They are the most powerful objects in the universe. Nothing, not even light, can escape the gravitational pull of a black hole. Astronomers now believe there are billions of them out in the cosmos, swallowing up planets, even entire stars in violent feeding frenzies. New theoretical research into the twisted reality of black holes suggests that three-dimensional space could be an illusion. That reality actually takes place on a two-dimensional hologram at the edge of the universe.
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LearningTranscript
00:01There are monsters out in the cosmos that can swallow entire stars.
00:08That can destroy space itself.
00:12Black holes.
00:14For decades they remained completely hidden.
00:17But now, scientists are entering into their uncharted territory.
00:22They've discovered that black holes don't just rule the realm of stars and galaxies.
00:27They impact all of us here on Earth.
00:31Because black holes just might be the key to understanding the true nature of reality.
00:45Space.
00:47Time.
00:48Life itself.
00:52The secrets of the cosmos lie through the wormhole.
00:57Take planet Earth and squeeze it down to the size of a marble.
01:13You'll create an object so dense that not even light traveling at 186,000 miles per second can escape its extraordinary gravitational core.
01:23Its name?
01:26A black hole.
01:28Astrophysicists think that black holes might form when giant stars run out of fuel and collapse under their own weight.
01:36We're not really sure.
01:39Why?
01:40Because black holes are places where the accepted laws of physics break down.
01:47A few bold thinkers are now making giant strides towards understanding what goes on inside black holes.
01:55And the new laws of physics that emerge have an astonishing implication.
02:00You, me, and the world we live in may be nothing more than an illusion.
02:08In my hometown in Mississippi there was a well.
02:20It fascinated me to gaze into its murky depths to try and see what lay at the bottom.
02:25I would sit there, throwing pebbles into it, trying desperately to hear a faint splash of water.
02:32But all I got was silence.
02:38One day, I took a dime stored toy soldier, made a parachute for it out of an old handkerchief, and watched it float down.
02:46I wondered what would happen to him when he hit the bottom, or if he would just keep on falling forever into that impenetrable blackness.
03:00Today, theoretical physicists are drawn to black holes like I was to that old well, trying to understand how they really work, and what they can tell us about the universe.
03:17It's one of those things that sounds like science fiction, only it's better because, you know, it's real.
03:21A black hole is the window into a world that we don't have the concepts, we don't even have the mental architecture yet to be able to envision properly.
03:32You are in this strange world of strong gravity, where there are no straight lines anymore.
03:39You can't even see it. That is disturbing and exciting at the same time.
03:45The notion of a black hole is a natural extension of the laws of gravity.
03:49The closer you are to a massive object, the more the pull of its gravity slows down anything trying to escape from it.
03:57The surface of the Earth is 4000 miles away from its center, so the force of gravity up here is not very strong.
04:05Even a kid can resist it, for a second or two.
04:09But if you could squeeze the Earth down so that all of its mass is really close to the center, the force of gravity would grow incredibly strong.
04:17Nothing could move fast enough to leave its surface. Not just a jumping boy. Even the beams of light speeding out from his shoes would be trapped.
04:26So if you are trying to imagine creating something so dense that not even light can escape, you are trying to get a system so compact that the speed that it takes to escape from that object is greater than the speed of light.
04:39Now the speed of light is 186,000 miles per second. So that is going really fast. Gravity is quite weak. I think it is surprising. The whole Earth is pulling on a rocket ship and all it has to do is go 7 miles per second to escape from the Earth.
04:52And to get all the way to a black hole, you would have to crunch down the entire sun to be less than a few kilometers across. Now it would take something traveling greater than the speed of light to escape so nothing can escape and the whole object goes dark.
05:08Christian Ott, an astrophysicist at the California Institute of Technology, has been trying to understand how such strange entities as black holes might really form in the cosmos.
05:23He studies what goes on when giant stars run out of fuel and start to shrink.
05:31A process comparable to the collapse of an exhausted marathon runner.
05:44So in some sense, you prepare a star at the prime of its life for the runner who is just starting out, still real fresh, consuming oxygen aerobically.
