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The most ambitious map in history
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is taking shape before our eyes.
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And scientists are heading
for the edge.
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It may be the strangest map
you'll ever see.
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And it's bigger
than you can believe.
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It's a map of the entire universe.
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There's this whole pattern to the
universe we're starting to map out.
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Seeing it really brought home the
way the universe actually behaved,
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in a way that all the numbers
and equations never quite could.
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Cosmologists are making sense
of startling discoveries.
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Medieval maps would say,
"Here be monsters."
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They weren't entirely wrong.
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They're even building pictures
of the invisible.
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How do you map something
that you can't even see?
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Our brains build maps even
where our telescopes cannot reach.
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This is a map of everything we know.
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And it's getting bigger every day.
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It kind of hits you,
how magnificent it is.
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It's bigger than
we can actually really even imagine.
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The universe is so big,
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we may never find the edge.
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Mapping the universe
is a job for pioneers.
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Nick Risinger is blazing a trail
through the American south west.
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You have to be pretty persistent.
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No stopping.
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You've got to keep going.
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Nick wants to put our entire galaxy
on the map.
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He's on a single-handed mission,
to photograph the Milky Way.
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New Mexico is a great place
to take photos.
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It's dry, it's high,
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and there's not a whole lot of
city around here.
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There's a break in the weather,
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and you get a full,
almost a full night in.
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Other times, you only get,
you know, 10% of the night.
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But it's all luck of the draw.
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It's looking pretty good
over there, actually.
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In the modern world,
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few of us have skies dark enough
to see the Milky Way.
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But Nick plans to show us
our home galaxy
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like we've never seen it before.
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I'm trying to give people that broad,
big-picture understanding
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of the entire night sky,
and where they fit into that.
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Our galaxy has nearly
half a trillion stars.
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Most of them are too dim
and distant to see.
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But Nick's cameras
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are more than 2,000 times more
sensitive than the naked eye.
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If I had known how much work
it would be going into it,
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I probably wouldn't have
even started.
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But my personality is, once you
start something, you finish it.
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After two years, he's photographed
20 million stars...
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..by stitching together
more than 37,000 separate images.
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Some people might be driven crazy
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by hearing shutters clack
all night long.
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But it's actually music to my ears,
because it means they're working.
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By combining data from
six different cameras, he's captured
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something that would tax even the
world's most powerful telescopes.
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His final image is the highest
definition, true colour map
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ever made of the Milky Way.
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But he hasn't just mapped it...
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..he's made a hand-held
guide to the galaxy.
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This is like a window to the sky.
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And you can point it
in any direction
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and be shown exactly
what you're looking at.
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So here, we're looking at
the centre of our galaxy.
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This is our Milky Way.
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You can see this bright cluster
of many small stars.
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The map reveals more features
with every level of detail.
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As we zoom in here
to the centre of the galaxy,
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I'll point out this dark patch here,
this is the Pipe Nebula,
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and it's one of my favourite
landmarks to help me orient myself.
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But it's the sheer size of the image
that reveals its true ambition.
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From one side to the other,
it's 100,000 light years.
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This image is such a big subject,
and it makes you feel so small.
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100,000 light years!
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It boggles the mind just trying
to comprehend just how vast that is.
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But the fact is, the map
of the universe has barely begun.
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Anthony Aguirre, from the University
of California in Santa Cruz,
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is a theoretical cosmologist.
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So he's used to thinking big.
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Now to say that we're going to go
out and make a map of the universe,
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it almost sounds crazy.
It sounds like real hubris, right?
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"We're going to go
and map the universe!"
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And yet the universe, as it turns
out, is really amenable to mapping.
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But you have to think big,
and clever.
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And that's where
the balloons come in.
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Because the map of the universe
isn't like other maps.
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We have to think in a different way,
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we can't just go out and look at the
universe and draw things on paper
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and say,
"There's our map of the universe."
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The universe is so big
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that the laws of physics say
we can't see all of it.
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It's as if we're at the centre of a
giant balloon, and we can't see out.
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We can only see light.
And light moves at a certain speed.
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00:08:07,400 --> 00:08:10,680
And so, as we look
farther and farther away,
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we're looking farther and farther
back in time
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because we're seeing light
coming to us from long ago.
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But there's only so far
we can go back in time.
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So there's only so far we can see.
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It's called
the "observable universe".
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We can only map what's inside,
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because the universe is
only 13.7 billion years old.
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There may well be
a lot more universe outside,
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but the light hasn't had time
to reach us yet.
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In the last 20 years, we've seen
this tremendous expansion,
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both in the amount and in the
precision of knowledge that we have
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about the observable universe.
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This has allowed cosmologists to
make a map of unbelievable scale.
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00:09:09,280 --> 00:09:17,600
The Milky Way could fit inside
10 million million million times.
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Our entire galaxy's
just a dot on the landscape.
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In the observable universe,
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there are 170 billion galaxies
just like it.
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Janna Levin is a professor
of theoretical astrophysics.
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She'd like to put every single
galaxy we can see on the map.
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But, before she can do that,
it's vital to account for
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one of the most surprising features
of the universe.
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Making a map of the whole universe
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is not like mapping
a map of the United States.
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00:10:01,280 --> 00:10:06,360
It's an observational fact that, if
you look at the galaxies around us,
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and the most distant
galaxies that we can see,
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they all appear to be moving away
from us.
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And, the further away they are, the
faster they're moving away from us.
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The galaxies aren't
like landmarks on normal maps.
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They don't stand still.
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Everywhere we look, the most distant
galaxies are moving away from us.
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This a strange universe,
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and the explanation
is even stranger.
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People want to imagine
a central point
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with everything exploding out
from that point,
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moving away only from that
one central location.
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That's really
the wrong picture here.
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That makes it sound like
we're in a special place,
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like somehow we're at the centre, and
everything is moving away from us.
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But actually it's not like that.
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There's nothing special
about our place in the universe.
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00:11:01,600 --> 00:11:07,040
If we went to another galaxy,
we'd see exactly the same thing.
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If you went to a distant galaxy,
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they would have
the same perspective.
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They would look at
all the galaxies around them
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00:11:13,000 --> 00:11:14,800
and see that they were moving away.
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00:11:14,800 --> 00:11:17,040
You really have to try to imagine
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that every single point is
moving away from every other point.
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So no point is special.
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No matter where you're standing
in the universe,
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if you look out, you will see
galaxies moving away from you.
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Think of it like cities
on the map of America.
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If you were standing in California,
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you would see New York
moving away from you.
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But, from the perspective
of New York,
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you would see Boston move away.
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00:11:43,040 --> 00:11:45,480
And if you were standing in Chicago,
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00:11:45,480 --> 00:11:48,920
you would see New York
and California moving away from you.
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So, no matter where you're standing,
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you see everything else
moving away from you.
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In the observable universe,
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the galaxies are doing
exactly the same thing.
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The only explanation for that is
that the space itself is stretching,
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that the universe itself
is getting bigger,
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not that the galaxies
are moving on the space,
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but that the space
is getting bigger.
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It's as if the whole of America was
getting bigger and bigger every day.
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You'd think it would be impossible
to keep the map up to date.
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But cosmologists take
everything into account,
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by using careful measurements
of the expansion rate.
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It works like the scale factor
on any road map.
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Imagine the United States
is doubling every day.
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You wouldn't want to make
a new map every day,
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you wouldn't draw a new map.
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All you would have to do really
is change the legend.
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Instead of one mile
between tick marks,
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the next day would be two miles,
the next day would be four miles.
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00:12:58,320 --> 00:13:01,560
And that scale, changing
on the side in your legend,
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would completely account for the
fact that the States kept doubling.
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And so you could keep
your originally drawn map.
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The map of the observable universe
doesn't change
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except for the scale factor.
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Right now, it's 46 billion
light years to the edge.
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But it's growing all the time.
