0:00:02 > 0:00:05The most ambitious map in history
0:00:05 > 0:00:07is taking shape before our eyes.
0:00:11 > 0:00:14And scientists are heading for the edge.
0:00:18 > 0:00:21It may be the strangest map you'll ever see.
0:00:22 > 0:00:26And it's bigger than you can believe.
0:00:26 > 0:00:31It's a map of the entire universe.
0:00:32 > 0:00:37There's this whole pattern to the universe we're starting to map out.
0:00:37 > 0:00:40Seeing it really brought home the way the universe actually behaved,
0:00:40 > 0:00:44in a way that all the numbers and equations never quite could.
0:00:46 > 0:00:50Cosmologists are making sense of startling discoveries.
0:00:51 > 0:00:55Medieval maps would say, "Here be monsters."
0:00:55 > 0:00:57They weren't entirely wrong.
0:00:58 > 0:01:01They're even building pictures of the invisible.
0:01:03 > 0:01:06How do you map something that you can't even see?
0:01:08 > 0:01:11Our brains build maps even where our telescopes cannot reach.
0:01:13 > 0:01:16This is a map of everything we know.
0:01:18 > 0:01:21And it's getting bigger every day.
0:01:23 > 0:01:26It kind of hits you, how magnificent it is.
0:01:26 > 0:01:29It's bigger than we can actually really even imagine.
0:01:31 > 0:01:33The universe is so big,
0:01:33 > 0:01:35we may never find the edge.
0:01:49 > 0:01:53Mapping the universe is a job for pioneers.
0:02:02 > 0:02:07Nick Risinger is blazing a trail through the American south west.
0:02:12 > 0:02:14You have to be pretty persistent.
0:02:14 > 0:02:16No stopping.
0:02:16 > 0:02:18You've got to keep going.
0:02:19 > 0:02:23Nick wants to put our entire galaxy on the map.
0:02:26 > 0:02:30He's on a single-handed mission, to photograph the Milky Way.
0:02:32 > 0:02:35New Mexico is a great place to take photos.
0:02:35 > 0:02:38It's dry, it's high,
0:02:38 > 0:02:41and there's not a whole lot of city around here.
0:02:41 > 0:02:43There's a break in the weather,
0:02:43 > 0:02:46and you get a full, almost a full night in.
0:02:46 > 0:02:49Other times, you only get, you know, 10% of the night.
0:02:49 > 0:02:51But it's all luck of the draw.
0:02:53 > 0:02:56It's looking pretty good over there, actually.
0:03:03 > 0:03:05In the modern world,
0:03:05 > 0:03:08few of us have skies dark enough to see the Milky Way.
0:03:11 > 0:03:14But Nick plans to show us our home galaxy
0:03:14 > 0:03:17like we've never seen it before.
0:03:19 > 0:03:23I'm trying to give people that broad, big-picture understanding
0:03:23 > 0:03:27of the entire night sky, and where they fit into that.
0:03:28 > 0:03:32Our galaxy has nearly half a trillion stars.
0:03:35 > 0:03:38Most of them are too dim and distant to see.
0:03:41 > 0:03:42But Nick's cameras
0:03:42 > 0:03:47are more than 2,000 times more sensitive than the naked eye.
0:03:47 > 0:03:50If I had known how much work it would be going into it,
0:03:50 > 0:03:53I probably wouldn't have even started.
0:03:53 > 0:03:57But my personality is, once you start something, you finish it.
0:04:00 > 0:04:04After two years, he's photographed 20 million stars...
0:04:09 > 0:04:13..by stitching together more than 37,000 separate images.
0:04:18 > 0:04:20Some people might be driven crazy
0:04:20 > 0:04:22by hearing shutters clack all night long.
0:04:22 > 0:04:27But it's actually music to my ears, because it means they're working.
0:04:28 > 0:04:31By combining data from six different cameras, he's captured
0:04:31 > 0:04:35something that would tax even the world's most powerful telescopes.
0:04:38 > 0:04:43His final image is the highest definition, true colour map
0:04:43 > 0:04:44ever made of the Milky Way.
0:04:50 > 0:04:52But he hasn't just mapped it...
0:04:55 > 0:04:58..he's made a hand-held guide to the galaxy.
0:05:10 > 0:05:13This is like a window to the sky.
0:05:13 > 0:05:15And you can point it in any direction
0:05:15 > 0:05:18and be shown exactly what you're looking at.
0:05:24 > 0:05:27So here, we're looking at the centre of our galaxy.
0:05:27 > 0:05:28This is our Milky Way.
0:05:28 > 0:05:32You can see this bright cluster of many small stars.
0:05:35 > 0:05:39The map reveals more features with every level of detail.
0:05:44 > 0:05:48As we zoom in here to the centre of the galaxy,
0:05:48 > 0:05:50I'll point out this dark patch here, this is the Pipe Nebula,
0:05:50 > 0:05:55and it's one of my favourite landmarks to help me orient myself.
0:05:59 > 0:06:03But it's the sheer size of the image that reveals its true ambition.
0:06:13 > 0:06:17From one side to the other, it's 100,000 light years.
0:06:25 > 0:06:30This image is such a big subject, and it makes you feel so small.
0:06:30 > 0:06:32100,000 light years!
0:06:33 > 0:06:38It boggles the mind just trying to comprehend just how vast that is.
0:06:42 > 0:06:46But the fact is, the map of the universe has barely begun.
0:06:59 > 0:07:03Anthony Aguirre, from the University of California in Santa Cruz,
0:07:03 > 0:07:06is a theoretical cosmologist.
0:07:07 > 0:07:10So he's used to thinking big.
0:07:10 > 0:07:13Now to say that we're going to go out and make a map of the universe,
0:07:13 > 0:07:17it almost sounds crazy. It sounds like real hubris, right?
0:07:17 > 0:07:19"We're going to go and map the universe!"
0:07:19 > 0:07:24And yet the universe, as it turns out, is really amenable to mapping.
0:07:26 > 0:07:29But you have to think big, and clever.
0:07:29 > 0:07:32And that's where the balloons come in.
0:07:33 > 0:07:38Because the map of the universe isn't like other maps.
0:07:38 > 0:07:40We have to think in a different way,
0:07:40 > 0:07:44we can't just go out and look at the universe and draw things on paper
0:07:44 > 0:07:46and say, "There's our map of the universe."
0:07:46 > 0:07:48The universe is so big
0:07:48 > 0:07:52that the laws of physics say we can't see all of it.
0:07:55 > 0:08:00It's as if we're at the centre of a giant balloon, and we can't see out.
0:08:02 > 0:08:06We can only see light. And light moves at a certain speed.
0:08:06 > 0:08:10And so, as we look farther and farther away,
0:08:10 > 0:08:12we're looking farther and farther back in time
0:08:12 > 0:08:16because we're seeing light coming to us from long ago.
0:08:16 > 0:08:21But there's only so far we can go back in time.
0:08:21 > 0:08:24So there's only so far we can see.
0:08:28 > 0:08:31It's called the "observable universe".
