The E

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We know the universe had a beginning.

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A moment 13.8 billion years ago
when it sprang into life...

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..creating the vast cosmos we see today.

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Now we've discovered its origin,

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we're faced with another
equally fundamental question.

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If the universe has a
beginning, if it was born,

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does that then mean it'll eventually die?

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Or will it just keep on
going for ever, eternal?

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You see, for us, as all-too-mortal
humans, the ultimate fate

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of the universe is a question
that's hard-wired into our psyche.

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Trying to answer it has
driven an astonishing

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revolution in our
understanding of the cosmos.

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Yet in recent years, it's
also revealed a universe

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that's far stranger than we ever imagined.

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And led to one of the most shocking
moments in scientific history.

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It's the latest twist in a tale
stretching back over 100 years.

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In that time, key experiments
and crucial discoveries...

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And there it is.

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Exactly, exactly where Hoyle predicted.

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..have brought us closer
than anyone thought possible

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to finally knowing the
ultimate fate of the universe.

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The sheer scale of the
universe is truly staggering.

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How on earth can you predict the
future of something so vast...

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..so complex...

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..so much bigger than we are?

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Since we first started
grappling with this question,

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the answer has hinged on one simple idea.

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If we could chart, observe and
understand how the universe has changed,

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how it has evolved to the
present moment from its very

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ancient beginnings, then we should
be able to extrapolate forward

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and predict how it will
evolve in the future.

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Unfortunately, the slight
flaw in that plan is that

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the universe operates on timescales
of millions and billions of years.

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We don't.

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To understand the workings of the universe,

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we need to see beyond our
limited human lifespan.

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And in this case, it
turned out the sheer scale

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of the universe could be
turned to our advantage.

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The universe is so vast,

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light from some of the objects
we see in the night sky

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has taken millions, even billions
of years to reach the Earth.

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When we look up, we're looking
back in time at a record

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of the deep history of the universe.

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The problem is, we only have
a snapshot, a single complex

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and confusing picture of all this history.

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It's like taking all the words
in a novel, jumbling them up

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and sticking them on a single page.

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The key is to try and unpick this
story, to learn how to read it,

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to recognise and understand
what's going on.

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Astronomers realised that stars
could help unlock that history.

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If scientists could work
out how stars change,

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how they evolve in time,

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they could begin to understand the
bigger story of how the universe

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was changing, the first clues
to what the future might hold.

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But it would take until the
middle of the 20th century

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to find the answer.

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Unlocking the secrets
of the stars would take

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a moment of brilliance
from this man, Fred Hoyle.

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Hoyle was a brilliant
mathematician and physicist,

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one of the greatest of his day.

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He was creative, coming
up with bold theories.

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Above all, he loved a problem,

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some thorny issue he could
make his mark by solving.

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And in the late 1940s, he
found one of the biggest.

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Hoyle wanted to know where
the elements came from.

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The early universe was mostly just
a sea of hydrogen and helium.

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The simplest and lightest elements.

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But we know that changed.

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Look around us now. This is
no simple world we live in.

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We're surrounded by complexity,
built from complex, heavy elements,

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like the oxygen I breathe
and the iron in our blood.

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And of course, carbon, in the trees
and in every cell in my body.

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No-one knew how to bridge
the gap, how the universe

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went from that very simple
beginning to all of this.

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This was the problem Hoyle seized on.

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Hoyle knew nuclear fusion
must hold the answer.

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In nuclear fusion,

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lighter elements are fused together
to make more complex ones.

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It was already known to
happen in the heart of stars,

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where hydrogen fused together to
form the more complex helium.

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Hoyle wondered how to go
further, how the helium nuclei

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might fuse to make heavier elements.

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It's a remarkably simple idea.
Here's our helium nucleus.

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If you could stick together
two helium nuclei,

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you'd make beryllium, a
heavier, more complex nucleus.

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Then, add a third helium
nucleus and you get carbon.

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From there, you can carry on building
up heavier and heavier elements.

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It sounds like the perfect solution.

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But there was a very good reason
why the formation of carbon -

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hence all other elements - was
still such a big mystery.

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The problem was, that the physics
of this process just didn't work.

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Calculations showed that three helium
nuclei wouldn't stick together.

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The carbon nucleus they formed was
unstable and simply fell apart.

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If it broke down at carbon,

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then there was no chance of making
any other heavier elements.

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It was like hitting a
roadblock, every time.

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In typical bold and bullish fashion,

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Hoyle got around the problem by
predicting a brand-new state of carbon.

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Hoyle took an intuitive leap.

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He decided that if three helium nuclei
did come together inside a star,

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they could form carbon with a
bit more energy than normal.

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In this special state, it could stay intact
for just long enough to become stable.

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In that way, stars could make carbon
and the roadblock was removed.

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If he was right, then Hoyle
had solved the mystery.

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The elements were built
in the heart of stars.

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But there was more at stake than that.

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Hoyle realised his theory could
reveal how stars changed

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through their lives.

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And as the universe we see is built
of stars, that would make it

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a powerful tool for predicting
the future of the universe.

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Astronomers were already grouping
stars based on their size,

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colour and brightness...

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..plotting them on a chart that was known
as the Hertzsprung-Russell diagram.

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So here we had the diagram
that they created.

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Along here is size and brightness,
running from very large,

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very bright stars, all the way
down to smaller, dimmer stars.

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And along this direction
is colour and temperature.

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Very hot blue stars, all the
way down to cooler red stars.

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Most regular-size stars
fell into a long diagonal

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through the middle of the diagram,

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with a group of giant, bright stars above

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and small, dwarf stars below.

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Astronomers could see the patterns, but
weren't able to unlock what they meant.

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Until Hoyle and his theory presented

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a radical new way of
looking at the diagram.

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One that would reveal the
life cycle of a star.

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Let's consider our own sun.

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Now, at the moment, it's sitting
here in the middle of the diagram,

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happily burning hydrogen,
turning it into helium.

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But if Hoyle was right, when
it's run out of its hydrogen,

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it'll start fusing helium
to make heavier elements.

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Now, at this point, a dramatic
transformation takes place.

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Because rather than moving down
the diagram in this direction,

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it expands to many times its size

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and jumps across here to
live amongst the red giants.

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At this phase, it starts burning
helium to make much heavier

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elements until it finally
begins to produce carbon.

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Now, at that point, when it's
run out of its nuclear fuel,

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it undergoes its final transformation.

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It sheds most of its outer layer and
leaves behind a tiny white cinder,

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living here amongst the white dwarfs.

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All stars follow their own
route around the diagram.

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Hoyle's theory provided the understanding
to track each star's evolution,

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driven by the sudden ignition of a
new phase of elemental formation.

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Here was the answer to the
mystery of the heavy elements.

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The key to the life cycle of the stars.

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And a window onto the
future of the universe.

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All thanks to Hoyle's new state of carbon.

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There was just one slight problem.

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No-one had ever seen or detected
Hoyle's special form of carbon,

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not in a telltale spectra from
stars, not anywhere on earth,

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not even in a laboratory experiment.

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As far as anyone could
tell, it didn't exist.

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And without this special form of carbon,

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the whole theory would come crashing down.

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What happened next is a
testament to Hoyle's brilliance

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and almost pig-headed self belief.

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In the 1950s, Hoyle joined the
California Institute of Technology -

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Caltech - who had one of the
few particle accelerators

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in existence at the time,
similar to this one.

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Hoyle wanted to use the accelerator to try

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and make his high-energy carbon.

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They were not so keen.

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Here was an unknown Brit trying
to take over their new machine

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in order to look for something
he'd effectively made up.

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Like Hoyle, I'm a theorist.

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Experimental physics is
a very different world

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and it's a different area of expertise.

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But Hoyle had the confidence, the
daring, to stride into the lab

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and, as the director of the facility said,

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without a buy-or-leave, demand
that they give up the research

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they were doing in favour of carrying
out a complicated experiment

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to look for something that no-one even
believed existed in the first place.

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I'm pretty sure I wouldn't
have had the guts to do that.

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Hoyle kept at them, arguing it would
be a crucial and famous discovery.

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Finally, they gave in.

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The search was on.

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Today, I'm recreating their experiment.

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The plan was to bombard a target
element with a particle beam

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to see if they could create
that state of carbon.

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Well, I have with me my own
experimental colleagues,

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Zahne and Robin, to help me out.

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Our target will be held in the
centre of this reaction chamber.

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Now, what they were looking for
was a very specific signal

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that would show up in their detectors.

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If that state of carbon existed,
then Hoyle predicted that it would

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show up as a spike in the energy
at 7.7 million electron volts -

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the fingerprints of this
special state of carbon.

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We'll be looking for the
same spike in energy.

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Time to seal the chamber...

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..close the radiation doors...

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..and see for ourselves what happened.

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Right, this is the control panel.

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And they've let me in - a
theorist - to get it all running.

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So the first thing I do
is fire up the beam.

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Then to aim the beam at the target.

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Charged particles are now
slamming into the target.

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Back in the 1950s, this was
Hoyle's moment of truth.

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Now data will start coming
in and the important display

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to look at is over here.

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Now, if Hoyle was right, they'd see
his excited state of carbon at this

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energy here. They would expect to see
a spike in energy at that point.

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And there it is.

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Exactly - exactly - where Hoyle predicted.

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Now, when this experiment was
carried out some 60 years ago,

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they were flabbergasted to
see that Hoyle was right.

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It's quite incredible to think that he
just worked on a theoretical hunch,

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convinced his experimental
colleagues to do the experiment,

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and he was right.

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He was also right about the fame.

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The director of the
laboratory went on to receive

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the Nobel Prize for the discovery.

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Hoyle, however, received nothing.

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They published their findings
in one of the most famous

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and heavily referenced papers in science.

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On the front cover of the paper,

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the authors put a very apt quote
from Shakespeare's King Lear.

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"It is the stars, the stars above
us, govern our conditions."

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It was the confirmation of this
excited state of carbon that

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proved that it's inside stars
that all the elements that make

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up the world around us, including
ourselves, are actually forged.

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And with that discovery, we gained real
insight into the life cycle of stars.

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We could begin to understand how
the universe changed over time,

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both now and into the future.

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Here was the foundation for
extrapolating into the future.

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And it made one clear prediction
for the end of the universe.

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It was hydrogen and helium
that first formed stars,

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and it was these two elements
that were consumed in stars

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as they aged, creating all the
heavier elements in the process.

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The logical conclusion was disturbing.

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After an almost unimaginable
length of time,

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stars would use up all the
hydrogen and helium in existence.

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No new stars could form,

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and existing stars would eventually
run out of their fuel and die.

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The universe would go dark.

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For everything that's important
to you and me, the light and life

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created by the stars, the universe
would eventually come to an end.

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00:17:55,400 --> 00:17:57,160
But there was another option.

239
00:17:57,160 --> 00:17:59,720
One that promised a very different fate...

240
00:18:00,920 --> 00:18:04,560
..and would play out long before
the stars ran out of fuel.

241
00:18:05,880 --> 00:18:09,800
A fate that involved a fundamental
force of the universe.

242
00:18:11,200 --> 00:18:13,160
Gravity.

243
00:18:16,840 --> 00:18:20,000
The potential for gravity
to define the ultimate fate

244
00:18:20,000 --> 00:18:25,200
of the universe was first spotted
by one of science's unsung heroes.

245
00:18:25,200 --> 00:18:27,400
Vesto Slipher.

246
00:18:27,400 --> 00:18:30,680
Little-known, his pioneering
expert measurements

247
00:18:30,680 --> 00:18:33,440
would transform our
understanding of the universe.

248
00:18:35,480 --> 00:18:40,040
In the early 1900s, astronomy
was entering its golden age,

249
00:18:40,040 --> 00:18:43,960
with evermore powerful
telescopes trained on the skies.

250
00:18:45,680 --> 00:18:48,880
One of the biggest targets
of the time was the nebulae.

251
00:18:54,560 --> 00:18:57,080
Nebulae were patches and swirls of light

252
00:18:57,080 --> 00:18:59,880
that could be seen in between the stars,

253
00:18:59,880 --> 00:19:03,320
and not much was known about
these mysterious objects,

254
00:19:03,320 --> 00:19:07,680
so astronomers were scrambling to find
out as much about them as possible.

255
00:19:07,680 --> 00:19:11,200
Slipher was interested in one
particular aspect of the nebulae -

256
00:19:11,200 --> 00:19:12,680
their motion.

257
00:19:12,680 --> 00:19:17,080
And for his target, he chose the
most famous one of all, Andromeda.

258
00:19:22,760 --> 00:19:27,560
Slipher wanted to be the first to measure
how quickly a nebula was moving.

259
00:19:29,240 --> 00:19:33,040
The problem was, his was not
the best telescope out there.

260
00:19:33,040 --> 00:19:34,560
Not by a long chalk.

261
00:19:36,120 --> 00:19:39,920
But Slipher did have one big
advantage over his competitors.

262
00:19:42,600 --> 00:19:44,560
He was a superb astronomer.

263
00:19:47,040 --> 00:19:51,120
This telescope is actually
the same size as Slipher's.

264
00:19:51,120 --> 00:19:53,240
It has a 24-inch mirror.

265
00:19:54,400 --> 00:19:58,880
But Slipher would have loved to have
got his hands on something like this.

266
00:19:58,880 --> 00:20:01,920
You see, what he needed
was to get a spectrum.

267
00:20:01,920 --> 00:20:05,080
Now, that involves splitting
the light from the nebulae

268
00:20:05,080 --> 00:20:09,120
into its different wavelengths, the
different colours that it's made of.

269
00:20:09,120 --> 00:20:12,880
Now, he'd have used something like
this - it's a diffraction grating.

270
00:20:12,880 --> 00:20:16,680
I can see it reflects
this light and gives me

271
00:20:16,680 --> 00:20:19,960
all the different colours of the rainbow.

272
00:20:19,960 --> 00:20:24,560
What worried Slipher was that he needed
to collect as much light as possible

273
00:20:24,560 --> 00:20:29,720
to give him a usable spectrum, and
nebulae are exceptionally faint.

274
00:20:30,720 --> 00:20:35,080
He feared that getting enough
light from his telescope would

275
00:20:35,080 --> 00:20:36,680
prove to be impossible.

276
00:20:40,080 --> 00:20:43,280
It may be the same size,

277
00:20:43,280 --> 00:20:46,480
but this modern telescope
can capture the spectrum

278
00:20:46,480 --> 00:20:48,880
of Andromeda in a matter of minutes.

279
00:20:52,560 --> 00:20:57,920
With his telescope, Slipher needed
14 hours to produce one spectrum.

280
00:20:57,920 --> 00:21:00,280
Two days of backbreaking efforts.

281
00:21:02,440 --> 00:21:04,280
Seven hours each night,

282
00:21:04,280 --> 00:21:07,960
constantly adjusting the telescope
to keep it fixed on Andromeda.

283
00:21:11,920 --> 00:21:15,000
Slipher wanted to know how
Andromeda was moving,

284
00:21:15,000 --> 00:21:18,760
and for that he didn't just need the
spectrum of light on Andromeda,

285
00:21:18,760 --> 00:21:21,000
he needed to have the absorption lines.

286
00:21:21,000 --> 00:21:25,240
Now, these are discreet gaps
in the spectrum, like this.

287
00:21:25,240 --> 00:21:29,480
Now, these absorption lines should
always be in the same place

288
00:21:29,480 --> 00:21:31,840
if the source isn't moving.

289
00:21:31,840 --> 00:21:35,480
If they've shifted to the right,
towards the red end of the spectrum,

290
00:21:35,480 --> 00:21:38,680
that means that the source
is moving away from us.

291
00:21:38,680 --> 00:21:42,200
If they've shifted to the left,
towards the blue end of the spectrum,

292
00:21:42,200 --> 00:21:46,160
that means the source is moving
towards us - a blue shift.

293
00:21:46,160 --> 00:21:52,280
Now, after two days of observing, Slipher
was ready to develop his photograph.

294
00:21:52,280 --> 00:21:56,080
And he didn't get something as
beautiful and clean as this.

295
00:21:58,000 --> 00:21:59,840
He got this image.

296
00:21:59,840 --> 00:22:01,640
Now this is in fact blown up.

297
00:22:01,640 --> 00:22:04,320
In fact, what he got was a
much smaller image than this.

298
00:22:04,320 --> 00:22:07,960
And it's not even these
lines, at the top and bottom.

299
00:22:07,960 --> 00:22:12,320
In fact, what he got was this
dirty smudge in the middle.

300
00:22:12,320 --> 00:22:14,440
That was the spectrum from Andromeda.

301
00:22:15,760 --> 00:22:17,800
Now, you might think he'd failed,

302
00:22:17,800 --> 00:22:20,200
that you couldn't get anything
meaningful from this.

303
00:22:20,200 --> 00:22:23,760
In fact, not only was he able to
get a meaningful measurement,

304
00:22:23,760 --> 00:22:28,520
he could work out that Andromeda
showed a very clear blue shift,

305
00:22:28,520 --> 00:22:30,760
that it was moving towards us.

306
00:22:30,760 --> 00:22:36,280
In fact, he worked out it was moving
towards us at a speed of 300km per second,

307
00:22:36,280 --> 00:22:39,040
which actually matches
modern-day estimates.

308
00:22:40,280 --> 00:22:42,560
Slipher had done it.

309
00:22:42,560 --> 00:22:45,800
The first ever measure of
the speed of a nebula.

310
00:22:45,800 --> 00:22:49,720
His skill and tenacity overcoming
the limits of his telescope.

311
00:22:52,720 --> 00:22:57,280
When Slipher presented his findings
at an astronomy meeting in 1914,

312
00:22:57,280 --> 00:22:59,840
he received a standing ovation.

313
00:22:59,840 --> 00:23:03,120
It's often easy to forget how
important people like Slipher are.

314
00:23:04,120 --> 00:23:07,720
The major breakthroughs in
science aren't always about

315
00:23:07,720 --> 00:23:10,520
the big idea or the beautiful theory.

