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00:00The Big Bang. The story of everything. Time. The Universe. Us.
00:11The Big Bang, one, has a cool name, and two, it's the history of our universe. This is it. It's all of us. It's all things.
00:22That's the traditional view. But is it right?
00:28More and more scientists aren't sure.
00:32In the old, outdated Big Bang theory, our universe just popped into existence from nothing.
00:39We talk about it as the beginning of the universe, but what it really is is the end of our understanding.
00:45Astronomers are ripping up the old rules, but that creates new problems.
00:52How can we possibly say that the universe expanded faster than the speed of light?
00:58But are they asking questions with no answers?
01:01What was the origin? Is there even a sense to asking, was there a time before time?
01:07We don't know. We got none, folks. Well, we got some things, but it's tough. It's tough.
01:15It doesn't tell us what happened really at the beginning. This is still an absolute puzzle.
01:20So just how did it all start? The Big Bang theory is a good story, but is it true?
01:30The Big Bang Theory
01:44To begin at the beginning. No space, no time.
01:52Everything in the known universe compressed into a dot smaller than an atom.
01:59Suddenly, out of this, the universe expands.
02:05Stars and galaxies form, creating the cosmos we see today.
02:11The story of our universe starts with a Big Bang, or does it?
02:17So the Big Bang is the observed truth, but there are details that haven't been quite worked out.
02:25There are a lot of things that may have happened. It's just one explanation.
02:31Science isn't about being right all the time. It's about being wrong.
02:36And we could absolutely be wrong about a major component in our understanding of the universe.
02:42We're putting one of science's greatest stories to the test.
02:47The Big Bang sure sounds like an explosion, but was it?
02:53An explosion is a sudden release of energy from one point, usually generating light, heat, pressure, and a bang.
03:07But did the Big Bang even explode?
03:12When you hear the term bang, you think of a noise, but you have to realize that it's sound waves propagating through air.
03:17So after the Big Bang, there's no air. There was no air. There's no way to hear anything. So in that sense, it was silent.
03:23So the Big Bang didn't bang, but to make the universe, it must have pushed out stuff. Lots of stuff.
03:36Every explosion has an ignition point. What about the Big Bang?
03:42So if you were to only think of the Big Bang as an explosion, you would very rightly ask, well, where's the center of that explosion? Where is the center of the universe?
03:52There was no central point. There's nowhere in the sky you can point and say, that's where the Big Bang was.
03:57The Big Bang is everything. The Big Bang happened here, where I'm sitting. The Big Bang happened on the other side of the planet.
04:05The Big Bang happened in the Andromeda galaxy. The Big Bang occurred throughout the universe simultaneously.
04:13During an explosion, debris fires out from the center.
04:20This debris spreads out unevenly, with different sized pieces landing at different distances from the blast center.
04:28But did the Big Bang shoot material out in this explosive manner?
04:35For clues, you need to search the night sky.
04:40One of the things that's really very striking about the universe when you simply take a telescope and start looking in different directions,
04:47is that it, roughly speaking, looks the same in all directions.
04:51Although the universe is peppered with individual galaxies and galaxy clusters, the big picture is what astronomers call homogeneous.
05:01When we say the universe is homogeneous, it means it's almost exactly the same on very large scales with very, very little differences. It's perfectly smooth.
05:10If we believe the classic Big Bang story, the same amount of material was shot out over the same distance in all directions.
05:19Our smooth, homogeneous universe doesn't appear to be the result of what we know as an explosion.
05:27It wasn't big, and it wasn't a bang.
05:30The Big Bang was not an explosion like a grenade or something like that.
05:35It wasn't a bang.
05:37The Big Bang was not an explosion like a grenade or a bomb or dynamite where there is material rushing out from a common center.
05:47It's not like there's a ring of galaxies that came out from some explosion.
05:51A firecracker explosion is triggered by a fuse.
05:56So, what set off the Big Bang?
05:59What I would say is there's no such thing as what triggered the Big Bang.
06:02You know, we tend to think when something happens, when there's an effect, there's a cause, right?
06:07There's something that made it happen.
06:09But here we're talking about the whole universe.
06:11There's nothing outside the universe to bring it into existence.
06:14The science is clear.