0:08:31 > 0:08:33We can only map what's inside,
0:08:33 > 0:08:38because the universe is only 13.7 billion years old.
0:08:39 > 0:08:42There may well be a lot more universe outside,
0:08:42 > 0:08:45but the light hasn't had time to reach us yet.
0:08:48 > 0:08:52In the last 20 years, we've seen this tremendous expansion,
0:08:52 > 0:08:55both in the amount and in the precision of knowledge that we have
0:08:55 > 0:08:57about the observable universe.
0:09:00 > 0:09:05This has allowed cosmologists to make a map of unbelievable scale.
0:09:08 > 0:09:16The Milky Way could fit inside 10 million million million times.
0:09:19 > 0:09:22Our entire galaxy's just a dot on the landscape.
0:09:25 > 0:09:27In the observable universe,
0:09:27 > 0:09:31there are 170 billion galaxies just like it.
0:09:34 > 0:09:38Janna Levin is a professor of theoretical astrophysics.
0:09:40 > 0:09:45She'd like to put every single galaxy we can see on the map.
0:09:45 > 0:09:48But, before she can do that, it's vital to account for
0:09:48 > 0:09:52one of the most surprising features of the universe.
0:09:55 > 0:09:57Making a map of the whole universe
0:09:57 > 0:10:00is not like mapping a map of the United States.
0:10:00 > 0:10:05It's an observational fact that, if you look at the galaxies around us,
0:10:05 > 0:10:08and the most distant galaxies that we can see,
0:10:08 > 0:10:10they all appear to be moving away from us.
0:10:10 > 0:10:13And, the further away they are, the faster they're moving away from us.
0:10:14 > 0:10:18The galaxies aren't like landmarks on normal maps.
0:10:19 > 0:10:21They don't stand still.
0:10:23 > 0:10:27Everywhere we look, the most distant galaxies are moving away from us.
0:10:29 > 0:10:32This a strange universe,
0:10:32 > 0:10:34and the explanation is even stranger.
0:10:36 > 0:10:38People want to imagine a central point
0:10:38 > 0:10:41with everything exploding out from that point,
0:10:41 > 0:10:45moving away only from that one central location.
0:10:45 > 0:10:47That's really the wrong picture here.
0:10:47 > 0:10:49That makes it sound like we're in a special place,
0:10:49 > 0:10:52like somehow we're at the centre, and everything is moving away from us.
0:10:52 > 0:10:54But actually it's not like that.
0:10:56 > 0:10:59There's nothing special about our place in the universe.
0:11:00 > 0:11:06If we went to another galaxy, we'd see exactly the same thing.
0:11:06 > 0:11:07If you went to a distant galaxy,
0:11:07 > 0:11:10they would have the same perspective.
0:11:10 > 0:11:12They would look at all the galaxies around them
0:11:12 > 0:11:14and see that they were moving away.
0:11:14 > 0:11:16You really have to try to imagine
0:11:16 > 0:11:19that every single point is moving away from every other point.
0:11:19 > 0:11:21So no point is special.
0:11:21 > 0:11:23No matter where you're standing in the universe,
0:11:23 > 0:11:26if you look out, you will see galaxies moving away from you.
0:11:28 > 0:11:31Think of it like cities on the map of America.
0:11:33 > 0:11:35If you were standing in California,
0:11:35 > 0:11:38you would see New York moving away from you.
0:11:38 > 0:11:40But, from the perspective of New York,
0:11:40 > 0:11:42you would see Boston move away.
0:11:42 > 0:11:44And if you were standing in Chicago,
0:11:44 > 0:11:48you would see New York and California moving away from you.
0:11:48 > 0:11:50So, no matter where you're standing,
0:11:50 > 0:11:52you see everything else moving away from you.
0:11:54 > 0:11:55In the observable universe,
0:11:55 > 0:11:58the galaxies are doing exactly the same thing.
0:12:01 > 0:12:06The only explanation for that is that the space itself is stretching,
0:12:06 > 0:12:08that the universe itself is getting bigger,
0:12:08 > 0:12:10not that the galaxies are moving on the space,
0:12:10 > 0:12:13but that the space is getting bigger.
0:12:14 > 0:12:19It's as if the whole of America was getting bigger and bigger every day.
0:12:20 > 0:12:24You'd think it would be impossible to keep the map up to date.
0:12:26 > 0:12:28But cosmologists take everything into account,
0:12:28 > 0:12:32by using careful measurements of the expansion rate.
0:12:34 > 0:12:37It works like the scale factor on any road map.
0:12:41 > 0:12:44Imagine the United States is doubling every day.
0:12:44 > 0:12:46You wouldn't want to make a new map every day,
0:12:46 > 0:12:48you wouldn't draw a new map.
0:12:48 > 0:12:52All you would have to do really is change the legend.
0:12:52 > 0:12:54Instead of one mile between tick marks,
0:12:54 > 0:12:57the next day would be two miles, the next day would be four miles.
0:12:57 > 0:13:00And that scale, changing on the side in your legend,
0:13:00 > 0:13:04would completely account for the fact that the States kept doubling.
0:13:04 > 0:13:07And so you could keep your originally drawn map.
0:13:11 > 0:13:14The map of the observable universe doesn't change
0:13:14 > 0:13:16except for the scale factor.
0:13:17 > 0:13:21Right now, it's 46 billion light years to the edge.
0:13:23 > 0:13:25But it's growing all the time.
0:13:29 > 0:13:31So, while, at first, this is a little confusing,
0:13:31 > 0:13:34trying to imagine something like a universe expanding,
0:13:34 > 0:13:37we realise that, by drawing a simple map
0:13:37 > 0:13:39and, by changing the scale on that map,
0:13:39 > 0:13:42that we can handle the expansion actually quite simply.
0:13:46 > 0:13:52For cosmologists, the expansion of the universe is not a problem.
0:13:52 > 0:13:53In fact, it's a gift.
0:13:55 > 0:13:56If space is stretching,
0:13:56 > 0:14:00then the wavelength of light from the galaxies is stretching too.
0:14:02 > 0:14:05The greater the distance, the redder the light.
0:14:06 > 0:14:08This red shift effect
0:14:08 > 0:14:12is the mapmaker's vital tool for measuring distance.
0:14:16 > 0:14:19And red shift was the key to the next vital stage
0:14:19 > 0:14:21in mapping the universe.
0:14:23 > 0:14:26A survey to pinpoint the exact location of galaxies,
0:14:26 > 0:14:30stretching 5.5 billion light years from Earth.
0:14:40 > 0:14:45It started here, in one of the more unusual towns in America.
0:14:49 > 0:14:53Welcome to Cloudcroft, New Mexico.
0:14:57 > 0:15:01A place where you don't have to be an astronomer to map the universe.
0:15:04 > 0:15:07Everyone in town can have a piece of the action.
0:15:12 > 0:15:17To us, it's wonderful - I mean, it's just part of our everyday life.
