New discoveries are helping experts map the entire universe, and they are finding strange truths about the cosmos and its unimaginable size.
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LearningTranscript
00:02The most ambitious map in history is taking shape before our eyes.
00:11And scientists are heading for the edge.
00:18It may be the strangest map you'll ever see.
00:22And it's bigger than you can believe.
00:27It's a map of the entire universe.
00:33There's this whole pattern to the universe that we're starting to map out.
00:37Seeing it really brought home the way the universe actually behaved in a way that all the numbers and equations
00:43never quite could.
00:45What if the universe is so big we never find the edge?
01:09Anthony Aguirre from the University of California in Santa Cruz is a theoretical cosmologist.
01:18So he's used to thinking big.
01:20Now to say that we're going to go out and make a map of the universe, it almost sounds crazy.
01:25It sounds like real hubris, right? We're going to go map the universe.
01:30And yet the universe, as it turns out, is really amenable to mapping.
01:37But you have to think big.
01:39And that's where the balloons come in.
01:45Because the map of the universe isn't like other maps.
01:49We have to think in a different way.
01:51We can't just go out and look at the universe and draw things on paper and say,
01:55there's our map of the universe.
01:57The universe is so big that the laws of physics say we can't see all of it.
02:06It's as if we're at the center of a giant balloon and we can't see out.
02:13We can only see light and light moves at a certain speed.
02:16And so as we look farther and farther away, we're looking at farther and farther back in time.
02:23Because we're seeing light coming to us from long ago.
02:27But there's only so far we can go back in time.
02:32So there's only so far we can see.
02:38It's called the observable universe.
02:42We can only map what's inside because the universe is only 13.7 billion years old.
02:50There may be a lot more universe outside, but the light hasn't had time to reach us yet.
02:59But cosmologists have still made a map on an unbelievable scale.
03:07The Milky Way could fit inside 10 million, million, million times.
03:17Our entire galaxy is just a dot on the landscape.
03:25In the observable universe, there are 170 billion galaxies just like it.
03:33Jan Eleven is a professor of theoretical astrophysics.
03:40She'd like to put every single galaxy we can see on the map.
03:45But before she can do that, it's vital to account for one of the most surprising features of the universe.
03:55Making a map of the whole universe is not like making a map of the United States.
04:00It's an observational fact that if you look at the galaxies around us,
04:05and the most distant galaxies that we can see, they all appear to be moving away from us.
04:09And the further away they are, the faster they're moving away from us.
04:13The galaxies aren't like landmarks on normal maps.
04:18They don't stand still.
04:21Everywhere we look, the most distant galaxies are moving away from us.
04:28This is a strange universe, and the explanation is even stranger.
04:35People want to imagine a central point with everything exploding out from that point, moving away, only from that one
04:42central location.
04:43And that's really the wrong picture here.
04:46That makes it sound like we're in a special place, like somehow we're at the center and everything's moving away
04:51from us.
04:52But actually it's not like that.
04:55There's nothing special about our place in the universe.
05:00If we went to another galaxy, we'd see exactly the same thing.
05:05If you went to a distant galaxy, they would have the same perspective.
05:09They would look at all the galaxies around them and see that they were moving away.
05:13You really have to try to imagine that every single point is moving away from every other point, so no
05:18point is special.
05:20No matter where you're standing in the universe, if you look out, you will see galaxies moving away from you.
05:28Think of it like cities on a map.
05:32If you were standing in California, you would see New York moving away from you.
05:37But from the perspective of New York, you would see Boston move away.
05:42And if you were standing in Chicago, you would see New York and California moving away from you.
05:47So no matter where you're standing, you see everything else moving away from you.
05:52In the observable universe, the galaxies are doing exactly the same thing.
06:00The only explanation for that is that the space itself is stretching, that the universe itself is getting bigger.
06:07Not that the galaxies are moving on the space, but that the space is getting bigger.
06:13It's as if the whole country was getting bigger and bigger every day.
06:19So you would think it would be impossible to keep the map up to date.
06:30For cosmologists, the expansion of the universe is not a problem.
06:35In fact, it's a gift.
06:38If space is stretching, then the wavelength of light from the galaxies is stretching too.
