Caltech_Fall2010

8/3/2019 Caltech_Fall2010

1/48

Volume lXXI I I , Number 4, FAll 2010

N ThIs Issue:

Volcanoes and Earthquakes Zombies and Celebrities

Aggression and Fruit Flies

California Inst i tute of Technology
http://www.caltech.edu/http://www.caltech.edu/


2/48

Engineering & Scienceis printed on recycled paper contain

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pulp comes from trees grown in the U.S. in accordance wit

Forest Stewardship Councils sustainability standards.

Tedx CalTeChJan uary 14, 2011

on the co

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http://tedxcaltech.com/http://dmse.mit.edu/faculty/faculty/belcher/https://researcher.ibm.com/researcher/view.php?person=almaden-eiglerhttps://researcher.ibm.com/researcher/view.php?person=almaden-eiglerhttp://www.ericjhellergallery.com/http://marcuslab.harvard.edu/http://www.jazzreview.com/articledetails.cfm?ID=655http://www.youtube.com/watch?v=TVyyhHFKI8Ehttp://www.bias-inc.com/about/artistProfiles/bRice.phphttp://susskindsblogphysicsforeveryone.blogspot.com/http://susskindsblogphysicsforeveryone.blogspot.com/http://www.sdss.jhu.edu/~szalay/http://www.sykes.easynet.co.uk/http://www.jcvi.org/cms/about/bios/jcventer/http://www.jcvi.org/cms/about/bios/jcventer/http://theory.caltech.edu/~preskill/http://theory.caltech.edu/~preskill/http://www.its.caltech.edu/~kip/http://www.ted.com/speakers/rives.htmlhttp://tedxcaltech.com/http://tedxcaltech.com/http://www.ted.com/speakers/rives.htmlhttp://www.its.caltech.edu/~kip/http://theory.caltech.edu/~preskill/http://www.jcvi.org/cms/about/bios/jcventer/http://www.jcvi.org/cms/about/bios/jcventer/http://www.sykes.easynet.co.uk/http://www.sdss.jhu.edu/~szalay/http://susskindsblogphysicsforeveryone.blogspot.com/http://susskindsblogphysicsforeveryone.blogspot.com/http://www.bias-inc.com/about/artistProfiles/bRice.phphttp://www.youtube.com/watch?v=TVyyhHFKI8Ehttp://www.jazzreview.com/articledetails.cfm?ID=655http://marcuslab.harvard.edu/http://www.ericjhellergallery.com/https://researcher.ibm.com/researcher/view.php?person=almaden-eiglerhttps://researcher.ibm.com/researcher/view.php?person=almaden-eiglerhttp://dmse.mit.edu/faculty/faculty/belcher/http://tedxcaltech.com/


3/48

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VoluMe lXXI I I , nuMBer 4, Fall 2010

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B aw y I Zmbiby andrew porterfield

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http://eands.caltech.edu/http://eands.caltech.edu/


4/48

ENGINEERING & SCIENCE fall 20102

In a marriage o brute orce and milli-

metric precision, a vital communica-

tions link in the Deep Space Network

has just undergone a major repair. The

giant Mars dishso named because

its rst job, in 1966, was to track

Mariner 4 ater its fyby o the redplanethas relayed commands to,

and data rom, every earthly emissary

to have ventured beyond the moon.

As the most sensitive antenna avail-

able, it was also crucial in bringing the

Apollo 13 astronauts home. But 44

years o operationmore than double

its projected 20-year liespanhave

taken a toll on the bearings that allow

it to aim its radio beam precisely at a

spacecrat the size o a VW Beetle

more than 10 billion kilometers away.

Ocially known as Deep Space

Station 14, the 70-meter antenna sits

in a shallow valley at JPLs Goldstone

complex deep in the Mojave des-

ert between Los Angeles and Las

Vegas, where it is shielded rom as

many o humanitys interering radiosignals as possible. The dish and its

substructure, including the two-story

corrugated steel building that houses

the drive motors and some o the

signal-processing equipment, weighs

about 3,000 metric tonsmore than a

herd o 500 elephants.

The entire assembly, as tall as a

20-story building, rests on three steel

support pads. These pads are part o

the hydrostatic bearing on which the

antenna rotates, and they glide on

a quarter-millimeter lm o oil atop a

24-meter-diameter steel ring called

the runner. The runner, in turn, sits on

a 10-meter-tall pedestal. Tiny trickles

o oil would seep through the runners

joints and drip o its edges, deterio-

rating the cement-based grout below.As the grout sotened, the runner

would develop waves, so a team o

our technicians would spend eight

to 10 hours a week inserting shims

under the runner to keep it level.

Work began in March to replace

the runner, the grout, and the eleva-

tion bearings that allow the dish to

tilt rom the zenith to the horizon. The

elevation bearings were done rsta

sort o warm-up job, as this merely

involved liting 1,800 tons o dish o

its mounting. Next, the crew usedthe same hydraulic jacks to raise the

entire 3,000-ton colossus ve milli-

metersenough clearance to ease

out the old components and install

a thicker runner with tighter joints on

new oil-resistant, epoxy-based grout.

As it talks to ar-fung spacecrat,

the Mars dish also measures the

distance to them, providing vital data

to the navigation teams. Changing the

dishs height by more than a ew milli-

meters would void these calculations.The new runner is seven inches thick

to the old runners ve, so, in one nal

engineering challenge, the hydrostatic

bearing pads had to be removed and

machined down to compensate.

The project, two years in the

planning, had a set-in-cement

deadline: the dish had to be back on

line by early November, in time or

JPLs rendezvous with comet Hartley

2. They made it. MW/DS

random walk

operation: mars antenna
http://deepspace.jpl.nasa.gov/dsn/http://deepspace.jpl.nasa.gov/dsn/features/goldstonetours.htmlhttp://deepspace.jpl.nasa.gov/dsn/features/goldstonetours.htmlhttp://deepspace.jpl.nasa.gov/dsn/features/goldstonetours.htmlhttp://deepspace.jpl.nasa.gov/dsn/features/goldstonetours.htmlhttp://deepspace.jpl.nasa.gov/dsn/


5/48

fall 2010 ENGINEERING & SCIENCE

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http://www.nasa.gov/mission_pages/epoxi/index.htmlhttp://www.nasa.gov/mission_pages/epoxi/index.html


6/48


Having a Blast

In 2007, soon ater landing at Naha

Airport on the island o Okinawa in

Japan, a Boeing 737 started spewing

uel rom a puncture in its right-wing

tank. As the uel fowed onto the hot

engine, it ignited, causing several ex-plosions as fames enguled the plane.

Fortunately, everyone evacuated in

time and no one was hurt.

O course, planes, trains, and

automobiles dont generally burst

into huge reballs whenever theyre

near a heat source, whether it be a

spark or a lit cigarettedespite what

Hollywood might lead you to believe.

But clearly, exploding uel is a hazard,

and understanding how it ignites al-

lows engineers to develop the proper

saety regulations to minimize danger.Postdoc Sally Bane (PhD 10),

working with Joe Shepherd (PhD 81),

Johnson Proessor o Aeronautics and

proessor o mechanical engineering,

is analyzing how a spark can ignite

fammable gas. Shes discovered that

these spark-ignited explosions are a

lot more complicated than previously

thought, and her results bring much-

needed updates to saety standards

that are decades oldand, in some

cases, based on data that are fat-outwrong.

For decades, engineers have

determined the likelihood o a spark-

ignited explosion in an aircrat by

using a number called the minimum

ignition energy (MIE). Each type o

uel or vapor has its own MIE value,

and i a sparks energy is below that

value, then nothing should ignite. The

problem, however, is that the MIE is

based on data rom old experiments,

some rom more than 60 years ago.

Even though the numbers have been

updated over the years, no one has

ever gone back and reevaluated the

original experiments in depth. The

original data rom the 1940s are still

cited today, Bane says.

As an expert in explosions, Shep-

herd was recruited in 1996 by the

National Transportation Saety Boardto help gure out why TWA Flight

800 crashed into the Atlantic just 12

minutes ater takeo rom New Yorks

JFK Airport (see Learning rom a

Tragedy, E&SNo. 2, 1998). During

the investigation, some o Shepherds

experiments showed unoreseen vari-

ability in spark-ignited explosions

even with a spark below the MIE, the

uel sometimes still blew up. However,

he didnt get a chance to explore the

issue urther until Bane came to his

lab as a graduate student in 2005.According to Bane, perorming

this kind o experiment is dicult and

time-consuming, and since there

hadnt been any obvious reason to

doubt the old MIE data, people were

content with the existing inormation.