0:15:17 > 0:15:19On a clear night, my husband will say,
0:15:19 > 0:15:22"Well, you're going to be busy tomorrow!"
0:15:22 > 0:15:26Frances Cope has been working here for two-and-a-half years.
0:15:29 > 0:15:31The last count, she'd mapped a quarter of a million galaxies.
0:15:34 > 0:15:40It can be very therapeutic but mostly it's, to me personally,
0:15:40 > 0:15:42it's a sense of fulfilment.
0:15:42 > 0:15:45Tracey Naugle trained as a mechanic,
0:15:45 > 0:15:48then retrained in galactic exploration.
0:15:51 > 0:15:56It's neat that you are a part of discovering new galaxies,
0:15:56 > 0:15:58it's kind of a good feeling.
0:15:58 > 0:16:01Kristina Huehnerhoff is a freelance writer.
0:16:02 > 0:16:05Mapping the universe helps her wind down.
0:16:07 > 0:16:11It's very Zen, I think, because you're, you know,
0:16:11 > 0:16:15you're putting things where they're supposed to be.
0:16:15 > 0:16:17They all work with this man.
0:16:19 > 0:16:21David Schlegel is a cosmologist
0:16:21 > 0:16:25from the University of California at Berkeley.
0:16:25 > 0:16:27When he first came to town,
0:16:27 > 0:16:30the map of the universe was almost empty.
0:16:30 > 0:16:34The only pictures we had of the full sky were on photographic plates,
0:16:34 > 0:16:39images taken by Palomar Sky Survey in the 1950s.
0:16:39 > 0:16:43And actually we were still using that in the 1990s,
0:16:43 > 0:16:45that was the best picture that we had of the full sky.
0:16:47 > 0:16:50The Palomar Survey was practically a museum piece -
0:16:50 > 0:16:55photographed on fragile glass negatives.
0:16:55 > 0:16:56Even by 1998,
0:16:56 > 0:17:01only 30,000 galaxies had been placed on the map of the universe.
0:17:05 > 0:17:09That's when David joined the Sloan Digital Sky Survey
0:17:09 > 0:17:12at the nearby Apache Point Observatory.
0:17:16 > 0:17:18We had the sense that it was going to be this great thing
0:17:18 > 0:17:22that was starting, but it hadn't actually started yet.
0:17:22 > 0:17:25What we wanted to do was something much more ambitious
0:17:25 > 0:17:29and actually get a map of the million brightest galaxies on the sky.
0:17:30 > 0:17:34The task required measuring the distance, and therefore red shift,
0:17:34 > 0:17:38for every single one of these galaxies.
0:17:39 > 0:17:42Obviously you need to look at more than one galaxy at a time,
0:17:42 > 0:17:44so that's the trick.
0:17:44 > 0:17:48If you were a futurist you'd say,
0:17:48 > 0:17:52"Well, it's the 1990s, we have computers and we have robots."
0:17:52 > 0:17:55The folks designing the Sloan, though,
0:17:55 > 0:17:57decided to take the pragmatic approach
0:17:57 > 0:18:01and say, well, we actually want this thing to work.
0:18:03 > 0:18:07Instead of robots, the ingenious system they came up with
0:18:07 > 0:18:10required a far more human touch.
0:18:12 > 0:18:15And they would have to go round the universe
0:18:15 > 0:18:17not once, but twice.
0:18:21 > 0:18:25It's really doing two maps of the sky.
0:18:25 > 0:18:29The first time round, they didn't measure any red shifts.
0:18:31 > 0:18:34The telescope simply took photographs...
0:18:34 > 0:18:38A map of the sky, but in two dimensions only.
0:18:40 > 0:18:44It doesn't give the distance to each galaxy - yet.
0:18:44 > 0:18:48We actually have from those images not very much idea
0:18:48 > 0:18:50of where these things are in three dimensional space.
0:18:50 > 0:18:54So at some level, it's just a pretty picture.
0:18:54 > 0:18:56But the next stage was the trick.
0:18:58 > 0:19:02They printed the pretty pictures in metal.
0:19:02 > 0:19:06Each of these holes corresponds to our two dimensional location
0:19:06 > 0:19:10of a galaxy on the sky, where if I look at this hole,
0:19:10 > 0:19:13we have the longitude on this coordinate,
0:19:13 > 0:19:16the latitude in this coordinate, and so the whole design
0:19:16 > 0:19:20of this system is to as efficiently as possible get the light
0:19:20 > 0:19:25from that one galaxy into that specific hole.
0:19:25 > 0:19:29The plugging team from town connected every galaxy
0:19:29 > 0:19:30with a fibre optic cable...
0:19:32 > 0:19:36..then fitted the plate back over the telescope.
0:19:38 > 0:19:42Second time around, the telescope measures the red shifts
0:19:42 > 0:19:44for these specific galaxies alone.
0:19:48 > 0:19:511,000 galaxies on a plate,
0:19:51 > 0:19:53nine plates a night
0:19:53 > 0:19:56and one million galaxies in total
0:19:56 > 0:20:00on a map crafted by human hands.
0:20:00 > 0:20:05It's hard to wrap my head around the idea that we're looking at...
0:20:05 > 0:20:09you know, with 1,000 fibres, we're looking at 1,000 galaxies,
0:20:09 > 0:20:12and it's... I have a hard time wrapping my head around
0:20:12 > 0:20:13that the universe is that big.
0:20:16 > 0:20:21The Sloan Survey is one of the great achievements of Precision Cosmology.
0:20:26 > 0:20:28Red shift measures the distance -
0:20:28 > 0:20:31the third and final co-ordinate for every galaxy...
0:20:33 > 0:20:37..to make a 3D Movie on a colossal scale.
0:20:41 > 0:20:45Maybe you've seen things like this in the opening of Star Trek
0:20:45 > 0:20:48or Star Wars or whatever, and that all looks great,
0:20:48 > 0:20:49but it's not real.
0:20:49 > 0:20:52This movie - it is the real Universe.
0:20:54 > 0:20:58Every point of light on the map is a galaxy like the Milky Way.
0:21:01 > 0:21:04Cosmologists can now see at a glance
0:21:04 > 0:21:07how the galaxies are arranged in space.
0:21:12 > 0:21:13What these maps let us do,
0:21:13 > 0:21:18is it really allows us to test all the forces of nature we know about.
0:21:20 > 0:21:24There is structure, really, on all scales.
0:21:24 > 0:21:27The galaxies are not just placed at random -
0:21:27 > 0:21:32they're bound together by gravity, in a vast cosmic web.
0:21:35 > 0:21:39This goes on and on, and in fact up to the largest scales
0:21:39 > 0:21:42that we can see. You can still trace these structures of galaxies.
0:21:44 > 0:21:47But the most surprising discovery is what can't be seen.
0:21:49 > 0:21:52Most of the universe is missing.
0:21:54 > 0:21:57The gravity, due to the stuff that we see, due to say the galaxies
0:21:57 > 0:21:59and stars, can't do the job.