06:16The universe did not start with an explosion.
06:20But if there was no bang, then how did everything start so small and get so big?
06:27The young universe, we do understand.
06:31And the old contemporary universe, we also understand.
06:36We've stitched together this story where we don't fully understand the first few paragraphs of the story, but we know the rest of the book.
06:47How can we get to the bottom of the Big Bang story when we can't even read the first page of the book?
06:54The only hope we have is to search back in time, line by line.
07:00One of the amazing things about being a cosmologist is that telescopes are time machines.
07:08It takes a while for light to get here, so if we look farther out into space, we're really looking back into the history of the universe.
07:16And that's amazing.
07:18The first clues to unraveling the Big Bang mystery came with the introduction of advanced telescopes in the 1920s.
07:30Edwin Hubble was studying the light coming from distant galaxies.
07:33And what he realized was the more distant a galaxy was, the more reddened the light was.
07:39Why should that be?
07:41Well, it turns out that light reddens if a galaxy is moving away from us.
07:44It's called the red shift.
07:45So what he discovered was pretty much every galaxy in the sky was moving directly away from the Milky Way.
07:52This was truly one of science's landmark moments.
07:56Hubble had proved one of the basic principles of the Big Bang story.
08:02Our universe is continuously expanding.
08:05There was only one conclusion to draw.
08:07If you extrapolate that back in time, it looks like everything was coming from one point at one time.
08:13That's the Big Bang.
08:15Hubble's discovery grabbed the headlines.
08:18But the idea of an expanding universe had been proposed two years earlier by a Belgian priest and physicist.
08:27The real idea of the Big Bang comes from George Lemaître.
08:31He realized that if you ran time backwards, back to the beginning of time,
08:35maybe everything coalesced into a single atom, the primeval atom.
08:42Lemaître believed the infant universe was extremely small and dense, squeezed into a single point,
08:52the primeval atom.
08:55Later, scientists would define this point as an infinite entity called a singularity.
09:01But there's a problem.
09:04The singularity and the laws of physics don't mix.
09:09It may be one infinitely small point, but it causes some impossibly big problems.
09:31The Big Bang. For almost a century, it's been science's leading account of how everything began.
09:40But there was no explosion, no bang, and it wasn't big.
09:46In fact, the father of the Big Bang, George Lemaître, claimed everything originated from one tiny point he called the primeval atom.
09:57I think one of the hardest things to grasp about the idea of the Big Bang is that everything you see, everything you've ever known,
10:04every body, every house, every tree, every planet, every moon, every star, every galaxy in the entire universe,
10:11at some point 13.8 billion years ago, was compressed down into a tiny little dot.
10:18In fact, far smaller than a tiny dot.
10:21Infinitely small. A point called a singularity.
10:27And this singularity has been causing astronomers headaches for decades.
10:33It's all because of one word. Infinite.
10:37As soon as you start getting the word infinity, things are infinitely large or infinitely small in physics,
10:43it means that you don't understand everything.
10:46Einstein's general relativity predicts the theoretical existence of singularities.
10:53But in practice, a singularity is where our current laws of physics break down.
10:59We do not understand singularities.
11:02These are some of the theoretical questions that are real conundrums and people are trying to figure out what to do.
11:09The universe is telling us something is going on here that we don't understand quite yet with our math.
11:15Our mathematics are incomplete.
11:18This is a sign that general relativity is not up to the task of describing the earliest, earliest moments of the universe.
11:26General relativity predicts singularities.
11:30But in reality, it doesn't work when things are really tiny.
11:36Einstein's picture of general relativity is incredibly successful at describing the motion of planets around the sun,
11:46the bending of light around massive objects, the growth and expansion of the universe itself.
11:53But it breaks down when gravity gets too strong and gets too small.
11:59General relativity may not be the best tool for understanding the origin of the universe.
12:05Say, for example, you want to weigh some spices in your kitchen.
12:09You can use a kitchen scale. That works really fine.
12:12But now say, on the other hand, you wish to weigh your truck.
12:15That's just not the right tool for it.
12:18So forget relativity.
12:21Maybe another fundamental branch of theoretical physics can help out.
12:26Quantum mechanics.
12:28This deals with the small, the very small.
12:32But what about the infinitely small?
