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Did our universe have a beginning?

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Why is there a universe
like this one?

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If time began at the big bang,
then was there a time before time?

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Why are there rivers and flows
and filaments of galaxies?

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Is there an end of the universe?
Is our universe eternal?

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I'm on tour in Australia,

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talking to audiences and scientists
about two fundamental questions -

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how did the universe begin...

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Like in the big bang,
it feels audacious.

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...and how will it end?

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Life on earth will become
very problematic.

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In the last decade,

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we've been able to probe these ideas
in unprecedented detail.

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So, this IS the oldest light
in the universe.

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This is the story
of our scientific quest

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to understand
the origin of the universe.

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Of all the questions in science,

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the question of the origin
of the universe

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is one that I think needs
no motivation.

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Every human culture
has its own creation story,

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and science is no different.

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For the best part of 100 years,
we've had the theory

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that the universe began
in the big bang.

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But in the last decade or so,

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new precision measurements
of the cosmos,

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coupled with
theoretical developments,

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have given us an unprecedented
and detailed picture

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of the origin of the universe.

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If this were a lesser program,

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we would start it
in a deep voice going,

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"There was a time... with no time."

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"There was a place... not in space."

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"THAT is the time before time"

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"and place without space"

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"that we call the big bang."

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That's not what we're doing, though.

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I think if you ask the question,

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"WHY do you want to know
the origins of the universe?"

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I suppose the answer
has to be curiosity.

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It's surely something that must occur
to everybody at some point -

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why do we exist?

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When I think of a scientist,

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I think of an adult who still has
the soul of curiosity of a child.

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So I think it's very natural to ask,
how did it all get here?

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Indigenous Australians
have been observing the stars

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for more than 40,000 years,

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and, like many ancient cultures,

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have a number of creation stories
based on the night sky.

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It's the story of 'arang' - the emu.

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The emu sacrificed his wings

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and was given an eternal place
in the southern skies.

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Forever you will be seen
running across the night sky

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and marked as 'dyurra' - the stars.

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I've always liked creation stories.

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I like reading about them
from across the world.

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Why do we do it?

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Why do we build telescopes
to look back to the edge of time?

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Why do we measure the expansion rate
of the universe

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and build theories to explain it?

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But the answer is because
that's what we've always done.

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And the evidence for that is

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that every culture you study across
the world has a creation story.

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And the most wonderful thing

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about living in the 21st century,
with modern science,

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is that we also have
a creation story.

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You've probably heard it described
as 'the big bang'.

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But what is the big bang?

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And what do we know about
the origin of the universe?

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With observations
and mathematical theorising,

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we have a good sense that
about 13.8 billion years ago,

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the universe was incredibly dense
and it was incredibly hot.

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Hot! Give me some heat!
Give me some density!

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Give me some violations of
the laws of particle physics.

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It underwent a rapid swelling
that's called the big bang.

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So, what's the big bang?

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And the answer is
I don't know what the big bang is.

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I just know what came after
the big bang,

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where we have a universe
that's expanding very quickly,

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it's really hot.

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These things, we do know.

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It's the things that come after
that we understand.

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You can trace everything back
and you get to a point

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where the universe had to have been
hot and small and dense

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and something happened
that made that expand, right?

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And so that's this idea that
became known as 'the hot big bang'.

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I'm liking the big bang.

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That just feels right.
It feels audacious.

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It's common to think of the big bang
as the start of time itself.

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The moment when everything
came from nothing.

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But there are cosmologists
who think there may be more to it -

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that the thing we used to call
'the big bang'

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was an event
in a pre-existing universe

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and not the beginning at all.

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But how can we be so confident?

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How can we even dare
to speak of things

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that happened
almost 14 billion years ago?

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In 1927,
the astronomer Edwin Hubble noticed

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that the light from distant galaxies
is stretched.

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That means that space is expanding -
our universe is expanding.

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So, you run time backwards
in your mind's eye,

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that means that in the past,

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the distances between the galaxies
was smaller,

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and you can imagine a time
when the distances were so small

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that everything is effectively
on top of each other.

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That implies that our universe
had a beginning,

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there was a day without a yesterday,

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and that is what we call
the big bang.

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More than 30 years after
Hubble made his observations,

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cosmologists remained divided

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about whether the big bang theory
was correct.