0:22:02 > 0:22:06It's simply not enough stuff to arrange things into the patterns
0:22:06 > 0:22:09that we see, have galaxies spinning in the way that they do.
0:22:09 > 0:22:13There's something else there. There's something beyond
0:22:13 > 0:22:15the galaxies that we see, the visible matter.
0:22:15 > 0:22:18There's some sort of Dark Matter out there.
0:22:20 > 0:22:24Modern cosmology needs a new kind of map maker.
0:22:31 > 0:22:34Because most of the universe is hiding in the dark.
0:22:39 > 0:22:41We don't know what Dark Matter is
0:22:41 > 0:22:44because it's never been detected on Earth.
0:22:47 > 0:22:49We know it must be out there,
0:22:49 > 0:22:53because its gravity is holding the cosmic web of galaxies together.
0:22:55 > 0:22:58But we can't see it, because it doesn't give off light.
0:23:00 > 0:23:04Someone has to find it and put it on the map.
0:23:09 > 0:23:13British astronomer Richard Massey is a master of the invisible.
0:23:21 > 0:23:23He's a member of a team hunting for Dark Matter,
0:23:23 > 0:23:27based at the California Institute of Technology.
0:23:27 > 0:23:32So, he's a frequent flyer to the city of Los Angeles.
0:23:33 > 0:23:35When you're flying over America at night,
0:23:35 > 0:23:38you see these criss-crossing lanes of street lights
0:23:38 > 0:23:40spread out across the continent.
0:23:44 > 0:23:47There's obviously some interesting stories going on down there,
0:23:47 > 0:23:49in between these roads.
0:23:53 > 0:23:56In fact, most of the story of what's going on in America
0:23:56 > 0:24:00is actually happening in those empty spaces that you can't see.
0:24:00 > 0:24:05Richard's task is like mapping those apparently empty spaces.
0:24:07 > 0:24:10It's as if whole cities were hiding in the dark.
0:24:12 > 0:24:16If we're driving across America, and trying to map out a new frontier,
0:24:16 > 0:24:18we can see mountains and valleys
0:24:18 > 0:24:20and streams and we can draw them all on a map.
0:24:20 > 0:24:23But when we're trying to map out the universe,
0:24:23 > 0:24:26most of its contents are invisible.
0:24:29 > 0:24:33It takes imagination to find your way in a Dark Universe.
0:24:35 > 0:24:39You have to dream up new ways to detect what can't be seen.
0:24:42 > 0:24:46One possibility is that if Dark Matter doesn't give off light
0:24:46 > 0:24:49maybe it absorbs light.
0:24:51 > 0:24:55Ordinary matter, the stuff that we're made out of, casts a shadow -
0:24:55 > 0:24:57because it absorbs light.
0:25:00 > 0:25:02So we can see the ordinary matter in silhouette.
0:25:04 > 0:25:09Unfortunately, Dark Matter doesn't give itself away that easily.
0:25:11 > 0:25:15Light just goes straight through it.
0:25:15 > 0:25:17Dark Matter doesn't interact with light in any way,
0:25:17 > 0:25:23so we can't look for its silhouette to map out where it is.
0:25:23 > 0:25:26We have to be a bit more ingenious about it.
0:25:33 > 0:25:36The solution depends on a very simple idea.
0:25:39 > 0:25:42It's like looking at lights in a swimming pool.
0:25:45 > 0:25:49The secret to mapping Dark Matter that you can't see,
0:25:49 > 0:25:51is to look at the light that you can see.
0:25:53 > 0:25:56Everything that has mass, including Dark Matter,
0:25:56 > 0:26:01actually bends the fabric of space and time that we're that we live in.
0:26:01 > 0:26:05And if space is warped, then everything in it is distorted.
0:26:05 > 0:26:07Even the paths of light rays.
0:26:09 > 0:26:13The only way that Dark Matter might reveal itself is through gravity.
0:26:15 > 0:26:18According to Einstein's Theory of Relativity,
0:26:18 > 0:26:22all matter distorts space causing light to change direction.
0:26:24 > 0:26:27The idea of General Relativity bending space and time
0:26:27 > 0:26:29and deflecting rays of light sounds complicated.
0:26:29 > 0:26:32But actually you see light rays bending all the time.
0:26:32 > 0:26:36Look into a swimming pool and see your legs aren't in the right shape,
0:26:36 > 0:26:40you know that there must be some water in the way.
0:26:40 > 0:26:46The distortion of the lights depends on water ripples in the pool.
0:26:46 > 0:26:49which in turn depend on where the swimmers are at any one moment.
0:26:52 > 0:26:53Ah!
0:26:56 > 0:27:00This is great, we're seeing these distorted images of lights
0:27:00 > 0:27:03under the pool and by looking at the shapes of these, we can work out
0:27:03 > 0:27:07what the ripples in the water are doing.
0:27:07 > 0:27:10The survey team went looking for Dark Matter in exactly
0:27:10 > 0:27:13the same way...
0:27:14 > 0:27:18..with 1,000 hours of observations on the Hubble Space Telescope.
0:27:20 > 0:27:23By looking at distant galaxies halfway across the universe,
0:27:23 > 0:27:24by looking at their shapes
0:27:24 > 0:27:27and the distorted images that we see of those,
0:27:27 > 0:27:31we can work out what ripples there are in space between them and us.
0:27:31 > 0:27:35And those ripples in space are caused by the Dark Matter.
0:27:41 > 0:27:45The search zone was a thin column of the universe,
0:27:45 > 0:27:47stretching eight billion light years from Earth.
0:27:49 > 0:27:51The team were on the look-out
0:27:51 > 0:27:53for distortions in the most distant galaxies.
0:27:55 > 0:27:57Whenever you see galaxies
0:27:57 > 0:28:00distorted into these strange uncharacteristic shapes,
0:28:00 > 0:28:03you know that there must be something in between them and you,
0:28:03 > 0:28:06something really massive, and even if it's invisible,
0:28:06 > 0:28:11you can still map out where it is by the way it warps that space time.
0:28:11 > 0:28:17The mapping technique revealed a ghostly, hidden universe.
0:28:17 > 0:28:23The light from visible galaxies was recast in new and beautiful forms.
0:28:24 > 0:28:26They've become these full rings,
0:28:26 > 0:28:30distorted just like what are known as Einstein Rings,
0:28:30 > 0:28:33whenever there's a big lump of Dark Matter in front of them.
0:28:33 > 0:28:37The lumps become contours on a map of the invisible.
0:28:39 > 0:28:42They reveal Dark Matter as the hidden iceberg
0:28:42 > 0:28:45beneath the surface of the cosmic ocean.
0:28:48 > 0:28:51What we're finding out there in the universe is really weird.
0:28:51 > 0:28:54It's equivalent to the idea that only one out of six cities in America
0:28:54 > 0:28:56actually has any people living in it.
0:28:56 > 0:28:59The other five sixths of the population
0:28:59 > 0:29:01are these invisible ghosts that we just can't see.
0:29:03 > 0:29:06The survey has transformed the map of the universe.
