytothinkaboutourquestionabove:wouldthenamesofnewspapershavechangedifAbrahamLincolnhadlivedtoaripeoldage?

Perhapssomeofthemwould,becausesomecultureswouldhavebecomeratherdifferent.PerhapsQuebecwouldn'thavebeenFrench;perhapsNewYorkwould

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havebeenDutch.ButnameslikeDailyMail,DailyNewsandNewYorkTimesaresoobvious,soappropriate,thateveniftheRomanEmpirewerestilrunningthings,theLatinequivalentswouldseemfitting.

Someonewouldhaveinventedflushtoilets,andtherewouldhavebeenasteamenginetime,whenseveralpeopleinventedsteampower.SomethingsinWesterncultureseemsolikely,fromtoiletpaperonupto(assoonaspaperisinvented)dailynewspaperstoplasticstoartificialwood...Technologyseemstohaveasetofrulesforitsadvancement,sothatitseemsrationaltoexpectgramophonesofsomekindifpeoplemakemusicwithmusicalinstruments,thentapeplayerswhenpeoplegetusedtoelectricityanditspossibilitiesforamplification.Thenfromanaloguetodigital,tocomputers...somethingsseeminevitable.

Perhapsthisfeelingismisleading,butit'ssilytoinsistthatabsolutelyeverythinginaslightlydivergentfuturehastoendupdifferent.

Organicevolutionhaslessonsforushere,andtheselessonscaninstructusabouthowlikelyvariousadvancesinanimalorganisationwere.

Innovationslikeinsectwings,vertebratejaws,photosynthesis,lifecomingoutfromtheseasontotheland...ifweranevolutiononEarthagain,wouldthesamethingshappen?Ifwewentbacktothebeginningoflifeonthisplanet,andkiledit,wouldanothersystemevolveandgiveusawholedifferentrangeofcreatures,orwouldEarthremainlifeless?Orwouldwebeunabletodecidewhetherwe'ddoneanything,becauseeverythingwouldbejustthesamethesecondtimearound?

Ifhistory`healedup',wewouldn'tbeabletotelifitwasthesecond,orthehundredth,orthemilionthtimearound-eachtimesoonerorlaterproducingaversionofus,whosetimemachinegoesbacktoTheOrigin.

Therewouldbeaconsistenttimeloop,ashappenedwiththeElvesinTheScienceofDiscworldI.Iflifeisèasy'tooriginate(andtheevidencedoeslookthatway)thenthisisn'tanexerciseingoingbackandkilingyourgrandfather,orifitis,yourgrandfatherisavampireanddoesn'tremainkiled.Iflifeiseasytoinvent,thenpreventingithappeningonce,oramiliontimes,wilmakenodifferenceinthelongrun.Thesameprocessthatgenerateditwilhappenagain.

Lookingatthepanoramaoflifeonthisplanet,intimeaswelasspace,wecanseethattherearetwokindsofevolutionaryinnovation.Photosynthesis,flight,

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fur,sex,andjointedlimbshavealarisenindependentlyinseveraldifferentlineages.Surely,liketoiletpaper,wewouldexpecttoseethemagaineachtimeweranlifeonEarth.

And,presumably,we'lseethemonotheraqueousplanetswhenweexploreourlocalregionofthegalaxy.Suchevolutionaryattractorsarecaledùniversals',incontrastto'parochials':unlikelyinnovationsthathavehappenedonlyonceinEarth'shistory.

Theclassicparochialisthecurioussuiteofcharacterspossessedbylandvertebrates,becauseaparticularspeciesofDevonianfishsucceededininvadingthelandinour,real,history.Thosefishes'descendantswereamphibians,reptiles,birds,andmammals-includingus.Jointedlimbsareauniversalinnovation.Thelimbsofspiders,hydraulicalyoperated,differindetailfromthelimbsofmammals,andwerepresumablyacquiredviaadifferentancestor,perhapsanearlierarthropodproto-spider.Themammalianinternalskeleton,withoneboneatthebodyend,thentwo,thenawristorankle,thenfivelinesofbonesforfingersortoes,wasanindependentevolutionofthesameuniversaltrick.

Thishighlyunlikelycombinationnowoccursinallandvertebrates(exceptmostoftheleglessones),becausetheyarealdescendedfromthosefishesthatcameoutofthewatertocolonisetheland.Otherparochialsarefeathersandteeth(ofthekindthatevolvedfromscales,whicharewhatwehave).And,especialy,eachofthespecialbody-plansthatcharacteriseEarth'sanimalsandplants:mammal,insect,rotifer,trilobite,squid,conifer,orchid...NoneofthesewouldappearagainafterarerunofEarth'sevolutionaryhistory,norwouldwefindexactreplicasonotheraqueousplanets.

Wewouldexpectmuchthesameprocessestooccur,though,inarepeatrunofEarthoronanothersimilarworld:anatmospherefarfromchemicalequilibriumaslifeformspumpuptheirchemistryusinglight;planktoniclayersoftheseascolonisedbythelarvaeofsedentaryanimals;flyingcreaturesofmanykinds.Suchecosystemswouldalsoprobablyhave`layers',ahierarchicalstructure,fundamentalysimilartotheecosystemsthathaveemergedinsomanydifferentcircumstancesonEarth.Sotherewouldbe'plantlike'creatures,aproductivemajorityofthebiomass(likeEarth'sgrassor

marinealgae).Thesewouldbebrowsedbytinyanimals(mites,grasshoppers)andbylargeranimals(rabbits,antelopes),withafewverylargecreatures

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(elephants,whales).Comparableevolutionaryhistorieswouldleadtothesamedramaticscenarios,butperformedbydifferentactors.

Thecentrallessonisthatalthoughnaturalselectionhasaveryvariedbasetoworkwith(recombinationsofancientmutations,differentlyassortedinalthosèwaste'progeny),clearlarge-scalethemesemerge.Marinepredators,suchassharks,dolphins,andichthyosaursalhavemuchthesameshapeasbarracuda,becausehydrodynamicefficiencydictatesthatstreamliningwilcatchyoumoreprey,morecheaply.Verydifferentlineagesofplanktoniclarvaealhavelongspinesorotherextensionsofthebodytorestrainthetendencytofalorrisebecausetheirdensitydiffersfromthatofseawater,andmostofthempumpionsinorouttoadjusttheirdensitiestoo.Assoonascreaturesacquirebloodsystems,othercreatures-leeches,fleas,mosquitoes-developpuncturetoolstoexploitthem,andtinyparasitesexploitboththebloodasfoodandthebloodsuckersaspostalsystems.Examplesaremalaria,sleeping-sickness,andleishmaniasisinhumans,andlotsofotherparasiticdiseasesinreptiles,fishes,andoctopuses.

Large-scalethemesmaybetheobviouslesson,butthelastexamplesrevealamoreimportantone:organismsmostlyformtheirownenvironments,andnearlyaloftheimportantcontextfororganismsisotherorganisms.

Humansocialhistoryislikeevolutionaryhistory.Weliketoorganiseitintostories,butthat'snothowitrealyworks.History,too,canbeconvergentordivergent.Itseemsquitesensibletobelievethatsmalchangesmostlygetsmearedout,orlostinthenoise,sothatbigchangesareneededtodivertthecourseofhistory.Butanyonefamiliarwithchaostheorywilalsoexpectsometinydifferencestosetoffdivergenthistories,driftingprogressivelyfurtherawayfromwhatmighthavehappenedotherwise.

Changinghistoryisathemeoftimetravelstories,andthetwoissuescometogetherinthosestoriescaled`worldsofif.

Wehavethestrongestfeelingthatwhatwedo,evenwhatwedecide,doeschangehistory.IfIdecide,now,nottogoandmeetAuntieJanieatthetrainstationeventhoughshe'sexpectingmebecauseItoldherIwould...theuniversewiltakeadifferentpathfromtheoneitwouldhavetakenifIhaddonetheexpected.Butwe'vejustseenthatevensavingAbrahamLincolnfromtheassassinwouldhavethetiniest,mostlocal,ofeffects.Neighbourssuchasthegas-bagaliensonJupiterwouldn'tnoticeLincoln'ssurvivalatal,oratleastnot

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foraverylongtime.Afteral,wehaven'tyetnoticedthem.[1]

Infact,howwilthey,orwe,notice?Howwilwebeabletosay,`Justaminute,thisnewspapershouldn'tbecaledtheDailyEcho...Theremusthavebeenatimetravelerinterfering,sothatwe'renowinthewronglegoftheTrousersofTime'?

AuntieJaniemakingherownwayfromthestationwon'ttoppleempires-

unlessyoubelieve,withFrancisThompson'sTheMistressofVision,thatAlthingsbyimmortalpowerNearorfarHiddenly

Toeachotherlinkedare

ThatthoucanstnotstiraflowerWithouttroublingofastar.

Thatis,alcontingentchaosbutterfliesareresponsibleinsomesenseforalimportanteventslikehurricanesandtyphoons-and[1]Wel,theremightbe...

newspapertitles.Whenatyphoon,oranewspapertycoon,topplesanempire,thateventiscausedbyeverything,althosebutterflies,thatprecededit.Becausechangeinanyone-orperhapsjustinoneofaverylargenumber-canderailtheimportantevent.

Soeverythingmustbecausedbyeverythingbeforeit,notjustbyathinstringofcausality.

Wethinkaboutcausalityasathinstring,alinearchainofevents,linkfolowinglinkfolowinglink...probablybecausethat'stheonlywaywecanholdanykindofcausalsequenceinourminds.Aswe'lsee,that'showwedealwithourownmemoriesandintentions,butnoneofthismeansthattheuniversecanisolatesuchacausalstringantecedenttoanyeventatal,importantornot.Andsurely'important'or`trivial'isusualyhumanjudgement,unlesstheuniverserealydoes`smearout'mostsmalchanges(whateverthatmeans),andmajoreventsarethosewhosesingularinfluencecanbedistinguishedatlatertimes.

Becausetheyarestories,committedtothewayourmindsworkandnottothewaytheuniverseworksitsowncausality,mosttimetravelstoriesassumethatabig(localised)changeisneededtohaveabigeffect-kilNapoleon,invadeChina...orsaveLincoln.Andtimetravelstorieshaveanotherconvention,

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another`conceit',becausetheyarestories,nearerfee-fi-fo-fumthanphysics.Thisistherememberedtimelineofthetraveler.

Usualytheplotdependsonitbeinguniquetohim.Whenhecomesbacktohispresentherememberssteppingonthebutterfly,orkilinghisgrandfather,ortelingLeonardoaboutsubmarines...butnooneelseisconsciousofanythingotherthantheiràltered'present.

Let'smovefromlargeevents,largeorsmalcauses,tohowweinfluencetheapparentcausalityinourownlives.Wehaveinventedaverystrangeoxymorontodescribethis:`freewil'.Thesewordsappearprominentlyonthelabelofthecanofwormscaled`determinism'.InFigmentsofRealitywetitledthefreewilchapter:`Wewantedtohaveachapteronfreewil,butwedecidednotto,sohereitis'inordertoexposetheparadoxicalnatureofthewholeidea.Dennett'srecentbookFreedomEvolvesisaverypowerfultreatmentofthesametopic.Heshowsthatinregardtòfreewil'

itdoesn'tmatterwhethertheuniverse,includinghumans,isdeterministic.

Evenifwecandoonlywhatwemust,therearewaystomaketheinevitableevitable.Evenifitisalbutterflies,iftinydifferenceschaoticalydeterminelargehistoricaltrends,neverthelesscreaturesasevolvedasuscanhavètheonlyfreewilworthhaving',accordingtoDennett.Hewritesofdodgingabasebalcomingforhisface,andthisbeingperhapsaculminationofacausalchaingoingrightbacktotheBigBang-yetifitwilhelphisteam,hemightletithithisface.

Butthen,whatdecidesitis:wilithelphisteam?That'snotafreechoice.

Inevitable,evitable.

Dennett'sbestexampleismoreancient:Odysseus'sshipapproachingtheSirens.Inevitably,ifhismenheartheSirens'song,theywilsteertheshipontotherocks.Butthesteersmanmustbeabletohearthesurf,sothereseemsnowaytoavoidtheirlure.Odysseushashimselflashedtothemast,whilealhissailorsplugtheirearswithwaxsotheycannotheartheSirens.ThevitalissueforDennettisthathumans,andonthisplanetprobablyonlyhumans,haveevolvedseveralstagesbeyondtheobserving-and-reactingthatevenquiteadvancedanimalsdo.Weobservedourselvesandothersobserving,sogotmorecontexttoembedourbehaviourin-includingourprospectivebehaviour.Thenwedevelopedatacticoflabelinggoodandbadimaginaryoutcomes,justaswe

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labeledourmemorieswithemotionaltags.We,andsomeotherapes-perhapsalsodolphins,perhapsevensomeparrots-developedàtheoryofmind',awaytoimagineourselvesorothersininventedscenariosandtoanticipatetheassociatedfeelingsandresponses.Thenwelearnedtorunmore

thanonescenario:`Butontheotherhand,ifwedidso-and-so,thelioncouldn'tgetusanyway...',andthattricksoonbecameamajorpartofoursurvivalstrategy.SowithOdysseus...andfiction...andparticularlythatdissectionofhypotheticalalternativesthatwecalatimetravelstory.

Inourminds,wecanholdmanypossiblehistories,justasMeadshowedthateverydiscoveryabouttodayimpliesadifferentpastleadinguptoit.

Butwhetherthereisanysenseinwhichtheuniversehasseveralpossiblepasts(orfutures)isamuchmoredifficultquestion.We'vearguedthatpopularisationsofquantumindeterminacy,particularlythemany-worldsmodel,havegotconfusedaboutthis.Theytelusthattheuniversebranchesateverydecisionpoint,whereaswethinkthatpeoplehavetoinventadifferentmentalcausalpath,adifferentexplanatoryhistory,foreachpossiblepresentorfuture.

AntonioDamasiohaswrittenthreebooks:LookingforSpinoza,Descartes'Error,andTheFeelingofWhatHappens.Thesearepopularaccountsofwhatweknowabouttheimportantattributesofourminds.Hehasdocumentedourdiscoveries,nowthatwecanusevariousexperimentaltechniquestòwatchthebrainthinking'andseehowthedifferentpartsofthebrainareinvolvedinwhatwefeelaboutthethingswethink.Wetendtoforgetthatourbrainsarecontinualyinteractingwithourbodies,whichsupplythebrainwithstance-determininghormonesforlonger-termbehaviour,andmoodchangingemotion-provokingchemicalsforshort-termmodulationofourintentionsandfeelings,directingourthoughts.

Accordingtothesebooks,theresultofhavinglivedwithabrainwhichwethinkwedirectusingakindoftiler,butwhichactualyiscontinualyaffectedbycross-winds,occasionalstorms,rainandwarmsunthatprovokesusintolazydays,isthatwehaveevolvedaseriesofmemorieswithdifferentflavours.Or,theresultofhavinglivedwithabrainthatwethinkwedirectusingakindofautomobilesteeringwheelandfootcontrols,butwhoserouteisactualycontinualyaffectedbylong-termgoalsthatchange(`Let'sgotoahotel,nottoAuntieJanie'sagain'),short-termroadsignsandothertraffic,isthatwehave

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evolvedaseriesofmemorieswithdifferentflavours.Or,eachofushasapersonalhistorywhichweexplaininternalybyfeelingsattachedtoemotionalmemories,sowehaveevolvedaseriesofmemorieswithdifferentflavours.

Damasiohasimportedemotionalbiasingintohowwethinkaboutourownintentions,choices,otherpeople,memories,andprospectiveplans.Heclaimsthatthisiswhatemotionis`for',andmostpsychologistsnowagreethatemotionalylabeledmemoriesaretheeffectofhavingabrainwhoseinteractionwithitsbodypaintsemotionsontomemoriesandintentions.

Wehabitualyassumethatrealphysicalhistory,andparticularlysocialhistory,worksthesamewayasourownpersonalhistories,witheventslabeled`good'or`bad'...butitdoesn't.It'smisleadingtothinkoftheBigBang,forexample,asanexplosionlikeabomborafirework,seenfromoutside.ThewholepointoftheBigBangmetaphoristhatatthemomenttheuniversewasbom,therewasnooutside.Moresubtly,perhaps,wetendtothinkofthebirthoftheuniverseinthesamewaythatwethinkofourownbirth,orevenourconception.

Realhistory,postwhatevertheBigBang`realy'was,reliesontheaccumulationofcountlesstinysequencesofcause-and-effect.Assoonaswebegintothinkaboutwhatanyofthesesequenceslookslike,takingitoutofthecontextthatdrivesit,weloseitscausality.Thisseethingseaofprocessesandappearancesanddisappearances,wherenocausalitycanbeisolated,issometimescaledÀntCountry'.Thenamereflectsthreefeatures:theseething,apparentlypurposelessactivityofants,which,inaggregate,makesantcolonieswork;themetaphoricalAuntHilaryinDouglasHofstadter'sGodel,Fscber,Bach,whowasasentientanthilandrecognisedtheapproachofherfriendtheanteaterbecausesomeofherconstituentantspanicked;andLangton'sAnt,asimplecelularautomaton,whichshowsthatevenifweknowaltherulesthatgovernasystem,itsbehaviourcannotbepredictedexceptbyrunningtherulesandseeingwhathappens.Whichinmostpeople'sbookisnot`prediction'atal.

Forsimilarreasons,itisimpossibletoforecasttheweatheraccurately,evenafewweeksahead.Yet,despitethisapparentabsenceofcausalityatthemicro-levelsofweather,theimpossibilityofisolatingcausalityintheswirlingbutterflies...despitethechaoticnatureofmeteorologyinboththelargeandthesmal,weathermakessense.Sodoesastonetumblingdownhil.Sodoesalotofphysics,engineering,andaeronautics:wecanbuildaBoeing747thatfliesreliably.Nevertheless,alofourphysicalmodelsarerootedinbrainsthatget

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mostoftheirperceptionswrong.

Shoutingatthemonkeysinthenexttree.That'swhatbrainsevolvedtodo.

Notmathematicsandphysics.

Wegetecologyandevolutionmostlyright,butoftenwrong,forthesamereasons.Thescenarioswebuilddon'twork,they'reasfalsetofactas`weather'.Butwecan'thelpbuildingthem,andthey'reusefulsufficientlyoftentobègoodenoughforgovernmentwork'.

Tounderlinethispoint,here'sanimportantevolutionaryexample.Thinkofthefirstlandvertebrate,thatfishthatcameoutofthewater.WehavethestrongestfeelingthatifwetookatimemachinebacktotheDevonian,whenthatfirstimportantfishwasemergingfromthesea,thereoughttobeamomentthatwecouldisolate:`Look,bywrigglingoutontothemudthatfemalehasescapedthatpredator,soshe'slivedtolayhereggs,andsomeofthemwilbecomeourancestors...Ifshehadn'tgotthoseleggyfins,shewouldn'tquitehavemadeit,andwewouldn'tbehere.'

Grandfatherparadoxagain?Notquite,butwecaniluminatethegrandfatherparadoxneatlywiththisexample.Askyourselfwhatwouldhappenifyoukiledthatfish.Wouldhumanityneverhavehappened?Notatal.Byisolatingasingleevent,wehavetriedmentalytomakehistoryfolowathinthreadofcausality.ButwemadetheAdam-and-Evemistake:ancestorsdon'tgetfewerasyougoback,theymultiply.Youhavetwoparents,fourgrandparents,maybeonlysevengreat-grandparents,becausecousinmarriageswerecommonerthen.Bythetimeyou'vegonebackacoupleofdozengenerations,asignificantproportionofalthebreedersofthatperiodwereyourancestors.That'swhyeveryonefindssomefamousancestorswhentheylook-andthefactthatfamouspeoplewererichandpowerfulandsexualysuccessfulhelpstoo,sothattheyarereproductivelybetterrepresentedinthatgeneration'sdescendants.

Notethatwesaid`breeders'and`many'.Nearlyalsexualyproducedcreaturesdon'tbreed,includinghumansofmostpreviousgenerations.Notonlyaremostofthepeoplealiveatthatpreviousgenerationyoungchildrenwhowon'tsurvivetobreed;manyoftheapparentlysuccessfulbreederscontributetolineagesthatdieoutbeforetheygettothepresentday,becausetheyareexcludedfromthelimitedecosystembymoresuccessfullineagesasthegenerationspass.

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SowhenwelookatthoseDevonianfishes,theresimplyisn'tjustonethatwasourancestor.Alofthebreeders,averyunsystematicsmalproportionofthefishpopulation,contributedtotherecombiningandmutatingmixofgenesthatpasseddownfromthosefishesthatleftthewater,throughgenerationsofamphibiansandmammalikereptiles,intotheearlymammals,werenewlyselectedtocharacterisetheearlyprimates,andeventualyendedupinus.Therewasn'tasinglegrandfatherfish,oronegrandfatherprimate,nothinlineofdescent,justasthereisn'tathinlineofcausalityleadingfromabutterfly'swingflaptoahurricane.Nearlyanyfishyouwentbackandkiledwouldmakevirtualynodifferencetohistory.We'dstilbehere,buthistorywouldhavetakenaslightlydifferentroutetogettous.

Butthatdoesn'tmeanthathistoryhasnoimportantaccomplishments.

Somephysicists,especialy,havearguedfromthisindeterminacyandchaoticinfluencesatalthemicro-levelsthatthereisnopatterntohistory,thatHeisenberguncertaintyrules.Wrong.Justbecausewecannotpredicttheweathermorethanaboutaweekahead,withthebestandbiggestcomputers,doesn'tmeanthatthereisn'tsuchathingasweather.Ourthin-causal-threadevolutionaryscenariosfortheemergenceofthosefishesontothelanddon'twork,butthatdoesn'tmeanwemustthrowawayalideasofcausalityinevolution.Anyevent,whenlookedatindetail,seemsnottohaveaclearcause,butthatjustmeansthatourDamasio-mindsarenotsuitedtothatwayofanalysinghistory.

Wearemuchbetterattotalydisregardingalthemicrostuff,andmakingbigguesses:Iguessit'lbesunnyagaintomorrow;orIguessthatamongalthosefisheseatingeachotherontheDevonianmudflats,somewilescapeontotheland.We'reconfirmedinthatguessbyfindingclimbingperch,mudskippersandlotsofotherseparatefishlineagesdoingexactlythatonmudflatstoday.

ThegreatevolutionarybiologistStephenJayGouldgotthispointwronginWonderfulLife:ifevolutionranagain,hestated,wewouldnotgetpeople,becauseofalthetinychaoticbutterfliesthatdeterminedevolutionaryoutcomes,sotherewerenothincausalthreads.Wedisagree:wemightnot,almostsurelywouldnot,getthesameprimatecomingdownfromthetrees,butequivalentmajorinnovationswouldoccurinthenewanddifferentlineages.Peoplearegoodatfindinghigh-levelgroupings,makinganalogiesandmetaphors,arguingfromwhatAuntJaniedoestodaytowhatshe'ldotomorrow,ordidtwentyyearsago.Butweoversimplifywhenwetrytodisentanglethemazeoftinycausalities

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thatliesbehindanyhistoricalevent,becausewecan'thandlethatkindofcomplexity.

So,eventhoughalofthecausalityhappensatthemicro-level,andwecan'tanalyseitexceptintermsoftensofparticlesinteractingwhenit'srealybilions,thisisn'twhatit'sabout.It'sliketheearlytwentieth-centuryphysiciststelingusthatthedining-roomtablewasn'trealythere,itwasnearlyalemptyspace,andthatconceptslikèhard'and`brown'hadnoplaceinthephysicist'sviewoftheworld.Somuchtheworseforthephysicist.Didherealynoteathisdinneroffjustsuchahard,browntable?

Andwasnothisbraindesignedtodorealycleverthingswithabstractionsusefulinhisdailylife,likehardandbrown,ratherthantheverypeculiarlyunusefulconceptsofatoms,nuclei,andsoon?

Onthecontrary,ourbrainsareexcelentatalthehigher-leveljudgementsthey'recaledontomake,especialyinaworldthatisfulofhard,browntables,doors,houses,treestomakethemoutof,andotherpeopletohelpusorcompetewithus.Butnearlyalhumanbrainsarepoorwhenitcomestothephysicsofatomsandthemicro-world.

Backtohistory.Wèmakesense'oflargemovementsliketheEnlightenment,democracyinancientAthens,theTudors;butweknowthatifweweretolookatalthesmal-scaleinteractions,theywouldmakelittlesenseagainstthecomprehensiblebackdrop.Thatispreciselywhyhistoricalnovelscanbesofascinating,andwhyTheThreeMusketeersdidn'trealyaffectCardinalRichelieuandaltheimportantpeopleinseventeenth-centuryFrance.Nevertheless,wegreatlyenjoythefictionthatmakessenseofthegreatmovementsbytyingthemdowntothemotivesandnobilityofafewpeoplelikeD'Artagnan,withwhomwecanidentify.

ThesequelsTenYearsAfterandTwentyYearsLaterintriguedsomeofus,asDumasfoundthathewasontoagoodthingandturnedoutmoreofthesame.Someofus,atleast,thenfoundthatAthos'snobilityrangincreasinglyfalse,andPorthos'sgoodhumourwasboring,whileAramis'sreligiosityworeverythinastheyearsrushedby.Theinitialideawedgedintothehistoryweknew,itwasconsistentandprovidedcolourfulincident.Butthelatermoney-spinnerswereincreasinglyatoddswithhowweknewhistoryworked.

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Thereisanexcelentexampleoftheconverseofthis,whichmakesthatpointevenbetterthanDumas.Wels'sTheTimeMachine,aswe'vesaid,wastheabsoluteclassictimetravelogue,showingusthelargepicturefromprehistorytothesocialconsequencesofthecapitalismthatthesocialistWelswantedtocriticise.ThenthecoolingSun,thegreatcrabsonapost-diluvianbeach...lovely.ButStephenBaxter'smodernsequelTheTimeShipsshowsushowclevertheMorlockswilbe,howtheTravelerisrealyalittlebitprurientaboutthelittlegirlfromthefuture-aresonancewithLewisCarrol'sAlice-whoisinnocentandabitstupid.

It'slikeahistoricalnovelthatputsalthelittlesexyanddespicablebitsintothegreattapestryofhistory.Suchliteraryexercisesaddcolourandflavourtohistory,justasDamasiohasshownthatwedowithourownpersonalmemories.Thepleasurethisexercisegivesusshowshowourhumanmindsreadhistory:inthelargewithoutflavour,inthesmalwiththekindofcolourthatwepaintontoourownsmalreminiscences.Sohistoricalromanceisjustthat:romanticpaintingofthelittle,interestingitems,whosecausalitymightaffectthebigpicture,butdoesn't.

Whatdoesitmean,then,toaskwhethertimeknitsupanychanges,orwhethermischievousbutterfliesareultimatelyresponsibleforthefalofempires?

Herefictionalconventionsceasetofittherealworld.Fromthepointofviewofthewizards,Roundworldtimeisaonedimensionalsequencethattheycanaccesstwodimensionalylikeabook.Fornarrativereasons,wehavetodepictitlikethisbecauseofalthosethin-thread-of-causalityhistoricalstoriesthatourmindsfindsocongenial.Inafictionalcontext,wehavelittlechoice.However,herewewanttothinkaboutthenatureofcausalityandfreewilinthèreal'universe,which-aswe'vemadeclearthroughouttheScienceofDiscworldseries-doesnothaveanynarrativium.Inthatcontext,wehavetounderstandthatthissimpleimageofRoundworldhistoryisafraud.TheTrousersofTimealsoworkwelasastory,butasgenuinephysicstheyareafraud:youcan'tbepushedfromonelegtotheotherbyanevent.Worse,youcan'ttelthattherehasbeensuchanevent.

Asfarasyouareconcerned,thisistheworld.Itdoesn'thaveìfs'initspast.

Noneofthisstopsususing`whatifs'(whichbynaturearefictions,notfacts)tothinkabouthistory.Wecanstilask,inourminds,whatwouldhavehappenedif,say,Lincolnhadsurvived...butintherealworldhedidn't,andwecan'truna

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mock-upofìfhedid'intherealworld:onlyinourheads.

Sciencerunsintopreciselythisdifficulty.Forinstance,themainproblemintestingmedicaltreatmentsisthatwecan'tbothgiveMrsJonesthetreatmentandnotgiveMrsJonesthetreatment,simultaneously,andcomparetheresults.Wecandoitsequentialy,butthenthesecondtreatment(whetheritisplaceboorrealtreatment)isofadifferentMrsJones,onewho'shadthefirsttreatment.Sowhatthetestersdoistohavequitealargepanel,dotreatmentfirstonsome,placebofirstonothers-

andtheyshouldperhapsdotwoplacebosonafew,andtwotreatmentsonafewothers.