06:45The greater the distance, the lighter the light.
06:50This redshift effect is the mapmaker's vital tool for measuring distance.
06:59And redshift was the key to the next vital stage in mapping the universe.
07:06A survey to pinpoint the exact location of galaxies stretching five and a half billion light years from Earth.
07:31Cloudcroft, New Mexico.
07:38David Schlegel is a cosmologist from the University of California at Berkeley.
07:44When he first came to town, the map of the universe was almost empty.
07:50What we wanted to do was something much more ambitious and actually get a map of the million brightest galaxies
07:56on the sky.
07:58The task required measuring the distance, and therefore the redshift, for every single one of these galaxies.
08:06Obviously, you need to look at more than one galaxy at a time, so that's the trick.
08:11And if you were a futurist, you'd say, well, it's the 1990s, we have computers and we have robots.
08:19The folks designing the Sloan, though, decided to take the pragmatic approach and say, well, we actually want this thing
08:25to work.
08:29Instead of robots, the ingenious system they came up with required a far more human touch.
08:39And they would have to go around the universe twice.
08:47It's really doing two maps of the sky.
08:52The first time around, they didn't measure any red shifts.
08:56The telescope simply took photographs.
09:00A map of the sky, but in two dimensions only.
09:05It doesn't give the distance to each galaxy yet.
09:10We actually have, from those images, not very much idea of where these things are in three-dimensional space.
09:17So, at some level, it's just a pretty picture.
09:20But the next stage was the trick.
09:24They printed the images in metal.
09:29Each of these holes corresponds to our two-dimensional location of a galaxy on the sky.
09:34Where if I look at this hole, we have the longitude in this coordinate, the latitude in this coordinate.
09:41And so, the whole design of this system is to, as efficiently as possible, get the light from that one
09:48galaxy into that specific hole.
09:52The plug-in team from town connected every galaxy with a fiber-optic cable.
09:58Then put the plate back over the telescope.
10:04The second time around, the telescope measures the red shifts for these specific galaxies alone.
10:14One thousand galaxies on a plate.
10:17Nine plates a night.
10:20And one million galaxies in total on a map crafted by human hands.
10:29The Sloan survey is one of the great achievements of precision cosmology.
10:39Redshift measures the distance, the third and final coordinate for every galaxy to make a 3D movie on a colossal
10:47scale.
10:54Maybe you've seen things like this in the opening of Star Trek or Star Wars or whatever, and that all
11:00looks great.
11:00But it's not real.
11:02This movie, it is the real universe.
11:07Every point of light on the map is a galaxy like the Milky Way.
11:15Cosmologists can now see at a glance how the galaxies are arranged in space.
11:24What these maps let us do is it really allows us to test all the forces of nature that we
11:31know about.
11:33There is structure really on all scales.
11:36The galaxies are not just placed at random, they're bound together by gravity in a vast cosmic web.
11:47This goes on and on, and in fact, up to the larger scales that we can see, you can still
11:53trace these structures of galaxies.
11:56But the most surprising discovery is what can't be seen.
12:02Most of the universe is missing.
12:08Most of the universe can be seen in the dark.
12:09The most surprising people are seeing as planets and planets.
12:15It's not the complete world.
12:17It's not the most surprising people, it's not the most surprising people, but we know that the world is not
12:18the most surprising people.
12:21Modern cosmology needs a new kind of map.
12:31Because most of the universe is hiding in the dark.
12:40We don't know what dark matter is, because it's never been detected on Earth.
12:47We know it must be out there, because its gravity is holding the cosmic web of galaxies together.
12:55But we can't see it, because it doesn't give off light.
13:01Someone has to find it, and put it on the map.
13:10British astronomer Richard Massey is a master of the invisible.
13:21He's a member of a team hunting for dark matter based at the California Institute of Technology.
13:28So he frequently flies to Los Angeles.
13:34When you're flying over America at night, you see these crisscrossing lanes of streetlights spread out across the continent.
13:45There's obviously some interesting stories going on down there, in between these roads.
13:54In fact, most of the story of what's going on in America is actually happening in those empty spaces that
14:00you can't see.