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So, while, at first,
this is a little confusing,
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trying to imagine something
like a universe expanding,
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we realise that,
by drawing a simple map
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and, by changing the scale
on that map,
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that we can handle the expansion
actually quite simply.
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For cosmologists, the expansion
of the universe is not a problem.
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In fact, it's a gift.
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If space is stretching,
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then the wavelength of light
from the galaxies is stretching too.
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The greater the distance,
the redder the light.
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00:14:07,440 --> 00:14:09,280
This red shift effect
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is the mapmaker's vital tool
for measuring distance.
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And red shift was the key
to the next vital stage
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in mapping the universe.
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00:14:23,920 --> 00:14:27,600
A survey to pinpoint
the exact location of galaxies,
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stretching 5.5 billion light years
from Earth.
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00:14:41,800 --> 00:14:45,840
It started here, in one of the
more unusual towns in America.
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Welcome to Cloudcroft, New Mexico.
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A place where you don't have to be
an astronomer to map the universe.
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Everyone in town can have a piece
of the action.
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To us, it's wonderful - I mean,
it's just part of our everyday life.
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On a clear night,
my husband will say,
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"Well, you're going
to be busy tomorrow!"
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Frances Cope has been working here
for two-and-a-half years.
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The last count, she'd mapped
a quarter of a million galaxies.
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It can be very therapeutic
but mostly it's, to me personally,
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it's a sense of fulfilment.
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00:15:43,600 --> 00:15:45,800
Tracey Naugle
trained as a mechanic,
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then retrained
in galactic exploration.
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00:15:52,640 --> 00:15:57,360
It's neat that you are a part of
discovering new galaxies,
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it's kind of a good feeling.
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00:15:59,600 --> 00:16:01,600
Kristina Huehnerhoff
is a freelance writer.
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Mapping the universe
helps her wind down.
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It's very Zen, I think,
because you're, you know,
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you're putting things
where they're supposed to be.
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00:16:16,480 --> 00:16:18,080
They all work with this man.
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00:16:19,880 --> 00:16:22,520
David Schlegel is a cosmologist
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from the University of California
at Berkeley.
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00:16:25,800 --> 00:16:27,840
When he first came to town,
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00:16:27,840 --> 00:16:30,960
the map of the universe
was almost empty.
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00:16:30,960 --> 00:16:35,520
The only pictures we had of the full
sky were on photographic plates,
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00:16:35,520 --> 00:16:40,200
images taken by Palomar Sky Survey
in the 1950s.
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00:16:40,200 --> 00:16:43,800
And actually we were
still using that in the 1990s,
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that was the best picture that we had
of the full sky.
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The Palomar Survey was
practically a museum piece -
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photographed on
fragile glass negatives.
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00:16:55,720 --> 00:16:57,440
Even by 1998,
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00:16:57,440 --> 00:17:02,360
only 30,000 galaxies had been
placed on the map of the universe.
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00:17:06,440 --> 00:17:09,680
That's when David
joined the Sloan Digital Sky Survey
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00:17:09,680 --> 00:17:13,320
at the nearby
Apache Point Observatory.
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00:17:16,960 --> 00:17:19,640
We had the sense that
it was going to be this great thing
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that was starting, but it hadn't
actually started yet.
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What we wanted to do was something
much more ambitious
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00:17:26,120 --> 00:17:29,720
and actually get a map of the million
brightest galaxies on the sky.
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00:17:31,640 --> 00:17:35,480
The task required measuring the
distance, and therefore red shift,
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00:17:35,480 --> 00:17:38,760
for every single one
of these galaxies.
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00:17:40,520 --> 00:17:43,200
Obviously you need to look
at more than one galaxy at a time,
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00:17:43,200 --> 00:17:45,400
so that's the trick.
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00:17:45,400 --> 00:17:48,880
If you were a futurist you'd say,
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00:17:48,880 --> 00:17:53,360
"Well, it's the 1990s, we have
computers and we have robots."
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00:17:53,360 --> 00:17:56,400
The folks designing the Sloan,
though,
239
00:17:56,400 --> 00:17:58,440
decided to take
the pragmatic approach
240
00:17:58,440 --> 00:18:01,920
and say, well, we actually want
this thing to work.
241
00:18:04,120 --> 00:18:07,800
Instead of robots, the ingenious
system they came up with
242
00:18:07,800 --> 00:18:11,160
required a far more human touch.
243
00:18:12,760 --> 00:18:15,880
And they would have to go round
the universe
244
00:18:15,880 --> 00:18:18,360
not once, but twice.
245
00:18:22,280 --> 00:18:26,440
It's really doing
two maps of the sky.
246
00:18:26,440 --> 00:18:30,400
The first time round, they didn't
measure any red shifts.
247
00:18:32,080 --> 00:18:35,120
The telescope
simply took photographs...
248
00:18:35,120 --> 00:18:39,440
A map of the sky,
but in two dimensions only.
249
00:18:40,880 --> 00:18:45,200
It doesn't give the distance
to each galaxy - yet.
250
00:18:45,200 --> 00:18:48,800
We actually have from
those images not very much idea
251
00:18:48,800 --> 00:18:51,600
of where these things are
in three dimensional space.
252
00:18:51,600 --> 00:18:55,440
So at some level,
it's just a pretty picture.
253
00:18:55,440 --> 00:18:57,480
But the next stage was the trick.
254
00:18:58,960 --> 00:19:03,600
They printed the pretty pictures
in metal.
255
00:19:03,600 --> 00:19:07,800
Each of these holes corresponds to
our two dimensional location
256
00:19:07,800 --> 00:19:11,520
of a galaxy on the sky,
where if I look at this hole,
257
00:19:11,520 --> 00:19:14,040
we have the longitude
on this coordinate,
258
00:19:14,040 --> 00:19:16,800
the latitude in this coordinate,
and so the whole design
259
00:19:16,800 --> 00:19:21,400
of this system is to as efficiently
as possible get the light
260
00:19:21,400 --> 00:19:26,200
from that one galaxy
into that specific hole.
261
00:19:26,200 --> 00:19:29,880
The plugging team from town
connected every galaxy
262
00:19:29,880 --> 00:19:31,240
with a fibre optic cable...
263
00:19:33,680 --> 00:19:37,120
..then fitted the plate
back over the telescope.
264
00:19:39,600 --> 00:19:43,200
Second time around, the telescope
measures the red shifts
265
00:19:43,200 --> 00:19:45,120
for these specific galaxies alone.
266
00:19:49,440 --> 00:19:52,560
1,000 galaxies on a plate,
267
00:19:52,560 --> 00:19:54,400
nine plates a night
268
00:19:54,400 --> 00:19:57,640
and one million galaxies in total
269
00:19:57,640 --> 00:20:01,720
on a map crafted by human hands.
270
00:20:01,720 --> 00:20:06,280
It's hard to wrap my head around
the idea that we're looking at...
271
00:20:06,280 --> 00:20:10,560
you know, with 1,000 fibres,
we're looking at 1,000 galaxies,
272
00:20:10,560 --> 00:20:13,160
and it's... I have a hard time
wrapping my head around
273
00:20:13,160 --> 00:20:14,520
that the universe is that big.
274
00:20:17,400 --> 00:20:22,000
The Sloan Survey is one of the great
achievements of Precision Cosmology.
275
00:20:27,160 --> 00:20:29,320
Red shift measures the distance -
276
00:20:29,320 --> 00:20:32,400
the third and final co-ordinate
for every galaxy...
277
00:20:33,960 --> 00:20:37,880
..to make a 3D Movie
on a colossal scale.
278
00:20:42,520 --> 00:20:46,000
Maybe you've seen things like this
in the opening of Star Trek
279
00:20:46,000 --> 00:20:49,080
or Star Wars or whatever,
and that all looks great,
280
00:20:49,080 --> 00:20:50,560
but it's not real.