05:53And it's the same with stars. They burn hydrogen into helium slowly and they're getting a lot of energy out of every single hydrogen nucleus they burn.
06:06After they're done fusing hydrogen into helium, they go on to more and more heavy elements and that fuel goes fast and fast.
06:14So at the end, they end up with iron and that's when their fuel is over, the fuel is out.
06:21And it's basically like a marathon runner hitting a wall in a marathon.
06:25But unlike a runner who can restore his energy with food and drink, a dying star has no way to come back from the brink.
06:32There's no more heat generation, no more energy generation happening at its core.
06:40So gravity keeps on pulling in and since there's nothing producing pressure to sustain it, it will just collapse.
06:46You get a shock wave and the shock wave moves out and it actually blows up the entire star and that's the phenomenon we call supernova.
06:52The death throes of giant stars are the most dramatic events astronomers have ever witnessed.
07:02Chinese stargazers saw one explode in 1054.
07:06It was so bright they could even watch it by day.
07:10Another two blew up around 400 years ago.
07:12These colossal explosions leave debris fills of gas and dust hundreds of light years across, still visible and still expanding today.
07:25But what interests black hole researchers is not the explosion, it's what happens at the very center of the dying star.
07:33Modern astronomers have never witnessed a star in our own galaxy explode.
07:38But theoretical physics predicts that if a star is large enough, its collapsing core should shrink down to form a black hole.
07:51So imagine the balloon is a star and the star stays alive by burning thermonuclear fuel and as it does so you get heavier elements like the sponge and all that energy released like the energy released in a bomb.
08:03So as a star runs out of fuel it begins to cool and as it cools it's no longer supported by all that pressure and so it starts to collapse under its own weight and it will continue to collapse until it gets so small that now you're running up against the pressure of crushing the matter together.
08:20And at this stage it's a little bigger than the size of the earth and it's supported by pushing all of the electrons and the atoms closer and closer together.
08:27Now if it's more massive than a couple of times the mass of the sun it will start to collapse even further and there is no form of pressure that can resist this collapse and it will continue to collapse down until it forms a black hole.
08:40But do such strange crushed corpses of stars really exist out in the cosmos?
08:51Could they be lurking at the center of some of those clouds of gas and dust thrown off in a supernova?
08:57Christian Ott and his theoretical astrophysicist group at Caltech are trying to discover whether exploding stars really do form black holes.
09:10Christian Ott and his theoretical astrophysicist group at Caltech are trying to discover whether exploding stars really do form black holes.
09:11Well I'm just generally, you know, I'm really excited about stars that blow up actually.
09:15First of all to get a black hole you need low specific angle momentum.
09:18To have a critically spinning black hole you need a lot of angle momentum.
09:22There are two ways to find out whether black holes really form when stars blow up.
09:28One is to wait for a supernova to go off in our galaxy and use every tool of modern astronomy to pick it apart.
09:36A galactic supernova would provide us so much information we wouldn't sleep for weeks.
09:41But unfortunately it happens only maybe once or twice per century.
09:47So Christian and his team are trying a different approach.
09:50Blowing up stars inside powerful supercomputers.
09:54This is no easy task.
09:56In fact, no one has pulled it off.
09:58But Christian is on his way to being the first.
10:02So simulating supernovae stellar collapse and black hole formation is so hard because it brings together a lot of physics.
10:09It's general relativity for gravity.
10:11It's fluid dynamics for the gas that collapses.
10:14It's particle physics doing these simulations like trying to do a really good weather forecast.
10:21So far Christian has failed to make a virtual star explode in a way that looks like a real supernova.
10:27But after years of refining the physics and the math, he now thinks he may be the first to fully understand how a black hole is born.
10:41What's surprising is that the most promising simulations don't actually explode.
10:56They simply collapse.
10:58It's not a bang, but a whimper.
11:01Its name, not supernova, but unnova.
11:06It's basically just everything eventually sinks into a black hole and the star slowly but surely just disappears.
11:13It could be true that most stars or a large fraction of stars just disappear.
