“Most people say that it is the intellect which makesa great scientist. They are wrong: it is character.”

Albert Einstein02 KNOWLEDGEPEDIA

HERE’S OUR GUIDE FOR EARTHLINGS

Source: New York Times News Service

HEY FOLKS! I’M . TODAY WE’LL KNOWWHAT HAPPENS IFYOU FALL INTO ABLACK HOLE AND

MORE...

Welcome, earthlings, to the place ofno return: a region in space wherethe gravitational pull is so strong,not even light can escape it. This is

a black hole. It’s OK to feel lost here. Even AlbertEinstein, whose theory of general relativity made itpossible to conceive of such a place, thought theconcept was too bizarre to exist. But Einstein waswrong, and so, here you are. But fear not, dearearthlings, your brain has taken millions of years toget here, and it’s ready for this gaze into thedarkness. So let’s get started...

It swallows up everything too close, tooslow or too small to fight its gravitationalforce. With every planet, gas, star or bit of

mass consumed, the black hole grows. Theedge of a black hole, its event horizon, is thepoint of no return. Here, light is drawn in to ablack hole, never to escape. And nothing isfaster than light.

A BLACK HOLE IS A HUNGRY BEAST

Will gravity rip you apart and crush you intothe black hole’s core? Or will a firewall ofenergy sizzle you into oblivion? Could

some essence of you ever emerge from a black hole?The question of how you would die inside a black holeis one of the biggest debates in physics. Called thefirewall paradox, it was posited in March 2012 by agroup of theorists including Donald Marolf, AhmedAlmheiri, James Sully and Joseph Polchinski. Based onthe mathematics in Einstein’s general theory of relativ-

ity of 1915, you would fall through the event horizonunscathed, then the force of gravity would pull you intoa noodle and ultimately cram you into singularity, theblack hole’s infinitely dense core. But Polchinski andhis team pitted Einstein against the quantum theory,which posited that an event horizon is a blazing fire-wall of energy that would torch your body tosmithereens. However, the presence of a firewall wouldviolate the principles of relativity, which decreed theexistence of black holes. And so physics is stuck.

IF YOU FELL INTO A BLACK HOLE, IT’S NOT CLEAR HOW YOU WOULD DIE

Either someoneis wrong, or wehave to admit

that earthlings are stillnot equipped to under-stand the universe. Thefirewall paradox callsinto question the mostdefinitive theories ofscience. The insight andwisdom of Einstein,Polchinski or StephenHawking notwithstanding, everything we know about theuniverse could change if we could know for certain whathappens to information inside a black hole.

HOW THE UNIVERSE WORKSDEPENDS ON BLACK HOLES

☛ The Milky Way galaxy alone is thought toharbour some 100 million stellar-mass blackholes, plus the supermassive Sagittarius A atits heart. With 100 billion galaxies out there,each with 100 million stellar-mass blackholes and a core supermassive monster (notto mention other types being discovered),it's like trying to count grains of sand.

☛ How dense can a black hole get? Imaginewhat kind of density you will get if you tryto squeeze in the entire mass of Earth in asmall (we mean miniscule) sphere with aDIAMETER of 9 millimetres! That’s the typeof density we are talking about.

☛ Cygnus X-1 was the first black hole discoveredin the 1960s, and it’s 10 times more massivethan the Sun.

☛ The closest black hole, V4647 Sagitarii,was thought to be 1,600 light years away.But scientists now believe that this blackhole is about 20,000 light years away.

A GIANT MAGNET IN EUROPEWILL NOT DESTROY THE PLANET

Before the European Organisation for NuclearResearch fired up the Large Hadron Collider in2008, critics worried that smashing together

protons in a 17-mile ring underground would create ablack hole that would swallow Earth. Scientists, howev-er, had smaller ones in mind. In theory, the search forthe smallest particles in the universe might kick up miniblack holes in the collider’s underground tubes, enablingresearchers to observe general relativity and quantummechanics in action, and perhaps open the door to solv-ing the firewall paradox. But, it won’t cause an apoc-alypse. Still, in June 2008, a safety review pro-claimed the Large Hadron Collider safe.Experiments commenced, the Higgs boson wasfound and Earth survived after all.