Whattimetravelstoriesdo,inourminds,isthesamekindoftest:`WhatwouldhappenifLeonardohadrealyseenasubmarineworking?'orequivalently`DidLeonardoseeasubmarineworking?'InTheScienceofDiscworld,andmoreexplicitlyinTheScienceofDiscworldI,weaskedwhethertheinterestingstoriesthatwemakeuphavesomekindofcoherentexplanation,somethinglikeèvil'-whichwepersonifiedinthesecondbookasElves.Towhatextentdosuchconceptsrelatetotherealrulesoftherealworld?Nowwearguethatwecannotknowifanyanswerwegetisuseful;wecan'tevenknowwhetherwe'vegotanansweratal.

AndthatthisispreciselywhyDennett'skindoffreewilistheonlyoneworthhaving.It'sprospective,givingeachofusthechancetomakelittleitemsofanotherwiseinevitablefutureevitable.

Whenwelookbackonsomethingwe'vechangedbythatkindofanactoffreewil,it'sjustascausalaseverythingelse-andiftheuniverseisinanysensedeterminate,thenitisdeterminateinthatsense.ThinkofOdysseuslookingbackatwhathappenedashisshipfailedtobecaughtbytheSirens.Hismendidn'thearthem,andhe,whocouldhearthem,couldn'tacttosteertheship.Soheandhiscrewcamethroughinthatmostunlikelyofpassages.Thereisasense,ofcourse,inwhicheveryseapassageisequalyunique,justaseverydealofcardsisunique;butOdysseus'sjourney,likeaonesuit-per-playerdealofcards,istotalyremarkabletoo.

Lookingbackintohistory,canwefindjourneys,events,andprocessessoremarkablethattheyseemtobetheresultsofpreviousactsoffreewil?

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What,then,iscausality?ForDamasio-likereasons,wetendtothinkthatwhatgiveshistoryitsdynamicisthebigevents,thèpivotpoints'.Thefalacyisthatwethinkbigcausesareneededtoproducebigeffects.Thisisfalse(butterfly)butthereisaproblem:choosingtherighttinychange(whichbutterfly?).Andtherearealwaysbilionsofnewbutterflies,draggingnewchangesoutfrompreviouslyinvisibledifferencesìnthe13thdecimalplace',unobservableuntiltheireffectsshowup.

Realhistoryislikethis;causesareoftendistributed,withhugenumbersoftinyeventsalcomingtogether.ItisjustthisproblemthatleadsRidculytoemploysuchahugenumberofwizards,doingsuchabizarresetoftrivialthings,merelytogetTheOriginwritten.

Weonlyjustifythissortofcausalityinretrospect:historydidn'tknow`whereitwasgoing'.Sochangingthepastcreatesacontextforthefuture,notacausalchain,andthisishowthewizardsmustoperate,whichiswhywehavethousandsofthemmakingendlesstrivialchangestoVictorianhistory,insteadof,say,assassinatingQueenVictoria.AnyVictorian,perhapsparticularlythewel-trainednursemaid,wiltelyoujustthataboutyourpersonalhistory:yourheartmustbepure(context)ratherthanyourplansbeingsubtle.

SEVENTEEN

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GALAPAGOSENCOUNTER

CHARLESDARWINWASSITTINGONagrassybank.Threetypesofbeebuzzedamongtheflowers,andoverheadexamplesofHirundorusticaswoopedaftermiscelaneousEphemeroptera.

Histhoughtswerecomplex,ashumanthoughtstendtobewhenthemindisidling,butincluded:thisisaninterestingbankofastonishingcomplexity;theremightbefishforlunch;hehadasorethroat;hehopednevertoreceiveanotherletteraboutbarnacles;therashseemedtobegettingworse;therewasastrangebuzzingsound;hadherealyexperiencedthatapparition?;homeopathytranscendedalcommonsense;herealyshouldfindoutwheretheovariaweresituatedinPhylosoma;itrealywasaveryloudbuzzing...

Somethinglikeayelow-brownsmokewasissuingfromaholeinthebankafewyardsaway,andresolveditselfintoacloudofangryVespulavulgaris.ItboredownonthehorrifiedDarwin-

'Overhere,waspies!'

Darwinstared.

ThismissionhadcreatedadifficultdecisionforRincewind,whenhe'dbeenpresentedwiththetaskofpreventingCharlesDarwinbeingstungtodeathbywasps.RightfromthestartitwasobviousthatDarwinwouldsee,him,andifRincewindwasinvisiblethewaspswouldn'tseehim.He'dthereforeundertakenthemissioncarryingtwobucketsofwarmjamandwearingapinktutu,anacid-greenwigandarednose,reasoningthat(a)Darwinwouldn'tbelievethathehadseenhimandinanycase(b)wouldn'tdaretelanyone...

Darwinwatchedtheapparitionskipawayoverthefields.Itwasquiteastonishing.He'dneverseenwaspsswarminsuchamanner.

Apieceofpaperflutteredtotheground.Thecuriousclownmusthavedroppedit.

Darwinpickeditupandread,aloud,"`Returnme,Hex".Whatdoes-?'

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Theafternoondozedon.Thegrassybankwentbacktoitsbuzzing,humming,floweringbusyness.

Ontheforlornshore,amanappeared,hidtwobucketsbehindarock,andremovedhisfalsenose.

Rincewindscannedthelandscapewhileextractinghishatfrominsidehisshirt.

Thiswasoneofthemostfamousislandsinthehistoryoftechnomancy?Itlooked,frankly,ratherdul.

He'dbeenexpectingforestsandstreamsandariotofcreatures.Youcouldn'tmoveforvibrant,strivinglifeonMonoIsland,homeoftheGodofEvolution.Everythingwantedtoleave.Butthisplacehadaskinflintlook.

You'dneedtobetoughtosurvivehere.You'dhavetofitin.

Hecouldn'tseeanygianttortoises,buttherewereacoupleoflarge,emptyshels.

Rincewindpickedupalengthofdriftwood,bakedbythesunintosomethinglikestone,andhurriedupanarrowpath.

Hexwasgood.ThemanRincewindwasafterwasstridingaheadofhimalongthetrack.

`MrLawson,sir!'

Themanturned.

`Yes?AreyoufromtheBeagle?'

`Yessir.Heaveho,sir,'saidRincewind.Lawsonstaredathim.`Whydoyouwearthathatwith"Wizzard"writtenonit?'Rincewindthoughtfast.ThankgoodnessRoundworldhadsome

strangecustoms.

`CrossingtheLineceremony,sir,'hesaid.`Tookafancytoit!'Òh,KingNeptuneandsoforth,'saidLawson,backingawayalittle.Jolygood.HowcanIhelp

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you?'

'Justwantedtoshakeyoubythehandandsayhowgladwealarethatyou'redoingsuchawonderfuljobouthere,sir,'saidRincewind,pumpingtheman'sunresistingarmvigorously.`We...that'sisverykindofyou,Mr-

whatwasthatnoise?'`Sorry?Shivermytimber,bytheway.'

`That...whistlingnoise...'saidLawson,uncertainly.

`Probablyoneofthetortoises?'saidRincewind,helpfuly.

`Theyhissor-wasn'tthatathump?'saidLawson.Behindhim,asmalcloudofdustroseabovethebushes.

`Didn'thearone,yoho,'saidRincewind,stilshakingthehand.`Wel,don'tletmekeepyou,sir.'

Lawsongavehimthelookofamanwhofeelshasinadvertentlyfalenintodribblingcompany.Thehatwasclearlypreyingonhismind.

`Thankyou,myman,'hesaid,pulinghishandaway.Ìndeed,Imustgo.'

Heheadedawayatsomespeed,whichincreasedwhenhenoticedRincewindfolowinghim,andcompletelyfailedtonoticewhatwas,afteral,justanothersmal,rubble-filedholeamongmany.Rincewindspottedit,though,andaftersomeeffortpuledoutasmal,warmlump.

Somethinghissed,behindhim.

Rincewindhadascertainedthattheonlywayagianttortoisecouldgoasfastashimwasbyfalingoveracliff,andalsothattheywerehighlyunlikelytosavageamantodeath.Stil,hewasready.

Heturned,stickupraised.

Something,agreyishsomething,somethingjusttransparentenoughtoshowthelandscapebehinditinadrearylight,washoveringafewfeetaway.Itlookedlikeamonk'srobeforaverysmalmonk,andminusthemonk.Theemptyhoodwasmoreworryingthanalmostanythingthatcouldhavefiledit.Therewereno

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eyes,therewasnoface,buttherewasneverthelessastare,asmalignantasrazorbladepants.

Otherrobe-shadowsappearedaroundtheshapeandbegandriftingtowardsit.Whentheyreachedittheyvanished,andthecentralshapebecamedarkerand,somehow,morepresent.

Rincewinddidn'tturnandrun.TherewasnopointintryingtorunfromAuditors;theywerecertainlyfasterthananythingwithlegs.Butthatwasn'tthereason.Ifitwastimetorun,he'dconsidered,noothercalculationsapplied.Hewouldn'tevenworrythathisescaperoutewasblockedbysolidlava;mostthingscouldbeovercomeifyouranatthemhardenough.Therewas,however,anotherreason.Ithadpinktoes.

`Whymeddle?'saidtheAuditor.Thevoicesoundedwindyanduncertain,asifthespeakerwashavingtoassemblethewordsbyhand.Èntropywilalwaystriumph.'

Ìsittruethatyoudieifyouhaveanemotion?'saidRincewind.TheAuditorwasquitedarknow,whichmeantthatithasassembledenoughmasstomovesomethingquiteheavy,likeahumanhead.

`Wedonothaveemotion,'saidtheAuditor.Ìtisahumanaberration.Inyouwedetectthephysicalmanifestationrecognisabletousasfear.'

`Youcan'tjustkilpeople,youknow,'saidRincewind.`That'sagainsttherules.'

`Webelievetheremaybenoruleshere,'saidtheAuditor,movingforward.

`Wait,wait,wait!'saidRincewind,tryingtobackawayintosolidrock.

`You'resayingyoudon'tknowwhatfearis,right?'

`Wehavenorequirementtodoso,'saidtheAuditor.`Preparetoceasecoherentfunction.'

`Turnaround,'saidRincewind.

AndaweaknessoftheAuditorsisthattheyfindadirectcommandhardtodisobey,atleastforasecondortwo.Itturned,or,rather,flowedthroughitselfto

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facetheotherway.

ThelidoftheLuggageclosedwithàclop'likethesoundofatrouttakinganunwarymayfly.

Iwonderifitfoundoutwhatfearrealyis,Rincewindthought.Butmoregreyshapesweredistilingoutoftheair.Nowitwastimetorun.

EIGHTEEN

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STEAMENGINETIME

THEREWASDARWIN,SITTINGONabank,watchingthebees,thewasps,theflowers...InthelastparagraphofTheOriginwefindabeautifulandimportantpassagethathintsatafternoonsofthatkind:Itisinterestingtocontemplateanentangledbank,clothedwithmanyplantsofmanykinds,withbirdssingingonthebushes,withvariousinsectsflittingabout,andwithwormscrawlingthroughthedampearth,andtoreflectthattheseelaboratelyconstructedforms,sodifferentfromeachother,anddependentoneachotherinsocomplexamanner,havealbeenproducedbylawsactingaroundus.

GoaheadPaley,makemyday.

AlthatwizardlyefforttogethimtowriteTheOrigin,notTheOlogy.ItmatteredtoDarwin,ofcourse,anditmatterstothosewhochartthecourseofhistory.But,justaswecanaskwhetherLincoln'sassassinationrealyhadmucheffectonsubsequentevents,sowecanaskthesameaboutDarwin'slife'swork.Woulditrealyhavematteredifthewizardshadfailed?

Metaphoricalwizards,youappreciate.Yes,thosehappycoincidencesthatgotCharlesonboardtheBeagleandkepthimtheredolookatadsuspicious,butwizards?

Let'saskthequestioninamorerespectableway.HowradicalwasDarwin'stheoryofnaturalselection,realy?Didhehaveinsightsthatnoonebeforehimhadconsidered?Ordidhejusthappentobethepersonwhocaughtthepubliceye,withanideathathadbeenfloatingaroundforsometime?Howmuchcreditshouldhebegiven?

Thesamecanbe-andhasbeen-askedofmany`revolutionary'scientificconcepts.RobertHookegottheideaofinversesquare-lawgravitybeforeNewtondid.Minkowski,Poincare,andothersworkedoutmuchofspecialrelativitybeforeEinsteindid.Fractalswerearound,insomeform,foratleastacenturybeforeBenoitMandelbrotenergeticalypromotedthemandtheydevelopedintoamajorbranchofappliedmathematics.TheearliestsniffofchaostheorycanbefoundinPoincare'sprize-winningmemoironthestabilityofthesolarsystemin1890,probably75yearsbeforethesubjectwasperceivedas`takingoff.

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Howdoscientificrevolutionsgetstarted,andwhatdecideswhogetsthecredit?Isittalent?Aflairforpublicity?Alottery?

PartoftheanswertothesequestionscanbefoundinRobertThurston's1878studyofanotherimportantVictorianinnovation,whichPonderStibbonsunerringlyhomedinoninChapter3.ThebookisAHistoryoftheGrowthoftheSteamEngine.Thesecondparagraphsays:Historyilustratestheveryimportanttruth:inventionsarenever,asgreatdiscoveriesareseldom,theworkofanyonemind.Everygreatinventionisrealyeitheranaggregationofminorinventions,orthefinalstepinaprogression.Itisnotacreation,butagrowthastrulysoasisthatofthetreesintheforest.Thesameinventionisfrequentlybroughtoutinseveralcountries,andbyseveralindividuals,simultaneously.

Thurston'stopicremindsusofacommonmetaphorforthiskindofapparentlysimultaneousinvention:steamenginetime.Whenit'ssteamenginetime,suddenlyeveryoneismakingsteamengines.Whenit'sevolutiontime,everyoneisinventingatheoryofevolution.Whenit'sVCR

time,everyoneismakingvideocassetterecorders.Whenit'sDotcomtime,everyoneissettingupInternettradingsystems.Andwhenit'sDotcom-going-busttime,altheDotcomsaregoingbust.

Therearetimeswhenhumanaffairsrealydoseemtorunonpreconstructedtracks.Somedevelopmentbecomesinevitable,andsuddenlyit'severywhere.Yet,justbeforethatpropitiousmoment,itwasn'tinevitableatal,otherwiseitwouldhavehappenedalready.`Steamenginetime'isaconvenientmetaphorforthiscuriousprocess.Theinventionofthesteamenginewasn'tthefirstexample,anditcertainlywasn'tthelast,butitisoneofthebestknown,andit'squiteweldocumented.

Thurstondistinguishesinventionfromdiscovery.Hesaysthatinventionsareneverthecreationofasingleindividual,whereasgreatdiscoveriesseldomare.However,thedistinctionisn'talwaysclearcut.Didancienthumansdiscoverfireasaphenomenonofnature,ordidtheyinventfireasatechnologytokeeppredatorsaway,lightthecave,andcookfood?Thenaturalphenomenonsurelycamefirst,intheformofbrush-orforestfirestriggeredbylightning,orpossiblyadropletofwateraccidentalyactingasalenstoconcentratetheSun'sraysontoapieceofdrygrass.[1]

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However,thatkindof`discovery'doesn'tgoanywhereuntilsomeonefindsauseforit.Itwastheideaofcontrolingfirethatmadethedifference,andthatseemsmoreofaninventionthanadiscovery.Except...youfindouthowtocontrolfirebydiscoveringthatfiresdon'tspread(soeasily)acrossbaresoil,thattheycanbespreadveryeasilyindeedbypickingupaburningstickanddroppingitintodrybrushwood,ortakingithometothecave...

Theinventivestep,ifthereissuchathing,consistsofputtingtogetherseveralindependentdiscoveriessothatwhatemergeshasgenuinenovelty.

Drygrassanddropsofwaterarenotcommonlyassociated,butperhapsadampelephanthadjustemergedfromarivercrossingontodrysavannah...Oh,inventyourownexplanation.

Soinventionsareoftenprecededbyaseriesofdiscoveries.Similarly,discoveriesareoftenprecededbyinventions.Thediscoveryofsunspotsrestedontheinventionofthetelescope,thediscoveryofamoebasandparameciumsinpondwaterrestedontheinventionofthemicroscope.Inshort,inventionanddiscoveryareintimatelyentwined,andit'sprobablypointlesstotrytoseparatethem.Moreover,thesignificantinstancesofbotharemucheasiertospotinretrospectthantheywereatthetimetheyfirsthappened.Hindsightisawondrousthing,butitdoeshavethevirtueofprovidinganexplicitcontextforworkingoutwhatdid,ordidnot,matter.

Hindsightletsusorganisetheremarkablymessyprocessofinvention/discovery,andtelconvincingstoriesaboutit.

Theproblemis,mostofthosestoriesaren'ttrue.

Aschildren,manyofuslearnedhowthesteamenginewasinvented.TheyoungJamesWatt,agedaboutsix,waswatchingakettleboil,andhenoticedthatthepressureofthesteamcouldliftthelid.Inaclassicèureka'

moment,itdawnedonhimthatarealybigkettlecouldliftrealyheavybitsofmetal,andthesteamenginewasborn.

TheoriginaltelerofthisstorywastheFrenchmathematicianFrancoisArago,authorofoneofthefirstbiographiesofWatt.Foralweknow,thestorymaybetrue,thoughitismorelikelyàlie-tochildren',oreducationalaid,*likeNewton'sapple.EveniftheyoungWattwasindeedsuddenlyinspiredbyaboilingkettle,

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hewasbynomeansthefirstpersontomaketheconnectionbetweensteamandmotivepower.Hewasn'teventhefirstpersontobuildaworkingsteamengine.Hisclaimtofamerestsonsomethingmorecomplex,yetmoresignificant.InWatt'shands,thesteamenginebecameaneffectiveandreliabletool.Hedidn't`perfect'it-manysmalerimprovementsweremadeafterWatt-buthebroughtitintoprettymuchitsfinalform.

[1].See7beScienceofDiscworld.

Wattwrotein1774:`Thefireengine(=steamengine)thatIhaveinventedisnowgoing,andanswersmuchbetterthananyotherthathasyetbeenmade.'InconjunctionwithhisbusinesspartnerMatthewBoulton,Wattmadehimselfthehouseholdnameofthesteamengine.Andithasdonehisreputationnoharmthat,inthewordsofThurston:Òfthepersonalhistoryoftheearlierinventorsandimproversofthesteam-engine,verylittleisascertained;butthatofWatthasbecomewelknown.'

WasDarwinjustanotherWatt?Didhegetcreditforevolutionbecausehebroughtitintoapolished,effectiveform?Ishefamousbecausewehappentoknowsomuchabouthispersonalhistory?Darwinwasanobsessiverecord-keeper,hehardlythrewawayasinglescrapofpaper.

Biographerswereabletodocumenthislifeinexceptionaldetail.Itcertainlydidhisreputationnoharmthatsuchawealthofhistoricalmaterialwasavailable.

Inordertomakecomparisons,let'sreviewthehistoryofthesteamengine,avoidinglies-to-childrenasmuchaswecan.Thenwe'llookatDarwin'sintelectualpredecessors,andseewhetheracommonpatternemerges.

Howdoessteamenginetimework?Whatfactorsleadtoaculturalexplosion,asanapparentlyradicalideàtakesoffandtheworldchangesforever?Doestheideachangetheworld,ordoesachangingworldgeneratetheidea?

Wattcompletedhisfirstsignificantsteamenginein1768,andpatenteditin1769.Itwasprecededbyvariousprototypes.ButthefirstrecordedreferencetosteamasasourceofmotivepoweroccursinthecivilisationofancientEgypt,duringtheLateKingdomwhenthatcountrywasunderRomanrule.Around150BC(thedateisveryapproximate)HeroofAlexandriawroteamanuscriptSpiritaliaseuPneumatica.Onlypartialcopieshavesurvivedtothepresentday,butfromthemwelearnthatthemanuscriptreferredtodozensofsteam-driven

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machines.WeevenknowthatseveralofthempredatedHero,becausehetelsusso;somewerethepreviousworkoftheinventorCestesibus,celebratedforthegreatnumberandvarietyofhisingeniouspneumaticmachines.Sowecanseethebeginningsofsteamenginetimelongago,butinitialprogresswassoquietandslowthatsteamenginetimeitselfwasstilfarinthefuture.

OneofHero'sdeviceswasaholowairtightaltar,withthefigureofagodorgoddessontop,andatuberunningthroughthefigure.Unknowntothepunters,thealtarcontainswater.Whenaworshipperlightsafireontopofthealtar,thewaterheatsupandproducessteam.Thepressureofthesteamdrivessomeoftheremainingliquidwaterupthepipe,andthegodoffersalibation.(Asmiraclesgothisoneisquiteeffective,anddistinctlymoreconvincingthanastatueofacowthatoozesmilkoroneofasaintthatweeps.)Similardeviceswerecommonplacefromthe1960stomaketeaatthebedsideandpouritoutautomaticaly.Theystilexisttoday,butarehardertofind.

AnotherofHero'smachinesusedthesameprincipletoopenatempledoorwhensomeonelitafireonanaltar.Thedeviceisquitecomplicated,andwedescribeittoshowthattheseancientmachineswentfarbeyondbeingmeretoys.Thealtaranddoorareaboveground,themachineryisconcealedbeneath.Thealtarisholow,filedwithair.Apiperunsverticalydownfromthealtarintoametalspherefulofwater,andasecondinvertedU-shapedpipeactslikeasiphon,withoneendinsidethesphereandtheotherinsideabucket.Thebuckethangsoverapuley,andropesfromthebucketwindroundtwoverticalcylinders,inlinewiththehingesofthedoorandattachedtothedoor'sedge.Theythenrunoverasecondpuleyandterminateinaheavyweightwhichactsasacounterbalance.Whenapriestlightsthefire,theairinsidethealtarexpands,andthepressuredriveswateroutofthesphere,throughthesiphon,andintothebucket.Asthebucketdescendsundertheweightofwater,theropescausethecylinderstoturn,openingthedoors.

Thenthere'safountainthatoperateswhenthesun'sraysfalonit,andasteamboilerthatmakesamechanicalblackbirdsingorblowsahorn.Yetanotherdevice,oftenreferredtoastheworld'sfirststeamengine,boilswaterinacauldronandusesthesteamtoturnametalglobeaboutahorizontalaxis.Thesteamemergesfromaseriesofbentpipesaroundthesphere'sèquator',atrightanglestotheaxis.

Indesign,thesemachinesweren'ttoys,butasfarastheirapplicationswent,they

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mightaswelhavebeen.Onlythedoor-openercomesclosetodoinganythingwewouldconsiderpractical,althoughthepriestsprobablyfoundtheabilitytoproducemiraclesondemandtobequiteprofitable,andthat'spracticalenoughformostbusinessmentoday.

Lookingbackfromthetwenty-firstcentury,itseemsastonishingthatittooksteamenginetimesolongtogainpropermomentum,withaltheseexamplesofsteampoweronpublicdisplayalovertheancientworld.

Especialysincetherewasplentyofdemandformechanicalpower,forthesamereasonsthatfinalygavebirthtosteamenginetechnologyintheeighteenthcentury-pumpingwater,liftingheavyweights,mining,andtransport.Sowelearnthatittakesmorethanthemereabilitytomakesteamengines,eveninconjunctionwithaclearneedforsomethingofthatkind,tokick-startsteamenginetime.

Andsothesteamenginebumbledalong,neverdisappearingentirely,butnevermakinganykindofbreakthrough.In1120thechurchatRheimshadwhatlookssuspiciouslylikeasteampoweredorgan.In1571Matthesiusdescribedasteamengineinasermon.In1519theFrenchacademicJacobBessonwroteabouttheproductionofsteamanditsmechanicaluses.In1543theSpaniardBalsodeGarayisreputedtohavesuggestedtheuseofsteamtopoweraship.LeonardodaVincidescribedasteam-gunthatcouldthrowaheavymetalbal.In1606FlorenceRivault,gentlemanofthebedchambertoHenryIV,discoveredthatametalbombshelwouldexplodeifitwasfiledwithwaterandheated.In1615,SalomondeCaius,anengineerunderLouisXII,wroteaboutamachinethatusedsteamtoraisewater.In1629...butyougettheidea.Itwentonlikethat,withpersonafterpersonreinventingthesteamengine,until1663.

InthatyearEdwardSomerset,MarquisofWorcester,notonlyinventedasteampoweredmachineforraisingwater:hegotitbuilt,andinstaled,twoyearslater,atVauxhal-nowpartofLondon,butthenjustoutsideit.Thiswasprobablythefirstgenuineapplicationofsteampowertoaseriouspracticalproblem.Nodrawingofthemachineexists,butitsgeneralformhasbeeninferredfromgrooves,stilsurviving,inthewalsofRaglanCastle,whereitwasinstaled.Worcesterplannedtoformacompanytoexploithismachine,butfailedtoraisethecash.Hiswidowinherturnmadethesameattempt,withthesamelackofsuccess.Sothat'sanothernecessaryingredientforsteamenginetime:money.

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Insomeways,Worcesterwasthetruecreatorofthesteamengine,buthegetslittlecredit,becausehewasjustatinybitaheadofthewave.Hedoesmarkamomentatwhichthewholegamechanged,however:fromthispointon,peopledidn'tjustinventsteamengines-theyusedthem.By1683,SirSamuelMorlandwasbuildingsteampoweredpumpsforLouisXIV,andhisbookofthatyearrevealsadeepfamiliaritywiththepropertiesofsteamandtheassociatedmechanisms.Theideaofthesteamenginehadnowarrived,alongwithafewofthethingsthemselves,earningtheirlivingbyperformingusefultasks.Butitstilwasn'tsteamenginetime.

Now,however,themomentumbegantogrowrapidly,andwhatgaveitarealybigpushwasmining.Mines,forcoalorminerals,hadbeenaroundformilennia,butbythestartoftheeighteenthcenturytheywerebecomingsobig,andsodeep,thattheyranintowhatquicklybecametheminer'sgreatestenemy:water.

Thedeeperyoutrytodigmines,themorelikelytheyaretobecomeflooded,becausetheyaremorelikelytorunintounderlyingreservoirsofwater,orcracksthatleadtosuchreservoirs,orjustcracksdownwhichwaterfromabovecanflow.Traditionalmethodsofremovingwaterwerenolongersuccessful,andsomethingradicalydifferentwasneeded.Thesteamenginefiledthegapneatly.Twopeople,aboveal,madeitpossibletobuildsuitablemachinery:DennisPapinandThomasSavery.

PapintrainedinmathematicsundertheJesuitsatBlois,andinmedicineinParis,wherehesettledin1672.HejoinedthelaboratoryofRobertBoyle,whowouldnowadaysbecaledanexperimentalphysicist.Boylewasworkingonpneumatics,thebehaviourofgases-'Boyle'slaw',relatingthepressureandvolumeofagasatconstanttemperature,continuestobetaughttothisday.Papininventedthedoubleairpumpandtheairgun,andthenheinventedtheDigester.Thisisbestdescribedasapressure-cooker,whichisasaucepanwiththickwalsandathicklid,heldonsecurelysothatwaterinsideboilstoformhigh-pressuresteam.Foodcontainedinthepancooksveryquickly.

Thecookeryaspectdoesn'taffectourstory,butonebitoftechnologydoes.

Toavoidexplosions,Papinaddedasafetyvalve,afeaturereplicatedinthesixtiesdomesticversion,andanimportantinventionbecauseearlyinvolvementwithsteamengineswasdangerousatthebestoftimes.Theideaprobablyoriginatedearlier,butPapingetsthecreditforusingittocontrolsteampressure.

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In1687hemovedtotheUniversityofMarburg,whereheinventedthefirstmechanicalsteamengineandthefirstpistonengine.Throughouthiscareer,hecarriedoutinnumerableexperimentswithsteam-relatedapparatus,andintroducedmanysignificantpiecesofgadgetry.

Steamenginetimewashottingup.Savery,whoalsotrainedinmathematics,broughtittotheboil.In1698hepatentedthefirststeampoweredpumpthatwasactualyusedtoclearminesofunwantedwater-inthiscase,thedeepminesofCornwal.HesentaworkingmodeltotheRoyalSociety,andlatershowedamodel`fireengine',asthemachineswerethenconfusinglycaled,toWiliamII.TheKinggrantedhimapatent:AgranttoThomasSaveryofthesoleexerciseofanewinventionbyhiminvented,forraisingofwater,andoccasioningmotiontoalsortsofmilworks,bytheimportantforceoffire,whichwilbeofgreatuseindrainingmines,servingtownswithwater,andfortheworkingofalsortsofmils,whentheyhavenotthebenefitofwaternorconstantwinds;toholdfor14

years;withusualclauses.