281
00:20:50,560 --> 00:20:53,360
This movie -
it is the real Universe.
282
00:20:55,440 --> 00:20:59,080
Every point of light on the map
is a galaxy like the Milky Way.
283
00:21:02,640 --> 00:21:04,880
Cosmologists can now see at a glance
284
00:21:04,880 --> 00:21:08,200
how the galaxies
are arranged in space.
285
00:21:12,800 --> 00:21:14,040
What these maps let us do,
286
00:21:14,040 --> 00:21:19,080
is it really allows us to test all
the forces of nature we know about.
287
00:21:21,560 --> 00:21:25,200
There is structure,
really, on all scales.
288
00:21:25,200 --> 00:21:28,160
The galaxies are not just
placed at random -
289
00:21:28,160 --> 00:21:32,560
they're bound together by gravity,
in a vast cosmic web.
290
00:21:35,960 --> 00:21:39,800
This goes on and on, and
in fact up to the largest scales
291
00:21:39,800 --> 00:21:43,320
that we can see. You can still trace
these structures of galaxies.
292
00:21:44,920 --> 00:21:48,200
But the most surprising discovery
is what can't be seen.
293
00:21:50,600 --> 00:21:53,440
Most of the universe is missing.
294
00:21:54,920 --> 00:21:58,520
The gravity, due to the stuff that
we see, due to say the galaxies
295
00:21:58,520 --> 00:22:00,320
and stars, can't do the job.
296
00:22:03,000 --> 00:22:06,840
It's simply not enough stuff to
arrange things into the patterns
297
00:22:06,840 --> 00:22:10,120
that we see, have galaxies spinning
in the way that they do.
298
00:22:10,120 --> 00:22:13,960
There's something else there.
There's something beyond
299
00:22:13,960 --> 00:22:16,120
the galaxies that we see,
the visible matter.
300
00:22:16,120 --> 00:22:18,640
There's some sort of
Dark Matter out there.
301
00:22:21,320 --> 00:22:24,720
Modern cosmology
needs a new kind of map maker.
302
00:22:31,640 --> 00:22:35,080
Because most of the universe
is hiding in the dark.
303
00:22:40,480 --> 00:22:42,400
We don't know what Dark Matter is
304
00:22:42,400 --> 00:22:45,360
because it's never been detected
on Earth.
305
00:22:48,200 --> 00:22:49,760
We know it must be out there,
306
00:22:49,760 --> 00:22:53,600
because its gravity is holding the
cosmic web of galaxies together.
307
00:22:56,000 --> 00:22:59,080
But we can't see it, because it
doesn't give off light.
308
00:23:01,120 --> 00:23:04,720
Someone has to find it
and put it on the map.
309
00:23:09,840 --> 00:23:14,440
British astronomer Richard Massey is
a master of the invisible.
310
00:23:22,040 --> 00:23:24,640
He's a member of a team
hunting for Dark Matter,
311
00:23:24,640 --> 00:23:28,560
based at the California
Institute of Technology.
312
00:23:28,560 --> 00:23:32,760
So, he's a frequent flyer
to the city of Los Angeles.
313
00:23:34,400 --> 00:23:36,240
When you're flying over
America at night,
314
00:23:36,240 --> 00:23:39,080
you see these criss-crossing lanes
of street lights
315
00:23:39,080 --> 00:23:41,000
spread out across the continent.
316
00:23:45,320 --> 00:23:48,400
There's obviously some interesting
stories going on down there,
317
00:23:48,400 --> 00:23:50,440
in between these roads.
318
00:23:54,200 --> 00:23:57,320
In fact, most of the story
of what's going on in America
319
00:23:57,320 --> 00:24:01,000
is actually happening in those
empty spaces that you can't see.
320
00:24:01,000 --> 00:24:06,120
Richard's task is like mapping
those apparently empty spaces.
321
00:24:07,880 --> 00:24:10,520
It's as if whole cities
were hiding in the dark.
322
00:24:13,400 --> 00:24:17,000
If we're driving across America, and
trying to map out a new frontier,
323
00:24:17,000 --> 00:24:18,880
we can see mountains and valleys
324
00:24:18,880 --> 00:24:20,920
and streams and we can draw
them all on a map.
325
00:24:20,920 --> 00:24:24,160
But when we're trying to map out
the universe,
326
00:24:24,160 --> 00:24:26,920
most of its contents are invisible.
327
00:24:30,160 --> 00:24:33,600
It takes imagination to find your
way in a Dark Universe.
328
00:24:36,280 --> 00:24:39,840
You have to dream up new ways
to detect what can't be seen.
329
00:24:43,360 --> 00:24:46,920
One possibility is that if
Dark Matter doesn't give off light
330
00:24:46,920 --> 00:24:50,160
maybe it absorbs light.
331
00:24:52,400 --> 00:24:56,040
Ordinary matter, the stuff that
we're made out of, casts a shadow -
332
00:24:56,040 --> 00:24:57,880
because it absorbs light.
333
00:25:00,680 --> 00:25:03,360
So we can see the ordinary matter
in silhouette.
334
00:25:05,600 --> 00:25:09,640
Unfortunately, Dark Matter doesn't
give itself away that easily.
335
00:25:12,280 --> 00:25:15,760
Light just goes straight through it.
336
00:25:15,760 --> 00:25:18,600
Dark Matter doesn't interact
with light in any way,
337
00:25:18,600 --> 00:25:23,880
so we can't look for its silhouette
to map out where it is.
338
00:25:23,880 --> 00:25:27,520
We have to be a bit more
ingenious about it.
339
00:25:33,840 --> 00:25:37,280
The solution depends on
a very simple idea.
340
00:25:39,920 --> 00:25:43,360
It's like looking at lights in
a swimming pool.
341
00:25:46,400 --> 00:25:50,280
The secret to mapping Dark Matter
that you can't see,
342
00:25:50,280 --> 00:25:52,280
is to look at the light
that you can see.
343
00:25:53,920 --> 00:25:56,760
Everything that has mass,
including Dark Matter,
344
00:25:56,760 --> 00:26:01,840
actually bends the fabric of space
and time that we're that we live in.
345
00:26:01,840 --> 00:26:05,760
And if space is warped, then
everything in it is distorted.
346
00:26:05,760 --> 00:26:07,640
Even the paths of light rays.
347
00:26:09,760 --> 00:26:13,840
The only way that Dark Matter might
reveal itself is through gravity.
348
00:26:16,000 --> 00:26:18,720
According to Einstein's
Theory of Relativity,
349
00:26:18,720 --> 00:26:22,960
all matter distorts space causing
light to change direction.
350
00:26:25,520 --> 00:26:28,040
The idea of General Relativity
bending space and time
351
00:26:28,040 --> 00:26:30,360
and deflecting rays of
light sounds complicated.
352
00:26:30,360 --> 00:26:33,560
But actually you see light rays
bending all the time.
353
00:26:33,560 --> 00:26:36,800
Look into a swimming pool and see
your legs aren't in the right shape,
354
00:26:36,800 --> 00:26:40,920
you know that there must be
some water in the way.
355
00:26:40,920 --> 00:26:46,760
The distortion of the lights depends
on water ripples in the pool.
356
00:26:46,760 --> 00:26:50,400
which in turn depend on where
the swimmers are at any one moment.
357
00:26:53,040 --> 00:26:54,240
Ah!
358
00:26:57,520 --> 00:27:00,800
This is great, we're seeing these
distorted images of lights
359
00:27:00,800 --> 00:27:04,400
under the pool and by looking at
the shapes of these, we can work out
360
00:27:04,400 --> 00:27:08,280
what the ripples
in the water are doing.
361
00:27:08,280 --> 00:27:11,320
The survey team went looking
for Dark Matter in exactly
362
00:27:11,320 --> 00:27:13,560
the same way...
363
00:27:15,320 --> 00:27:18,840
..with 1,000 hours of observations
on the Hubble Space Telescope.
