All language subtitles for Brian Cox Life of a Universe 2of2 End Of Days 720p

I'm on tour in Australia...

Some of them might recollapse
in a fraction of a second.

Others might be blown apart
by loads of dark energy.

...talking about
the life of our universe

to scientists
and to space-loving audiences.

I just like having
my brain stretched.

I'll probably just stop and have
a look at the stars on the way home.

On our journey so far, we've explored
how our universe began.

So, this is the oldest light
in the universe.

But what about our future?

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

The universe literally
tears itself apart.

There is some true vacuum somewhere.

We could tunnel into it
at any moment.

Does it make any sense
to talk about this universe

in 100 billion, 200 billion,
a trillion years' time?

Will there be stars and galaxies?

And people, and questions,

and astronomers, and televisions?

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

I suppose we all get used to the idea
that we live finite lives,

and perhaps that's 'cause we imagine
we can leave a legacy -

our children and grandchildren,
great works.

But will that legacy be eternal?

Can we imagine taking the great
achievements of our civilisation

and chiselling them into granite
and leaving them

as a record into the far future?

Or do the laws of nature conspire
to make that impossible?

Will all trace of our civilisation
one day vanish?

What will be our fate?

And what is the ultimate fate
of the universe?

I'm going to investigate the theories
that cosmologists have put forward

for the end of days.

There is a law of physics

called the second law
of thermodynamics,

and to paraphrase it,
it means that on a global scale -

so, across the universe -

things can only get worse.

So, things tend to get
more disordered,

things tend to decay away.

I was once involved in putting
forward the opposite proposition -

things can only get better -

but that is a gross violation
of the second law of thermodynamics.

It really shouldn't have been allowed
even in a song lyric.

♪ Things

♪ Can only get better... ♪

I think, actually,

songwriters should pay more attention
to fundamental physics.

The first stars in our universe
began to shine

around 100 million years
after the big bang.

But it was another 9 billion years
before our star, the sun, formed.

But our sun won't live forever,

which will obviously have a direct
impact on all life on Earth.

The sun is about halfway through the
phase where it's burning hydrogen.

It's making helium.

It's got what we call
the 'solar luminosity' -

it's putting out
that much heat and light.

But that is going to be
slowly increasing.

Presumably at some point we would
find it extremely uncomfortable here.

Yeah.

In about 1.1 billion years,

it will have got to 10% brighter
than it is now.

That is enough to create
what's called a moist greenhouse.

So life on Earth will become
very problematic at that stage.

3.5 billion years from now,

it'll be 1.4 times
its current luminosity,

and that's enough
to evaporate the oceans.

Right.

So that's getting fairly severe
at that stage.

It's really got
another 5 billion years to go

that it can keep on
burning hydrogen,

but it will become uncomfortable
for us well before that.

The destiny of stars like our sun
is to run out of fuel and collapse.

The core compresses, but the rest
of the star expands enormously

and we have a red giant.

So we enter this red giant phase.

When our sun becomes a red giant

and it begins to swell and engulf
the orbit of Mercury,

it's gonna start getting
very hot on Earth.

We're gonna need ways
to terraform Mars

and then ship billions of people
to Mars,

because Mars will be cooler
than Earth,

it being one and a half times
farther away.

The Earth will basically get fried
at that point.

We won't be able to exist.

Hopefully, if humans are still
around in some form or another,

we've moved off to better locales.

So, the ultimate fate of our star,
the sun, is to be this cooling ember?

That's the ultimate fate of the sun.

So, in just over a billion years,
this place will become uninhabitable.

In 6 to 7 billion years,
the sun will be gone.

But that, of course,
isn't the end for the universe,

and matter that floats out
from our dying sun

will recollapse to other stars,
other planets

and perhaps other living things.

But that process can't go on forever.

There comes a point
in the life of the universe

when the constant recycling,
the births of new stars, has to stop.

So, what IS the fate of the universe?

How will it all end?

Cosmologists have thought about this
for a long time,

and many have come to the conclusion
that the end will come

in more of a whimper than a bang.

