BBC Time_4of4_Cosmic Time
Transcript
00:00Imagine, somewhere in our universe, an utterly strange world, a place where time could both
00:21speed up and slow down, from where we could journey into the past and the future, somewhere
00:31time could even split in two.
00:37Incredibly, this is no alien world.
00:43It's our world, and it's all around us.
00:48Now for the first time, science is enabling us to see what for thousands of years has
00:54remained hidden...
00:55the true nature of time.
01:18We live in a world governed by time.
01:35From the tiniest of cells to the most distant of stars, our entire universe is subject to
01:40the beat of a constant clock.
01:47Because time is everywhere, we think we know it.
01:51We know that it's regular and it moves in one direction.
01:56We know that it's universal and eternal.
02:00And we know that it never, ever stands still.
02:06But how can we be so sure?
02:10How much of what we think we know about time is really true?
02:18In this program, I want to get to the bottom of what time really is.
02:23And in doing so, I'll be challenging some of our most cherished beliefs.
02:30As a theoretical physicist, it's this hidden time that has always fascinated me throughout
02:36most of my professional career.
02:39I'm going to explore the very limits of our universe in order to uncover just what time
02:45really is.
02:46And in the process, I'll be revealing an astonishing secret, nothing less than our ultimate destiny,
02:54the future of the universe and the fate of time itself.
03:16Of all our assumptions about time, one of the most obvious is that time is regular,
03:24that a minute will always be a minute for everyone, everywhere.
03:32Here in the Swiss Alps, I'm searching for something that challenges this assumption,
03:37something that if time was as regular as we think it is, shouldn't exist at all.
04:07Well, I'm now 11,000 feet above sea level and I'm out of breath and actually feeling
04:17a little bit dizzy.
04:19Now the bad news is I still have a ways to go to reach the top of the Alps because what
04:25I'm looking for is something that becomes more plentiful the higher you go.
04:51And this is what I've come to see.
04:53It's a particle counter, telling me that the air around me is full of tiny particles
04:59called muons that come from all the way out there.
05:12Muons are short-lived particles formed when cosmic rays from space collide with the upper
05:19atmosphere.
05:26But the big mystery is how they come to be down here on Earth.
05:34Because with a lifespan of just two millionths of a second, muons should only live long enough
05:40to travel a few hundred meters.
05:43And yet, here they are, after a journey of several miles, something that shouldn't be
05:49possible.
05:53So what exactly is going on?
05:56The answer to this mystery, the reason why muons can reach us at all, is so extraordinary
06:03that from the moment it was first proposed, it literally rewrote the rulebook of time.
06:27Less than a hundred miles from the Alps lies the affluent city of Bern.
06:35In the early 1900s, this was home to a young German physicist who would change the way
06:40we looked at time forever.
06:45His name was Albert Einstein, and he's been my hero for the past 50 years.
06:55In 1905, in this, his first floor apartment, Albert Einstein put the finishing touches
07:01to his radical new theory, special relativity.
07:10One of five papers published by Einstein in 1905, special relativity would make us think
07:17about time in a completely new way.
07:34Einstein's astonishing claim was that time was not regular at all.
07:39It could beat at different rates.
07:43Time changes, depending on relative speed.
07:54Imagine for a minute that my tram is capable of traveling at phenomenal speed, just a fraction
08:01less than the speed of light.
08:06According to special relativity, the rate at which time flowed on this speeding tram
08:11would depend on whether you were on board or looking in from the outside.
08:19So while for me, it would seem as though time was passing perfectly normally, for me, sitting
08:27on the pavement, assuming I could somehow peer inside the tram, time would assume a
08:33totally different quality.
08:40Looking in from the outside, I'd sense that time on board the tram was passing much more
08:45slowly.
08:48That's because, according to Einstein, the faster an object moves, the slower its time
08:53will run to someone observing from the sidelines.
08:58In other words, time can vary.
09:01It's all a matter of speed.
09:06That explains the mystery of how our muons reach the earth.
09:16Because muons travel near the speed of light, relative to the earth, their clocks have slowed
09:21down, so much so that they exist long enough to reach the earth and be detected.
09:30Time for our muons has stretched.
09:33It beats very differently to the way it does for us.
09:48Now the effects of special relativity are so small that they have no impact on our daily
09:53lives.
09:54But the fact that they are there at all has changed everything.