316
00:23:10,520 --> 00:23:14,480
They're often simply reliant on
people who are exceptionally

317
00:23:14,480 --> 00:23:18,080
skilled at observing and
measuring the natural world.

318
00:23:22,320 --> 00:23:26,320
We now know that the Andromeda
nebula is actually a galaxy

319
00:23:26,320 --> 00:23:28,400
like our own, the Milky Way.

320
00:23:30,240 --> 00:23:34,680
And it's Andromeda's movement that
reveals how gravity can shape

321
00:23:34,680 --> 00:23:36,440
the fate of the universe.

322
00:23:42,160 --> 00:23:45,000
Since it was first born in the Big Bang,

323
00:23:45,000 --> 00:23:48,520
the universe has been expanding outwards.

324
00:23:48,520 --> 00:23:51,000
As a result, most galaxies are actually

325
00:23:51,000 --> 00:23:52,840
heading away from each other.

326
00:23:54,160 --> 00:23:56,840
When they first formed, the
same would have been true

327
00:23:56,840 --> 00:23:59,200
of Andromeda and the Milky Way.

328
00:23:59,200 --> 00:24:03,720
Until gravity got to work and began
to overwhelm that expansion.

329
00:24:07,320 --> 00:24:09,880
It's gravity that's dragging Andromeda

330
00:24:09,880 --> 00:24:13,280
and our own Milky Way
galaxy inexorably together.

331
00:24:13,280 --> 00:24:15,790
The question is, if it
can pull off this trick

332
00:24:15,795 --> 00:24:17,880
in our own little
corner of the cosmos,

333
00:24:17,880 --> 00:24:22,000
can it do the same over the
entire expanse of the universe?

334
00:24:36,000 --> 00:24:39,440
If gravity could overwhelm the expansion,

335
00:24:39,440 --> 00:24:42,320
then long before the stars are burnt out,

336
00:24:42,320 --> 00:24:48,120
our vast universe would inevitably,
inescapably collapse in on itself.

337
00:24:50,200 --> 00:24:53,360
The universe would end with a big crunch.

338
00:24:57,200 --> 00:25:01,800
If gravity failed, the universe
would simply continue to expand,

339
00:25:01,800 --> 00:25:05,360
far beyond even the time
when the last star had died.

340
00:25:12,280 --> 00:25:15,520
Everything hinged on one factor,

341
00:25:15,520 --> 00:25:19,280
predicted by Einstein's
general theory of relativity.

342
00:25:23,760 --> 00:25:25,520
Using general relativity

343
00:25:25,520 --> 00:25:29,520
revealed that there were two very
different futures to the universe.

344
00:25:29,520 --> 00:25:33,040
What's more, they were able to
calculate a specific figure

345
00:25:33,040 --> 00:25:36,760
that marked the boundary between
these two different scenarios.

346
00:25:36,760 --> 00:25:39,760
It became known as the critical density.

347
00:25:44,520 --> 00:25:48,520
The critical density was
effectively a threshold

348
00:25:48,520 --> 00:25:52,520
based on how much matter and
energy - how much stuff -

349
00:25:52,520 --> 00:25:55,280
there was in the entire universe.

350
00:25:58,040 --> 00:26:01,280
If that total was above
the critical density,

351
00:26:01,280 --> 00:26:05,040
then gravity would drag the
entire universe back together

352
00:26:05,040 --> 00:26:06,760
into the Big Crunch.

353
00:26:10,280 --> 00:26:13,280
If the total was below
the critical density,

354
00:26:13,280 --> 00:26:17,760
then the expansion of the
universe will continue for ever.

355
00:26:20,080 --> 00:26:24,280
The fate of the entire universe
came down to a simple question -

356
00:26:24,280 --> 00:26:26,520
what universe do we live in?

357
00:26:26,520 --> 00:26:30,000
One that is above the critical
density, or one that is below?

358
00:26:35,520 --> 00:26:39,800
One way to tell was to look at
the expansion of the universe.

359
00:26:40,800 --> 00:26:44,520
If the universe was above the
critical density and heading for

360
00:26:44,520 --> 00:26:49,360
collapse, then the rate of expansion
would already be slowing down.

361
00:26:50,360 --> 00:26:53,520
So, astronomers began
working on a way to measure

362
00:26:53,520 --> 00:26:56,280
how the expansion of the
universe was changing.

363
00:26:59,520 --> 00:27:03,280
They were confident until
a precocious PhD student

364
00:27:03,280 --> 00:27:08,040
called Beatrice Tinsley spotted
a fatal flaw in the plan.

365
00:27:11,280 --> 00:27:14,840
Tinsley, know as "little beetle"
to her family and friends,

366
00:27:14,840 --> 00:27:17,040
was an extremely talented musician.

367
00:27:17,040 --> 00:27:19,040
She could have turned professional.

368
00:27:19,040 --> 00:27:22,280
But instead she decided to focus
on her other great passion,

369
00:27:22,280 --> 00:27:24,040
which was astrophysics.

370
00:27:24,040 --> 00:27:26,040
Here, too, she excelled.

371
00:27:26,040 --> 00:27:30,280
But an academic career in the 1960s,
if you are woman, wasn't easy,

372
00:27:30,280 --> 00:27:33,280
and her institution, the
University of Texas,

373
00:27:33,280 --> 00:27:37,520
seemed determined to ignore this
brilliant scientist in their midst.

374
00:27:37,520 --> 00:27:40,040
Despite that, she completed her PhD

375
00:27:40,040 --> 00:27:43,200
in less than half the time
it would normally take.

376
00:27:44,200 --> 00:27:48,520
And that PhD spelled trouble for
the expansion rate measurements.

377
00:27:51,040 --> 00:27:54,280
The plan was to measure
how galaxies were moving

378
00:27:54,280 --> 00:27:56,520
at different distances from Earth

379
00:27:56,520 --> 00:28:00,040
and therefore at different
times in the past.

380
00:28:02,520 --> 00:28:04,800
How their movement changed

381
00:28:04,800 --> 00:28:08,280
would reveal how the expansion
of the universe was changing.

382
00:28:09,520 --> 00:28:13,280
Measuring the movement was
relatively straightforward.

383
00:28:13,280 --> 00:28:16,520
It was measuring the distance
where the problem lay.

384
00:28:18,280 --> 00:28:21,760
In our everyday world, we're
surrounded by visual clues

385
00:28:21,760 --> 00:28:25,040
that give us a good sense of
scale, and therefore of distance.

386
00:28:25,040 --> 00:28:28,520
But in the vastness of the universe,
this is much more difficult,

387
00:28:28,520 --> 00:28:32,040
so astronomers turned to something
that might seem unusual.

388
00:28:32,040 --> 00:28:33,720
Light itself.

389
00:28:37,040 --> 00:28:40,280
Light is not perhaps an
obvious tape measure,

390
00:28:40,280 --> 00:28:43,120
but in this case it seemed ideal.

391
00:28:43,120 --> 00:28:45,520
Now, this relies on a
very simple principle.

392
00:28:45,520 --> 00:28:50,280
How bright the light appears to me
is dependant on how close I am to it

393
00:28:50,280 --> 00:28:53,520
so when I'm very close, a
lot of light enters my eyes

394
00:28:53,520 --> 00:28:55,280
and it seems bright.

395
00:28:55,280 --> 00:28:59,280
But as I move away, the light has
had more chance to spread out

396
00:28:59,280 --> 00:29:02,760
and less of it enters my
eyes, so it appears dimmer.

397
00:29:02,760 --> 00:29:06,040
Crucially, this change in
the level of brightness

398
00:29:06,040 --> 00:29:09,280
follows a very precise
mathematical relationship.

399
00:29:12,040 --> 00:29:16,040
And I can use this relationship
to calculate distance.

400
00:29:18,560 --> 00:29:21,040
'If I measure the difference in brightness

401
00:29:21,040 --> 00:29:23,040
'between a light next to me...'

402
00:29:23,040 --> 00:29:24,560
220.

403
00:29:25,560 --> 00:29:27,680
'..and one further away...'

404
00:29:27,680 --> 00:29:29,520
About 1.5.

405
00:29:29,520 --> 00:29:32,280
I don't know if you can see that.
It's quite dark.

406
00:29:32,280 --> 00:29:35,520
'..I can work out how
far away the light is.'

407
00:29:37,800 --> 00:29:41,120
And so now I have to
divide these two numbers.

408
00:29:41,120 --> 00:29:45,040
Well, it's roughly 150.

409
00:29:46,040 --> 00:29:48,840
Now I have to take the square root.

410
00:29:48,840 --> 00:29:51,280
The square root of 150...

411
00:29:51,280 --> 00:29:53,280
Well, it's about 12.

412
00:29:53,280 --> 00:29:55,280
It's just over 12.

413
00:29:55,280 --> 00:29:58,600
About 12.2 metres.

414
00:29:59,600 --> 00:30:01,040
Right.

415
00:30:02,040 --> 00:30:04,960
Now to check my working.

416
00:30:07,040 --> 00:30:09,760
It's this principle that
astronomers were using

417
00:30:09,760 --> 00:30:12,040
to measure the distance to galaxies.

418
00:30:15,960 --> 00:30:18,280
So, what I have here...

419
00:30:18,280 --> 00:30:20,760
is 11.5 metres.

420
00:30:20,760 --> 00:30:24,280
It's a bit less than the 12 metres
I calculated, but close enough.

421
00:30:24,280 --> 00:30:26,280
I'm pretty happy with that.

422
00:30:28,280 --> 00:30:30,760
But this technique only works

423
00:30:30,760 --> 00:30:34,520
if you know how bright the
distance object should be,

424
00:30:34,520 --> 00:30:38,280
so you can measure how much
that brightness has changed.

425
00:30:38,280 --> 00:30:42,280
And that would turn out to be
the astronomers' Achilles heel.

426
00:30:44,440 --> 00:30:47,280
They were measuring galaxies
at different distances,

427
00:30:47,280 --> 00:30:50,760
so at different times during
the life of the universe.

428
00:30:50,760 --> 00:30:54,040
This meant that the galaxies
differed in age by millions

429
00:30:54,040 --> 00:30:55,760
or billions of years.

430
00:30:55,760 --> 00:30:58,520
You see, for the distance
measurements to work,

431
00:30:58,520 --> 00:31:01,760
they had to assume that all these
galaxies of different ages

432
00:31:01,760 --> 00:31:04,280
were shining with the same brightness.

433
00:31:04,280 --> 00:31:05,760
In other words,

434
00:31:05,760 --> 00:31:08,520
a galaxy's brightness
doesn't change over time.

435
00:31:08,520 --> 00:31:10,280
But for Beatrice Tinsley,

436
00:31:10,280 --> 00:31:13,760
there was a fatal flaw at the
heart of this assumption.

437
00:31:16,480 --> 00:31:20,280
Tinsley was fascinated by the
life cycle of the stars -

438
00:31:20,280 --> 00:31:23,040
how they changed through their lives.

439
00:31:24,520 --> 00:31:28,040
Her PhD looked at what
effect that would have

440
00:31:28,040 --> 00:31:30,280
on the brightness of galaxies.

441
00:31:33,040 --> 00:31:37,040
For Tinsley, it was clear that
if stars have a life cycle

442
00:31:37,040 --> 00:31:40,760
during which their appearance
and brightness change,

443
00:31:40,760 --> 00:31:44,520
then because galaxies are
fundamentally made of stars,

444
00:31:44,520 --> 00:31:48,040
so too would their
brightness change over time.

445
00:31:50,520 --> 00:31:54,520
Tinsley's findings sent
shockwaves through the field.

446
00:31:54,520 --> 00:31:59,280
"A palpable sense of panic", as one
astronomer of the time described it.

447
00:31:59,280 --> 00:32:02,040
And they were immediately challenged.

448
00:32:02,040 --> 00:32:04,760
You see, a huge amount of
time, effort and money

449
00:32:04,760 --> 00:32:07,760
had been invested in these
expansion measurements

450
00:32:07,760 --> 00:32:11,760
and yet here was this unknown young
PhD student - a woman, no less -

451
00:32:11,760 --> 00:32:13,760
who was questioning it all.

452
00:32:13,760 --> 00:32:17,040
And yet there was no arguing
the logic of Tinsley's work

453
00:32:17,040 --> 00:32:20,440
and, after four years, it
was eventually accepted.

454
00:32:23,520 --> 00:32:26,280
With that, it was back
to the drawing board.

455
00:32:29,040 --> 00:32:32,520
A new way was needed to test
how close the universe was

456
00:32:32,520 --> 00:32:34,280
to the critical density

457
00:32:34,280 --> 00:32:37,960
to see if it would collapse
or continue to expand.

458
00:32:44,520 --> 00:32:46,520
There was another option.

459
00:32:46,520 --> 00:32:48,760
A more direct approach.

460
00:32:52,440 --> 00:32:55,520
One obvious way to see how
close the universe is

461
00:32:55,520 --> 00:32:57,280
to the critical density

462
00:32:57,280 --> 00:33:00,520
is just to count how much
stuff there is out there.

463
00:33:00,520 --> 00:33:04,520
It's a simple enough idea, but
rather difficult to pull off.

464
00:33:04,520 --> 00:33:08,520
After all, in something as almost
unimaginably vast as the universe,

465
00:33:08,520 --> 00:33:11,520
how do you count every galaxy, every star,

466
00:33:11,520 --> 00:33:14,040
every speck of interstellar gas?

467
00:33:14,040 --> 00:33:16,040
It's almost impossible.

468
00:33:18,040 --> 00:33:22,320
So, instead, astronomers cut
the universe down to size.

469
00:33:23,320 --> 00:33:26,520
They took an average count
of just one small part

470
00:33:26,520 --> 00:33:29,760
and then multiplied it up from there.

471
00:33:29,760 --> 00:33:33,040
They could do this thanks to
one unique characteristic

472
00:33:33,040 --> 00:33:34,760
of the universe.

473
00:33:36,200 --> 00:33:39,760
As far as we can tell, the universe
is, on the largest scales,

474
00:33:39,760 --> 00:33:42,280
the same in whatever direction we look.

475
00:33:42,280 --> 00:33:45,520
So an astronomer sitting on
Earth looking out into space

476
00:33:45,520 --> 00:33:49,040
will get pretty much the same
view as an alien astronomer

477
00:33:49,040 --> 00:33:51,520
on a planet thousands of light years away

478
00:33:51,520 --> 00:33:54,280
looking out in a completely
different direction.

479
00:33:54,280 --> 00:33:57,280
And that's why measuring
how much stuff there is

480
00:33:57,280 --> 00:33:59,280
in one small part of the universe

481
00:33:59,280 --> 00:34:03,400
gives us a pretty accurate measure
of how much there is overall.

482
00:34:05,040 --> 00:34:09,040
They took their averages and came
up with a total amount of mass

483
00:34:09,040 --> 00:34:11,040
and energy in the universe.

484
00:34:12,760 --> 00:34:15,760
The results took everyone by surprise.

485
00:34:15,760 --> 00:34:20,040
All of them suggested the universe
was well below the critical density.

486
00:34:20,040 --> 00:34:23,760
In fact, the best estimate suggested
the universe had so little mass

487
00:34:23,760 --> 00:34:28,040
that its density was only a tiny
fraction of the critical value.

488
00:34:29,520 --> 00:34:31,280
Obviously, if right,

489
00:34:31,280 --> 00:34:35,040
there was no way that the
universe was going to collapse.

490
00:34:51,040 --> 00:34:54,200
But there was a problem
with this first estimate

491
00:34:54,200 --> 00:34:58,000
of how close the universe was
to the critical density.

492
00:34:58,000 --> 00:35:02,760
The results were so low, they
just didn't make any sense.

493
00:35:04,280 --> 00:35:06,520
A flat white coffee, please.

494
00:35:08,040 --> 00:35:12,280
Ours is so clearly a universe
of matter, mass and energy.

495
00:35:12,280 --> 00:35:14,280
They dominate our world.

496
00:35:14,280 --> 00:35:16,040
They ARE our world.

497
00:35:16,040 --> 00:35:19,040
These findings painted a
picture of a universe

498
00:35:19,040 --> 00:35:23,520
so alien to our everyday experience
that it is perhaps understandable

499
00:35:23,520 --> 00:35:26,480
it was such a difficult concept to embrace.

500
00:35:27,760 --> 00:35:32,280
What's more, the estimates seemed to
be at odds with the universe itself.

501
00:35:34,760 --> 00:35:37,280
The scale of the mismatch was revealed

502
00:35:37,280 --> 00:35:41,040
when the universe was mapped
on an unprecedented scale

503
00:35:41,040 --> 00:35:44,040
by Margaret Geller at Harvard University.

504
00:35:51,280 --> 00:35:55,280
What Geller and her team did was
first take a slice of the universe

505
00:35:55,280 --> 00:36:01,040
some 500 million light-years long,
300 million light-years wide,

506
00:36:01,040 --> 00:36:04,520
but still a thin wedge
of the visible universe.

507
00:36:04,520 --> 00:36:07,280
They observed as many
galaxies as they could

508
00:36:07,280 --> 00:36:09,480
and plotted them against distance.

509
00:36:09,480 --> 00:36:13,040
So, every one of these dots
is an individual galaxy.

510
00:36:13,040 --> 00:36:15,280
There's over a thousand of them.

511
00:36:15,280 --> 00:36:19,040
What took everyone by surprise
was this pattern that they saw -

512
00:36:19,040 --> 00:36:22,520
these bubbles, or almost
a honeycomb structure.

513
00:36:22,520 --> 00:36:25,520
You see, everyone had assumed
that the galaxies would be

514
00:36:25,520 --> 00:36:28,280
scattered randomly throughout the universe.

515
00:36:28,280 --> 00:36:32,520
Here, for the first time, was
evidence that - far from random -

516
00:36:32,520 --> 00:36:35,280
the universe actually had structure.

