All language subtitles for Brian Cox Life of a Universe 1of2 Creation 720p

Did our universe have a beginning?

Why is there a universe
like this one?

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

Why are there rivers and flows
and filaments of galaxies?

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

I'm on tour in Australia,

talking to audiences and scientists
about two fundamental questions -

how did the universe begin...

Like in the big bang,
it feels audacious.

...and how will it end?

Life on earth will become
very problematic.

In the last decade,

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

So, this IS the oldest light
in the universe.

This is the story
of our scientific quest

to understand
the origin of the universe.

Of all the questions in science,

the question of the origin
of the universe

is one that I think needs
no motivation.

Every human culture
has its own creation story,

and science is no different.

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

that the universe began
in the big bang.

But in the last decade or so,

new precision measurements
of the cosmos,

coupled with
theoretical developments,

have given us an unprecedented
and detailed picture

of the origin of the universe.

If this were a lesser program,

we would start it
in a deep voice going,

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

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

"THAT is the time before time"

"and place without space"

"that we call the big bang."

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

I think if you ask the question,

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

I suppose the answer
has to be curiosity.

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

why do we exist?

When I think of a scientist,

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

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

Indigenous Australians
have been observing the stars

for more than 40,000 years,

and, like many ancient cultures,

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

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

The emu sacrificed his wings

and was given an eternal place
in the southern skies.

Forever you will be seen
running across the night sky

and marked as 'dyurra' - the stars.

I've always liked creation stories.

I like reading about them
from across the world.

Why do we do it?

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

Why do we measure the expansion rate
of the universe

and build theories to explain it?

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

And the evidence for that is

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

And the most wonderful thing

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

is that we also have
a creation story.

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

But what is the big bang?

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

With observations
and mathematical theorising,

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

the universe was incredibly dense
and it was incredibly hot.

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

Give me some violations of
the laws of particle physics.

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

So, what's the big bang?

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

I just know what came after
the big bang,

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

it's really hot.

These things, we do know.

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

You can trace everything back
and you get to a point

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

and something happened
that made that expand, right?

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

I'm liking the big bang.

That just feels right.
It feels audacious.

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

The moment when everything
came from nothing.

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

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

was an event
in a pre-existing universe

and not the beginning at all.

But how can we be so confident?

How can we even dare
to speak of things

that happened
almost 14 billion years ago?

In 1927,
the astronomer Edwin Hubble noticed

that the light from distant galaxies
is stretched.

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

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

that means that in the past,

the distances between the galaxies
was smaller,

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

that everything is effectively
on top of each other.

That implies that our universe
had a beginning,

there was a day without a yesterday,

and that is what we call
the big bang.

More than 30 years after
Hubble made his observations,

cosmologists remained divided

about whether the big bang theory
was correct.

More evidence was needed.

And it came in the 1960s,

with the discovery of
a mysterious faint signal.

We call it the cosmic microwave
background radiation.

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

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

So, this is the oldest light
in the universe.

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

and 13.8 billion years
from over there,

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

One of the many remarkable things
about the cosmic microwave background

is the story of its discovery,

because it was found
entirely by accident.

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

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

So, where did the cosmic microwave
background come from?

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

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

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

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

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

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

the universe becomes
almost instantly transparent,

so light can travel
in straight lines,

and it will continue to travel
in straight lines

for the rest of the expansion history
of the universe

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

The cosmic microwave background
is considered such strong evidence

in large part because

the big bang theory predicted
that it should exist.

It was first observed
in the mid-1960s,

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

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

really took hold.

It's an almost overwhelming
piece of evidence,

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

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

We don't see it as a hum.

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

the whole sky
looking out into the universe,

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

This remarkable baby photograph
of the universe

confirmed that
we had the basics right.

But its great detail
presented fresh challenges.

As we often find with science,

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

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

is in some ways unsatisfactory.

It raises a series of
childlike questions.

Like, if the universe
had a beginning,

then what happened
before the beginning?

What caused it?

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

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

Was there a before?

Well, that is
a philosophical question,

unless you can come up with a theory

that predicts something that
you can test against observation.

The clues which point the way
to a theory

of what came before the big bang

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

There are two problems
with the standard big bang model.

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

You can picture the horizon problem
as follows.

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

which is to say
the cosmic microwave background,

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

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

which is the cosmic
microwave background.

But those two points on the sky
are separated today

by 90 billion light-years.

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

and is only 13.8 billion years old,

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

Which means there's no explanation

for how they could be
so precisely the same.

And then there's
the flatness problem.

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

Which seems very strange,

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

or curved like the surface
of a saddle.

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

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

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

it was expanding incredibly fast.

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

every 10 to the -37 seconds.

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

of a second.

Why does that solve
the horizon and flatness problems?