0:29:10 > 0:29:12It suggests that normal, visible matter
0:29:12 > 0:29:15is just a fraction of what's out there.
0:29:17 > 0:29:21In the search zone, Dark Matter outweighs it by six to one.
0:29:24 > 0:29:27This is the stuff the universe is really made of.
0:29:34 > 0:29:38For cosmologists, the road ahead has become a lot less certain.
0:29:41 > 0:29:45Right now, we know the universe is expanding.
0:29:45 > 0:29:48But given enough Dark Matter, it could have a different,
0:29:48 > 0:29:51and very dark future.
0:29:52 > 0:29:54It's sensible to conclude,
0:29:54 > 0:29:57when we look at how that stuff affects the shape of space,
0:29:57 > 0:30:01that the universe should be expanding but that it should be slowing down.
0:30:03 > 0:30:07Dark Matter puts a very heavy foot on the brakes.
0:30:08 > 0:30:13Because the more matter there is, the more gravity there is.
0:30:16 > 0:30:20Gravity attracts. And so the cosmic expansion should be slowed down
0:30:20 > 0:30:22by all that attraction.
0:30:26 > 0:30:28If there's enough Dark Matter,
0:30:28 > 0:30:31the universe will eventually stop expanding altogether...
0:30:31 > 0:30:33..and go into reverse.
0:30:36 > 0:30:38Gravity will bring everything back together,
0:30:38 > 0:30:41in a final, cataclysmic big crunch.
0:30:49 > 0:30:53The question is - when?
0:30:55 > 0:30:57The search for the answer began here
0:30:57 > 0:31:00on the Berkeley Campus of the University of California.
0:31:04 > 0:31:09It's a distinctive outpost in the landscape of science
0:31:09 > 0:31:14signposted with some of its greatest names.
0:31:17 > 0:31:21There's even a car park reserved for Nobel Laureates.
0:31:24 > 0:31:29Nine prize winners in a row - with five in Physics alone.
0:31:31 > 0:31:36And it was here, in 1988, that Saul Perlmutter set out
0:31:36 > 0:31:39to map the deceleration of the universe.
0:31:51 > 0:31:54There's nothing you like more than a really good mystery.
0:31:55 > 0:31:58I wondered if you could actually measure,
0:31:58 > 0:32:01how much the universe was slowing down.
0:32:01 > 0:32:03I thought it was a very exciting possibility that you could,
0:32:03 > 0:32:08make a measurement, and find out what the fate of the universe was.
0:32:08 > 0:32:10Saul was the leading light
0:32:10 > 0:32:13behind an international team of physicists and astronomers.
0:32:17 > 0:32:22Under his guidance, they embarked on a ten year voyage of exploration
0:32:22 > 0:32:25far across the observable universe.
0:32:33 > 0:32:36The key was to measure how fast the universe was expanding
0:32:36 > 0:32:42in the past, compared to now. They planned to map ancient galaxies -
0:32:42 > 0:32:4410.8 billion light years from Earth.
0:32:47 > 0:32:50But it would take a whole decade to find and analyse
0:32:50 > 0:32:52what they were looking for.
0:32:53 > 0:32:55A candle.
0:32:57 > 0:33:00If you want to measure distances across the universe
0:33:00 > 0:33:06you would like to be able to use an object that's of known brightness.
0:33:06 > 0:33:10We call anything that we know the brightness of a Standard Candle.
0:33:11 > 0:33:14A Standard Candle always has the same brightness -
0:33:14 > 0:33:19so you can use it to measure distance very precisely.
0:33:19 > 0:33:20The further away it is,
0:33:20 > 0:33:24the dimmer it will appear in our telescopes.
0:33:24 > 0:33:26But candles are elusive objects.
0:33:26 > 0:33:31We hunt, for what astronomical object could you possibly use,
0:33:31 > 0:33:34that will behave in this very regular way,
0:33:34 > 0:33:36so that you can actually compare the distances.
0:33:38 > 0:33:40The galaxies themselves are no good.
0:33:40 > 0:33:44They come in many different shapes and sizes
0:33:44 > 0:33:47and at this distance, they're so dim we can barely see them.
0:33:50 > 0:33:53We're talking about distances that are even more vast than usual
0:33:53 > 0:33:56for astronomy. Now we need to look at some of the most distant objects
0:33:56 > 0:33:59in the universe so these had to be very bright objects.
0:33:59 > 0:34:02Saul had a very bright idea.
0:34:06 > 0:34:09He would find his way by the light of a dying star.
0:34:11 > 0:34:12A supernova.
0:34:14 > 0:34:16When one of these supernovas explode,
0:34:16 > 0:34:20that one star can be as bright as the entire galaxy
0:34:20 > 0:34:23of a hundred billion other stars.
0:34:26 > 0:34:29So this is a remarkably bright, single event.
0:34:31 > 0:34:34Saul had a special kind of supernova in mind.
0:34:39 > 0:34:40A Type 1A is triggered
0:34:40 > 0:34:44when a dying star draws in mass from its neighbour.
0:34:48 > 0:34:51Just at the point where there's a critical mass,
0:34:51 > 0:34:55there will be a runaway thermonuclear explosion.
0:34:59 > 0:35:02So that means that it's triggered at the same mass every time.
0:35:05 > 0:35:09Same mass every time means same brightness every time.
0:35:09 > 0:35:13They're perfect standard candles.
0:35:13 > 0:35:15But Saul had to find them first.
0:35:18 > 0:35:21If you could work with anything else in the world
0:35:21 > 0:35:24besides a supernova to do your research you would.
0:35:24 > 0:35:26They're just a real pain in the neck to work with.
0:35:31 > 0:35:33They're rare, they're random and they're rapid.
0:35:33 > 0:35:37A supernova only burns brightly for three weeks.
0:35:37 > 0:35:42And in any given galaxy, they explode without warning
0:35:42 > 0:35:46roughly once every 300 years.
0:35:46 > 0:35:49With those odds, you can't book valuable time
0:35:49 > 0:35:50on the world's best telescopes.
0:35:52 > 0:35:55It makes a terrible proposal, if you were to say that,
0:35:55 > 0:35:57"Sometime in the next several hundred years,
0:35:57 > 0:36:00"a Type 1a supernova, might explode, somewhere in this galaxy.
0:36:00 > 0:36:03"I would like the night of March the 3rd, just in case."
0:36:05 > 0:36:10But Saul had a plan to get the odds working in his favour.
0:36:10 > 0:36:14With billions of galaxies in the observable universe -
0:36:14 > 0:36:17there are dozens of supernovae every night.
0:36:21 > 0:36:23Saul's team spent six years
0:36:23 > 0:36:26perfecting a new system for supernovae on demand.
0:36:28 > 0:36:33They took snapshots of thousands of galaxies at once,
0:36:33 > 0:36:36then repeated them two and a half weeks later.
0:36:36 > 0:36:41First you don't see a supernova.
0:36:41 > 0:36:43Now you do.