09:58Because if time is relative, if time is flexible, then our belief in the immutability of time
10:05is wrong.
10:07And if we can be wrong about something as basic and as fundamental as this, then in
10:12what other ways might we be mistaken?
10:15Do either of you play cards?
10:27I just play a little poker.
10:28You play poker?
10:29So you didn't shuffle cards, can you?
10:30Oh, no.
10:31No?
10:32I let someone else shuffle.
10:33So do you shuffle like this?
10:34Yeah.
10:35Yeah?
10:36That's called the overhand shuffle.
10:37OK.
10:38Because if you don't shuffle cards that well, you can try this one.
10:39This one's pretty good.
10:40It makes a complete mess of the deck of cards.
10:41Some cards go back to face, and some are like back to back.
10:46Our complete trust in temporal order is the reason why we delight in the obvious impossibility
10:52of magic tricks.
10:53Back to face and face to back.
10:54So it makes a total mess.
10:55I'll just show you.
10:56Some of the cards, they're like face to back.
10:57Not very good for playing poker or blackjack.
10:58But if you press the button here, press the button, snap your fingers, they all come out
10:59the right way, which is rather handy.
11:00That's pretty cool, isn't it?
11:01That's pretty good.
11:02Wow.
11:03My job as a magician is to manipulate people's fates.
11:04I'm a magician.
11:05I'm a magician.
11:06I'm a magician.
11:07I'm a magician.
11:08I'm a magician.
11:09I'm a magician.
11:10I'm a magician.
11:11I'm a magician.
11:12I'm a magician.
11:13I'm a magician.
11:14My job as a magician is to manipulate people's fates.
11:16Hi.
11:17How are you doing?
11:18Can you stop me for a moment?
11:19People realize that things can't disappear and reappear.
11:22I'm going to run through the cards, and you say stop wherever you like.
11:25If you do your job properly, you can make it look as though two things can be in the
11:28same place at the same time.
11:32And to that end, essentially, you can make it look as though you're manipulating space
11:35and time.
11:36Have you ever seen magicians use these before?
11:37Yeah.
11:38I've seen them.
11:39I'll show you a trick with two of them.
11:40OK.
11:41So can you hold your hand out for me?
11:42Yeah, sure.
11:44A classic way of demonstrating the manipulation of space and time can be done using the sponge
11:48ball trick.
11:49It's 100 years old, but it's great.
11:53But essentially, you take a ball in your own hand, and the spectator holds a ball.
11:58And you can do it in such a way that it looks as though you can manipulate space and time,
12:01and it looks as though the ball has disappeared from your hand.
12:04So when the spectator opens their hand, suddenly they have two.
12:07That ball has vanished from your hand, and it's reappeared in theirs.
12:13But believe it or not, this sort of behavior isn't always an illusion.
12:18Beneath the surface of our common sense world lies another world, where magical things really
12:25do happen, where the impossible can be made real, and where time can perform the most
12:32incredible tricks.
12:38That place is inside the atom.
12:43For years, scientists had assumed that in our universe, there was nothing smaller than
12:48an atom.
12:50The very word atom, in fact, comes from the Greek word for indivisible.
12:55Then in 1897, an Englishman named J.J.
12:58Thompson made an astounding discovery, that inside the atom, there were even smaller particles
13:04called electrons.
13:07That discovery opened the door to the amazing world inside the atom, a world where everything,
13:14including time, behaves in a truly alien fashion.
13:29Physicist Ian Walmsley has been studying this microscopic world for almost 30 years.
13:37When we get inside the atom to this world of subatomic particles, the ideas that we
13:43have about the way the world works completely have to change.
13:46We can't think in the same sorts of common sense terms that we think of in everyday experience.
13:56In fact, this subatomic universe is so strange that time becomes chaotic.
14:04A startling discovery that emerged from the study of light.
14:13Light consists of individual particles called photons, known for their wave-like properties.
14:23Waves have a very interesting sort of phenomenon.
14:25It's called interference.
14:29When two waves come together, they can add together and reinforce one another, or they
14:34can cancel one another out.
14:37And this interference is a ubiquitous property of all waves, not just water waves, but also
14:42light waves.
14:45But in the early 1900s, scientists noticed something very odd about these light waves,
14:52something that proves that time isn't always ordered.
15:00In this reworking of a classic experiment, once described as the most beautiful in physics,
15:06single photons, or particles of light, are fired down a darkened tube towards a camera,
15:13one at a time.