12:35Can quantum mechanics prove the existence of a singularity?
12:39General relativity seems to say that singularities exist.
12:43They're a very straightforward prediction of general relativity.
12:46That doesn't fit well with what quantum mechanics says.
12:49Quantum mechanics tends to fuzz things out. It doesn't really like singularities.
12:53In some theories of quantum mechanics, the science of the small,
12:57there's a limit to how small you can go.
13:00For example, I'm not going to be able to fold up this paper more than seven times.
13:05One.
13:07Two.
13:09Three.
13:11Four. I'm feeling good.
13:13Five.
13:15Oh, man. Six. Can I do it? Can I do it? Can I break the laws of physics? No, I can't.
13:20There's a limit. I just can't go past it.
13:22You can't keep folding paper or space into smaller and smaller fragments.
13:27And according to most laws of quantum mechanics,
13:30you can't have anything infinitely small and infinitely dense.
13:37Singularities seem to be doomed.
13:40So is the Big Bang story wrong, or are we just too dumb to work it out?
13:46Our laws of physics are our best attempts to model with mathematics
13:54all of our observations of the universe.
13:58The universe doesn't care what we think.
14:01The universe doesn't care how we understand it.
14:04This is just our attempts to explain the behavior that we see.
14:09And the earliest moments of the Big Bang is a big example of where our understanding falls short.
14:17Maybe the answer lies in a combination of general relativity and quantum mechanics.
14:24But they won't play ball.
14:26One. Two. Three.
14:28One. Two. Three.
14:30One. Two. Three.
14:32One. Two. Three.
14:34One. Two. Three.
14:36One. Two. Three.
14:38Imagine the rules of quantum mechanics are like the rules that lacrosse players might use to play their games.
14:46And the rules of general relativity are the rules that baseball players would use to play their game.
14:53If you're just watching a baseball game, then they're just following the rules of baseball or general relativity.
15:00If you're just watching a lacrosse game, you're watching the rules of lacrosse play out.
15:05You're watching the rules of quantum mechanics.
15:07But if you take one team from lacrosse and one team from baseball and put them together and ask them to start playing,
15:13they don't even know how to interact with each other.
15:17It's fundamentally different rules that simply don't connect.
15:22Each of these pillars of modern science, quantum mechanics and general relativity, are wonderful in their domain.
15:31But when we try to marry them, which is what we need to do to describe the earliest moments of the universe, it all goes haywire.
15:39Perhaps both teams, playing with a unified set of rules, will shed some light on the Big Bang.
15:47Merging together quantum mechanics and general relativity is the gold standard.
15:52It's what every theoretical physicist would really love to do in the modern age.
15:55We haven't done it yet. We have ideas.
15:58So when I say we haven't done it yet, we don't agree on what the right idea is.
16:02What will ultimately reconcile quantum mechanics with gravity?
16:06Is there even a reconciliation between them?
16:11What do we need? Do we need more surprising, more powerful observations?
16:17New data that we weren't expecting?
16:19Another genius or a thousand geniuses to come along and find the route through the mathematics to marry it?
16:27It's probably all of the above.
16:30So, a major premise of the Big Bang story remains unproven.
16:36But what about Monsignor Lemaitre's other assertions?
16:40Was the infant universe, the primeval atom, intensely hot?
16:45And if so, just how hot was it?
17:00The Big Bang
17:06The story of the Big Bang is based on the discovery that the universe is continuously expanding.
17:13And if we go back in time, this leads to one inescapable conclusion.
17:20So if you run the clock backwards and let the universe get younger, it'll get smaller and smaller and smaller,
17:26and then everything is basically compressed into one point.
17:29The Big Bang story claims this point was infinitely small.
17:35But scientists have not been able to prove the existence of such singularities.
17:41In our universe, we see all galaxies receding from all other galaxies on average.
17:47Imagine if you were looking at trains leaving a station.
17:52If you ran the clock backwards, the trains would converge to the same station.
17:56Now, did these trains come from the same station? Probably.
18:01Did they come from the exact same platform? Probably not.
18:05You can't fit all the trains onto the same platform.
18:08But while physicists can't prove everything came from an infinitely small and dense singularity,
18:15they're convinced the observable universe did expand from one small point.