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

way bigger than the piece
we can see today.

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

Think about an analogy with
the surface of the Earth.

This little piece of the Earth here
looks flat,

even though we know
the Earth's curved.

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

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

It also solves our horizon problem,

because it says that
that piece of the sky,

which is so far away from that piece,

were once in contact with each other.

They could jiggle around
and get to the same temperature,

but then they were ripped apart.

It's mind-boggling,

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

then this violent rapid expansion
must have occurred

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

So, what is our current theory?

This theory called inflation

that says there was something
going on before,

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

Yeah, yeah, the hot big bang.

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

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

the universe is in
a fireball kind of state.

Yeah.

Yeah, the reason we know
that something happened before

is we can look at
that primordial fireball state.

Like, we can actually see it.

Because we can see
the cosmic microwave background,

which is the, sort of, afterglow
of that time

when the whole universe
was hot and dense.

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

that things that were connected
to each other before,

close enough together
to communicate,

to come into equilibrium,
to be the same temperature,

rapidly come out of contact.
Yeah.

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

and we see that two different parts
of the universe

that should never have been
in contact with each other

are the same temperature,

it's because you can dial back
the expansion

and find that they were
never in contact,

but then there's this extra
secret time at the beginning

where they did communicate,

and then they just were, sort of,
pulled apart so quickly

that, you know,
we can only infer that that happened

by the fact that they must have been
in contact at some point.

So inflation leads
to a massive universe.

Galaxies way beyond the horizon,
way beyond the part that we can see,

possibly infinite in extent.

And that's one of the things
inflation does.

So, it tell us that the universe
should be significantly bigger

than the patch we can see.

Uh, look, I'll probably just stop

and have a look at the stars
on the way home.

It was... yeah, it was really
mind-expanding stuff.

Did you understand it all?
I wouldn't say I understood it ALL.

Excellent. Very good show. Yes.

Did you understand it all?
No.

I'm so confused!

After entertaining
the people of Canberra,

I've made my way to Tidbinbilla,
just outside the capital.

It's home to
one of the most important

deep-space tracking stations
on earth,

and it's a must-see
for an astronomy geek like me.

I always find these places exciting.

If you're a space geek...
..and you look out here,

that big dish you can see

is the only dish in the world
that can talk to Voyager 2.

So, that iconic spacecraft,
I've followed that since 1977,

since I was nine years old.

We're still in contact with it now,
beyond the edge of the solar system,

with its tiny transmitter -
about 16 watts of power,

and THAT dish is the way
that we talk to Voyager.

AND - in the background
is a famous dish.

It's called Honeysuckle,
and that dish is the Apollo dish.

So, when you hear Apollo 11
on the moon

and you hear the last words of NASA

as Apollo 13 came back
into the atmosphere,

the last contact as it re-entered
and the last words you hear

is, "Lost contact at Honeysuckle" -

and that dish through the trees
is that dish.

Farewell, Aquarius,
and we thank you.

OK, IOS in a minute
or a minute and a half.

It's exciting.

- And welcome home.
- Thank you.

Well, it's all very well saying
that the universe underwent

a period of rapid expansion
sometime before the big bang,

but we need some kind of mechanism
that might cause that to happen.

And we have one -
off the shelf, if you like -

from particle physics.

It's a thing called a scalar field.

You could picture it as a sort of
still ocean filling space,

and we call it the inflaton field.

The thing
about that type of field

is we know it had to go away
at some point,

or else the universe would still be
exponentially expanding.

If you have an energy

that is uniformly spread out
through a region of space,

it can yield a new kind of gravity -
repulsive gravity.

Gravity that doesn't pull things
together but pushes things apart.

So, they presuppose that
this kind of... fuel, if you would,

called the inflaton field,

but it's like a fuel that generates
this repulsive gravity,

is what drove the universe to start
expanding in the first place.

The idea that inflation is driven
by the inflaton field

leads to one of
the most remarkable predictions

in the history of cosmology -

which is supported by observation.

Now, you can think of
the inflaton field

as a sort of a still ocean
filling space,

but quantum theory tells us there's
no such thing as a still ocean -

every ocean has ripples in it.

Now, what do those ripples
correspond to?

They mean that the inflaton field

is a little bit bigger
in some regions than others.

So that means
that at the end of inflation

and at the start of the big bang,

some bits of the universe
will have expanded

a little bit more than others

and they will be a little less dense
than the others.

So, at the big bang,
you get a very natural prediction

that some regions of the universe
are slightly denser

than other regions of the universe.

Now, imagine what happens
as this universe expands and cools.

Those denser regions get denser,

and eventually, they collapse
to form the galaxies, the stars.

The fluctuations
in the early universe

led to the structures
that we see today -

including, of course, us.