517
00:36:36,480 --> 00:36:40,520
And at the heart of this
newly-discovered structure

518
00:36:40,520 --> 00:36:42,520
was the pull of gravity.

519
00:36:44,160 --> 00:36:47,280
Since almost the beginning of the universe,

520
00:36:47,280 --> 00:36:50,280
gravity has been drawing matter together.

521
00:36:51,280 --> 00:36:56,720
First into clouds of gas, which then
clumped together to form galaxies.

522
00:36:59,520 --> 00:37:03,280
These galaxies come together
to form clusters of galaxies

523
00:37:03,280 --> 00:37:05,880
and the clusters into superclusters.

524
00:37:08,240 --> 00:37:10,760
It looks like a work of art.

525
00:37:18,040 --> 00:37:22,520
These superclusters of galaxies
are all joined together

526
00:37:22,520 --> 00:37:26,040
by filaments of dust and gas,

527
00:37:26,040 --> 00:37:30,000
all acting under the
same irresistible pull.

528
00:37:33,680 --> 00:37:36,560
My universe has just collapsed.

529
00:37:36,560 --> 00:37:38,040
Argh!

530
00:37:41,360 --> 00:37:45,520
Here we clearly see gravity
acting as an architect,

531
00:37:45,520 --> 00:37:49,760
shaping and influencing the
structure of the entire universe

532
00:37:49,760 --> 00:37:52,360
on a truly cosmic scale.

533
00:37:54,880 --> 00:37:57,040
No, I think I can do better.

534
00:37:57,040 --> 00:38:00,520
'The problem was, the estimates
of matter in the universe

535
00:38:00,520 --> 00:38:02,040
'were so small...'

536
00:38:02,040 --> 00:38:03,520
Open that up.

537
00:38:03,520 --> 00:38:07,040
'..they put the universe so far
below the critical density,

538
00:38:07,040 --> 00:38:10,760
'that such grand structures
simply could not form.'

539
00:38:10,760 --> 00:38:12,520
I don't like that.

540
00:38:12,520 --> 00:38:14,520
'According to the numbers,

541
00:38:14,520 --> 00:38:17,760
'the universe as we know
it couldn't exist.'

542
00:38:17,760 --> 00:38:19,920
This is a rubbish universe.

543
00:38:28,280 --> 00:38:32,040
There had to be something
missing from the counts.

544
00:38:32,040 --> 00:38:33,760
But what was it?

545
00:38:33,760 --> 00:38:37,040
And what would it mean
for the critical density

546
00:38:37,040 --> 00:38:39,360
and the fate of the universe?

547
00:38:40,880 --> 00:38:44,280
One of the most colourful and
controversial scientists

548
00:38:44,280 --> 00:38:47,280
of the 20th century found the first clue.

549
00:38:48,280 --> 00:38:50,640
Fritz Zwicky.

550
00:38:51,760 --> 00:38:56,040
Zwicky was an eccentric, abrasive
and brilliant scientist,

551
00:38:56,040 --> 00:38:59,360
known occasionally to refer
to the rest of his profession

552
00:38:59,360 --> 00:39:03,280
as "spherical bastards", which is
basically anyone who's a bastard,

553
00:39:03,280 --> 00:39:05,280
whichever way you look at him.

554
00:39:05,280 --> 00:39:07,280
But even those who disliked him

555
00:39:07,280 --> 00:39:10,440
had to admit that he was
capable of brilliant work.

556
00:39:14,880 --> 00:39:18,760
Zwicky was also looking at galaxy clusters

557
00:39:18,760 --> 00:39:22,520
and they would lead him to
discover something extraordinary.

558
00:39:25,360 --> 00:39:29,280
This picture here is just
such a galaxy cluster.

559
00:39:29,280 --> 00:39:31,760
It's called Abell 1689.

560
00:39:31,760 --> 00:39:35,400
Each one of these yellow
dots is part of the cluster.

561
00:39:35,400 --> 00:39:38,280
It's quite incredible to
think that each one of them

562
00:39:38,280 --> 00:39:40,360
is an entire galaxy in itself.

563
00:39:40,360 --> 00:39:44,360
It sort of gives you an impression
of the sheer scale of these things.

564
00:39:45,360 --> 00:39:49,040
Zwicky was fascinated by what
held the clusters together.

565
00:39:50,040 --> 00:39:53,040
The answer, of course, has to be gravity.

566
00:39:53,040 --> 00:39:56,520
Imagine these marbles are all
each individual galaxies,

567
00:39:56,520 --> 00:40:00,280
moving in chaotic orbits around
the centre of the cluster,

568
00:40:00,280 --> 00:40:04,440
but none of them moves fast
enough to be able to break free

569
00:40:04,440 --> 00:40:06,520
and escape from the cluster.

570
00:40:07,520 --> 00:40:11,520
Because of that, Zwicky could use
how fast they were travelling

571
00:40:11,520 --> 00:40:15,520
to measure the strength of
gravity holding them in place.

572
00:40:15,520 --> 00:40:19,520
And the strength of gravity would
tell him how much matter -

573
00:40:19,520 --> 00:40:22,520
how much stuff - there
was within the cluster.

574
00:40:23,760 --> 00:40:26,760
That is where things got very strange,

575
00:40:26,760 --> 00:40:30,520
because the galaxies were
moving at tremendous speeds.

576
00:40:32,640 --> 00:40:36,520
The strength of gravity needed to
hold all these speeding galaxies

577
00:40:36,520 --> 00:40:40,520
within the cluster required far
more mass than he could see.

578
00:40:40,520 --> 00:40:43,040
And it wasn't just a small difference.

579
00:40:43,040 --> 00:40:46,280
In fact, he needed something
like a hundred times more mass

580
00:40:46,280 --> 00:40:48,040
than could be detected.

581
00:40:51,040 --> 00:40:55,760
Zwicky called this mysterious
mass Dunkle Materie.

582
00:40:55,760 --> 00:40:57,520
Dark matter.

583
00:40:58,520 --> 00:41:03,280
Here was a strong candidate for
the missing mass of the universe.

584
00:41:04,280 --> 00:41:09,280
But to know if it took the universe
above or below the critical density,

585
00:41:09,280 --> 00:41:12,520
they had to solve one major problem.

586
00:41:12,520 --> 00:41:17,160
How to study something when there
is no known way of detecting it.

587
00:41:24,920 --> 00:41:28,040
The answer would come thanks
to a discovery made here

588
00:41:28,040 --> 00:41:30,280
at the Jodrell Bank Observatory.

589
00:41:30,280 --> 00:41:34,040
This giant dish is the Bernard
Lovell Radio Telescope

590
00:41:34,040 --> 00:41:39,520
and, in 1973, it spotted something
no-one had ever seen before.

591
00:41:45,280 --> 00:41:49,520
At the time, it was carrying out
a survey of some very distant,

592
00:41:49,520 --> 00:41:51,640
very bright objects -

593
00:41:51,640 --> 00:41:53,400
quasars.

594
00:41:58,040 --> 00:42:02,280
Part way through the survey, they
detected something very unusual.

595
00:42:03,280 --> 00:42:07,040
I've come here today to take
another look at what they saw,

596
00:42:07,040 --> 00:42:10,520
this time using not just the
telescopes here at Jodrell,

597
00:42:10,520 --> 00:42:13,760
but radio telescopes across the country.

598
00:42:22,040 --> 00:42:25,040
Right, here we are - the
control room at Jodrell Bank.

599
00:42:25,040 --> 00:42:27,760
A lovely view there of
the Lovell Telescope.

600
00:42:27,760 --> 00:42:30,040
Now, over here, on these screens,

601
00:42:30,040 --> 00:42:33,760
we see live data coming in
from various telescopes.

602
00:42:33,760 --> 00:42:37,520
One of them, the Mark II, is a
radio telescope at Jodrell Bank,

603
00:42:37,520 --> 00:42:41,440
but the rest are scattered around
the country, all linked together

604
00:42:41,440 --> 00:42:45,080
through optical fibres feeding
into the central computer here.

605
00:42:46,080 --> 00:42:50,280
The point is, the longer you observe
an object, the better-quality image

606
00:42:50,280 --> 00:42:54,520
you get, and after 50 hours of
observation, here's what they see.

607
00:42:54,520 --> 00:42:58,280
This is the same image as
was seen 40 years ago,

608
00:42:58,280 --> 00:43:01,040
showing these two bright dots -

609
00:43:01,040 --> 00:43:03,040
two quasars.

610
00:43:03,040 --> 00:43:06,040
This wasn't the first time
quasars had been seen

611
00:43:06,040 --> 00:43:10,040
but certainly the first time they
had been spotted so close together,

612
00:43:10,040 --> 00:43:12,400
as though they were a pair.

613
00:43:14,000 --> 00:43:16,040
A pair was something new.

614
00:43:17,040 --> 00:43:20,760
They began to gather as much
information about them as possible,

615
00:43:20,760 --> 00:43:23,280
including measuring their spectra -

616
00:43:23,280 --> 00:43:27,040
the unique fingerprint
contained within their light.

617
00:43:30,520 --> 00:43:33,600
Here are the spectra from the two quasars.

618
00:43:33,600 --> 00:43:37,280
Now, even at first glance, I can
tell they look quite similar.

619
00:43:37,280 --> 00:43:40,360
In fact, they are much more
than just quite similar.

620
00:43:40,360 --> 00:43:42,200
When they first measured them,

621
00:43:42,200 --> 00:43:44,720
they saw that they were both red-shifted -

622
00:43:44,720 --> 00:43:47,520
so longer wavelengths - by
exactly the same amount.

623
00:43:47,520 --> 00:43:50,240
And have a look at these emission peaks.

624
00:43:50,240 --> 00:43:53,840
They both fall at exactly
the same wavelength.

625
00:43:53,840 --> 00:43:56,280
In fact, the spectra was so similar

626
00:43:56,280 --> 00:43:58,760
they thought they had made a mistake -

627
00:43:58,760 --> 00:44:01,280
that they had looked at
the same object twice.

628
00:44:01,280 --> 00:44:02,760
But they hadn't.

629
00:44:02,760 --> 00:44:05,040
And that left just one possibility.

630
00:44:05,040 --> 00:44:07,760
What they thought were two separate quasars

631
00:44:07,760 --> 00:44:10,280
were in fact just one single quasar

632
00:44:10,280 --> 00:44:13,760
that had somehow been
split into two images.

633
00:44:13,760 --> 00:44:16,280
A case of astronomical double vision.

634
00:44:19,440 --> 00:44:22,760
There was a theory that
could explain this -

635
00:44:22,760 --> 00:44:26,600
a strange effect predicted
by Albert Einstein -

636
00:44:26,600 --> 00:44:28,760
gravitational lensing.

637
00:44:33,440 --> 00:44:35,720
If you look through this lens,

638
00:44:35,720 --> 00:44:40,880
you see that everything behind it
is warped into strange shapes.

639
00:44:40,880 --> 00:44:43,000
This bizarre effect is because,

640
00:44:43,000 --> 00:44:46,840
as light passes through different
thicknesses of the glass,

641
00:44:46,840 --> 00:44:50,560
it bends, giving rise to a warped image.

642
00:44:50,560 --> 00:44:55,760
Now, Einstein said that matter
- stuff - also warped space,

643
00:44:55,760 --> 00:44:59,760
changing the very shape of
the fabric of the universe,

644
00:44:59,760 --> 00:45:03,280
and so, as light passes
through regions of space

645
00:45:03,280 --> 00:45:06,360
with high concentrations
of matter, it will bend,

646
00:45:06,360 --> 00:45:09,280
just like it does going through
the glass of this lens,

647
00:45:09,280 --> 00:45:12,640
and so giving rise to
similar visual tricks.

648
00:45:14,680 --> 00:45:16,520
How much the light is bent

649
00:45:16,520 --> 00:45:20,480
is dependent on how much
the space is being warped,

650
00:45:20,480 --> 00:45:24,560
and that depends on how much mass there is.

651
00:45:24,560 --> 00:45:26,920
Between the quasar and the telescopes,

652
00:45:26,920 --> 00:45:29,760
there had to be a huge amount of mass,

653
00:45:29,760 --> 00:45:33,440
bending the light so much
that the image is split,

654
00:45:33,440 --> 00:45:36,720
making the single quasar appear as two.

655
00:45:38,360 --> 00:45:41,320
Here's our culprit, or at least part of it.

656
00:45:41,320 --> 00:45:45,440
This smudge here is just one galaxy
within a cluster of galaxies

657
00:45:45,440 --> 00:45:48,440
that sit between us and the distant quasar.

658
00:45:48,440 --> 00:45:50,720
So it's not just a little bit of mass,

659
00:45:50,720 --> 00:45:54,920
but hundreds of galaxies,
each with billions of stars.

660
00:45:54,920 --> 00:45:58,240
Combined, they bend the
light from the quasar,

661
00:45:58,240 --> 00:46:00,080
giving us the double image.

662
00:46:02,720 --> 00:46:06,880
And the double image was crucial
to the study of dark matter.

663
00:46:09,160 --> 00:46:13,840
Even with all the mass and matter
contained in the galaxy cluster,

664
00:46:13,840 --> 00:46:17,040
there wasn't enough to
bend the light that much.

665
00:46:18,040 --> 00:46:22,040
For that, you needed Zwicky's
mysterious and invisible

666
00:46:22,040 --> 00:46:23,800
dark matter.

667
00:46:23,800 --> 00:46:28,200
And carefully analysing exactly
how much the light was distorted

668
00:46:28,200 --> 00:46:31,120
could reveal where that dark matter was.

669
00:46:32,520 --> 00:46:35,360
This is what you get - a map.

670
00:46:35,360 --> 00:46:39,160
In the centre is the normal matter
of the galaxy cluster itself,

671
00:46:39,160 --> 00:46:43,040
but, surrounding it, stretching out
much further, coloured here in red,

672
00:46:43,040 --> 00:46:44,760
is the dark matter.

673
00:46:44,760 --> 00:46:46,960
Look how far out it spreads.

674
00:46:46,960 --> 00:46:50,520
It completely dwarfs the normal
matter of the galaxy cluster.

675
00:46:50,520 --> 00:46:53,520
Zwicky's mysterious and invisible matter

676
00:46:53,520 --> 00:46:56,280
revealed by a cosmic optical illusion.

677
00:46:58,640 --> 00:47:01,520
It couldn't reveal what dark matter was,

678
00:47:01,520 --> 00:47:05,760
but mapping like this, as Jodrell
is still doing to this day,

679
00:47:05,760 --> 00:47:09,840
did give an idea of how
much there was out there,

680
00:47:09,840 --> 00:47:13,800
and it seemed to far
outweigh normal matter,

681
00:47:13,800 --> 00:47:18,360
but was it enough to take the
universe over the critical density?

682
00:47:20,240 --> 00:47:24,360
Even though there appeared to be far
more dark matter than normal matter,

683
00:47:24,360 --> 00:47:26,800
that still seemed to leave the universe

684
00:47:26,800 --> 00:47:29,160
way below the critical density -

685
00:47:29,160 --> 00:47:31,960
but this was still far
from the end of the story.

686
00:47:31,960 --> 00:47:33,880
The discovery of dark matter

687
00:47:33,880 --> 00:47:37,960
had taken the scientific community
completely by surprise.

688
00:47:37,960 --> 00:47:42,400
Trying to work out how close the
universe was to the critical density

689
00:47:42,400 --> 00:47:45,480
was just throwing up more
mysteries than answers.

690
00:47:50,400 --> 00:47:53,480
A shocking new discovery
that initially promised

691
00:47:53,480 --> 00:47:56,120
to finally reveal the fate of the universe

692
00:47:56,120 --> 00:47:59,680
instead threw physics into crisis.

693
00:48:11,200 --> 00:48:15,960
In the 1990s, these telescopes were
part of an international project

694
00:48:15,960 --> 00:48:19,440
looking to finally reveal
the fate of the universe.

695
00:48:23,560 --> 00:48:27,080
They were using a new
technique to once again

696
00:48:27,080 --> 00:48:31,560
look at how the expansion of the
universe had changed over time.

697
00:48:40,880 --> 00:48:44,480
I've come to use this telescope - the GTC -

698
00:48:44,480 --> 00:48:48,080
to observe the object that was
at the heart of those studies.

699
00:48:54,240 --> 00:48:59,040
This huge telescope - you can
see the vast mirror behind it -

700
00:48:59,040 --> 00:49:02,000
is going to take a close
look at a supernova,

701
00:49:02,000 --> 00:49:04,440
the explosive death of a star.

702
00:49:04,440 --> 00:49:09,040
The light reaching us from these
distant epic events would be key

703
00:49:09,040 --> 00:49:12,440
to unlocking how the universe
expanded in the past

704
00:49:12,440 --> 00:49:16,360
and, in turn, would reveal what
would happen to it in the future.

705
00:49:21,240 --> 00:49:23,040
To measure the expansion,

706
00:49:23,040 --> 00:49:26,880
researchers were interested in a
particular type of supernova.

707
00:49:39,360 --> 00:49:42,840
Our target tonight is the
same class of supernovae

708
00:49:42,840 --> 00:49:45,920
that they were searching for - a type Ia.

709
00:49:45,920 --> 00:49:49,280
Now, what made type Ia supernovae so useful

710
00:49:49,280 --> 00:49:50,800
is that, when they went off,

711
00:49:50,800 --> 00:49:54,000
they created an incredibly
bright spike of light.

712
00:49:54,000 --> 00:49:57,920
Briefly, the star would shine
brighter than its entire galaxy.

713
00:49:57,920 --> 00:50:00,400
Not only that, but they always gave off

714
00:50:00,400 --> 00:50:03,320
almost exactly the same
level of brightness.

715
00:50:03,320 --> 00:50:05,600
This meant that not only
could they see them

716
00:50:05,600 --> 00:50:08,120
over vast distances and remote galaxies,

717
00:50:08,120 --> 00:50:12,080
but they could also work out
exactly how far away they were.