18:20And this point was incredibly dense and incredibly hot.
18:24Imagine that you and a bunch of friends are in a very large room,
18:28and you're all hanging out and it all seems normal.
18:31But now you're all crammed together in a very small elevator,
18:35and it starts to feel much warmer because you're interchanging all this heat.
18:39It's sort of like that in the early universe. Everything is smashed together. Everything is very hot.
18:44It makes sense, theoretically, that this period was intensely hot.
18:49But how do you prove it?
18:52How do you take the temperature of the early universe, which began 13.8 billion years ago?
19:00You can't. But you can take the temperature of the coldest part of the universe now.
19:07So if you go away from all the stars and get away from all the galaxies,
19:11you might think space was infinitely cold, absolute zero. But it turns out it's not.
19:15Empty space has a temperature of roughly 455 degrees Fahrenheit below zero.
19:22Five degrees higher than absolute zero.
19:26Where did these mysterious extra five degrees come from?
19:31Big Bang believers thought they had the answer.
19:35They claimed this faint trace of heat was left over from the incredibly hot infant universe.
19:41Getting the proof took decades, but it came in 1964 by pure accident.
19:49Penzias and Wilson were Bell Labs engineers, and they were given an assignment to measure certain radio signals
19:57for the idea of sending wireless signals via telephone, so rural areas could have telephone.
20:02They used a radio antenna shaped like a giant horn.
20:06The problem was, no matter where they pointed this horn, they kept hearing kind of a static,
20:11just a radio noise coming from every direction.
20:14And they thought, okay, maybe it's a satellite, but it didn't match up with any satellite positions.
20:21There was a nearby army base, and they called up the army base and said,
20:25hey, are you broadcasting at this frequency? And they said, no, we're not.
20:29They thought, maybe it's pigeon poop.
20:31Well, you know, there are these pigeons nesting inside the antenna,
20:35and their droppings are creating this noise in your telescope.
20:39So they actually went inside and scraped out all these pigeon droppings.
20:42But no matter what they did, the noise remained.
20:45They tried everything they could to remove this background noise,
20:50and they finally realized it was coming from the sky. It was real.
20:54What they were hearing was not radio waves, but a different form of sound.
20:59Not radio waves, but a different form of radiation, microwaves,
21:05a heat signature left over from the Big Bang.
21:11They had discovered the cosmic microwave background,
21:16a ghostly snapshot of the early universe.
21:20Different colors highlight subtle variations in temperature.
21:24The cooler blue areas will develop to form stars and galaxies.
21:30The warmer orange areas will eventually make up the vastness of intergalactic space.
21:37The cosmic microwave background is a literal baby picture of our universe.
21:43It's the equivalent of a picture of you when you were seven seconds old.
21:49We can date the cosmic microwave background to 380,000 years after the Big Bang.
21:56The temperature here is estimated to be 5,000 degrees Fahrenheit.
22:02But how hot was the Big Bang?
22:06As we run the clock backwards, the universe gets smaller and the temperature increases.
22:13We know what the temperature of the cosmic microwave background was,
22:17but prior to that time, we know the universe was getting smaller and smaller and smaller,
22:21and therefore it had to get hotter and hotter and hotter.
22:25But can we find out how hot?
22:29In the early universe, it was much smaller, denser, and hotter than it is today.
22:35And in fact, it was so hot, it could fuse hydrogen into helium.
22:3925% of the mass in the early universe is fused into helium in this timescale of just a few minutes.
22:45So it's trillions and trillions of times more than the amount of fusion that's going on in the sun.
22:56Extremely high temperatures are required to fuse hydrogen into helium.
23:01Scientists estimate fusion started 100 seconds after the Big Bang.
23:06When temperatures reached 1 billion degrees Fahrenheit.
23:11During the very first fractions of the very first second of the Big Bang,
23:16some estimate the temperature could have reached 250 million trillion trillion degrees Fahrenheit.
23:24But what sparked this massive release of energy here at the birth of the Big Bang?
23:30The initial moments of our universe are a source of frustration, because it'd be really nice to know that,
23:38but also a source of curiosity.
23:41This is the frontiers of physics.
23:44This is where we're really pushing things to try to understand the fundamental aspects of reality.