Without those seeds, without
that structure, we wouldn't exist.

Although inflationary cosmology
does have its critics,

this idea that the universe
underwent a violent expansion

before the hot big bang

is now accepted by many cosmologists.

But a more speculative addition
to the theory exists,

and it opens the doors
to an intriguing possibility -

ours may not be the only universe.

If the theory of inflation
is correct,

then you could ask the question,

how long was inflation going on for
before the big bang?

And the answer is we don't know.

We have a minimum time,
which is quite short, actually -

about 10 to the -35 seconds or so -

but it could have been
much longer than that.

And so you ask the question,

could it have been going on
for an indefinite period of time?

Could you push
the origin of the universe

back and back and back
into the infinite past,

so we have an eternal universe?

The answer is we don't know. There's
theoretical speculation either way.

But imagine if the universe
IS in fact eternal.

There may not have BEEN a beginning.

So, this picture of inflation,

I suppose there are two ways
of looking at it.

There's one that
this universe is all there is

and it inflates and then slows down
and... there we are,

but there are other possibilities,
aren't there?

Yeah, for sure.

And the other possibilities suggest

that we're one of a grand collection
of universes -

we're part of a multiverse.

And again, it's not an idea
that comes out of wild theorising,

it comes right from the math.

You see, when you try to explain

how the universe -
say, our universe - got started,

and you have this repulsive gravity
coming from the inflaton field,

it causes space to expand,

but the math shows that
it's such an efficient process

that you can virtually never
fully use up the fuel

that generated our expansion,

so our big bang happens, but there's
still some fuel left over.

What does it do?
It can generate ANOTHER big bang.

So you get this wonderful process

of big bang after big bang
after big bang,

yielding universe after universe
after universe.

And that's just this natural outcome

of trying to explain the big bang
in OUR universe.

You're naturally led
to the possibility

that it simply is not
a one-time event.

Well, here is Earth,

and we would think it's special,

because we happen to be
pretty close to it,

then you realise,
"Oh, it's one of eight planets."

"But our sun..."

"No, no, it's one of
100 billion other suns."

"The galaxy...!"

"No, it's one of
100 billion galaxies."

"The universe!"

Well, is it just gonna stop there
and we have only one universe?

The trend line tells us,

why shouldn't there be
multiple universes?

If you look out onto this universe,
the one in which we live,

and you ask the question,
could it have been any different?

What would it have looked like
if gravity was a bit stronger?

Or there was a little more
dark energy?

Or the force of electromagnetism
was a little bit weaker?

Very quickly, you get to a universe
which would not permit life to exist.

So it's a legitimate question
to ask - are we lucky?

But in theories that allow you
to have multiple universes,

such as the inflationary multiverse,

then it CAN be the case

that the different bubble-universes
have different laws of physics

and it CAN be the case

that the mechanism
that produces those universes

provides a very natural way

of exploring the landscape
of the laws of physics.

So that then means
that we're not lucky at all,

our existence is inevitable,

because every possible universe
with every possible combination

of physical constants and dark energy
and masses of the particles -

every one exists.

And not only that, but every one
of those is being created

essentially an infinite
number of times

and will go on being created
into the indefinite future.

And THAT is
the inflationary multiverse.

So it says our existence
is inevitable.

"How does that
make you feel?"

We may never know
if our existence is inevitable.

We may never have a complete theory
of the origin of the universe.

But it is remarkable
that we've made so much progress.

The big bang as we see it

was created in a very special way.

The present understanding is
that inflation can do that.

So... that's what I would hang
my hat on right now.

But I wouldn't be surprised

if there are changes in the future
in our understanding.

One day, some smart person will
come along and solve it for you.

That's the beautiful thing
of how science works.

The set of questions
we're asking now

get us to a new vista,
a new place to stand,

and on a new place to stand,

there are other questions
we haven't even dreamt of yet

that I'm sure will be more important

than whatever we think
we're answering today.

I think cosmology is the most
remarkable of the sciences.

I mean, not only are we able
to look up into the sky

and collect the light
from the most distant galaxies,

and even - in the form of
the cosmic microwave background -

from close to the origin
of the universe itself,

but we're able to decode
the messages that it contains

and build plausible theories
of the origin of the universe.

You know, I think our situation
was beautifully summed up

by the Belgian priest
and mathematician Georges Lemaitre,

one of the fathers
of the big bang theory.

He said,
"Standing on a well-cooled cinder,"

"we see the slow fading of the suns"

"and try to recall
the vanished brilliance"

"of the origin of the worlds."

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

The universe literally
tears itself apart.

Will there be stars and galaxies?

What is the fate of the universe?
How will it all end?

Captions by Ericsson Access Services

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Broadcasting Corporation