364
00:27:21,680 --> 00:27:24,480
By looking at distant galaxies
halfway across the universe,
365
00:27:24,480 --> 00:27:25,520
by looking at their shapes
366
00:27:25,520 --> 00:27:27,640
and the distorted images
that we see of those,
367
00:27:27,640 --> 00:27:31,720
we can work out what ripples there
are in space between them and us.
368
00:27:31,720 --> 00:27:36,080
And those ripples in space
are caused by the Dark Matter.
369
00:27:42,400 --> 00:27:45,840
The search zone was a thin column
of the universe,
370
00:27:45,840 --> 00:27:48,280
stretching eight billion
light years from Earth.
371
00:27:50,320 --> 00:27:51,960
The team were on the look-out
372
00:27:51,960 --> 00:27:54,600
for distortions
in the most distant galaxies.
373
00:27:56,400 --> 00:27:58,200
Whenever you see galaxies
374
00:27:58,200 --> 00:28:01,160
distorted into these strange
uncharacteristic shapes,
375
00:28:01,160 --> 00:28:04,000
you know that there must be
something in between them and you,
376
00:28:04,000 --> 00:28:07,080
something really massive,
and even if it's invisible,
377
00:28:07,080 --> 00:28:12,240
you can still map out where it is by
the way it warps that space time.
378
00:28:12,240 --> 00:28:18,120
The mapping technique revealed
a ghostly, hidden universe.
379
00:28:18,120 --> 00:28:24,040
The light from visible galaxies was
recast in new and beautiful forms.
380
00:28:25,240 --> 00:28:27,120
They've become these full rings,
381
00:28:27,120 --> 00:28:30,800
distorted just like what are known as
Einstein Rings,
382
00:28:30,800 --> 00:28:34,200
whenever there's a big lump
of Dark Matter in front of them.
383
00:28:34,200 --> 00:28:37,640
The lumps become contours on a map
of the invisible.
384
00:28:40,480 --> 00:28:43,520
They reveal Dark Matter
as the hidden iceberg
385
00:28:43,520 --> 00:28:46,160
beneath the surface
of the cosmic ocean.
386
00:28:49,040 --> 00:28:52,200
What we're finding out there
in the universe is really weird.
387
00:28:52,200 --> 00:28:55,320
It's equivalent to the idea that only
one out of six cities in America
388
00:28:55,320 --> 00:28:57,600
actually has any people living in it.
389
00:28:57,600 --> 00:29:00,080
The other five sixths
of the population
390
00:29:00,080 --> 00:29:02,240
are these invisible ghosts
that we just can't see.
391
00:29:03,880 --> 00:29:06,880
The survey has
transformed the map of the universe.
392
00:29:10,920 --> 00:29:13,200
It suggests that normal,
visible matter
393
00:29:13,200 --> 00:29:15,840
is just a fraction
of what's out there.
394
00:29:17,840 --> 00:29:22,480
In the search zone, Dark Matter
outweighs it by six to one.
395
00:29:24,640 --> 00:29:28,560
This is the stuff the universe
is really made of.
396
00:29:35,560 --> 00:29:39,400
For cosmologists, the road ahead
has become a lot less certain.
397
00:29:41,840 --> 00:29:46,080
Right now, we know the
universe is expanding.
398
00:29:46,080 --> 00:29:49,160
But given enough Dark Matter,
it could have a different,
399
00:29:49,160 --> 00:29:52,000
and very dark future.
400
00:29:53,200 --> 00:29:55,280
It's sensible to conclude,
401
00:29:55,280 --> 00:29:58,480
when we look at how that stuff
affects the shape of space,
402
00:29:58,480 --> 00:30:02,040
that the universe should be expanding
but that it should be slowing down.
403
00:30:04,600 --> 00:30:07,760
Dark Matter puts a very heavy
foot on the brakes.
404
00:30:09,040 --> 00:30:13,720
Because the more matter there is,
the more gravity there is.
405
00:30:17,200 --> 00:30:21,600
Gravity attracts. And so the cosmic
expansion should be slowed down
406
00:30:21,600 --> 00:30:22,840
by all that attraction.
407
00:30:26,720 --> 00:30:28,760
If there's enough Dark Matter,
408
00:30:28,760 --> 00:30:32,200
the universe will eventually stop
expanding altogether...
409
00:30:32,200 --> 00:30:34,480
..and go into reverse.
410
00:30:37,080 --> 00:30:39,520
Gravity will bring everything
back together,
411
00:30:39,520 --> 00:30:42,200
in a final, cataclysmic big crunch.
412
00:30:50,280 --> 00:30:53,720
The question is - when?
413
00:30:55,760 --> 00:30:58,200
The search for the answer began here
414
00:30:58,200 --> 00:31:01,440
on the Berkeley Campus of the
University of California.
415
00:31:05,320 --> 00:31:09,920
It's a distinctive outpost in the
landscape of science
416
00:31:09,920 --> 00:31:14,800
signposted with some
of its greatest names.
417
00:31:18,120 --> 00:31:21,760
There's even a car park
reserved for Nobel Laureates.
418
00:31:24,680 --> 00:31:29,880
Nine prize winners in a row
- with five in Physics alone.
419
00:31:32,560 --> 00:31:36,920
And it was here, in 1988,
that Saul Perlmutter set out
420
00:31:36,920 --> 00:31:40,000
to map the
deceleration of the universe.
421
00:31:52,080 --> 00:31:55,200
There's nothing you like more
than a really good mystery.
422
00:31:56,680 --> 00:31:59,360
I wondered if you could
actually measure,
423
00:31:59,360 --> 00:32:01,800
how much the universe
was slowing down.
424
00:32:01,800 --> 00:32:04,400
I thought it was a very exciting
possibility that you could,
425
00:32:04,400 --> 00:32:08,720
make a measurement, and find out
what the fate of the universe was.
426
00:32:08,720 --> 00:32:11,360
Saul was the leading light
427
00:32:11,360 --> 00:32:13,960
behind an international team of
physicists and astronomers.
428
00:32:18,040 --> 00:32:23,200
Under his guidance, they embarked on
a ten year voyage of exploration
429
00:32:23,200 --> 00:32:25,880
far across the observable universe.
430
00:32:34,200 --> 00:32:37,400
The key was to measure how fast the
universe was expanding
431
00:32:37,400 --> 00:32:42,840
in the past, compared to now. They
planned to map ancient galaxies -
432
00:32:42,840 --> 00:32:45,520
10.8 billion light years from Earth.
433
00:32:47,960 --> 00:32:51,200
But it would take a
whole decade to find and analyse
434
00:32:51,200 --> 00:32:52,800
what they were looking for.
435
00:32:54,000 --> 00:32:56,240
A candle.
436
00:32:58,000 --> 00:33:01,080
If you want to measure distances
across the universe
437
00:33:01,080 --> 00:33:06,720
you would like to be able to use an
object that's of known brightness.
438
00:33:06,720 --> 00:33:10,640
We call anything that we know the
brightness of a Standard Candle.
439
00:33:12,280 --> 00:33:14,920
A Standard Candle always has the
same brightness -
440
00:33:14,920 --> 00:33:19,800
so you can use it to
measure distance very precisely.
441
00:33:19,800 --> 00:33:21,000
The further away it is,
442
00:33:21,000 --> 00:33:24,880
the dimmer it will appear
in our telescopes.
443
00:33:24,880 --> 00:33:27,480
But candles are elusive objects.
444
00:33:27,480 --> 00:33:32,240
We hunt, for what astronomical
object could you possibly use,
445
00:33:32,240 --> 00:33:34,760
that will behave
in this very regular way,
446
00:33:34,760 --> 00:33:37,040
so that you can actually
compare the distances.
447
00:33:38,880 --> 00:33:41,600
The galaxies themselves are no good.