14:01Richard's task is like mapping those apparently empty spaces.
14:07It's as if whole cities were hiding in the dark.
14:15It takes imagination to find your way in a dark universe.
14:21You have to dream up new ways to detect what can't be seen.
14:28One possibility is that if dark matter doesn't give off light, maybe it absorbs light.
14:38Ordinary matter, the stuff that we're made out of, casts a shadow because it absorbs light.
14:46So we can see the ordinary matter in silhouette.
14:51Unfortunately, dark matter doesn't give itself away that easily.
14:57Light just goes straight through it.
15:01The secret to mapping dark matter that you can't see is to look at the light that you can see.
15:09Everything that has mass, including dark matter, actually bends the fabric of space and time that we live in.
15:16And if space is warped, then everything in it is distorted, even the paths of light rays.
15:25The only way that dark matter might reveal itself is through gravity.
15:31According to Einstein's theory of relativity, all matter distorts space, causing light to change direction.
15:40The idea of general relativity bending space and time and deflecting rays of light sounds really complicated.
15:45But actually, you see light rays bending all the time.
15:49When you look into a swimming pool and see that your legs aren't in the right shape,
15:52you know that there must be some water in the way.
15:56The distortion of the light depends on water ripples in the pool,
16:01which in turn depend on where the swimmers are at any one moment.
16:09The survey team went looking for dark matter in exactly the same way,
16:16with a thousand hours of observations on the Hubble Space Telescope.
16:23By looking at distant galaxies halfway across the universe,
16:25by looking at their shapes and the distorted images that we see of those,
16:29we can work out what ripples there are in space between them and us.
16:33And those ripples in space are caused by the dark matter.
16:43The search zone was a thin column of the universe, stretching eight billion light years from Earth.
16:51The team was on the lookout for distortions in the most distant galaxies.
16:57Whenever you see galaxies distorted into these strange, uncharacteristic shapes,
17:02you know that there must be something in between them and you,
17:05something really massive, and even if it's invisible,
17:08you can still map out where it is by the way that it warps that space-time.
17:14The mapping technique revealed a ghostly hidden universe.
17:19The light from visible galaxies was recast in new and beautiful forms.
17:26They've become these full rings, distorted, what are known as Einstein rings,
17:31whenever there's a big lump of dark matter in front of them.
17:35The lumps become contours on a map of the invisible.
17:41They reveal dark matter as the hidden iceberg beneath the surface of the cosmic ocean.
17:49What we're finding out there in the universe is really weird.
17:53It's equivalent to the idea that only one out of six cities in America actually has any people living in
17:58it.
17:58The other five, six of the population are these invisible ghosts that we just can't see.
18:04The survey has transformed the map of the universe.
18:12It suggests that normal visible matter is just a fraction of what's out there.
18:19In the search zone, dark matter outweighs it by six to one.
18:25This is the stuff the universe is really made of.
18:48For cosmologists, the road ahead has become a lot less certain.
18:54Right now, we know the universe is expanding.
18:58But given enough dark matter, it could have a different and very dark future.
19:06It's sensible to conclude, when we look at how that stuff affects the shape of space,
19:11that the universe should be expanding, but that it should be slowing down.
19:16Dark matter puts a very heavy foot on the brakes.
19:21Because the more matter there is, the more gravity there is.
19:30Gravity attracts, and so the cosmic expansion should be slowed down by all that attraction.
19:39If there's enough dark matter, the universe will eventually stop expanding altogether,
19:45and go into reverse.
19:50Gravity will bring everything back together in a final cataclysmic big crunch.
20:02The question is, when?
20:08The search for the answer began here on the Berkeley campus of the University of California.
20:18It's a distinctive outpost in the landscape of science,
20:24signposted with some of its greatest names.
20:31There's even a parking lot reserved for Nobel laureates.
20:37Nine prize winners in a row, with five in physics alone.
20:45And it was here in 1988, that Saul Perlmutter set out to map the deceleration of the universe.
20:59The key was measuring how fast the universe was expanding in the past, compared to now.
21:05They planned to map ancient galaxies, 10.8 billion light years from Earth.
21:12But it would take a whole decade to find and analyze what they were looking for.
21:20A candle.