Steamenginetimewascloseathand.WhatclincheditwasthatSaverywasabornbusinessman.Hedidn'twaitfortheworldtobeatapathtohisdoor:headvertised.HegavelecturesattheRoyalSociety,someofwhichwerepublishedinitsjournals.Hecirculatedaprospectusamongmine-ownersandmanagers.Andtheselingpoint,naturaly,wasprofit.Ifyoucanopenupdeeperlevelsofyourmine,youcanextractmoremineralsandmakemoremoneyoutofthesamemineandthesamebitofland.

TwomoremajorstepswereneededbeforewhatThurstoncalsthèmodern'steamengine-thatof125yearsago-becamefirmlyestablished.Thefirstwastomovefromspecialised,single-purposemachines,tomulti-purposeones.Thesecondwastoimprovetheengine'sefficiency.

Themovetomulti-purposesteamengineswasmadebyThomasNewcomen,ablacksmithbytrade,whointroducedaradicalnewkindofengine,theàtmosphericsteamengine'.Previousengineshadeffectivelycombinedasteam-drivenpistonandapumpinthesameapparatus.

Newcomenseparatedthecomponents,andthrewinaseparateboilerandacondensertoboot.Thepistonmovesupanddownlikeànoddingdonkey',drivingarod,whichcanbeattachedto...anythingyoulike.

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AnotherengineerwhomustbementionedherewasJohnSmeaton,whoscaledNewcomen'sdesignuptomuchlargersize.

Now,finaly,wecometoJamesWatt.Whatevercredithedeserves,itisclearthathestoodontheshouldersofanumberofgiants.Evenifhehadbeencapableofinventingthesteamengineonhisown,theplainfactisthathedidn't.Hisgrandfatherwasamathematician-thereseemtobealotofmathematiciansinthehistoryofthesteamengine-andWattinheritedhisabilities.Hecarriedoutlotsofexperiments,andhemadequantitativemeasurements,arelativelynewidea.Heworkedouthowheattraveledthroughthematerialsoftheengine,andhowmuchcoalittooktoboilagivenamountofwater.Andherealisedthatthekeytoanefficientsteamenginewastocontrolunnecessaryheatloss.Theworstlossoccurredinthecylinderthatpoweredthepiston,whichkeptchangingtemperature.Wattrealisedthatthecylindershouldalwaysbekeptatthesametemperatureasthesteamthatenteredit-buthowcouldthatbedone?Theanswer,whenhefinalychanceduponit,wassimpleandelegant:

IhadgonetotakeawalkonafineSabbathafternoon.IhadenteredtheGreenbythegateatthefootofCharlotteStreet,andhadpassedtheoldwashing-house.Iwasthinkingupontheengineatthetime,andhadgoneasfarastheherd'shouse,whentheideacameintomymindthat,assteamwasanelasticbody,itwouldrushintoavacuum,and,ifacommunicationweremadebetweenthecylinderandanexhaustedvessel,itwouldrushintoit,andmightbecondensedtherewithoutcoolingthecylinder...IhadnotwalkedfartherthantheGolfhouse,whenthewholethingwasarrangedinmymind.

Suchaneasythingtocomeupwith-don'tcoolthesteaminthecylinder,coolitsomewhereelse.Yetitimprovedthemachine'sefficiencysomuchthatwithinafewyearstheonlysteamenginesthatanyoneeventhoughtofinstalingwerethoseofWattandhisfinancialpartnerBoulton.Boulton-and-Wattenginescorneredthemarket.Norealysignificantimprovementsweresubsequentlymadetotheirdesign.Or,tobemoreaccurate,laterìmprovements'supplantedthesteamenginewithenginesofaverydifferentdesign,drivenbycoalandoil.Thesteamenginehadevolvedtothepinnacleofitsexistence,andwhatdisplaceditwas,ineffect,anewspeciesofenginealtogether.

Inretrospect,steamenginetimearrivedaroundtheperiodofSavery,whentheabilitytomakepracticalmachinescoincidedwithagenuineneedfortheminanindustrythatcouldaffordtopayforthemandwouldmakemoreprofitsasa

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result.Addtothatasoundbusinessmind,tonoticethesituationandexploitit,andasenseforpublicitytoraisemoneyfrominvestorsandgettheideaofftheground,andthesteamenginewentlikea...train.

Ironicaly,beforemostpeoplerealisedthatsteamenginetimehadarrived,ithadgoneagain,andintheendtherewasonlyonewinner.Therestofthecompetitionfelbythewayside.AndthatiswhyWattgetssomuchcredit,andwhy,ultimately,hedeservesit.Buthealsodeservescreditforhissystematicquantitativeexperiments,hisfocusonthetheorybehindthesteamengine,andhisdevelopmentoftheconcept-notasitsinventor.

Certainlynotforwatchingakettleasakid.

ThehistoryoftheintroductionoftheBoulton-and-Wattsteamengineisessentialyanevolutionaryone:thefittestdesignsurvived,thelessfitweresupersededandvanishedfromthehistoricalrecord.WhichbringsustoDarwin,andnaturalselection.TheVictorianerawas`steamenginetime'

forevolution;Darwinwasjustoneofmanypeoplewhorecognisedthemutabilityofspecies.Doeshedeservethecredithegets?Washe,likeWatt,thepersonwhobroughtthetheorytoitsculmination?Ordidheplayamoreinnovativerole?

IntheintroductiontoOrigin,Darwinmentionsseveralofhispredecessors.

Sohecertainlywasn'ttryingtotakecreditfortheideasofothers.UnlessyousubscribetotheratherMachiavelianschoolofthoughtthatgivingcredittoothersisjustasneakywayofdamningthemwithfaintpraise.-

Onepredecessorthathedoesnotmentionisperhapsthemostinterestingofal-hisowngrandfather,ErasmusDarwin.PerhapsCharlesfeltthatErasmuswasabittoonuttytomention,especialybeingarelative.

ErasmusknewJamesWatt,andmayhavehelpedhimtopromotehissteamengine.TheywerebothmembersoftheLunarSociety,anorganisationofBirminghamtechnocrats.AnotherwasJosiahWedgwood,Darwin'suncleJos'sgrandfatherandfounderofthefamousceramicscompany.The'Lunaticks'metonceamonthatthetimeofthefulmoon-

notforpaganormysticreasons,orbecausetheywerealwerewolves,but

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becausethatwaytheycouldseetheirwayeasilyastheyrodehomeafterafewdrinksandagoodmeal.

Erasmus,aphysician,couldalsoturnaniftyhandtomachinery,andheinventedanewsteeringmechanismforcarriages,ahorizontalwindmiltogrindJosiah'spigments,andamachinethatcouldspeaktheLord'sPrayerandtheTenCommandments.Whenthe1791riotsagainst`philosophers'

(scientists)andfor`ChurchandKing'putpaidtotheLunarSociety,Erasmuswasjustputtingthefinishingtouchestoabook.ItstitlewasZoonomia,anditwasaboutevolution.

Not,however,byCharles'smechanismofnaturalselection.Erasmusdidn'trealydescribeamechanism.Hejustsaidthatorganismscouldchange.

Alplantandanimallife,Erasmusthought,derivedfromliving`filaments'.

Theyhadtobeabletochange,otherwisethey'dstilbefilaments.AwareofLyel'sDeepTime,Erasmusarguedthat:Inthegreatlengthoftime,sincetheearthbegantoexist,perhapsmilionsofagesbeforethecommencementofthehistoryofmankind,woulditbetooboldtoimagine,thatalwarm-bloodedanimalshavearisenfromonelivingfilament,whichthefirstgreatcauseendowedwithanimality,withthepowerofacquiringnewparts,attendedbynewpropensities,directedbyirritations,sensations,volitions,andassociations;andthuspossessingthefacultyofcontinuingtoimprovebyitsowninherentactivity,andofdeliveringdownthoseimprovementsbygenerationtoitsposterity,worldwithoutend!IfthissoundsLamarckian,that'sbecauseitwas.Jean-BaptisteLamarckbelievedthatcreaturescouldinheritcharacteristicsacquiredbytheirancestors-thatif,say,ablacksmithacquiredhugemusculararmsbyvirtueofworkingforyearsathisforge,thenhischildrenwouldinheritsimilararms,withouthavingtodoalthathardwork.InsofarasErasmusenvisagedamechanismforheredity,itwasmuchlikeLamarck's.Thatdidnotpreventhimhavingsomeimportantinsights,notalofthemoriginal.Inparticular,hesawhumansassuperiordescendantsofanimals,notasaseparateformofcreation.Hisgrandsonfeltthesame,whichiswhyhecaledhislaterbookonhumanevolutionTheDescentofMan.Alveryproperandscientific.ButRidculyisright.Àscent'wouldhavebeenbetterpublicrelations.

CharlescertainlyreadZoonomia,duringtheholidaysafterhisfirstyearat

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EdinburghUniversity.Heevenwrotethewordontheopeningpageofhis`BNotebook',theoriginofOrigin.Sohisgrandfather'sviewsmusthaveinfluencedhim,butprobablyonlybyaffirmingthepossibilityofspecieschange.[1]Thebigdifferencewasthatfromtheverybeginning,Charleswaslookingforamechanism.Hedidn'twanttopointoutthatspeciescouldchange-hewantedtoknowbowtheychanged.Anditisthisthatdistinguisheshimfromnearlyalofthecompetition.

Themostseriouscompetitorwehavementionedalready:Walace.DarwinacknowledgestheirjointdiscoveryinthesecondparagraphoftheintroductiontoOrigin.ButDarwinwroteaninfluentialandcontroversialbook,whereasWalacewroteoneshortpaperinatechnicaljournal.

Darwintookthetheorymuchfurther,assembledmuchmoreevidence,andpaidmoreattentiontopossibleobjections.

HeprefacedOriginwithÀnHistoricalSketch'ofviewsoftheoriginofspecies,andinparticulartheirmutability.AfootnotementionsaremarkablestatementinAristotle,whoaskedwhythevariousparts[1]Whatwouldhavehappened-ifDarwinhadgonebackintimeandkiledhisowngrandfather?

ofthebodyfittogether,sothat,forexample,theupperandlowerteethmeettidily,insteadofgrindingagainsteachother.TheancientGreekphilosopheranticipatednaturalselection:Wheresoever,therefore,althingstogether(thatisalthepartsofonewhole)happenedlikeasiftheyweremadeforthesakeofsomething,thesewerepreserved,havingbeenappropriatelyconstitutedbyaninternalspontaneity;andwhatsoeverthingswerenotthusconstituted,perished,andstilperish.

Inotherwords:ifbychance,orsomeunspecifiedprocessthecomponentscarriedoutsomeusefulfunction,theywouldappearinlatergenerations,butiftheydidn't,thecreaturethatpossessedthemwouldnotsurvive.

AristotlewouldhavemadeshortshriftofPaley.

Next,DarwintacklesLamarck,whoseviewsdatefrom1801.Lamarckcontendedthatspeciescoulddescendfromotherspecies,mostlybecauseclosestudyshowsendlesstinygraduationsandvarietieswithinaspecies,sotheboundariesbetweendistinctspeciesismuchfuzzierthanweusualythink.ButDarwinnotestwoflaws.Oneisthebeliefthatacquiredcharacteristicscanbe

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inherited-Darwincitesthegiraffe'slongneckasanexample.TheotheristhatLamarckbelievedin`progress'-aone-wayascenttohigherandhigherformsoforganisation.

Alongseriesofminorfiguresfolows.Amongthemisonenoteworthybutobscurefelow,PatrickMatthew.In1831,hepublishedabookaboutnavaltimber,inwhichtheprincipleofnaturalselectionwasstatedinanappendix.Naturalistsfailedtoreadthebook,untilMatthewdrewattentiontohisanticipationofDarwin'scentralideaintheGardener'sChroniclein1860.

NowDarwinintroducesabetter-knownforerunner,theVestigesoftheNaturalHistoryofCreation.Thisbookwaspublishedanonymouslyin1844

byRobertChambers;itisclearthathewasalsoitsauthor.ThemedicalschoolsofEdinburghwereawashwiththerealisationthatentirelydifferentanimalshaveremarkablysimilaranatomies,suggestingacommonoriginandthereforethemutabilityofspecies.Forexample,thesamebasicarrangementofbonesoccursinthehumanhand,thepawofadog,thewingofabird,andthefinofawhale.Ifeachwereaseparatecreation,Godmusthavebeenrunningoutofideas.

Chamberswasasocialite-heplayedgolf-andhedecidedtomakethescientificvisionoflifeonEarthavailabletothecommonman.Abornjournalist,Chambersoutlinednotjustthehistoryoflife,butthatoftheentirecosmos.Andhefiledthebookwithslydigsat`thosedogsoftheclergy'.

Thebookwasanovernightsensation,andeachsuccessiveeditionslowlyremovedvariousblundersthathadmadethefirsteditioneasytoattackonscientificgrounds.ThevilifiedclergythankedtheirGodthattheauthorhadnotbegunwithoneofthelatereditions.

Darwin,whorespectedtheChurch,hadtorefertoVestiges,buthealsohadtodistancehimselffromit.Inanycase,hefounditwoefulyincomplete.

Inhis`HistoricalSketch',Darwinquotedfromthetenthàndmuchimproved'edition,objectingthattheanonymousauthorofVestigescannotaccountforthewayorganismsareadaptedtotheirenvironmentsorlifestyles.Hetakesupthesamepointinhisintroduction,suggestingthattheanonymousauthorwouldpresumablysaythat:Afteracertainnumberofunknowngenerations,somebirdhadgivenbirthtoawoodpecker,andsomeplanttothemisseltoe{sic},andthatthesehadbeenproducedperfectaswenowseethem;butthisassumptionseems

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tometobenoexplanation,foritleavesthecaseofthecoadaptationsoforganicbeingstoeachotherandtotheirphysicalconditionsoflife,untouchedandunexplained.

Moreheavyweightsfolow,interspersedwithlesserfigures.ThefirstheavyweightisRichardOwen,whowasconvincedthatspeciescouldchange,addingthattoazoologisttheword`creation'meansàprocessheknowsnotwhat'.ThenextisWalace.Darwinreviewshisinteractionswithboth,atsomelength.HealsomentionsHerbertSpencer,whoconsideredthebreedingofdomesticatedvarietiesofanimalsasevidencethatspeciescouldchangeinthewild,withouthumanintervention.SpencerlaterbecameamajorpopulariserofDarwin'stheories.Heintroducedthememorablephrasèsurvivalofthefittest',whichunfortunatelyhascausedmoreharmthangoodtotheDarwiniancause,bypromotingarathersimple-mindedversionofthetheory.

AnunexpectednameisthatoftheReverendBadenPowel,whose1855

ÈssaysontheUnityofWorlds'statesthattheintroductionofnewspeciesisanaturalprocess,notamiracle.CreditformutabilityofspeciesisalsogiventoKarlErnstvonBaer,Huxley,andHooker.

Darwinwasdeterminednottomissoutanyonewithalegitimateclaim,andinalhelistsmorethantwentypeoplewhoinvariouswaysanticipatedpartsofthistheory.Heisabsolutelyexplicitthatheisnotclaimingcreditfortheideathatspeciescanchange,whichwascommoncurrencyinscientificcircles-and,asBadenPowelshows,beyond.WhatDarwinislayingclaimtoisnottheideaofevolution,butthatofnaturalselectionasanevolutionarymechanism.

So...wecomefulcircle.Doesaninnovativeideachangetheworld,ordoesachangingworldgeneratetheidea?

Yes.

It'scomplicity.Bothofthesethingshappen-notonce,butoverandoveragain,eachprogressivelyalteringtheother.Innovationsredirectthecourseofhumancivilisation.Newsocialdirectionsencouragefurtherinnovation.Theworldofhumanideas,andtheworldofthings,recursivelymodifyeachother.

Thatiswhathappenstoaplanetwhenaspeciesevolvesthatisnotmerelyinteligent,butwhatweliketocalexteligent.Onethatcanstoreitsculturalcapital

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outsideindividualminds.Whichletsthatcapitalgrowvirtualywithoutlimit,andbeaccessibletoalmostanybodyinanysucceedinggeneration.

Exteligentspeciestakenewideasandrunwiththem.BeforetheinkwasdryonOrigin,biologistsandlaymenwerealreadytryingtotestitsideas,shootthemdown,pushthemfurther.IfDarwinhadwrittenOlogy,andifnobodyelsehadwrittensomethinglikeOrigin,thenVictorianexteligencewouldhavebeenenfeebled,andperhapsthemodernworldwouldhavetakenlongertoarrive.

Butitwasevolutiontime.Somebodywouldhavewrittensuchabook,andsoon.Andinthatalternat(iv)eworldofif,heorshewouldhavegotthecreditinstead.

Soit'sonlyfairtogiveDarwinthecreditinthisworld.Steamenginetimenotwithstanding.

NINETEEN

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LIESTODARWIN

ARCHCHANCELLORRIDCULLY'SMOUTHDROPPEDOPEN.

`Youmeankiled?'hesaid.

+++No+++,Hexwrote,+++Imeanvanished.DarwindisappearsfromRoundworldin1850.Thisisanewdevelopment.Thatistosay,ithasalwayshappened,buthasalwayshappenedonlyforthelasttwominutes+++

Ìrealyhatetimetravel,'sighedtheDean.

`Kidnapped?'saidPonder,hurryingacrossthehal.

+++Unknown.Phasespacecurrentlycontainsproto-historiesinwhichhereappearsafterafractionofonesecondandotherswhereheneverreappearsatal.Claritymustberestoredtothisnewnode+++

Àndyouonlytelusthisnow?'saidtheDean.

+++Ithasonlyjusthappened+++

`But,'theDeanattempted,`whenyoulookedatthis...historybefore,thiswasn'thappening!'

+++Correct.Butthatwasthenthen,thisisthennow.Somethinghasbeenchanged.Isurmisethatthisisasaresultofouractivities.And,havinghappened,ithasalwayshappened,fromthepointofviewofanobserverinRoundworld+++

Ìt'slikeaplay,Dean,'saidPonderStibbons.`Thecharactersjustseetheactthey'rein.Theydon'tseethescenerybeingshiftedbecausethat'snotpartoftheplay.'

+++Despitebeingwrongineveryimportantrespect,thatisaverygoodanalogy+++Hexwrote.

`Haveyouanyideawhereheis?'saidRidculy.+++No+++

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`Wel,don'tjustsitthere,man,findhim!'

Rincewindreappearedabovethelawn,androledexpertlywhenhehittheground.Otherwizards,nothinglikesoexperiencedatdealingwiththevicissitudesoftheworld,layaboutgroaningorstaggeredarounduncertainly.

Ìtwearsoff,'hesaid,ashesteppedoverthem.`Youmightthrowupabitatfirst.Othersymptomsofrapidcross-dimensionaltravelareshort-termmemoryloss,ringingintheears,constipation,diarrhoea,hotflushes,confusion,bewilderment,amorbiddreadoffeet,disorientation,nosebleeds,eartwinges,grumblingofthespleen,widgeons,andshort-termmemoryloss.'

ÌthinkI'dliketo...thing...endofyourlifething...'murmuredayoungwizard,crawlingacrossthedampgrass.Nearby,anotherwizardhadpuledoffhisbootsandwasscreamingathistoes.

Rincewindsighedandmadeagrabatanelderlywizard,whowasstaringaroundlikealostlamb.Hewasalsosoakingwet,havingapparentlyalsolandedinthefountain.

Helookedfamiliar.ItwasimpossibletoknowalthewizardsinUU,ofcourse,butthisonehehaddefinitelyseenbefore.

ÀreyoutheChairofObliqueFrogs?'hesaid.

Themanblinkedathim.Ì...don'tknow,'hesaid.ÀmI?'

ÒrtheProfessorofRevolvings?'saidRincewind.Ìusedtowritedownmynameonapieceofpaperbeforethissortofthing.That'salwaysahelp.

YoulookabitliketheProfessorofRevolvings.'

`DoI?'saidtheman.

Thislookedlikeaverybadcase.`Let'sfindyouyourpointyhatandsomecocoa,shalwe?You'lsoonfeel-'

TheLuggagelandedwithathump,raiseditselfonitslegs,andtrottedaway.ThepossibleProfessorofRevolvingsstaredatit.

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`That?Oh,it'sjusttheLuggage,'saidRincewind.Themandidn'tmove.

`Sapientpearwood,youknow?'Rincewindcarriedon,watchinghimanxiously.Ìt'sverycleverwood.Youcan'tgettheverycleverwoodanymore,notaroundhere.'

Ìtmovesabout?'saidthepossibleprofessor.

Òh,yes.Everywhere,'saidRincewind.

Ìknowofnoplantlifethatmovesabout!'

`Realy?IwishIdidn't,'saidRincewind,fervently,grippingthemanalittletighter.`Comeon,afteranicewarmdrinkyou'l-'

Ìmustexamineitclosely!Iamaware,ofcourseoftheso-caledVenusFly-'

`Pleasedon't!'Rincewindpleaded,pulingthemanback.`YoucannotbotanisetheLuggage!'

Thebewilderedmanlookedaroundwithadesperationthatwasshadingintoanger.

`Whoareyou,sir?Whereisthisplace?Whyarealthesepeoplewearingpointyhats?IsthisOxford?Whathashappenedtome!'

AchilyfeelingwascreepingoverRincewind.Quiteprobably,healoneofalthewizardshadreadPonder'sbriefingsastheyarrivedbysurlyporter;itpaidtoknowwhatyoumighthavetorunawayfrom.Onehadincludedapictureofamanwholookedasifhewasevolvingalbyhimself,aneffectcausedbytheriotoffacialhair.Thismanwasnotthatman.Notyet.ButRincewindcouldseethathewouldbe.

Ùm,'hesaid,Ìthinkyoushouldcomeandmeetpeople.'

ItseemedtothewizardsthatMrDarwintookitalverywel,aftertheinitialandquiteunderstandablescreaming.

Ithelpedthattheytoldhimquitealotoflies.Noonewouldliketobetoldthattheycamefromauniversecreatedquitebyaccidentand,moreover,bytheDean.

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Itcouldonlycausebadfeeling.Ifyouweretoldyouweremeetingyourmaker,you'dwantsomethingbetter.

ItwasPonderandHexwhosolvedthat.Roundworld'shistoryofferedalotofopportunities,afteral.

Ìdidn'tfeelanylightningstrike,'Darwinsaid,lookingaroundtheUncommonRoom.

Àh,youwouldn'thavedone,'saidPonder.`Thewholeforceofitthrewyouhere.'

Ànotherworld...'saidDarwin.Helookedatthewizards.Àndyouare...

magicalpractitioners...'

`Dohavealittlemoresherry,'saidtheChairofIndefiniteStudies.ThesherryglassinDarwin'shandfiledupagain.`Youcreatesherry?'hesaid,aghast.

Òhno,that'sdonebygrapesandsunshineandsoon,'saidRidculy.`Mycoleaguejustmoveditfromthedecanteroverthere.It'sasimpletrick.'

`We'realverygoodatit,'saidtheDeancheerfuly.

`Magicisbasicalyjustmovin'stuffaround,'saidRidculy,butDarwinwaslookingpasthim.TheLibrarianhadjustknuckledintotheroom,wearingtheoldgreenrobeheworeforimportantoccasionsorwhenhe'dhadabath.Heclimbedintoachairandheldupaglass;itfiledinstantly,andabananadroppedintoit.

`ThatisPongopongo!'saidDarwin,pointingashakingfinger.Ànape!'

`Weldonethatman!'saidRidculy.`You'dbeamazedathowmanypeoplegetthatwrong!He'sourLibrarian.Verygoodatit,too.Now,MrDarwin,there'sadelicatematterwe-'

Ìt'sanothervision,isn'tit?'saidDarwin.Ìt'smyhealth,Iknowit.Ihavebeenworkingtoohard.'Hetappedthechair.`Butthiswoodfeelssolid.

Thissherryisquitepassable.Butmagic,Imusttelyou,doesnotexist!'Besidehim,withalittlegurgle,hisglassrefiled.

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Justonemoment,sir,please,'saidPonder.`Didyousayanothervision?'

Darwinputhisheadinhishands.Ìthoughitwasanepiphany,'hegroaned.ÌthoughtthatGodhimselfappeareduntomeandexplainedHisdesign.Itmadesomuchsense.IhadrelegatedHimtothestatusofPrimeMover,butnowIseethatHeisimmanentinHiscreation,constantlyimpartingdirectionandmeaningtoital...or,'helookedup,blinking,`soIthought...'

Thewizardsstoodfrozen.Then,verycarefuly,Ridculysaid:`Divinevisitation,eh?Andwhenwasthis,exactly?'

Ìtwouldhavebeenafterbreakfast,'moanedDarwin.Ìtwasraining,andthenIsawthisstrangebeetleonthewindow.Theroomfiledupwithbeetles-'

Hestopped,mouthopen;athinbluehazesurroundedhim.

Ridculyloweredhishand.

`Wel,wel,'hesaid.`Whataboutthat,MrStibbons?'

Ponderwasscrabblingdesperatelyatthepaperonhisclipboard.

Ì'venoidea!'hesaid.`Hexhasn'tmentionedit!'

TheArchchancelorgrinnedthegrimlittlegrinofsomeonesensingthatthegame,atlast,wasafoot.

`MonoIsland,remember?'saidRidculy,whileDarwinstaredblanklyatnothing.Àgodwithathingaboutbeetles?'

Ì'dratherforget,'Pondershuddered.`But,but...no,itcouldn'tbehim.HowcouldtheGodofEvolutiongetintoRoundworld?'

`SamewaytheAuditorsdid?'saidRidculy.Àlthespacetimecontinuumuumstuffwe'redoing,who'stosaywearen'tleavingafewdoorsajar?Wel,wecan'tletthebarmyoldboyrunaroundthere!YouandRincewind,meetmeintheGreatHalinonehour!'

PonderrememberedtheGodofEvolution,whohadbeensoproudofdevelopingacreatureevenbetterfittedtosurvivethanmankind.Ithadbeenacockroach.

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`Weshouldgorightaway,'hesaid,firmly.

`Why?Wecanmoveintime!'saidRidculy.`Thehour,MrStibbons,isforyoutocomeupwithsomewaytokilAuditors!'

`They'reindestructible,sir!'Àlright-ninetyminutes!'

TWENTY

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THESECRETSOFLIFE

THEDISCWORLDVERSIONOFDARWIN'SvisionmaynotbequitewhatRoundworld'shistoriansofscienceliketotelus,butthetwowilhavebeendoneconvergedontothesametimelineifthewizardsmanagetohavewildefeatedtheAuditors,sowecanconcentrateontheafter-effectsofthatconvergence.InanycasesomefeaturesarecommontobothversionsofDarwinianhistory,includingapes,beetles,andparasiticwasps.Bycontemplatingtheseorganisms,andmanyothers-especialythoseconfoundedbarnacles,ofcourse-Darwinwasledtohisgrandsynthesis.

Today,noareaofbiologyremainsunaffectedbythediscoveryofevolution.

Theevidencethattoday'sspeciesevolvedfromdifferentones,andthatthisprocessstilcontinues,isoverwhelming.Verylittlemodernbiologywouldmakesensewithouttheoverarchingframeworkofevolution.IfDarwinwerereincarnatedtoday,hewouldrecognisemanyofhisideas,perhapsslightlyreformulated,intheconventionalscientificwisdom.Thebigprincipleofnaturalselectionwouldbeoneofthem.Buthewouldalsoobservedebate,perhapsevencontroversy,aboutthisfundamentalpilarofhisthinking.Notwhethernaturalselectionhappens,notwhetheritdrivesmuchofevolution;butwhetheritistheonlydrivingforce.

Hewouldalsofindmanynewlayersofdetailfilingsomeofthegapsinhistheories.ThemostimportantandfarreachingoftheseisDNA,themagicmoleculethatcarriesgeneticìnformation',thephysicalformofheredity.

Darwinwassurethatorganismscouldpassontheircharacteristicstotheiroffspring,buthehadnoideahowthisprocesswasimplemented,andwhatphysicalformittook.Todaywearesofamiliarwiththeroleofgenes,andtheirchemicalstructure,thatanydiscussionofevolutionislikelytofocusmainlyonDNAchemistry.Theroleofnaturalselection,indeedtheroleoforganisms,hasbeendowngraded:themoleculehastriumphed.

Wewanttoconvinceyouthatitwon'tstaythatway.

Evolutionbynaturalselection,thegreatadvancethatDarwinandWalacebroughttopublicattention,isnowadaysconsideredtobeòbvious'byscientists

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ofmostpersuasionsandbymostnonspecialistsoutsidetheUS

BibleBelt.Thisconsensushasarisenpartlybecauseofageneralperceptionthatbiologyisèasy',itisn'tareal,hard-to-understandsciencelikechemistryorphysics,andmostpeoplethinkthattheyknowenoughaboutitbyakindofosmosisfromthegeneralfolkinformation.ThisassumptionshowedupamusinglyattheCheltenhamScienceFestivalin2001,whentheAstronomerRoyalSirMartinReesandtwoothereminentastronomersgavetalkson`LifeOutThere'.