448
00:33:41,600 --> 00:33:45,120
They come in many
different shapes and sizes
449
00:33:45,120 --> 00:33:48,000
and at this distance, they're so dim
we can barely see them.
450
00:33:51,080 --> 00:33:54,240
We're talking about distances that
are even more vast than usual
451
00:33:54,240 --> 00:33:57,320
for astronomy. Now we need to look
at some of the most distant objects
452
00:33:57,320 --> 00:33:59,800
in the universe so these had to be
very bright objects.
453
00:33:59,800 --> 00:34:02,640
Saul had a very bright idea.
454
00:34:06,720 --> 00:34:10,000
He would find his way by the light
of a dying star.
455
00:34:11,760 --> 00:34:12,760
A supernova.
456
00:34:15,080 --> 00:34:17,160
When one of
these supernovas explode,
457
00:34:17,160 --> 00:34:21,520
that one star can be as bright
as the entire galaxy
458
00:34:21,520 --> 00:34:23,640
of a hundred billion other stars.
459
00:34:26,720 --> 00:34:30,160
So this is a remarkably
bright, single event.
460
00:34:32,080 --> 00:34:35,360
Saul had a special kind
of supernova in mind.
461
00:34:40,000 --> 00:34:41,640
A Type 1A is triggered
462
00:34:41,640 --> 00:34:44,920
when a dying star draws in mass
from its neighbour.
463
00:34:49,520 --> 00:34:51,880
Just at the point where
there's a critical mass,
464
00:34:51,880 --> 00:34:56,040
there will be a runaway
thermonuclear explosion.
465
00:34:59,840 --> 00:35:03,160
So that means that it's triggered at
the same mass every time.
466
00:35:06,080 --> 00:35:10,480
Same mass every time
means same brightness every time.
467
00:35:10,480 --> 00:35:14,440
They're perfect standard candles.
468
00:35:14,440 --> 00:35:16,160
But Saul had to find them first.
469
00:35:19,360 --> 00:35:22,480
If you could work
with anything else in the world
470
00:35:22,480 --> 00:35:24,680
besides a supernova
to do your research you would.
471
00:35:24,680 --> 00:35:26,920
They're just a real
pain in the neck to work with.
472
00:35:31,640 --> 00:35:34,440
They're rare, they're random
and they're rapid.
473
00:35:34,440 --> 00:35:38,480
A supernova only burns
brightly for three weeks.
474
00:35:38,480 --> 00:35:43,200
And in any given galaxy,
they explode without warning
475
00:35:43,200 --> 00:35:47,440
roughly once every 300 years.
476
00:35:47,440 --> 00:35:49,880
With those odds, you can't book
valuable time
477
00:35:49,880 --> 00:35:51,520
on the world's best telescopes.
478
00:35:53,520 --> 00:35:55,800
It makes a terrible proposal,
if you were to say that,
479
00:35:55,800 --> 00:35:58,240
"Sometime in the next
several hundred years,
480
00:35:58,240 --> 00:36:01,080
"a Type 1a supernova, might explode,
somewhere in this galaxy.
481
00:36:01,080 --> 00:36:04,320
"I would like the night
of March the 3rd, just in case."
482
00:36:06,360 --> 00:36:11,200
But Saul had a plan to get the odds
working in his favour.
483
00:36:11,200 --> 00:36:14,680
With billions of galaxies
in the observable universe -
484
00:36:14,680 --> 00:36:18,040
there are dozens of supernovae
every night.
485
00:36:21,760 --> 00:36:24,240
Saul's team spent six years
486
00:36:24,240 --> 00:36:26,880
perfecting a new system
for supernovae on demand.
487
00:36:28,960 --> 00:36:34,160
They took snapshots
of thousands of galaxies at once,
488
00:36:34,160 --> 00:36:37,200
then repeated them
two and a half weeks later.
489
00:36:37,200 --> 00:36:42,280
First you don't see a supernova.
490
00:36:42,280 --> 00:36:44,320
Now you do.
491
00:36:46,520 --> 00:36:48,720
That's very important,
that two and a half weeks,
492
00:36:48,720 --> 00:36:51,880
because that guarantees,
that everything you find,
that's brighter,
493
00:36:51,880 --> 00:36:54,840
on the second night than the first,
is on the way up.
494
00:37:01,760 --> 00:37:05,080
We can now guarantee
that there would not just be one
495
00:37:05,080 --> 00:37:08,280
Type 1A supernova,
but there would be a half dozen.
496
00:37:12,560 --> 00:37:15,880
Saul now knew exactly where to point
497
00:37:15,880 --> 00:37:18,200
one of the world's
most powerful telescopes -
498
00:37:18,200 --> 00:37:21,240
the Keck Observatory in Hawaii.
499
00:37:23,160 --> 00:37:29,240
He was finally ready to measure
the deceleration of the universe.
500
00:37:30,240 --> 00:37:32,440
But by late in 1997,
501
00:37:32,440 --> 00:37:35,120
the team was getting
some very weird results.
502
00:37:39,400 --> 00:37:44,240
The points were not showing up
where you would expect.
503
00:37:44,240 --> 00:37:46,480
This was exciting.
504
00:37:46,480 --> 00:37:49,520
The supernovae distance measurements
505
00:37:49,520 --> 00:37:52,800
didn't match
the predicted deceleration.
506
00:37:56,640 --> 00:37:58,360
We were then faced with
the question,
507
00:37:58,360 --> 00:38:00,640
"OK, what else
could be going wrong?"
508
00:38:00,640 --> 00:38:04,000
Saul and his team spent five more
anxious months,
509
00:38:04,000 --> 00:38:06,600
eliminating all possible
sources of error.
510
00:38:06,600 --> 00:38:10,680
But by January 1998 they were
finally ready to go public.
511
00:38:13,400 --> 00:38:15,360
The more we checked, the more we,
512
00:38:15,360 --> 00:38:19,160
fine tuned every little
step of the calibration,
513
00:38:19,160 --> 00:38:22,440
the more the weird result
didn't go away.
514
00:38:22,440 --> 00:38:24,880
The weird result
has reverberated through
515
00:38:24,880 --> 00:38:26,480
the world of science ever since.
516
00:38:28,640 --> 00:38:30,520
In January 2012,
517
00:38:30,520 --> 00:38:34,440
Saul Perlmutter won
the Nobel Prize for Physics
518
00:38:34,440 --> 00:38:37,720
and booked a parking space for life.
519
00:38:38,800 --> 00:38:44,040
At the end, we concluded that
actually, the universe really
isn't slowing down,
520
00:38:44,040 --> 00:38:46,120
it's actually speeding up
in its expansion.
521
00:38:46,120 --> 00:38:48,640
And that was a big shock.
522
00:38:51,760 --> 00:38:56,720
It's been described as one of the
biggest shocks in modern cosmology.
523
00:39:02,720 --> 00:39:05,360
This is a Runaway Universe
524
00:39:05,360 --> 00:39:08,160
and everyone's on board -
525
00:39:08,160 --> 00:39:10,320
whether we like it or not.
526
00:39:13,040 --> 00:39:15,440
We find out that the universe
is not just expanding,
527
00:39:15,440 --> 00:39:19,440
but that it's getting
faster and faster.
528
00:39:19,440 --> 00:39:21,960
The cosmological community,
when this result came out,
529
00:39:21,960 --> 00:39:23,560
was completely incredulous.
530
00:39:23,560 --> 00:39:25,640
I didn't believe it
when I first heard about it.
531
00:39:25,640 --> 00:39:29,200
I don't even think I paid very much
attention to it at the time.
532
00:39:29,200 --> 00:39:32,720
We know the universe
doesn't look like this.
533
00:39:32,720 --> 00:39:35,200
There had to be something wrong
with these observations.
534
00:39:35,200 --> 00:39:37,360
I thought they would go away,
I really did.
535
00:39:40,240 --> 00:39:41,840
Of course, I was wrong.