0:36:45 > 0:36:48That's very important, that two and a half weeks,
0:36:48 > 0:36:51because that guarantees, that everything you find, that's brighter,
0:36:51 > 0:36:54on the second night than the first, is on the way up.
0:37:01 > 0:37:04We can now guarantee that there would not just be one
0:37:04 > 0:37:07Type 1A supernova, but there would be a half dozen.
0:37:11 > 0:37:15Saul now knew exactly where to point
0:37:15 > 0:37:17one of the world's most powerful telescopes -
0:37:17 > 0:37:20the Keck Observatory in Hawaii.
0:37:22 > 0:37:28He was finally ready to measure the deceleration of the universe.
0:37:29 > 0:37:31But by late in 1997,
0:37:31 > 0:37:34the team was getting some very weird results.
0:37:38 > 0:37:43The points were not showing up where you would expect.
0:37:43 > 0:37:45This was exciting.
0:37:45 > 0:37:48The supernovae distance measurements
0:37:48 > 0:37:52didn't match the predicted deceleration.
0:37:55 > 0:37:57We were then faced with the question,
0:37:57 > 0:37:59"OK, what else could be going wrong?"
0:37:59 > 0:38:03Saul and his team spent five more anxious months,
0:38:03 > 0:38:05eliminating all possible sources of error.
0:38:05 > 0:38:09But by January 1998 they were finally ready to go public.
0:38:12 > 0:38:14The more we checked, the more we,
0:38:14 > 0:38:18fine tuned every little step of the calibration,
0:38:18 > 0:38:21the more the weird result didn't go away.
0:38:21 > 0:38:24The weird result has reverberated through
0:38:24 > 0:38:25the world of science ever since.
0:38:28 > 0:38:29In January 2012,
0:38:29 > 0:38:33Saul Perlmutter won the Nobel Prize for Physics
0:38:33 > 0:38:37and booked a parking space for life.
0:38:38 > 0:38:43At the end, we concluded that actually, the universe really isn't slowing down,
0:38:43 > 0:38:45it's actually speeding up in its expansion.
0:38:45 > 0:38:48And that was a big shock.
0:38:51 > 0:38:56It's been described as one of the biggest shocks in modern cosmology.
0:39:02 > 0:39:04This is a Runaway Universe
0:39:04 > 0:39:07and everyone's on board -
0:39:07 > 0:39:09whether we like it or not.
0:39:12 > 0:39:14We find out that the universe is not just expanding,
0:39:14 > 0:39:18but that it's getting faster and faster.
0:39:18 > 0:39:21The cosmological community, when this result came out,
0:39:21 > 0:39:22was completely incredulous.
0:39:22 > 0:39:25I didn't believe it when I first heard about it.
0:39:25 > 0:39:28I don't even think I paid very much attention to it at the time.
0:39:28 > 0:39:32We know the universe doesn't look like this.
0:39:32 > 0:39:34There had to be something wrong with these observations.
0:39:34 > 0:39:36I thought they would go away, I really did.
0:39:39 > 0:39:41Of course, I was wrong.
0:39:44 > 0:39:47It's sometimes really fun to be wrong.
0:39:52 > 0:39:55Welcome to a very new picture of the universe.
0:39:58 > 0:40:01But even the experts can hardly believe it's real.
0:40:03 > 0:40:09The most famous force in physics has met its match -
0:40:09 > 0:40:13because the entire universe is defying gravity.
0:40:16 > 0:40:19This was saying that there was something
0:40:19 > 0:40:22that fills the universe, and causes an anti-gravity force.
0:40:22 > 0:40:26Something that was causing everything to push everything else apart,
0:40:26 > 0:40:28and to make the universe bigger and bigger
0:40:28 > 0:40:29in an accelerated way.
0:40:29 > 0:40:32Gravity acts as a brake -
0:40:32 > 0:40:35pulling back on the expansion of the universe.
0:40:35 > 0:40:39But we now know there's another, more mysterious force -
0:40:39 > 0:40:43with its foot on the gas.
0:40:43 > 0:40:46What's doing the pushing? What's that force that's forcing everything apart?
0:40:46 > 0:40:49Well, we don't know, but we did work out what to call it.
0:40:49 > 0:40:51We have a name for it. We call it dark energy.
0:40:53 > 0:40:56Cosmologists don't know what dark energy is.
0:40:58 > 0:41:01They only know what it does.
0:41:01 > 0:41:05Where gravity pulls -
0:41:05 > 0:41:09dark energy pushes.
0:41:10 > 0:41:13You don't see this stuff.
0:41:13 > 0:41:15You don't see it doing anything, directly.
0:41:15 > 0:41:17Basically, it's sort of this one hit wonder,
0:41:17 > 0:41:20that just does one thing, it causes an anti-gravity force.
0:41:20 > 0:41:24We don't have any other handle on it.
0:41:24 > 0:41:27Dark energy is dark matter's dark adversary.
0:41:29 > 0:41:32A shadow on the entire universe.
0:41:35 > 0:41:37There's dark energy in the galaxy.
0:41:37 > 0:41:38There's dark energy, here on Earth.
0:41:38 > 0:41:42There's dark energy passing through us right now. We're filled with this dark energy.
0:41:42 > 0:41:44We don't see it - we don't feel it.
0:41:44 > 0:41:46But it's everywhere.
0:41:46 > 0:41:49It's kind of just a uniform colouration to our map.
0:41:49 > 0:41:5373% of the universe is dark energy,
0:41:53 > 0:41:54but you'd never know.
0:41:56 > 0:41:59In everyday life, this stuff is just hard to detect.
0:41:59 > 0:42:01Now, it's true that between my two fingers,
0:42:01 > 0:42:03there's an anti-gravity force, right now.
0:42:03 > 0:42:06But that anti-gravity force is so incredibly minuscule,
0:42:06 > 0:42:07that I'll never ever notice it.
0:42:07 > 0:42:09It's only when you get to really large scales,
0:42:09 > 0:42:12that you really see the affect of this stuff.
0:42:12 > 0:42:15If I could move my fingers, all the way across the universe,
0:42:15 > 0:42:19then they'd feel this tremendous push apart, due to this dark energy.
0:42:22 > 0:42:24In the really big scheme of things,
0:42:24 > 0:42:27dark matter is fighting a losing battle...
0:42:29 > 0:42:32..because there's only so much of it to go round.
0:42:35 > 0:42:37If you add more space,
0:42:37 > 0:42:41if you give more place for those little pieces of matter to be,
0:42:41 > 0:42:43then, the density of them goes down.
0:42:43 > 0:42:46You just see less of it - it gets diluted.
0:42:46 > 0:42:49As the universe expands, dark matter thins out
0:42:49 > 0:42:53until it can no longer compete with dark energy.
0:42:55 > 0:42:57The really crucial thing about how this dark energy behaves,
0:42:57 > 0:42:59is that it doesn't dilute.
0:42:59 > 0:43:01When the universe doubles in size,
0:43:01 > 0:43:04you've got twice as much dark energy.
0:43:04 > 0:43:08You make it four times as big, you've just got four times as much dark energy.