Thetalksweresensibleandinteresting,buttheymadenocontactwithrealmodembiology.Theywerebasedonthekindofbiologythatiscurrentlytaughtinschools,mostofwhichisaboutthirtyyearsoutofdate.Likealmosteverythinginschoolscience,becauseittakesatleastthatlongforideastòtrickledown'fromtheresearchfrontierstotheclassroom.Most`modemmathematics'isatleast150yearsold,sothirty-year-oldbiologyisprettygood.Butit'snotwhatyoushouldbaseyourthinkingonwhendiscussingcutting-edgescience.

Jack,intheaudience,asked:`Whatwouldyouthinkofthreebiologistsdiscussingthephysicsoftheblackholeatthecentreofthegalaxy?'Theaudienceapplauded,seeingthepoint,butittookacoupleofminutesforthescientistsontheplatformtounderstandthesymmetry.Theywerethenascontriteastheycouldbewithoutlosingtheirdignity.

Thiskindofthinghappensalot,becausewearealsofamiliarwithevolutionthatwethinkweunderstandit.Wedevotetherestofthissectiontoareasonableaccountofwhattheaveragepersonthinksaboutevolution.

Itgoeslikethis.

Onceuponatimetherewasalittlewarmpondfulofchemicals,andtheymessedaboutabitandcameupwithanamoeba.Theamoeba'sprogenymultiplied(becauseitwasagoodamoeba)andsomeofthemhadmorebabies(somethingfunnyhere...)andsomehadfewer,andsomeoftheminventedsexandhadamuchbettertimeafterthat.Becausebiologicalcopyingwasn'tverygoodinthosedays,aloftheirprogenyweredifferentfromeachother,carryingvariouscopyingmistakescaledmutations.

Nearlyalmutationswerebad,ontheprinciplethatputtingabuletrandomlythroughapieceofcomplexmachineryisunlikelytoimproveitsperformance,

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butafewweregood.Animalswithgoodmutationshadmanymorebabies,andthosehadthegoodmutationtoo,sotheythrivedandbred.Theirprogenycarriedthegoodmutationintothefuture.However,manymorebadmutationsaccumulated,sonaturalselectionkiledthoseoff.Luckily,anothernewmutationappeared,whichmadeanewcharacterforanewspecies(bettereyes,orswimmingfins,.orscales),whichwasaltogetherbetterandtookover.

Theselaterspecieswerefishes,andoneofthemcameoutonland,growinglegsandlungstodoso.Fromthesefirstamphibiansarosethereptiles,especialythedinosaurs(whiletheunadventurousfisheswerepresumablyjustmessingaboutintheseaformilionsofyears,waitingtobefishandchips).Thereweresomesmal,obscuremammals,whosurvivedbycomingoutatnightandeatingdinosaureggs.

Whenthedinosaursdied,themammalstookovertheplanet,andsomeevolvedintomonkeys,thenapes,thenStoneAgepeople.

Thenevolutionstopped,withamoebasinpondscontenttoremainamoebasandnotwantingtobefishes,fishesnotwantingtobedinosaursbutjustlivingtheirlittlefishylives,thedinosaurswipedoutbyameteorite.

Themonkeysandapes,havingseenwhatitwasliketobeatthepeakofevolution,arenowjustslowlydyingout-exceptinzoos,wheretheyarekepttoshowuswhatourprogenitorsusedtobelike.Humansnowoccupythetopbranchofthetreeoflife:sinceweareperfect,there'snowhereforevolutiontogoanymore,whichiswhyithasstopped.

Ifpressedformoredetail,wedredgeupvariousthingswe'velearned,mostlyfromnewspapers,aboutthingscaledgenes.GenesaremadefromamoleculecaledDNA,whichtakestheformofadoublehelixandcontainsakindofcode.Thecodespecifieshowtomakethatkindoforganism,sohumanDNAcontainstheinformationneededtomakeahuman,whereascatDNAcontainstheinformationforacat,andsoon.

BecausetheDNAhelixisdouble,itcanbesplitapart,andtheseparatepartscaneasilybecopied,whichishowlivingcreaturesreproduce.DNAisthemoleculeoflife,andwithoutit,lifewouldnotexist.MutationsaremistakesintheDNAcopyingprocess-typosinthemessagesoflife.

Yourgenesspecifyeverythingaboutyou-whetheryou'lbehomosexualor

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heterosexual,whatkindsofdiseasesyouwilbesusceptibleto,howlongyouwillive...evenwhatmakeofcaryouwilprefer.Nowthatsciencehassequencedthehumangenome,theDNAsequenceforaperson,weknowaloftheinformationrequiredtomakeahuman,soweknoweverythingthereistoknowabouthowhumanbeingswork.

SomeofuswilbeabletoaddthatmostDNAisn'tintheformofgenes,butisjust`junk'leftoverfromsomedistantpartofourevolutionaryhistory.Thejunkgetsafreerideonthereproductiveroler-coaster,anditsurvivesbecauseitis`selfish'anddoesn'tcarewhathappenstoanythingexceptitself.

Hereendsthefolkviewofevolution.We'veparodieditalittle,butnotbyasmuchasyoumighthope.Thefirstpartisalie-to-childrenaboutnaturalselection;thesecondpartisuncomfortablyclosetòneo-Darwinism',whichformostofthepast50yearshasbeentheacceptedintelectualheirtoTheOrigin.Darwintolduswhathappensinevolution;neo-Darwinismtelsushowithappens,andhowithappensisDNA.

There'snoquestionthatDNAiscentraltolifeonEarth.Butvirtualyeverymonth,newdiscoveriesarebeingmadethatprofoundlychangeourviewofevolution,genetics,andthegrowthanddiversificationoflivingcreatures.

Thisisavasttopic,andthebestwecandohereistoshowyouafewsignificantdiscoveriesandexplainwhytheyaresignificant.

JustasphysicsreplacedNewtonbyEinstein,therehasbeenamajorrevolutioninthebasictenetsofbiology,sowenowhaveadifferent,moreuniversalviewofwhatdrivesevolution.Thèfolk'evolutionaryviewpoint:Ì'vegotthisnewmutation.Ihavebecomeanewkindofcreature.Isitgoingtodomeanygood?'isnotthewaymodernbiologiststhink.

Therearemanythingswrongwithourfolk-evolutionstory.Infactwe'vedeliberatelyconstructeditsothateverysingledetailiswrong.However,it'snotverydifferentfrommanyaccountsinpopularsciencebooksandtelevisionprogrammes.Itassumesthatprimitiveanimalsalivetodayareourancestors,whentheyareourcousins.Itassumesthatwècamefrom'

apes,whenofcoursetheape-likeancestorofmanisthesamecreatureasthemanlikeancestorofmodemapes.Moreseriously,itassumesthatmutationsinthegeneticmaterial,thechangesthatnaturalselectionhastoworkon-indeed,

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toselectamong-arecheckedoutassoonastheyappear,and

labeled`bad'(theorganismdies,oratleastfailstobreed)or`good'(theanimalcontributesitsprogenytothefuture).

Untiltheearly1960s,thatwaswhatmostbiologiststhoughttoo.Indeed,twoveryfamousbiologists,J.B.S.HaldaneandSirRonaldFisher,producedimportantpapersinthemid-1950sespousingjustthatview.Inapopulationofabout1000organisms,theybelieved,onlyaboutathirdofthebreedingpopulationcouldbèlost'tobadgenevariants,orcouldbeoustedbyorganismscarryingbetterversions,withoutthepopulationmovingtowardsextinction.Theycalculatedthatonlyabouttengenescouldhavevariants(knownasàleles')thatwereincreasingordecreasingasproportionsofthepopulation.Perhapstwentygenesmightbechanginginthiswayiftheywerenotverydifferentin`fitness'fromtheregularaleles.

Thispictureofthepopulationimpliedthatalmostalorganismsinagivenspeciesmusthaveprettymuchthesamegeneticmake-up,exceptforafewwhichcarriedthegoodalelescomingin,andwinning,orthebadalelesonthewayout.[1]Theseexceptionsweremutants,famouslyandstupidlyportrayedinmanySFfilms.

However,intheearly1960sRichardLewontin'sgroupexploitedanewwaytoinvestigatethegeneticsofwild(orindeedany)organisms.Theylookedathowmanyversionsofcommonproteinstheycouldfindintheblood,orincelextracts.Iftherewasjustoneversion,theorganismhadreceivedthesamealelefrombothofitsparents:thetechnicaltermhereis`homozygous'.Ifthereweretwo

versions,ithadreceiveddifferentonesfromeachparent,andsowas`heterozygous'.

WhattheyfoundwastotalyincompatiblewiththeFisher-Haldanepicture.

Theyfound,andthishasbeenamplyconfirmedinthousandsofwildpopulationssince,thatinmostorganisms,abouttenpercentof[1]Theymadeexceptionsformanifestlyùnimportant'butverydiversesetsofaleleslikebloodgroups,butinthosecasesitdidn'tseemtomattermuchwhichkindyouhad.

genesareheterozygous.Wenowknow,thankstotheHumanGenomeProject,

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thathumanbeingshaveabout34,000genes.Soabout3400areheterozygous,inanyindividual,insteadofthetenorsopredictedbyHaldaneandFisher.

Furthermore,ifmanydifferentorganismsaresampled,itturnsoutthataboutone-thirdofalgeneshavevariantaleles.Somearerare,butmanyofthemoccurinmorethanonepercentofthepopulation.

Thereisnowaythatthisreal-worldpictureofthegeneticstructureofpopulationscanbereconciledwiththeclassicalviewofpopulationgenetics.Nearlyalcurrentnaturalselectionmustbediscriminatingbetweendifferentcombinationsofancientmutations.It'snotamatterofanewmutationarrivingandtheresultbeingimmediatelysubjectedtoselection:instead,thatmutationmusttypicalyhangaround,formilionsofyears,untileventualyitendsupplayingarolethatmakesenoughofadifferencefornaturalselectiontonotice,andreact.

Withhindsight,itisnowobviousthatalcurrentlyexistingbreedsofdogmusthavebeen'available'-inthesensethatthenecessaryalelesalreadyexisted,somewhereinthepopulation-intheoriginaldomesticatedwolves.Theresimplyhasn'tbeentimetoaccumulatethenecessarymutationspurelyinmoderndogs.Darwinknewabouttheamountofcrypticandovertvariationinpigeons,too.Buthissuccessors,hotonthetrailofthemolecularbasisoflife,forgotaboutwolvesandpigeons.Theyprettymuchforgotaboutcels.DNAwascomplicatedenough:celbiologywasimpossible,andasforunderstandinganorganum...

Lewontin'sdiscoverywasasignificantturningpointinourunderstandingofheredityandevolution.ItwasatleastasradicalasthemuchbetterpublicisedrevolutionthatreplacedNewton'sphysicswithEinstein's,anditwasarguablymoreimportant.Wewilseethatinthelastyearorsotherehasbeenanother,evenmoreradical,revisionofourthinkingaboutthecontrolofcelbiologyanddevelopmentbythegenes.ThewholedogmaaboutDNA,messengerRNA,andproteinshasbeengivenarealitycheck,andscience'sinternalàuditors'haverendereditasarchaicasFisher'spopulationgenetics.

Itiscommonlyassumed-notonlybytheaveragetelevisionproducerofpopsciencehalf-hours,butalsobymostpopularsciencebookauthors-

thatnowweknowaboutDNA,thèsecretoflife',evolutionanditsmechanismsareanopenbook.SoonafterthediscoveryofDNA'sstructureandmechanismof

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replicationbyJamesWatsonandFrancisCrick,inthelate1950s,themedia-andbiologytextbooksatallevels-

werebeginningtorefertoitasthèBlueprintforLife'.Manybooks,culminatingwithDawkins'sTheSelfishGeneinthe1970s,promotedtheviewthatbyknowingaboutthemechanismofheredity,wehadfoundthekeytoaloftheimportantpuzzlesofbiologyandmedicine,especialyevolution.

Therewassoontobeamajortragedy,resultingfromamedicalapplicationofthatmistakenview.Thesedativethalidomidewasincreasinglybeingprescribed,andboughtoverthecounter,totreatnauseaandotherminordiscomfortsoftheearlyweeksofpregnancy.

Onlylaterwasitdiscoveredthatinasmalproportionofcases,thalidomidecouldcauseatypeofbirthdefectknownasphocomelia,inwhicharmsandlegsarereplacedbypartialydevelopedversionsthatresembleaseal'sflippers.

Ittookawhileforanyonetonotice,partlybecausefewgeneralpractitionershadexperienceofphocomeliabefore1957.Infact,veryfewofthemhadeverseenacaseatal,butafter1957theybegantoseetwoorthreeinayear.Asecondreasonwasthatitwasverydifficulttotiethisdefecttoaparticularpotionortreatment:pregnantwomenfamouslytakeagreatvarietyofdietaryadditives,andoftentheydon'trememberpreciselywhatthey'vetaken.Nevertheless,by1961somemedicaldetectiveworkhadtiedthespateofphocomeliadowntothalidomide.

Americandoctorscongratulatedthemselvesonhavingmissedoutonthepathology,becauseFrancesKelsey,amedicalworkerfortheFoodandDrugAdministration,hadexpressedmisgivingsabouttheoriginalanimaltestingofthedrug.Hermisgivingseventualyturnedouttohavebeenunfounded,buttheydidsavemuchsufferingintheUSA.Shenoticedthatthedrughadnotbeentestedonpregnantanimals,becauseatthattimesuchtestswerenotrequired.Everyoneknewthattheembryohasitsownblueprintfordevelopment,quiteseparatefromthatofthemother.However,embryologiststrainedinbiologydepartments,asdistinctfrommedicalembryologists,knewabouttheworkofCecilStockard,EdwardConklin,andotherembryologistsofthe1920s.Theyhadshownthatmanycommonchemicalscouldcausedmonstrousdevelopmentaldefects.Forinstance,lithiumsaltseasilyinducedcyclopia,asinglecentraleye,infishembryos.

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Thesealternativedevelopmentalpaths,inducedbychemicalchanges,havetaughtusalotaboutthebiologicaldevelopmentoforganisms,andhowitiscontroled.

Theyhavealsotaughtusthatanorganism'sdevelopmentisnotrigidlydeterminedbytheDNAofitscels.Environmentalinsultscanpushthecourseofdevelopmentalongpathologicalpaths.Inaddition,thegeneticsoforganisms,particularlywildorganisms,areusualyorganisedsothat`normal'developmenthappensdespiteavarietyofenvironmentalinsults,andevendespitechangesinsomeofthegenes.Thisso-caled`canalised'

developmentisveryimportantforevolutionaryprocesses,becausetherearealwaystemperaturevariations,chemicalimbalancesandassaults,parasiticbacteriaandviruses;thegrowingorganismmustbèbuffered'

againstthesevariations.Itmusthaveversatiledevelopmentalpathstoensurethatthèsame'wel-adaptedcreatureisproduced,whatevertheenvironmentisdoing.Withinreasonablelimits,atanyrate.

Therearemanydevelopmentaltacticsandstrategiesthathelptoaccomplishthis.TheyrangefromsimpletricksliketheHSP90proteintotheveryclevermammaliantrade-off.

HSPstandsfor`heatshockprotein'.Thereareabout30oftheseproteins,andtheyareproducedinmostcelsinresponsetoasudden,notverysevere,changeoftemperature.Adifferentarrayofproteinsisproducedinresponsetoothershocks;thisoneiscaledHSP90becauseofwhereitsitsinamuchlongerlistofcelproteins.HSP90,likemostHSPs,isachaperonin:itsjobistohugotherproteinsduringtheirconstruction,sothatwhenthelonglineofaminoacidsfoldsupitachievesthèright'shape.

HSP90isverygoodatmakingthèright'shape-evenifthegenethatspecifiesthechaperonedproteinhasaccumulatedalotofmutations.Sotheresultingorganismdoesn't`notice'themutations;theproteinis`normal'

andtheorganismlooksandbehavesjustlikeitsancestralform.

However,ifthere'saheatshockorotheremergencyduringdevelopment,HSP90isdivertedfromitsroleaschaperonin,andotherlesspowerfulchaperoninspermitthemutationaldifferencestobeexpressedinmostoftheprogeny.The

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effectthishasonevolutionistokeeptheorganismsmuchthesameuntilthere'sanenvironmentalstress,whensuddenly,inonegeneration,lotsofpreviouslyhidden,buthereditable,variationappears.

Mostbooksthatdescribeevolutionseemtoassumethateverytimethere'samutation,theenvironmentpromptlygetstojudgeitgoodorbad...butonelittletrick,HSP90,whichispresentinmostanimalsandmanybacteria,makesnonsenseofthatassertion.AndfromLewontin'sdiscoverythatathirdofgeneshavecommonvariantsinwildpopulations,andthatalorganismscarrylotsofthem,itisclearthatancientmutationsarecontinualybeingtestedindifferentmoderncombinations,whilethepotentialeffectsofmorerecentmutationsarebeingcloakedbyHSP90

anditsilk.

Thetrickemployedbymammalsismuchmorecomplexandfarreaching.

Theyreorganisedtheirgenes,andgotridofalotofgeneticcomplicationthattheiramphibianancestorsreliedon,byadoptinganewandmorecontroleddevelopmentalstrategy.Mostfrogsandfishes,whoseeggsusualyencountergreatdifferencesandchangesoftemperatureduringeachembryology,ensurethatthèsame'larva,andthenadult,results.

ThinkoffrogspawninafrozenEnglishpond,warmingupto35°Cduringthedaywhilethedelicateearlydevelopmentproceeds;thenthelittlehatchlingtadpoleshavetoendurethesetemperaturechanges.Nowthinkofthefrogsthatsofewofthetadpolesbecome.

Mostchemicalreactions,includingmanybiochemicalones,happenatdifferentratesifthetemperatureisdifferent.Youonlygetafrogifalthedifferentdevelopmentalprocessesfittogethereffectively,andtimingiscrucial.Sohowdoesfrogdevelopmentworkatal,giventhattheenvironmentischangingsoquicklyandrepeatedly?

Theansweristhatthefroggenomècontains'manydifferentcontingencyplans,formanydifferentenvironmentalscenarios.Therearemanydifferentversionsofeachoftheenzymesandotherproteinsthatfrogdevelopmentrequires.Alofthemareputintotheeggwhileitisinmotherfrog'sovary.

Thereareperhapsasmanyastenversionsofeach,appropriatetodifferent

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temperatures(fastenzymesforlowtemperatures,sluggishonesforhighertemperatures,tokeepthedurationofdevelopmentmuchthesame)[1],andtheyhavèlabels'onthepackagesthatmakethem,sotheembryocanchoosewhichonetouseaccordingtoitstemperature.

Animalswhosedevelopmentmustbebufferedinthiswayusealotoftheirgeneticprogrammetosetupcontingencyplansformanyothervariables,inadditiontotemperature.

Themammalscleverlyavoidedalofthisfaffingaround,bymakingtheirfemalesthermostaticalycontroled-'warm-blooded'.What[1]That'sveryimportantforafewspecies.Zebra-fisheggsinthewildmusthatchinjustunder72hours,becausethey'relaidjustbeforedawnandmusthidebeforethethirddawnwhenpredatorscouldseethem.

countsisnotthewarmthoftheblood,butthesystemthatmaintainsitataconstanttemperature.Thebeautifulycontroleduteruskeepsalkindsofothervariablesawayfromtheembryos,too,frompoisonstopredators.Itprobably`costs'muchlessinDNAprogrammingtoadoptthisstrategy,too.

Thistrick,evolvedbythemammals,carriesanimportantmessage.ToaskhowmuchinformationpassesacrossthegenerationsintheDNAblueprint,astextbooksandsophisticatedresearchmanualsoftendo,istomissthepoint.Howthegenesandproteinsareusedisfarmoreimportant,andfarmoreinteresting,thanhowmanygenesorproteinsthereareinagivencreature.Lungfishesandsomesalamanders,evensomeamoebas,havemorethanfiftytimesasmuchDNAaswemammalsdo.Whatdoesthissayabouthowcomplexthesecreaturesare,comparedtous?

Absolutelynothing.

TrickslikeHSP90,andstrategieslikewarm-bloodednessandkeepingdevelopmentinsidethemother,meanthatbean-countingofDNAìnformation'isbesidethepoint.WhatcountsiswhattheDNAmeans,nothowbigitis.Andmeaningdependsoncontext,aswelascontent:youcan'tregulatethetemperatureofauterusunlessyourcontext(thatis,mother)providesone.

Thesimple-minded`mutation'viewpoint,aliedtotrendyinterpretationsofDNAfunctionintermsofìnformationtheory',isoftenaliedwithignoranceofbiologyinotherareas.Oneexampleisradiationbiologyandsimpleecologyasseenby

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`conservationactivists'.Someofthesevolunteersfoundfive-leggedfrogsandother'monsters'downwindoftheChernobylsite,yearsafterthenuclearaccidentbutwhileradiationlevelswerestilnoticeablyhigh.Theyclaimedthatthemonstersweremutants,causedbytheradiation.Otherworkers,however,thenfoundjustasmanysupposedmutantsupwindofthereactorsite.

Itturnedoutthatthebestexplanationhadnothingtodowithmutantfrogs.Itwastheabsenceoftheirusualpredators,owlsandhawksandsnakes,becausethereweresomanyhumanstrudgingabout.

RanapalustristadpolesfromChernobylproducednomoreofthesepathologiesthandidotherfrogspawnsamplesfrompondssometensofkilometresawaythathadnotbeensubjectedtoradiation,whenahighpercentageofbothwasalowedtosurvive.Usualy,inBritishRanatemporariafrogs,itisverydifficulttoachievetenpercentnormaladults,orevenonesthatareviableinthelaboratory,buttheydon'tproduceextralimbsaspalustrisdoes.Itisnormalythecase,ofcourse,thatafemalefrog'slifetimeproductionofsome10,000eggsresultsinafewhighlyselected,andthereforènormal',survivors,andonaveragejusttwobreeders.Butconservationistsdon'tlikethinkingaboutthisreproductivearithmetic,withalthosedeaths.

Hereisanotherissue,againchosenfromthethalidomideliterature,thatdemonstrateshowtalkofLamarckism,orof`mutations',missesthepoint.

Someofthechildrenaffectedbythalidomidehavemarriedeachother,andseveralofthesepairingshaveproducedphocomelicchildren.Theobviousdeduction,fromthefolk-DNApointofview,isthattheDNAofthefirstgenerationmusthavebeenaltered,sothatitproducedthesameeffectinthenextgeneration.Infact,thiseffectlooks,atfirstglance,likeLamarckism:theinheritanceofacquiredcharacters.Indeed,itseemsaclassicdemonstrationofsuchinheritance,asconvincingasifcuttingoffterriers'tailsresultedinpuppiesbeingbornwithshorttails.However,itisactualyalessoninnotattemptingtoexplainthingsàtfirstglance',liketheconservationistsdidwiththeabnormalfrogs.

Itisverytemptingtodojustthat,whentheideaofheredityinyourmindisthatonegeneleadstoonecharacter,soifyou'vegotthecharacteryou'vegotthegene,andviceversa.Figuresfromtheepidemiologicalliteraturesuggestthatinthespaceofafewyearseithersideof1960,about4

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milionwomentookthalidomideatthecriticaltimeduringgestation.Ofthose,about15,000-18,000foetusesweredamaged;12,000cametobirthwithdefects,andabout8,000survivedtheirfirstyear.Thatistosay,thenaturalcourseofdevelopmentselectedjust1in500whoshowedadverseeffects.Theproportionofchildrenbornwithnodetectabledefectwasmuch,muchhigher.Andthatfactchangesourviewofthelikelyreasonforthechildrenoftwothalidomideparentstosufferfromphocomelia,forthefolowingreason.

ConradWaddingtondemonstratedaphenomenoncaled`geneticassimilation'.Hestartedwithageneticalydiversepopulationofwildfruitflies,andfoundthataboutonein15,000oftheirpupae,whenwarmed,producedaflywithnocrossveininitswing.These'crossveinless'flieslookedjustlikesomeveryraremutantfliesthatturnedupoccasionalyinthewild,justasoccasionalgeneticalyphocomelicchildrenturnedupbeforethalidomide.Bybreedingfromthefliesthatrespondedtothetreatment,Waddingtonselectedforalowerandlowerthresholdofresponse.Inafewtensofgenerations,hehadselectedfliesthatbredtrueforthecrossveinlesstrait,exhibitingitregularlywithoutanyonewarmingthepupae.ThismaylooklikeLamarckianinheritance,butit'snot.It'sgeneticassimilation.Theexperimentswereselectingfliesthathadnocrossveinatlowerandlowertemperaturethresholds.Eventualy,theyselectedfliesthathadnocrossveinat`normal'temperatures.

Similarly,geneticassimilationprovidesamuchbetterexplanationthanLamarckismforthephocomelicchildrenofthalidomidemodifiedparents.

Wehaveselected,fromsome4milionfoetuses,thosethatrespondtothalidomidewithphocomelia.Itisnotsurprisingthatwhentheymarryeachother,theyproduceafewprogenywhosethresholdisverylow-belowzeroinfact.Theyaresoliabletoproducephocomeliathattheydoitwithoutthalidomide,justasWaddington'sfliescametoproducecrossveinlessnesswithoutwarmingthepupae.

OneofthethingsthatrealyworriedDarwinwastheexistenceofparasiticwasps-afactthathasinfluencedourDiscworldtale,buthasgoneunremarkeduntilnowinthescientificcommentaries.Parasiticwaspslaytheireggsinotherinsects'larvae,sothatasthewaspeggsgrowintowasplarvae,theyeattheirhosts.Darwincouldseehowthismighthavehappenedonevolutionarygrounds,butitseemedtohimtoberatherimmoral.Hewasawarethatwaspsdon'thaveasenseofmorality,buthesawitassomekindofflawonthepartofthewasps'

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creator.IfGoddesignedeachspeciesonEarth,foraspecialpurpose-whichiswhatmostpeoplebelievedatthetime-thenGodhaddeliberatelydesignedparasiticwasps,whosepurposewastoeatotherspeciesofinsect,alsodesignedbyGod.Tobesoeaten,presumably.

Darwinwasfascinatedbysuchwasps,eversincehefirstencounteredtheminBotafogoBay,Brazil.Heeventualysatisfiedhimself-thoughnothissuccessors-thatGodhadfounditnecessarytopermittheexistenceandevolutionofparasiticwaspsinordertogettohumans.ThisiswhatthequoteattheendofChapter10aludesto.Thatparticularexplanationhasfalenoutoffavouramongbiologists,alongwithaltheistinterpretations.

Parasiticwaspsexistbecausethereissomethingforthemtoparasitise-

sowhynot?Indeed,parasiticwaspsplayamajorroleincontrolingmanyotherinsectpopulations:nearlyone-thirdofaloftheinsectpopulationsthathumansliketolabel`pests'arekeptatbayinthismanner.Maybetheywerecreatedinorderforhumanstobepossible...Atanyrate,thewaspsthatsopuzzledDarwinstilhavemuchtotelus,andthelatestdiscoveryaboutthemthreatenstooverturnseveralcherishedbeliefs.

Strictly,thediscoveryisnotsomuchaboutthewasps,asaboutsomevirusesthatinfectthem...oraresymbioticwiththem.Theyarecaledpolydnaviruses.

Whenmotherwaspinjectshereggsintosomeunsuspectinglarva,suchasacaterpilar,shealsoinjectsasoliddoseofviruses,amongthemsaidpolydnaviruses.Thecaterpilarnotonlygetsaparasite,itgetsaninfection.

Thevirus'sgenesproduceproteinsthatinterferewiththecaterpilar'sownimmunesystem,stoppingitreactingtotheparasiteand,perhaps,rejectingit.Sothewasplarvaemunchmerrilyawayonthecaterpilar,andinthefulnessoftimetheydevelopintoadultwasps.

Now,anyself-respectingadultparasiticwaspobviouslyneedsitsowncomplementofpolydnaviruses.Wheredoesitgetthem?Fromthecaterpilarthatitfedon.Anditgetsthem(justasmotherdid)notasaseparateinfectiveòrganism',butaswhatiscaledaprovirus:aDNAsequencethathasbeenintegratedintothewasp'sowngenome.

Manygenomes,probablymostifnotal,includevariousbitsofvirusesinthis

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way.Ourowncertainlydoes.TransportofDNAbyvirusesseemstohavebeenanimportantfeatureofevolution.