536
00:39:44,920 --> 00:39:48,000
It's sometimes really fun
to be wrong.
537
00:39:53,040 --> 00:39:56,080
Welcome to a very new picture
of the universe.
538
00:39:59,320 --> 00:40:02,440
But even the experts can hardly
believe it's real.
539
00:40:04,160 --> 00:40:10,160
The most famous force in physics
has met its match -
540
00:40:10,160 --> 00:40:14,080
because the entire universe
is defying gravity.
541
00:40:17,640 --> 00:40:19,800
This was saying that
there was something
542
00:40:19,800 --> 00:40:23,280
that fills the universe,
and causes an anti-gravity force.
543
00:40:23,280 --> 00:40:26,760
Something that was causing everything
to push everything else apart,
544
00:40:26,760 --> 00:40:28,920
and to make the universe
bigger and bigger
545
00:40:28,920 --> 00:40:30,320
in an accelerated way.
546
00:40:30,320 --> 00:40:32,920
Gravity acts as a brake -
547
00:40:32,920 --> 00:40:36,520
pulling back on the expansion
of the universe.
548
00:40:36,520 --> 00:40:39,960
But we now know there's another,
more mysterious force -
549
00:40:39,960 --> 00:40:44,080
with its foot on the gas.
550
00:40:44,080 --> 00:40:47,480
What's doing the pushing?
What's that force that's forcing
everything apart?
551
00:40:47,480 --> 00:40:49,760
Well, we don't know,
but we did work out what to call it.
552
00:40:49,760 --> 00:40:52,560
We have a name for it.
We call it dark energy.
553
00:40:54,200 --> 00:40:57,400
Cosmologists don't know
what dark energy is.
554
00:40:59,080 --> 00:41:02,480
They only know what it does.
555
00:41:02,480 --> 00:41:06,360
Where gravity pulls -
556
00:41:06,360 --> 00:41:09,800
dark energy pushes.
557
00:41:11,160 --> 00:41:13,680
You don't see this stuff.
558
00:41:13,680 --> 00:41:15,720
You don't see it doing anything,
directly.
559
00:41:15,720 --> 00:41:18,240
Basically,
it's sort of this one hit wonder,
560
00:41:18,240 --> 00:41:21,200
that just does one thing,
it causes an anti-gravity force.
561
00:41:21,200 --> 00:41:25,040
We don't have any other
handle on it.
562
00:41:25,040 --> 00:41:28,280
Dark energy is dark matter's
dark adversary.
563
00:41:30,120 --> 00:41:32,680
A shadow on the entire universe.
564
00:41:36,400 --> 00:41:37,920
There's dark energy in the galaxy.
565
00:41:37,920 --> 00:41:39,560
There's dark energy, here on Earth.
566
00:41:39,560 --> 00:41:43,160
There's dark energy passing
through us right now.
We're filled with this dark energy.
567
00:41:43,160 --> 00:41:45,160
We don't see it - we don't feel it.
568
00:41:45,160 --> 00:41:47,000
But it's everywhere.
569
00:41:47,000 --> 00:41:50,640
It's kind of just a uniform
colouration to our map.
570
00:41:50,640 --> 00:41:53,880
73% of the universe is dark energy,
571
00:41:53,880 --> 00:41:55,440
but you'd never know.
572
00:41:56,960 --> 00:42:00,040
In everyday life,
this stuff is just hard to detect.
573
00:42:00,040 --> 00:42:02,240
Now, it's true
that between my two fingers,
574
00:42:02,240 --> 00:42:04,120
there's an anti-gravity force,
right now.
575
00:42:04,120 --> 00:42:06,680
But that anti-gravity force
is so incredibly minuscule,
576
00:42:06,680 --> 00:42:08,160
that I'll never ever notice it.
577
00:42:08,160 --> 00:42:10,520
It's only when you get
to really large scales,
578
00:42:10,520 --> 00:42:13,160
that you really see
the affect of this stuff.
579
00:42:13,160 --> 00:42:16,440
If I could move my fingers,
all the way across the universe,
580
00:42:16,440 --> 00:42:19,800
then they'd feel this tremendous push
apart, due to this dark energy.
581
00:42:23,040 --> 00:42:25,560
In the really big scheme of things,
582
00:42:25,560 --> 00:42:27,600
dark matter is fighting
a losing battle...
583
00:42:29,880 --> 00:42:32,880
..because there's only
so much of it to go round.
584
00:42:36,120 --> 00:42:37,800
If you add more space,
585
00:42:37,800 --> 00:42:42,000
if you give more place for those
little pieces of matter to be,
586
00:42:42,000 --> 00:42:44,480
then, the density of them goes down.
587
00:42:44,480 --> 00:42:46,920
You just see less of it -
it gets diluted.
588
00:42:46,920 --> 00:42:50,520
As the universe expands,
dark matter thins out
589
00:42:50,520 --> 00:42:54,360
until it can no longer compete
with dark energy.
590
00:42:56,040 --> 00:42:58,600
The really crucial thing about how
this dark energy behaves,
591
00:42:58,600 --> 00:43:00,160
is that it doesn't dilute.
592
00:43:00,160 --> 00:43:02,480
When the universe doubles in size,
593
00:43:02,480 --> 00:43:05,440
you've got twice as much
dark energy.
594
00:43:05,440 --> 00:43:09,440
You make it four times as big,
you've just got four times as much
dark energy.
595
00:43:09,440 --> 00:43:11,480
Once you get to this
cosmological scale,
596
00:43:11,480 --> 00:43:14,520
the biggest possible scale,
it becomes the biggest game in town.
597
00:43:14,520 --> 00:43:17,760
It becomes the prime player.
598
00:43:17,760 --> 00:43:20,800
Dark energy is on the map.
599
00:43:22,160 --> 00:43:24,240
But cosmologists can't explain it.
600
00:43:26,560 --> 00:43:29,280
Depressing, or exciting?
I think it's exciting.
601
00:43:29,280 --> 00:43:32,200
As a map maker,
this is a strange thing.
602
00:43:32,200 --> 00:43:36,880
We go out, we make this map,
we discover this land,
603
00:43:36,880 --> 00:43:39,520
we've mapped it out,
and we still don't know what it is.
604
00:43:39,520 --> 00:43:42,160
I love that.
605
00:43:50,600 --> 00:43:54,160
The entire observable universe
is saturated in dark energy.
606
00:43:57,960 --> 00:44:03,520
But there's one final set of clues
to be found - on its furthest edge.
607
00:44:06,880 --> 00:44:10,800
And it may contain the secrets
to the universe beyond.
608
00:44:20,800 --> 00:44:25,480
We're heading off the map
into impossible territory.
609
00:44:28,600 --> 00:44:31,880
The edge of the observable universe
610
00:44:31,880 --> 00:44:35,720
is the furthest horizon
our telescopes can see.
611
00:44:35,720 --> 00:44:40,680
But for cosmologists like
Sean Carroll, that's not enough.
612
00:44:40,680 --> 00:44:45,720
He wants to know
the size of the whole universe.
613
00:44:45,720 --> 00:44:51,600
I definitely think it's OK to think
about parts of the universe that we
can't observe and can never observe.
614
00:44:51,600 --> 00:44:54,680
We've done a very good
job at understanding
615
00:44:54,680 --> 00:44:57,120
what the universe looks like
in that visible portion.
616
00:44:57,120 --> 00:44:59,400
So now when our imaginations roam,
617
00:44:59,400 --> 00:45:02,120
they often sneak outside the visible
portion to ask what might
618
00:45:02,120 --> 00:45:04,880
the universe look like
beyond our visible horizon.
619
00:45:04,880 --> 00:45:07,640
The universe that we can't see -
620
00:45:07,640 --> 00:45:09,880
that's the playground
for theorists now.