It took her ve years to design, build,

and run her experiments, which are

among the most rigorous ever done.

Her explosions range rom harmless

pus to tiny reballs, saely contained

in a solid-steel vessel weighing 200kilograms. Inside the vessel are two

pointy tungsten electrodes, separated

by a couple o millimeters. Charge

builds up in the electrodes, generat-

ing a voltage dierence that ionizes

the gas between them. The ionized

gas creates a path or electrons to

travel rom one electrode to the other,

and in just a ew nanoseconds, you

get a spark. The spark energies that

Bane works with are relatively low

as low as 50 microjoules. You would

need a million o these sparks to light

a 50-watt lightbulb or a second.

A high-speed camera, which can

take up to several hundred thousand

rames per second, records the spark

and any resulting explosion. Bane

repeated the experiment or dierent

spark energies and with various mix-

tures o fammable gases as suggest-ed by the Aerospace Recommended

Practices, standards developed by

the Society o Automobile Engineers

that guide the design and production

o aircrat parts. The mixtures con-

tained 5, 6, or 7 percent hydrogen,

oxygen, and argon.

Unlike tests that are common in the

industry, Banes are done in a sealed

vessel, which means that she knows

the gass composition, temperature,

and pressure with a high degree o

certainty. Furthermore, Bane says, inother setups, theres no camera that

directly observes the ignition. Instead,

the only way to tell that theres been

an explosion is to watch whether a

piece o oil, which is across an open-

ing in the vessel, pops upor, i the

blast is violent enough, bursts open.

Bane discovered that there isnt a

single MIE value or a given famma-

ble mixture; theres no single energy

that sets the threshold or whether

an explosion is possible. Instead,she ound, whether or not a certain

spark ignites the gas is an exercise

in probabilities, rising and alling with

the energy o the spark. To be sure, at

some point, the energy is too low and

an explosion is impossible. But its

not as cut and dried as people had

thought.

In the case o the 7 percent

hydrogen mixture, Banes results

were roughly comparable to the
http://www.galcit.caltech.edu/~jeshep/http://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://eands.caltech.edu/articles/Shepherd%20Feature.pdfhttp://www.galcit.caltech.edu/~jeshep/


7/48


Fr lf: t frm of fr nulfd Bon

737 wn lkn ful w nd by o nn.

Forunly, no on w ur.

Lf: a rk bwn wo ony lcrod n

7 rcn ydron mxur, nrn frbll.

i no dnrou look xloon

mll. For comron, dnc bwn

lcrod only fw mllmr. t no r

kn 5, 50, 100, 175, nd 250 mcrocond.

experiments done by Bernard

Lewis and Guenther von Elbe in the

1940s, which gave an MIE o 100

microjoules. She ound that at 100

microjoules, the gas had a 10 percent

chance o igniting. But or the 5 per-

cent hydrogen mixture, the MIE given

was 200 microjoules, while Bane

determined that the spark had to be

at least 780 microjoules beore it evenhad a 10 percent chance o blowing

up. It turned out that Lewis and von

Elbe hadnt actually had data or a 5

percent hydrogen mixture back in the

1940sthey had just extrapolated

the MIE rom data or the 7 percent

gas.

This variability is likely an inherent

characteristic o spark ignition, Bane

says. Even when she kept the condi-

tions as constant as possible, the

explosions were never consistent. The

spark itselthe channel o plasmaconnecting the two electrodesis

intrinsically irregular, wavering in

shape and motion. Other complexities

have been revealed in fuid-dynamic

simulations that Bane and graduate

student Jack Ziegler have run o the

ignition process.

Bane and Shepherd are now work-

ing to develop better saety stan-

dards with Boeing, which unded the

research. Last summer, she expanded

her experiments to include kerosene,the type o uel used in most com-

mercial aircrat. Unlike clean-burning

hydrogen, kerosene is a dirty uel, so

ater each trial, Bane dons a protec-

tive jacket, Kevlar gloves, and goggles

beore opening the hot vessel to

swab out the soot and set up the next

experiment.

Bane is nding that it doesnt take

much energy to set o kerosene.

She was able to ignite kerosene at

60 degrees Celsius with only 0.65

microjoules, while in Shepherds

previous work, it took 40 microjoules

to ignite the uel at 52 degrees. I

anticipate that in uture tests Ill be

able to ignite mixtures with even lower

energies, she says. The ignition o

uel vapor is highly sensitive to tem-

perature change, Bane explains, and

her experiment used shorter-durationsparksabout a couple hundred

nanoseconds, which is a more ac-

curate simulation o an electrostatic

dischargeso the discrepancy isnt

a complete surprise. But the act that

its apparently much easier to ignite

kerosene than the test mixtures speci-

ed by the FAA has certainly gotten

the attention o the olks at Boeing.

Bane says her data can be applied

to any situation where theres a tank

o uel and the possibility o a

sparkor example, in power plants,in the natural-gas tank that heats your

house, or when storing hydrogen gas,

which has garnered interest as a

clean-burning uel. But as or

smoldering cigarettes blowing cars to

kingdom come? That could never

happen, Bane says. Gasoline needs

to be extremely hot to ignite, and a

cigarette just wont cut it. But it sure

looks cool. MW

Wc slly Bn dcu r

work r of 2010 evrr

Lcur sr.
http://today.caltech.edu/theater/item?story_id=44862http://today.caltech.edu/theater/item?story_id=44862


8/48

a m of

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mn knw or

d rd bou

n 150 Cefrom

Cludu polmy

georphi.

ENGINEERING & SCIENCE fall 20106 ENGINEERING & SCIENCE fall 20106

on tHe map

From Neolithic cave painting to

Google Earth, humans have used

maps to depict, understand, and navi-

gate their environment. Now some o

the Caltech Archives nest treasures

on the subject o mapping the earth,the skies, and longitude have gone

on display, many or the rst time,

on the second foor o Parsons-

Gates Hall o Administration. The On

the Map exhibit includes Claudius

Ptolemys 2nd-century map o the

known world; Georg Braun and Frans

Hogenbergs beautiully illustrated

Civitates Orbis Terrarum, rom the

latter part o the 16th century; a 1570

map o Russia by Abraham Ortelius;

Johannes Bayers 1603 Uranome-tria; Johannes Keplers world map o

1627; a 17th-century planispheric

celestial map by Andries van Luchten-

berg; prints rom Joan Blaeus 1662

Atlas Maior; and rst editions o

books by Tycho Brahe, Johannes

Hevelius, Giovanni Domenico Cassini,

and Christiaan Huygens.

Ptolemys map is an early 16th-

century version reconstituted rom

his cartography and geography book,

the Geographia, published in 150

CE. Ptolemy, a Roman citizen o

Alexandria, knew that the earth was

a globethe ancient Greeks had

worked it out centuries earlierbut

his view o the world extends only

rom the zero-degree line o longitude

o the west coast o Arica (beyond

which no sailor had returned to tellthe tale) to the 180-degree line

through China, and rom 60 degrees

north latitude to 30 degrees south.

He omitted the three-quarters o

the globe that was still uncharted, a

technique that humans still employ

today when mapping unknown terrain

such as Saturns moon Titan, currently

under surveillance by JPLs Cassini

spacecrat. Cassinis radar views

a narrow swath o Saturns lunar

companion with each fyby, and theresulting maps, in which Titans topo-

graphical eatures are interspersed

with black regions or which no data

exists, are in some sense Ptolemys

intellectual descendantsJPLs car-

tographers dont ll the empty space

with creations o their own ancy.

Cassini will, in all likelihood, map

Titan more rapidly than humans

mapped the earth: the Americas,

ater all, were not discovered by

Europe until the late 15th century.

But once the Age o Exploration got

under way, the exciting accounts o

new lands brought back by sailors

sparked a renewed interest in geogra

phy among prosperous and literate

Europeans. Printing presses, invented

a ew decades earlier, ound a lucra-

tive market in catering to the demandor inormation.