21:23If you want to measure distances across the universe,
21:26you would like to be able to use an object that's of known brightness.
21:31We call anything that we know the brightness of, a standard candle.
21:37A standard candle always has the same brightness, so you can use it to measure distance very precisely.
21:44The further away it is, the dimmer it will appear in our telescopes.
21:49But candles are elusive objects.
21:53We hunt for what astronomical object could you possibly use that will behave in this very regular way,
22:00so that you can actually compare the distances.
22:03Saul had a very bright idea.
22:09He would find his way by the light of a dying star.
22:14A supernova.
22:18When one of these supernova explodes, that one star can be as bright as the entire galaxy of a hundred
22:25billion other stars.
22:29So this is a remarkably bright single event.
22:35Saul had a special kind of supernova in mind.
22:41A Type 1A is triggered when a dying star draws in mass from its neighbor.
22:51Just at the point where there's a critical mass, there will be a runway thermonuclear explosion.
23:01So that means that it's triggered at the same mass every time.
23:05The same mass every time means the same brightness every time.
23:12They're perfect standard candles.
23:15But Saul had to find them first.
23:20They're just a real pain in the neck to work with.
23:26They're rare, they're random, and they're rapid.
23:30A supernova only burns brightly for three weeks.
23:34And in any given galaxy, they explode, without warning, roughly once every 300 years.
23:42With those odds, you can't book valuable time on the world's best telescopes.
23:49It makes a terrible proposal if you say that sometime in the next several hundred years,
23:54a Type 1A supernova might explode somewhere in this galaxy.
23:57I would like the night of March the 3rd, just in case.
24:02But Saul had a plan to get the odds working in his favor.
24:07With billions of galaxies in the observable universe, there are dozens of supernovae every night.
24:17Saul's team spent six years perfecting a new system for supernovae on demand.
24:25They took snapshots of thousands of galaxies at once, then repeated them two and a half weeks later.
24:33First, you don't see a supernova.
24:38Now you do.
24:41That's very important, that two and a half weeks, because that guarantees that everything you find that's brighter on the
24:46second night than the first is on the way up.
24:49We can now guarantee that there would not just be one Type 1A supernova, but that there would be a
24:54half dozen.
25:00Saul now knew exactly where to point one of the world's most powerful telescopes, the Keck Observatory in Hawaii.
25:11He was finally ready to measure the deceleration of the universe.
25:17But by late in 1997, the team was getting some very weird results.
25:27The supernovae distance measurements didn't match the predicted deceleration.
25:34The more we checked, the more we fine-tuned every little step of the calibration,
25:40the more the weird result didn't go away.
25:43The weird result has reverberated through the world of science ever since.
25:49In January 2012, Saul Perlmutter won the Nobel Prize for Physics and won a parking space for life.
26:00At the end, we concluded that actually, the universe really isn't slowing down.
26:05It's actually speeding up in its expansion.
26:07And that was a big shock.
26:12It's been described as one of the biggest shocks in modern cosmology.
26:22Welcome to a very new picture of the universe.
26:29But even the experts can hardly believe it's real.
26:35The most famous force in physics has met its match.
26:40Because the entire universe is defying gravity.
26:47What's doing the pushing? What's that force that's forcing everything apart?
26:51Well, we don't know, but we did work out what to call it.
26:54We have a name for it. We call it dark energy.
26:58Cosmologists don't know what dark energy is.
27:02They only know what it does.
27:06Where gravity pulls, dark energy pushes.
27:18There's dark energy in the galaxy. There's dark energy here on Earth.
27:22There's dark energy passing through us right now.
27:24We're filled with this dark energy.
27:26We don't see it. We don't feel it.
27:28But it's everywhere. It's kind of just a uniform coloration to our map.
27:3373% of the universe is dark energy.
27:36But you'd never know.
27:39In everyday life, this stuff is just hard to detect.
27:43It's only when you get to really large scales that you really see the effect of this stuff.
27:50In the really big scheme of things, dark matter is fighting a losing battle.
27:56Because there's only so much of it to go around.
28:03If you add more space, if you give more place for those little pieces of matter to be, then the
28:09density of them goes down.