15:16So we have here a very simple apparatus.
15:18It consists of a light bulb at this end and a camera at the other end that can register
15:24the light.
15:25And in between, the light encounters a pair of slits etched onto this piece of glass through
15:33which the photons can pass on their way from the source to the camera.
15:41The purpose of the experiment is to study the behavior of photons as they travel from
15:46one end of the tube to the other.
15:49To begin with, the individual photons are sent through just one of the slits.
15:55Each of these dots arriving represents a single photon.
16:01So most of them are coming along this point.
16:04Some of them lie above or below that point, but the distribution is nice and smooth.
16:09Now the second slit is opened up and the experiment repeated.
16:14Each single photon must still pass through one of the two slits, so the results should
16:20still be the same.
16:22Classical logic would say that what we would get when we open both slits is just the sum
16:26of these two detection patterns.
16:30But what we actually find is this, an interference pattern, something that should be impossible.
16:41What that implies is that the single photon is somehow going through both slits at the
16:47same time.
16:48It's not making a choice as to go through one or the other, but is going through both
16:52simultaneously.
16:55In other words, each photon exists not just in two places, but also in two times.
17:02So we have this very strange notion that this single photon can be in two different places
17:08at once.
17:09It's delocalized.
17:12But we can think also of a single photon being in two different times.
17:18So both space and time have become delocalized and fragmented.
17:27On the surface, we feel time is ordered.
17:31But that belies a different reality.
17:35We are totally unaware of the chaos and unpredictability that lies deep within the atom.
17:41Not surprisingly, our understanding of time comes from our everyday experience.
17:49And it's for this reason that we cling to yet another of our assumptions about time,
17:54that it never stands still.
17:58In fact, one thing that sets us apart as humans is the knowledge that time waits for no man.
18:05That time doesn't merely exist, but is constantly flowing.
18:11But one discovery proved that this isn't always the case.
18:15Dr. Tom Bolton of the University of Toronto made more than 40 observations of Cygnus X-1.
18:33In 1971, astronomer Tom Bolton embarked on a project to observe a mysterious X-ray source
18:41called Cygnus X-1, an object assumed to be a distant neutron star.
18:51I started to look at Cygnus X-1 because I thought it would be a good opportunity to
18:55determine the mass of a neutron star.
19:00And nobody had done that yet.
19:03Cygnus X-1, some 8,000 light years away, is one half of what's called a binary system.
19:11The binary system is a pair of stars that are gravitationally bound to each other, just
19:19like the Earth is bound to the Sun, and they orbit about their mutual center of mass.
19:28By measuring the speed and orbit of X-1's binary partner, Tom was able to work out the
19:34mass of his neutron star.
19:37But the figure he arrived at was far, far bigger than the one he'd been expecting.
19:44That turned out to be about 10 solar masses, with a significant error, but still way too
19:52big to be a neutron star.
19:56So I had to start thinking about what are the alternatives if it's not a neutron star.
20:03There was only one possibility that fitted the data, but it was something that few people
20:09believed actually existed.
20:13As far as I knew, the only object that would fit that description and produce X-rays was
20:19a black hole.
20:21So I said so.
20:25Tom's discovery caused a sensation.
20:30The first incontrovertible proof that far from being a figment of people's imagination,
20:36black holes were in fact very real indeed.
20:46Since their discovery 25 years ago, we now know that the universe is teeming with them.
20:51It is how black holes affect time that make them so unusual.
21:01Black holes are so massive that their gravitational pull approaches infinity.
21:12And according to Einstein's second theory, that of general relativity, very intense gravity
21:19slows time in a similar way to moving at very high speed.
21:25So if you were to watch someone fall into a black hole, you'd notice that their time
21:35was beginning to slow down, so much so that at the very center, where the gravitational
21:41pull is infinite, time would stop altogether.
21:46Time would cease to exist.
22:07That there are places where time can come to a grinding halt seems frankly incredible.
22:16That's only because we live in such a uniform corner of the galaxy, warmed by a benevolent
22:24sun far from any extremes of gravity.
22:32Beyond our everyday environment, time is very different.
22:37Not only is it irregular, it's also chaotic.
22:41It can even stand still.
22:44But for all its vagaries, there's one thing that time never seems to do, and that's turn
22:51back on itself.
22:59Which when you think about it, is a little odd.