23:51But even if we can back up the Big Bang story by proving the way everything in the universe works,
23:57even if we can back up the Big Bang story by proving the way everything came from a tiny hot point,
24:04there's still another problem.
24:06Where did everything that made up that tiny point come from?
24:11You can't get something from nothing, right? We all know that.
24:14Except it looks like we got everything from nothing.
24:17The entire universe seems to have appeared out of nowhere.
24:20How can that work?
24:28The Big Bang.
24:30No space.
24:32Total darkness.
24:34Nothing.
24:37Suddenly, the universe sparks into life.
24:42Really?
24:44Surely everyone knows.
24:47You can't get something from nothing.
24:51It's really the ultimate question.
24:54How did the universe come into being?
24:57We don't want just everything to come from nothing.
25:00It seems like a trick.
25:02But here we are. We exist.
25:04So something must have happened.
25:06And we just don't understand the physics of it yet.
25:09This is one of the big open questions in cosmology.
25:12The origin of the universe.
25:14And I think that people have variously said stuff like, oh, the universe has come from nothing.
25:20Like, ta-da! Now there's a universe.
25:22But remember, we don't have data about the earliest moments of the universe.
25:30We don't know what was going on.
25:34We're struggling in the dark.
25:37To get insight into what may have happened before the Big Bang,
25:41that period of apparent nothingness,
25:44physicists look to empty space.
25:47But does empty really mean there's absolutely nothing there?
25:53It's not that there's something coming from nothing,
25:56because that old-fashioned idea of nothing just doesn't apply to what we think of as empty space.
26:02It turns out, empty space is far from empty.
26:07The vacuum of space is really a writhing sea,
26:11awash with charged quantum particles and electromagnetic fields.
26:16The vacuum of space itself, it can be a very dynamic thing.
26:21Matter can spontaneously appear out of the vacuum and then spontaneously annihilate.
26:26The vacuum is full of particles and antiparticles that are whizzing into existence
26:31and then disappearing, colliding with each other.
26:34Space is full of virtual particles, popping in and out of existence.
26:39And there's no question that they're real.
26:42Their effects are absolutely visible. We can see them.
26:47In extreme physics, things can get strange.
26:51Maybe nothing is something after all.
26:57If empty space contains particles that apparently come from nothing,
27:02could some sort of similar process have triggered the Big Bang?
27:08The quantum vacuum itself can randomly, spontaneously,
27:14without any input, just have a lot of energy.
27:19Perhaps enough energy to spark something that we would call a Big Bang.
27:28There are many speculative theories about the origin of the universe.
27:33But is its sudden appearance out of nothingness the only trick it pulled off?
27:39It also made matter from energy.
27:41The universe is full of galaxies, stars, planets and comets.
27:47Where did they all come from?
27:49According to the Big Bang narrative, from one tiny dot.
27:54When the universe began, there was actually no room for matter at all.
27:58The temperature was so high, the spaces were so compressed that matter couldn't exist.
28:03So how did the universe manage to become full of matter?
28:07In the primeval atom, there was no room for matter, but it was crammed full of energy.
28:15And as Einstein tells us, all we need to create matter is energy.
28:22According to E equals mc squared, energy and matter are interchangeable.
28:30Einstein taught us, with special relativity,
28:33that energy and matter are two sides of the same coin.
28:38You can convert matter into energy by, say, blowing something up.
28:44The most fearsome example of converting matter into energy
28:48was the atomic bomb developed in the 1940s.
28:57But with the Big Bang, this process was rewritten.
29:01This process was reversed.
29:04Energy created matter.
29:08Matter that expanded out and out to fill a whole universe.
29:16And in cosmic terms, the universe, where matter would develop, grew remarkably fast.
29:23Right after the universe was born, it had an unbelievable growth spurt,
29:27basically going from being a toddler to a teenager in the single tick of a clock.
29:33How could the universe get so big so quickly?
29:38If we believe the Big Bang story, it appears to have broken one of the most fundamental laws of physics.
29:46Did the early universe really grow faster than the speed of light?
29:58The Big Bang
30:07In the classic Big Bang story, the observable universe expands from a ball of energy smaller than an atom.
30:15Today, the universe is estimated to be 93 billion light years in diameter.