In2004ateamheadedbyEricEspagneworkedouttheDNAsequenceofapolydnavirus-asonedoes-andwhattheyfoundwasdramaticalydifferentfromwhatanyonehadexpected.Typicalvirusgenomesareverydifferentfromthoseof'eukaryotes'-organismswhosecelshaveanucleus,whichincludesmostmulti-celularcreaturesandmanysingle-celedones,butnotbacteria.TheDNAsequencesofmosteukaryotegenesconsistofèxons',shortsequencesthatcolectivelycodeforproteins,separatedbyothersequencescaledintrons,whichgetsnippedoutwhenthecodeisturnedintotheappropriateprotein.Viralgenesarerelativelysimple,andtypicalytheydonotcontainintrons.Theyconsistofconnectedcodesequencesthatspecifyproteins.-Thisparticularpolydnavirusgenome,incontrast,doescontainintrons,quitealotofthem.Thegenomeiscomplex,andlooksmuchmorelikeaeukaryotegenomethanavirusgenome.Theauthorsconcludethatpolydnavirusgenomesconstitutèbiologicalweaponsdirectedbythewaspsagainsttheirhosts'.Sotheylookmoreliketheenemy'sgenomethanthatofanordinaryvirus.

Numerousexamples,oldandnew,disproveeveryaspectofthefolkversionofevolutionandDNA.Weendwithonethatlooksespecialyimportant,discoveredveryrecently,andwhosesignificanceisjustbecomingseriouslyapparenttothebiologicalcommunity.ItisprobablythemostsevereshockthatcelbiologyhasreceivedsincethediscoveryofDNAandthewonderful`centraldogma':DNAspecifiesmessenger-RNAwhichspecifiesproteins.Thediscoverywasnotmadethroughsomebig,highlypublicisedresearchprogrammelikethehumangenomeproject.Itwasmadebysomeonewhowonderedwhyhispetuniashadgonestripy.

Whenaltheworldischasing`the'humangenome,it'snoteasytogetresearchgrantstoworkonstripypetunias.Butwhatthepetuniasrevealedisprobablygoingtobefarmoreimportantformedicinethantheentirehumangenomeproject.

Becauseproteinsarethestructureoflivingcreatures,andbecauseasenzymestheycontroltheprocessesoflife,ithasseemedobviousthatDNAcontrolslife,thatwecan`map'DNAcodeontoaltheimportantlivingfunctions.Wecouldassignafunctiontoeachprotein,sowecouldassumethattheDNAthatcodedforthatproteinwasultimatelyorfundamentalyresponsibleforthe

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correspondingfunction.Dawkins'searlybooksreinforcedtheideaofonegene,oneprotein,onefunction(althoughhecarefulywarnedhisreadersthathedidn'twanttogivethatimpression),andthisencouragedsuchmediaexaggerationsascalingthehumangenometheBookofLife.Andthèselfishgene'imagemadeitentirelycrediblethathugestretchesofthegenomewerepresentforsolelyselfishreasons-thatis,fornoreasonrelatedtotheorganismconcerned.

Biologistsemployed-assomanynoware-inthebiotechnologyindustriesservingagriculture,pharmacy,medicine,evensomeengineeringprojects(wedon'tmeanjust`geneticengineering'butmakingbettermotoroils),alsubscribetothecentraldogma,withafewminormodificationsandexceptions.AlofthemhavebeeninformedthatnearlyaloftheDNAinthehumangenomeis`junk',notcodingforproteins,andthatalthoughsomeofitmaybeimportantfordevelopmentalprocessesorforcontrolingsomeofthèreal'genes,theyrealydon'tneedtoworryaboutit.

Admittedly,quitealotofjunkDNAseemstobetranscribedintoRNA,butthesearejustshortlengthsthatsitaboutbrieflyinthecelfluidsanddon'tneedtobeconsideredwhenyou'redoingimportantproteinmakingthingswiththerealgenes.RecalthattheDNAsequencesofrealgenesconsistofamosaicofèxons'whichcodeforproteins,separatedbyothersequencescaledintrons.TheintronshavetobecutoutoftheRNAcopiestogetthèreal'protein-codingsequences,caledmessenger-RNAs,whichlaceintoribosomesliketapesintoatapeplayer.Messenger-RNAsdeterminewhatproteinsgetmade,andtheyhavesequencesontheirendsthatlabelthemformakingmanycopiesofaproteinorfordestructionafteronlyacoupleofproteinmolecules.

Nobodyworriedmuchaboutthosesnipped-outintrons,justbitsofRNAdriftingaimlesslyaroundintheceltiltheygotbrokenupbyenzymes.Now,theydoworry.WritingintheOctober2004ScientificAmerican,JohnMattickreportsthat

Thecentraldogmaiswoefulyincompletefordescribingthemolecularbiologyofeukaryotes.Proteinsdoplayaroleintheregulationofeukaryoticgeneexpression,yetahidden,paralelregulatorysystemconsistingofRNAthatactsdirectlyonDNA,RNAsandproteinsisalsoatwork.ThisoverlookedRNAsignalingnetworkmaybewhatalowshumans,forexample,toachievestructuralcomplexityfarbeyondanythingseenintheunicelularworld.

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Petuniasmadethatclear.In1990RichardJorgensenandcoleaguesweretryingtobreednewvarietiesofpetunias,withmoreinteresting,brightercolours.Anobviousapproachwastoengineerintothepetuniagenomesomeextracopiesofthegenethatcodedforanenzymeinvolvedintheproductionofpigment.Moreenzyme,morepigment,right?

Wrong.

Lesspigment?

No,notexactly.Whatpreviouslywasauniformlycolouredpetalbecamestripy.Insomeplacesthepigmentwasbeingproduced,elsewhereitwasn't.Thiseffectwassosurprisingthatplantbiologiststriedtofindoutexactlywhyitwashappening.Andwhattheyfoundwas`RNAinterference'.

CertainRNAsequencescanshutdownagene,preventitmakingprotein.

Ithappensinmanyotherorganisms,too.Infact,itisextremelywidespread.Anditsuggestssomethingextraordinarilyimportant.

Thebigquestioninthisarea,askedmanytimesandlargelyignored,hasalwaysbeen:ifintrons(whichoccupyalbutone-twentiethofatypicalprotein-codinggene)havenobiologicalfunction,whyaretheythere?Itiseasytodismissthemasrelicsofsomedimevolutionarypast,nolongeruseful,lyingaroundbecausenaturalselectioncan'tgetridofthingsthatareharmless.Evenso,wecanstilwonderwhetherintronsarepresentbecausetheydohavesomeusefulfunction,onethatwehaven'tyetworkedout.Andit'sstartingtolookasifthatmaybethecase.

Forastart,intronsarenotthatancient.Itnowseemsthattheybecameincorporatedintothehumangenomerelativelyrecently.TheyareprobablyrelatedtomobilegeneticelementsknownasgroupIintrons,whichareàparasitic'formofDNAthatcaninvadehostgenomesandthenremovethemselveswhentheDNAisexpressedasRNA.Moreover,theynowseemtohavearoleas'signals'intheregulationofgeneticprocesses.Anintronmayberelativelyshort,comparedtothelongprotein-codingsequencesthatarisewhentheintronsaresnippedout,butashortsignalhasadvantagesandcandoquitealot.Ineffect,theintronsmaybegenetic'txtmsgs'inthemobilephoneoflife.Short,cheap,andveryeffective.AnRNA-based`code',runningparaleltotheDNAdoublehelix,canaffecttheactivityofthecelverydirectly.AnRNA

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sequencecanactasaveryspecific,wel-definedsignal,directingRNAmoleculestotheirtargetsinRNAorDNA.

Theevidencefortheexistenceofsuchasignalingsystemisreasonable,butnotyetundeniable.Ifsuchasystemdoesexist,itclearlyhasthepotentialtoresolvemanybiologicalmysteries.Abigpuzzleaboutthehumangenomeisthatits34,000genesmanagetoencodeover100,000

proteins.Clearlyònegeneoneprotein'doesn'twork.AhiddenRNAsignalingsystemcouldmakeonegeneproduceseveralproteins,dependingonwhattheaccompanyingRNAsignalspecified.Anotherpuzzleisthecomplexityofeukaryotes,especialytheCambrianexplosionof525milionyearsago,whentherangeofterrestrialbody-planssuddenlydiversifiedoutofalrecognition;indeed,wasmorediversethanitisnow.

PerhapsthehypotheticalRNAsignalingsystemstartedtotakeoffatthattime.Andit'swidelyknownthatthehumanandchimpanzeegenomesaresurprisinglysimilar(thoughthedegreeofsimilarityseemsnottobe98percentaswidelyquotedevenafewyearsago).IfourRNAsignalsaresignificantlydifferent,thatwouldbeonewaytoexplainwhyhumansdon'tgreatlyresemblechimps.

Atanyrate,itverymuchlooksasifalthat`junk'DNAinyourgenomeisnotjunkatal.Onthecontrary,itmaybeacrucialpartofwhatmakesyouhuman.

Thislessonisdrivenhomebythosebusinessassociatesofparasiticwasps,thesymbioticpolydnaviruses,sneakilyburiedinsidethewasps'

ownDNA.Thereisamessagethereabouthumanevolution,andit'saverystrangeone.

Genome-sequencingmayhavebeenoversoldastheanswertohumandiseases,butit'sverygoodbasicscience.TheactivitiesofthesequencershaverevealedthatwaspsarenottheonlyorganismstohavebitsofviralDNAhangingaroundintheirgenomes.Infact,mostcreaturesdo,humansincluded.Thehumangenomeevencontainsonecompleteviralgenome,andonlyone,caledERV-3(EndogenousRetroVirus).Thismayseemanevolutionaryoddity,abitof`junkDNA'thatrealyisjunk...but,actualy,withoutitnoneofuswouldbehere.Itplaystheabsolutelycrucialroleofpreventingrejectionofthefoetusbythemother.Mother'simmunesystemòughtto'recognisethetissueofadevelopingbabyas`foreign',andtriggeractionsthatwilgetridofit.Byòughtto'herewe

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meanthatthisiswhattheimmunesystemnormalydoesfortissuethatisnotthemother'sown.

Apparently,theERV-3proteincloselyresemblesanotheronecaledp15E,whichispartofawidespreaddefencesystemusedbyvirusestostoptheirhostskilingthemoff.Thep15Eproteinstopslymphocytes,akeytypeofcelintheimmunesystem,fromrespondingtoantigens,moleculesthatrevealthevirus'sforeignnature.Atsomestageduringmammalianevolution,thisdefencesystemwasstolenfromthevirusesandusedtostopthefemaleplacentarespondingtoantigensthatrevealtheforeignnatureofthefoetus'sfather.Perhapsontheprincipleofbeinghungforasheepaswelasforalamb,thehumangenomedecidedtogothewholehog[1]andstealtheentireretroviralgenome.

Whenevolutioncarriedoutthetheft,however,itdidnotjustdumpitsbootyintothehumanDNAsequenceunchanged.Itthrewinacoupleofintrons,too,splittingERV-3intoseveralseparatepieces.It'scomplete,butnotconnected.Nomatter:enzymescaneasilysnipouttheintronswhenthatbitofDNAisturnedintoprotein.Butnooneknowswhytheintronsarethere.

Theymightbeanaccidentalintrusion.Or-pursuingtheRNAinterferenceidea-theymightbemuchmoresignificant.Thoseintronsmightbeanimportantpartofthegeneticregulatorysystem,`textmessages'thatlettheplacentauseERV-3withoutrunningtheriskofsettingthecorrespondingvirusloose.

Atanyrate,whatevertheintronsarefor,warm-bloodednessisnottheonlytrickthatmammalianevolutionmanagedtofindandexploit.

[1]Sorryabouttheproliferationofbarnyardmetaphors.

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Italsoindulgedinwholesaletheftofavirus'sgenome,tostopmother'simmunesystembootingoutbabybecauseit`smeled'offather.AndwealsogetanotherlessonthatDNAisn'tselfish.ERV-3ispresentinthehumangenome,butnotbecauseit'sabitofjunkthatgetscopiedalongwitheverythingelseandhasremainedbecauseitdoesnoharm.It'stherebecause,inaveryrealsense,

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humanscouldnotsurvive-couldnotevenreproduce-withoutit.

TWENTY-ONE

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NOUGATSURPRISE

THEACTIVITYINTHEGREATHALLwasslowingdownnow.Alalongtherainbowlinesoftime,thenodeswereclosed.Orshut,ordenoded,Rincewindthought.Whateveryoudidwithnodes,anyway.

Therewasalittlecheerasthelastglowingwizardsymbolfadedaway,andaroarfromoutsideasthreewizardsandalotoftentacleslandedinthefountain.Rincewindhadbeensurprisedaboutthat,andthendismayed.

Sinceitdidnothavehisnameonit,thismeantthatRidculyhadsomethingworseinmind.

`LookslikeI'mnotneedednow,'hesaidhopefuly,justincase.

'Haha,professor,whatacardyouareandnomistake,'saidthelobsternexttohim.`TheArchchancelorwasverydefinitethatwewastokeepyouherenomatterwhatyousaid.'

`ButIwasn'trunningaway!'

`No,youwasonlyinspectingthewalwiththeloosebricksinit,'saidthelobster.[1]`Wequiteunderstand.Luckyforyouwecaughtyoubeforeyoudroppedoverintothealey,eh?Could'vedoneyerselfamischief.'

Rincewindsighed.Thelobsterswerealwayshardtooutrun.Theyhuntedinpacks,appearedtoshareacommonbrain,andmanyyears[1]TheUniversity'sproctorswereknownaslobstersbecausetheywentveryredwhenhotandhadagripthatwasextremelyhardtoshakeoff.

Theyweregeneralyex-armysergeants,haddepthsofcynicismunplumbablebyanyline,andwerefueledbybeer.

ofharryingerringstudentshadgiventhemamalignantstreetcunningthatvergedonthesupernatural.

Someoftheseniorwizardssweptin...TherewasanargumentgoingonbetweenRidculyandtheDean.

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Ìdon'tseewhyIshouldn't.'

`Becauseyougettooexcitedinthepresenceofcombat,Dean.Yourunaroundmakingsily"hut,hut"noises,'saidRidculy.`Rememberwhywehadtostopthosepaintbalafternoons?Youdidn'tseemtobeabletogetthehangoftheterm"peopleonmyside".'

`Yes,butthisis-'

ÌttookusaweektogettheSeniorWranglerlookinghalfwaysuitableforpolitecompany-Ah,Rincewind.Stilwithus,Isee.Goodman.Verywel,MrStibbons:report!'

Pondercoughed.

`Hexconfirmsthat,er,thatourrecentactivitiesmayhaveleftcamiloopsbetweenourwordandRoundworld,Sir.Thatistosay,residualconnectionsthatmaybeuseddeliberatelyorinadvertentlyfromeitherside.

Magicdoors,infact,driftingwithoutanchor.Thesewilevaporatewithinamatterofdays.Um...'

Ìdon'twanttohear"um",MrStibbons."Um"isnotawordweentertainhere.'

`Wel,thefactisthatsincethecamiloopsarespreadovercenturies,theAuditorsmayverywelhavebeeninRoundworldforsometime.Wehavenowayofknowingforhowlong.Hex,um,sorry,doesreportsomecircumstantialevidencethathumansaredimlyawareoftheirmalignmeddling,albeitataverymundanelevelasevidencedbythefindingsofaresearchercaledMurphy.Roundworldwouldbedifficultforthem.Theywouldbebewildered.Thingswouldnotworkthewaytheyexpect.Theyarenotflexiblethinkers.'

`TheywereabletomessaroundwithMrDarwin'svoyage!'

`Bydoinglotsofsmalandratherstupidthingsatgreateffort,sir.Theydon'treactweltoadversity.Theygetpetulant.FromwhatProfessorRincewindtelsus,manyhundredsofthemhavetocombinetoperformevenasimplephysicalaction.'

Hestoodbackandindicatedsomeitemslaidoutonadiningtable.

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`ThereissomeevidencethatAuditors,beingembodimentsofphysicallaws,findithardtodealwithnonsensicalorcontradictoryinstructions.

Therefore,Ihavepreparedthese.'

Heflourishedsomethingthatlookedlikeatable-tennisbat.Onitwereprintedthewords:`DoNotReadThisSign.'

`Thatworks,doesit?'saidtheDean,doubtfuly.

Ìt'ssaidtoputtheirmindsintoafuguestate,Dean.Theyfeelconfusedandalone,andevaporateinstantly.Beingalonemeanshavingasenseofself,andanyAuditorthatdevelopsanindividualityissaidtodieinstantly.'

Àndthecatapultbows?'Whataretheyfor?'saidtheArchchancelor,slappingtheDean'shandoffoneofthem.

Ìnaddition,itispossiblethatacolectiveofAuditorswithsufficientpresenceinthematerialworldmaydevelopcrudephysicalsenses,andsoIhaveadaptedsomecatapultbowstofireamixtureofintense,er,stimuli.

Oldreferencessuggestchili,essenceofWahoonieorBlissberryblossoms,butmodernthinkinginclinestoHiggs&MeakinsLuxuryAssortment.'

`Chocolate?'saidRidculy.

`Theydon'tlikeit,sir.'

`Butthosethingscanliveinemptyspaceandinsidestars,man!'

`Wherechocolateissignificantlyabsent,sir,'saidPonder,patiently.`Theykeepawayfromit.Also,itcomeshandilypacked.Theyparticularlydon'tliketheStrawberryWhirl.'

Ridculypickedupabow,pointeditatawizard,andfired.Therewasadistantòw!'

'Hmm.Spreadsnicelyonimpact,'hesaid.`Weldone,MrStibbons.I'mimpressed.Youareincharge.'

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TheDeanbridledatthis.Ìprotest!IamtheDean,whenalissaidanddone!'

Òh,alright,Dean,youcancome!But,andIwanttomakemyselfabsolutelyclear,youarenottopointanythingatanythingunlessIgiveyouaclearinstruction,understood?'

`Yes,Mustrum,'saidtheDeanmeekly.

`Furthermore,youwilnot,atanypoint,waveyourweaponintheairandshout"chocandload".Isthatclear?IsaythatbecauseIcanpracticalyseethesilywordsforminginyourhead!'

`That'savilecalumny!'theDeanshouted.

Ìhopeso.Stibbons,waitherewiththeproctorsandseenoharmcomestoMrDarwin.Hex,youknowwheretosendus.Invisibly,ifyouplease!'

WhileCharlesDarwinwassittinginabluehazeinUnseenUniversity,aslightlyyoungerCharlesDarwinwasstaringoutattherain,notingidlythattherainsoundedalittlelikewhispering.

Adrawbackofinvisibilityisthatnoonecanseeyou;itisinfactthemaindrawbackifthereisagroupofyou-

`-thatwasmyfoot!'

`Whoisthat?'

`Lookwhereyou'regoing!'

Àndwhathelpwilthatbe?'

`Keepitdown,youfelows!He'lhearyou!'

Atwhichpoint,thewalinthecornerdissolvedandbriliantlightshonethrough.Beetlesofalsizesandcolourspouredintothestudyinashimmeringtorrent.

Afigurethatthewizardsrecognisedsteppedthoughtheholeandlookedaroundhimwithanairofamiablebewilderment.Hehadaslightlylopsidedcircletofleavesonhishead,andglowedwiththelightofdeity.

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`MrDarwin?'hesaid,asthefigureinthecornerturnedandstared.Ì

understandyouarestudyingevolutionandarecurrentlyperplexed?''Lookbehindhim!'Ridculywhispered.

Theunseenwizardsstaredintotheflickeringhole.Therewassand,andseainthedistance,asuggestionofmovingshadows...

Àfterme,'Ridculyhissed,asanastonishedDarwindroppedtohisknees.

`Let'sgetthem...'

Thewizardspouredthroughthecamiloop,whilebehindthemanelderlyvoicesaid:Òfcourse,selectionis,ahaha,anythingbutnatural.Take,forexample,aspeciesofparasiticwasp...'

Thesandboiled.Sometimeshandfulsofitfountainedintotheair.Oneinvisiblepersoncanmovewithstealthandspeed.Halfadozeninvisiblepeopleareanaccidentwaitingtohappenagainandagain.

`Thisisnotbeingourfinesthour,'saidthevoiceofRidculy.ÈverytimeIstarttostandupsomeoneelsetreadsonme!Can'tHexsortthisout?'

`We'rebackintherealworld,'saidtheinvisibleDean.`Hex'spowerisn'tsostronghere.It'ltakehimsometimetofindus.Wouldyoumindgettingoffmyleg.Thankyousoverymuch.'

`That'snotme,I'moverhere.Idon'tseewhyit'saproblem.Wewereinanotherworld,afteral!'

`RoundworldisrightinsidetheHighEnergyMagicBuilding,'saidtheLecturerinRecentRunes.`We'rethousandsofmilesway,Isuspect.CouldIpossiblysuggestwealendeavourtocrawlawayindifferentdirections?Ifyou,Dean,headforthatlittlebushwiththeredflowers,andRincewind-

where'sRincewind?'

`Here,'saidamuffledvoicefromunderthesand.

`Sorry...youheadforthatrockthere...'

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Bydegrees,withonlytheoccasionalcurse,thewizardswereabletogettotheirunseenfeet.

`ThisisMonoIsland,Irecognisethatmountain,'saidRidculy.`Lookoutfor-'

`Whydidn'twejustbophimonthehead?'saidtheDean.`Justataponthenoggin?Thenwecouldhavedraggedhimbackhere,endofproblem.'

`Butit'squantum,'saidRincewind.`Wehavetodealwithwhat'shappened.

Ifwestopithappeningbeforeithappens,theotherthingswe've...'hehesitated.`Look,it'squantum.Believeme,I'dpreferittheotherway.'

Ànyway,youcan'tjustbopgodsonthehead,'saidRidculy,nowafaintoutlineagainstthedistantocean.Ìtdoesn'tusualyworkanditcausestalk.

Theothergodswouldbeboundtohearaboutit,too.'

`So?Noneofthemlikehim.Theyexiledhimhereafterheinventedthehermitelephant!'saidtheDean,whowasalsofadingintoview.

Ìt'sthelookofthething,'saidRidculy.`Theydon'twanttoencouragedeicide.Besides,lookupthere...'

Òhdear,'saidRincewind.Àuditors...'

Agreycloudwasrolingdownthemountain.Asitneared,itcontracteduponitself,growingdarker.

`They'velearnedthings,'saidRidculy.`They'veneverdonethatbefore.Oh,wel...Rincewind,firstlineofdefence,ifyouplease.Andhurry!'

Rincewind,who'dalwaysoperatedontheassumptionthatifyoucarriedaweaponyouweregivingtheenemysomethingextratohityouwith,heldupaplacard.Itread:GOAWAY.

`Stibbonssaysitshouldwork,'saidRidculy,uncertainly.

TheAuditorsdrewcloser,merginguntil,now,onlyhalfadozenwereleft.

Theyweredark,andfulofmenace.

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Àh,theyprobablyaren'tthereadingsort,then,'saidRidculy.`Gentlemen,it'schocolatetime...'

Ithadtobesaidthatthemostofthewizardswerenotnaturalaimers.Aspelwentwhereyouwantedittogo.Youjusthadtowaveinthegeneraldirection.They'dneverlearnedtobeseriousaboutpointing.

Someshotswenthome.WhenseveralhitanAuditoritletoutathinscreamandbegantobreakupintoitscomponentrobes,whichthenevaporated.

Butone,slightlylargerthantheothers,ziggedandzaggedthroughthetumblingchocolates.Auditorsdidlearnhere...andthewizardswererunningoutofchocolate.

`Holdit,'saidtheDean,pointinghisbow.

Theshapestopped.

Àh,'saidtheDean,happily.'Ha,Iexpectyouarewondering,eh,Iexpectyouarewondering,indeed,ifIhaveanychocolateleft?AndasamatteroffactI'mno-'

`No,'saidtheAuditor,driftingforward.

`What?Pardon?'

Ìamnotwonderingifyouhaveanychocolateleft,'saidthedarkapparition.`Youhavenoneleft.TheHiggs&MeakinsLuxuryAssortmentcomprisestwoeachof:WalnutWhips,StrawberryWhirls,CaramelBars,VioletCreams,CoffeeCreams,CherryWhipsandWalnutClustersandoneeachofAlmondDelight,VanilaCup,PeachCream,CoffeeFondueandLemonExtravaganza.'

TheDeansmiledthesmileofamanwhoseHogswatcheshadcomealatonce.Heraisedthebow.

`ThenbesokindastosaygooddaytotheNougatSurprise!'

Therewasatwang.Thesweetflew.ForamomenttheAuditorwavered,andthewizardsheldtheirbreath.Then,withtheslightestofwhimpers,itfadedintonothing.

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ÈveryoneforgetstheNougatSurprise,'saidtheDean,turningtotheotherwizards.Ìsupposeit'sbecauseit'ssoirredeemablyawful.'

Therewasnothingbutthesoundoftheseaforafewseconds.Then:Èr...weldone,Dean,'saidRidculy.

`Thankyou,Archchancelor.'

Àlittletooshowy,nevertheless.Imean,youdidn'thavetochattothething.'

Ìwasn'tinfactsureifIhadusedthenougat,'saidtheDean,stilsmiling.

Quiteaneffortwouldbeneededtowipethatsmileaway,Ridculyknew,andsohegaveup.

'Goodshow,althesame,'hemumbled,andthenraisedhisvoice.

'Ifyoucanhearme,Hex...backtotheGreatHal,please.'

Nothinghappened.Animportantpartoftransferringmatteracrosstheworldisthemovingofanequivalentmasstheotherway.Thiscantakeawhile.

Thenanoaktable,threechairsandtwospoonscrashedintothebeach.Amomentlater,thewizardsvanished.

TWENTY-TWO

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FORGETTHEFACTS

IT'STHEORIESTHATMATTER.

Discworlddoesnothavescienceassuch.Butitdoeshaveavarietyofsystemsofcausality,rangingfromhumanintentions('I'ljustgooutforadrinkin

theMendedDrum')tomagicalspelstoageneralisednarrativiumthatkeepslocalandgeneralhistoryclosetothelinesof`story'.Roundworlddoeshavescience,butit'sdifficulttodiscovertheextenttowhichitdetermines,modifies,affectspeople'sactions-technologydoes,ofcourse,butdoesscience?Sciencedoesaffectwhatwedo,whatwethink,butitdoesn'tchangewhatwedoandthinkbecausesomuchofourbasicknowledgeissimplyacceptedscientific`fact'.

Wel,actualynot`fact',buttheory.

Wesearchfortheoriesbecausetheyorganisefacts.Wedothis,accordingtoTheScienceofDiscworldI,becausewearerealyPannarrans,thestorytelingape,notHomosapiens,thewiseman.Weinventourownstoriestohelpourselvestolive.Forthisreasonwearenotreliablewhenwecolect`facts'forscientificpurposes.Eventhebestscientists,andcertainlythepaidhelpandthestudentemployees,aresofulofwhattheywanttofindthatthere'snowaythatwhattheydofindcanrelatetotherealworldmorethantotheirownprejudices,biases,andwishes.However,wewerealtoldatschoolthat`science'sfactsarereliable',butthatitstheories-andevenmoresoitsworkinghypotheses-areandwereconstantlysubjecttocriticism,andthereforetochange.ItwasexplainedtousthatNewtonhadbeensupplantedbyEinstein,LamarckbyDarwin,FreudbySkinner...Soweweretoldthattheorieswereconstantlybeingsupplanted,butthattheobservationsonwhichtheywerebasedwerereliable.

Thisisthereverseofthetruth.

Noteacherpointedoutthatmany,perhapsmost,ofthebasicassumptionsofourintelectualworldwerescientifictheoriesthathadsurvivedcriticism...fromtheplaceofEarthandSolintheMilkyWaygalaxytothefertilisationtheoryofhumanconceptiontosubatomicphysicsproducingatombombs.

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..toOhm'sLawandtheelectricalenergygrid,tomedicaltrickslikethegermtheoryofdis

ease,althewaytoX-raysandMRI(magneticresonanceimaging),nottomentionchemicaltheoriesthatreliablygaveusnylon,polytheneanddetergents.Thesetheoriesgounnoticedbecausetheyhavebecomedefaults,socompletelyacceptedas`true'thatwefailtopaintthemwithemotionaltags,andsimplybuildthemintoourintelectualtoolkit.Eventhoughnoteacherpointedoutthattheywerescientificsuccesses,theyconstitutemuchofthe(regrettablybutunavoidably)uninspiringpartsofschoolscience.

OnthesefoundationbeliefswehangsuchglitteringfleshasvisitstoMars,newfertilitytechniqueslikeICSI,fusionpower,newbactericidesforkitchensurfaces-andforaminorityofthemoreimaginativechildren,thewideandwonderfulworldsofsciencefiction.