In 1513, the German cartographer

Martin Waldseemller, whose large

map o the world (and the rst map

to use the name America) had sold

well a ew years earlier, decided to

bring out Ptolemys Geographia. For

centuries the Christian world had

regarded the ancient geometer as

a heretic, and the work was hidden

away and orgotten until its rediscov-

ery in the 14th century. Waldseeml-ler borrowed a manuscript copy, in

Greek, rom an Italian monastery. The

maps were missing, but he reconsti-

tuted them, including the world map

in the Caltech display, rom Ptolemys

extensive topographical lista

compendium o place names and

geographical eatures along with their

latitudes and longitudes. (The list was

compiled rom travelers reports, and

many o the longitudes were wrong


9/48


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anyon comrn currn m of Bl w

1575 vw from Brun nd honbr Civies Orbis

terrrum(town of World) m nk

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or, at best, very bad guesseswhich

is why the landorms get increasingly

distorted the arther one gets rom the

Mediterranean.)

In the decades that ollowed, deco-

rative maps and atlases ound ready

buyers. Some o the nest were pro-

duced by the Flemish cartographer

Abraham Ortelius, who pioneered the

change rom the woodcut printing omaps to copperplate engraving, with

italic lettering and rich hand-coloring

that greatly enhanced the denition

and beauty o the prints. When his

Theatrum Orbis Terrarum (Theater o

the World), the rst true atlas, sold

well, he encouraged Georg Braun

and Frans Hogenberg o Cologne to

produce a companion book o town

views and history, the Civitates Orbis

Terrarum (Towns o the World).

With its rst volume published

in 1572, Braun and Hogenbergsambitious project took an additional

45 years to complete, and Caltech is

ortunate to own our volumes rom

the six-volume rst edition. Their

scrupulously detailed town plans

generally depict buildings and houses

rom a birds-eye perspective and

are brought to lie with drawings o

people in local costume carrying out

their trades, o animals, and o scenes

rom history, all accompanied by an

account in Latin o the towns situa-

tion, population, history, government,commerce, and traditions.

Today the armchair traveler has

morphed into the Google Earther,

as more and more people turn to

cyberspace to swoop in on houses

or the worlds cities. Interestingly,

Wikipedias city pages provide almost

the same inormation that Braun and

Hogenberg did.

Humans were likely curious about

the heavens even beore they ex-

plored the world: ollowing the daily

course o the sun, moon, stars, andplanets doesnt involve any traveling.

Early astronomers and geographers

both used the same surveying instru-

ments, such as quadrants and astro-

labes; and both earth and sky maps

have equators and poles, latitude and

longitude. (The longitude o a star or

planet is given by its right ascension,

while the latitude is given by its dec-

lination.) For millennia, star tables

celestial topographical listsplayed

an indispensible role in predictingimportant events in the calendar such

as equinoxes, solstices, phases o the

moon, and eclipses (not to mention

their use in casting horoscopes!), but

they were so imprecise that, accord-

ing to the young Tycho Brahe, There

are just as many measurements and

methods as there are astronomers,

and all o them disagree.

Accordingly, Tycho (as he is

commonly known), a Danish noble-

man, made it his lies work to take

accurate, systematic observations

rom a single spot over many years.

He persuaded King Frederick II oDenmark to give him the small island

o Hven (modern Ven), in the straits

between Denmark and Sweden, and

to build him an observatory there and

provide him with a generous income

to und it. Todays astronomers should

be so ortunate!

Tycho named his palatial astro-

nomical research center Uraniborg,

the Castle o the Heavens. With

accommodations or up to a hundred

observers, assistants, and visiting

scholars, it was not unlike a modernastronomical research center, save or

the alchemy workshop in the base-

ment and the utter lack o telescopes

(Tycho was the last major astronomer

to survey the skies entirely by naked

eye.) He later added Stjerneborg,

the Castle o the Stars, an under-

ground observatory with a rotating

dome that sheltered his instruments

rom the bueting winds that swirled

around Uraniborgs towers. A series

o lakes provided waterpower orboth instrument workshops and a mill

that produced paper or publications.

Unortunately, ater Fredericks death,

Tycho argued with his heir and had to

abandon the island in 1597.

Uraniborg, Stjerneborg, and the

lakes can be seen on the map o

Hven in the Archives displaya

reproduction o a colored engraving

by Willem Blaeu rom Joan Blaeus

Atlas Maior, 1662. The young Willem,


10/48

a m of tyco

Br lnd of hvn

(now Vn) from Jon

Bluals Miorof

1662, own ob-

rvor Urnbor

nd sjrnbor nd

lk rovdd

wrowr.

a rr nd unuul m of world

dnd by Klr for 1627 book of

r bl, tbule Rudolphine.


Joans ather, had studied astronomy

and globe-making with Tycho, and he

went on to run a successul map-

publishing business in Amsterdam.

Uraniborg was demolished shortlyater Tychos sudden death in 1601,

but today we can zoom in on Ven via

Google Earth and view Uraniborgs

partially restored gardens, the remains

o Stjerneborg, and even, aintly, the

remains o the lakes.

Tychos assistant, Johannes Kepler,

who would go on to attain some ame

in his own right, nished the work by

preparing a new set o star tables

based on the Hven observations.

These he published in 1627 as the

Tabulae Rudolphinae, or RudolphineTables, in honor o Rudol II o Aus-

tria, Holy Roman emperor and Tychos

royal patron at the end o his lie, and

Keplers patron as

well. The exhibit

includes a photo-

graph o a large

world map olded

inside Caltechs

copy o the Tables.

The maps unusual

projection, compris-ing one whole hemi-

sphere centered on

Europe and Arica,

fanked by two hal

hemispheres, was

Keplers own

design. It was

probably in-

tended to make

it easier or navi-

gators to plot their position by keep-

ing the most-traveled seaways o the

Known World contiguous. Keplers

line o zero longitude is centered on

Hven. Caltech is ortunate to havethis map, as it is rare: the engraver

had not nished it when the book was

published, and ater the astronomers

death three years later, it lay orgotten

until rediscovered in 1658.

Kepler also tackled the problem o

accurately measuring ones longitude,

a necessity or any maritime power

attempting to become a global pres-

ence. But although his method gave

useul results on dry land, despite his

best eorts, it proved impractical on a

tossing deck. Among those who triedto nd a better way were Giovanni

Domenico Cassini, Christiaan Huy-

gens, and Englands rst Astronomer

Royal, John Flamsteed; books and

prints refecting their work are also on

display.

Nowadays, ships, planes, and even

cars navigate with the help o

satellites, and travelers (almost)

always know exactly where they are.

Lie is saer and easierbut our

curiosity about the world around us is

as strong as ever. BE

Barbara Ellis is a writer and

researcher forOn the Map, which is

curated by Shelley Erwin, head of

Archives and Special Collections.

The majority of the books, prints, and

artifacts on display were collected

and later donated to Caltech by

Earnest C. Watson, founder of the

Watson Lecture Series and professor

of physics and dean of the faculty at

Caltech for many years. The Tabulae

Rudolphinae are from the Rocco Col-lection, purchased by trustee Harry

Bauer for Caltech in 1955.


11/48

R: Un Brnbow cnqu,

n wc nuron r lbld w df-

frnly colord fluorcn ron,

rrcr cn m ou nurl crcu

n zbrf lrv. Bcu lrv

v rlvly fw nuron nd r

rnrn, y mk for ood modl

ornm for udyn nurl nd

nc ym rul l.


WHy do We

sleep?

While we can more or less abstain

rom some basic biological urges

or ood, drink, and sexwe cant do

the same or sleep. At some point, no

matter how much espresso we drink,we just crash. And every animal thats

been studied, rom the ruit fy to the

rog, also exhibits some sort o sleep-

like behavior. (Paul Sternberg, Morgan

Proessor o Biology, was one o the

rst to show that even a millimeter-

long worm called a nematode alls

into some sort o somnolent state.)

But why do weand the rest o the

animal kingdomsleep in the rst

place?

We spend so much o our time

sleeping that it must be doing some-thing important, says David Prober,

assistant proessor o biology and

an expert on how genes and neu-

rons regulate sleep. Yes, we snooze

in order to rest and recuperate, but

what that means at the molecular,

genetic, or even cellular level remains

a mystery. Saying that we sleep be-

cause were tired is like saying we eat

because were hungry, Prober says.