Quantum effects suggest that, asHawking radiation leaks into the uni-verse, a black hole will dissipate,

eventually. It will take many times the age ofthe universe for a black hole to fully disappear.Like Einstein, Hawking at first did not believehis own theory. But the numbers were right.Physicists now view his result as the backbonefor whatever future theory will bring togethergravity and quantum theory.

A BLACK HOLE IS NOT FOREVER

A lthough no black hole is close enough to Earth to pull the planet to itsdoom, there are so many black holes in the universe that counting them isimpossible. Nearly every galaxy — our own Milky Way, as well as the 100

billion or so other galaxies visible from Earth — shows signs of a supermassive blackhole in its centre. Moreover the bigger a galaxy, the more massive its central blackhole. Nobody knows why. Of the billions of stars in the Milky Way, about one in every1,000 new stars is massive enough to become a black hole. Our sun is not. But a star25 times heavier is. Stellar-mass black holes result from the death of these stars,and can exist anywhere in the galaxy.

ASTRONOMERS HAVE EVIDENCE FOR BLACK HOLESIN NEARLY EVERY GALAXY IN THE UNIVERSE

On July 2, 1967, a network of satellites recordedan explosion of gamma rays coming from outerspace. In retrospect, it was one of the first indi-

cations that black holes are real. Today, scientists believethat a gamma ray burst is the final breath of a dying starand the birth of a stellar-mass black hole. The dramatictransformation starts when a massive star runs out of fuel.As the star begins to collapse, it explodes. The star’s outerlayers spew out into space, but the inside implodes,becoming denser and denser, until there is too much mat-

ter in too little space. The core succumbs to its owngravitational pull and collapses into itself, inextreme cases forming a black hole. Theoretically,if you shrank any mass down into a certain amountof space, it could become a black hole.

BLACK HOLES ARE STELLARTOMBSTONES

O n March 28, 2011, astronomers detected a longgamma ray burst coming from the centre of agalaxy 4 billion light years away. This was the

first time humans observed what might have been a dor-mant black hole eating a star. No matter what a black holeeats — a star, a donkey, an iPhone — it’s all the same tothe black hole. “A black hole has no hair,” the physicistJohn Archibald Wheeler once said, meaning that a blackhole remembers only the mass, spin and charge of its din-ner. The more a black hole eats, the more it grows. In 2011,scientists discovered one of the biggest black holes ever,more than 300 million light years away. It weighs enoughto have gobbled up 21 billion suns. Scientists want to knowif the biggest black holes are the result of two holesmerging or one hole eating a lot. But scientists don’t knowhow they grew so large.

BLACK HOLE CAN GOBBLE UP 21BILLION SUNS

TO FIND THE DARKNESS, FOLLOW THE LIGHT

L ight can’t escape a black hole, so seeingwhat’s inside one is impossible. Getting apicture of a black hole’s edge is difficult,

and getting a clear picture is something elseentirely. And until now, it has never been done.So far, scientists have detected black holes onlyindirectly, by their signatures, such as a gamma

ray burst, supernova or,perhaps, an object on thebrink of a black hole’sevent horizon. Typically, iftremendous energy isemanating from a massivecore at the centre of agalaxy, the core is proba-bly a black hole. The EventHorizon Telescope, theone that SheperdDoeleman and his col-leagues used to photo-graph the black hole in thegalaxy M87, required more

than 100 scientists on four continents and a veryimportant crystal used to calibrate atomic clocks.In April 2017, scientists put out eight telescopesatop mountains on four continents, synchronisedthem, pointed them at the sky and waited. And sothey brought Einstein’s monster, the black hole,into view for the first time.