28:11If you just see less of it, it gets diluted.
28:14As the universe expands, dark matter thins out until it can no longer compete with dark energy.
28:22The really crucial thing about how this dark energy behaves is that it doesn't dilute.
28:28When the universe doubles in size, you've got twice as much dark energy.
28:32Make it four times as big, you've just got four times as much dark energy.
28:36Once you get to this cosmological scale, the biggest possible scale, it becomes the biggest game in town.
28:42It becomes the prime player.
28:45Dark energy is on the map.
28:49But cosmologists can't explain it.
29:02The entire observable universe is saturated in dark energy.
29:09But there's one final set of clues to be found on its furthest edge.
29:15And it may contain the secrets to the universe beyond.
29:42We're heading off the map into impossible territory.
29:50The edge of the observable universe is the furthest horizon our telescopes can see.
29:57But for cosmologists like Sean Carroll, that's not enough.
30:02He wants to know the size of the whole universe.
30:06I definitely think it's okay to think about parts of the universe that we can't observe and can never observe.
30:13We've done a very good job at understanding what the universe looks like in that visible portion.
30:19So now when our imaginations roam, they often sneak outside the visible portion to ask what might the universe look
30:24like beyond our visible horizon.
30:27The universe that we can't see, that's the playground for theorists now.
30:34But if we can't see the rest of the universe, how can we figure out how big it is?
30:40For Gen 11, it's a similar task to working out the shape and size of the Earth.
30:46But there's a catch.
30:48We know we could step far from the Earth as an astronaut has.
30:53We can look down on it and see from the outside that it was a sphere and it was curved.
31:00You can't step outside of the universe. You have to do everything from inside of space.
31:06Without leaving the Earth, how do you know it's round and therefore has finite size?
31:13It could be completely flat and stretched to infinity in all directions.
31:19One way is to use simple math.
31:27All you have to do is draw a triangle.
31:37If you're drawing a small enough triangle on the beach, you won't notice the curvature of the Earth.
31:43It'll look like a normal triangle.
31:45You'll be able to draw the lines pretty straight and the interior angles will look like they add up to
31:50180 degrees.
31:51It'll look like the triangle you draw on a flat sheet of paper.
31:54But this isn't a normal triangle because the Earth's surface is curved.
32:01It's just so subtle that the sides of the triangle still look straight.
32:07It would probably be a challenge on the beach to draw it big enough that you would be able to
32:11notice the curvature of the Earth.
32:14The key is to make the curvature more obvious by drawing the biggest triangle you can.
32:22If I draw a triangle big enough that it comes from the North Pole and it wraps all the way
32:28around North America,
32:29now it's very obvious that those angles are bigger than 180 degrees and that the sides of the triangle are
32:37not straight lines.
32:41So we can show the Earth is curved and therefore has finite size without leaving it.
32:48And we can find out the shape and size of the universe in exactly the same way by looking for
32:56triangles of light.
33:01Light will travel in a straight line if the space is flat and light itself will travel on an arc
33:07if the space is curved.
33:08These curves are going to be so subtle, more subtle than the curvature of the Earth.
33:14We really have to look back as far as we possibly can and that means the oldest relic we have
33:20in the universe.
33:21So that means looking at things like the light left over from the Big Bang.
33:35The early universe was a hot, dense fireball.
33:40When it cooled, a pattern of light emerged at what is now the edge of the observable universe.
33:47This is the cosmic microwave background.
33:55The CMB was discovered in the 1960s.
33:59But throughout his career, Sean Carroll has been able to explore it in greater and greater detail.
34:07Waiting for triangles to emerge.
34:14It takes good technology to do it.
34:17You need better and better receivers.
34:19Less and less noise in your detector.
34:21And ultimately you need satellites to get a really good 360 degree view of the whole cosmic microwave background.
34:33It was NASA's WMAP mission in 2003 that brought the most vital contours into sharp focus.
34:44WMAP for the first time had that resolution.
34:47So when WMAP came out, we could really use those features to make a big triangle and measure the geometry
34:53of space.
34:56Continents begin to appear, smaller islands, you get a finer resolution of the coastlines and so forth.
35:02The islands are miniscule temperature variations in the early universe.