Thetheoriesofscience,then,particularlythetotalyacceptedoneslikesperm-eggconception,polythene,andEarth-orbits-Sun,aregoodreliablescience.Theyarecontinualytestedagainsttherealworldwhenbabiesareconceivedinfertilityclinics,whenpeopledothewashing-up,orwhenastronautscircletheEarthinsunlightandshadow.AnenormousmassofRoundworldscienceisbuiltintooureverydayworld,andit'smostlyreliable.

Butthereisalsoawholemassofsciencethatisincomprehensibletonearlyeverybody,whichpretendsthatit'sTheAnswerforalkindsoftechnicalorphilosophicalissues,andwhichsupportsexperts.Quantumtheoryistheclassiccase,relativityisatouchmoreaccessible,butsubatomicphysicsandmostofmedicine,aeronauticsandautomobileengineering,soilchemistryandbiology,statistics,andthehigherreachesofeconomics,arealsubjectsthatnearlyeverybodyiscontenttoleavetotheexperts.Mathematicshasastrangeposition,similarbutwithitsownpeculiarstanceakintorevealedreligion-mostlybecauseithasbeenpresentedfromschoolonwardsasanarcanecraftwhosepractitionersaretheonlyhumanswithaccesstoPlatonictruths.

Thentherearethequasi[1]-scienceslikeastrology,homeopathy,reflexology,andiridology,whichsimplycan'twork.Theyshouldbesharplydistinguishedfromodd,oftenancientpracticeslikeacupuncture,osteopathyandherbaltreatments,whichworksufficientlyoftenbuthaveatheoreticalbasethatispoorlyworkedoutinscientificterms.Manypeopleareattractedbytheirhomespunmixofmyth

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andmysticism(whicharealthemoreimpressivebecausethetreatmentsometimesworks),andfeelthatamodemscientificinvestigationwouldsomehowspoilthem.Itwouldcertainlypokesomeholesinthetraditionalrationalisations,butinallikelihooditwouldmakethetreatmentsevenbetter.Whereasthequasi-scienceswouldbe(indeed,alreadyhavebeen,notthateveryone'snoticed)demolished.

Toendthatlist,weaddevolutionarybiology,averywel-establishedsetofmodelsfoundedinthefossilrecord,chromosomes,andDNA,whichexplainssimilaritiesanddifferencesamongtoday'slivingcreaturesmuchmoreelegantlyandeffectivelythanitscreationistorinteligent-designrivals.Nevertheless,averylargeproportionofpeople-especialyChristiansintheAmericanMid-West,MuslimsinfanaticalyIslamiccultures,andfundamentalistbelieversingeneral[1]Pronounced`crazy'.

-denythathumansevolved.Tothem,theirownbrandofauthoritytrumpsthescientificevidence,ortheir`commonsense'rendersthewholeconceptlaughable.Ìain'tkintonoape!'wastheexplanationgivenbyayoungschoolgirlatoneofJack'sLifeonOtherPlanetslectures,whentheteacheraskedherwhyshedidn'tbelieveinevolution.

Thereisageneralhumanpropensity,ofwhichmuchuseismadeintheDiscworldbooks,tosetupaccepted,unexaminedmentalbackgrounds.

MostlytheseresultfromtheMake-a-Human-Beingkitsthateachhumancultureinflictsonitsmembersastheygrowupthroughchildhoodandadolescence.Eachofusistheresultofalearningprocess,onlyatinyfractionofwhichisovertèducation'byprofessionalteachers.Thekitincludesnurseryrhymes,songs,stories,thepersonificationofnurseryanimals(slyfoxes,wiseowls,industriouslitter-colectingWombles)andhumanrolesfromfabulouspostmanandprincessuptocrime-fightingBatmanandSuperman.Althesehavetheirplaceintheunexaminedbasisofourday-to-daythoughtsandactions.ApossibleexplanationforPrincessDiana'sundeniablepopularitywiththeBritishpublic-indeedtheworld-isthatshe,unlikèreal'royalty,hadimbibedthepopularimpressionofWhatPrincessesDoasdistinctfromtheauthenticalyroyalversion.Soshedidwhatwehadallearnedthatrealprincessesdo,shelookedandbehavedlikeanicon,notlikegenuineroyalty.

Sophisticatedhumanbeings,citizenslikeus-andindeedliketribesmenand

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barbarians[1]intoday'sworld,nearlyalofwhomhaveheardofSuperman,Tarzan,RonaldMacDonald-alhavethishotchpotch[1]ThisisaspecialusagedevisedbytheanthropologistLloydMorganinthe1880s,pickedupbyJohnCampbelJrinanAnalogeditorialinthe1960s,thenbyJackinThePrivilegedApe:fortribalhumans,everythingistraditional,mandatoryorforbidden;forbarbarians,actionisdrivenbyhonour,bravery,modesty,defianceofprecedent;forcitizens,somerolesaretribal,somebarbarian,wechoose.

ofimages,models,phobias,inspirationsandvilains.Ourday-to-dayexperiencegivesusaselfwhosememory-trainisasuccessionofscenes,thoughts,experiences,andpassions,alpaintedalaDamasiowithemotionaltagsthatsay`Great!',`DoThisAgainWhenICan!'orÀvoidAtAlCosts!'whenwerecalthem.Butthesesituponagreatmassofmostlyunexaminedstructuralhumanmaterial,thatlabelsusasWesternTwentieth-CenturyBiologistorGhettoRabbiorRomanCenturionorSeventeenth-CenturyFrenchCourtesan,or,formostpeoplemostofthetime,ExploitedPeasant.

Eachofthoseroleshasadifferentsetofemotionallabelsformoney,forpriests,forsex,fornakedness,fordeath,andforbirth.Mostpeople,untilquiterecently,underpinnedthatunexaminedsetofbeliefswithatheist(personal,humanlike)Godorgods,oradeist(SomethingUpTherewithExtraordinaryPowers)god-structure,sotheemotionaltagsonimportantmemorieshavebeenstronglyGodflavoured.Whenwerememberthemtheymaybesins,atonements,redemptionsortrials.Theymaybemitzvahs(blessings)orrevengesorcharities.Religions,inbringingusintoourculturesviatheirMakea-ChristianorMake-a-Mayakit,putdifferent-strengthlabelson,forexample,humansacrifice,sothatithasawholehostofassociationsinadultlife.Ouradultprejudices,andourscientifictheories,goinontopofthiscrazymishmashofhistoricalerrors,badlyunderstoodschooling,mathematicsandstatisticsthatbarelymakesensetous,God-storiesofcausalityandethics,andeducationallies-to-childrenthatpermittheteachertodisengagehisbraininresponsetochildren'squestions.

ThismentalmishmashiswelilustratedbyourchangingattitudestoMars.

Marswasknowntotheancientsasàwanderingstar',aplanet;itsreddishcolourhadbloodyassociations,sotheRomansassociateditwiththeirgodofwar.Italsoacquiredaconnectionwithwarinastrology,wherethevisiblestarsandplanetsalhadtomeansomething.We'regoingtolookatalotofdifferentassociationswithMars,[1]asmythandrationalityengagedwiththeredplanet,

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asstoriesbythehundredemployedMarsandMartians,andasthescientificpictureofMarschangedoverthecenturies.

Weshouldn'task`whichisthetrueMars?'Webecomelargerhumansbyconsideringaloftheseaspects;fromthatstancethererealyisn'tatrue,real,objectiveplanetforourmindstoengagewithusefuly.Oursimple,thincausallinescan'tcomprehendarealastronomicalobject,evenaworldwhichisactualyouttheresothatwecanseeit.Theìt'weseecanbethediscwhoseapparentlinesGiovanniSchiaparelicaled'canali',whichexcitedPercivalLowel(whosegraspofItalianseemstohavebeenslight,sincethewordmeans`channels')toseethemasengineeredcanals.HewroteMarsastheAbodeofLife,andthislaidthefoundationforthefolkMarsofthetwentiethcentury.

BetweentheWorldWars,everybodyintheWest,andmanyintheEast,lookedintothenightskyandsawinimicalMartians,amentalresidueofthat1920spictureofadrying,dyingMars.TheimagewasoverlaidbytheWaroftheWorldspictureofenvious,grim,disgustingtripodMartiansinvadingEarth(oratleastEngland).Therewasamoreromanticoverlayformanyofthoseoutcamping,orsleepingoutunderthestars:Barsoom.

EdgarRiceBurroughs,familiarbecauseofhisTarzanstories,inventedaMarswhosedried-outseabedswerehometogreenMartianwarriorhordes,six-leggedcentaur-likecreatureswhoseegg-incubatorswerevisitedregularly.JohnCarter,anAmericanex-confederatearmyofficer,hadwishedhimselfontoMars,beencapturedbythegreenwarriorsbutsoonfoundhimselfmarriedtoaredMartianprincess.[2]StanleyWeinbaum'sAMartianOdysseyaddedmoredimensions:theMartiancaledTweel,

[1]Notquiteincludingtheconfectionery,whichwasthesurnameoftheoriginator;hecametoEnglandfromtheUSA,andinventedM&Mstoo.

Thatstandsfor'MarsandMars'.

[2]Alsoegg-laying.Jack,readingBurroughswhenyoung,wasdisturbedbytheideaoftheirmarriagebed...

whomadelonghopsandlandedonhisnose,thehypnoticpredatorthatshowedyouyourmostdesirableimages,andattemptsatagosh-wowdesertecology.ThentherewerestoriesofMartianscomingtoEarth,pretendingtobehuman...andhumansattemptingtointeractwithamoreorlessmysticalancientMartian

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civilisation.

Thebestknown,perhapsthebestcraftedoftheseromanticmysticalportrayalsofcrude,lumberingEarthmen,insensitivetotheetherealbeautiesoftheMartiancrystalcities,wereRayBradbury's.Inthe1950sand1960shistaleswerereadbymanyoutsidethefantasy/SFworld,andtheyappearedinwidelyreadmagazineslikeArgosyaswelasinSF

pulpsinrailwaystationbookstores.TheylaidthemysticalancientMartianfoundationforRobertHeinleintobuildthemostpotentofaltheseMartiantales,StrangerinaStrangeLand.MichaelValentineSmithhadbeenafoundlingonMars,broughtupandtrainedintheirculturebytheancientMartians.HecametoEarth,foundedacommuneoffriends-'WaterBrothers'-andstartedareligionwhose'grokkingthefulness'ofeverydayevents,fromsextosciencetoswimming,spreadtocommunitiesofreaders.Therewasatragic,wel-publicisedassociationwiththemurderousMansonkilers,whohadusedthisbookastheirmantra,butthisdidn'tharmsales,andtheancientmysticalMartiansbecamethestandardimage.

ThenwelearnedthatMarshasnoatmospheretospeakof,thatitiscold,dry,ladenwithfrozencarbondioxide,totheextentthatthe'icecaps'wereprobablydryice.OurmachinesvisitedMars,lookedfor`life',andfoundstrangechemistrybecauseweinevitablyaskedthewrongquestions.Thècanals'diedinthepublicmind,replacedbycratersandgiganticvolcanoes.

Wehavenowvisitedagain,anditseemsthatancient,wetMarsmayhavebeenareality,theremaybeatleastbacteriallifeformsunderthesand...

Muchisnotyetclear,butwhatisclearisthatourimageofMarshaschangedyetagain.

EachofushasavarietyofassociationswithMars.Whenweweavethesemanydifferentinterpretationsandimaginationstogether,webecomeadifferent,wiserkindofcreature.AsforalofourdifferentMarses...wel,thosearetoysofourimaginations,aswegroktheredplanet'sfulness.

IfMarsseemsabitofadigression,considerthosetwiniconsofevolution,thearchaeopteryxandthedodo.Infolk-evolutionarythinking,thearchaeopteryxistheancestorofalthebirds,andthedodoisthebirdthatwentextinctabout400yearsago.Àsdeadasadodo.'Again,ourthinkingabouttheseiconiccreaturesis

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heavilydaubedwithunchalengedassumptions,myths,andfictionalassociations.

WementionedarchaeopteryxinChapter36(`RunningfromDinosaurs')ofTheScienceofDiscworld,secondedition.Wethinkofitastheancestralbirdbecauseitisadinosaur-likeanimalwithbirdlikefeathers...anditwasthefirstonetobefound.However,bythetimeofarchaeopteryxtherewereplentyofgenuinebirdsaround,amongthemthedivingbirdIchthyornis.

Pooroldarchaeopteryxarrivedonthescenefartoolatetobèthe'birdancestor.

Therecentamazing'dinobird'discoveriesinChina-transitionalcreaturespartwaybetweendinosaursandbirds-havetotalychangedscientists'

viewofbirdevolution.Atsomestagesomedinosaursstartedtodevelopfeathers,thoughtheycouldn'tthenfly.Thefeathershadsomeotherfunction,probablykeepingtheanimalwarm.Later,theyturnedouttobeusefulinwings.Somedinobirdseffectivelyhadfourwings-twoatthefront,twoattheback.Ittookawhilebeforethestandard`bird'body-plansettleddown.

Asforthedodo-wealknowwhatitlookedlike,right?Fatlittlethingwithabighookedbeak...Suchafamouslyextinctcreaturemustbeweldocumentedinthescientificliterature.

No,it'snot.Whatwehaveisabouttenpaintingsandhalfastuffedspecimen.[1]'Wehavemorespecimensofthearchaeopteryxthanwe[1]RajithDissanayake,'WhatdidtheDodolooklike?'Biologist51(2004),165-8.

doofthedodo.Why?Thedodowentextinct,remember?Anditdidsobeforesciencerealygotinterestedinit.Sofewpeoplerecordedit,orstudiedit.Itwasthere,notrequiringspecialattention,andthenitwasn't,anditwastoolatetostartstudyingit.Itisn'tevencertainwhatcolouritwas-manybookssay`grey',butitwasmorelikelybrown.

Yet,wealknowexactlywhatitlookedlike.Howcome?BecausewealsawitilustratedbySirJohnTennielinAlice'sAdventuresinWonderland.

Saynomore.

ThegreatstrengthofDiscworldnarrativeisthatitmakesfunofjustthoseplaces

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whereèducation'hasleftusfeelingabitvulnerable:wherewechangethesubjectinthepub,orwhenourfive-year-oldasksusthoseprobingquestions.ArunningjokethroughouttheScienceofDiscworldseriesiswhatgrammarianscal'privatives'.Theseareconceptsthatourmindsseemquitehappywith,eventhoughamoment'sthoughtshowsthatthey'recompletenonsense.Chapter22ofTheScienceofDiscworlddiscussedthisnotion,andwerecapbriefly.

Itisentirelynormaltospeakof`coldcominginthewindow'orìgnorancespreadingamongthemasses'.Theoppositesoftheseconcepts,heatandknowledge,arereal,butwe'vedignifiedtheirabsencewithwordsthatdonotcorrespondtoactualthings.InDiscworld,wefind'knurd',whichissuper-sober,asfarfromordinarysoberasdrunkisinthealcoholicdirection.Therearejokesaboutthespeedofdark,whichmustbefasterthanthespeedoflightbecausedarkhastogetoutoftheway.OnDiscworld,Deathexistsasa(perhapsthe)majorcharacter,butonRoundworldthatwordrefersonlytotheabsenceoflife.

Peoplehabitualylabeltheabsenceofsomethingwithaword,insteadof(oraswelas)itspresence:suchwordsaretheaforementionedprivatives.

Sometimesthishabitleadstomistakes.Theclassiccasewasthelabel`phlogiston',thesubstancethatappearstobeemittedbyburningmaterials.Youcanseeitcomingoutassmoke,flame,foam...Ittookmanyyearstodemonstratethatburningwasanintakeofoxygen,nottheemissionofphlogiston.Duringtheinterveningperiod,manypeoplehaddemonstratedthatwhenmetalsburnedtheygotheavier,andhadthereforearguedthatphlogistonhadnegativeweight.Thesewerecleverpeople;theyweren'tbeingstupid.Thephlogistonidearealydidwork-untiloxygensupplanteditsexplanations,andalchemistssuddenlyfoundthatthepathsintorationalchemistrywereeasier.

Privativesareoftenverytempting.InWhatisLife?,ashortbookpublishedin1944,thegreatphysicistErwinSchrodingeraskedpreciselythatquestion.AtthattimetheSecondLawofThermodynamics-everythingrunsdown,disorderalwaysincreases-wasthoughttobeafundamentalprincipleabouttheuniverse.Itimpliedthateventualyeverythingwouldbecomeagrey,coolsoupofmaximumentropy,maximumdisorder:àheatdeath'inwhichnothinginterestingcouldhappen.Soinordertoexplainhow,insuchauniverse,lifecouldoccur,Schrodingerclaimedthatlifecouldonlyputoffitsindividualtinyheatdeathbyimbibingnegativeentropy,or'negentropy'.Manyphysicistsstilbelievethis:thatlifeisunnatural,selfishlycausingentropytoincreasemoreinitsvicinitythanit

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wouldotherwisedo,byeatingnegentropy.

Thistendencytodenywhatishappeningbeforeourveryeyesispartofwhatitistobehuman.Discworldexploitsitforhumorousandseriouspurposes.BybuildingDiscworldflat,Terrypokesfunatflat-Earthers;rather,herecruitshisreadersintoàwealknowtheEarthisround,don'twe?'felowship.TheOmnians'beliefinaroundDisc,inSmalGods,addsafurthertwist.

Wewanttoputwhatrationalpeoplearecomingtobelieveintoageneralhumancontext,solet'slookatwhateveryonebelieves.Inthesedaysoffundamentalistterroristswewoulddoweltounderstandwhyafewpeopleholdbeliefsthataresodifferentfromtherational.Theseunexaminedbeliefsmaybevitalyimportant,becausetheignorantpeoplewhoespousethemthinkthattheyprovideagoodreasonforkilingusandourlovedones,eventhoughtheyhaveneverconsideredalternatives.PeopleWhoKnowTheTruth,byheredityorpersonalrevelationorauthority,arenotconcernedwithlogicorthevalidityofpremises.

Nearlyeverybodywhohaseverlivedhasbeenoneofthose.

Therehavebeenafewsparsetimesandplaces-andwearehopingthatthetwenty-firstcenturywilhostafewofthem-inwhichonlookersaremorereadytobelieveadisputantwhoisunsure,thanonewhoiscertain.Butintoday'spolitics,changingyourmindinresponsetonewevidenceisseenasaweakness.WhenhewasViceChanceloratWarwickUniversity,thebiologistSirBrianFolettremarked:Ìdon'tlikescientistsonmycommittees.Youdon'tknowwherethey'lstandonanyissue.Givethemsomemoredata,andtheychangetheirminds!'Heunderstoodthejoke:mostpoliticianswouldn'tevenrealiseitwasajoke.

Inordertodiscussthekindsofexplanationandunderstandingthataregoingtohavefuturevalues,weneedatleastasimplegeographyofwherehumanbeingspintheirfaithsnow.Whatkindsofworldpicturearemostcommon?Theyincludethoseoftheauthoritariantheist,themore-or-lessimaginativetheist,themorecriticaldeist,andvariouskindsofatheists-

fromBuddhistsandthefolowersofSpinozatothose,includingmanyscientistsandhistorians,whosimplybelievethattheageofreligionisbehindus.

Mosthumanbeingsofthelastfewmilenniaseemtohavebeenauthoritariantheists,andwestilhavemanyoftheminourworld;perhapstheyarestila

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majority.Doesthismeanthatwemustgiveintelectual'equaltime'totheseviews(plural,becausethey'realverydifferent:Zeus,Odin,Jahweh...),orcanwejustdismissthemalwithÌhavenoneedofthathypothesis',asLaplacesupposedly

saidtoNapoleon.Voltaire,awarethatGodmakingmaninHisimagemeantthatGod'snaturemightbededucedfromman's,thoughtitatleastpossiblethatGodhasmischievouslymisinformedusaboutrewardandpunishment.PerhapssinnersarerewardedbyHeavenandsaintsaregivenatasteofHel.Ourviewisthatalthevariousauthoritariantheistsarethecontemporarybearersofanextremelysuccessfulmemeplex,apackageofbeliefsdesignedandselectedthroughthegenerationstoensureitsownpropagation.

AtypicalmemeplexistheJewishshema:Àndthesewords...youshalteachthemtoyourchildren,museonthemwhenyougetupandwhenyouliedown...Writethemuponthedoorpostsofyourhouseanduponyourgates.'Likee-mailchainlettersthatthreatenyouwithpunishmentifyoufailtosendthemontomanyfriends,andwith`luck'ifyoudosendthemon,theworld'sgreatreligionshavealpromisedpleasuresforcommittedbelieversandtransmitters,butpainforthosewhofailtoadheretothefaith.

Heretics,andthosewholeavethefaith,areoftenkiledbythefaithful.

Wecaneasilyunderstandhowsuchbeliefs,bolsteredastheyarefromwithin,havebeenretainedthroughoutthegenerations.Thepromiseofanafterlife,espousedbyalthesensiblepeoplearoundyou,makesmanyofthislife'ssorrowseasiertobear.And,aswe'veseeninrecentyears,beliefinaParadiseforthosewhodiefightingforthefaithinaHolyWarmakesyouprettywelinvincible.[1]Suchinvincibilityisaside-effectofthememeplex'sbelieftactics,notacertificationofthetruthofthebomber'sfaith.Especialygiventhatnearlyalofthosewhosharethebomber'sfaith(Islam,Catholicism...)denythattheirbeliefsjustifykilingunbelievers.

Thispluralityoftheistbeliefs,especialyintoday'smixed-upworldwithitsdifferentculturesandmulticultures,encouragesamorecriticalbeliefinauthority,andusualyawilingnesstoadmit[1]AlthoughitdoesseemalittlestrangethatPalestinianterroristsprotecttheirgenitals,foruseinParadise,whensettingthemselvesupassuicidebombers.

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commonalitywithothertheists.Suchcommongroundencouragestheintegrationofdifferentcultures.Manyminoritiesareassimilatedanddisappear,butothersreactbyemphasisingtheirindividuality.Someofthelatter,liketheThuggeeworshippersofthedeathgoddessKaliinnineteenth-centuryIndia,andtherecental-Qaedaterrorists,gaintemporarynotorietythatseemstobeatriumphoftheirfaith.However,thisisusualyself-defeatinginthelongerterm.Inanyevent,thenumberofdeathsisnocomment,plusorminus,uponthetruthofthebeliefsthatthesethugshold.Thefaithofthesemilitantminoritiessometimesgainssharpnessandevensubtlety,butitisusualysubordinatedtotheday-todayexigenciesoftheviolentlivestheylead.

Manygreatscientists,forexampleGalileo,wereridiculedwhentheyproposednewinsightsintothenaturalworld.Scientificcrackpotsoftendeducethatbecausetheirworkisbeingridiculed,theymustbethenewGalileo,butthatdoesn'tfolow.Similarly,menofviolenceoftentrytovalidatetheir`martyrdom'bycomparingthemselvestoancientChristiansorghettoJews,andagainthelogicisflawed.Thereisnorationalreasontoacceptanyoftheirgodsaspartoftherealuniverse,howeverhelpfulthatbeliefmightbetosomepeopleasregardsday-to-dayliving.Despitethat,manyclever,honestpeopledofeelthataGodisnecessarytotheirunderstandingofhoweverythingisorganised.Onceamemeplexhascaughtyou,it'shardtoescape.

Wehavealittlemoresympathywithdeists,whomostlyseemtobelievethattheuniverseisextraordinarilycomplex,yetpossessesanoveralsimplicity,andthatthispointstosomecelestialguardianwholooksafterthewholethingandgivesitmeaning.PonderStibbonsandMustrumRidculy,intheirdifferentways,edgetowardsdeism;theywanttofeelthat`someone'isatthehelm.Ifchalenged,deistsusualydenytheanthropomorphiccharacterofthisguardian,buttheystilretainabeliefintheabilityofindividualpeople-perhapsindividual`souls'-torelatedirectlywithwhoeverorwhateverisincharge.Wepersonalydoubtthatsuchapparentinteractions,whetherattainedbymeditationorprayer,aremorethanselfdelusion.Butwearehappytoliveonthesameplanetaspeoplewhobelievethattheyareindirectcontactwithultimatecausality,howeverunscientificwemayfeelthatbelieftobe.

Thereisagrowingminorityofthoughtfulpeoplewhohavegivenupontheideaofapersonal,anthropomorphicGodaltogether.Some,particularlyamongBuddhistsandTaoists,retainthemystical/metaphysicalstancethatischaracteristicofreligion,andconsiderthèscientific'worldtobesubservienttoa

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mysticaltruepicturemorecloselyrelatedtosubjectiveexperience.Incontrast,thoseofuswhowerepersuadedbySpinoza'srejectionofananthropomorphicGod,notleastbecauseneithertheuniversenoranomnipotentdeitycanexistwithoutbeingcoextensivewitheverythingthereis,seethescientificviewasexposingboththenatureofgod,ifthatisourbelief,throughthelawsbywhichthingswork,andtheworkingsoftheuniverseitself.

Manyscientists,particularlythosewhoseendeavoursrelatecloselytotherealworld,likegeologists,astronomers,biologists,ecologists,andpolymerchemists,avoidthemysticalapproachandseetheirownspecialityasexemplifyingacomplexsliceoftheuniverse,withmanyemergentpropertiesthatarenotpredictablefromthedetailedsubstructure.Otherscientists,particularlythosedevotedtoreductionistexplanations,likephysicists,astrophysicists,physicalchemists,molecularbiologists,andgeneticists,retainaversionofthemysticalapproach,buttrytoexplainhigherlevelbehaviourintermsofthesubstructure.Telingly,manyscientistswhoworkatthècoalface'ofthesubjectgeneralyhavearespectfortheunknownpossibilitiesthattheuniversemightthrowatthem,whereasworkersinmoreabstractrealmslikequantumtheoryhaveatendencytogoalmysticalabouttheirownunderstanding,orlackofit.

Mosthumanattempts-atanexplanationtrytofindathincausalchainoflogicandnarrative,leadingfromthingsweaccepttowhateveritiswearetryingtoexplain.Thistypeofstoryappealstohumanminds,butitisusualyanoversimplification,anditleadstoseriousmisunderstandings.Thetypicaltelevisionscienceprogramme,whereasingleindividualisheldtoberesponsibleforsomebig`breakthrough',paintsawildlyinaccuratepictureoftheincrementalprocessbywhichmostscientificadvancesaremade.Unicausalexplanationsmakenicestories,butfailtocapturethecomplexitiesoftherealworld.Themosteffectiveexplanationsareoftenveryvaried,andit'sagoodideatofindalotofdifferentones,ifthey'reavailable.Physicistssearchingforaunificationofrelativityandquantumtheoryshouldperhapsbearinmindthepossibilitythatanyunificationmayturnouttobelesseffectivethanthetwoseparatetheories,eachsafelyconfinedtoitsowndomain.Onlyifyoucangetseveraltheoriestocompete,inyourmentalterritory,canyoubegintodistilunderstanding.

TWENTY-THREE

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THEGODOFEVOLUTION

`DOINGWELLBUTLOTSSTILLTOBEDONE!'barkedRidculy,stridingoutofthemagiccircleintotheGreatHal.Èverythingalright,MrStibbons?'

`Yes,Sir.Youdidn'ttrytostoptheGodofEvolutiontalkingtoDarwin,didyou?'

`No,yousaidweshouldn't,'saidRidculybriskly.

`Good.Ithadtohappen,'saidPonder.`SoalweneedtodonowispersuadeMrDarwin-'

Ì'vebeenthinkingaboutthat,Stibbons,'Ridculyinterrupted,àndIhavedecidedthatyouwilnowtakeMrDarwintomeetourGodofEvolutiononhisisland,'saidtheArchchancelor.Ìt'squitesafe.'

Ponderwentpale.Ì'drealyrathernotgothere,sir!'

`However,youwil,becauseIamArchchancelorandyouarenot'saidRidculy.`Let'sseewhathethinksofthewheeledelephant,eh?'

PonderglancedatDarwin,stilintheblueglowofstasis.`That'sverydangerous,sir.Thinkofwhathe'lbeseeing!Anditwouldbequiteunethicaltoremovethememoriesthat-'

ÌknowIamArchchancelor,it'swrittenonmydoor!'saidRidculy.`Showhimhisgod,MrStibbons,andleavetheworryingtome.Quickly,man.Iwantthisalwrappedupbydinnertime!'

AmomentafterPonderandDarwinleft,asmalboulderandquitealotofsandappearedandslidacrossthetilesoftheGreatHal.

`Weldone,MrHex,'saidRidculy.

+++Thankyou,Archchancelor+++Hexwrote.

Ìwaskindofhopingwe'dgetthechairsback,though.'

+++IwilseewhatIcandonexttime,Archchancelor+++

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AndonMonoIsland,CharlesDarwinpickedhimselfupfromthebeachandstaredaround.