That doesnt explain why its better to

eat some oods rather than others andwhat those dierent kinds o oods do

or us.

No one knows exactly why we

slumber, Prober says, but there are

our main hypotheses. The rst is

that sleeping allows the body to

repair cells damaged by metabolic

byproducts called ree radicals. The

production o these highly reactive

substances increases during the day,

when metabolism is aster. Indeed,

scientists have ound that the expres-

sion o genes involved in xing cells

gets kicked up a notch during sleep.

This hypothesis is consistent with the

act that smaller animals, which tend

to have higher metabolic rates (and

thereore produce more ree radicals),

tend to sleep more. For example,

some mice sleep or 20 hours a day,

while giraes and elephants only needtwo- to three-hour power naps.

Another idea is that sleep helps

replenish uel, which is burned while

awake. One possible uel is ATP, the

all-purpose energy-carrying molecule,

which creates an end product called

adenosine when burned. So when

ATP is low, adenosine is high, which

tells the body that its time to sleep.

While a postdoc at Harvard, Prober

helped lead some experiments in

which zebrash were given drugs that

prevented adenosine rom latchingonto receptor molecules, causing the

sh to sleep less. But when given

drugs with the opposite eect, they

slept more. He has since expanded

on these studies at Caltech.

Sleep might also be a time or your

brain to do a little housekeeping. As

you learn and absorb inormation

throughout the day, youre constantly

generating new synapses, the junc-

tions between neurons through which

brain signals travel. But your skullhas limited space, so bedtime might

be when superfuous synapses are

cleaned out.

And nally, during your daily

slumber, your brain might be replay-

ing the events o the day, reinorcing

memory and learning. Thanos Siapas,

associate proessor o computation

and neural systems, is one o several

scientists who have done experiments

that suggest this explanation or

sleep. He and his colleagues looked

at the brain activity o rats while the

rodents ran through a maze and then

again while they slept. The patterns

were similar, suggesting the rats were

reliving their day while asleep.

O course, the real reason or sleep

could be any combination o these

our ideas, Prober says. Or perhaps

only one o these hypotheses mighthave been true in the evolutionary

past, but as organisms evolved, they

developed additional uses or sleep.

Researchers in Probers lab look or

the genetic and neural systems that

aect zebrash sleeping patterns by

tweaking their genes and watching

them doze o. An overhead camera

records hundreds o tiny zebrash

larvae as they swim in an array o

shallow square dishes. A computer

automatically determines whether the

sh are awake or not based onwhether theyre moving or still, and

whether they respond to various

stimuli. Prober has identied about

500 drugs that aect their sleeping

patterns, and now his lab is searching

or the relevant genetic pathways. By

studying the sh, the researchers

hope to better understand sleep in

more complex organisms like humans.

Even i we nd only a ew new

genes, thatll really open up the eld,

he says. The uture is promising, headds, and or that, itll be well worth

staying awake. MW
http://biology.caltech.edu/Members/Sternberghttp://biology.caltech.edu/Members/Proberhttp://biology.caltech.edu/Members/Proberhttp://biology.caltech.edu/Members/Sternberg


12/48


tHe mKids are

alrigHt

Build CCAT! the decadal survey

says. Thats the U.S. National

Research Councils sixth decadal sur-

vey or astrophysics and astronomy,released in August. These surveys

predict the greatest scientic oppor-

tunities and rank proposed research

projects accordingly. The outlined

projects oer the best prospects or

making discoveriesboth anticipated

and unanticipatedor which the next

decade will be remembered. CCAT

a telescope initiated by Caltech, JPL,

and Cornell that is slated or con-

struction in the high-altitude Atacama

Desert in northern Chilewas listed

as a top priority or its part in thesearch or the rst stars, galaxies, and

black holes.

The rst two billion years o the

universe will open up in the next

decade, predicts Chuck Steidel (PhD

90), Caltechs DuBridge Proessor

o Astronomy. CCAT has a starring

role: it is the only telescope that can

survey the dustiest and most luminous

galaxies in the primordial universe.

We expect some big surprises.

Astronomers have wanted a tele-scope like CCAT since the 1980s,

when the Caltech Submillimeter Ob-

servatory (CSO) began to reveal dust

clouds packed with embryonic stars

in nearby galaxies. These clouds look

dim or black to optical telescopes, but

they blaze in the submillimeter- and

millimeter-wavelength light that the

CSO and CCAT are designed to see.

This light alls between radio waves

on the one side and near-inrared

and visible light on the other. To see

well at these wavelengthsjust out

o the reach o radio and optical

telescopescompletely new cameras

and spectrometers had to be devel-

oped.

This light may be tough to work

with, but it holds the key to under-

standing galaxy ormation. I star-

orming regions are thick with dust,primeval galaxies may also be hidden

by the dust and gas o their own

ormation. CCAT will survey huge

swaths o sky at great depths, essen-

tially looking back in time by catching

photons that have been traveling or

more than 10 billion years. Its superb

site and 25-meter dishmore than

twice as large as the CSOsare big

actors in its observing power. But the

real revolution is down in the bowels

o the telescope.

It has taken three decades odogged work, alse leads, and lucky

breaks to develop the technology

or CCATs wideband spectrometer

and its large-ormat cameras. E&S

discussed this journey o a thou-

sand steps with Jonas Zmuidzinas

(BS 81)the Kingsley Proessor o

Physics, Caltechs project scientist

or CCAT, and a leader in detector

development.

So ar, we have gotten just a

small taste o what there is to learnat submillimeter wavelengths, says

Zmuidzinas. Studying a submillimeter-

bright galaxy oten requires three

telescopes. You need a submillimeter

telescope to nd the object, a radio

telescope to pinpoint its location, and

an optical spectrometer to analyze its

chemistry and measure its redshit,

which determines its place on the

cosmic time-line.

CCAT will be able to do all o these

things. Its spectrometer, the next

generation o an instrument called

Z-Spec, will have unprecedented

bandwidth and be able to target

multiple objects simultaneously. It

will routinely nd redshits or distant,

dust-obscured galaxies rich with new

stars. Its cameras, using microwave

kinetic inductance detectors (MKIDs)

are expected to bring the state othe art rom a ew thousand pixels to

many tens o thousands o pixels and

beyond. They will capture detailed

panoramas o the submillimeter sky.

Caltech and JPL were central to

development o the new detectors.

Thats not because o one or two

peoplequite the opposite. In this

small community, ideas fy rom under-

graduates to senior researchers to

trustees to alumni (dont try to keep

track o all the characters that ollow!)

Here, a good idea can generate thenimble collaboration more typical o a

pro sports teameach player, aware

o the skills and resources o the oth-

ers, contributes what he or she can,

whether its a new method, a better

production acility, a timely inusion o

unding, or a novel design.

SiS openS the Submillimeter

Our story begins in 1979, when

Bell Labs Tom Phillipsnow AltairProessor o Physics at Caltechin-

vented the superconductor-insulator-

superconductor, or SIS mixer. The

SIS mixer was crucial to the develop-

ment o radio-style receivers or the

submillimeter band, and it is now

used in nearly all submillimeter- and

millimeter-wavelength telescopes. It

made sensitive high-resolution sub-

millimeter spectroscopy and interer-

ometry a possibility, says Zmuidzinas.

t r of colldn lx known

annn, n by (from

lf o r) ody vbl, nfrrd,

nd ubmllmr lco. CCat

wll du-roudd r-

formn ron CsO ,

bu w szr l roluon.

hubbl szr CsO
http://www.submm.org/http://www.submm.caltech.edu/http://www.submm.caltech.edu/~tgp/http://www.submm.caltech.edu/~tgp/http://www.submm.caltech.edu/http://www.submm.org/


13/48


An SIS mixer channels photons to

a tiny junction made o two layers o

superconducting metals, each just a

tenth o a micrometer thick, separated

by a smear o insulation. Excited by

the photons, electrons leap across

the insulator by quantum tunneling,

generating a measurable current with

extremely low noise. John Tucker (BS

66) developed the theory behindthese mixers, predicting that their

noise levels could be reduced to the

undamental limits set by quantum

mechanics.

Phillips, who had been a visiting as-

sociate at Caltech, joined the aculty

that year. Once installed in Caltech

telescopes, his prototype SIS receiv-

ers demonstrated antastic potential,

convincing JPL to dedicate research-

ers and lab space to the project.