35:07Less than 100,000 of a degree.
35:14A distinctive feature for making triangles.
35:27These splotches we see in the microwave background appear at all different sizes.
35:32But there is a best size for them to be.
35:35There's a size at which the fluctuations are the strongest.
35:39We know how big they are.
35:41We know how far away they are.
35:43So between us and the size of a feature in the CMB, we can measure a triangle and use that
35:49to infer the geometry of space.
35:53The Earth, plus the opposite sides of the island, form the three points of a very long, thin triangle.
36:03The key to measuring whether the universe is flat or curved.
36:08If the universe were positively curved, if the angles inside the triangle added up to greater than 180 degrees, then
36:16it would be finite in size.
36:18If the spatial geometry is flat, if the angles inside the triangle add up to 180, then it could go
36:25on forever.
36:29The result is one of the greatest triumphs of modern cosmology.
36:35A miracle of precision map making that measures the angles of the triangle to the third decimal place.
36:44And it says that the universe is infinite.
36:48The answer is that Euclid was right.
36:51Space seems to us to be flat as far as we can measure.
36:54It will never cease to amaze me.
36:57We human beings here on this tiny little rock are able to reach out with our instruments and our brains
37:03to understand the whole shebang.
37:08And if an infinite universe isn't big enough for you, it's still growing.
37:16All the distances are getting bigger every day, so it's still infinite, all the same galaxies are there, it's just
37:22that we've now pumped more space between every point in this infinite universe.
37:27That's really mind-boggling.
37:32But even this isn't the end of the story.
37:57But even this isn't the end of the story.
38:02Because Anthony Aguirre thinks our universe may not be alone.
38:13Sometimes when I'm headed down the highway and I'm driving, you know, my wife will say, Anthony, you're going 40
38:21on the highway.
38:21And then she knows that I'm thinking about other universes.
38:27He thinks that there may be other universes because of the process that created our own.
38:33It's called inflation.
38:36It describes an exponential expansion in the moments after the Big Bang.
38:43At a speed the universe would never repeat again.
38:47Inflation has been a very successful theory in predicting the observed properties of our universe and how our observed universe
38:55came into being.
38:59Inflation may have started out as a mathematical theory.
39:05But it has gained acceptance after successful testing against the evidence from the cosmic microwave background.
39:14I was amazed when I saw the results come in from those satellites that reproduced all the bumps and wiggles
39:22and all the detailed properties of that microwave background that inflation had predicted.
39:27Inflation explains how the observable universe developed.
39:33It was doubling its size over and over and over again in a tiny fraction of a second.
39:37Going from something like a billionth of the size of a proton to something maybe the size of a bubble.
39:43So-called.
39:48But inflation didn't stop with our own universe.
39:52Anthony believes it may have happened over and over again.
39:59This is really a side effect.
40:01It's a huge side effect.
40:03It's an amazing side effect.
40:04But it's a side effect of something we invented already for a different purpose.
40:11It's a process called eternal inflation.
40:20There could be as many as we could imagine.
40:27Anthony's vision of an infinite number of infinite universes may sound far-fetched.
40:34But the search is on to find evidence to support it.
40:40Evidence from the oldest part of our map.
40:47Every once in a while we could have sort of a cosmic collision with another bubble.
40:55It would leave an impact, it would leave a bruise, a disk in the sky on the microwave background radiation
41:03that we could look for.
41:09Anthony and his colleagues have simulated what a collision of universes would look like.
41:15A dark bruise superimposed on the cosmic microwave background.
41:21He doesn't yet have enough data to test it.
41:25But it's a tantalizing glimpse of what the map could reveal with the next generation of satellites.
41:34In principle, I think this scenario with all these bubbles is testable.
41:39We can actually go out and look for them.
41:42This may be the ultimate map of the universe.
41:50We're talking about understanding and testing and theorizing in a scientific way about an infinite number of universes.
42:00It's simultaneously so mind-boggling and yet it's still rigorous science.
42:05We can do mathematics, we can do experiments, we can really test it.
42:16Some day we'll understand the universe so well that we can literally take that map, put it on a little
42:20compact disc and put it in our pockets and take it home.
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