`Doesthislenditselftoanyrationalexplanation,orisitmoremadness?'

hesaidtoPonder.Ìhavecutmyhandquitebadly!'

Atwhichpointtwolittleleavespushedthemselvesoutofthegroundnearhisfootand,withamazingspeed,becameaplant.Itthrewupmoreleaves,thendevelopedasingleredflowerwhichopenedlikeanexplosionanddiedlikeasparktoproduceonesingleseed,whichwaswhiteandfluffy.

Òh,abandageplant,'saidPonder,pickingit.`Hereyouare,sir.'

`How-'Darwinbegan.

Ìtjustunderstoodwhatyouneeded,sir,'saidPonder,leadingtheway.

`ThisisMonoIsland,thehomeoftheGodofEvolution.'

Àgodofevolution?'saidDarwin,stumblingafterhim.`Butevolutionisaprocessinherentin-'

`Ye-yes,Iknowwhatyou'rethinking,sir.Butthingsaredifferenthere.

Thereisagodofevolutionandhe...improvesthings.That'swhywethinkeverythinghereisdesperatetogetofftheisland,poorcreatures.

Somehowtheyknowwhatyouwantandevolveasfastastheycaninthehopeyou'lpickthemtotakeaway.'

`Thatisnotpossible!Evolutionneedsmanythousandsofyearsto-'

`Pencil,'saidPonder,calmly.Atreenearbyshivered.

Àctualy,thepencilbushbreedstrueintherightsoil,'Ponderwenton,walkingovertoit.`We'vegotsomeoftheseattheUniversity.AndtheChairofIndefiniteStudieskeptacigarettetreegoingformonths,buttheygotverytarry.OncemostofthemgetfarenoughawayfromMonoislandtheystoptrying.'Heheldoneout.`Wouldyoulikearipepencil?They'requiteuseful.'

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DarwintooktheslimcylinderPonderhadpluckedfromthetree.Itwaswarm,andstilslightlymoist.

`ThisisMonoIsland,yousee,'saidPonder,andpointedtothesmalmountainatthefarendoftheisland.Ùpthereiswherethegodlives.Notabadoldboy,asgodsgo,buthewilkeepchangingthingsalthetime.

Whenwemethimhe-'

Thebushesrustled,andPonderdraggedthebemusedDarwinasideassomethingrattleddownthepath.

`That'sagianttortoise!'saidDarwin,asittrundledpast.`Thatatleastissomething-oh!'

`Yes.'

Ìt'sonwheels!'

Òh,yes.He'sverykeenonwheels.Hethinkswheelsshouldwork.'

Thetortoiseturnedquiteprofessionalyandroledtoahaltbyacactus,whichitproceededtoeat,daintily,untiltherewasahissanditsaggedsideways.

'Oh,'saidavoicefromtheair.`Badluck.Tyrebladderpunctured.It'stheeverlastingproblemofthestrengthoftheintegumentversustheusagerateofthemucus.'

Askinny,ratherpreoccupiedman,dressedinagrubbytoga,appearedbetweenthetwoofthem.Beetlesorbitedhimlikewonderfullittleasteroids.

`Depositionofmetalmaybeourfriendhere,'hesaid,andturningtoPonderasiftoanotheroldfriendhewenton:`Whatdoyouthink?'

Àh,um,er...doyourealyneedalthatshel?'saidPonder,hurriedly.

Beetles,brightastinygalaxies,landedonhisrobe.

Ìknowwhatyoumean,'saidtheoldman.`Tooheavy,perhaps?Oh...youseemfamiliar,youngman.Havewemetbefore?

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'PonderStibbons,Sir.Iwashereafewyearsago.Withsomewizards,'

saidPonder,withcare.He'dquiteadmiredtheGodofEvolution,untilhe'dfoundthatthegodconsideredthecockroachtobethepeakoftheevolutionarypyramid.

Àh,yes.Youhadtoleaveinsuchahurry,Irecal,'saidthegod,sadly.'itwas-'

`You!...youappearedinmyroom!'saidDarwin,who'dbeenstaringatthegodwithhismouthopen.`Therewerebeetleseverywhere!'

Hestopped,hismouthopeningandshuttingforawhile.`Butyoucertainlyarenot...Ithoughtyou-'

Ponderwasreadyforthis.

`YouknowaboutOlympus,sir?'hesaidquickly.`What?ThisisGreece?'

saidDarwin.

`No,sir,butwe'vegotlotsofgodshere.This,er,gentlemanisn't,asyoumightputit,thegod.He'sjustagod.'

Ìsthereaproblem?'saidtheGodofEvolution,givingthemaworriedsmile.

Àgod?'Darwindemanded.

Òneoftheniceones,'saidPonderquickly.

Ìliketothinkso,'saidthegod,beaminghappily.`Look,Ineedtocheckonhowthewhalesaredoing.Whydon'tyoucomeupthemountainfortea?Ilovetohavevisitors.'

Hevanished.

`ButtheGreekgodsweremyths!'Darwinburstout,staringatthesuddenlyemptyspace.

Ìwouldn'tknowaboutthat,sir,'saidPonder.Òursaren't.Onthisworld,godsareextremelyreal.'

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`Hecamethroughthewal!'saidDarwin,pointingangrilyattheemptyair.`Hetoldmethathewasimmanentinalthings!'

`Hetinkersalot,certainly,'saidPonder.`Butonlyhere.'`Tinkers!'

`ShalwetakealittlewalkupMountImpossible?'saidPonder.

MostofMountImpossiblewasholow.Youneedalotofspacewhenyouaretryingtodeviseadirigiblewhale.Ìtrealyshouldwork,'saidtheGodofEvolution,overtea.`Without

thatheavyblubberandwithaninflatableskeletonofwhich,ImustsayIamratherproud,itshoulddowelontheroutesofmigratorybirds.Largermaw,ofcourse.Notethecloud-likecamouflage,obviouslyrequired.Liftingisproducedviabacteriainthegutwhichproduceelevatinggases.Thedorsalsailandtheflattenedtailgiveareasonabledegreeofsteerability.

Alinal,agoodpieceofwork.Mymainproblemisdevisingapredator.

Thesea-airbalisticsharkhasprovedquiteunsatisfactory.Idon'tknowifyoumighthaveanysuggestions,MrDarwin?'

PonderlookedatDarwin.Thepoorman,hisfacegrey,wasstaringupatthetwowhaleswhowerecruisinggentlyneartheroofofthecave.

Ìbegyourpardon?'hesaid.

`Thegodwouldliketoknowwhatcouldattackthis,'Ponderprompted.

`Yes,thegreypeoplesaidyouwereveryinterestedinevolution,'saidthegod.

`Thegreypeople?'saidPonder.

Òhyes,youknow.Youseethemflyingaroundsometimes.Theysaidsomeonerealywantedtolistentomyviews.Iwassopleased.Lotsofpeoplejustlaugh.'

Darwinlookedaroundthecelestialworkshopandsaid:Ìcannotseeanythingtolaughatinanelephantwithsails,sir!'

Èxactly!Itwasthebigearsthatgavemethecluethere,'saidthegodcheerfuly.

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`Makingthembiggerwassimplicityitself.Itcandotwenty-fivemilesanhouracrosstheopenveldtinagoodwind!'

Ùntilawheelbursts,'saidDarwin,flatly.

Ì'msureoncetheygettheideaitwilalwork,'saidthegod.`Youdon'tthinkitmightbebettertoletthingsevolvebythemselves?'saidDarwin.

`Mydearsir,it'ssodul,'saidthegod.`Fourlegs,twoeyesonemouth...

sofewarepreparedtoexperiment.'

OnceagainDarwinlookedaroundtheglowinginteriorofMountImpossible.Ponderwatchedhimtakeinthedetails:thecageofwebwingedocto-monkeysthatintheorycouldskimacrossthecanopyforhundredsofyards,thePhaseoluscoccineusgiganticusthatactualybredtrue,iftherewasanypossibleuseforabeanstalkthatcouldgrowhalfamilehigh...andeverywheretheanimals,ofteninstagesofassemblyordisassemblybutalquitecontentedlyaliveinalittlemistofholiness.

`Mr,er,Stibbons,Ishouldliketogo...homenow,please,'saidDarwin,whohadgonepale.`Thishasalbeenmost...instructive,butIshouldliketogohome.'

Òhdear,peoplearealwaysrushingoff,'saidthegod,sadly.`Butstil,IhopeIhavebeenofhelp,MrDarwin?'

Ìndeed,Ibelieveyouhave,'saidDarwin,grimly.

Thegodaccompaniedthemtothemouthofthecave,beetlesstreamingbehindhiminacloud.

`Docalagain,'hesaid,astheywanderedoffdownthetrack.Ìdoliketo-'

Hewasinterruptedbyanoiselikealthepartybaloonsintheworldbeingletdownatonce.Itwaslonganddrawnoutandfulofmelancholy.

Òhno,'saidtheGodofEvolution,hurryingbackinside,`notthewhales!'

Darwinwassilentastheywalkedtothebeach.Hewasevenmoresilentastheypassedthewheeledtortoise,whichwaslimpingincircles.Thesilencewas

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deafeningwhenPondersummonedHex.WhentheyappearedintheGreatHalhissilence,apartfromabriefscreamduringtheactualtraveling,wasahugeinfectioussilencethatwascontagious.

Theassembledwizardsshuffledtheirfeet.Darkrageradiatedofftheirvisitor.

`Howdiditgo,Stibbons?'whisperedRidculy.

'Er,theGodofEvolutionwashisusualself,sir.'

`Washe?Ah,good-'

Ìwish,veryclearly,toawakenfromthisnightmare,'saidDarwin,abruptly.

Thewizardsstaredattheman,whowasquiveringwithrage.`Verywel,sir,'Ridculysaidquietly.`Wecanhelpyouwakeup.Excuseusamoment.'

Hewavedahand;onceagaintheblueshimmersurroundedtheirvisitor.

`Gentlemen,ifyouplease?'

Hebeckonedtotheotherseniorwizards,whoclusteredaroundhim.

`Wecanputhimbackwithouthimhavinganymemoryofanythingthathappenedhere,right?'hesaid.`MrStibbons?'

`Yes,Sir.Hexcoulddoit.ButasIsaid,sir,itwouldn'tbeveryethicaltomessaroundwithhismind.'

`Wel,Iwouldn'tlikeanyonetothinkwe'reunethical,'saidRidculyfirmly.Heglaredaround.Ànyoneobject?Good.Yousee,I'vebeentakingtoHex.I'dliketogivehimsomethingtoremember.Weowehimthat,atleast.'

`Realy,sir?'saidPonder.`Won'titmakethingsworse?'

Ì'dlikehimtoknowwhywedidalthis,evenifit'sonlyforamoment!'

Àreyousurethat'sagoodidea,Mustrum?'saidtheLecturerinRecentRunes.

TheArchchancelorhesitated.`No,'hesaid.`Butit'smine.Andwe'regoingtodoit.'

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TWENTY-FOUR

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ALACKOFSERGEANTS

WHATWASITABOUTVICTORIANENGLAND,andwhatleduptoit,thatmadeitsoprogressive,inventiveandinnovative?WhywasitsodifferentfromRussia,China,andaltheothernationsthatseemtohavestagnatedduringthenineteenthcentury-accumulatingwealth,butlackingamiddleclassfulofengineers,seacaptains,clerics,andscientists?Wewouldnotexpecttheretobeonesimpleanswer,onetrickthatVictorianEnglanddiscoveredbutothernationsdidnot.Thatwouldsatisfytheinnatehumanwishforasinglethincausalchain,butaswe'veseen,historydoesn'tworklikethat.

Equaly,though,it'sunsatisfyingjusttolistlotsofpossiblecontributorycauses-theEastIndiaCompany...Harrison'sexcelentchronometer,whichhelpedtomaketheBritishEmpiresoprofitableandmadearistocraticfamiliessendtheiryoungersonsfairlysafelyoutintotheEmpire,fromwhichtheycamebackwiserandricher...Quakersandothernonconformistsects,whichweretoleratedbytheAnglicanChurch...theLunarSociety'sprogeny,includingtheRoyalSocietyandtheLinnaeanSociety...theColegeofApprentices...Parliamentandthepretenceofdemocracy,sothatamiddleclasscouldrisefromthemergingofjunioraristocratswhocamebackfromtheEmpiretofoundpicklefactoriesinManchester...artisanswhowerecomingintotownslookingforsatisfyingjobs.

Wecouldmakethelisttentimeslonger,thoughinmostcaseswewouldn'tbesureaboutgenuinecausalconnections.Andevenwithtentimesasmany`causes',wewouldstilhavetosayàloftheabove'.

Aresuchfactorsacauseofhistoricaldifferences,oraconsequence?

That'snotasensiblequestionifyouinsistonayes/noanswer-veryprobablytheanswershouldbèboth'.Amodemanaloguewouldbetoaskwhethertoday'sspace-orientedengineersandscientistsareacauseofthesuccessofspacefilmsandnailed-downscience-fictionstories-ordidtheearlyscientificalyorientedSFstories,withtheirsenseofwonderatthesheervastnessandmysteryofouterspace,firethoseengineers,whenyoung,withthedesiretoturnfictionintofact?Itmusthavebeenboth,ofcourse.

TheearlyVictorianapprenticesinpottery,ironworking,brickfiring,andevenbricklayingwererespectedby,andrespected,theirmasters.

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Togethertheylaiddownenduringmonumentsforfuturegenerations.

Similarly,earlytrainsandcanalsconnectedalthemajorcities,andconnectedfactoriestotheirsuppliersandcustomers.ThistransportsystempavedthewaytothewonderfuleconomicnetworkthatEdwardianBritaininheritedfromtheVictorians.Thesesystemswerenotstatic,tobeadmiredforwhattheyhadachieved.Theyweredynamic,theychanged,theywereprocessesasmuchasachievements.Theychangedthewaysucceedinggenerationsthoughtaboutwhereandhowtheylived.Eventoday,ourcitiesrelyheavilyonwhattheVictoriansbuilt,especialywhenitcomestosewerageandwatersupplies.

Theresultingchangesinthinkingfueledfurtherchanges.Thecombinationofcauseandconsequenceisanexampleofwhatwehaveelsewherecaledcomplicity.[1]Thisphenomenonariseswhentwoconceptualydistinctsystemsinteractrecursively,eachrepeatedlychangingtheother,sothattheyco-evolve.Atypicaloutcomeisthat[1]SeeJackCohenandIanStewart,TheColapseofCbaos(Viking,1994).

togethertheyworktheirwayintoterritorythatwouldhavebeeninaccessibletoeitheralone.Complicityisnotmereìnteraction',wherethesystemsjoinforcestoachievesomejointoutcome,butarenotthemselvesgreatlyaffectedasaresult.Itisfarmoredrastic,anditchangeseverything.Itcaneveneraseitsownorigins,sothatneitheroftheoriginalseparatesystemsremains.

Thesocialinnovationsthatwere(arguablybutnotsolely)triggeredbyVictorianingenuityanddrivearejustlikethat.Becausetherewasselection,andbecausethebestgrowthoftenoccursinthebestrunandbestdesignedpartsofgrowingsystems,therewasrecursion.Thenextgenerationwasinspiredbythepreviousgeneration'ssuccesses,andtheirnoblemistakes,andbuiltabetterworld.WhatwemightcaltheChannelTunnelSyndromeoccursquiteoftenincapitalist,democraticsocieties,butnotintotalitarianstatesoreveninnationslike,say,today'sArabstatesortwentieth-centuryIndia.Andparticularlynotinnineteenth-centuryRussiaorChina:bothwererich,buttheyhadnorespectablemiddleclass.

TheVictorianmiddleclasswasrespectedbothbytheworkerswhoselivestheyexploited-andopenedup-andbythearistocrats,whoseincreasinglyinternationaloutlookwasprogressivelyintegratedwithtrade.RussiaandChinahadpoliticalsystemswithoutaneconomicalypowerful,shareholdingmiddle

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class,whichcouldstartorfolowfashions,andsupportromantic,visionaryventures.Today,theBritishwilstilsupportaChannelTunnelventureoraBeagle-2Marslander,becausesuchthingsareromanticandpossiblyheroic,eventhoughtheyareunlikelytobeveryprofitable.Alengthyhistoricalrecordshowsveryclearlythatthefirstattemptatanymajortunnelusualycolapsesfinancialy-thoughafterthetunnelissuccessfulybuilt-oftenafteralongseriesofattemptstoshoreupafailingenterprise.Thentheruinsareboughtforasong,occasionalynationalisedorconsiderablyfinancedbygovernmentorsomeothermajorcapitalsource,andtheresultingbusinesscanstandontheshouldersofthefirst.OnlysomeratherstrainedeconomicshassofarkepttheoriginalcompaniesinvolvedintheChannelTunnelinbusiness,atleastontheBritishsideoftheChannelwhereeverythingwasdonebyprivateenterprise.

Someprojectsaresoromantic,soattractiveinconceptbutsoverydifficultinexecution,thatthreeorfourattemptsareneededforthemtoacquiremomentum.Itisrecursivestructureofthecomplicitkindthatkeepsthemafloat.[1]Telford'sbridgesarefamous,asaresomanyofhisotherengineeringworks;hisabilitytocapitaliseonhissuccesseswastheresult,andthecause,ofhisfame,whichwasachievedbywhatwouldnowbecaled`networking'amongaristocrats,governmentministers,andpicklemanufacturers.Hewas,astheysaid,famousforbeingfamous.InAmericasimilarenterprisesweremeasuredmorebytheanticipatedfinancialreturn,thèbottomline'.SoJohnD.Rockefeler,AndrewCarnegie,andtheirilkwereworthsupportingbecauseyourinvestmentwasguaranteedtomultiply,ratherthanbecausetheenterprisewasexciting`forQueenandCountry'.Earlytwentieth-centuryAmericahadgigantic,monolithicFord...

whileEnglandhadavarietyofsmalengineeringconcernslikeMorrisGarages(MG).

TheothermajorreasonwhysocietieslikeVictorianEnglandcanpickthemselvesupbytheirbootstrapsandflyisonewe'vediscussedearlier.

Theyliftthemselvesoutoftheoldconstraints,andintoanewsetofrules.InTheScienceofDiscworldandTheScienceofDiscworldIweexplainedwhythespacebolas,akindofenormousFerriswheelinorbit,iscapableofcarryingpeopleintospacefarcheaperthanrockets-infact,requiringlessenergythananyonewouldcalculateusingNewton'slawsofmotionandgravity.Wetookone

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[1]Intheir1980bookAutopoiesisandCognition,HumbertoMaturanaandFranciscoVarelaconfusedthiskindofrecursionwithalifeforce,andcaledit'autopoiesis'.Manyselfconsciouslymodemmanagementexpertscitethisconcept,withouthavingthefoggiestideawhatitis.

furtherstep,andinvokedthespaceelevator,averystrongcablehungfromgeostationaryorbit,whichwouldbehardertobuildbutwouldrequireevenlessenergy.Thetrickisthatpeopleandgoodscomingdowncanhelptoliftotherpeopleandgoodsup.Theenergeticssatisfyalthestandardmathematicalrules,butthecontextsuppliesanunexpectedsourceofenergy.

Thesegadgetsworkbetterthanrockets,butnotbecausetheseuserelativityorotherclevernewphysicslikequantum.Orbecausetheydon'tobeyNewton'slaws,becausetheydo,totheextentthatthesearestilrelevant.Instead,thebolasandtheelevatorhavenewinventionimmortalisedintothem,sothataspacemanwhogetsintothecabinofabolasinthinupperatmospherefromajetaircraftcanshortlyafterwardsgetoutofthecabin400milesup.Goingattherightspeed,itsohappens,tocatchthepassingcabinofa400-milespacebolas,whichcandeposithim,dayslater,intherightorbittocatchthe15,000-milebolas,whichdepositshimingeostationaryorbit,22,000milesup,afteracoupleofweeks.SuchmachinescanbepoweredbyusingthemtodropvaluableasteroidmaterialdowntoEarth,or(inthecaseofthebolas)by`pumping'themlikeagardenswing,usingmotorsinthemiddlepoweredbysunlightandreelinginorlettingoutthecabintethersasthebolasrotates.

Oncewe'vemadethehugeinitialinvestmentrequiredtobuildsuchmachinery,rockettechnologybecomeslargelyobsolete,justasanimaltractionwasdispossessedbytheinternalcombustionengine.Sure,youcan'tattach500horsestothefrontofabigcanal-barge,becausetherewouldn'tberoomonthetowpath-buta500horsepowermarineengineisanothermatterentirely.Sure,arocketwouldusefartoomuchfueltobeapracticalmethodforhoistinggoodsandpeopleintoorbitenmasse-butthat'snottheonlywaytogetthemthere.Yes,Newton'slawsstilhavetobeobeyed,andyouhavetòpay'toseteverythingup,anditstilcostsjustthesameenergytogetpeopleintoorbit.Butnobodypaysoncethemachineryisthere.Ifyoudon'tbelievethis,goupinanelevatorinaskyscraper,notinghowthecounterbalanceweightsgodown,andreturntosolidground.Then,toramthemessagehome,walkupthestairs.

Thewordprocessorwe'reusingtotypethisbookisametaphoricalspaceelevator

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comparedtoamanualtypewriter(rememberthose?Maybenot).

AmodemautomobileisaspaceelevatorcomparedtoaFordmodelToranAustin-7,whichwerethemselvesbolases,while1880ssteamcarswererockets.ThinkoftheinvestmentthatwentintotheVictorianrailwaysystem,thecanals-thenrealisehowthisimmenseinvestmentchangedtherules,sothatlatergenerationscoulddoalkindsofthingsthatwereimpossibletotheirforebears.

Victoriana,then,wasnotasituation,itwasaprocess.Arecursiveprocess,whichbuiltitselfnewrulesandnewabilities,asprevioushardworkandinnovationledtonewcapital,newmoney,andnewinvestment.

Thenewpoor,downtroddenthoughtheymayhavebeen,weremuchbetteroffthantheruralpoorhadbeen.Whichiswhypeoplepouredintothecitieswheretheirlives,eventhoughDickensian,wereeasierandmoreinterestingthantheyhadbeeninthecountryside.Theurbannewcomersprovidedanewworkforcetobuildnewindustries.Theyprovidedausefulconsumerbasetoo.Thoseworkmen'scottages,stilfoundinthesuburbsofmanytowns,werenotonlyhousingforanexploitedlabourforce;theywerealsoasourceofnewwealthforthatyoungaristocratbackfromtheGoldCoastwho'dopenedapicklefactoryinManchester.HehadseenthesaucesmadeinMadagascarorGoa,likedthetaste,andthoughtthathecouldselthemtoworkmentoputontheirsausagesandbacon.Thinkofhimforamoment,perhapsachinlesswonderwhoemployedthirtymentomixthetropical-fruitingredientsandboilthemingreatcast-ironvats.ThevatshadbeenmadeinSheffieldandcarriedbynarrow-boatalongcanals,givingcointoperhapsfiftyworkmenwhosuppliedtheoriginalvatsandbuildings:[1]Hispicklecompanysupportedawholesmalindustryforgenerations:supplyingcokeforheating,importedandlocalygrownfruitandspicestobeprocessedintosauces,specialwater,glassbottles,printedlabels...

[1]WhenJackstartedatBirminghamUniversityinthe1950s,thefactorybehindtheuniversitymadecookingpotsformissionaries,justliketheonesthatwerepopularinthecartoonsinPunch-withthemissionariesasingredients,notcooks,youappreciate.NodoubtthesamefactoryhadoncemadetheoriginalsaucevatsusedinMadagascarandGoa.

Therewouldhavebeenhalfadozenmiddle-agedmatronsbusyatdifferenttasksinhisfactory,too,evenbossingsomeofthemen.Thiswasnew-

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outsidethehome,anyway.Womenalsogotjobswithhimascleaners,perhapsassecretariestosomeoftheseniorstaff,andwomenearningtheirownmoneywasamassivewedgedrivenintoamale-dominatedsociety.Inthatsociety,itwasrareevenforcourtesanstohavecontroloftheirownfunds,tothatextentMimiinLaBohemeismorerealisticthanFlorainLaTraviata.Thelawsandcustomsthenwereverydifferentfromwhatweacceptas'normal'now:youngwomenandolderoneswereexploitedsexualy,largenumbersofworkmendiedfromindustrialaccidentsandpolution.[1]Onlythroughtheirsuffering-andtheirtriumphs-

couldthenextgenerationbebuilt.

Today'sBritonsareanintegralpartofthisonwardandupwardprocess,andinordertoseewhythetriumphsofourrealVictorianhistoryhavelessonsforusnow,wemustunderstandwhathappenedthen.

Therewasonemajordifference,amongmilionsofindividualtinydifferences,betweenVictorianBritainandRussia(orChina).The[1]Detailscanbefoundinmanypersonaldiaries,suchasthosekeptbytheforemenofthespinningandweavingmilsinLancashireasexercisesinwritingfortheireveningclasses.Welearnthatsexualengagementwithwomenemployeeswassometimesnecessaryforthesemen,inordertoretaintherespectoftheircoleagues,tomaintainobediencebytheworkforce,evenwhentheyfoundithorriblethemselves.Inthearmedforces,ofcourse,andinprisons,thesocial'rules',thepeerpressuretosingrossly,weretoopowerfultoresist,tooawfulforustocontemplatenow.

Britishhadseveralsourcesofsocialheterogeneity,dissidence,ofexposuretothepubliceyeofthingsbeingdoneorunderstoodindifferentways.FromtheBaptistchapeltotheQuakermeetinghouse,fromtheCatholiccathedralwithitssweetmusicandincomprehensibleprayerstotheJewishsynagogueswiththeirstrangelycloakedandhattedcongregantswhoturnedintoyourlawyeroryouraccountantduringtheweek,religionwasobviouslydiverse.InPolandandRussia,therewerepogroms(particularlyduringthelatenineteenthcentury);inEngland,therewereonlytaxes.EveninEnglishprisons,verydifferentreligiouspracticeswererespected,perhapsasmuchinthebreachasinthepractice,butthetheorywaswelknownandencouraged-ifnotenforced-bythelaw.Thisfreedomofthought,wordanddeedlasted.AftertheSecondWorldWar,afterthedefeatofNazismatimmensecost,withLondonstilinruinsandfoodrationed,SirOswaldMosleywasanavowedfascistwhoseBlackshirtscamedowntothe

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EastEndofLondontopromotetheirracistviews.Jackwasinvolvedinstreetfightswiththemaboutonceamonth.

Eventhen,hewaspleasedthattheirhorriblespeecheswerepermittedbythelaw.IntheUSAorRussia,Mosleywouldeitherhavebeeninjailorelectedpresident.Therewasacontextofheterogeneity,ofdifferencebeingmorethanaccepted,beingvaluedwithasmile.Andthiswaspartofanunbrokentradition,goingbacktoVictoriantimes.

ThebigdifferencethatmadeVictorianBritainsuccessful,itselffosteredrecursivelybyalthesuccessstorieswithinit-andbythedisparatenatureofthesesuccesses,suchasQuakers,railways,bigbeautifulbridges,fewerstarvingchildren,controlofsomediseases-wasintheambience,thecontext,whichpromoteddifference.Ithasbeenfashionableforaparticularlynaivekindofhistorianofsciencetopointtothesocialcontextofscientifictheories,andtopretendthatscienceisthereforeentirelysocialydriven.Itisusualyclaimed,bythesametoken,thatthisprovenancedeniesscienceitsauthority,soitstruthsmerelyfolowsocialconvention.

Victorianevolutionistsprovideapreciserefutationofthatview.

Walace,forexample,wasborntopoorparents,wasapprenticedtoawatchmakerforawhile(obviouslyoneofourwizardshadbeeninstructedtoachievethis),thenbecameasuccessful-thoughindigent-landagent,thenamoresuccessfulanimalandplantcolector.Henevermadeenoughmoneytojointheuppermiddleclass,evenafterhisstarhadrisenalongsideDarwin's.

Darwinwasajunioraristocrat,hisparentswereweloff,anditwouldhavebeenentirelyproperforhimtohavebecomeacurate-and,indeedtohavewrittenTheologyofSpecies.Otherproevolutionists,asvariousasOwen(mistakenbyDarwinforanantievolutionistbecauseofhiscarefulanalysisoftheanatomicalimplicationsoftheDarwin/Walacenatural-selectionidea),Huxley,Spencer,Kingsley,werealfromdifferentstrataofsociety.

WehaveseenthatthefirstprintingofOriginofSpecieswasinadequateforthemarket,andalcopiesweresoldbythesecondmorningafterpublication.Wouldthathavehappenedinnineteenth-centuryIndia?InRussiaundertheczars,oraftertherevolution?IntheUnitedStates...

possibly.AndintheGermanpartofPrussia.Dickens'sstories,criticalasthey

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wereoftheexistingorder,wereanxiouslyawaitedbyalstrataofsocietyinEngland-andbymanyintheeasternUnitedStates.