621
00:45:12,320 --> 00:45:15,000
But if we can't see the rest
of the universe,
622
00:45:15,000 --> 00:45:17,000
how can we figure out how big it is?
623
00:45:18,840 --> 00:45:22,160
For Janna Levin, it's a similar task
to working out the shape
624
00:45:22,160 --> 00:45:25,120
and size of the earth.
625
00:45:25,120 --> 00:45:27,160
But there's a catch.
626
00:45:29,000 --> 00:45:33,400
We know we could step far from
the Earth, as an astronaut has.
627
00:45:33,400 --> 00:45:35,160
We can look down on it
628
00:45:35,160 --> 00:45:39,920
and see from the outside that it was
a sphere and it was curved.
629
00:45:39,920 --> 00:45:41,880
You can't step
outside of the universe.
630
00:45:41,880 --> 00:45:46,720
You have to do
everything from inside of space.
631
00:45:46,720 --> 00:45:49,560
Without leaving the earth,
how do you know it's round,
632
00:45:49,560 --> 00:45:52,160
and therefore has finite size?
633
00:45:53,560 --> 00:45:55,800
It could be completely flat,
634
00:45:55,800 --> 00:45:58,920
and stretch to infinity
in all directions.
635
00:46:01,080 --> 00:46:03,960
One way is to use a simple
piece of mathematics.
636
00:46:09,040 --> 00:46:11,600
All you have to do
is draw a triangle.
637
00:46:19,520 --> 00:46:22,800
If you're drawing a small enough
triangle on the beach,
638
00:46:22,800 --> 00:46:25,080
you won't notice
the curvature of the earth.
639
00:46:25,080 --> 00:46:29,560
It will look like a normal triangle,
you'll be able to draw the lines
pretty straight
640
00:46:29,560 --> 00:46:32,360
and the interior angles will look
like they add up to 180 degrees,
641
00:46:32,360 --> 00:46:35,000
it will look like the triangle you
draw on a flat sheet of paper.
642
00:46:36,440 --> 00:46:38,880
But this isn't a normal triangle,
643
00:46:38,880 --> 00:46:43,000
because the earth's surface
is curved.
644
00:46:43,000 --> 00:46:45,160
It's just so subtle,
645
00:46:45,160 --> 00:46:47,480
that the sides of the triangles
still look straight.
646
00:46:47,480 --> 00:46:51,800
It would probably be a challenge on
the beach to draw it big enough
647
00:46:51,800 --> 00:46:55,760
that you would be able to
notice the curvature of the earth.
648
00:46:55,760 --> 00:46:58,160
The key is to make the curvature
more obvious -
649
00:46:58,160 --> 00:47:00,800
by drawing the biggest triangle
you can.
650
00:47:04,440 --> 00:47:08,520
If I draw a triangle big enough
that it comes from the North Pole
651
00:47:08,520 --> 00:47:12,160
and it wraps all the way
around North America,
652
00:47:12,160 --> 00:47:17,280
now it's very obvious that those
angles are bigger than 180 degrees
653
00:47:17,280 --> 00:47:20,360
and that the sides of the triangle
are not straight lines.
654
00:47:22,760 --> 00:47:26,200
So, we can show the earth is curved
655
00:47:26,200 --> 00:47:29,920
and therefore has finite size
without leaving it.
656
00:47:29,920 --> 00:47:33,400
And we can find out the shape
and size of the universe
657
00:47:33,400 --> 00:47:36,880
in exactly the same way -
658
00:47:36,880 --> 00:47:40,840
by looking for triangles of light.
659
00:47:43,280 --> 00:47:46,120
Light will travel in a straight line
if the space is flat,
660
00:47:46,120 --> 00:47:48,720
and light itself will travel
in an arc if the space is curved.
661
00:47:51,440 --> 00:47:53,760
These curves are going to be
so subtle,
662
00:47:53,760 --> 00:47:55,880
more subtle than
the curvature of the earth.
663
00:47:57,680 --> 00:47:59,920
We really have to look back
664
00:47:59,920 --> 00:48:01,680
as far as we possibly can.
665
00:48:01,680 --> 00:48:04,400
And that means the oldest relic
we have in the universe.
666
00:48:04,400 --> 00:48:06,240
So that means looking at things
667
00:48:06,240 --> 00:48:08,640
like the light left
over from the Big Bang.
668
00:48:19,400 --> 00:48:22,680
The early universe was a hot,
dense fireball.
669
00:48:25,120 --> 00:48:28,160
When it cooled,
a pattern of light emerged
670
00:48:28,160 --> 00:48:31,640
at what is now the edge
of the observable universe.
671
00:48:31,640 --> 00:48:35,320
This is the cosmic
microwave background.
672
00:48:41,120 --> 00:48:44,560
The CMB was discovered in the 1960s.
673
00:48:44,560 --> 00:48:47,520
But throughout his career,
Sean Carroll
674
00:48:47,520 --> 00:48:52,280
has been able to explore it
in greater and greater detail -
675
00:48:52,280 --> 00:48:54,680
waiting for triangles to emerge.
676
00:48:58,800 --> 00:49:00,640
It takes good technology to do it,
677
00:49:00,640 --> 00:49:03,280
you need better and better
receivers,
678
00:49:03,280 --> 00:49:05,640
less and less noise
in your detector,
679
00:49:05,640 --> 00:49:08,160
and ultimately you need satellites
680
00:49:08,160 --> 00:49:10,520
to get a really good 360 degree view
681
00:49:10,520 --> 00:49:13,520
of the whole
cosmic microwave background.
682
00:49:18,440 --> 00:49:22,080
It was NASA's WMAP mission in 2003
683
00:49:22,080 --> 00:49:25,640
that brought the most vital contours
into sharp focus.
684
00:49:29,840 --> 00:49:32,560
WMAP for the first time
had that resolution
685
00:49:32,560 --> 00:49:36,000
so when WMAP came out, we could
really use those features
686
00:49:36,000 --> 00:49:38,640
to make a big triangle and measure
the geometry of space.
687
00:49:40,040 --> 00:49:43,680
Continents begin to appear,
smaller islands,
688
00:49:43,680 --> 00:49:47,680
you get a finer resolution
of the coastlines and so forth.
689
00:49:47,680 --> 00:49:51,240
The islands are miniscule
temperature variations
690
00:49:51,240 --> 00:49:55,720
in the early universe -
less than 100,000th of a degree...
691
00:49:58,640 --> 00:50:02,200
..a distinctive feature
for making triangles.
692
00:50:11,960 --> 00:50:17,240
These splotches we see
in the microwave background
appear at all different sizes
693
00:50:17,240 --> 00:50:19,520
but there is a best size
for them to be,
694
00:50:19,520 --> 00:50:24,320
there's a size at which the
fluctuations are the strongest.
695
00:50:24,320 --> 00:50:28,200
We know how big they are,
we know how far away they are,
696
00:50:28,200 --> 00:50:32,080
so between us and the size
of a feature in the CMB,
697
00:50:32,080 --> 00:50:35,920
we can measure a triangle and use
that to infer the geometry of space.
698
00:50:39,400 --> 00:50:43,120
The earth, plus the opposite
sides of the island,
699
00:50:43,120 --> 00:50:47,280
form the three points of a very
long, thin triangle -
700
00:50:47,280 --> 00:50:51,520
The key to measuring whether
the universe is flat or curved.
701
00:50:53,640 --> 00:50:56,040
If the universe were
positively curved,
702
00:50:56,040 --> 00:50:59,440
if the angles inside the triangle
added up to greater
703
00:50:59,440 --> 00:51:02,720
than 180 degrees,
then it would be finite in size.
704
00:51:02,720 --> 00:51:04,960
If the spatial geometry is flat,
705
00:51:04,960 --> 00:51:08,560
if the angles inside the triangle
add up to 180,
706
00:51:08,560 --> 00:51:10,640
then it could go on for ever.