The CSO also sped aheadits SIS

receivers caught their rst photonsin 1987. JPL opened its Microde-

vices Laboratory in 1988, and the

new acility turned physicists heads

nationwide.

One o those physicists was

Zmuidzinas, then a postdoc in Illinois.

He was designing ways to orce-eed

photons to an SIS junction with mini-

mal losses. He had rened a device

called a twin-slot mixer, in which two

antennas collect light and guide it into

microstrips made with superconduct-ing metals.

Zmuidzinas returned to Pasadena

in 1990. Caltech was irresistible.

The CSO had recently been com-

pleted. The Microdevices Lab had

just opened, so there was a beautiul

acility or doing this work. Today,

descendents o the twin-slot are used

in the Herschel Space Observatorys

spectrometers and in the CSOs

high-requency instruments.

SpiderwebS and Sin

A ew years later, Zmuidzinas

ocused on the problem o nding

distant submillimeter-bright galaxies,

which would require a camera with

at least a hundred detectorsone

per pixel. At the time, the workhorse

detectors were germanium bolom-

eters. Bolometers, which are used

in both cameras and spectrometers,absorb incoming photons and convert

their energy to heat, which an electri-

cal thermometer then converts to a

measurable electrical signal. But the

devices were laboriously assembled

by hand. Zmuidzinas wanted to solve

the problem by combining his twin-

slot antennas with a new bolometer

based on superconductor-insulator-

normal (SIN) junctions that had just

been invented by a UC Berkeley

student. With this approach, the en-

tire detector array could be producedby lithographyno hand-assembly

needed!

At that time, the late Andrew Lange,

then a proessor at Berkeley, and his

student Jamie Bock were developing

the spiderweb bolometer, a rened

germanium bolometer in which every-

thing could be mass-produced except

the thermometer. The web, less than

hal the diameter o a dime, was

photolithographed, gold-coated sili-

con nitride. The spiderthe thermom-eterwas hand-placed in the middle.

When the silicon backing material

was etched away, the spider and web

hung in ree space, suspended on

thin guy lines. Lange began a sab-

batical at Caltech in 1994; when he

decided to stay, Bock joined JPL as a

postdoc. JPLs Microdevices Labora-

tory was just what they needed: They

had prototyped the device at Berke-

ley, but they needed good acilities to

make a go o it, says Zmuidzinas.

Lange, Bock, and Zmuidzinas

started down both pathsspider-

webs and SINbut soon ocused on

the spiderwebs. They were more o a

known quantity, and Lange and Bock

wanted to create a working instru-

ment quickly or upcoming experi-

ments. Spiderweb bolometers made

cameras aster and more accuratethey had more detectors and needed

ewer photons to produce a measur-

able signal, and cosmic rays and the

heat and shaking o nearby equip-

ment aected them less. The 1998

BOOMERanG experiment, co-led by

Lange, used them to provide the rst

experimental evidence that the uni-

verse is fat and that the infationary

theory is correct (see An Ultrasound

Portrait o the Embryonic Universe, in

E&S2000, No. 3). Similar bolometers

are fying on the Herschel and Planckobservatories326 on Herschel and

52 on Planck. They were also used in

a 144-pixel camera installed on the

CSO in 2002.

the miSSing redShiftS

In 1998, a UK team at the James

Clerk Maxwell Telescopelocated

on the summit o Hawaiis Mauna

Kea, just a ew hundred yards rom

the CSOannounced that they hadound distant submillimeter-bright

galaxies. They had used hand-assem-

bled, thread-suspended, pre-spider-

web bolometers. It was a brute-

orce, inelegant solution, but they got

there rst, Zmuidzinas says.

The galaxies proved to be very aint

and dicult to study at other wave-

lengths. In particular, their redshits

usually measured with optical spec-

troscopyremained largely unknown.

Jon Zmudz-

n (Bs 81),

Knly prof-

or of pyc

nd Clc

rojc cn

for CCat.
http://microdevices.jpl.nasa.gov/http://microdevices.jpl.nasa.gov/http://calteches.library.caltech.edu/712/2/Ultrasound.pdfhttp://calteches.library.caltech.edu/712/2/Ultrasound.pdfhttp://calteches.library.caltech.edu/712/2/Ultrasound.pdfhttp://calteches.library.caltech.edu/712/2/Ultrasound.pdfhttp://microdevices.jpl.nasa.gov/http://microdevices.jpl.nasa.gov/


14/48


Lf: a drwb bolomr on dm.

R: tnum nrd Mcrowv Knc

inducnc Dcor, or MKiD, of y

undr dvlomn for CCat cmr. t

cv r (curd) bou cnmr

cro, or rouly z of c n

wc drwb bolomr undd,

bu MKiD 16 16 xl rry

nd of bolomr nl nor.

Zmuidzinas started to think about how

to make a submillimeter spectrometer

with enough bandwidth to measure

redshits or distant galaxies.

In an optical spectrometer, a grat-

ing diracts incoming light, bouncing

it to an array o detectors. The longer

the light ans out beore it hits the

detectors, the more the resolution

improvesbut the instrument alsogets larger. This becomes a serious

problem in the submillimeter band,

because the wavelengths are about a

thousand times longer than in the op-

tical. Hoping to shrink the instrument

back down, Zmuidzinas considered

conning the light in superconduct-

ing circuitry on a silicon waer, similar

to an ordinary printed circuit board.

This would address the problem

the metal circuitry would conne the

light vertically and also slow it down,

reducing the required path lengthsconsiderably. But experiments initi-

ated by undergraduate Chiyan Luo

(BS 00) showed that the circuitry

would lose too many photons.

Meanwhile, Jamie Bock, by then

a JPL research scientist, was also

trying to make a better submillimeter

spectrometer. He was looking into

instruments that bounced light the

old-ashioned way, with mirrors and

lenses. But they were proving to be

unmanageably large, so Zmuidzinassuggested a compromise using a

machined-metal version o the super-

conducting spectrometer.

In 2000, Bock and Zmuidzinas

joined orces to develop a new instru-

ment that would draw on each o

their approaches, and they were soon

joined by Millikan Postdoctoral Fel-

low Matt Bradord, graduate student

Bret Naylor (PhD 08), Hien Nguyen

at JPL, and collaborators at other

universities.

In Z-Spec, the resulting spectrome-

ter that was rst installed on the CSO

in 2005, eedhorns unnel light into

the 2.5-millimeter gap between two

parallel metal plates, each more than

a oot on a side. The light hits a ac-

eted, arc-shaped grating, splintering

o to be caught by 160 bolometers

variations on the spiderweb concept.Z-Specs bandwidthon par with

that o optical spectrometersis over

ten times larger than that o previous

submillimeter spectrometers. The in-

strument recently measured redshits

o several distant, dust-obscured

star-orming galaxies discovered with

Herschel.

of SQuidS and mkidS

The story doesnt end with the

smashing success o the spiderwebbolometers and Z-Spec. In act,

Lange and Bocks progress on the

bolometers had let one box un-

checked: We didnt ulll the vision

o producing large arrays o detectors

purely by lithography, Zmuidzinas

says. Its a requent quandarydo you

spend more time on a new tool that

can scale up, or do you prioritize the

ability to do interesting science right

away? The spiderwebs had mostly

solved the issue o hand-assembly,but placing the thermometers and

installing the wiring was still delicate

and labor-intensive. In the late 90s,

Zmuidzinas returned to the challenge

o making a camera with simple wiring

and thousands o mass-producible

detectors.

Kent Irwin (BS 88) had made

progress on this problem, in the

meantime, when he ound a simple,

practical way to make use o super-

conducting bolometers as a Stanord

graduate student in 1995. Called

transition edge sensors, his bolom-

eters used strips o superconducting

metal lms as thermometers. Small

temperature changes in the strips

reliably yielded measurable changes

in resistance, once Irwin drew on the

design o stereo ampliers to keep

the strips within a working tempera-ture range. Then, in 1999, in his rst

job, Irwin and collaborators (including

Erich Grossman, PhD 88) developed

readout multiplexers using supercon-

ducting quantum intererence devices

(SQUIDs) that simplied the wiring

or large bolometer arrays. Arrays o

these detectors, incorporating novel

antennas inspired by Zmuidzinass

work, are being developed at JPL

or studying the cosmic microwave

background and or sensitive spec-

troscopy rom space.It was a breakthrough, but the

SQUID multiplexers seemed com-

plicated to Zmuidzinas. The SQUID

approach works well or certain

applications, but it wouldnt scale up

to the large detector count needed

or CCATs cameras. He and JPLs

Rick LeDuc discussed the problem

at a coee shop near campus. LeDuc

wondered: Cant we use kinetic

inductance somehow?