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More evidence was needed.

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And it came in the 1960s,

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with the discovery of
a mysterious faint signal.

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We call it the cosmic microwave
background radiation.

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It's seen as a faint glow, coming
literally from everywhere in the sky,

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but not being emitted from any
particular star, galaxy or object.

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So, this is the oldest light
in the universe.

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There are photons that have travelled
13.8 billion years from over there

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and 13.8 billion years
from over there,

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and they're carrying information
about the beginning of time.

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One of the many remarkable things
about the cosmic microwave background

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is the story of its discovery,

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because it was found
entirely by accident.

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We had this result. We couldn't find
any explanation for it.

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We couldn't make it go away. What
were we going to do with this thing?

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So, where did the cosmic microwave
background come from?

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And why do we consider it such strong
evidence for the big bang theory?

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So, the picture is this - the
universe is expanding and cooling.

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In the first few minutes,
it's extremely hot,

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and then the universe is filled
by what's called a plasma -

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so, it's too hot for atoms to form.

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380,000 years after the big bang,
it's cool enough for atoms to form,

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the universe becomes
almost instantly transparent,

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so light can travel
in straight lines,

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and it will continue to travel
in straight lines

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for the rest of the expansion history
of the universe

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and it can enter our telescopes here
on Earth 13.8 billion years later.

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The cosmic microwave background
is considered such strong evidence

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in large part because

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the big bang theory predicted
that it should exist.

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It was first observed
in the mid-1960s,

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and it's only then, really,
just before I was born,

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that the idea that the universe began
at a hot, dense origin

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really took hold.

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It's an almost overwhelming
piece of evidence,

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because you're seeing the afterglow
of that earliest of times.

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We can take pictures of that light
in great detail now.

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We don't see it as a hum.

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We can photograph, essentially,
the universe as it was,

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the whole sky
looking out into the universe,

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and see it as it was
when that first light was released.

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This remarkable baby photograph
of the universe

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confirmed that
we had the basics right.

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But its great detail
presented fresh challenges.

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As we often find with science,

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when you answer one set of questions,
new ones arise.

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This idea that the universe
had a beginning in the big bang

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is in some ways unsatisfactory.

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It raises a series of
childlike questions.

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Like, if the universe
had a beginning,

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then what happened
before the beginning?

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What caused it?

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If time emerged at the big bang,
then was there a time before time?

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How can the universe appear
spontaneously out of nothing at all?

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Was there a before?

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Well, that is
a philosophical question,

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unless you can come up with a theory

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that predicts something that
you can test against observation.

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The clues which point the way
to a theory

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of what came before the big bang

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can be found in problems with
the big bang theory itself.

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There are two problems
with the standard big bang model.

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They're called the horizon problem
and the flatness problem.

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You can picture the horizon problem
as follows.

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If you look at the universe as far
as the eye can see in that direction,

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which is to say
the cosmic microwave background,

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then it's the same temperature
to one part in 100,000

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as the universe as far as the eye
can see in that direction,

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which is the cosmic
microwave background.

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But those two points on the sky
are separated today

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by 90 billion light-years.

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That means if you've got a universe
that's been expanding sedately

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and is only 13.8 billion years old,

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those two points could never have
been in contact with each other.

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Which means there's no explanation

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for how they could be
so precisely the same.

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And then there's
the flatness problem.

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When you look at our universe,
it appears to be completely flat.

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Which seems very strange,

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because it could have been curved
like the surface of a sphere

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or curved like the surface
of a saddle.

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A solution can be found in a theory
known as inflation,

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which suggests that there was a time
in the history of the universe

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when the universe wasn't just
expanding sedately as it is today -

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it was expanding incredibly fast.

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By "fast", I mean
that it was doubling in size

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every 10 to the -37 seconds.

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That's one ten-million-million-
million-million-million-millionths

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of a second.

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Why does that solve
the horizon and flatness problems?

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Well, first of all, it suggests the
universe has to be extremely big -

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way bigger than the piece
we can see today.

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And that means that
it's always gonna look flat.

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Think about an analogy with
the surface of the Earth.

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This little piece of the Earth here
looks flat,

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even though we know
the Earth's curved.

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Why? Because it's very small
compared to the size of the Earth.