30:22Think about the vast universe that we see all around us today,
30:25and it was once a tiny, tiny little volume, unimaginably dense.
30:29The universe must have gone through a colossal growth spurt.
30:35With a steady rate of expansion, there simply hasn't been enough time for the universe to grow to its current size.
30:44Regions of the universe that were close neighbors in the past are now so far apart
30:50that their separation can't be explained by normal expansion.
30:56And the huge size of the cosmos is not the only strange thing we've discovered.
31:03The universe is what astronomers call flat.
31:07Our universe is lumpy and bumpy at small scales.
31:13There's galaxies, there's black holes, there's people, there's all sorts of junk.
31:18But at large scales, global scales, truly universal scales, our universe is flat.
31:29Could this universal flatness and the super-rapid growth somehow be connected?
31:37We know that the Big Bang wasn't an explosion, or matter in the universe would be unevenly distributed.
31:46Yet something pushed everything outwards and fast.
31:52But what?
31:55In 1980, Alan Guth, a young Stanford cosmologist, came up with a potential answer.
32:01His theory of inflation says the observable universe expanded from being smaller than an atom
32:08to the size of a basketball almost instantaneously.
32:13In this tiny fraction of a second at the beginning of the universe, like a millionth of a second,
32:19but a millionth of that, a millionth of that, and a millionth of that,
32:23the universe expanded by, take the size of the universe at that time,
32:27and multiply it by a one with, say, roughly 50 zeros behind it.
32:31Inflation drove the accelerated expansion of the universe,
32:37made it get really, really big, really, really fast, and then it stopped.
32:43Inflation seems to solve two Big Bang headaches.
32:47How the universe got so huge so quickly, and why it's so flat.
32:52Because it inflated everywhere at once, all the energy in the universe,
32:57which would turn into matter, was pushed out evenly at the same time and same pace.
33:04And the four stars grow together to become the first galaxies.
33:09Even here, us, in the solar system, we're born, we're seeded,
33:15and we're the first ones to be born.
33:18In the solar system, we're born, we're seeded, in the event of inflation.
33:28Parts of the universe that are now separated by 93 billion light years
33:33once had the same cosmic zip code.
33:37To have expanded so quickly,
33:40inflation must have broken one of the fundamental rules of physics.
33:45We all know that one rule the universe sticks to all the time
33:49is that nothing can travel faster than the speed of light.
33:52So how can we possibly say that the universe expanded faster than the speed of light?
33:57But inflation says the universe expands into nothingness.
34:02There was no outside of the universe.
34:05The universe was everything.
34:08So space itself was inflating.
34:11And space can move as fast as it wants.
34:15You can't go faster than the speed of light through space.
34:19But space itself is allowed to stretch and expand as fast as it wants.
34:23And that's what our universe is doing.
34:26The idea of inflation smooths out the universe in kind of a peculiar way.
34:30You can kind of think of it as having a sheet with a lot of wrinkles in it.
34:34And if you take that sheet and snap it really hard, those wrinkles very suddenly flatten out.
34:38The theory of inflation is one of the craziest sounding ideas in the history of science.
34:46So crazy that it might just be right.
34:49Inflation helps us to understand the inexplicable.
34:53But there's a problem.
34:55We don't know what triggered or powered inflation.
35:00The inflationary universe idea imagines that the universe was suffused with some kind of ultra-dense energy at early times.
35:08Something that pushed the universe apart.
35:11What caused there to be that hot, expanding stuff?
35:15We have to be humble and acknowledge that we don't know for sure.
35:20But whatever started it, inflation was over in a split second.
35:25It didn't last very long.
35:27And this is difficult to understand.
35:30How did inflation stop?
35:34We don't know.
35:36We got none, folks.
35:38Well, we got some things, but it's tough.
35:41It's tough.
35:44But has the process of inflation really stopped?
35:47One radical theory proposes if the force called inflation kick-started the expansion of one universe,
35:55then why not another?
35:57And another?
35:59And another?
36:02Is inflation creating a whole series of new universes?
36:07Is there a multiverse?
36:18If we believe the Big Bang story,
36:21a dot smaller than an atom expanded to make a universe 93 billion light years across.