718
00:50:12,080 --> 00:50:14,120
So, if they could find enough of them,

719
00:50:14,120 --> 00:50:16,680
they could sample
conditions in the universe

720
00:50:16,680 --> 00:50:20,000
over a wide range of distances and times.

721
00:50:22,840 --> 00:50:26,640
Tonight, astronomer David
Alvarez has been homing in

722
00:50:26,640 --> 00:50:29,760
on a recently discovered type Ia supernova.

723
00:50:32,360 --> 00:50:36,360
Right, David, this is very exciting.
Do you have the supernova?

724
00:50:36,360 --> 00:50:39,240
This is the image of the supernova.

725
00:50:39,240 --> 00:50:41,360
- That thing there?
- That thing there.

726
00:50:41,360 --> 00:50:44,760
- Can you zoom in at all on it?
- Yeah, we can zoom in here.

727
00:50:44,760 --> 00:50:47,080
You can see the bright dot.

728
00:50:47,080 --> 00:50:49,640
And the rest of it is the galaxy?

729
00:50:49,640 --> 00:50:51,840
The rest of the light you can see there

730
00:50:51,840 --> 00:50:54,240
is the host galaxy of the supernova.

731
00:50:54,240 --> 00:50:55,560
I mean, that's incredible.

732
00:50:55,560 --> 00:50:58,640
Here's a galaxy with hundreds
of billions of stars,

733
00:50:58,640 --> 00:51:01,240
but this one exploding star
- this one supernova -

734
00:51:01,240 --> 00:51:05,000
is shining brighter than the
whole of the rest the galaxy.

735
00:51:05,000 --> 00:51:08,600
And you know how far
away this supernova is?

736
00:51:08,600 --> 00:51:10,080
You've measured the distance?

737
00:51:10,080 --> 00:51:13,196
Yeah, the supernova is about
eight billion light years away.

738
00:51:13,201 --> 00:51:14,240
Wow.

739
00:51:17,400 --> 00:51:18,800
As well as the distance,

740
00:51:18,800 --> 00:51:21,800
the spectrum of the
supernova is also crucial.

741
00:51:23,640 --> 00:51:26,080
The astronomers needed the
spectrum of the light

742
00:51:26,080 --> 00:51:28,360
because it gave them the redshift.

743
00:51:28,360 --> 00:51:31,960
You see, as the light travels from
the distant supernova to Earth,

744
00:51:31,960 --> 00:51:34,000
the universe is expanding,

745
00:51:34,000 --> 00:51:37,280
the space the light is travelling
through is stretching,

746
00:51:37,280 --> 00:51:40,160
and so the light itself is also stretching.

747
00:51:40,160 --> 00:51:42,320
Its wavelength is getting longer.

748
00:51:42,320 --> 00:51:44,120
If it leaves the supernova

749
00:51:44,120 --> 00:51:46,440
at a particular wavelength,
a particular colour,

750
00:51:46,440 --> 00:51:50,040
when it arrives in our telescopes,
it's at a longer wavelength -

751
00:51:50,040 --> 00:51:52,920
it's shifted towards the
red end of the spectrum,

752
00:51:52,920 --> 00:51:54,560
hence a redshift.

753
00:51:54,560 --> 00:51:56,920
So knowing the redshift of the light

754
00:51:56,920 --> 00:52:00,880
tells us how much space has
expanded in that time.

755
00:52:00,880 --> 00:52:05,520
In a sense, it gives us a measure
of how big the universe has become.

756
00:52:07,160 --> 00:52:10,880
Because of this, measuring
redshifts at greater distances -

757
00:52:10,880 --> 00:52:13,760
in effect, further back in time -

758
00:52:13,760 --> 00:52:15,680
could create a potted history

759
00:52:15,680 --> 00:52:18,920
of how the expansion of the
universe was changing.

760
00:52:21,440 --> 00:52:25,000
Astronomers were convinced
that gravity must have,

761
00:52:25,000 --> 00:52:28,880
at the very least, been
slowing down the expansion.

762
00:52:28,880 --> 00:52:32,440
The question was - by how much?

763
00:52:32,440 --> 00:52:35,000
By plotting distance

764
00:52:35,000 --> 00:52:37,840
against the redshift's
measure of expansion,

765
00:52:37,840 --> 00:52:40,240
they could finally answer that question.

766
00:52:42,240 --> 00:52:45,880
Now, if you imagine the universe has
been expanding at the same rate -

767
00:52:45,880 --> 00:52:48,680
the rate that it is now -
for its entire history,

768
00:52:48,680 --> 00:52:51,920
I'd get a very simple line.

769
00:52:51,920 --> 00:52:54,200
But astronomers knew
this couldn't be correct

770
00:52:54,200 --> 00:52:57,920
because, of course, gravity is
putting the brakes on the expansion,

771
00:52:57,920 --> 00:53:00,840
so the expansion of the
universe should be slowing down

772
00:53:00,840 --> 00:53:03,120
and, if it's expanding more slowly now,

773
00:53:03,120 --> 00:53:06,160
it should've been expanding
more quickly in the past.

774
00:53:06,160 --> 00:53:10,360
Space stretching more would
mean a bigger redshift.

775
00:53:10,360 --> 00:53:12,360
Now, what does this mean for our supernova?

776
00:53:12,360 --> 00:53:15,880
Well, we know it was eight
billion light years away.

777
00:53:16,960 --> 00:53:19,880
So we know it wouldn't
fall exactly on this line,

778
00:53:19,880 --> 00:53:23,080
which corresponds to a
redshift of about 0.49.

779
00:53:23,080 --> 00:53:25,840
It should sit maybe somewhere over here.

780
00:53:25,840 --> 00:53:28,800
Maybe at a redshift greater than 0.5.

781
00:53:28,800 --> 00:53:33,840
That means this line should
really be curving down like that.

782
00:53:33,840 --> 00:53:36,760
But, of course, the exact shape
of this line would tell them

783
00:53:36,760 --> 00:53:40,360
how much gravity is slowing down
the expansion of the universe

784
00:53:40,360 --> 00:53:44,360
and that would tell them
the fate of the universe.

785
00:53:44,360 --> 00:53:47,160
OK, so, David, you have
the spectrum ready now.

786
00:53:47,160 --> 00:53:49,440
We have it.

787
00:53:49,440 --> 00:53:51,560
Yes, bring it up.

788
00:53:51,560 --> 00:53:53,480
And that gives you a
measure of the redshift.

789
00:53:53,480 --> 00:53:55,120
So what did you measure that to be here?

790
00:53:55,120 --> 00:53:58,120
For this case, we measured 0.47.

791
00:53:58,120 --> 00:54:01,720
0.47! Well, that puts it
on this side of the line.

792
00:54:01,720 --> 00:54:05,560
That means it's not a larger
redshift, but a smaller redshift.

793
00:54:07,480 --> 00:54:10,280
This is fascinating because
it's exactly what they saw.

794
00:54:10,280 --> 00:54:14,120
Not redshifts that were larger,
but redshifts that were smaller.

795
00:54:14,120 --> 00:54:16,320
And they saw this time and time again

796
00:54:16,320 --> 00:54:18,800
and it could only have one explanation -

797
00:54:18,800 --> 00:54:22,320
smaller redshifts meant that the
universe must have been expanding

798
00:54:22,320 --> 00:54:25,240
more slowly in the past than it is today.

799
00:54:25,240 --> 00:54:28,120
In other words, rather than slowing down,

800
00:54:28,120 --> 00:54:31,880
the rate of expansion of the
universe is accelerating.

801
00:54:34,920 --> 00:54:37,720
As more and more supernovae were plotted,

802
00:54:37,720 --> 00:54:39,520
the picture became clearer.

803
00:54:42,480 --> 00:54:45,520
For the first few billion
years after the Big Bang,

804
00:54:45,520 --> 00:54:49,320
it looked as if the expansion rates
had been slowing as expected...

805
00:54:51,160 --> 00:54:53,920
..but then that changed

806
00:54:53,920 --> 00:54:57,000
and the expansion started to accelerate.

807
00:54:59,600 --> 00:55:03,000
It's hard to stress how
much of a shock this was.

808
00:55:03,000 --> 00:55:06,200
Back then, everyone knew that
the expansion of the universe

809
00:55:06,200 --> 00:55:07,920
had to be slowing down.

810
00:55:07,920 --> 00:55:11,200
Now, whether it would slow down
enough to stop and then recollapse,

811
00:55:11,200 --> 00:55:14,280
that wasn't clear, but it
had to be slowing down.

812
00:55:14,280 --> 00:55:18,480
After all, gravity had to be doing
its job of putting the brakes on,

813
00:55:18,480 --> 00:55:19,760
but it wasn't.

814
00:55:19,760 --> 00:55:21,880
About six billion years ago,

815
00:55:21,880 --> 00:55:24,600
the expansion started to speed up.

816
00:55:24,600 --> 00:55:27,440
Clearly, there was some
new and unexpected thing

817
00:55:27,440 --> 00:55:28,760
going on in the universe -

818
00:55:28,760 --> 00:55:30,920
something that science
didn't have an answer for,

819
00:55:30,920 --> 00:55:34,120
something that was pushing the
expansion of the universe

820
00:55:34,120 --> 00:55:36,160
at an accelerating rate.

821
00:55:36,160 --> 00:55:40,040
It became known, for want of
another term, as dark energy.

822
00:55:44,720 --> 00:55:47,600
The best estimates suggest that dark energy

823
00:55:47,600 --> 00:55:50,360
makes up 70% of the universe.

824
00:55:52,400 --> 00:55:56,800
And that means the universe will not
collapse and end in a big crunch.

825
00:55:56,800 --> 00:56:00,400
Instead, dark energy, not gravity,

826
00:56:00,400 --> 00:56:03,600
will define the ultimate
fate of the universe.

827
00:56:06,320 --> 00:56:09,480
Dark energy pushes the universe apart.

828
00:56:09,480 --> 00:56:12,920
It won't carry on expanding
steadily for ever.

829
00:56:12,920 --> 00:56:16,720
Instead, dark energy forces
the universe to fly apart

830
00:56:16,720 --> 00:56:18,600
at an ever-increasing rate.

831
00:56:18,600 --> 00:56:20,560
Galaxies will become so far apart

832
00:56:20,560 --> 00:56:23,120
that light wouldn't be able
to travel between them.

833
00:56:23,120 --> 00:56:26,880
Each one will end up as an
individual island of stars

834
00:56:26,880 --> 00:56:28,240
alone in the cosmos.

835
00:56:28,240 --> 00:56:30,640
It may even become so extreme

836
00:56:30,640 --> 00:56:33,360
that galaxies themselves
will be ripped apart,

837
00:56:33,360 --> 00:56:37,840
leaving individual stars all
alone in the black emptiness.

838
00:56:40,880 --> 00:56:43,120
Then again, maybe not.

839
00:56:44,360 --> 00:56:47,080
After all, the effect of dark energy

840
00:56:47,080 --> 00:56:51,840
seemed to suddenly appear between
six and seven billion years ago.

841
00:56:51,840 --> 00:56:54,680
Who's to say how it'll
behave in the future?

842
00:56:56,440 --> 00:56:58,520
That may sound bizarre

843
00:56:58,520 --> 00:57:02,320
but, with the discovery of
dark energy, all bets are off.

844
00:57:04,040 --> 00:57:07,720
It's hard to stress how little
we know about dark energy.

845
00:57:07,720 --> 00:57:10,160
It has a name, but that's about it.

846
00:57:10,160 --> 00:57:11,960
We don't know what it's made of,

847
00:57:11,960 --> 00:57:14,120
why it's driving the universe apart

848
00:57:14,120 --> 00:57:17,080
and, crucially, how it'll
behave in the future.

849
00:57:17,080 --> 00:57:20,640
And that leaves a big hole in our
understanding of the universe

850
00:57:20,640 --> 00:57:22,360
and its ultimate fate.

851
00:57:24,440 --> 00:57:28,360
Dark energy may simply
be part of the universe,

852
00:57:28,360 --> 00:57:30,400
built into the way it works...

853
00:57:33,760 --> 00:57:37,040
..or it could point to
a fundamental problem

854
00:57:37,040 --> 00:57:41,480
with the most important and trusted
scientific theories we have...

855
00:57:43,600 --> 00:57:46,160
..ones that are at the very
heart of our understanding

856
00:57:46,160 --> 00:57:47,880
of how the world works.

857
00:57:52,320 --> 00:57:56,680
How the universe will end started
as astronomy's great challenge,

858
00:57:56,680 --> 00:57:58,840
but the fate of the universe has become

859
00:57:58,840 --> 00:58:01,480
much more than just an academic question.

860
00:58:01,480 --> 00:58:05,000
Through the discovery of this
strange, enigmatic energy -

861
00:58:05,000 --> 00:58:08,880
if, indeed, that's what it is - one
that defies current understanding,

862
00:58:08,880 --> 00:58:12,200
it's spread to the heart
of fundamental physics.

863
00:58:12,200 --> 00:58:15,160
Finding the answer to how
the universe will end

864
00:58:15,160 --> 00:58:20,040
could have profound implications
on how we understand our world.

865
00:58:24,800 --> 00:58:28,600
If you want to find out more about
the universe and the end of time,

866
00:58:28,600 --> 00:58:28,600
go to the address below and follow
the links to the Open University.

The B

1
00:00:07,000 --> 00:00:09,560
It is a good rule of
thumb that, in science,

2
00:00:09,560 --> 00:00:13,240
the simplest questions are
often the hardest to answer.

3
00:00:16,400 --> 00:00:19,520
Questions like, how did the universe begin?

4
00:00:21,640 --> 00:00:26,000
In fact, until relatively recently,
science simply didn't have the tools

5
00:00:26,000 --> 00:00:29,960
to begin to answer questions about
the origins of the universe.

6
00:00:31,320 --> 00:00:34,680
But in the last 100 years, a
series of breakthroughs have been

7
00:00:34,680 --> 00:00:39,600
made by men and women who, through
observation, determination

8
00:00:39,600 --> 00:00:46,240
and even sheer good luck, were able
to solve this epic cosmic mystery.

9
00:00:46,240 --> 00:00:48,520
This was real astronomical gold.

10
00:00:48,520 --> 00:00:51,280
I am going to recreate their
most famous discoveries

11
00:00:51,280 --> 00:00:53,600
and perform their greatest experiments...

12
00:00:53,600 --> 00:00:56,960
30,000 km/s.

13
00:00:56,960 --> 00:01:00,200
..that take us from the very
biggest objects in the universe

14
00:01:00,200 --> 00:01:02,960
to the infinitesimally small,

15
00:01:02,960 --> 00:01:06,480
until I reach the limits of
our knowledge by travelling

16
00:01:06,480 --> 00:01:10,640
back in time to recreate the
beginning of the universe.

17
00:01:10,640 --> 00:01:14,280
The moment one millionth of
a second after the universe

18
00:01:14,280 --> 00:01:16,400
sprang into existence.

19
00:01:16,400 --> 00:01:19,360
This is a time before matter
itself has formed in any way

20
00:01:19,360 --> 00:01:21,760
that we would recognise it.

21
00:01:21,760 --> 00:01:25,400
It is as close as we can
hope to get to creation,

22
00:01:25,400 --> 00:01:28,280
to the beginning of time,

23
00:01:28,280 --> 00:01:30,480
the beginning of the universe itself.

24
00:01:55,200 --> 00:01:59,560
It is a remarkable fact that science
took hundreds of years to come up

25
00:01:59,560 --> 00:02:02,760
with a theory to explain the
origins of the universe.

26
00:02:05,080 --> 00:02:07,760
All the more surprising,
given what a simple

27
00:02:07,760 --> 00:02:09,800
and fundamental question it is.

28
00:02:11,280 --> 00:02:15,000
There is something quintessentially
human about asking the question,

29
00:02:15,000 --> 00:02:17,480
where does all of this come from?

30
00:02:17,480 --> 00:02:20,880
Perhaps because it is a deeper,
more fundamental version of

31
00:02:20,880 --> 00:02:22,240
where I come from?

32
00:02:29,640 --> 00:02:33,360
Yet, for most of human history,
the answers to such an apparently

33
00:02:33,360 --> 00:02:37,000
simple question could only
be attempted by religion.

34
00:02:39,200 --> 00:02:42,800
It wasn't until the middle of
the 20th century that science

35
00:02:42,800 --> 00:02:47,000
built a coherent and persuasive
creation story of its own.

36
00:02:47,000 --> 00:02:51,760
It was a story based on theory,
predictions and observation,

37
00:02:51,760 --> 00:02:55,440
a story that could finally explain
what had happened at the very

38
00:02:55,440 --> 00:02:58,760
beginning of time, the beginning
of the universe itself.

39
00:03:03,720 --> 00:03:07,640
A little over 100 years ago, if
scientists considered the life of

40
00:03:07,640 --> 00:03:12,600
the universe at all, they considered
it eternal, infinite and stable.

41
00:03:13,880 --> 00:03:15,680
No beginning and no end.

42
00:03:17,960 --> 00:03:21,560
So even framing the question about
the origins of the universe

43
00:03:21,560 --> 00:03:22,720
was impossible.

44
00:03:24,440 --> 00:03:28,040
But at the beginning of the 20th
century, that began to change.

45
00:03:31,000 --> 00:03:33,840
New discoveries shook the old certainties

46
00:03:33,840 --> 00:03:38,120
and paved the way for questions
about where the universe came from.

47
00:03:42,400 --> 00:03:45,400
One observation transformed our idea about

48
00:03:45,400 --> 00:03:47,280
the true scale of the universe.

49
00:03:50,840 --> 00:03:53,080
It began with a mystery in the sky.

50
00:04:00,280 --> 00:04:03,520
By the early part of the 20th
century, it was well known

51
00:04:03,520 --> 00:04:09,000
that our solar system way
within a galaxy, the Milky Way.