0:43:08 > 0:43:10Once you get to this cosmological scale,
0:43:10 > 0:43:13the biggest possible scale, it becomes the biggest game in town.
0:43:13 > 0:43:17It becomes the prime player.
0:43:17 > 0:43:20Dark energy is on the map.
0:43:21 > 0:43:23But cosmologists can't explain it.
0:43:25 > 0:43:28Depressing, or exciting? I think it's exciting.
0:43:28 > 0:43:31As a map maker, this is a strange thing.
0:43:31 > 0:43:36We go out, we make this map, we discover this land,
0:43:36 > 0:43:38we've mapped it out, and we still don't know what it is.
0:43:38 > 0:43:41I love that.
0:43:49 > 0:43:53The entire observable universe is saturated in dark energy.
0:43:57 > 0:44:02But there's one final set of clues to be found - on its furthest edge.
0:44:06 > 0:44:10And it may contain the secrets to the universe beyond.
0:44:20 > 0:44:24We're heading off the map into impossible territory.
0:44:27 > 0:44:31The edge of the observable universe
0:44:31 > 0:44:35is the furthest horizon our telescopes can see.
0:44:35 > 0:44:39But for cosmologists like Sean Carroll, that's not enough.
0:44:39 > 0:44:44He wants to know the size of the whole universe.
0:44:44 > 0:44:50I definitely think it's OK to think about parts of the universe that we can't observe and can never observe.
0:44:50 > 0:44:53We've done a very good job at understanding
0:44:53 > 0:44:56what the universe looks like in that visible portion.
0:44:56 > 0:44:58So now when our imaginations roam,
0:44:58 > 0:45:01they often sneak outside the visible portion to ask what might
0:45:01 > 0:45:04the universe look like beyond our visible horizon.
0:45:04 > 0:45:06The universe that we can't see -
0:45:06 > 0:45:09that's the playground for theorists now.
0:45:11 > 0:45:14But if we can't see the rest of the universe,
0:45:14 > 0:45:16how can we figure out how big it is?
0:45:18 > 0:45:21For Janna Levin, it's a similar task to working out the shape
0:45:21 > 0:45:24and size of the earth.
0:45:24 > 0:45:26But there's a catch.
0:45:28 > 0:45:32We know we could step far from the Earth, as an astronaut has.
0:45:32 > 0:45:34We can look down on it
0:45:34 > 0:45:39and see from the outside that it was a sphere and it was curved.
0:45:39 > 0:45:41You can't step outside of the universe.
0:45:41 > 0:45:46You have to do everything from inside of space.
0:45:46 > 0:45:48Without leaving the earth, how do you know it's round,
0:45:48 > 0:45:51and therefore has finite size?
0:45:53 > 0:45:55It could be completely flat,
0:45:55 > 0:45:58and stretch to infinity in all directions.
0:46:00 > 0:46:03One way is to use a simple piece of mathematics.
0:46:08 > 0:46:11All you have to do is draw a triangle.
0:46:18 > 0:46:22If you're drawing a small enough triangle on the beach,
0:46:22 > 0:46:24you won't notice the curvature of the earth.
0:46:24 > 0:46:28It will look like a normal triangle, you'll be able to draw the lines pretty straight
0:46:28 > 0:46:31and the interior angles will look like they add up to 180 degrees,
0:46:31 > 0:46:34it will look like the triangle you draw on a flat sheet of paper.
0:46:35 > 0:46:38But this isn't a normal triangle,
0:46:38 > 0:46:42because the earth's surface is curved.
0:46:42 > 0:46:44It's just so subtle,
0:46:44 > 0:46:46that the sides of the triangles still look straight.
0:46:46 > 0:46:51It would probably be a challenge on the beach to draw it big enough
0:46:51 > 0:46:55that you would be able to notice the curvature of the earth.
0:46:55 > 0:46:57The key is to make the curvature more obvious -
0:46:57 > 0:47:00by drawing the biggest triangle you can.
0:47:03 > 0:47:07If I draw a triangle big enough that it comes from the North Pole
0:47:07 > 0:47:11and it wraps all the way around North America,
0:47:11 > 0:47:16now it's very obvious that those angles are bigger than 180 degrees
0:47:16 > 0:47:19and that the sides of the triangle are not straight lines.
0:47:22 > 0:47:25So, we can show the earth is curved
0:47:25 > 0:47:29and therefore has finite size without leaving it.
0:47:29 > 0:47:32And we can find out the shape and size of the universe
0:47:32 > 0:47:36in exactly the same way -
0:47:36 > 0:47:40by looking for triangles of light.
0:47:42 > 0:47:45Light will travel in a straight line if the space is flat,
0:47:45 > 0:47:48and light itself will travel in an arc if the space is curved.
0:47:50 > 0:47:53These curves are going to be so subtle,
0:47:53 > 0:47:55more subtle than the curvature of the earth.
0:47:57 > 0:47:59We really have to look back
0:47:59 > 0:48:01as far as we possibly can.
0:48:01 > 0:48:03And that means the oldest relic we have in the universe.
0:48:03 > 0:48:05So that means looking at things
0:48:05 > 0:48:08like the light left over from the Big Bang.
0:48:18 > 0:48:22The early universe was a hot, dense fireball.
0:48:24 > 0:48:27When it cooled, a pattern of light emerged
0:48:27 > 0:48:30at what is now the edge of the observable universe.
0:48:30 > 0:48:34This is the cosmic microwave background.
0:48:40 > 0:48:43The CMB was discovered in the 1960s.
0:48:43 > 0:48:46But throughout his career, Sean Carroll
0:48:46 > 0:48:51has been able to explore it in greater and greater detail -
0:48:51 > 0:48:54waiting for triangles to emerge.
0:48:58 > 0:48:59It takes good technology to do it,
0:48:59 > 0:49:02you need better and better receivers,
0:49:02 > 0:49:05less and less noise in your detector,
0:49:05 > 0:49:07and ultimately you need satellites
0:49:07 > 0:49:09to get a really good 360 degree view
0:49:09 > 0:49:12of the whole cosmic microwave background.
0:49:17 > 0:49:21It was NASA's WMAP mission in 2003
0:49:21 > 0:49:25that brought the most vital contours into sharp focus.
0:49:29 > 0:49:31WMAP for the first time had that resolution
0:49:31 > 0:49:35so when WMAP came out, we could really use those features
0:49:35 > 0:49:37to make a big triangle and measure the geometry of space.
0:49:39 > 0:49:42Continents begin to appear, smaller islands,
0:49:42 > 0:49:47you get a finer resolution of the coastlines and so forth.
0:49:47 > 0:49:50The islands are miniscule temperature variations
0:49:50 > 0:49:55in the early universe - less than 100,000th of a degree...
0:49:57 > 0:50:01..a distinctive feature for making triangles.
0:50:11 > 0:50:16These splotches we see in the microwave background appear at all different sizes
0:50:16 > 0:50:18but there is a best size for them to be,
0:50:18 > 0:50:23there's a size at which the fluctuations are the strongest.