707
00:51:13,720 --> 00:51:20,000
The result is one of the greatest
triumphs of modern cosmology.
708
00:51:20,000 --> 00:51:21,840
A miracle of precision map making
709
00:51:21,840 --> 00:51:26,680
that measures the angles of the
triangle to the third decimal place.
710
00:51:28,840 --> 00:51:33,640
And it says that the
universe is infinite.
711
00:51:33,640 --> 00:51:36,800
The answer is that Euclid was right,
712
00:51:36,800 --> 00:51:39,160
space seems to us to be flat
as far as we can measure it.
713
00:51:42,520 --> 00:51:44,920
That means that the simplest
picture of the universe,
714
00:51:44,920 --> 00:51:46,400
is a universe that's infinite.
715
00:51:46,400 --> 00:51:49,280
We really could
live in a universe where,
716
00:51:49,280 --> 00:51:53,720
there's galaxy after galaxy
after galaxy, in every direction.
717
00:51:53,720 --> 00:51:56,360
Up, down, sideways.
And, it never stops.
718
00:51:56,360 --> 00:51:59,200
Cosmologists have found a way
719
00:51:59,200 --> 00:52:03,000
to picture the universe
in its entirety -
720
00:52:03,000 --> 00:52:07,320
confirmation of the tremendous
power of making maps.
721
00:52:07,320 --> 00:52:09,960
It will never cease to amaze me -
722
00:52:09,960 --> 00:52:13,160
we human beings here on this tiny
little rock are able to reach out
723
00:52:13,160 --> 00:52:16,480
with our instruments and our brains
724
00:52:16,480 --> 00:52:18,720
to understand the whole shebang.
725
00:52:18,720 --> 00:52:23,160
And if an infinite universe
isn't big enough for you -
726
00:52:23,160 --> 00:52:26,960
then Saul Perlmutter has proved
it's still growing.
727
00:52:29,040 --> 00:52:31,240
All the distances are getting
bigger, every day.
728
00:52:31,240 --> 00:52:33,880
So, it's still infinite,
all the same galaxies are there,
729
00:52:33,880 --> 00:52:35,760
it's just that we have
pumped more space
730
00:52:35,760 --> 00:52:38,000
between every point
in this infinite universe.
731
00:52:39,960 --> 00:52:41,640
That's really mind boggling.
732
00:52:44,920 --> 00:52:49,120
But even this isn't
the end of the story.
733
00:52:56,680 --> 00:53:01,160
There may be one final,
bizarre twist in the road.
734
00:53:05,800 --> 00:53:10,680
Because Anthony Aguirre thinks
our universe may not be alone.
735
00:53:16,920 --> 00:53:20,160
Sometimes when I'm headed down
the highway and I'm driving,
736
00:53:20,160 --> 00:53:21,880
you know, my wife will say,
737
00:53:21,880 --> 00:53:24,320
"Anthony, you're going 40
on the highway."
738
00:53:24,320 --> 00:53:27,360
And then she knows that I'm thinking
about other universes.
739
00:53:29,360 --> 00:53:32,160
He thinks there may be
other universes
740
00:53:32,160 --> 00:53:35,400
because of the process
that created our own.
741
00:53:35,400 --> 00:53:39,240
It's called inflation.
742
00:53:39,240 --> 00:53:41,800
It describes an exponential
expansion
743
00:53:41,800 --> 00:53:46,040
in the moments after the Big Bang,
744
00:53:46,040 --> 00:53:51,320
at a speed the universe would
never repeat again.
745
00:53:52,920 --> 00:53:56,600
Inflation has been a very successful
theory in predicting
746
00:53:56,600 --> 00:53:58,960
observed properties of our universe
747
00:53:58,960 --> 00:54:01,920
and how our observed universe
came into being.
748
00:54:04,720 --> 00:54:07,960
Inflation may have started
out as a mathematical theory...
749
00:54:12,240 --> 00:54:14,720
..but it has gained acceptance
after successful testing
750
00:54:14,720 --> 00:54:19,120
against the evidence from the
cosmic microwave background.
751
00:54:19,120 --> 00:54:25,000
I was amazed when I saw the results
come in from those satellites
752
00:54:25,000 --> 00:54:26,920
that reproduced all the bumps
and wiggles
753
00:54:26,920 --> 00:54:29,720
and all the detailed properties
of that microwave background
754
00:54:29,720 --> 00:54:32,280
that inflation had predicted.
755
00:54:32,280 --> 00:54:39,080
Inflation explains how the
observable universe developed.
756
00:54:39,080 --> 00:54:42,080
It was doubling in size over and
over again in a tiny fraction
of a second,
757
00:54:42,080 --> 00:54:45,560
going from something like a billionth
of the size of a proton
758
00:54:45,560 --> 00:54:49,320
to something maybe the size of a
bubble, a soap bubble.
759
00:54:53,560 --> 00:54:57,160
But inflation didn't stop
with our own universe.
760
00:54:57,160 --> 00:55:01,480
Anthony believes it may have
happened over and over again.
761
00:55:04,840 --> 00:55:07,080
This is really a side effect.
762
00:55:07,080 --> 00:55:10,360
It's a huge side effect,
it's an amazing side effect,
763
00:55:10,360 --> 00:55:15,800
but it's a side effect of something
we invented already for a different
purpose.
764
00:55:17,800 --> 00:55:22,120
It's a process called
eternal inflation.
765
00:55:26,480 --> 00:55:29,240
There could be as many
as we can imagine.
766
00:55:31,880 --> 00:55:36,320
Anthony's vision - of an infinite
number of infinite universes -
767
00:55:36,320 --> 00:55:38,160
may sound far-fetched.
768
00:55:40,280 --> 00:55:44,360
But the search is on to find
evidence to support it.
769
00:55:46,720 --> 00:55:49,720
Evidence from the oldest
part of our map.
770
00:55:52,000 --> 00:55:55,360
Every once in a while we could have
sort of a cosmic collision
771
00:55:55,360 --> 00:55:56,520
with another bubble.
772
00:56:01,120 --> 00:56:04,160
It would leave an impact, it would
leave a bruise,
773
00:56:04,160 --> 00:56:05,240
a disc in the sky
774
00:56:05,240 --> 00:56:09,240
on the microwave background radiation
that we could look for.
775
00:56:12,080 --> 00:56:14,920
Anthony and his colleagues
have simulated
776
00:56:14,920 --> 00:56:18,760
what a collision of universes
would look like.
777
00:56:20,960 --> 00:56:27,360
A dark bruise, superimposed
on the cosmic microwave background.
778
00:56:27,360 --> 00:56:30,880
He doesn't yet have enough
data to test it,
779
00:56:30,880 --> 00:56:35,040
but it's a tantalising
glimpse of what the map could reveal
780
00:56:35,040 --> 00:56:37,720
with the next
generation of satellites.
781
00:56:40,080 --> 00:56:43,800
In principle I think this scenario
with all these bubbles
782
00:56:43,800 --> 00:56:47,240
is testable, we can actually go out
and look for them.
783
00:56:47,240 --> 00:56:52,720
This may be the ultimate
map of the universe.
784
00:56:57,360 --> 00:57:00,440
We're talking about understanding
and testing and theorising
785
00:57:00,440 --> 00:57:04,880
in a scientific way about an
infinite number of universes.
786
00:57:04,880 --> 00:57:08,280
It's simultaneously so mind-boggling
787
00:57:08,280 --> 00:57:10,600
and yet it's still rigorous science -
788
00:57:10,600 --> 00:57:14,720
we can do mathematics, we can do
experiments, we can really test it.
789
00:57:21,360 --> 00:57:23,800
Some day we'll understand
the universe so well
790
00:57:23,800 --> 00:57:27,160
that we can literally take that map,
put it on a little compact disc
791
00:57:27,160 --> 00:57:29,200
and put it in our pockets
and take it home.
792
00:57:43,720 --> 00:57:49,160
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