36:29A theory called cosmic inflation claims to explain this stupendous growth.
36:41But inflation may create more questions than answers.
36:45Inflation gave us more than we had bargained for.
36:48We tried to come up with a mechanism that would just create our universe and stop.
36:53And then quickly realized that actually just like most car factories don't produce one car and then stop,
36:58but produce many cars.
37:00Inflation tends to produce one universe and another and a vast number of them.
37:05A multiverse.
37:07It's a process called eternal inflation.
37:10It proposes that while inflation ended in our universe and led to formation of stars and galaxies,
37:16we're just one small part of a vast, continuously inflating multiverse.
37:23Imagine a series of bubbles next to each other.
37:28Those are the different universes.
37:30And so our bubble is expanding.
37:32And we're bumping into our neighboring universe and we're going to expand into it.
37:36If the multiverse theory is correct.
37:40A big bubbling multiverse sounds like science fiction.
37:45But there is prospective evidence to back up the theory.
37:49Scientists have spotted an unusual mark on the cosmic microwave background.
37:56That snapshot of the infant universe.
38:00There's a spot on the cosmic microwave background
38:05There's a spot in the southern hemisphere that's not necessarily the coldest spot or the biggest spot,
38:14but it's the coldest, biggest spot.
38:17And it's strange.
38:20We don't know how to fully explain it.
38:23One unproven but intriguing theory is that this area is a kind of cosmic dent.
38:30Surface damage from an impact with another universe.
38:34I work in the building with the people that discovered this giant cold area.
38:39And they were pointing it out and saying, well, that doesn't make any sense.
38:42Why would the microwave background be like that?
38:44Hey, maybe that's evidence of another universe interacting with our own.
38:48That's something that when you go to lunch makes you pause.
38:53If you buy into the idea of a crowded multiverse,
38:57cosmic bangs and scrapes are not only perfectly possible, they're probable.
39:03There may be many universes outside expanding under the force of inflation right now.
39:08One analogy is think about a superhero that just can't be killed.
39:12They keep regenerating.
39:15If the multiverse narrative is correct,
39:18it places a giant question mark over the story of the Big Bang.
39:23The possibility of a multiverse suggests not just one, but a whole series of Big Bangs.
39:32But not all physicists buy into this thesis.
39:37The community is divided on the idea of the multiverse, predictably,
39:41because there are some of us who believe that this sort of this leap of imagination is justified.
39:47And there are others, sort of hardliners, who think that till we have empirical evidence,
39:52this is not a scientific idea.
39:54Others welcome the fact that when it comes to explaining everything,
39:58we're not simply stuck with the good old Big Bang narrative.
40:03I would have felt kind of claustrophobic if it turned out that all that existed was Earth.
40:09And I was happy that we discovered there was part of something bigger,
40:12the solar system, the galaxy, a cluster of galaxies or a universe.
40:16So I'd feel even better if there's still more space out there and parallel universes.
40:22The more the merrier.
40:23While it's an appealing notion, without empirical evidence,
40:27it's a theory requiring a leap of faith.
40:32There's no reason to think that the tiny little creatures that we are
40:36actually perceive the vast true nature of reality.
40:40This is still an absolute puzzle.
40:43We have ideas, I have ideas, other people have proposed models, right?
40:47But we have no data, really, that helps us distinguish between these ideas.
40:50And to be honest, the ideas themselves aren't fully fleshed out.
40:55Support for the classic Big Bang model seems to be increasingly shaky.
41:00The latest thinking proposes not one, but a whole series of Big Bangs.
41:08As scientists continue to rewrite the traditional story,
41:12more and more questions are being asked.
41:15But for now, many remain.
41:17Unanswered.
41:19What was the origin?
41:21Is there even a sense to asking was there a time before time?
41:25And I think the answer is yes.
41:27You know, our science and our math, they're just incomplete.
41:30Someday we may have the mathematics to describe the earliest moments of the universe.
41:35Someday we may be able to make predictions that we can connect to observations.
41:40Just because that day isn't today, doesn't mean that that day will never come.
41:44We've learned an enormous amount in the last hundred years,
41:47but now we're left with some pretty serious puzzles that are going to be really tough to solve.
41:53So I'm waiting for the next Einstein.