11:18We, you know, don't have any data on that.
11:20We have never seen an unnova.
11:22If Christian is right and black holes form silently, then these cosmic cannibals could be hidden in plain sight all around us.
11:33And we might never know it.
11:36Finding black holes is terribly, terribly difficult.
11:39Even if it wasn't black and would be radiating energy, it would still be only, let's say, 20 miles across.
11:47And even, you know, at 10 light years away, it would be impossible to find even with the best telescopes we have.
11:54But if black holes were almost completely elusive, no one told this man.
11:59He spent the past 30 years hunting one, a giant one, right at the heart of our own Milky Way galaxy.
12:07And his discovery will overturn all our ideas about how the universe really works.
12:23In 1931, a Bell Telephone researcher, Carl Jansky, was testing a new system for sending radio messages across the Atlantic to Europe.
12:33He was plagued by background noise.
12:38After two years of careful work, Jansky stripped out most of the interference.
12:43But one strange signal never went away.
12:48It was loudest whenever his antenna was pointed at the constellation Sagittarius, at the very heart of the Milky Way.
12:56It was a signal unlike anything a star would make.
13:03Astronomers began to wonder whether it might come from an object theorists had predicted, but never detected.
13:10A black hole.
13:13But there was no way to find out.
13:17The center of our galaxy is hidden from view by a thick veil of dust.
13:23Then, 25 years ago, a German astronomer, Reinhard Genzel, found a way to see through the fog.
13:31The problem is, we are sitting in the Milky Way, and the galactic center is sort of just along the way through the entire plane of this big spiral galaxy we are sitting in.
13:41And there's all this gunk, this dust and this gas between us and the galactic centers.
13:46You can't see it in the visible.
13:47But at longer wavelengths, this dust is not as efficient.
13:50Infrared light with its longer wavelength is perfect for penetrating the veil.
13:57But it's terrible at getting through the water vapor in Earth's atmosphere.
14:02So Reinhard Genzel headed for the highest, driest place on Earth, the Atacama Desert of Chile.
14:09Beginning in 1992, he and his team at the Max Planck Institute began what would become an enduring campaign
14:16to find out exactly what was causing the strange noise at the center of the Milky Way.
14:22In fact, we found in the center of the Milky Way a very dense collection of stars.
14:27That's the very center of the Milky Way around which, you know, everything turns.
14:31And then came the first suspicions, maybe, maybe there's something there.
14:36Reinhard had a hunch that a black hole could be acting as a colossal center of gravity, causing dozens of stars to whirl around it.
14:45So he settled in for the long haul.
14:47Each year, he took another set of pictures, plotting the movement of that cluster of stars at our galaxy's heart.
14:54He gathered a large team to help him handle the immense amounts of data,
14:59and used a new technique called adaptive optics to make the images of these distant stars sharper.
15:07So if you look at what the galactic center would look like in a normal telescope, let's say,
15:12you would get images which look like that.
15:15The effect of these adaptive optics you can see on the right-hand side,
15:18it's just amazing how beautiful that image gets.
15:21It's really the same scenery.
15:22You can recognize those two stars here on the left-hand side in the blurred image.
15:27They are these two stars on the right-hand side.
15:30As the years went by, a striking pattern emerged.
15:34Stars were moving, moving really fast.
15:38This was something that no astronomer had ever seen before.
15:41A dozen, then 20, then 30 stars, all swirling at breakneck speed around a central object that was completely dark and tremendously dense.
15:52Could this be the first proof that black holes existed?
15:55And if so, was there really one here, right in the center of our own galaxy?
16:05What do you do in order to see something or prove that it exists on something which you can't really see, right?
16:11And the black hole, you would think, is something, well, by definition, light can't escape from.
16:16But you have gravity.
16:18Think of the solar system, okay?
16:20You have the Sun in the center, and then you have the planets.
16:23The outer planets move very slowly around the Sun.
16:27And the closer you come to the Sun, the faster the planets go.