23:03After all, my physical environment offers me enormous freedom.
23:12The thing is, the laws of physics don't have any problems with time running backwards.
23:18So we physicists believe that it just might be possible to build a time machine.
23:24The only obstacle we face is one of engineering.
23:30That's because the theoretical blueprint for our time machine already exists.
23:39A machine that's secret lies deep within our microscopic universe.
24:01At the tiniest subatomic level, the fabric of space and time becomes so unstable that
24:07it starts to behave like a foam, its surface alive with tiny bubbles momentarily popping
24:14in and out of existence.
24:17We call this quantum state the space-time foam.
24:24It's thought that contained within this foam are objects called wormholes, tiny passageways
24:31between two points in space and time.
24:36The secret to building a time machine is to stabilize the space-time foam long enough
24:42to make one of these wormholes permanent.
24:46And the way we do that is by subjecting it to enormous amounts of energy.
24:57I'm standing 100 meters above what will be, when it's finished, the world's most powerful
25:03particle accelerator.
25:04This machine, scientists hope, will help to unlock some of the secrets of the mysterious
25:09world of subatomic particles, the building blocks of our universe.
25:26This tunnel is 27 kilometers in circumference and it houses the accelerator.
25:32Inside this chamber, two beams of subatomic particles will be traveling in opposite directions,
25:38boosted to near the speed of light.
25:47As the protons within the beams collide, they shatter into even smaller particles, releasing
25:54bursts of energy roughly half a million times greater than those inside a nuclear explosion.
26:04But even the most powerful accelerator on this planet can't produce enough energy to
26:09stabilize the space-time foam.
26:12To do that, our particles would have to be moving even faster.
26:16And that would require an accelerator of truly enormous proportions.
26:33So big, in fact, we would need to build it in space.
26:56Now we know that if you smash particles together at extremely high velocities, eventually you
27:03create something called a quark-gluon plasma, an extremely hot, high-energy cauldron of
27:11matter with a temperature exceeding 10 trillion degrees.
27:17By adding even more energy, blasting the plasma with lasers, we can finally stabilize space-time
27:26foam long enough to pluck out a minuscule wormhole.
27:33The next task is to enlarge it, and even that is scientifically possible.
27:39In 1948, a Dutch physicist named Hendrik Casimir introduced us to a mysterious new force called
27:47negative energy, complete with anti-gravitational properties.
27:55So far, we can only create minute quantities of this in the laboratory, but one day, if
28:01we can create enough negative energy, we might be able to increase the size of a wormhole.
28:08And this is how we think our wormhole would look, each end a sphere held in place by an
28:15electric field invisibly connecting two points in space and time.
28:22By subjecting one end of the wormhole to a huge gravitational field, we could bring
28:28its clock almost to a stop.
28:34This turns our wormhole into a time machine, both ends existing in the same place, but
28:42at different times.
28:47Our ability to build such a machine is still some way off.
28:56But just knowing that time travel is possible is enough to turn yet another of our assumptions
29:02on its head.
29:05So far, we've seen how time, which appears to be so regular, can in fact be quite flexible.
29:12We've seen how time can behave in such unpredictable ways.
29:17And as we understand more about time, it's even becoming possible to solve perhaps the
29:23greatest mystery of them all, whether time is eternal.
29:31Over the last hundred years, it's become increasingly clear that our universe, and hence time itself,
29:37had a beginning.
29:38But that raises another question.
29:40If time had a beginning, will it also have an end?
30:09History has long pondered the origins of time and the universe.
30:18Almost every religion that has ever existed has had its own creation myth.
30:25When I was a child, I remember being so confused about how we got here.
30:30And that's because I was brought up in between two faiths with two very different views on
30:35creation.
30:46On the one hand, there was Christianity.
30:49At Sunday school, I learned all the Old Testament stories, among them the book of Genesis, describing
30:57how the universe came into being in a single moment of divine creation.
31:05On the other hand, my parents were both Buddhists.
31:09From them, I discovered that Buddhists believe the universe is timeless, without either beginning
31:16or end.
31:23For some time, I continued to struggle with these two seemingly incompatible doctrines.
31:33Either the universe had a beginning, or it didn't.
31:36Either time is eternal, or it isn't.
31:42It's only in the last 40 years or so that we think we've found the answer, an answer
31:48that comes from the furthest reaches of space.