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So it is, according to the theory
of inflation, for our universe.

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It also solves our horizon problem,

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because it says that
that piece of the sky,

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which is so far away from that piece,

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were once in contact with each other.

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They could jiggle around
and get to the same temperature,

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but then they were ripped apart.

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It's mind-boggling,

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but it's important to say
that if we are right about inflation,

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then this violent rapid expansion
must have occurred

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BEFORE the thing
we used to call 'the big bang'.

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So, what is our current theory?

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This theory called inflation

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that says there was something
going on before,

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I suppose that thing we used to call
'the big bang', or is that...

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Yeah, yeah, the hot big bang.

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I make that distinction by saying
"hot big bang" versus "big bang",

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because 'hot big bang'
does imply, sort of,

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the universe is in
a fireball kind of state.

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Yeah.

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Yeah, the reason we know
that something happened before

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is we can look at
that primordial fireball state.

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Like, we can actually see it.

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Because we can see
the cosmic microwave background,

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which is the, sort of, afterglow
of that time

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when the whole universe
was hot and dense.

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The, sort of, important point there
is that it was expanding so fast

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that things that were connected
to each other before,

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close enough together
to communicate,

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to come into equilibrium,
to be the same temperature,

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rapidly come out of contact.
Yeah.

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And so that's why now
when we look at the sky

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and we see that two different parts
of the universe

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that should never have been
in contact with each other

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are the same temperature,

243
00:15:21,289 --> 00:15:23,728
it's because you can dial back
the expansion

244
00:15:23,729 --> 00:15:26,128
and find that they were
never in contact,

245
00:15:26,129 --> 00:15:28,488
but then there's this extra
secret time at the beginning

246
00:15:28,489 --> 00:15:30,208
where they did communicate,

247
00:15:30,209 --> 00:15:32,848
and then they just were, sort of,
pulled apart so quickly

248
00:15:32,849 --> 00:15:36,248
that, you know,
we can only infer that that happened

249
00:15:36,249 --> 00:15:40,089
by the fact that they must have been
in contact at some point.

250
00:15:41,569 --> 00:15:44,968
So inflation leads
to a massive universe.

251
00:15:44,969 --> 00:15:50,088
Galaxies way beyond the horizon,
way beyond the part that we can see,

252
00:15:50,089 --> 00:15:52,448
possibly infinite in extent.

253
00:15:52,449 --> 00:15:54,448
And that's one of the things
inflation does.

254
00:15:54,449 --> 00:15:58,248
So, it tell us that the universe
should be significantly bigger

255
00:15:58,249 --> 00:15:59,969
than the patch we can see.

256
00:16:06,129 --> 00:16:08,408
Uh, look, I'll probably just stop

257
00:16:08,409 --> 00:16:09,888
and have a look at the stars
on the way home.

258
00:16:09,889 --> 00:16:11,888
It was... yeah, it was really
mind-expanding stuff.

259
00:16:11,889 --> 00:16:14,808
Did you understand it all?
I wouldn't say I understood it ALL.

260
00:16:14,809 --> 00:16:16,288
Excellent. Very good show. Yes.

261
00:16:16,289 --> 00:16:18,168
Did you understand it all?
No.

262
00:16:18,169 --> 00:16:19,929
I'm so confused!

263
00:16:21,809 --> 00:16:24,208
After entertaining
the people of Canberra,

264
00:16:24,209 --> 00:16:28,208
I've made my way to Tidbinbilla,
just outside the capital.

265
00:16:28,209 --> 00:16:30,568
It's home to
one of the most important

266
00:16:30,569 --> 00:16:32,888
deep-space tracking stations
on earth,

267
00:16:32,889 --> 00:16:36,728
and it's a must-see
for an astronomy geek like me.

268
00:16:36,729 --> 00:16:39,368
I always find these places exciting.

269
00:16:39,369 --> 00:16:42,528
If you're a space geek...
..and you look out here,

270
00:16:42,529 --> 00:16:44,288
that big dish you can see

271
00:16:44,289 --> 00:16:48,568
is the only dish in the world
that can talk to Voyager 2.

272
00:16:48,569 --> 00:16:52,328
So, that iconic spacecraft,
I've followed that since 1977,

273
00:16:52,329 --> 00:16:53,888
since I was nine years old.