16:30So suppose in your mind you switch off the Sun, you would have to conclude that there is a central object
16:35with one solar mass around which the planets orbit.
16:38See, that's what we're doing.
16:41So these are the stars of the show.
16:43Here at the very center here is the radio source, which we suspect is the location of the black hole.
16:49This is our best star which we have followed for 15 years to trace a full orbit.
16:57This star, known only by the name S2, was moving at a phenomenal rate.
17:03At its closest approach to the dark central object, Reinhardt and his team clocked it moving at 11 million miles per hour.
17:11What we learned from this is that indeed there is only one central mass, right there at the position of the radio source,
17:18and that has 4 million solar masses.
17:21There cannot really be any believable configuration which we know of other than a black hole.
17:27Reinhardt Genzel had made the first definitive discovery of a black hole.
17:37But more than that, his team had found an object that must have swallowed millions of stars over its lifetime.
17:44Astronomers call it a supermassive black hole.
17:49But despite the enormity of this discovery, it would be just the first of many increasingly bizarre and disturbing findings.
17:58The next was to figure out what goes on inside a black hole.
18:03What happens to stars, planets, even people, if they get too close to this cosmic sinkhole?
18:10No telescope can ever see inside black holes.
18:14To understand how they twist reality, we have to stop looking and learn how to listen.
18:21Lurking at the center of our galaxy is an object that's completely invisible, but weighs as much as 4 million stars.
18:36Astronomers now believe almost every galaxy has a supermassive black hole at its core.
18:43So, what are they?
18:46Science fiction sees black holes as cosmic time machines or portals to a parallel universe.
18:53But real scientists are finding that truth is stranger than sci-fi.
18:59You're about to enter a world where the very big and the very small are indistinguishable.
19:06Where reality and illusion are one and the same.
19:12Astronomer Julie Comerford has been studying the centers of dozens of distant galaxies.
19:18Trying to find signs of black holes.
19:21Hoping to learn more about these mind-bending objects.
19:25It turns out that in all or nearly all galaxies, wherever we look, they have a central supermassive black hole at their heart.
19:32Supermassive ones are the ones that have masses of anywhere from a million to a billion times the mass of the sun.
19:37You can see a supermassive black hole when gas is falling onto it.
19:41And sort of right before the gas falls into it, it gets heated up and emits a lot of energy and can appear really bright.
19:47But when Julie investigates the glowing gas surrounding these giant black holes, she finds something totally unexpected.
19:56There's a cosmic dance going on, on a scale that's almost unimaginable.
20:06You saw two peaks in the light instead of just one.
20:09You'd expect one from one black hole that's just sitting at rest in its galaxy.
20:13But we saw two peaks with different velocities and that immediately hit us as this has got to be something interesting.
20:19Julie began thinking about what would happen when two galaxies collide.
20:24And if both had black holes at their centers, what would happen to those massive objects?
20:31So when two galaxies collide, the black holes at their center, instead of crashing in head-on, they begin this swirl or dance.
20:38And the way that we can detect these vaulting black holes is by looking at the light that's emitted from them.
20:44So for the black hole that's moving towards us, we detect light that is at smaller wavelengths scrunched up together, so we see bluer light.
20:52And for the black hole that's moving away from us, we see stretched out, longer wavelength light that appears redder.
20:59So it's this redder and bluer light that is a telltale signature of a black hole waltz.
21:03Every time we see it, we high-five in the observation room, and we just can't get over it.
21:09As Julie scans the universe, she finds the same remarkable dance happening time and time again.
21:16In galaxy after galaxy, black holes are paired up and dancing the cosmic night away.
21:23So we identified 90 galaxies from when the universe was half its present age.
21:27And we found that fully 32 of them, or about a third, had black holes that exhibited this blue and red signature.
21:34So that was really surprising that such a high fraction of the black holes were not stationary at the center of the galaxy at all,
21:40that they were undergoing this waltz with another black hole.
21:44Scientists like Jana Levin believe the discovery of waltzing black holes opens up a whole new way to learn what's inside them.
21:54Because their dance might not only be visible, it could also be audible.