31:58The amazing thing about looking up into the night sky is that it's like gazing at a cosmic
32:03map of the past.
32:05Every planet, every star, is like a snapshot taken when their light first left them.
32:11The further the star, the more ancient its origins.
32:15But for centuries, the limits of the universe were a total mystery, until one man peered
32:21further into the heavens than ever before.
32:25In doing so, he gave us a better understanding, not just of our universe, but of time as well.
32:45Perched high in the hills above Los Angeles in Southern California is the Mount Wilson
33:03Observatory.
33:06In 1919, it saw the arrival of an ambitious new astronomer named Edwin Hubble.
33:15Don Nicholson remembers Hubble from regular visits to Mount Wilson as a young boy.
33:23Hubble certainly as an astronomer was a very skilled, a very dedicated, a very effective
33:33astronomer.
33:35He was highly respected for his professionalism.
33:42Hubble's arrival more or less coincided with completion of the world's then most powerful
33:47telescope, capable of looking further into space and hence further back in time than
33:55ever before.
34:03Most astronomers felt that our galaxy was the universe and for many that even that the
34:10solar system was at the center of that universe.
34:15But on the evening of October 4th, 1923, Edwin Hubble noticed a tiny speck deep within the
34:23Andromeda Nebula.
34:29Before that time, there was no telescope in the world, for example, that could resolve
34:34individual stars in these spiral nebula.
34:39And so there was belief that they were simply gaseous objects in our own galaxy.
34:47But Hubble was able to prove that his speck was indeed a star and incredibly that it was
34:54more than a million light years away.
34:57Much too far to be part of our own galaxy.
35:02In one stroke, Edwin Hubble had destroyed the notion that our Milky Way was the sum
35:07total of the universe.
35:09And if the universe was much bigger, then it also had to be far, far older.
35:27Hubblecast is produced by ESA, the European Space Agency, and the European Space Agency.
35:56Every Thursday, a whole bunch of fans congregate at this drag strip to enjoy the sights, the
36:01smells, the sounds of these muscle cars.
36:09These unmistakable sounds are created by the same phenomenon that enabled Edwin Hubble
36:15to make his second great discovery.
36:22The sound of a car will always depend on the direction it's traveling.
36:29A car moving towards me sounds high-pitched, but a car moving away from me sounds lower-pitched.
36:40This shift in pitch, known as the Doppler effect, is due to the fact that at the front
36:46of a moving car, sound waves are compressed.
36:51While at the back, they're stretched out.
36:59And what's true of sound is also true of light.
37:03As light moves away from us, its waves, too, become stretched.
37:10By measuring this effect, called the redshift, in one galaxy after another, Edwin Hubble
37:16realized that not only were they all incredibly distant, they were all moving away from us.
37:25In other words, the universe was expanding.
37:29If the universe was expanding, then it had to be expanding from something.
37:38From an event whose soundtrack is still with us today.
38:09What I'm listening to now are some of the sweetest sounds ever, the sounds of creation.
38:14Waves of light from the beginning of time have been stretched so much that we can't
38:18really see them anymore.
38:19Instead, we can pick some of them up on the radio in the form of static.
38:27Although he didn't know it at the time, Hubble's discovery that the universe was expanding
38:31led to one of the most important breakthroughs ever made about time, the Big Bang.
38:40Once there was nothing, not even time.
38:45But 13.7 billion years ago, it seems that this nothing became everything.
38:54And a tiny dot of infinite density spontaneously expanded at a phenomenal rate, giving birth
39:04to the universe and everything within it, including time.
39:14But if time had a beginning, does that also mean that time will have an end?
39:33Just as many cultures have their own creation myth, so most also have their own take on
39:39how the universe will end.
39:44In the 11th century, the ancient Norse myth of Ragnarok predicted that the universe, and
39:50time along with it, would end in a desperate battle between the forces of good and evil.
40:02It was believed that this apocalypse would be preceded by something called the Winter
40:08of Winters, an epic ice age during which all the stars would gradually vanish from
40:18the sky.
40:23How the universe will end continues to preoccupy us over a thousand years later.
40:37In 1988, physicist Saul Perlmutter joined this quest to discover the fate of the cosmos.
40:48It seems like a really philosophical question.
40:51Is the universe going to last forever or is it someday going to come to an end?
40:55But in just the last few decades, we finally have both the intellectual tools that Einstein
41:01gave us and the practical measurement tools.