274
00:16:53,889 --> 00:16:58,048
We're still in contact with it now,
beyond the edge of the solar system,

275
00:16:58,049 --> 00:17:02,008
with its tiny transmitter -
about 16 watts of power,

276
00:17:02,009 --> 00:17:05,288
and THAT dish is the way
that we talk to Voyager.

277
00:17:05,289 --> 00:17:09,568
AND - in the background
is a famous dish.

278
00:17:09,569 --> 00:17:13,328
It's called Honeysuckle,
and that dish is the Apollo dish.

279
00:17:13,329 --> 00:17:15,928
So, when you hear Apollo 11
on the moon

280
00:17:15,929 --> 00:17:18,488
and you hear the last words of NASA

281
00:17:18,489 --> 00:17:20,888
as Apollo 13 came back
into the atmosphere,

282
00:17:20,889 --> 00:17:23,808
the last contact as it re-entered
and the last words you hear

283
00:17:23,809 --> 00:17:25,888
is, "Lost contact at Honeysuckle" -

284
00:17:25,889 --> 00:17:28,368
and that dish through the trees
is that dish.

285
00:17:28,369 --> 00:17:30,569
Farewell, Aquarius,
and we thank you.

286
00:17:32,649 --> 00:17:36,409
OK, IOS in a minute
or a minute and a half.

287
00:17:37,569 --> 00:17:39,089
It's exciting.

288
00:17:40,929 --> 00:17:43,409
- And welcome home.
- Thank you.

289
00:17:52,409 --> 00:17:54,568
Well, it's all very well saying
that the universe underwent

290
00:17:54,569 --> 00:17:58,048
a period of rapid expansion
sometime before the big bang,

291
00:17:58,049 --> 00:18:03,968
but we need some kind of mechanism
that might cause that to happen.

292
00:18:03,969 --> 00:18:06,928
And we have one -
off the shelf, if you like -

293
00:18:06,929 --> 00:18:08,528
from particle physics.

294
00:18:08,529 --> 00:18:10,689
It's a thing called a scalar field.

295
00:18:11,929 --> 00:18:17,488
You could picture it as a sort of
still ocean filling space,

296
00:18:17,489 --> 00:18:19,529
and we call it the inflaton field.

297
00:18:22,369 --> 00:18:24,328
The thing
about that type of field

298
00:18:24,329 --> 00:18:26,968
is we know it had to go away
at some point,

299
00:18:26,969 --> 00:18:29,368
or else the universe would still be
exponentially expanding.

300
00:18:29,369 --> 00:18:31,448
If you have an energy

301
00:18:31,449 --> 00:18:34,728
that is uniformly spread out
through a region of space,

302
00:18:34,729 --> 00:18:38,488
it can yield a new kind of gravity -
repulsive gravity.

303
00:18:38,489 --> 00:18:41,968
Gravity that doesn't pull things
together but pushes things apart.

304
00:18:41,969 --> 00:18:46,648
So, they presuppose that
this kind of... fuel, if you would,

305
00:18:46,649 --> 00:18:48,168
called the inflaton field,

306
00:18:48,169 --> 00:18:51,328
but it's like a fuel that generates
this repulsive gravity,

307
00:18:51,329 --> 00:18:54,769
is what drove the universe to start
expanding in the first place.

308
00:18:57,849 --> 00:19:01,608
The idea that inflation is driven
by the inflaton field

309
00:19:01,609 --> 00:19:04,488
leads to one of
the most remarkable predictions

310
00:19:04,489 --> 00:19:06,328
in the history of cosmology -

311
00:19:06,329 --> 00:19:09,848
which is supported by observation.

312
00:19:09,849 --> 00:19:12,128
Now, you can think of
the inflaton field

313
00:19:12,129 --> 00:19:16,288
as a sort of a still ocean
filling space,

314
00:19:16,289 --> 00:19:21,368
but quantum theory tells us there's
no such thing as a still ocean -

315
00:19:21,369 --> 00:19:24,169
every ocean has ripples in it.

316
00:19:26,049 --> 00:19:28,808
Now, what do those ripples
correspond to?