22:01The scientific visionary Albert Einstein saw space and time as a flexible material that could be distorted by gravity.
22:10A black hole is merely a very deep well in this material.
22:14When two black holes come close to one another, these two orbiting wells stir up spacetime and send out ripples that can travel clear across the universe.
22:26And these waves will move out through the universe traveling at the speed of light.
22:30So we can hope to not see black holes with light, but maybe in some sense hear them if we can pick up the wobbling of the fabric of spacetime itself.
22:41For the past several years, Jana and her colleagues have been trying to predict the sounds black holes make as they spin around one another.
22:50Their calculations are not for the faint of heart.
22:53Modeling what happens when two giant objects create a storm in the sea of spacetime takes some serious math and months of supercomputing.
23:03This is the orbit of a small black hole around a bigger black hole.
23:07And it's literally making a knocking sound on the drum where the drum is spacetime itself.
23:12Well, it really sounds like a knocking.
23:15It starts to get a higher frequency and happen faster until it falls into the big black hole and goes down the throat.
23:24And then the two will ring out together and form one black hole at the end of the day.
23:28And then it just sort of, you know, chirps up.
23:31Because black holes stir up the space and time around them so much, the orbit of one black hole around another looks nothing like the orbit of Earth around the sun.
23:43An orbit can come in around a black hole and do an entire circle as it loops around before it moves out again.
23:49So instead of getting an oval, you get a three leaf clover that processes around.
23:54This clover leaf pattern keeps coming out of the simulations.
23:59Jana was shocked.
24:01Because this picture of how two of the heaviest objects in the universe move around one another
24:07bears an uncanny resemblance to the way two of the lightest objects move around one another.
24:12The tiny protons and electrons inside an atom.
24:17We can build a kind of classical atom out of a big black hole like a nucleus
24:22and a light black hole which acts like an electron.
24:25And together they form a real atom in a sense.
24:29How could an object that weighs so much behave like a subatomic particle that weighs so little?
24:37When we talk about ordinary objects or people even, they are never exactly the same.
24:43I mean you could try to clone me and still the different copies of me would not be exactly the same.
24:49In that sense, people and ordinary objects are not like fundamental particles.
24:53They are distinguishable.
24:55But the black hole is quite different from that.
24:57Black holes are like fundamental particles.
24:59And that is very surprising because they are huge macroscopic objects.
25:03Right now, this idea is only a tantalizing hunch.
25:07But in just five years, supersensitive detectors should be able to pick up the ripples in space created by two massive black holes spinning around one another.
25:17And they'll tell us whether they really do behave like tiny atoms.
25:23But this connection between the very big and the very small has already sparked a war between two of the greatest living physicists.
25:32One of them, Stephen Hawking.
25:36The other began life as a plumber in the South Bronx.
25:40And is now using black holes to develop the most revolutionary idea in physics since Albert Einstein.
25:47An idea that literally turns reality inside out.
25:52The first step in joining the physics of the very large and the very small came in 1974 from the mind of Stephen Hawking.
26:07The theory of the very small quantum mechanics predicts that empty space should be sizzling with particles and antiparticles.
26:16Popping into existence in pairs and then annihilating one another an instant later.
26:22These particles exist for such a short time they are not considered part of reality.
26:28Physicists call them virtual particles.
26:31But Hawking realized there was one special place in the universe where these particles could become real.
26:38Around a black hole there is an invisible line in space called the event horizon.
26:43Outside that line the hole's gravity is just too weak to trap light.
26:49Inside it nothing can escape its pull.
26:52If a pair of virtual particles formed just outside the event horizon, then one of the pair might travel across that point of no return before being able to recombine.
27:04Falling into the black hole and leaving its partner to escape as real radiation.
27:09Hawking radiation.
27:11If Hawking is right, black holes should not actually be black.
27:17They should shine.
27:19Ever so faintly.
27:22No one has ever detected Hawking radiation from the rim of a black hole.
27:27In fact, it's so faint and black holes are so far away that it would probably never be possible.