Itwouldnothavebeenquitesostrangeifthisheterogeneoussocietyinvolveddifferentgroupsthatpickedupondifferentideas,accordingtotheirvariousphilosophiesandtheologies.However,whatrealyhappened,bothtoDickensandtoDarwinandlatertoWels,wasaverygeneralappreciationoftheirradicalideas,verywidely,acrossalofthosediversegroups.Thesamealternativeviewswerewelcomedbymanydifferentstrataofsociety.Moreso,perhaps,thaninanyothersocietysince,heterodoxywasalmosttherule.Workingmen'sclubswerehotbedsofrationalargument,thankstotheestablishmentofeveningclassesbytheWorkers'EducationalAssociation.EducationforthecommonmanwaspromotedbythenewtechnicalcolegesandtheBritishAssociationfortheAdvancementofScience.

Tosomeextent,thesamewentforaltheembryouniversitieswhich,inVictoriantimes,hadbeenseededbyphilanthropicdiscussiongroupsinthebigcities.Theseestablishments,darkred-brickbuildingsfoundinthecentresofalEnglishindustrialcities,wereverydifferentorganisationsfromtheancientuniversities.Theotherhalfofthebuilding,orthebuildingoppositeonthesamestreet,wasoftenthepubliclibrary,anorganisationnottobefoundinRussiaorChinaatthattime.Theseorganisationsprovidedawayupfrommanuallabourtoartisan,andtherewereathousandsuchestablishmentsaloverVictoriana.

Therealuniversities,ofOxford,Cambridge,Edinburgh,StAndrew's,werepromotingorthodoxyviaclassicsandtheliteraryandgovernmentalarts.

Thescienceswereslowlycomingin,mainlyastheoreticalphysicsandastrophysics,whichneededonlybrainsandblackboards,likemathematics.Practicalscienceslikegeologyandpalaeontology,chemistry,andzoologywentonindarkanddirtylaboratorieswithtalglassanddarkwoodpartitions;botanywasbackedupbyaromaticherbaria.

Suchworkhadaverylowstatuscomparedtomathematicsandphilosophy-ithadassociationswithmanuallabouranddirt.However,archaeology,becauseofitscontinuingassociationwiththeclassicalworldanditsartefacts,hadquitehighstatus.

Theburgeoningmiddleclassdidn't,byandlarge,aspiretothesearcane

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practices.Theywantedtechnicalandscientificinformation,nottopotteraboutwiththeories,howeverimportantandromantic.Theydidn'twantclassicalanything,certainlynottheclassics.Theuniversitiesproperwerestilrequiringaclassicaleducationofalaspiringstudents,andeveninthe1970stheycontinuedtorequirecompetenceinaforeignlanguagefromscienceentrants(asevidence,presumably,ofsomeculture-theyneverrequiredscienceormathematicsfromartsorclassicsentrants).Theworkmenandtheartisans'guildscooperatedtoproducetheapprenticeshipsystem,andthiswasinmanywaysthemodelfortheirowneducationalorganisations.

These,notablytheWEA,providedexactlywhatwaswanted,guidedandmonitoredbytheartisans'guildsandbytheelectedcouncilrepresentativeswhohelpedoverseetheirrelationswithlocalindustry,especialyapprenticeshipschemes.`CityandGuilds'examinations,grantingcertificatesanddiplomas,weretheeducationalcurrencyoftheseself-organisededucationalsystems,andtheycontinueduntilthe1960s.

Theywerethelabelsthatqualifiederstwhilelabourersasartisans,worthyofrespectbytheirpeers.

Thispulingyourselfupbyyourbootstrapsintorespectablecitizenshipcontrastswiththeattitudetoelectedlocalcouncilmenbytheuniversitiesthattheseorganisationsmaturedinto.Liketheancientuniversities,newoneslikeBirminghamandManchesterrewardedlocalelecteddignitaries,mayors,andcouncilorswithhonorarydegrees.Theseemptytitles,contrastingbothwiththeearnedcertificatesoftheartisansandwiththehonorarydegreesgiventoeminentscholarsinrecognitionandrespect,ensuredapoliticalalegiance-anddevaluedacademiaingeneral.

Unfortunately,theprofusionofsuchyounguniversitiesinlatetwentieth-centuryEnglandhasmeantthatnon-technical,evennon-scientificsubjectshaveagainbecomefashionable,totheexclusionofthatartisaneducationwhichwassohealthyinlateVictoriantimes.Thedevaluationofacademicdegreesofalkindshascontinuedapace,butatthesametimethealternativeandmoreworthyroutestoself-advancementhaveatrophied.

Doesthismatter?

Indeeditdoes.PerhapsOwenHarry,whohadhimselfrisenfromapoorWelsh

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beginningnearCardiffsTigerBaytobecomeaveryyoungchieftechnicianinJack'szoologydeptatBirminghamUniversity,andlaterbecameaseniorlectureratBelfastUniversity,putthisbestwhenhedescribeditsmainnegativeconsequenceasàlackofsergeants'.

ThereisastoryaboutofficertrainingandexaminationintheBritishArmyinthe1950s.Oneofthemostimportantquestionswas'Howdoyoudigatrench?'.ThecorrectanswerwasÌsay"Sergeant,digmeatrench!"'

Sergeantsarepeoplewhoorganisethedoing.Theyarenotexpertsinwhattodo,orwhen:that'stheprerogativeofofficers,whotheoreticalyconstitutethebrainsoftheorganisation.Officersdecidewhathastobedone,butdon'tknowhowtodoit.Sergeantsdon'tactualydothings,either,exceptoccasionalywhentheyhaveto.Theirroleistoorganisesquadsofignorantmen,oftenincompetent,butweltrainedtoobeyorders,sothattheycooperateeffectively.Sergeantsarethelayerthatmakescooperationeffective:theyknowhowtogetthingsdone.Privatesknowhowtodowhatthey'retold,andaretrainednottodoanythingelse.

Wedidn'tsayefficient;it'sacommonmistaketoseeefficiencyassomethingtobestrivenfor.Efficiencyisaconceptborrowedfromengineeringandphysics,ameasureofhowmuchyougetoutforhowmuchyouputin.Sergeantsareinsomerespectstheleastefficientwayofgettingthingsdone;theyhaveatendencytowardsrepetitionandsarcasm,confidentthatafewoftheirrecruitswilgraduatefrombasictrainingwithsomedegreeofcompetence.Butsergeantsareveryeffective,andthesystemtheyarepartofisveryrobust.

DarwinandWalace,SpencerandWels,alcameupthroughasystemthatwasveryrobustinthisway.Alofthem,differentastheywere,knewthatwritingbookswasaprimewayofaffectingthesocietyaroundyou.

Therewasnotelevision,nofilms,andonlyafractionofpeoplewenttothetheatreortheopera...mostlytomusichalandpantomimesaroundChristmas.Dickens,Kingsley,theBrontesisters,andThomasHardymadepeople-lotsofpeople-thinknewthoughtsandleadnewlives.Theworkingmen'sclubsandtheirlinkswiththepubliclibrariesbroughtreadingskilstoahigherlevelthaneverbefore.

Sothisaudiencewasripeforpersuasivetextsthatcouldtakethemoutofsimple

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biblicalknowledgeintonewtheologies,evenintoatheism.Huxley,`Darwin'sBuldog',promotedDarwinismastheantithesisofaGod-madeworld.FromtheaspiringmiddleclassofVictorianagrewourmodernsecularage,withGodrelegatedtotheplaythingofafewofthelessmodernclergy.Modernclergydon'tbelieveinatwelve-footEnglishmanupthereinthesky,withHeavenasaneternalBuckinghamPalacegardenparty.ParticularlyfromthoseFrenchphilosopherswhocontinuedsophisticatedtheologicalcriticisminlineagesderivedfromVoltaire,ourclericslearnedtodowithoutthatstrongVictorianstyleofChristianity.ThatformofAnglicanism,confidentthatGodrealywaslookingaftertheEnglish,didn'tneedtoembarrassitselfwithovertprayers.Theritualswouldsuffice(providedtheyweren'tnoisyliketheWelsh,orshowyliketheCatholics).

Wehaveloststrongsimplereligion,wehavelostacademicexcelence,wehavegainedasecularsocietythatmaintainstheheterogeneitythatmadeitsorobustinVictoriantimesandlater.However,wearenowpursuingpolicies,particularlyineducation,thatfailtoprovidesocietywithalthoseablepeoplewhobuilttheVictorianandEdwardianedifices,bothmaterialandtheoretical.

Thereareroutesawayfromthispessimism.InTheScienceofDiscworld2

wereferredtohumansasPannarrans,thestorytelingchimpanzee.Ouroveralmessagewasthathumansneedtomakestoriestomotivatethemselves,toidentifygoals,andtodistinguishgoodfromevil.

Herewegoastepfurther.

TechnologicalandCivilisedMan,webelieve,mustbecomePolypanmultinarrans,[1]toextendthemetaphorratherfurther.Humanbeingsmustbecomeevermorediverse,valuingandenjoyingeachother'sdifferencesratherthanfearingthemorsuppressingthem.Andmereexplanationisnotenough.Togainunderstanding,ausefulworkingphilosophyasappropriateforactionasforjudgementand[1]Sorry,it'soneofthosehorribleGraeco-Latinhybrids.But,likètelevision',it'scomprehensible.

decision,anexplanationisonlyrarelygoodenough.Peoplefindsimpleexplanationssatisfyingbecausetheyenablethincausalchainsofthekindwebuildforourownpersonalmemoriesandcausalities.Buttherealworld,eventheworldofotherpeopleandtheirlikes,dislikes,andprejudices-sometimesso

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rigidlyheldthatourownlivesandthoseofourlovedonesdon'tmattertothem-doesn'tworklikethat.

Weoweittoourselves,andtothoseforwhomweareresponsibleandthosewhorespectus,todevelopmulti-causalunderstanding.Wecandothat,assuggestedhere,bysimultaneouslyencompassingseveralexplanationsofeachpuzzle,explanationsthatdisagreeproductivelywitheachother.Multinarrans:manystories.Sooneperson,evenaNewtonoraShakespeareoraDarwin,wilnotrealybeenough,despitethestorywehavejusttoldyou.OurfictionalDarwinisasymbolforanendlessstreamofDarwins,chalengingorthodoxyandbeingright,agloriousnetworkofinnovativethinkersandradicals.Peoplewhotrytokeepancientculturesalivebyblowingupthecompetitionachievenothing,exceptwidespreadcontemptfortheirobjectives.Theydoomtheirownenterprisebytheirmethods,andtheybetrayaterriblelackofconfidencethatwhatmatterstothemcansurvivewithoutcoercionandviolence.

Backtosergeants,andthewaythingsarerealydone:`Sergeant,digatrench.'ThisishowPolypanmultinarransgetsthingsdone.Howmanypeopleareneededtounderstandajetairliner?Tobuildone?Recursionintechnologyrealyislikebiologicalevolution,itrealydoesexpandthephasespace.Itexpandsitsomuchthatmostofushavevirtualynounderstandingofhowtheworldweliveinworks.Infact,itisessentialthatwedon't,becausetherewouldbetoomuchforanyonetounderstand.

Butwedoneedtounderstandthatthisiswhattheworldislike.Otherwisewedon'tjustlosethesergeants:welosetheabilitytobuildaircraftthatfly,dishwashersthatclean,carsthatdon'tpolute(asmuch).Westopbeingabletocure(someof)thesick,tofeed(mostof)theplanet,andtohouse,clothe,andwashaburgeoninghumanity.

Ourworldischanging,andit'schangingveryfast,andweourselvesaretheinescapableagentsofthatchange.Ifwestagnate,likeourfictionalVictoriana,wedie.Stayingwhereweareisnotanoption.Staticresourcescannotcontinuetosupportus.

Wemakeourworldworkbyintroducingnew,undreamt-ofrulesandpossibilities,byconsideringalternativesandmakingdecisions,whichfeellikèfreewil',andworkthatway,eveniftheyarèrealy'deterministic.Webuildonthepresenttocreateabiggerfuture.Sciencestandingontechnology,and

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technologystandingonscience,provideasuccessfulladderthatleadstoexteligence.

Isit,perhaps,theonlyone?

Thepastwasanothercountry,butthefutureisanalienworld.

Andyet...

Themostremarkablethingabouttheuniverse,asEinsteinoncesaid,isthatitiscomprehensible.Notineveryaspect,butinenoughtomakeusfeelathomeinit.Itmakessense-almostasmuchasaDiscworldstory.

Whichisamazingbecausefactsdon'thavetomakesense:onlywel-

craftedfictionhastoobeysuchrigidrules.

Partofthiscomprehensibilitycanbeexplained.Weevolvedintheuniverse,andweevolvedtosurviveinit.Beingabletotelourselves`whatifstoriesaboutit-tounderstandit-hassurvivalvalue.Wehavebeenselected,bynature,totelsuchstories.

Whatislesseasytoexplainiswhytheuniversecanberepresentedbyhumanstoriesatal.Butthen,ifitwasn't,wewouldn'tbetelingthem,wouldwe?

WhichbringsusbacktoCharlesDarwin,architectofourownpresent,whichwashisfuture,andwouldsurelyseemalientoanyVictorian.InChapter18welefthimsittingonanèntangledbank',watchingbirdsandinsects,andmusingonthenatureoflife.ThefinalparagraphofTheOrigin,whichbeganwithgentlemusingsaboutentangledbanks,nowworksitswaytoitsrevolutionaryconclusion:

Fromthewarofnature,fromfamineanddeath,themostexaltedobjectwhichwearecapableofconceiving,namely,theproductionofthehigheranimals,directlyfolows.Thereisgrandeurinthisviewoflife,withitsseveralpowers,havingbeenoriginalybreathedintoafewformsorintoone;andthat,whilstthisplanethasgonecyclingonaccordingtothefixedlawofgravity,fromsosimpleabeginningendlessformsmostbeautifulandmostwonderfulhavebeen,andarebeing,evolved.

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TWENTY-FIVE,

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THEENTANGLEDBANK

ITWASMIDNIGHTINTHEmuseum'sCentralHalwhenthewizardsappeared.Therewereafewlightson;justenoughtoseetheskeletons.

Ìsthisatempleofsomekind?'saidtheChairofIndefiniteStudies,pattinghispocketsforhistobaccopouchandapacketofWizlas.Òneoftheweirderones,perhaps?'

+++Indeed+++boomedthevoiceofHexfromthemiddleair.

+++InaltheuniversesoftheTheOlogy,itwastheTempleoftheAscentofMan.Here,itisnot+++

`Veryimpressive,'mutteredtheDean.`Butwhydon'twejustshowhimthebigsnowbal?He'dbeprettypleasedtoknowitwasbecauseofhimhumansgotaway.'

`We'vescaredthepoorchapenough,that'swhy!'snappedRidculy.`He'lunderstandthis.HexsaystheystartedbuildingwhenDarwinwasalive.

Stuffedanimals,bones...it'sthekindofthingheknows.Nowstandbackandgivethechapsomeair,wilyou?'

TheysteppedawayfromthechaironwhichCharlesDarwinhadbeentransported,wreathedinthebluelight.Ridculysnappedhisfingers.

Darwinopenedhiseyes,andgroaned.

Ìtneverends!'

`No,we'resendingyouback,sir,'saidRidculy.`Thatis,you'lsoonwakeup.Butwethoughtthereissomethingyoushouldseefirst.'

Ì'veseenenough!'

`Notquiteenough.Lights,gentlemen,please,'saidRidculy,straighteningup.

Lightistheeasiestmagictodo.Aglowroseinthehal.

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`TheMuseumofNaturalHistory,MrDarwin,'saidRidculy,standingback.

Ìtopenedafteryourdeathatavenerableage.It'syourfuture.Ibelievethereisastatuetoyouheresomewhere.Placeofhonour,nodoubt.

Pleaselisten.Iwouldlikeyoutoknowthatbecauseofyou,humanityturnedouttobefitenoughtosurvive.'

Darwinstaredaroundatthehal,andthenlookedaskanceatthewizards.

`Thephrase"survivalofthefittest"wasnot-'hebegan.

`Survivaloftheluckiestinthiscase,Ifear,'saidRidculy.`Youarefamiliarwiththeideaofnaturalcatastrophesthroughouthistory,MrDarwin?'

Ìndeed!Oneonlyhastoexamine-'

`Butyouwilnothaveknownthattheywipedinteligentlifefromthefaceoftheglobe,'saidRidculy,sombrely.`Sitdownagain,sir...'

Theytoldhimaboutthecrab-likecivilisation,andtheoctopus-likecivilisationandthelizard-likecivilisation.Theytoldhimaboutthesnowbal.

[1]

Darwin,Ponderthought,boreupwel.Hedidn'tscreamortrytorunaway.

Whathediddowas,inaway,worse:heaskedquestions,inaslow,solemnvoice,andthenaskedmorequestions.

Strangely,hekeptawayfromoneslikèhowdoyouknowthis?'and`howcanyoubesosure?'.Helookedlikeamananxioustoavoidcertainanswers.

Forhispart,MustrumRidculyverynearlytoldthewholetruthonseveraloccasions.

AtlastDarwinsaid,ÌthinkIsee,'inatoneoffinality.

Ì'msorrywehadto-'Ridculybegan,butDarwinheldupahand.

[1]SeeTheScienceofDiscworldandTheScienceofDiscworld2

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'Idoknowthetruthofalthis,'hesaid.

`Youdo?'saidRidculy.`Realy?'

Ìndeed,afewyearsagotherewasaratherpopularnovelpublished.AChristmasCarol.Didyoureadit?'

Ponderlookeddownatthehithertoblankpieceofpaperonhisclipboard.

Hexhadbeentoldtobequiet;CharlesDarwinwasprobablynotintherightframeofmindforboomingvoicesfromthesky.ButHexwasresourceful.

`ByCharlesDickens?'saidPonder,tryingnottolookasthoughhewasreadingthewritingthathadsuddenlyfiledthepage.`Thestoryoftheredemptionofamisanthropeviaghostlyintervention?'

`Quiteso,'saidDarwin,stilspeakinginthecareful,woodenvoice.Ìtiscleartomethatsomethingsimilarishappeningtome.Youarenotghosts,ofcourse,butaspectsofmyownmind.Iwasrestingonabanknearmyhome.Ihadbeenwrestlingatlengthwithsomeoftheperturbingimplicationsofmywork.Itwasawarmday.Ifelasleep,andyou,andthat...god...andalthis,areakindof...pantomimeinthetheatreofmybrainasmythinkingresolvesitself.'

Thewizardslookedatoneanother.TheDeanshrugged.

Ridculygrinned.`Holdontothatthought,sir.'

ÀndIfeelsurethatwhenIawakeIwilhavereachedaresolve,'saidDarwin,amanfirmlynailinghisthoughtsinorder.Ànd,IferventlytrustIwilhaveforgottenthemeansbywhichIdidso.Icertainlywouldnotwishtorecalthewheeledelephant.Orthepoorcrabs.Andasforthedirigiblewhale...'

`Youwanttoforget?'saidRidculy.

Òh,yes!'

`Sincethatisyourclearrequest,Ihavenodoubtitwilbethecase,'saidRidculy,glancingquestioninglyatPonder.Ponderglancedattheclipboardandnodded.Itwasadirectrequest,afteral.Ridculywas,Pondernoted,quitecleverunderalthatshouting.

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Apparentlyrelievedatthis,Darwinlookedaroundthehalagain.

"ÌdreamtIdweltinmarblehals",indeed,'hesaid.

Thewords`ReferencetoapopularsongwrittenbyMichaelW.Balfe,manageroftheLyceumTheatre,London,in1841'floatedacrossPonder'sclipboard.

Ìdon'trecognisesomeoftheseveryimpressiveskeletons,'Darwinwenton.`ButthatisRobertOwen'sDiplodocuscarnegii,clearly...'Heturnedsharply.

`Humanitysurvives,yousay?'hesaid.Ìtrodeouttothestarsontamedcomets?'

`Somethinglikethat,MrDarwin,'saidRidculy.Ànditflourishes?'

`Wedon'tknow.Butitsurvivesbetterthatitwouldunderamileofice,Isuspect.'

Ìthasachancetosurvive,'saidDarwin.

Èxactly.'

Èvenso...totrustyourfuturetosomefrailcraftspeedingthroughtheunknownvoid,preytounthinkabledangers...'

`Thatwaswhatthedinosaursdid,'saidRidculy.Àndthecrabs.Andaltherestofthem.'

Ìbegyourpardon?'

Ìmeantthatthisworldisaprettyfrailcraft,ifyoutakethelongview.'

`Ha.Nevertheless,somevestigeoflifesurelysurviveseverycatastrophe,'

saidDarwin,asiffolowingatrainofthought.`Deepunderthesea,perhaps.Inseedsandspores...'

Àndisthathowitshouldbe?'saidRidculy.`Newthinkin'creaturesarisin'

andbeingforeversmasheddown?Ifevolutiondidn'tstopattheedgeofthesea,whyshoulditstopattheedgeoftheair?Thebeachwasonceanunknownvoid.Surelytheevidencethatmankindhasrisenthusfarmaygivehimhopeforastil

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higherdestinyinthedistantfuture?'

Ponderlookeddownathisclipboard.Hexhadwritten:heisquotingDarwin.

Àninterestingthought,sir,'saidDarwin,andmanagedasmile.Àndnow,Ithink,Irealyshouldliketoawaken.'

Ridculysnappedhisfingers.

`Wecangetridofthosememories,can'twe?'hesaid,astheblueglowenvelopedDarwinyetagain.

Òhyes,'saidPonder.`He'saskedusto,soit'sethicalycorrect.

Weldone,sir.Hexcanseetoit.'

`Welthen,'saidRidculy,rubbinghishands.`Sendhimback,Hex.

Withperhapsjustatinyrecolection.Asouvenir,asitwere.'Darwinvanished.'Jobdone,gentlemen,'saidtheArchchancelor.

Àlthatremainsnowistogetbackfor-'

`WeoughttomakesuretherearenomoreAuditorsleftonRoundworld,sir,'saidPonder.

Ònthatsubject-'Rincewindbegan,butRidculywavedhimaway.`Thatatleastcanwait,'hesaid.`We'veestablishedthetimeline,it'sniceandstable,andwecan-'

Èr,Idon'tthinktheywanttowait,sir,'saidRincewind,backingaway.

ShadowswerepouringintotheCentralHal.Overthedoublestaircase,acloudwasforming.ItlookedlikethegreyrobeofanAuditor,buthugelybigger,andasthewizardswatchedthegreynessdarkenedtocoal-mineblack.

Thebloatedshapedriftedforward,whilehundredsmoreoftheemptygreyrobescontinuetomergewithit.

ÀndIthinkthey'reabitangry,'Rincewindadded.

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Trailinggreynessafterit,filingthehalfromedgetoedge,theAuditorboredownonthewizards.

`Hex-'Ponderbegan.

`Toolate,'boomedtheAuditor.'Wehavecontrolnow.Nomagic,noscience,nochocolate.Wehavetothankyouforthisplace.Neverwasthereaspeciessodeterminedtodestroyitself.Inthisworld,wecanwinwithouttrying!Doyouknowthewarsyou'veunleasheduponthistoyworld?Theplagues,thefamine,thewholescienceofdeath?Areyounotashamed?'

`What'shetalkingabout,Stibbons?'saidRidculy,nottakinghiseyesoffthecloud.

`Thereareanumberofwarsinthenextcoupleofhundredyears,sir,'saidPonder.`Bigones.'

`Darwin'sfault?

'Er,sir.'

`Just"er",Stibbons?'

`"Er"isaverypreciseterminthiscontext,sir.Itmeanswedon'thavetimeforabigdebate.ButcertainlythewarsarebiggerandmorefrequentthantheonesthattookplaceintheworldofTheOlogy.'`Badthing,then?'saidRidculy,wholikedhisphilosophysuccinct.Èragain,sir,I'mafraid,'saidPonder.

`Caretoexpand?'

Ìnshort,sir,morepeoplewildieinwars,farfewerwildieofdiseaseandmedicalproblemsofalkinds.Andhumanitysurvivesthesnowbal.Thefirsthumanslefttheplanetinconvertedweaponsofwar,sir.'

`That'smonkeysforyou,Stibbons,'saidRidculy.HelookedupatthecloudofpureAuditor.

`No,we'renotashamed,'hesaid.`Humansgetachancetogoon.'`Theywon'thaveearnedit!'

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`Strangethatthisconcernsyou,'saidRidculy.

`Doyouknowtheterrorsthatwilconfrontthem?'theAuditordemanded.

Àndtheterrorsthattheywilbringwiththem?'

`No,butIdoubtifthey'reworsethattheonesthey'vemetalready,'saidRidculy.Ànyway,youdon'tcareaboutthem.Youjustwantthemtodiequietly.Don'tyou?'

TheAuditorshimmered.PonderwonderedhowmanyAuditorshadcometogethertocreateit.Itseemed,now,tobehesitant,unsureItsaid:Ìwant...I...'

...andexplodedintofogwhich,itself,fadedaway.

`Notlearnedquiteenough,then,'saidRidculy,andsniffed.`Wel,let'ssendDarwinbackandgohome,shalwe?I'msurewe'vemissedatleastonemeal.Where's·Rincewind?'

+++HidingintheMineralsGalery+++saidHex.

Ìmpressive.Ididn'tevenseehimmove.Ohwel,Idaresayyoucanpickhimuplater.Let'sgo.'

`Whatdiditmeanbytheterrorstheybringwiththem?'saidtheDean.

`Wel,they'restilmonkeys,'saidRidculy.`Stilscreamingatoneanother,trailingalthatevolutionbehindthem,wherevertheygo.'`Darwinsaidsomethinglikethat,sir.InTheDescentofMan,'saidPonder.

`Goodchap,Darwin,'saidRidculy.`Wouldhavemadeagoodwizard.'

`Didyouknowtheyputhisstatueinthecanteen,sir?'saidPonder,alittleshocked.

`Didthey?Goodidea,'saidRidculybrusquely.`Thatway,everysensiblepersonseesit.Ready,Hex.'

AndtheCentralHalwasemptyagain,apartfromthefossils.

CharlesDarwinawoke.Foramomentsobriefthatablinkendedit,therewasa

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senseofcompletedisorientation.Butthenhesatup,feelingunaccountablyexhilarated,andlookedaroundatthetangled,busybank,withitsbirdsandflittinginsects,andthought:Yes.That'sright.That'showitis.

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AFTERTHOUGHT

TheDarwinfamilymotto:

caveetaude.

Watch,andlisten.


GURPS Discworld Also

GURPS Discworld Also

Spanish Discworld Game traducción

Spanish Discworld Game traducción

Shel silverstein no media

Shel silverstein no media

Discworld gods - Wikipedia, the free encyclopedia.pdf

Discworld gods - Wikipedia, the free encyclopedia.pdf

Discworld and Time-Lord Uni Special

Discworld and Time-Lord Uni Special

Selling Terry Pratchett's Discworld: Merchandising and the Cultural ...

Selling Terry Pratchett's Discworld: Merchandising and the Cultural ...

GURPS - Discworld - Role-Playing Game

GURPS - Discworld - Role-Playing Game

Subversions - The Discworld Novels of Teny Pratchett

Subversions - The Discworld Novels of Teny Pratchett

Shel Silverstein. Poetry

Shel Silverstein. Poetry

Subversions : The Discworld novels of Terry Pratchett

Subversions : The Discworld novels of Terry Pratchett

Shel Silverstein’s

Shel Silverstein’s

Shel Silverstein Poems - j.b5z.netj.b5z.net/i/u/2106388/f/PAPShelSilversteinPoems.pdf · Shel Silverstein Poems 1 MAGIC Sandra’s seen a leprechaun, ... Shel Silverstein Poems 5

Shel Silverstein Poems - j.b5z.netj.b5z.net/i/u/2106388/f/PAPShelSilversteinPoems.pdf · Shel Silverstein Poems 1 MAGIC Sandra’s seen a leprechaun, ... Shel Silverstein Poems 5

Shel Silverstein - Falling Up

Shel Silverstein - Falling Up

Introduction to Discworld (demonstration of vocal variety)

Introduction to Discworld (demonstration of vocal variety)

Discworld legacy 21 looking back, looking forward

Discworld legacy 21 looking back, looking forward

SSH - Secure SHel l

SSH - Secure SHel l

The Discworld Mapp - Terry Pratchett and Stephen Briggs

The Discworld Mapp - Terry Pratchett and Stephen Briggs

3245604 New Discworld Companion Ver 2 Corrected

3245604 New Discworld Companion Ver 2 Corrected

Ribono shel olam - ShulCloud

Ribono shel olam - ShulCloud

SHEL PERKINS TALENT IS

SHEL PERKINS TALENT IS