317
00:19:28,809 --> 00:19:31,088
They mean that the inflaton field

318
00:19:31,089 --> 00:19:35,088
is a little bit bigger
in some regions than others.

319
00:19:35,089 --> 00:19:37,848
So that means
that at the end of inflation

320
00:19:37,849 --> 00:19:39,608
and at the start of the big bang,

321
00:19:39,609 --> 00:19:42,208
some bits of the universe
will have expanded

322
00:19:42,209 --> 00:19:43,968
a little bit more than others

323
00:19:43,969 --> 00:19:47,928
and they will be a little less dense
than the others.

324
00:19:47,929 --> 00:19:52,048
So, at the big bang,
you get a very natural prediction

325
00:19:52,049 --> 00:19:56,448
that some regions of the universe
are slightly denser

326
00:19:56,449 --> 00:19:58,409
than other regions of the universe.

327
00:20:01,729 --> 00:20:04,848
Now, imagine what happens
as this universe expands and cools.

328
00:20:04,849 --> 00:20:07,888
Those denser regions get denser,

329
00:20:07,889 --> 00:20:13,008
and eventually, they collapse
to form the galaxies, the stars.

330
00:20:13,009 --> 00:20:15,088
The fluctuations
in the early universe

331
00:20:15,089 --> 00:20:17,488
led to the structures
that we see today -

332
00:20:17,489 --> 00:20:19,208
including, of course, us.

333
00:20:19,209 --> 00:20:23,449
Without those seeds, without
that structure, we wouldn't exist.

334
00:20:32,729 --> 00:20:36,168
Although inflationary cosmology
does have its critics,

335
00:20:36,169 --> 00:20:40,448
this idea that the universe
underwent a violent expansion

336
00:20:40,449 --> 00:20:43,088
before the hot big bang

337
00:20:43,089 --> 00:20:45,369
is now accepted by many cosmologists.

338
00:20:46,409 --> 00:20:49,888
But a more speculative addition
to the theory exists,

339
00:20:49,889 --> 00:20:54,368
and it opens the doors
to an intriguing possibility -

340
00:20:54,369 --> 00:20:58,368
ours may not be the only universe.

341
00:20:58,369 --> 00:21:01,528
If the theory of inflation
is correct,

342
00:21:01,529 --> 00:21:03,448
then you could ask the question,

343
00:21:03,449 --> 00:21:07,528
how long was inflation going on for
before the big bang?

344
00:21:07,529 --> 00:21:09,448
And the answer is we don't know.

345
00:21:09,449 --> 00:21:12,888
We have a minimum time,
which is quite short, actually -

346
00:21:12,889 --> 00:21:16,448
about 10 to the -35 seconds or so -

347
00:21:16,449 --> 00:21:18,888
but it could have been
much longer than that.

348
00:21:18,889 --> 00:21:20,808
And so you ask the question,

349
00:21:20,809 --> 00:21:23,888
could it have been going on
for an indefinite period of time?

350
00:21:23,889 --> 00:21:26,648
Could you push
the origin of the universe

351
00:21:26,649 --> 00:21:30,168
back and back and back
into the infinite past,

352
00:21:30,169 --> 00:21:32,168
so we have an eternal universe?

353
00:21:32,169 --> 00:21:36,848
The answer is we don't know. There's
theoretical speculation either way.

354
00:21:36,849 --> 00:21:41,528
But imagine if the universe
IS in fact eternal.

355
00:21:41,529 --> 00:21:43,289
There may not have BEEN a beginning.

356
00:21:50,409 --> 00:21:52,608
So, this picture of inflation,

357
00:21:52,609 --> 00:21:54,928
I suppose there are two ways
of looking at it.

358
00:21:54,929 --> 00:21:57,888
There's one that
this universe is all there is

359
00:21:57,889 --> 00:22:00,848
and it inflates and then slows down
and... there we are,

360
00:22:00,849 --> 00:22:04,288
but there are other possibilities,
aren't there?

361
00:22:04,289 --> 00:22:05,888
Yeah, for sure.

362
00:22:05,889 --> 00:22:07,488
And the other possibilities suggest

363
00:22:07,489 --> 00:22:10,968
that we're one of a grand collection
of universes -

364
00:22:10,969 --> 00:22:12,368
we're part of a multiverse.