27:34But Jeff Steinhauer thinks he's found a way to test Hawking's theory and send shockwaves through the world of physics.
27:42He's the only person on the planet who has seen a black hole from up close.
27:48In fact, he's learned how to create one.
27:51My black hole is in no way dangerous.
27:54It's a sonic black hole.
27:56It can only absorb sound waves.
27:58It's only made of 100,000 atoms, which is very little matter.
28:02And I'm sure that my neighbors would love that I would put a sonic black hole around my apartment, but it's not going to happen.
28:10When he's not jamming in the basement of the physics department at the Technion in Israel, he's upstairs in his lab.
28:19Jeff Steinhauer's recipe for making a sonic black hole begins with a tiny sample of rubidium atoms, chilled down to minus 459 degrees Fahrenheit.
28:30While I was working with these very cold atoms, I stumbled across a phenomenon.
28:35When the atoms are actually flowing faster than the speed of sound, then if there are sound waves trying to travel against the flow, they can't go forward.
28:44And this is analogous to a real black hole where light waves cannot escape due to the strong gravitation.
28:50Even though this black hole traps only sound, not light, the same laws of quantum mechanics apply to it as they do to its cosmic cousins.
29:01If Hawking's theory about black holes is correct, Jeff should be able to detect tiny sound waves escaping.
29:08There should be pairs of sound waves, one on the right side and one on the left side.
29:13Due to the quantum physics, they will suddenly be created.
29:17This is the elusive Hawking radiation.
29:20Jeff has not detected this elusive radiation yet, but he believes he should within a year as he refines his experiment.
29:30No one will await that news more keenly than Leonard Susskind.
29:37He has spent much of the last 30 years thinking about Hawking radiation and being deeply troubled by what it means.
29:45Today, he's one of the world's leading theoretical physicists, but that's not the way he started.
29:53When I was 16 years old, I was a plumber.
29:56Fixing toilets and sewers and so forth in tenement buildings in the South Bronx was not what I wanted to be doing for the rest of my life.
30:05Whenever I make analogies about physics, it always seems that they have something to do with plumbing.
30:12The analogy that I've used over and over about black holes is water going down a drain.
30:18The invention of string theory, which has a lot to do with tubes.
30:23Some people even say this must have been Susskind the plumber.
30:27Leonard Susskind's fascination with black holes began 30 years ago when he listened to a talk by Stephen Hawking,
30:36a talk that triggered a violent reaction.
30:39I first heard Stephen Hawking give a lecture up in San Francisco in which he made this extraordinary claim
30:47that black holes seem to violate the very, very fundamental principle of physics called conservation of information.
30:56Seven years after his groundbreaking work on black hole radiation, Hawking had taken the idea to its logical conclusion.
31:05For every ounce of material a black hole absorbed into its core, it would radiate away an equivalent amount of energy from its event horizon.
31:15But since there is no physical link between the center of a black hole and its event horizon, the two processes could not share any information.
31:25Now this was a disaster from the point of view of the basic principles of physics.
31:30The basic principles of physics say that you can't lose information.
31:34Let me give you an example.
31:37Here's a sink of water.
31:39Let me imagine sending in a message into that sink of water in the form of Morse code by dropping in this red ink.
31:46Drip, drip, drip, drop, drip.
31:49You see the red ink swirling around.
31:52But if you wait a few hours, what will happen is that red ink will get diffused throughout the water.
31:58You might say, well, my goodness, the information is clearly lost.
32:03Nobody can reconstruct it now.
32:05But down at the very core of physical principles, no, that information is there.
32:11If you could watch every single molecule, you could reconstruct that message.
32:17It may be much too hard for human beings to be able to reconstruct and to follow all those motions, but physics says it's there.
32:28But Stephen Hawking claimed there are special places in the universe where that law can be broken.
32:36What happens when the information goes down the black hole?
32:40The answer, according to Stephen, was it goes down the drain and disappears completely from our universe.
32:48This was a fundamental violation of the most sacred principle of physics, and I was personally truly shocked.