This was a lightning bolt orZmuidzinas. Back in his oce, he

scanned the literature. Photons

absorbed by a superconductor would

produce quasiparticles. A quasipar-

ticle population boom would change

the superconductors inductance,

which would change the circuits

resonant requency. Perhaps he and

LeDuc could design a lithographed

superconducting resonator and use

its requency change as the detect-


15/48


able response. Each resonance

would be sharp, occupying a narrow

range o requencies. You could tack

resonators next to each other on one

readout wire, maybe into the thou-

sands. There was no theoretical ceil-

ing or the quality o each resonator.

reSonant interactionSZmuidzinas and LeDuc shared the

idea with Tom Tombrello, Caltechs

Kenan Proessor and then chair o

the Division o Physics, Mathematics

and Astronomy. Tombrello spoke with

then provost Steve Koonin, who con-

nected him with trustee Alex Lidow

(BS 75)who provided substantial

seed unding. Lidows git came at

a critical time or usit allowed us to

get the equipment we needed and

get set up to do this in the right way,

Zmuidzinas says. Prominent research-ers rom Caltech and JPL, as well as

other universities, signed on to the e-

ort. Koonin and Tombrello also talked

with JPLs Jakob van Zyl (PhD 86),

who helped move the project ahead.

JPLs Peter Day (PhD 93) sug-

gested making the resonators using

a structure called a coplanar wave-

guide, etched rom a superconduct-

ing metal lm deposited on a silicon

waer. In the resulting resonators, the

distance covered by the microwavesas they bounced back and orth

totaled more than a kilometer!

They were getting Qs(a qual-

ity actor related to path length) o a

million-plus, says Keith Schwab, an

applied physicist at Caltech. People

in quantum computing and applied

physics couldnt believe it. Its had

a big impact on our work. And the

technology is easy to implement.

Beyond their unanticipated ben-

ets, the new MKID circuits actually

work. The team has created a camera

with 2,304 detectorsit will be in-

stalled on the CSO in the all o 2011.

In development are new versions oMKIDs, in which the radiation is ab-

sorbed in meandering superconduct-

ing strips that also let energy slosh

back and orth between inductors and

capacitors. They will have Qs in the

tens o millions. These MKIDs rely on

superconducting titanium-nitride lms,

a choice suggested by LeDuc. They

are very simple, dropping costs and

enabling abrication o extremely large

cameras or CCAT.

The invention is also inspiring newapplications: Caltech physicist Sunil

Golwala is exploring ways to use

titanium-nitride MKIDs to detect dark

matter, Ben Mazin (PhD 04) is de-

veloping optical-wavelength versions

or astrophysics, and Zmuidzinas and

Day hope to use the material to make

a nearly ideal microwave amplier.

These ongoing eorts are supported

by the Keck Institute or Space

Studies and by the Gordon and

Betty Moore Foundation, which also

enabled earlier detector work.

As you can see, you bounce

around and it takes a while to land on

the right idea, says Zmuidzinas. Theinstruments at the heart o CCAT will

bring decades o work to ruition.

Looking back, Zmuidzinas refects,

There are always such surprising

connections. Who would have

thought that trying to look or

submillimeter galaxies would spark an

idea useul in quantum computing?

But thats how research works. There

are deep, hidden connections among

elds. We all learn rom each other.

AW

if umn y could ubmllm-

r l, ow k ovr

CCat lco would look. CCat wll

b bul o Crro Cjnnor n Cl

acm dr n lvon of

5,612 mr, on of nd

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http://www.kschwabresearch.com/http://www.astro.caltech.edu/~golwala/http://www.astro.caltech.edu/~golwala/http://www.kiss.caltech.edu/http://www.kiss.caltech.edu/http://www.moore.org/http://www.moore.org/http://www.moore.org/http://www.moore.org/http://www.kiss.caltech.edu/http://www.kiss.caltech.edu/http://www.astro.caltech.edu/~golwala/http://www.astro.caltech.edu/~golwala/http://www.kschwabresearch.com/


16/48


Left: Looking like a knight in a chain-mail hood,

Koch dons an array of electroencephalography (EEG)

electrodes for a brain-function test.

Right: Afterward, he appears to have been a ttacked

by a giant squid, thanks to the arrays suction cups.

Be Aware of Your Inner ZombieBy Andrew Portereld

Be Aware of Your Inner ZombieIn the 1968 horror classic Night of the

Living Dead, terried people trapped in a

Pennsylvania armhouse try to survive zom-

bies hungry or human fesh.

But real zombies arent like that, accord-

ing to neurobiologist Christo Koch. The

word zombie is a surprisingly technical

term, developed in detail by philosopher

David Chalmers. Zombies are exactly like

you and me except that they have no eelingor awareness, Koch saysa rather more

sympathetic view than director George

Romeros. Chalmerss 1996 book, The

Conscious Mind, proposed these zombies

as a thought experiment through which

we could explore the question o whether a

creature could exist that displayed the ull

range o human behavior but lacked con-

scious sensations. Such a zombie would get

up, get dressed, and go to work like you and

me. I you asked it over lunch what its avor-

ite band was, it might answer, Pink Floyd,

and perhaps even invite you on a date tosee a local tribute band cover Dark Side

of the Moon on Saturday. But the zombie

would not be experiencing the taste o the

sandwich it was eating, nor would it enjoy

the music as a human would. Do any natura

laws prohibit the existence o such beings?

Chalmers asked.

In act, its the unconscious, or zom-

bie, systems in our brains that help us get

through daily lie, Koch says, and they can

show us how consciousness really works.

Koch has been ascinated by the phe-nomenon o consciousness or more than

two decades, but his interest started not

with a penchant or horror cinema, but with

a toothache. I was teaching a course at

the Marine Biological Laboratory in Woods

Hole, Massachusetts. So I was lying in bed,

had this terrible toothache, Im taking aspirin

but its still persistent. He began to ask

himsel, Why should that hurt? Where does

the eeling come rom?

Koch blends techniques rom psychology,

Zombies walk among us. In act, we couldnt get along without

themoperating below the threshold o awareness, zombie

systems in our brains take care o all sorts o routine tasks

without any conscious eort on our part. Studying such un-

conscious processes is beginning to throw light on how the

conscious mind works.
http://www.klab.caltech.edu/~koch/http://www.klab.caltech.edu/~koch/


17/48


In Kochs world, the

zombies are in our

brains. In the pop-

culture world, the

zombies are out for

our brains.

biology, and neurology to attack the unda-

mental questions o consciousness: What

is it in the brain that enables us to eel?

What part o the human and animal brain is

necessary to be conscious? And how does

consciousness arise out o matter?

The debate about whether theres an

actual place or consciousness in the brain

goes back millennia. Plato and Aristotle held

that the mind was entirely divorced rom thephysical bodylike parallel Las Vegases,

what happened in the body stayed

in the body; what happened

in the mind stayed

in the mind. More

recently, the French

philosopher

Ren Descartes

argued that the

mind and the brain

could infuence each

other. He proposed that

the soul resided in thepineal glanda solitary

lump in the shape o a pine cone (but about

the size o a grain o rice) that lies almost ex-

actly in the middle o the brain, surrounded

by the matched pairs o structures that make

up the rest o the brain. This glands singular

nature and central location, he argued,

clearly marked it as something special, and

what could be more special than the physi-

cal seat o what makes us human? (Alas,

we now know that the pineal gland doesnt

do much more than help control our cycle o

waking and sleeping by secreting the hor-

mone melatonin in response to darkness.)

a Risky Business

When Koch entered the eld in 1988, the

study o consciousness was not consid-

ered serious science. A mountain climber

and trail runner, he describes himsel asa risk taker. Even without tenure, I was

adventuresome, and I was very interested in

consciousness. But talking about con-

sciousness was a sign that you were retired,

or had a Nobel Prize, or were a mystic and

slept next to crystal pyramids, he laughs. It

was like talking about sex during Victorian

timesit was just taboo. Koch paired up

with the vigorously unretired Nobel laureate

Francis Crick, the codiscoverer o the

double-helical structure o DNA, the

molecule o heredity, who had moved romprobing the workings o genes to contem-

world beyond the neurobiology community.