52
00:04:09,000 --> 00:04:12,800
Every single star we can see
in the sky with the naked eye

53
00:04:12,800 --> 00:04:17,920
is within our own galaxy and,
until the 1920s, all these stars,

54
00:04:17,920 --> 00:04:22,600
this single galaxy, was the full
extent of the entire universe.

55
00:04:22,600 --> 00:04:24,640
Beyond it was just an empty void.

56
00:04:26,480 --> 00:04:30,080
But there were some enigmatic
objects up there as well,

57
00:04:30,080 --> 00:04:33,840
just discernible to the naked
eye that looked different.

58
00:04:35,320 --> 00:04:38,240
And one of the most notable is Andromeda.

59
00:04:41,040 --> 00:04:44,480
You can find Andromeda if
you know where to look.

60
00:04:44,480 --> 00:04:47,920
So, if you start from
Cassiopeia, those five stars

61
00:04:47,920 --> 00:04:52,520
shaped like a sideways letter M,
if you move across from the point,

62
00:04:52,520 --> 00:04:56,560
from the points of the M, slightly
up is where you should find it.

63
00:04:56,560 --> 00:05:01,760
Now, I'm going to use my binoculars
to help me in the first instance.

64
00:05:01,760 --> 00:05:04,640
And if I zoom across...

65
00:05:04,640 --> 00:05:06,960
Yeah, there it is.

66
00:05:06,960 --> 00:05:10,040
You can tell it's not a star.
I mean, it's basically

67
00:05:10,040 --> 00:05:14,800
a very faint smudge stuck
between those two stars.

68
00:05:14,800 --> 00:05:16,400
That is it straight up there -

69
00:05:16,400 --> 00:05:19,840
that is M31, the great Andromeda nebula.

70
00:05:19,840 --> 00:05:23,200
Now, they were called nebulae,
because they had this smudgy,

71
00:05:23,200 --> 00:05:25,400
sort of wispy, cloudy nature.

72
00:05:25,400 --> 00:05:28,920
In fact, the word nebula derives
from the Latin for cloud.

73
00:05:33,360 --> 00:05:37,600
These indistinct objects were found
scattered throughout the night sky.

74
00:05:44,400 --> 00:05:48,480
Telescopes revealed many of these
nebulae were far more complex

75
00:05:48,480 --> 00:05:51,160
than simple clouds of interstellar gas.

76
00:05:55,400 --> 00:05:58,920
They appeared to be vast
collections of stars

77
00:05:58,920 --> 00:06:02,560
and that raised two
intriguing possibilities.

78
00:06:02,560 --> 00:06:06,440
Were these stellar nurseries
places where stars were born,

79
00:06:06,440 --> 00:06:09,760
and therefore residing
within our own galaxy, or,

80
00:06:09,760 --> 00:06:13,520
much more profoundly, were these
beautiful, enigmatic objects

81
00:06:13,520 --> 00:06:18,560
galaxies in their own right sitting
way outside the Milky Way?

82
00:06:21,160 --> 00:06:24,800
The implications of that second
possibility were enormous.

83
00:06:25,920 --> 00:06:27,720
If true, it would instantly

84
00:06:27,720 --> 00:06:32,280
and utterly transform our idea
about the size of the universe.

85
00:06:42,760 --> 00:06:46,600
Here was an opportunity for an
ambitious astronomer to make

86
00:06:46,600 --> 00:06:49,160
a real name for themselves.

87
00:06:49,160 --> 00:06:52,320
Perhaps someone with a
really big telescope.

88
00:07:11,680 --> 00:07:16,320
Step forward this man - Edwin
Hubble, a man from Missouri,

89
00:07:16,320 --> 00:07:19,440
although if you had ever met
him, you'd never have guessed,

90
00:07:19,440 --> 00:07:23,880
because he developed this weird
persona, a pipe smoking tea drinker

91
00:07:23,880 --> 00:07:28,480
with a very affected
aristocratic English accent.

92
00:07:28,480 --> 00:07:32,040
Hubble is probably the most
famous astronomer ever,

93
00:07:32,040 --> 00:07:36,200
not least because of his consummate
skill at self-promotion,

94
00:07:36,200 --> 00:07:39,840
but also because of the incredible
measurements he would make.

95
00:07:41,880 --> 00:07:44,600
In Hubble's day, when
it came to observations

96
00:07:44,600 --> 00:07:47,200
and new discoveries, size mattered.

97
00:07:52,520 --> 00:07:57,160
Today, this is the most powerful
optical telescope in the world,

98
00:07:57,160 --> 00:08:01,160
the GTC, with a primary mirror

99
00:08:01,160 --> 00:08:05,080
over 10 metres, or 400 inches, in diameter.

100
00:08:07,480 --> 00:08:09,600
Far bigger than anything Hubble had.

101
00:08:11,440 --> 00:08:13,640
In September 1923,

102
00:08:13,640 --> 00:08:16,120
Hubble was working at what was
then the biggest telescope

103
00:08:16,120 --> 00:08:18,760
in the world, the 100-inch Hooker telescope

104
00:08:18,760 --> 00:08:21,720
at the Mount Wilson Observatory,
perched on top of the

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High Sierra mountains overlooking
Los Angeles in California.

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He was using the telescope to
study one of the most prominent

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nebulae in the sky, the Andromeda nebula.

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The same nebula I looked at earlier,
and it was while observing it

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that one very special star
caught Hubble's attention,

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one that could reveal the
true nature of Andromeda.

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And I am going to use this
telescope to look for it now.

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00:08:55,200 --> 00:08:58,880
This is the control room of the
GTC and, tonight, they've pointed

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the telescope at Andromeda and they
are going to take a picture of it.

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It takes about a minute for the exposure

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- to give you a clear enough image?
- That's right.

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Now, the picture is finished,
so we're going to open it.

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OK, so, this is Andromeda here.

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That's Andromeda, that's right.

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And now, this is Hubble's original plate.

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Right, now, Hubble's star is
down here in this corner.

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Can you find it in your image?

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Yeah, if you take the
image and you compare it,

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you will see that we don't see that one.

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What we see is the edge of the galaxy,

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so we have to go a little
bit further west...

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- Oh, I see, so all this is just the edge.
- That's the edge.

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I was assuming it was
the centre of the galaxy.

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No, no, no.

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It just goes to show how much more
resolution your telescope can get.

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- That's right.
- OK, so, can we see that particular star?

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Yes, in order to find that particular star,

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because it is so faint,

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we have to look for references
which are brighter.

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And, in this case, you will
see four stars in here,

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which are these four stars.

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And the star Hubble found
will be this one here.

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That's it...

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That tiny star is the
one that Hubble found.

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That's amazing.

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00:10:10,840 --> 00:10:13,840
And are you able to get a
magnitude for that star?

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00:10:13,840 --> 00:10:16,600
Yeah, we have to do a little bit
of processing on the image,

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but we are able to get it.

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OK. Hubble had found his star.

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He knew it was special,

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because he compared his plate with
others taken over previous nights

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00:10:26,720 --> 00:10:30,440
and he noticed that his star
changed in brightness -

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some nights it was brighter,
some nights it was dimmer.

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00:10:33,760 --> 00:10:38,560
He realised this is a variable star,
and he saw the significance of it.

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He could see that this was
real astronomical gold.

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00:10:44,200 --> 00:10:46,800
His star was a Cepheid variable.

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In the stellar bestiary,

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00:10:48,680 --> 00:10:52,280
Cepheid variable stars
hold very special place...

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..because, by studying the way
their brightness changes,

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astronomers can calculate
how far away they are.

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00:11:02,920 --> 00:11:06,320
Hubble's Cepheid was the first
to be discovered in a nebula,

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so he knew that, if he
could measure its period,

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he would be able to work
out its distance from us.

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So, Hubble set about meticulously measuring

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how his star's luminosity varied.

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It's not hard to imagine how exciting

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this must have been for Hubble.

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At his fingertips was the
opportunity to resolve

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a fundamental yet simple question -

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was this nebula within the
Milky Way or beyond it?

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00:11:35,760 --> 00:11:39,080
The answer would reshape our
knowledge of the universe.

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Hubble measured the
luminosity, or brightness,

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of his star over many nights
and plotted this curve here.

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Now, when we measured tonight,
we found it had a value of 18.6

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and I know because they measured it
last night to be slightly dimmer

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that it falls on this side of the curve.

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But more important is the period,

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the time in days, from peak
brightness to peak brightness.

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Hubble measured this to be 31.415 days.

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This is the critical measurement.

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Armed with this and its
apparent brightness,

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Hubble calculated the distance
to the Andromeda nebula.

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It was immediately apparent that
this star is very far away.

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But when Hubble did his calculation,
he worked out that it was

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900,000 light years away,

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making this star the most
remote object ever recorded.

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00:12:42,440 --> 00:12:44,760
It could mean only one thing -

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not only is Andromeda a
galaxy in its own right...

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00:12:49,760 --> 00:12:52,600
..but it lies well beyond
our own Milky Way...

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00:12:54,560 --> 00:12:56,840
..and the myriad of other elliptical

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00:12:56,840 --> 00:13:01,600
and spiral nebulae were also
individual distant galaxies.

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00:13:03,600 --> 00:13:06,720
It was a moment in human
consciousness when the universe

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00:13:06,720 --> 00:13:10,640
had suddenly and dramatically
got considerably bigger.

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00:13:10,640 --> 00:13:14,920
With this observation, Hubble had
redrawn the observable universe.

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00:13:14,920 --> 00:13:17,520
It might not have directly challenged

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00:13:17,520 --> 00:13:19,600
the idea of a stable universe,

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00:13:19,600 --> 00:13:23,120
but it shattered long-held
assumptions and opened

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00:13:23,120 --> 00:13:26,480
the possibility of other bigger secrets,

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00:13:26,480 --> 00:13:29,600
like an origin to the universe.

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00:13:29,600 --> 00:13:33,800
Into this profoundly-expanded
cosmos strode someone who would,

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00:13:33,800 --> 00:13:37,760
without realising it, provide the
tools to unlock that secret.

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00:13:39,160 --> 00:13:40,200
This guy.

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00:13:52,200 --> 00:13:54,720
A story as great as one that explains

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00:13:54,720 --> 00:13:58,840
the origins of the universe would
somehow feel wrong without involving

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00:13:58,840 --> 00:14:01,720
a scientist as great as Albert Einstein.

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00:14:01,720 --> 00:14:03,840
And so, of course, it does,

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00:14:03,840 --> 00:14:07,560
because it was Einstein who provided
the theoretical foundations

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00:14:07,560 --> 00:14:09,680
needed to study the universe

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00:14:09,680 --> 00:14:13,560
and effectively invent the
science of cosmology.

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00:14:16,480 --> 00:14:21,320
100 years ago, he proposed his
general theory of relativity.

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00:14:21,320 --> 00:14:23,640
It turned physics on its head and gave us

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00:14:23,640 --> 00:14:26,240
a completely new
understanding of the world.

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00:14:30,600 --> 00:14:34,280
He proposed that gravity
was caused by the warping

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00:14:34,280 --> 00:14:39,000
or bending of space-time by massive
objects like planets and stars.

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00:14:43,800 --> 00:14:46,520
His theories were revolutionary.

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00:14:46,520 --> 00:14:49,360
Einstein was a maverick who
ignored the conventional

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00:14:49,360 --> 00:14:51,840
to follow his own remarkable instincts.

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00:14:55,280 --> 00:14:57,440
One of his lecturers once told him,

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00:14:57,440 --> 00:15:00,680
"You are a smart boy,
Einstein, a very smart boy.

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00:15:00,680 --> 00:15:02,800
"But you have one great fault -

215
00:15:02,800 --> 00:15:06,200
"you do not allow yourself
to be told anything."

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00:15:06,200 --> 00:15:09,280
Of course, it was this very
quality that would allow him

217
00:15:09,280 --> 00:15:13,280
to change the world of physics
and, of course, to mark him out

218
00:15:13,280 --> 00:15:16,240
as one of the greatest
thinkers of the 20th century.

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00:15:19,320 --> 00:15:23,840
And in 1917, he took his
general theory of relativity

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00:15:23,840 --> 00:15:26,520
and applied it to the entire universe.

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00:15:28,160 --> 00:15:30,400
By following the logic of his theory,

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00:15:30,400 --> 00:15:33,520
he arrived at something rather unsettling -

223
00:15:33,520 --> 00:15:36,520
the combined attraction of gravity from all

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00:15:36,520 --> 00:15:40,000
the matter in the universe would pull every

225
00:15:40,000 --> 00:15:44,280
object in the cosmos
together, beginning slowly

226
00:15:44,280 --> 00:15:47,320
but gradually accelerating until...

227
00:15:49,160 --> 00:15:50,920
Gravity would ultimately

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00:15:50,920 --> 00:15:55,080
and inevitably lead to the
collapse of the universe itself.

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00:15:57,680 --> 00:16:01,040
But Einstein believed, like
virtually everyone else,

230
00:16:01,040 --> 00:16:05,200
that the universe was eternal
and static and certainly wasn't

231
00:16:05,200 --> 00:16:08,800
unstable or ever likely
to collapse in on itself.

232
00:16:16,560 --> 00:16:19,840
But his equations appeared
to show the opposite.

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00:16:20,880 --> 00:16:23,520
In order to prevent the
demise of the universe

234
00:16:23,520 --> 00:16:27,520
and keep everything in balance,
he adds this in his equation -

235
00:16:27,520 --> 00:16:30,920
Lambda, or the Cosmological Constant.

236
00:16:30,920 --> 00:16:33,800
It is a sort of made-up
force of anti-gravity

237
00:16:33,800 --> 00:16:37,160
that acts against normal gravity itself.

238
00:16:37,160 --> 00:16:40,440
Now, he had no evidence for
this, but it helped ensure

239
00:16:40,440 --> 00:16:43,920
that his equations described
a stable universe.

240
00:16:46,200 --> 00:16:50,600
Within his grasp was the secret
to the origins of the universe.

241
00:16:52,280 --> 00:16:56,240
Yet Einstein simply couldn't,
or wouldn't, bring himself

242
00:16:56,240 --> 00:16:59,400
to accept the implications
of his own equations.

243
00:17:01,040 --> 00:17:04,880
With hindsight, it seems
remarkable that Einstein did this.

244
00:17:04,880 --> 00:17:08,320
I mean, here was a man who
had revolutionised science

245
00:17:08,320 --> 00:17:10,920
by rejecting conventional wisdom

246
00:17:10,920 --> 00:17:14,840
and yet, he couldn't bring
himself to trust his own theory.

247
00:17:14,840 --> 00:17:18,000
He felt compelled to massage his equation

248
00:17:18,000 --> 00:17:20,240
to fit the established view.

249
00:17:20,240 --> 00:17:22,880
He even admitted that the
Cosmological Constant

250
00:17:22,880 --> 00:17:27,360
was necessary only for the
purposes of making a quasi-static

251
00:17:27,360 --> 00:17:32,240
distribution of matter, basically
to keep things the way they were.

252
00:17:32,240 --> 00:17:35,880
Whatever his reasons, this
little character, Lambda,

253
00:17:35,880 --> 00:17:37,440
would return to haunt him.

254
00:17:41,240 --> 00:17:44,560
Because, while it prevented
Einstein from understanding

255
00:17:44,560 --> 00:17:45,800
the implications...

256
00:17:48,360 --> 00:17:51,880
..his ideas opened the way
for someone else to propose

257
00:17:51,880 --> 00:17:54,520
a theory for the origin of the universe.

258
00:17:59,720 --> 00:18:04,520
He was a young part-time university
lecturer of theoretical physics.

259
00:18:06,560 --> 00:18:09,920
His idea was so radical, it
shocked the world of physics

260
00:18:09,920 --> 00:18:12,280
and split the scientific community.

261
00:18:12,280 --> 00:18:16,560
He started an argument that wouldn't
be resolved for half a century.

262
00:18:16,560 --> 00:18:18,600
His name was Georges Lemaitre.

263
00:18:21,240 --> 00:18:24,280
Now, the eagle-eyed might
spot the dog collar.

264
00:18:24,280 --> 00:18:28,200
In fact, he was both a physicist
and an ordained priest.

265
00:18:28,200 --> 00:18:30,720
Of this apparently curious dual role,

266
00:18:30,720 --> 00:18:34,200
Lemaitre said, "There were two
ways of pursuing the truth.

267
00:18:34,200 --> 00:18:36,440
"I decided to follow both."

268
00:18:36,440 --> 00:18:39,080
And, using Einstein's theory of relativity,

269
00:18:39,080 --> 00:18:41,880
he developed his own cosmological models.

270
00:18:43,320 --> 00:18:46,360
Lemaitre's model described a universe that,

271
00:18:46,360 --> 00:18:49,760
far from being static,
was actually expanding,

272
00:18:49,760 --> 00:18:52,520
with galaxies hurtling
away from one another.

273
00:18:56,840 --> 00:19:00,040
Furthermore, Lemaitre saw
the implications of this.

274
00:19:00,040 --> 00:19:03,600
Winding back time, he deduced
that there had to be a moment

275
00:19:03,600 --> 00:19:08,000
when the entire universe was
squeezed into a tiny volume,

276
00:19:08,000 --> 00:19:10,720
something he dubbed the primeval atom.

277
00:19:13,600 --> 00:19:17,520
This was essentially the first
description of what became known

278
00:19:17,520 --> 00:19:21,880
as the big bang theory, the moment
of creation of the universe.

279
00:19:27,680 --> 00:19:31,360
These were revolutionary ideas
and so he published them

280
00:19:31,360 --> 00:19:35,840
in the Annales de la Societe
Scientifique de Bruxelles,

281
00:19:35,840 --> 00:19:39,600
where they were promptly ignored
by the scientific community.

282
00:19:41,760 --> 00:19:45,960
So, he travelled to Brussels to
try to gain support for his idea.