32:59If what Hawking claimed was right, it would mean most of modern physics had to be seriously flawed.
33:11Black holes would spend their lives eating stars and leave no record of what they'd done.
33:18Nothing else in the universe does this.
33:20The fiery blast of a nuclear bomb might vaporize everything in sight, but all that information is still in this universe,
33:28no matter how scrambled.
33:30Black holes, according to Hawking, don't scramble information.
33:35They completely destroy it.
33:37That was 1981, and from that time forward, I was hooked.
33:43I could not let go of the question of black holes.
33:46This squabble soon grows beyond these two men and engulfs all of physics.
33:52At stake is more than just bragging rights for the winner.
33:56It turns out to affect the very way we perceive the universe.
33:59There may be a hundred million black holes scattered across the Milky Way.
34:13Anything that strays too close to these dark remnants of burned out stars will be pulled in by an intense gravitational field.
34:23But what actually happens to the stuff that falls into a black hole?
34:30Is it simply wiped out of existence?
34:33Or do black holes remember?
34:36These are the battle lines of the Black Hole War.
34:39A battle with repercussions that the men who started it could never have imagined.
34:46It's a war between two giant minds.
34:50On one side, the famous physicist Stephen Hawking.
34:53On the other, Leonard Susskind, one of the creators of string theory.
34:58Stephen Hawking argues black holes destroy what they swallow without a trace.
35:03Leonard Susskind passionately disagrees.
35:06But for ten years, he struggled to find anything wrong with Hawking's concept of how black holes radiate away the matter they swallow.
35:15It was thought to be inconceivable that somehow the things which fell into the black hole could have anything to do with the Hawking radiation which was coming out from very, very far from where the particles fell in.
35:31Then he began looking at the problem in a new way.
35:36Call it the Dead and Alive Paradox.
35:39It's a cosmic thought experiment starring an astronaut named Alice, her friend Bob, and a black hole.
35:47Bob is orbiting the black hole in a spaceship and Alice decides to jump into the black hole.
35:53What does Bob see and what does Alice see?
35:58Well, Bob sees Alice falling toward the black hole, getting closer and closer to the horizon, but slowing down.
36:06Because the gravity of the black hole severely distorts space and time near the event horizon,
36:12Einstein's theory of relativity predicts that Bob will see Alice moving slower and slower until she eventually stops.
36:21So, from Bob's point of view, Alice simply becomes completely immobile with a big smile on her face.
36:29And that's the end of the story.
36:31It takes forever for Alice to fall through the black hole.
36:36On the other hand, Alice has a completely different description of what happens.
36:41She just falls completely cleanly through the horizon, feeling no pain, no bump.
36:47It's only when she approaches the interior, when she starts to feel uncomfortable.
36:53At that point, she starts to get more and more distorted, and I don't want to go into in detail what happens to her.
37:00It's not pretty.
37:01These two descriptions of the same events appear to be at odds.
37:05In one, Alice is stuck at the event horizon.
37:09In the other, she sails right through.
37:12In one version, she dies.
37:15In the other, she's frozen in time, but alive.
37:20But then, Leonard Susskind suddenly realized how to resolve this paradox and win the black hole war.
37:28I began to think that some of the ideas that we had developed for string theory could help resolve this problem, this paradox.
37:37One way of thinking about string theory is that elementary particles are simply more than meets the eye.
37:43You see this propeller here?
37:45This propeller, when it's spinning very, very rapidly, all you see is the central hub.
37:50It looks like no more than a simple particle, but if you had a really high-speed camera that could catch it as it was spinning,
38:00you would discover that there's more to it than you realized.
38:03There's the blades, and the blades would make it look bigger.
38:07In string theory, an elementary particle has vibrations on top of vibrations.
38:13It's as though this propeller had on the ends of its blades more propellers, and those propellers had propellers on the ends of their blades, out to infinity.
38:25Each propeller going faster than the previous one, as you would catch it with a higher and higher-speed camera,
38:32you would see more and more structure come into focus, and the particle would seem to grow.
38:38It would grow endlessly until it filled up the whole universe.