Today, many laboratories study con-

sciousness, and Descartess intellectual

descendants are still asking: Where in the

brain is the mind? Consider a computer,

Koch says. I you rig a thermometer to a

computer and put them both next to a heat

source, the thermometer will transmit the

ambient temperature to the computer. Once

the temperature rises above some thresholdthe computer can be set to print out a mes-

sage. It is too hot. Im in pain. But does the

computer actually experience pain? I dont

think so. At this point, its response is noth-

ing but a programmed instruction, a refex.

At a certain threshold temperature value,

some electrons fow onto a gate, a transis-

tor opens another gate, opens the register,

records the content, and prints out a state-

ment. There is no eeling involved.

Now compare that to the sensation o

someone stomping on your toe. Again, atrain o electrical impulsesthis time medi-

When Koch entered the ield in 1988, the study oconsciousness was not considered serious science.

plating the workings o the brain 15 years

earlier. The two remained close collabora-

tors until Cricks death in 2004.Francis had thought or a long time about

consciousness, and in his view it was a

scandalous state o aairs that people were

studying the brain without ever reerring to

the act that this brain produces conscious-

ness every day, day in and day out, Koch

recalls. Together, the duo published about

two dozen papers; Crick also wrote the

oreword to Kochs 2004 book, The Quest

for Consciousness, which introduced the

notion o zombie agents to the unsuspecting

ated by calcium, sodium, potassium, and

other ionsfows rom your oot to your

brain. I can say this is just biophysicssignals moving about inside the nervous

system. Theres no pain eeling anywhere.

But without any doubt youll eel this bad

thing, pain. So how is it that a physical

system like a brain can produce a subjec-

tive state, but another physical system, the

computer, doesnt? This is the heart o the

mind-body problem.

Some headway has been made since the

days o Descartes, and scientists have dis-

covered that not all o the brain is involved in

creating consciousness. The cerebellum, orexample, controls the timing o motor move-

ments, and it contains hal o the brains

neurons. I you lose your cerebellar unction

you will be unable to coordinate your muscle

movements, a condition called ataxia. You

might stagger and sway while you walk,

or instance. You wont be in a rock band,

you wont be a ballerina or a climber, but

your visual consciousness will be marginally

impacted, i at all, Koch notes.

Nudist Colony of the Dead, 1991 Pirromount Pictures.
http://www.amazon.com/gp/product/1936221047/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0974707708&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1WKZ0FE9AQK56MBMEABPhttp://www.amazon.com/gp/product/1936221047/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0974707708&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1WKZ0FE9AQK56MBMEABPhttp://www.amazon.com/gp/product/1936221047/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0974707708&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1WKZ0FE9AQK56MBMEABPhttp://www.amazon.com/gp/product/1936221047/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0974707708&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1WKZ0FE9AQK56MBMEABP


18/48


i see, TheRefoRe i am

Koch attacks the problem o conscious-

ness through the brains visual system. He

originally established his laboratorynot

coincidentally, painted in bright primary

colorsto study visual perception, trying to

understand how we ocus on one aspect o

a scene, and to gure out how this orm o

selective visual attention could be taught to

machine-vision systems. This backgroundlent itsel easily to experiments with visual

consciousness.

Kochs other longtime collaborator, Itzhak

Fried, is a proessor o neurosurgery at

UCLA who implants microelectrodes into

epilepsy patients whose seizures cannot

be controlled by nonsurgical means. Fried

uses these electrodes to nd the abnormal

brain-cell activity caused by epilepsy; the

electrodes pinpoint the lesions locations in

order to guide his scalpel. The electrodes

as many as a dozen per patient, with each

one sprouting as many as nine microwireprobes rom its tipshow up nicely in CAT

scans, which provide their tips three-

dimensional coordinates to within a ew

millimeters.

Even better, rom Kochs point o view,

each microwire is sensitive enough to pick

up the musings o a single neuron. As luck

would have it, some o the deep-brain cen-

ters involved in recognizing and remember-

ing people are in brain areas that are most

oten aected by epilepsy, such as the

hippocampus. Thus Frieds electrodes giveKoch a window intoor, more accurately,

a water glass pressed up against the wall

othose regions o the brain.

The electrodes remain in the patients

heads or up to two weeks. Thats a long

time to spend hanging around in a hospi-

tal, so the simple video games that Koch

and his colleagues have designed or their

experiments oer a welcome distraction.

As the patients stare at the computer

screens, the researchers use the electrodes

to look or neural correlates o conscious-

ness, or NCCs, which Koch and Crick had

dened in a 2003 paper called A Frame-

work or Consciousness. The paper pro-

posed that visual NCCs are small coalitions

o nerve cells that collect inormation rom

the back o the cerebral cortex, where the

preliminary processing o visual inormation

is perormed, and establish sets o two-way

communication links with other parts o thecerebral cortex at the ront o the brain.

The receiving regions include the medial

temporal lobe, where Koch, his grad student

Gabriel Kreiman (MS, PhD 02), and Fried

had already ound neurons that only red

when a person was consciously perceiv-

ing an image. That discovery had been

made by tting Frieds patients with special

LCD glasses that were, in eect, separate

TV screens or each eye. A picture would

appear on one screen and remain there so

that the test subjects could clearly see it.

Then a second, dierent picture would bemomentarily fashed into the other eyea

technique known as fash suppression,

because the new picture in the second

eye would suppress the perception o the

old image in the rst eye. In other words,

the resh image wiped the older one rom

consciousness, even though both were still

there to be seen. The neurons ring rates

refected this. Kreiman noticed that, in most

cases, each neuron being recorded would

respond to only one specic image, say a

picture o a smiling girl. When the imagewas fash-suppressed, however, the neuron

became ar less active, even though its

preerred picture was still displayed. Those

neurons, thereore, ollowed whatever was

in the patients conscious perception. They

red when the patient saw the image, and

they didnt re when the patient didnt.

Wherever the brains representations o

the suppressed imagesvisible, but not

consciously seenmight reside, they had to

be somewhere else.

seeing JennifeR anisTon

That some neurons red only in response

to specic pictures was no big surprise

ater all, pattern recognition is one o the

things our brains do best. But in 2005,

postdoc Rodrigo Quian Quiroga; grad

student Leila Reddy (PhD 05); Kreiman, by

then at MIT; Koch; and Fried announced the

discovery o individual neurons in the medial

temporal lobes that recognized specicpeople. It didnt matter whether the picture

presented was ull-ace or in prole, or even

a line drawing or a caricature; the neuron

knew who it was looking at.

The rst neuron we ound behaving this

way was a Bill Clinton neuron back in 2002,

Koch recalls. Then, there was a second

neuron that responded to three dierent

cartoon images o characters rom The

Simpsons, and a third selective neuron to

basketball superstar Michael Jordan. When

we rst submitted the paper to Nature, the

reerees didnt believe this unheard-o

Left: The regions mentioned in this article lie deep

within your brain. (The brains outer surface is out-

lined in orange.) Visual processing begins in area V1

also known as the primary visual cortex. V2 through

V5 do additional analysis before sending the informa

tion on to the medial temporal lobe, the hippocampu

and other areas where consciousness may lurk. V1

through V5 are on the inner, facing surfaces of the ce

rebral hemispheres; the hippocampus, the cerebellum

and the pineal gland straddle the brains midline.

Far left: A horizontal slice through the temporal lobes

V3AV3V1/V2V4 (color)Cerebellum

Face and objectrecognition areas

V5 (motion)

Front

Temporal lobe

Hippocampus

Pineal gland

Medial temporal lobe
http://www.nature.com/neuro/journal/v6/n2/abs/nn0203-119.htmlhttp://www.nature.com/neuro/journal/v6/n2/abs/nn0203-119.htmlhttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.nature.com/nature/journal/v435/n7045/abs/nature03687.htmlhttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.pnas.org/content/99/12/8378.abstracthttp://www.nature.com/neuro/journal/v6/n2/abs/nn0203-119.htmlhttp://www.nature.com/neuro/journal/v6/n2/abs/nn0203-119.html


19/48


Your brain wires up groups of cells that respond to things weconstantly encounter. I had no idea who Jennifer Anistonwas before we did these experiments, but presumably I nowhave a set of neurons that respond to Jennifer Aniston,Koch chuckles.

degree o selectivity, since we only had

three such neurons. Three neurons dont

make a discovery. So we went back and

characterized many more o these remark-

able cells51 in that 2005 Nature paper,

and more since then.