283
00:19:49,400 --> 00:19:54,280
The 1927 Solvay Conference, held
here in Brussels, was probably

284
00:19:54,280 --> 00:19:58,240
the most famous and greatest
meeting of minds ever assembled.

285
00:20:01,400 --> 00:20:02,640
But for our story,

286
00:20:02,640 --> 00:20:05,560
the most significant meeting
didn't happen here.

287
00:20:05,560 --> 00:20:08,840
It wasn't planned and happened
away from the conference.

288
00:20:10,800 --> 00:20:12,040
It happened here.

289
00:20:14,440 --> 00:20:18,520
In this park, the unknown Lemaitre
approached the most famous,

290
00:20:18,520 --> 00:20:21,120
the most feted scientist in the world -

291
00:20:21,120 --> 00:20:22,520
Albert Einstein.

292
00:20:25,000 --> 00:20:29,520
Here, finally, was his chance to
explain his idea about an expanding

293
00:20:29,520 --> 00:20:34,920
universe to the very person whose
theory he had used to derive it.

294
00:20:34,920 --> 00:20:38,800
You can only imagine Lemaitre's
trepidation as he approached.

295
00:20:38,800 --> 00:20:41,880
If Einstein endorsed his radical idea,

296
00:20:41,880 --> 00:20:43,720
then surely it would be accepted.

297
00:20:43,720 --> 00:20:47,520
Surely this brilliant mind,
this titan of physics,

298
00:20:47,520 --> 00:20:51,280
this deeply original thinker, would
see the merits of his theory.

299
00:20:52,760 --> 00:20:55,080
But after a brief discussion,

300
00:20:55,080 --> 00:20:58,240
Einstein rejected his idea out of hand.

301
00:20:58,240 --> 00:20:59,880
According to Lemaitre, he said,

302
00:20:59,880 --> 00:21:02,160
"Vos calculs sont corrects,

303
00:21:02,160 --> 00:21:05,200
"mais votre physique est abominable."

304
00:21:05,200 --> 00:21:06,840
As far as Einstein was concerned,

305
00:21:06,840 --> 00:21:09,880
his maths might have been
correct, but his understanding

306
00:21:09,880 --> 00:21:13,560
of how the real world worked
was, well, abominable.

307
00:21:16,040 --> 00:21:20,680
Once again, Einstein dismissed
the idea of a dynamic universe.

308
00:21:25,280 --> 00:21:28,400
Lemaitre's paper should
have ignited science,

309
00:21:28,400 --> 00:21:31,720
but without the backing of such a
huge and influential figure as

310
00:21:31,720 --> 00:21:37,960
Einstein, his ground-breaking idea
was doomed to be quietly forgotten,

311
00:21:37,960 --> 00:21:42,800
unless some observation or
evidence showed up to support

312
00:21:42,800 --> 00:21:44,960
the idea of an expanding universe.

313
00:21:52,160 --> 00:21:55,760
Edwin Hubble, here, was riding
high after his discovery that

314
00:21:55,760 --> 00:21:58,400
proved there were galaxies
outside of our own.

315
00:21:58,400 --> 00:22:01,000
He was feted by Hollywood glitterati,

316
00:22:01,000 --> 00:22:03,000
a guest of honour at the Oscars,

317
00:22:03,000 --> 00:22:05,840
and, with access to the world's
most powerful telescope,

318
00:22:05,840 --> 00:22:07,920
he was ready for his next challenge.

319
00:22:13,240 --> 00:22:17,520
He had heard of some unusual
observations that many galaxies

320
00:22:17,520 --> 00:22:19,880
appeared to be moving away from us.

321
00:22:21,800 --> 00:22:24,360
No-one could understand why this might be.

322
00:22:27,080 --> 00:22:30,720
So, in 1928, the world's
most famous astronomer

323
00:22:30,720 --> 00:22:35,400
turned his attention to this new
cosmic mystery and began to measure

324
00:22:35,400 --> 00:22:39,160
the speed that these galaxies
were moving relative to Earth.

325
00:22:44,200 --> 00:22:47,640
To measure the velocity that a
galaxy was receding from us,

326
00:22:47,640 --> 00:22:50,320
Hubble use something called redshift.

327
00:22:50,320 --> 00:22:54,160
Now, it's not a perfect analogy,
but the effect is similar to one

328
00:22:54,160 --> 00:22:56,720
most of us are familiar with in sound -

329
00:22:56,720 --> 00:23:00,160
the pitch of a car engine as
it approaches us is higher,

330
00:23:00,160 --> 00:23:02,800
because the sound waves are compressed,

331
00:23:02,800 --> 00:23:06,040
but the pitch drops lower
as the car recedes,

332
00:23:06,040 --> 00:23:08,400
because the sound waves are stretched.

333
00:23:11,480 --> 00:23:13,720
The effect is similar with light waves.

334
00:23:13,720 --> 00:23:17,560
As the source of light moves towards
us, the observed wavelength

335
00:23:17,560 --> 00:23:21,040
is squashed towards the violet
or blue end of the spectrum.

336
00:23:21,040 --> 00:23:23,640
But if the source is moving away from us,

337
00:23:23,640 --> 00:23:27,280
the wavelength is stretched towards
the red end of the spectrum,

338
00:23:27,280 --> 00:23:30,480
or redshifted, in the
parlance of astronomers.

339
00:23:30,480 --> 00:23:33,680
And the greater the velocity
the object is receding,

340
00:23:33,680 --> 00:23:35,200
the greater the redshift.

341
00:23:39,440 --> 00:23:43,720
With his assistant, Milton Humason,
Hubble spent the next year

342
00:23:43,720 --> 00:23:46,720
carefully measuring the
redshift of galaxies.

343
00:23:47,920 --> 00:23:50,840
And I have got the chance to
do the same thing right now

344
00:23:50,840 --> 00:23:52,400
using this telescope.

345
00:23:55,560 --> 00:23:59,160
OK, Massimo, have you
found a galaxy for me?

346
00:23:59,160 --> 00:24:01,880
Yes, I found this galaxy.

347
00:24:01,880 --> 00:24:03,920
So, how far away is this?

348
00:24:03,920 --> 00:24:08,400
It is approximately 430 megaparsec far.

349
00:24:08,400 --> 00:24:12,440
So, if you convert that to light years...
430 x 3.26...

350
00:24:12,440 --> 00:24:17,280
So it's about 1.5 billion light years away.

351
00:24:17,280 --> 00:24:19,080
- Yeah, yeah.
- OK.

352
00:24:21,160 --> 00:24:25,800
Hubble needed to measure the average
light coming from the galaxy

353
00:24:25,800 --> 00:24:29,440
in order to get a spectrum, so that
he could calculate the redshift.

354
00:24:29,440 --> 00:24:33,560
Now, Humason did this by
exposing a photographic plate

355
00:24:33,560 --> 00:24:36,920
and it took him a whole week
to collect enough light

356
00:24:36,920 --> 00:24:38,320
to get the spectrum.

357
00:24:38,320 --> 00:24:42,040
But here at the TNG, the Galileo
Telescope, they use instead

358
00:24:42,040 --> 00:24:45,960
a very sensitive chip that can
do this much more quickly.

359
00:24:45,960 --> 00:24:49,040
How long does it take for
you to get a spectrum?

360
00:24:49,040 --> 00:24:52,520
Approximately 10, 15 minutes.

361
00:24:52,520 --> 00:24:55,680
So, 10 or 15 minutes'
exposure compared with a week

362
00:24:55,680 --> 00:24:57,280
back in Hubble's time -

363
00:24:57,280 --> 00:25:00,160
far more powerful than
anything they had back then.

364
00:25:02,120 --> 00:25:05,360
- It's done.
- The spectrum is quite good.

365
00:25:05,360 --> 00:25:07,040
Ah.

366
00:25:07,040 --> 00:25:10,480
OK, so this is the raw
spectrum that has been taken.

367
00:25:10,480 --> 00:25:13,840
Is there a particular emission
line here that you will

368
00:25:13,840 --> 00:25:16,026
use as your reference
to measure the redshift?

369
00:25:16,031 --> 00:25:16,760
Yeah.

370
00:25:16,760 --> 00:25:20,880
Here, for example, you
have an emission line,

371
00:25:20,880 --> 00:25:24,880
but to obtain real spectra,

372
00:25:24,880 --> 00:25:29,240
you have to clean it to
obtain the final one.

373
00:25:29,240 --> 00:25:32,619
Ah, this is the
cleaned-up version of that.

374
00:25:32,624 --> 00:25:33,800
Yes, of that.

375
00:25:33,800 --> 00:25:37,096
So this is the actual emission
lines from the galaxy...

376
00:25:37,101 --> 00:25:38,200
Yes.

377
00:25:38,200 --> 00:25:41,440
And this one below, I
guess, is the reference?

378
00:25:41,440 --> 00:25:43,480
The reference, correct,

379
00:25:43,480 --> 00:25:46,320
of a galaxy with redshift zero.

380
00:25:46,320 --> 00:25:49,076
OK, so one that isn't
moving away relative to us.

381
00:25:49,081 --> 00:25:50,000
Yes.

382
00:25:50,000 --> 00:25:54,280
And so it is very clear here, if you
compare the top one with this one,

383
00:25:54,280 --> 00:25:57,200
every emission peak is shifted.

384
00:25:57,200 --> 00:25:59,440
It's shifted in the red.

385
00:25:59,440 --> 00:26:03,000
The reference line for
the sample is H-Alpha,

386
00:26:03,000 --> 00:26:07,240
and, from these, you can compute
the redshift of this galaxy.

387
00:26:07,240 --> 00:26:10,440
And can you work out from that how fast

388
00:26:10,440 --> 00:26:12,760
the galaxy is moving away from us?

389
00:26:12,760 --> 00:26:14,800
In principle, you can obtain this.

390
00:26:14,800 --> 00:26:16,800
OK, so what is the formula?

391
00:26:16,800 --> 00:26:20,720
The formula is the difference
between the reference wavelength

392
00:26:20,720 --> 00:26:22,880
and the observed wavelength,

393
00:26:22,880 --> 00:26:27,000
divided by the reference
wavelength and multiplied by C.

394
00:26:27,000 --> 00:26:28,560
This is the Doppler effect.

395
00:26:28,560 --> 00:26:30,840
- Let's see if we can do that roughly.
- Yes.

396
00:26:30,840 --> 00:26:32,240
OK, so this is about...

397
00:26:32,240 --> 00:26:37,440
7,200, approximate.

398
00:26:37,440 --> 00:26:38,960
OK.

399
00:26:38,960 --> 00:26:42,440
Minus 6,563.

400
00:26:42,440 --> 00:26:44,640
- ..63. - OK. - Over...

401
00:26:44,640 --> 00:26:46,640
6,563.

402
00:26:46,640 --> 00:26:48,736
And that is the fraction
of the speed of light?

403
00:26:48,741 --> 00:26:49,440
Yes.

404
00:26:49,440 --> 00:26:51,760
OK, so, I might as well do this.

405
00:26:51,760 --> 00:26:54,400
I should do it with my calculator, but...

406
00:26:54,400 --> 00:26:56,240
So...

407
00:27:02,680 --> 00:27:06,240
OK. So then that we divide by 6,563.

408
00:27:06,240 --> 00:27:09,320
OK, so it is roughly 0.1
the speed of light.

409
00:27:11,360 --> 00:27:16,200
So it is about 30,000 km/s, yes?

410
00:27:16,200 --> 00:27:17,760
- Correct.
- Thank you.

411
00:27:19,080 --> 00:27:20,280
OK.

412
00:27:20,280 --> 00:27:22,480
I'm actually quite pleased
at my maths here,

413
00:27:22,480 --> 00:27:24,640
because I was under pressure.

414
00:27:24,640 --> 00:27:30,160
So, this galaxy is 1.5 billion light
years away from the Milky Way

415
00:27:30,160 --> 00:27:32,120
and, from the redshift,

416
00:27:32,120 --> 00:27:35,200
we have worked out it
is moving away from us

417
00:27:35,200 --> 00:27:37,160
at 1/10 the speed of light.

418
00:27:37,160 --> 00:27:40,880
That means it is moving
away from us at three...

419
00:27:40,880 --> 00:27:44,080
At, sorry, 30,000 km/s.

420
00:27:45,960 --> 00:27:47,640
Boom.

421
00:27:47,640 --> 00:27:48,920
Science.

422
00:27:53,400 --> 00:27:56,080
Once he had calculated
the speed of the galaxy,

423
00:27:56,080 --> 00:27:58,800
Hubble then measured how far away it was.

424
00:28:04,680 --> 00:28:07,280
Once Hubble had both his measurements,

425
00:28:07,280 --> 00:28:12,080
he could start putting them on a
graph of velocity against distance.

426
00:28:12,080 --> 00:28:14,680
Now, he made 46 different measurements

427
00:28:14,680 --> 00:28:18,000
and, when he put them on the graph,
he noticed a pattern emerging.

428
00:28:18,000 --> 00:28:21,080
He could draw a line
through all these points -

429
00:28:21,080 --> 00:28:23,600
each one of them is an individual galaxy.

430
00:28:23,600 --> 00:28:26,720
He noticed a connection
between the velocity

431
00:28:26,720 --> 00:28:28,440
and the distance of a galaxy.

432
00:28:28,440 --> 00:28:31,080
In fact, the further away it was,

433
00:28:31,080 --> 00:28:33,520
the faster it was moving away from us.

434
00:28:36,160 --> 00:28:40,600
In a stable universe, the speeds
of galaxies should appear random.

435
00:28:42,120 --> 00:28:44,600
You wouldn't expect a clear relationship

436
00:28:44,600 --> 00:28:47,680
between the distance of a
galaxy and its velocity.

437
00:28:49,520 --> 00:28:53,640
Hubble's graph showed that
the universe was expanding,

438
00:28:53,640 --> 00:28:56,720
which has profound
implications for the idea

439
00:28:56,720 --> 00:28:58,640
of a beginning to the universe.

440
00:29:01,160 --> 00:29:04,200
What this means is that it is
not just that the galaxies

441
00:29:04,200 --> 00:29:07,120
are all speeding away from
us and from each other

442
00:29:07,120 --> 00:29:09,680
but that, if you could wind the clock back,

443
00:29:09,680 --> 00:29:12,960
there would have been a time when
they were all squeezed together

444
00:29:12,960 --> 00:29:14,280
in the same place.

445
00:29:23,360 --> 00:29:25,960
Here, finally, was the first observation,

446
00:29:25,960 --> 00:29:29,880
the first piece of evidence that
Lemaitre's idea of a moment

447
00:29:29,880 --> 00:29:33,680
of creation, of a universe
evolving from a Big Bang,

448
00:29:33,680 --> 00:29:35,080
might be correct.

449
00:29:51,120 --> 00:29:54,440
Thanks to Hubble's work, Georges Lemaitre,

450
00:29:54,440 --> 00:29:56,640
the unknown Belgian cleric,

451
00:29:56,640 --> 00:30:00,480
the theoretician without proper
international credentials,

452
00:30:00,480 --> 00:30:03,640
the man whose physics
Einstein called abominable,

453
00:30:03,640 --> 00:30:07,640
was belatedly rightly
recognised for his bold theory.

454
00:30:10,600 --> 00:30:12,280
Most significantly,

455
00:30:12,280 --> 00:30:16,560
the biggest name in physics came
around to this revolutionary idea.

456
00:30:19,640 --> 00:30:22,920
In 1931, on a visit to
Hubble's observatory,

457
00:30:22,920 --> 00:30:28,160
Einstein publicly endorsed the Big
Bang expanding universe model.

458
00:30:28,160 --> 00:30:30,360
"The redshifts of distant nebulae

459
00:30:30,360 --> 00:30:34,520
"has smashed my old construction
like a hammer blow," he said.

460
00:30:34,520 --> 00:30:39,760
Einstein dropped the cosmological constant.
He even wrote to Lemaitre,

461
00:30:39,760 --> 00:30:43,880
"Ever since I introduced the term,
I have had a bad conscience.

462
00:30:43,880 --> 00:30:46,640
"I am unable to believe
that such an ugly thing

463
00:30:46,640 --> 00:30:49,440
"should be realised in nature."

464
00:30:49,440 --> 00:30:52,200
It must have been quite an
absolution for Lemaitre.

465
00:30:52,200 --> 00:30:56,040
Having been practically cast out
into the scientific wilderness,

466
00:30:56,040 --> 00:31:00,120
he was now firmly at the centre
of a cosmological revolution.

467
00:31:08,360 --> 00:31:12,240
The idea of the Big Bang was
finally gaining traction.

468
00:31:14,640 --> 00:31:17,360
But, despite Einstein's seal of approval,

469
00:31:17,360 --> 00:31:20,040
and the observations of Hubble,

470
00:31:20,040 --> 00:31:22,080
the argument was far from over.

471
00:31:31,200 --> 00:31:33,480
There were still significant objections

472
00:31:33,480 --> 00:31:36,920
if the idea of a Big Bang
was to be widely accepted.

473
00:31:36,920 --> 00:31:40,640
A scientific theory of creation
isn't just about explaining

474
00:31:40,640 --> 00:31:42,680
the expansion of the universe -

475
00:31:42,680 --> 00:31:45,960
there were more profound issues to resolve.

476
00:31:47,720 --> 00:31:53,120
The problem was, the Big Bang raised
as many questions as it answered.

477
00:31:53,120 --> 00:31:56,920
Like, if the universe had
erupted from a single point,

478
00:31:56,920 --> 00:31:59,480
where did all the matter come from?

479
00:32:04,160 --> 00:32:07,400
To go further, the Big Bang
theory needed to explain

480
00:32:07,400 --> 00:32:10,240
how matter itself had been formed.

481
00:32:13,560 --> 00:32:16,240
Well, before that could be
answered, we need to know

482
00:32:16,240 --> 00:32:19,920
what the universe is actually made
of - the elemental building blocks.

483
00:32:19,920 --> 00:32:23,080
And working that out took an
incredible bit of insight

484
00:32:23,080 --> 00:32:26,880
by a remarkable woman - Cecilia Payne.