38:42Then it realized that a black hole is like an ultra-high-speed camera.
38:51It appears to slow objects down as they approach the event horizon.
38:56Time for another thought experiment.
38:58The black hole, Bob, and Alice are back.
39:01But this time, Alice has an airplane, powered by a string theory propeller.
39:07For Alice, not much changes.
39:10She sits in the cockpit and flies right over the event horizon, all the time seeing just the central hub of her propeller.
39:19And she meets the same horrible fate at the heart of the black hole, this time accompanied by some plane debris.
39:27Bob's view is very different.
39:30So first he sees the first propeller come into existence.
39:34Then later, when it's slowed down even further, he begins to see the outer propellers come into existence.
39:41Sort of one by one, and the effect is for the whole propeller to get bigger and bigger and bigger and grow,
39:48and eventually be big enough to cover the whole horizon.
39:57These two views no longer seem so irreconcilable.
40:01Alice is either squished at the center of the black hole or smeared all over the event horizon.
40:07Leonard has a name for this new way of seeing things, the holographic principle.
40:14I began to think, hey wait a minute, this sounds awfully much like a hologram.
40:20There's Alice at the center, and if I look at the, let me not call it the horizon, let me just call it the surface, the film,
40:28all you see is a completely scrambled mess, and somehow they're representing exactly the same thing.
40:34Leonard's idea that the event horizon of a black hole is a two-dimensional representation of a three-dimensional object at its center
40:44solves the problem of information loss.
40:47Every object that falls into a black hole leaves its mark both at the central mass
40:53and on the shimmering hologram at the event horizon.
40:57When the black hole emits Hawking radiation from the horizon, that radiation is connected to the stuff that fell in.
41:05Information is not lost.
41:10In 2004, at a scientific conference in Dublin, Hawking conceded defeat.
41:15Black holes do not destroy information.
41:19Leonard Susskind had won the black hole war.
41:23But he'd done much more than that, because the theory does not merely apply to black holes.
41:29It forces us to picture all of reality in a new way.
41:34It's as if there were two versions of the description of you and me and what's in this room.
41:40One of them being the normal, perceived, three-dimensional reality,
41:47and the other being a kind of holographic image on the walls of the room, completely scrambled, but still with the same exact information in it.
41:57That idea has now, it's not an idea anymore.
42:01It's a really basic principle of physics, that information is stored on a kind of holographic film at the edges of the universe.
42:11In a sense, three-dimensional space is just one version of reality.
42:17The other version exists on a flat holographic film, billions of light years away, at the edge of the cosmos.
42:26Why these two realities seem to coexist is now the biggest puzzle physics needs to solve.
42:32One of the big challenges that comes out of all of this is understanding space itself.
42:38Why is space three-dimensional when all of the information that's stored in that space is stored as a two-dimensional hologram?
42:48A black hole raises these challenges and really sharpens these challenges,
42:53because it's practically a place where ordinary space doesn't exist anymore.
42:57So, if I'm asked questions about how space emerges, I will simply have to say,
43:03well, we're thinking about it. We don't understand it.
43:06Black holes have been a source of fascination for almost a century.
43:12We've thought of them as time machines, shortcuts to parallel universes,
43:18as monsters that will one day devour the Earth.
43:21Well, any of these ideas may turn out to be true one day.
43:25But right here, right now, black holes have a profound effect on you and me.
43:33Their shimmering holographic surfaces seem to be telling us that everything we think is here
43:40is mirrored out there, at the very edge of our mysterious universe.
43:48How long has the space been?
43:50There's only one place where they feel on the horizon with each other.
43:52The sun is a large part of these areas, where the sun is a mountian,
43:56The sun is at the very end and the sun is at the very end.
43:58The air is a city that contains sprang in the air.
44:00The sun is at the sky in the air, the sun is completely open,
44:02The sun is a kind of the sun, the sun is bats to the sky in the air.
44:04The sun is a great event.
44:06The sun is at the sun is a strong ecosystem,
44:08The sun is aasy in the sky in the air.