365
00:22:12,369 --> 00:22:15,928
And again, it's not an idea
that comes out of wild theorising,

366
00:22:15,929 --> 00:22:17,568
it comes right from the math.

367
00:22:17,569 --> 00:22:20,288
You see, when you try to explain

368
00:22:20,289 --> 00:22:22,968
how the universe -
say, our universe - got started,

369
00:22:22,969 --> 00:22:27,288
and you have this repulsive gravity
coming from the inflaton field,

370
00:22:27,289 --> 00:22:29,448
it causes space to expand,

371
00:22:29,449 --> 00:22:32,608
but the math shows that
it's such an efficient process

372
00:22:32,609 --> 00:22:36,448
that you can virtually never
fully use up the fuel

373
00:22:36,449 --> 00:22:38,688
that generated our expansion,

374
00:22:38,689 --> 00:22:41,768
so our big bang happens, but there's
still some fuel left over.

375
00:22:41,769 --> 00:22:44,608
What does it do?
It can generate ANOTHER big bang.

376
00:22:44,609 --> 00:22:46,288
So you get this wonderful process

377
00:22:46,289 --> 00:22:49,488
of big bang after big bang
after big bang,

378
00:22:49,489 --> 00:22:52,888
yielding universe after universe
after universe.

379
00:22:52,889 --> 00:22:55,248
And that's just this natural outcome

380
00:22:55,249 --> 00:22:58,168
of trying to explain the big bang
in OUR universe.

381
00:22:58,169 --> 00:23:00,048
You're naturally led
to the possibility

382
00:23:00,049 --> 00:23:02,289
that it simply is not
a one-time event.

383
00:23:06,649 --> 00:23:08,208
Well, here is Earth,

384
00:23:08,209 --> 00:23:09,888
and we would think it's special,

385
00:23:09,889 --> 00:23:12,008
because we happen to be
pretty close to it,

386
00:23:12,009 --> 00:23:14,968
then you realise,
"Oh, it's one of eight planets."

387
00:23:14,969 --> 00:23:16,808
"But our sun..."

388
00:23:16,809 --> 00:23:20,128
"No, no, it's one of
100 billion other suns."

389
00:23:20,129 --> 00:23:21,528
"The galaxy...!"

390
00:23:21,529 --> 00:23:24,688
"No, it's one of
100 billion galaxies."

391
00:23:24,689 --> 00:23:26,288
"The universe!"

392
00:23:26,289 --> 00:23:29,648
Well, is it just gonna stop there
and we have only one universe?

393
00:23:29,649 --> 00:23:31,888
The trend line tells us,

394
00:23:31,889 --> 00:23:34,649
why shouldn't there be
multiple universes?

395
00:23:41,329 --> 00:23:45,448
If you look out onto this universe,
the one in which we live,

396
00:23:45,449 --> 00:23:49,728
and you ask the question,
could it have been any different?

397
00:23:49,729 --> 00:23:52,488
What would it have looked like
if gravity was a bit stronger?

398
00:23:52,489 --> 00:23:54,688
Or there was a little more
dark energy?

399
00:23:54,689 --> 00:23:58,888
Or the force of electromagnetism
was a little bit weaker?

400
00:23:58,889 --> 00:24:03,489
Very quickly, you get to a universe
which would not permit life to exist.

401
00:24:04,849 --> 00:24:08,088
So it's a legitimate question
to ask - are we lucky?

402
00:24:08,089 --> 00:24:12,808
But in theories that allow you
to have multiple universes,

403
00:24:12,809 --> 00:24:15,448
such as the inflationary multiverse,

404
00:24:15,449 --> 00:24:17,848
then it CAN be the case

405
00:24:17,849 --> 00:24:21,528
that the different bubble-universes
have different laws of physics

406
00:24:21,529 --> 00:24:23,288
and it CAN be the case

407
00:24:23,289 --> 00:24:26,928
that the mechanism
that produces those universes

408
00:24:26,929 --> 00:24:28,928
provides a very natural way

409
00:24:28,929 --> 00:24:32,328
of exploring the landscape
of the laws of physics.