485
00:32:26,880 --> 00:32:30,400
She studied at Cambridge University,
but wasn't awarded a degree,

486
00:32:30,400 --> 00:32:32,680
because, well, she was a woman.

487
00:32:32,680 --> 00:32:34,360
So, to continue to her studies,

488
00:32:34,360 --> 00:32:36,680
she needed to go somewhere
more enlightened.

489
00:32:36,680 --> 00:32:38,720
She left England for America

490
00:32:38,720 --> 00:32:43,080
and it was there that she revealed
the composition of the universe.

491
00:32:55,360 --> 00:32:58,680
If you were to ask someone what
the most common elements were,

492
00:32:58,680 --> 00:33:01,520
an atmospheric scientist
might say nitrogen.

493
00:33:01,520 --> 00:33:04,880
After all, it makes up more than
three quarters of the atmosphere.

494
00:33:04,880 --> 00:33:10,640
A geologist might say silicon
or iron or oxygen...

495
00:33:10,640 --> 00:33:13,960
which all seems very
quaint and Earth-centric

496
00:33:13,960 --> 00:33:16,000
and really rather parochial.

497
00:33:27,920 --> 00:33:31,480
So, astronomers thought it
better to look at the sun.

498
00:33:35,280 --> 00:33:38,600
Which makes sense, given
that most of what we see

499
00:33:38,600 --> 00:33:41,200
when we look out into the cosmos is stars.

500
00:33:46,000 --> 00:33:48,960
The first attempts to analyse
the composition of the sun

501
00:33:48,960 --> 00:33:51,400
were done with a set-up rather like this.

502
00:33:51,400 --> 00:33:53,000
Well, not exactly like this -

503
00:33:53,000 --> 00:33:56,240
this is a cutting-edge
21st-century solar telescope.

504
00:33:56,240 --> 00:33:59,240
But the basic idea was exactly the same.

505
00:34:08,800 --> 00:34:10,680
The basic idea's very simple.

506
00:34:10,680 --> 00:34:13,960
The sun's light is reflected
off this mirror here,

507
00:34:13,960 --> 00:34:17,080
up into a second mirror...

508
00:34:17,080 --> 00:34:20,400
where it bounces off, down
through the top of the tower,

509
00:34:20,400 --> 00:34:23,080
all the way to the bottom,
ten storeys down,

510
00:34:23,080 --> 00:34:27,880
where it's focused and split
into a spectrum and analysed.

511
00:34:45,960 --> 00:34:48,440
This is the control room
of the solar telescope.

512
00:34:48,440 --> 00:34:51,120
The base of the telescope is over there.

513
00:34:51,120 --> 00:34:54,960
And here, I've got a live
feed image of the sun.

514
00:34:54,960 --> 00:34:58,320
And what I've got up here
is a zoomed-in section

515
00:34:58,320 --> 00:35:00,760
of the spectrum of the
light coming from the sun.

516
00:35:00,760 --> 00:35:02,640
Now, it's in black and white,

517
00:35:02,640 --> 00:35:06,080
but it actually corresponds to
the green part of the spectrum.

518
00:35:06,080 --> 00:35:10,320
These two thick dark lines
correspond to the element iron.

519
00:35:10,320 --> 00:35:13,240
They tell us there's iron in the sun.

520
00:35:13,240 --> 00:35:16,680
Now, here I have the spectrum
in much more detail,

521
00:35:16,680 --> 00:35:19,680
and these two lines
correspond to these two dips

522
00:35:19,680 --> 00:35:21,600
in the absorption spectrum

523
00:35:21,600 --> 00:35:25,200
at very specific wavelengths. This is iron.

524
00:35:25,200 --> 00:35:29,040
If I look at different parts of the
spectrum, I can see other elements.

525
00:35:29,040 --> 00:35:34,600
This big dip here is hydrogen.
These two dips represent oxygen.

526
00:35:34,600 --> 00:35:38,120
And this dip corresponds
to the element magnesium.

527
00:35:39,880 --> 00:35:42,720
All these dips and lines in the spectrum

528
00:35:42,720 --> 00:35:47,240
indicate the presence of these
elements in the sun's atmosphere.

529
00:35:47,240 --> 00:35:51,080
Effectively, a fingerprint
of the sun's composition.

530
00:35:53,800 --> 00:35:57,040
To a geologist, these elements
are all very familiar.

531
00:35:57,040 --> 00:36:00,440
It appears, at first glance, that
the sun is made of the same stuff

532
00:36:00,440 --> 00:36:05,280
as the Earth, that the sun
is simply a very hot rock.

533
00:36:14,800 --> 00:36:16,960
And that would have been that

534
00:36:16,960 --> 00:36:20,240
were it not for the
insight of Cecilia Payne.

535
00:36:23,040 --> 00:36:27,080
She realised that the spectrographs
were being affected by processes

536
00:36:27,080 --> 00:36:28,960
in the sun's atmosphere.

537
00:36:32,560 --> 00:36:36,400
These would distort the apparent
abundance of the elements

538
00:36:36,400 --> 00:36:37,880
that make up the sun.

539
00:36:40,120 --> 00:36:43,880
So, she recalculated the relative
abundances of the elements

540
00:36:43,880 --> 00:36:47,480
and discovered that the sun
was composed almost entirely

541
00:36:47,480 --> 00:36:49,960
of just two elements -

542
00:36:49,960 --> 00:36:52,200
hydrogen and helium.

543
00:36:52,200 --> 00:36:55,960
All the other elements -
carbon, oxygen, sodium, iron -

544
00:36:55,960 --> 00:36:58,520
that made the sun seem so Earth-like

545
00:36:58,520 --> 00:37:02,280
amounted to just a tiny
fraction of its composition.

546
00:37:02,280 --> 00:37:04,520
When she first presented this result,

547
00:37:04,520 --> 00:37:06,360
it was considered impossible.

548
00:37:06,360 --> 00:37:08,800
In fact, when she wrote up her work,

549
00:37:08,800 --> 00:37:12,760
she was persuaded to add the comment
that these calculated abundances

550
00:37:12,760 --> 00:37:17,080
of hydrogen and helium were
almost certainly not true.

551
00:37:18,920 --> 00:37:22,520
The idea was only accepted
some four years later,

552
00:37:22,520 --> 00:37:25,640
when the director of a
prestigious observatory

553
00:37:25,640 --> 00:37:31,080
arrived at exactly the same
conclusion by different means.

554
00:37:31,080 --> 00:37:33,960
Ironically, this director
was the very same man

555
00:37:33,960 --> 00:37:38,040
who'd initially dismissed Payne's
work as clearly impossible.

556
00:37:41,120 --> 00:37:46,360
Payne's revelation about the ratio
of hydrogen and helium was found

557
00:37:46,360 --> 00:37:51,400
to be remarkably consistent for
almost every star in the galaxy.

558
00:37:51,400 --> 00:37:54,040
That led to a big conclusion.

559
00:37:54,040 --> 00:37:57,840
The universe is dominated by
just two elements, the simplest

560
00:37:57,840 --> 00:38:01,560
and lightest elements -
hydrogen and helium.

561
00:38:01,560 --> 00:38:06,120
Together, they make up more than 98%
of all the matter in the universe.

562
00:38:06,120 --> 00:38:08,400
All the other elements that
are so important to us -

563
00:38:08,400 --> 00:38:13,120
like carbon, oxygen, iron
- amount to less than 2%.

564
00:38:16,520 --> 00:38:20,240
So now the challenge for
supporters of the Big Bang theory

565
00:38:20,240 --> 00:38:22,360
was very clear and simple -

566
00:38:22,360 --> 00:38:26,040
could the Big Bang theory
explain the creation

567
00:38:26,040 --> 00:38:31,840
AND the observed ratios of hydrogen
and helium found in the stars?

568
00:38:40,560 --> 00:38:45,480
But to answer that would require
a fundamental shift of emphasis.

569
00:38:48,920 --> 00:38:53,160
Rather than consider the almost
infinite vastness of the universe,

570
00:38:53,160 --> 00:38:55,480
it was necessary to consider

571
00:38:55,480 --> 00:38:58,880
the infinitesimally small
world of the atom.

572
00:38:58,880 --> 00:39:01,480
And that required, not an astronomer,

573
00:39:01,480 --> 00:39:04,920
but an entirely different
kind of physicist.

574
00:39:04,920 --> 00:39:07,720
George Gamow was a Russian
nuclear physicist

575
00:39:07,720 --> 00:39:12,080
and an enthusiastic advocate
of the Big Bang idea.

576
00:39:12,080 --> 00:39:16,360
He turned his attention to the
earliest moments of the universe.

577
00:39:22,840 --> 00:39:24,400
Here, he felt,

578
00:39:24,400 --> 00:39:27,960
was where the answer to the
composition of the universe lay.

579
00:39:27,960 --> 00:39:32,640
This was when he believed hydrogen
and helium were first forged,

580
00:39:32,640 --> 00:39:35,680
and he proposed it would
have happened very soon

581
00:39:35,680 --> 00:39:38,640
after the birth of the universe.

582
00:39:38,640 --> 00:39:41,720
He set about building a mathematical model

583
00:39:41,720 --> 00:39:45,640
of the earliest stages of the universe.

584
00:39:45,640 --> 00:39:48,880
He was thinking about the universe
in terms of seconds and minutes,

585
00:39:48,880 --> 00:39:51,200
rather than billions of years.

586
00:39:51,200 --> 00:39:54,000
And he recruited a young protege,

587
00:39:54,000 --> 00:39:57,680
this chap, Ralph Alpher, to help him.

588
00:39:57,680 --> 00:40:00,560
After years of hard work, some
of which, according to Alpher,

589
00:40:00,560 --> 00:40:03,360
were aided by hard drinking in a bar,

590
00:40:03,360 --> 00:40:05,360
they presented their idea.

591
00:40:06,640 --> 00:40:09,880
By rewinding the universe, it
was clear to them that there

592
00:40:09,880 --> 00:40:13,800
would have been a time when the
early universe was incredibly dense

593
00:40:13,800 --> 00:40:16,160
and phenomenally hot.

594
00:40:16,160 --> 00:40:19,000
At this stage, which they
calculated to be just three minutes

595
00:40:19,000 --> 00:40:22,160
after the Big Bang, the
universe would have been so hot

596
00:40:22,160 --> 00:40:24,560
that atoms themselves couldn't exist,

597
00:40:24,560 --> 00:40:26,960
only their constituent parts,

598
00:40:26,960 --> 00:40:30,240
a kind of superheated primordial soup

599
00:40:30,240 --> 00:40:33,040
of protons, neutrons and electrons.

600
00:40:33,040 --> 00:40:35,960
They even gave this soup a name - ylem,

601
00:40:35,960 --> 00:40:38,360
from an old English word for matter.

602
00:40:40,880 --> 00:40:45,120
Then came the crucial moment...

603
00:40:45,120 --> 00:40:48,160
a time when conditions
were right for the nuclei

604
00:40:48,160 --> 00:40:50,480
of the first elements to be forged.

605
00:40:50,480 --> 00:40:52,560
In a short period of time,

606
00:40:52,560 --> 00:40:55,240
which they estimated to
be less than 15 minutes,

607
00:40:55,240 --> 00:41:00,000
hydrogen nuclei proton were
coming together to form helium,

608
00:41:00,000 --> 00:41:02,440
in the process of nuclear fusion.

609
00:41:05,160 --> 00:41:09,720
Moreover, the ratios of hydrogen and
helium predicted by their model

610
00:41:09,720 --> 00:41:13,040
matched that measured in the stars.

611
00:41:16,520 --> 00:41:20,240
They announced their results
in a paper published in 1948.

612
00:41:22,000 --> 00:41:24,560
However, Gamow added another
author to the paper -

613
00:41:24,560 --> 00:41:26,880
the famous nuclear physicist, Hans Bethe,

614
00:41:26,880 --> 00:41:28,720
who had nothing to do with the work.

615
00:41:28,720 --> 00:41:30,600
Gamow added his name for a laugh.

616
00:41:30,600 --> 00:41:32,880
He thought it made a good science pun,

617
00:41:32,880 --> 00:41:38,080
because the authors of the paper now
read, "Alpher, Bethe and Gamow."

618
00:41:38,080 --> 00:41:41,440
The young Alpher, however, was less
amused to be sharing the credit

619
00:41:41,440 --> 00:41:44,720
with someone who'd done no work.

620
00:41:44,720 --> 00:41:47,280
By way of reconciliation, the story goes,

621
00:41:47,280 --> 00:41:50,040
Gamow produced a bottle
of Cointreau for Alpher

622
00:41:50,040 --> 00:41:53,880
but with the label changed to read, "Ylem."

623
00:41:56,880 --> 00:42:01,080
The ability to make calculations
that explained the origins of matter

624
00:42:01,080 --> 00:42:06,720
in the first few minutes after a
Big Bang was remarkable in itself.

625
00:42:06,720 --> 00:42:09,400
But there was a very significant prediction

626
00:42:09,400 --> 00:42:11,880
that emerged from their work.

627
00:42:11,880 --> 00:42:15,920
A prediction that had the
potential to deliver the proof

628
00:42:15,920 --> 00:42:19,720
that the universe had
begun with a Big Bang.

629
00:42:19,720 --> 00:42:22,880
Alpher continued to study the
early evolving universe,

630
00:42:22,880 --> 00:42:25,160
focusing on what happened next.

631
00:42:25,160 --> 00:42:28,720
He pictured the universe at
this stage as a seething fog

632
00:42:28,720 --> 00:42:31,280
of free electrons and atomic nuclei.

633
00:42:31,280 --> 00:42:34,400
Then it dropped to a critical temperature,

634
00:42:34,400 --> 00:42:37,720
a temperature cool enough
for electrons to latch on

635
00:42:37,720 --> 00:42:41,000
to the nuclei of hydrogen and helium.

636
00:42:41,000 --> 00:42:43,000
At this precise point,

637
00:42:43,000 --> 00:42:47,120
light was released to travel
freely throughout the universe.

638
00:42:47,120 --> 00:42:49,680
The first light of creation.

639
00:42:57,200 --> 00:43:00,360
This might have remained nothing
more than an academic curiosity

640
00:43:00,360 --> 00:43:02,800
had it not been for Alpher's insight.

641
00:43:02,800 --> 00:43:05,320
You see, he realised that
this light from the beginning

642
00:43:05,320 --> 00:43:08,040
of the universe should
still be reaching us now,

643
00:43:08,040 --> 00:43:09,800
after billions of years.

644
00:43:09,800 --> 00:43:13,720
Very weak, very faint, but
observable in all directions.

645
00:43:13,720 --> 00:43:17,560
He calculated that the expansion of
the universe should be stretching

646
00:43:17,560 --> 00:43:21,640
the wavelength of this light beyond
the range of the visible spectrum

647
00:43:21,640 --> 00:43:25,080
and should now be arriving
as microwave radiation.

648
00:43:28,280 --> 00:43:32,160
So, find this predicted
ancient microwave signature

649
00:43:32,160 --> 00:43:35,240
and it will prove, not just the
theory of the early evolution

650
00:43:35,240 --> 00:43:40,080
of the universe, but the entire
Big Bang theory itself. Simple.

651
00:43:41,680 --> 00:43:44,320
The problem was, this was the late 1940s

652
00:43:44,320 --> 00:43:48,520
and no-one had any way of
detecting such a weak signal.

653
00:43:48,520 --> 00:43:51,120
The acid test was quietly forgotten.

654
00:43:56,320 --> 00:43:59,600
Supporters of the Big Bang
now had the prediction

655
00:43:59,600 --> 00:44:03,040
and observation of an expanding universe.

656
00:44:04,920 --> 00:44:07,560
And a theory for how elements were forged

657
00:44:07,560 --> 00:44:10,360
in the first few minutes
after the Big Bang.

658
00:44:13,080 --> 00:44:17,000
But without the clinching evidence
for this, the argument over

659
00:44:17,000 --> 00:44:20,200
whether the Big Bang theory
was correct rumbled on.

660
00:44:24,400 --> 00:44:27,880
The opponents of the Big Bang
continually tweaked and adjusted

661
00:44:27,880 --> 00:44:32,640
their theories to make their idea
of an eternal and infinite universe

662
00:44:32,640 --> 00:44:34,480
fit the new observations.

663
00:44:34,480 --> 00:44:39,160
The scientific community was
still pretty evenly split.

664
00:44:40,280 --> 00:44:44,160
Conclusive proof of the Big Bang
theory would eventually emerge

665
00:44:44,160 --> 00:44:46,040
some 15 years later.

666
00:44:46,040 --> 00:44:48,800
It would be revealed quite unexpectedly

667
00:44:48,800 --> 00:44:52,120
by two young radio engineers.

668
00:44:54,400 --> 00:44:58,280
In 1964, Arno Penzias and Robert Wilson -

669
00:44:58,280 --> 00:45:00,520
that's Penzias on the right there -

670
00:45:00,520 --> 00:45:04,680
discovered something so momentous,
it won them the Nobel Prize.

671
00:45:09,000 --> 00:45:14,040
This telescope is dedicated to
study their accidental discovery.

672
00:45:15,920 --> 00:45:20,040
In 1964, Penzias and Wilson were
working at the Bell Laboratories

673
00:45:20,040 --> 00:45:23,160
in the US where they were
given this, a bizarre

674
00:45:23,160 --> 00:45:26,640
and obsolete piece of kit to play with.

675
00:45:26,640 --> 00:45:29,920
It looks, for all the world,
like an enormous ear trumpet.

676
00:45:29,920 --> 00:45:33,120
But when they turned their telescope on,

677
00:45:33,120 --> 00:45:38,000
they found that the sky was
saturated with microwave radiation.

678
00:45:40,320 --> 00:45:43,520
All warm bodies emit microwave radiation,

679
00:45:43,520 --> 00:45:47,560
whether it's from the atmosphere
or from the instrument itself.