Grad student Stephen Waydo (PhD 08),

on loan rom control and dynamical systems

proessor Richard Murray (BS 85), and

Koch pieced together an explanation or theprocess behind such extreme selectivity.

Although the world around us presents an

innite variety o stimuli, Waydo and Koch

assumed that most o the patterns that

come to us through our senses are due to

a small number o causes. For instance,

when Im at home, most o the visual activity

in my brain at any given moment is caused

by me seeing my amily and the urniture in

the rooms around me, all o which are very

amiliar to me, Koch says. Working rom this

premise, Waydo devised a set o machine-

learning rules that would enable a com-puter to identiy such commonly occurring

patternsdiscovering or itsel the Platonic

orm, i you will, o Kochs soaand then

represent each one as a specic pattern o

outputs rom a collection o neurons.

Similarly, says Koch, Your brain wires up

groups o cells, what we call concept cells,

that re specically in response to things we

constantly encounter. To illustrate this, he

brings up on his computer a session with

one o Frieds patients. An image o Marilyn

Monroe appears on the screen: a rapid-

re trrrppp, trrrppp, trrrppp pours rom the

speakers. Then, actor Josh Brolin; nothing.

I had no idea who Jennier Aniston

was beore we did these experiments, but

presumably I now have a set o neurons that

respond to Jennier Aniston, Koch chuck-

les. Its an ecient way o dealing with the

world. It allows inants to learn early thelessons that stay with us: rst you learn to

recognize your parents and your siblings in

this abstract and invariant matter, and your

dog, and all the other important people, ani-

mals, and things that your brain constantly

encounters. Then when you get older, its

on to mastering more abstract things, like

Marcel Proust or e = mc2.

Concept cells respond to sensory stimuli

o all kindsin Anistons case, or example,

not just seeing her, but hearing the sound

o her voice or even reading her name; this

set o neurons will activate when exposed toany aspect o the Zen o Jen.

There are two schools o thought about

how concept cells work. The distributed-

population hypothesis invokes a large

number o neurons, each contributing a little

bit to encoding the percept. The power o

this approach lies in the great number o

distinct objects that can be encoded, and

in the robustness o their representation

lose any one neuron, and the percept hardly

changes. The sparse-coding hypothesis, on

the other hand, proposes that a small net-

work o neurons is entirely responsible or

the encoding. The ultimate sparse network

would be one consisting o a single cell;

this reduction to the extreme is known in the

trade as the grandmother cell hypothesis,

because it implies that somewhere in your

brain there lives a cell whose sole duty is to

recognize your grandmother.At rst blush, the existence o Jennier

Aniston neurons would seem to support

the grandmother-cell hypothesis, but there

is something to both sides, says Koch.

In 2008, Quian Quiroga, Kreiman, Koch,

and Fried ound that yet another o Frieds

patients had a neuron in the hippocampus

(an interior region o the medial temporal

lobe) that responded not only to Aniston but

to her Friends costar Lisa Kudrow. Since

the two actresses have only one degree o

separation on the small screen, it seems

reasonable that their NCCs might share aew cells as well. (Another cell in the para-

hippocampal cortex o a dierent patient

red in response to both the Eiel Tower

and the Leaning Tower o Pisa but not to

other landmarks, displaying a similar power

o generalization.) So it appears that the

networks are indeed sparse, but maybe not

thatsparsethey contain enough members

to be both very selective and very abstract

at the same time.

A couple of famous people who might be in your head.

The first concept cell that Kochs team discovered fired in response to pictures of President Clinton.

If youve watched more than a few episodes of Friends, youve probably got a set of neurons that respond to

actress Jennifer Aniston.

Once a network of concept cells has been wired up, it will be activated whenever it recognizes the object of its

obsession. It doesnt matter whether the image it sees is a grainy black-and-white photo or even a scrawled

cariacture; nor does it matter if the subject is seen in a full-face view, in profile, or even partly obscured.

In fact, the stimulus doesnt even have to be visual. Concept cells will react to sounds, smells, and even the

written wordany sensory stimulus that we associate with that person.
http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(08)00023-5


20/48


living The ZomBie life

So what do zombies have to do with

any o this? More than wed like to admit,

apparently. In his upcoming book, Con-

sciousnessConfessions of a Romantic

Reductionist, Koch recalls a trail-running

session in which he encountered a rattle-

snake. Something made me look down. My

right leg instantly lengthened its stride, or

my brain had detected a rattlesnake sunningitsel on the stony path where I was about to

put my oot, he writes. Beore I had seen

the reptile or experienced any ear . . . I had

already acted to avoid stepping on it. Had

he been orced to think about consciously

adjusting his stride, it would have been too

late.

This unconscious, automatic response

was choreographed by one o our zombie

systems. While its well known that the ner-

vous system controls many body unctions

without conscious eortthings such as

heartbeat, breathing, and digestionKochestimates that about 90 percent o our ac-

tivities are the work o unconscious zombies.

The central insight o Sigmund Freud is

that youre not conscious o most o the stu

in your brain. For example, we spend much

o the day typing. Now, i I ask someone,

What nger do you type the letter fwith?

most people wont know. They have to pan-

tomime the movement to realize that its the

let index nger. But i you dont consciously

think about it, your ngers will do the typing

by themselves. Even activities as seem-

ingly varied and unstructured as Kochs

mountain-climbing adventures call on these

zombie systems most o the time. Nearly all

o his risky moves up the side o a cli are

so ingrained that he doesnt give them a

thought.

So why isnt all o lie like that? he asks.

Why not have a completely zombie exis-

tence? Because lie throws us curve balls,

thats why. The world is so complex; you

have to do things that are nonroutine. Letssay there was an earthquake right now. You

would look rst at the glass window, which

could shatter and seriously injure you, and

then you would look around or a sae way

to get outside. Reacting to an earthquake

isnt something youve trained or hundreds

o times. But or repetitive behaviors, even

very elaborate ones, its a convenient way or

our brain to handle the situation with minimal

eort.

Paying aTTenTion

But even with an army o zombies at our

command, we suer rom inormation over-

load, says Koch. We have to concentrate

on the essentials; otherwise we wouldnt get

anything done. Attention is the brains way

o maintaining ocus. But attention is not

the same as awareness or consciousness,

he adds. While consciousness involves the

general awareness o the world around us,

or what we think is the world around us, at-

tention is a spotlight. Attention takes hold o

one aspect o our environment, whether its

scanning your DVD collection or the sev-

enth season o Friends or listening to one

person in a crowded room. Its a mechanism

or selecting or urther processing a ew

rivulets o inormation out o the food that

inundates our senses, providing the brain

a way to organize multiple inputs and make

sense o the world.

Scientists have long assumed that atten-

tion and consciousness are the same, or at

the very least heavily intertwined. This pastMay, biology postdoc Jeroen van Boxtel,

psychology and neuroscience postdoc

Naotsugu Tsuchiya, and Koch demonstrated

that this assumption is wrong. In these

experiments, members o the campus com-

munity were asked to xate their eyes, with-

out any movement, on a dot in the center

o a computer screen. Then, o to one side

o one eyes eld o view, a Gabor patcha

computer-generated blur resembling a smal

smudgewould appear or our seconds

and then vanish, leaving an aterimage in

the eye that had seen it. (Aterimages arethe oldest tools o visual psychologists, as

they are easy to induce and manipulate in

reproducible ways.) The volunteers pressed

a button when the aterimage disappeared.

At the same time, the participants were

asked to count the number o times a

specic symbol appeared among a series o

symbols that rapidly fashed, one by one, at

the center o their gaze. In some o the runs,

the correct symbols were made deliberately

hard to spota demanding task requiring

ull attention. In other runs, the task waseasier, mean

Caltech_Fall2010

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