0:50:23 > 0:50:27We know how big they are, we know how far away they are,
0:50:27 > 0:50:31so between us and the size of a feature in the CMB,
0:50:31 > 0:50:35we can measure a triangle and use that to infer the geometry of space.
0:50:38 > 0:50:42The earth, plus the opposite sides of the island,
0:50:42 > 0:50:46form the three points of a very long, thin triangle -
0:50:46 > 0:50:50The key to measuring whether the universe is flat or curved.
0:50:53 > 0:50:55If the universe were positively curved,
0:50:55 > 0:50:58if the angles inside the triangle added up to greater
0:50:58 > 0:51:02than 180 degrees, then it would be finite in size.
0:51:02 > 0:51:04If the spatial geometry is flat,
0:51:04 > 0:51:07if the angles inside the triangle add up to 180,
0:51:07 > 0:51:10then it could go on for ever.
0:51:13 > 0:51:19The result is one of the greatest triumphs of modern cosmology.
0:51:19 > 0:51:21A miracle of precision map making
0:51:21 > 0:51:26that measures the angles of the triangle to the third decimal place.
0:51:28 > 0:51:33And it says that the universe is infinite.
0:51:33 > 0:51:36The answer is that Euclid was right,
0:51:36 > 0:51:38space seems to us to be flat as far as we can measure it.
0:51:41 > 0:51:44That means that the simplest picture of the universe,
0:51:44 > 0:51:45is a universe that's infinite.
0:51:45 > 0:51:48We really could live in a universe where,
0:51:48 > 0:51:52there's galaxy after galaxy after galaxy, in every direction.
0:51:52 > 0:51:55Up, down, sideways. And, it never stops.
0:51:55 > 0:51:58Cosmologists have found a way
0:51:58 > 0:52:02to picture the universe in its entirety -
0:52:02 > 0:52:06confirmation of the tremendous power of making maps.
0:52:06 > 0:52:09It will never cease to amaze me -
0:52:09 > 0:52:12we human beings here on this tiny little rock are able to reach out
0:52:12 > 0:52:15with our instruments and our brains
0:52:15 > 0:52:18to understand the whole shebang.
0:52:18 > 0:52:22And if an infinite universe isn't big enough for you -
0:52:22 > 0:52:26then Saul Perlmutter has proved it's still growing.
0:52:28 > 0:52:30All the distances are getting bigger, every day.
0:52:30 > 0:52:33So, it's still infinite, all the same galaxies are there,
0:52:33 > 0:52:35it's just that we have pumped more space
0:52:35 > 0:52:37between every point in this infinite universe.
0:52:39 > 0:52:41That's really mind boggling.
0:52:44 > 0:52:48But even this isn't the end of the story.
0:52:56 > 0:53:00There may be one final, bizarre twist in the road.
0:53:05 > 0:53:10Because Anthony Aguirre thinks our universe may not be alone.
0:53:16 > 0:53:19Sometimes when I'm headed down the highway and I'm driving,
0:53:19 > 0:53:21you know, my wife will say,
0:53:21 > 0:53:23"Anthony, you're going 40 on the highway."
0:53:23 > 0:53:26And then she knows that I'm thinking about other universes.
0:53:28 > 0:53:31He thinks there may be other universes
0:53:31 > 0:53:34because of the process that created our own.
0:53:34 > 0:53:38It's called inflation.
0:53:38 > 0:53:41It describes an exponential expansion
0:53:41 > 0:53:45in the moments after the Big Bang,
0:53:45 > 0:53:50at a speed the universe would never repeat again.
0:53:52 > 0:53:55Inflation has been a very successful theory in predicting
0:53:55 > 0:53:58observed properties of our universe
0:53:58 > 0:54:01and how our observed universe came into being.
0:54:03 > 0:54:07Inflation may have started out as a mathematical theory...
0:54:11 > 0:54:14..but it has gained acceptance after successful testing
0:54:14 > 0:54:18against the evidence from the cosmic microwave background.
0:54:18 > 0:54:24I was amazed when I saw the results come in from those satellites
0:54:24 > 0:54:26that reproduced all the bumps and wiggles
0:54:26 > 0:54:29and all the detailed properties of that microwave background
0:54:29 > 0:54:31that inflation had predicted.
0:54:31 > 0:54:38Inflation explains how the observable universe developed.
0:54:38 > 0:54:41It was doubling in size over and over again in a tiny fraction of a second,
0:54:41 > 0:54:44going from something like a billionth of the size of a proton
0:54:44 > 0:54:48to something maybe the size of a bubble, a soap bubble.
0:54:52 > 0:54:56But inflation didn't stop with our own universe.
0:54:56 > 0:55:00Anthony believes it may have happened over and over again.
0:55:04 > 0:55:06This is really a side effect.
0:55:06 > 0:55:09It's a huge side effect, it's an amazing side effect,
0:55:09 > 0:55:15but it's a side effect of something we invented already for a different purpose.
0:55:17 > 0:55:21It's a process called eternal inflation.
0:55:25 > 0:55:28There could be as many as we can imagine.
0:55:31 > 0:55:35Anthony's vision - of an infinite number of infinite universes -
0:55:35 > 0:55:37may sound far-fetched.
0:55:39 > 0:55:43But the search is on to find evidence to support it.
0:55:46 > 0:55:49Evidence from the oldest part of our map.
0:55:51 > 0:55:54Every once in a while we could have sort of a cosmic collision
0:55:54 > 0:55:55with another bubble.
0:56:00 > 0:56:03It would leave an impact, it would leave a bruise,
0:56:03 > 0:56:04a disc in the sky
0:56:04 > 0:56:08on the microwave background radiation that we could look for.
0:56:11 > 0:56:14Anthony and his colleagues have simulated
0:56:14 > 0:56:18what a collision of universes would look like.
0:56:20 > 0:56:26A dark bruise, superimposed on the cosmic microwave background.
0:56:26 > 0:56:30He doesn't yet have enough data to test it,
0:56:30 > 0:56:34but it's a tantalising glimpse of what the map could reveal
0:56:34 > 0:56:37with the next generation of satellites.
0:56:39 > 0:56:43In principle I think this scenario with all these bubbles
0:56:43 > 0:56:46is testable, we can actually go out and look for them.
0:56:46 > 0:56:52This may be the ultimate map of the universe.
0:56:56 > 0:56:59We're talking about understanding and testing and theorising
0:56:59 > 0:57:04in a scientific way about an infinite number of universes.
0:57:04 > 0:57:07It's simultaneously so mind-boggling
0:57:07 > 0:57:09and yet it's still rigorous science -
0:57:09 > 0:57:14we can do mathematics, we can do experiments, we can really test it.
0:57:20 > 0:57:23Some day we'll understand the universe so well
0:57:23 > 0:57:26that we can literally take that map, put it on a little compact disc
0:57:26 > 0:57:28and put it in our pockets and take it home.
0:57:43 > 0:57:48Subtitles by Red Bee Media Ltd