410
00:24:32,329 --> 00:24:34,928
So that then means
that we're not lucky at all,

411
00:24:34,929 --> 00:24:36,888
our existence is inevitable,

412
00:24:36,889 --> 00:24:40,808
because every possible universe
with every possible combination

413
00:24:40,809 --> 00:24:43,888
of physical constants and dark energy
and masses of the particles -

414
00:24:43,889 --> 00:24:46,368
every one exists.

415
00:24:46,369 --> 00:24:50,808
And not only that, but every one
of those is being created

416
00:24:50,809 --> 00:24:53,208
essentially an infinite
number of times

417
00:24:53,209 --> 00:24:56,608
and will go on being created
into the indefinite future.

418
00:24:56,609 --> 00:24:59,768
And THAT is
the inflationary multiverse.

419
00:24:59,769 --> 00:25:02,849
So it says our existence
is inevitable.

420
00:25:04,529 --> 00:25:06,569
"How does that
make you feel?"

421
00:25:12,649 --> 00:25:16,208
We may never know
if our existence is inevitable.

422
00:25:16,209 --> 00:25:20,968
We may never have a complete theory
of the origin of the universe.

423
00:25:20,969 --> 00:25:24,969
But it is remarkable
that we've made so much progress.

424
00:25:28,529 --> 00:25:30,448
The big bang as we see it

425
00:25:30,449 --> 00:25:32,888
was created in a very special way.

426
00:25:32,889 --> 00:25:36,648
The present understanding is
that inflation can do that.

427
00:25:36,649 --> 00:25:40,288
So... that's what I would hang
my hat on right now.

428
00:25:40,289 --> 00:25:42,248
But I wouldn't be surprised

429
00:25:42,249 --> 00:25:46,208
if there are changes in the future
in our understanding.

430
00:25:46,209 --> 00:25:49,768
One day, some smart person will
come along and solve it for you.

431
00:25:49,769 --> 00:25:53,128
That's the beautiful thing
of how science works.

432
00:25:53,129 --> 00:25:55,048
The set of questions
we're asking now

433
00:25:55,049 --> 00:25:58,448
get us to a new vista,
a new place to stand,

434
00:25:58,449 --> 00:26:00,008
and on a new place to stand,

435
00:26:00,009 --> 00:26:02,168
there are other questions
we haven't even dreamt of yet

436
00:26:02,169 --> 00:26:03,888
that I'm sure will be more important

437
00:26:03,889 --> 00:26:05,809
than whatever we think
we're answering today.

438
00:26:08,129 --> 00:26:11,888
I think cosmology is the most
remarkable of the sciences.

439
00:26:11,889 --> 00:26:15,088
I mean, not only are we able
to look up into the sky

440
00:26:15,089 --> 00:26:19,328
and collect the light
from the most distant galaxies,

441
00:26:19,329 --> 00:26:22,608
and even - in the form of
the cosmic microwave background -

442
00:26:22,609 --> 00:26:25,808
from close to the origin
of the universe itself,

443
00:26:25,809 --> 00:26:29,648
but we're able to decode
the messages that it contains

444
00:26:29,649 --> 00:26:34,888
and build plausible theories
of the origin of the universe.

445
00:26:34,889 --> 00:26:38,288
You know, I think our situation
was beautifully summed up

446
00:26:38,289 --> 00:26:41,408
by the Belgian priest
and mathematician Georges Lemaitre,

447
00:26:41,409 --> 00:26:44,248
one of the fathers
of the big bang theory.

448
00:26:44,249 --> 00:26:47,768
He said,
"Standing on a well-cooled cinder,"

449
00:26:47,769 --> 00:26:50,368
"we see the slow fading of the suns"

450
00:26:50,369 --> 00:26:53,808
"and try to recall
the vanished brilliance"

451
00:26:53,809 --> 00:26:56,169
"of the origin of the worlds."

452
00:27:11,689 --> 00:27:14,689
Is there an end of the universe?
Is our universe eternal?

453
00:27:16,409 --> 00:27:18,809
The universe literally
tears itself apart.

454
00:27:19,889 --> 00:27:22,809
Will there be stars and galaxies?

455
00:27:24,009 --> 00:27:27,889
What is the fate of the universe?
How will it all end?

456
00:27:36,769 --> 00:27:38,728
Captions by Ericsson Access Services

457
00:27:38,729 --> 00:27:41,288
Copyright Australian
Broadcasting Corporation