41:12Saul believed that the destiny of our universe was linked to the rate at which it was expanding.
41:20Since the 1930s, we've known that the universe is expanding and everybody's understanding
41:26was that it would be slowing down in that expansion because all of the stuff in the
41:30universe would gravitationally attract all the other stuff, and so it would slow the
41:34expansion down little by little.
41:38This would result in the universe collapsing back in on itself in something called the
41:43Big Crunch, bringing time to an abrupt and violent halt.
41:49Are there any decisions coming up?
41:55Are there any other ones that we're actually going to have to decide something about?
41:59To discover just when the universe and time would end, Saul and his team began to hunt
42:05for extremely rare objects known as supernovae, the aftermath of exploded stars.
42:13There are two things you need to know about a given supernova once you've discovered one.
42:18First, its peak brightness.
42:19That tells you how far away it is and hence how far back in time the explosion occurred.
42:24The other thing is you want to look at its color through its spectrum, and the more it's
42:29been shifted to the red, it's called redshift, the more the universe has stretched since
42:34the time of that explosion.
42:38Painstakingly, Saul and his team began to discover one supernova after another.
42:45After several years of the supernova hunting, we had built up a sample of some 42 supernova
42:51and we were finally ready to go back to ask that question that we began the project with,
42:55what is the fate of the universe?
42:58But the answer they came up with came as something of a shock.
43:04When we finally graphed the results, we found a very surprising result.
43:10Apparently the universe is not slowing down.
43:11It was actually speeding up, and that was the big surprise.
43:20In other words, the universe wasn't headed for a big crunch at all.
43:25So what will its fate be?
43:32Saul's discovery has helped scientists to map out how time and the universe will evolve.
43:38An incredible space epic, separated into five long ages.
43:45The first of these was the primordial age, starting with the Big Bang and the birth of
43:53time.
43:56Lasting only 350,000 years, that's long gone.
44:01We're now 13.7 billion years into the second age, and it's only just beginning.
44:09We live in something called the Stelliferous Era, an epoch that has brought us not just
44:16the stars and the planets, but also every speck of matter in the universe.
44:21One day, a hundred million, million years from now, a mere finger-click in the life
44:27of the universe, this golden age will come to an end.
44:33In its place will come the Degenerate Age.
44:38When the last stars burn out and die, when the planets fall from their orbits, and in
44:45the darkness of space, matter begins to decay.
44:57After a truly unimaginable length of time, only black holes remain.
45:03A fourth age that far exceeds all the time that has ever gone before.
45:11But even black holes don't last forever.
45:14Little by little, their thermal energy will leak away, until ultimately they too disappear.
45:27So what does this mean for the future of time?
45:30Does the death of our universe mean that time is destined to run out?
45:34Or is time really eternal, without end?
45:41Even as the last black hole evaporates, a fifth and final age is beginning.
45:49The age of the photon, in which time finally fragments into total disorder.
45:57When all that remains of our cosmos are invisible, indestructible, low energy, light particles.
46:12For Saul Perlmutter, this cold chaos represents the ultimate destiny for time.
46:21This particular picture of the future of the universe, and we don't know if this will be
46:25the final answer, would have time lasting forever.
46:29There will be no end to the universe in this particular scenario.
46:48So it seems as if both religious traditions that I grew up with are in some sense correct.
46:54Time is eternal, as the Buddhists believe.
46:57But time also came into being at a precise moment, and that fits well with the story
47:03of Genesis.
47:10As we look out to the vastness of time that lies ahead, we begin to notice something truly
47:15incredible.
47:17As we move from one age of the universe to the next, we see that the nature of time itself
47:23begins to change.
47:25Time evolves.
47:26Ultimately, the strange and chaotic behavior that we can only glimpse inside the atom may
47:33in general become the nature of time throughout the entire cosmos.
47:38And if we could somehow hang around to experience it, we might not even recognize it as time
47:44at all.
47:47As just as particles can be in many places at once, so in our quantum cosmos, we might
47:54uncover many universes, each one with a time of its own.
48:01So this new perspective of time over the whole life of the cosmos makes us look at our time
48:08from a new point of view.
48:09The time that we feel passing, the time that we know and trust, may be something of an
48:15illusion.
48:16An illusion that allows us to make sense of our place in this tiny corner of the cosmos.
48:46Transcription by ESO. Translation by —