680
00:45:47,560 --> 00:45:52,000
And today's mobile communications
flood the sky with it.

681
00:45:52,000 --> 00:45:57,360
FAINT STATIC

682
00:45:57,360 --> 00:46:00,520
So, before they could do
any useful measurements,

683
00:46:00,520 --> 00:46:03,760
they had to calibrate
their Horn Antenna to see

684
00:46:03,760 --> 00:46:06,320
if they could reduce this "noise."

685
00:46:06,320 --> 00:46:09,120
FAINT STATIC

686
00:46:09,120 --> 00:46:11,760
Even after accounting for the atmosphere

687
00:46:11,760 --> 00:46:13,320
and their instrumentation -

688
00:46:13,320 --> 00:46:16,080
of course, there were no mobile
phones to worry about back then -

689
00:46:16,080 --> 00:46:18,320
they were still left with this persistent

690
00:46:18,320 --> 00:46:20,920
and deeply irritating background noise.

691
00:46:20,920 --> 00:46:23,640
It was registered on their
instruments as a radiation

692
00:46:23,640 --> 00:46:27,840
with a constant temperature of
three degrees above absolute zero,

693
00:46:27,840 --> 00:46:30,920
a microwave hiss that
they couldn't get rid of

694
00:46:30,920 --> 00:46:32,920
no matter what they tried.

695
00:46:34,320 --> 00:46:39,360
FAINT STATIC

696
00:46:39,360 --> 00:46:42,840
Even more annoying for them was
the fact that it seemed to be

697
00:46:42,840 --> 00:46:46,040
everywhere they pointed their
celestial ear trumpet.

698
00:46:48,760 --> 00:46:52,480
They were about to give up when
Penzias attended a meeting

699
00:46:52,480 --> 00:46:56,120
where he casually mentioned
this irritant to a colleague.

700
00:46:56,120 --> 00:46:58,880
A few weeks later, the same
colleague phoned him up and said

701
00:46:58,880 --> 00:47:01,240
he knew of some researchers in Princeton

702
00:47:01,240 --> 00:47:04,360
who are looking for just such a signal.

703
00:47:06,600 --> 00:47:10,200
Unwittingly, Penzias and
Wilson had stumbled upon

704
00:47:10,200 --> 00:47:13,360
that predicted radiation
- Alpher's burst of light

705
00:47:13,360 --> 00:47:15,920
from the early evolution of the universe.

706
00:47:15,920 --> 00:47:20,080
Here, at last, was proof
of the Big Bang theory.

707
00:47:31,600 --> 00:47:35,000
It's quite remarkable to think
that this microwave radiation

708
00:47:35,000 --> 00:47:37,800
has travelled across the
furthest reaches of space,

709
00:47:37,800 --> 00:47:40,480
from 13.8 billion years ago

710
00:47:40,480 --> 00:47:44,000
when that first light from
the Big Bang was released.

711
00:47:44,000 --> 00:47:46,920
As Penzias himself said,
when you go outside,

712
00:47:46,920 --> 00:47:51,200
you're getting a tiny bit of warmth
from the Big Bang on your scalp.

713
00:47:51,200 --> 00:47:54,200
And, yes, I probably feel
it a bit more than most.

714
00:47:58,200 --> 00:48:02,360
Almost 40 years after
Lemaitre first postulated it,

715
00:48:02,360 --> 00:48:07,560
the idea of the Big Bang had finally
entered the scientific mainstream.

716
00:48:10,960 --> 00:48:14,920
But the discovery of this cosmic
microwave background radiation,

717
00:48:14,920 --> 00:48:19,240
the CMB, and the proof of
the Big Bang theory itself,

718
00:48:19,240 --> 00:48:21,600
isn't the end of our story.

719
00:48:28,600 --> 00:48:32,920
We've probed back to the first
few minutes after the Big Bang.

720
00:48:37,200 --> 00:48:40,680
And beyond this lies a new
frontier of knowledge.

721
00:49:01,640 --> 00:49:04,720
There are still very big questions
to resolve about the beginning

722
00:49:04,720 --> 00:49:06,520
of the universe, questions like,

723
00:49:06,520 --> 00:49:09,000
"Where did all the matter
itself come from?"

724
00:49:09,000 --> 00:49:12,360
And "How do you get
something from nothing?"

725
00:49:12,360 --> 00:49:15,560
The answers to these
questions lie further back,

726
00:49:15,560 --> 00:49:18,120
hidden behind the curtain of the CMB.

727
00:49:18,120 --> 00:49:21,680
Their secrets lie in the
primordial universe,

728
00:49:21,680 --> 00:49:25,200
within the very first
second of its existence.

729
00:49:31,360 --> 00:49:35,400
This is where the edge of
our understanding now lies,

730
00:49:35,400 --> 00:49:39,880
and this is where scientists
are focusing their efforts...

731
00:49:39,880 --> 00:49:42,040
not by looking into the skies,

732
00:49:42,040 --> 00:49:45,520
but here on the border of
Switzerland and France.

733
00:49:48,280 --> 00:49:50,480
More specifically, at CERN,

734
00:49:50,480 --> 00:49:53,640
with the largest particle
accelerator in the world,

735
00:49:53,640 --> 00:49:57,320
the Large Hadron Collider, or LHC.

736
00:50:00,080 --> 00:50:03,760
Now, you might be wondering what a
particle accelerator has to do with

737
00:50:03,760 --> 00:50:06,720
the early universe, because the
connection between the two

738
00:50:06,720 --> 00:50:08,240
is far from obvious.

739
00:50:08,240 --> 00:50:11,240
The thing to remember is that,
when the universe was very young,

740
00:50:11,240 --> 00:50:13,840
it was much smaller and so all the matter -

741
00:50:13,840 --> 00:50:16,800
everything that makes up the
stars, the galaxies, black holes -

742
00:50:16,800 --> 00:50:21,040
all had to be confined
into a much smaller space.

743
00:50:21,040 --> 00:50:24,440
At that stage, the universe
was phenomenally hot and,

744
00:50:24,440 --> 00:50:28,080
more significantly, its
energy density was very high.

745
00:50:31,800 --> 00:50:36,240
It was then that the first
matter sprang into existence.

746
00:50:36,240 --> 00:50:40,160
The LHC can't yet replicate that process...

747
00:50:42,920 --> 00:50:45,920
..but it can allow us
to study the properties

748
00:50:45,920 --> 00:50:48,360
of these fundamental particles.

749
00:50:48,360 --> 00:50:52,960
Once a year, the LHC stops its
normal business of colliding

750
00:50:52,960 --> 00:50:56,680
beams of protons, and instead
uses much more massive particles

751
00:50:56,680 --> 00:51:00,600
to create collisions with energies
more than 80 times greater

752
00:51:00,600 --> 00:51:03,640
than that produced from two protons.

753
00:51:03,640 --> 00:51:07,160
They do this by accelerating atoms of lead,

754
00:51:07,160 --> 00:51:09,160
stripped of all their electrons,

755
00:51:09,160 --> 00:51:11,720
up to speeds close to that of light,

756
00:51:11,720 --> 00:51:14,040
and smashing them together.

757
00:51:14,040 --> 00:51:17,280
And that lets us see
something pretty special.

758
00:51:22,520 --> 00:51:26,000
The collisions are so
intense that, for a moment,

759
00:51:26,000 --> 00:51:29,400
we create something unique -

760
00:51:29,400 --> 00:51:34,080
a world not of atoms or
even neutrons and protons -

761
00:51:34,080 --> 00:51:39,240
but of quarks and gluons and leptons
- exotically named particles

762
00:51:39,240 --> 00:51:43,880
that came together to form atoms
in the first millionth of a second

763
00:51:43,880 --> 00:51:49,000
after the Big Bang, and have
been locked away ever since.

764
00:51:49,000 --> 00:51:54,000
Down there, underneath that lead
shielding, we're recreating a stage

765
00:51:54,000 --> 00:51:58,280
in the universe's evolution
called the quark-gluon plasma.

766
00:51:58,280 --> 00:52:02,520
Now, this is the moment immediately
before the quarks become trapped

767
00:52:02,520 --> 00:52:06,160
by the gluons to create
protons and neutrons,

768
00:52:06,160 --> 00:52:09,600
which themselves go on to
form the nuclei of atoms.

769
00:52:09,600 --> 00:52:12,240
The phrase we use - grandly -

770
00:52:12,240 --> 00:52:15,240
is the confinement of the quarks.

771
00:52:23,280 --> 00:52:25,560
To develop the necessary energy,

772
00:52:25,560 --> 00:52:30,680
the lead nuclei are passed through
a chain of smaller accelerators,

773
00:52:30,680 --> 00:52:33,800
gradually ramping up the
energy until they're finally

774
00:52:33,800 --> 00:52:38,480
fed into the largest
accelerator on Earth, the LHC.

775
00:52:38,480 --> 00:52:42,640
Now, the maximum energy a beam
can achieve is directly related

776
00:52:42,640 --> 00:52:44,720
to the size of the accelerator,

777
00:52:44,720 --> 00:52:48,640
and the LHC has a circumference of 27km.

778
00:52:48,640 --> 00:52:51,640
That means the beams here
can achieve an energy

779
00:52:51,640 --> 00:52:55,440
of 1,000 tera-electronvolts.

780
00:52:55,440 --> 00:52:58,800
Now, actually, that's less than
you might imagine, because

781
00:52:58,800 --> 00:53:03,000
it's equivalent to the energy that
a housefly hits a window pane.

782
00:53:03,000 --> 00:53:05,160
But the critical difference here

783
00:53:05,160 --> 00:53:07,760
is that the energy is concentrated,

784
00:53:07,760 --> 00:53:10,240
it's the energy density that's important.

785
00:53:10,240 --> 00:53:14,720
The LHC can squeeze all that energy
down to a space that's less than

786
00:53:14,720 --> 00:53:18,200
a trillionth of the size of a single atom.

787
00:53:19,880 --> 00:53:24,560
This is something that can happen
nowhere else in the known universe.

788
00:53:33,480 --> 00:53:37,120
The two beams of lead nuclei
are travelling around the ring

789
00:53:37,120 --> 00:53:38,920
in opposite directions.

790
00:53:38,920 --> 00:53:42,720
They're meeting deep underneath
this control room at the detector.

791
00:53:42,720 --> 00:53:46,640
We can see live feed pictures of
the detector up on that screen.

792
00:53:46,640 --> 00:53:47,880
Now, underneath us,

793
00:53:47,880 --> 00:53:53,680
they're travelling at a speed
of 99.9998% the speed of light.

794
00:53:53,680 --> 00:53:57,840
That means they're covering the
full 27km circumference of the ring

795
00:53:57,840 --> 00:54:01,360
more than 11,000 times per second.

796
00:54:01,360 --> 00:54:03,960
When the beams reach maximum energy -

797
00:54:03,960 --> 00:54:06,680
and we can see up there, it says
"iron physics stable beams" -

798
00:54:06,680 --> 00:54:08,880
that means they can be crossed.

799
00:54:08,880 --> 00:54:10,560
Just like in Ghostbusters.

800
00:54:10,560 --> 00:54:14,640
At that point, a tiny fraction
of the lead nuclei will collide

801
00:54:14,640 --> 00:54:18,480
and create a super-hot,
super-dense fireball

802
00:54:18,480 --> 00:54:23,480
with a temperature 400,000 times
hotter than the centre of the sun,

803
00:54:23,480 --> 00:54:26,440
and a density that would
be equivalent to squeezing

804
00:54:26,440 --> 00:54:30,120
the whole of Mont Blanc down
to the size of a grape.

805
00:54:42,840 --> 00:54:46,480
That looks like a fantastic image there.

806
00:54:46,480 --> 00:54:49,880
- Can you tell me what we're seeing?
- It's amazing, actually, isn't it?

807
00:54:49,880 --> 00:54:54,120
It's literally tens of thousands of
particles and antimatter particles

808
00:54:54,120 --> 00:54:56,696
flying out - this kind of
aftermath of this explosion.

809
00:54:56,701 --> 00:54:57,560
Right.

810
00:54:57,560 --> 00:55:00,600
So the coloured particle trails here

811
00:55:00,600 --> 00:55:03,600
AREN'T the quarks and gluons themselves,

812
00:55:03,600 --> 00:55:08,520
but evidence of the quark-gluon
plasma created by the collision.

813
00:55:08,520 --> 00:55:11,600
We have to infer its properties
from looking at the debris

814
00:55:11,600 --> 00:55:15,720
that flies out. It's a bit like
working out how an aircraft works

815
00:55:15,720 --> 00:55:19,080
by looking at the debris of a plane crash.
That's what we see.

816
00:55:19,080 --> 00:55:22,960
What I find amazing is, what we're
doing here is trying to recreate

817
00:55:22,960 --> 00:55:27,960
that moment in the early universe
where the quarks and gluons

818
00:55:27,960 --> 00:55:30,480
were all free to float around,
cos the energy was so high,

819
00:55:30,480 --> 00:55:33,720
and then it cooled and they stacked
together. You're doing the opposite.

820
00:55:33,720 --> 00:55:36,640
We're starting with normal
matter, smashing it together,

821
00:55:36,640 --> 00:55:41,160
and going back to that
unconfined state, that plasma.

822
00:55:41,160 --> 00:55:43,560
Yeah. I like to think about
it as a time machine.

823
00:55:43,560 --> 00:55:45,640
We're actually winding back the clock.

824
00:55:45,640 --> 00:55:49,520
And this is the only way that we can
study the properties of free quarks,

825
00:55:49,520 --> 00:55:53,080
because these quarks have been
imprisoned inside particles

826
00:55:53,080 --> 00:55:56,520
like protons and neutrons
for 13.8 billion years.

827
00:55:56,520 --> 00:56:00,120
That's pretty incredible, isn't it?
Finally, after 13.8 billion years,

828
00:56:00,120 --> 00:56:01,720
you can set these quarks free -

829
00:56:01,720 --> 00:56:04,480
- even if it's for a fraction of a second.
- Yes.

830
00:56:06,920 --> 00:56:11,240
While we don't yet know how
matter sprang into existence,

831
00:56:11,240 --> 00:56:13,680
studying these collisions allows us

832
00:56:13,680 --> 00:56:17,720
to make the first tentative
steps towards that discovery.

833
00:56:19,280 --> 00:56:22,840
What we've just witnessed is the
earliest stages of the universe

834
00:56:22,840 --> 00:56:26,400
that anyone - anywhere -
has been able to observe.

835
00:56:26,400 --> 00:56:30,400
It's the closet we've got to
the moment of the Big Bang.

836
00:56:30,400 --> 00:56:33,000
And, let's face it, it's not bad.

837
00:56:33,000 --> 00:56:36,560
One millionth of a second
after the Big Bang itself.

838
00:56:40,040 --> 00:56:42,280
Even going this far back in time

839
00:56:42,280 --> 00:56:45,880
still leaves physics with
unanswered questions.

840
00:56:50,560 --> 00:56:54,240
Beyond this is where some of the
deeper mysteries of the universe

841
00:56:54,240 --> 00:56:59,520
are hiding. How the fundamental
forces that bind matter together -

842
00:56:59,520 --> 00:57:02,400
gravity, electromagnetism
and the nuclear forces -

843
00:57:02,400 --> 00:57:04,800
are connected to each other.

844
00:57:04,800 --> 00:57:07,600
How the particles that
make up matter itself

845
00:57:07,600 --> 00:57:10,600
condensed out of a fog of energy.

846
00:57:10,600 --> 00:57:13,760
How mass is generated from
the force that binds protons

847
00:57:13,760 --> 00:57:15,920
and neutrons together.

848
00:57:15,920 --> 00:57:20,920
And how the universe itself
underwent a super-fast expansion

849
00:57:20,920 --> 00:57:26,240
in one billion-billion-
billion-billionth of a second

850
00:57:26,240 --> 00:57:28,640
to create the structure of the cosmos.

851
00:57:30,480 --> 00:57:34,640
At the moment, we have no way of
observing any of these phenomena.

852
00:57:36,280 --> 00:57:40,480
This is the realm of abstract
theory and speculation.

853
00:57:44,960 --> 00:57:48,080
If we're ever going to replicate
this early stage of the universe's

854
00:57:48,080 --> 00:57:52,960
evolution, we're going to need to
create considerably higher energies.

855
00:57:52,960 --> 00:57:56,200
Frankly, we're going to need
to build a bigger collider.

856
00:57:56,200 --> 00:57:59,640
And that's a problem. And
it's not just one of expense,

857
00:57:59,640 --> 00:58:03,400
although it would be
phenomenally expensive.

858
00:58:03,400 --> 00:58:07,560
No, it's more one of finding
the room to build it.

859
00:58:09,440 --> 00:58:12,880
Remember when I said the energy's
related to the circumference

860
00:58:12,880 --> 00:58:16,680
of the accelerator? Well,
the LHC, down below me,

861
00:58:16,680 --> 00:58:19,800
has a circumference of 27km.

862
00:58:19,800 --> 00:58:22,840
It runs beneath the Jura Mountains

863
00:58:22,840 --> 00:58:26,520
and straddles both France and Switzerland.

864
00:58:26,520 --> 00:58:31,760
In order to look back and observe the
universe at this earliest stage,

865
00:58:31,760 --> 00:58:34,120
well, we'd need to build an accelerator

866
00:58:34,120 --> 00:58:38,080
with a circumference larger
than the orbit of Pluto.

867
00:58:42,600 --> 00:58:45,560
Revealing the origin of the
universe begs another,

868
00:58:45,560 --> 00:58:48,200
even more profound question -

869
00:58:48,200 --> 00:58:50,480
how will it end?

870
00:58:50,480 --> 00:58:54,240
Next time, I discover whether the
universe will end with a bang

871
00:58:54,240 --> 00:58:56,560
or a whimper.

872
00:58:56,560 --> 00:59:00,400
Want to discover more about the
beginnings of the universe?