It's known as the heat death,

and it begins with a decrease
in the rate of star formation.

Looking up into the southern sky

allows us to see a hint
of this process.

As soon as you look
through a telescope,

you do get a sense of the amount of
gas and stuff out there, don't you?

You always hear this wonderful phrase
'stellar nurseries'.

So, is that really accurate,

that you really do have these places
where all the action is concentrated?

Absolutely.

In order to form stars, you have
to put together a lot of material,

and so you naturally pop off a lot
of stars in that particular area.

I can't...
I can't stop looking, actually.

Fortunately, we have
very powerful telescopes

to see all the way across the galaxy

so that we can pick out stars

in all kinds of stages
of their formation process,

from when they just start collapsing

to when they really kick on
and turn into full-blown stars.

Stars form from collapsing clouds
of gas and dust.

And the leftover material
forms into planets and moons

and asteroids and comets.

But in our part of the Milky Way,

this construction process
is slowing down.

Is this a glimpse
of the beginning of the end?

We see that around
the, sort of, solar neighbourhood,

around where the sun lives,

that there's about half as much
star formation

as there was 10 billion years ago.

Why is that?

Once you form a star, it dies

and it holds
some of its matter together

in a black hole or a white dwarf
or a neutron star,

and you've locked that gas up
forever

and it never goes back
to being a star again.

So in order to keep forming stars,

you've got to keep bringing gas in
from somewhere else.

So the fact that
the rate is dropping...

...you said a factor of two from,
what, 10 billion years ago to now,

implies, of course, that some time
in the future, that's gonna stop.

So, when is that?

It's a long time.
Not in our lifetimes.

I think if you do the extrapolation,

you go out 100 billion years
or something, more than that.

It's a long time away.

Eventually, we will run out of gas
to form new stars

in every single galaxy,

and gradually, gradually, gradually,
the universe will... die away.

So, what will our descendants
actually see

when they look up into the night sky
in a few billion years' time?

Well, the centre of the galaxy
is here, isn't it?

Yeah. It's kind of the empty bit
of sky up here - Sagittarius.

Peer into the centre of the Milky Way

and, like virtually
all other galaxies,

you'll find
a supermassive black hole.

Ours is around 4 million times
the mass of the sun.

We don't know how these
supermassive black holes form,

but we do know about smaller,
stellar-mass black holes.

And when the centre of those stars
are more massive

than about two or three times
the mass of our sun,

they actually collapse
into a singularity,

is the theory,

and the space-time around them
bends completely on itself,

so nothing...

The gravitational pull is so strong,
nothing, even light, can't escape.

So, then we're left, I suppose,
with a dark sky,

but a sky full of black holes...

Yeah.
..and, what, fading stellar remnants?

Yeah, fading stellar remnants.

Things like faintly glowing cores
of long dead stars,

billions or even trillions of years
in the future,

and these are glowing so faintly,
you can't even see them.

Now, black holes do radiate
very, very faintly,

but we won't actually be able
to see that,

because they'll all be
too far apart.

You get the sense, I suppose,
when you talk about that,

this starry sky, we take for granted.

Although, perhaps we don't.

You know, perhaps
it's the most beautiful thing

but it's a temporary phenomenon.

It's actually a very short-term
phenomenon, isn't it?

We're only nearly 14 billion years
into the universe's history.

So in the far, far future,
hundreds of billions of years' time,

if we could still stand somewhere
and look out into the night sky,

we would see just blackness,

and there would be no hints at all
to tell us

about the past glorious history
of our universe.

But is this the whole picture?

Science has a habit of
opening up new possibilities -

often when you least expect them.

We've known our universe is expanding
since the 1920s,

and we thought the expansion rate
was slowing down.

Then, in the late 1990s,
it was discovered

that the expansion rate of our
universe is actually speeding up.

Nobel Prize winner Brian Schmidt

was as surprised as anyone
by his discovery.

1998,
we went through and we measured

that the universe wasn't slowing
down at all - it was speeding up.

And that was... well,
it looked to me like a big mistake

and that I had somehow wasted
three and a half years of my life

getting some nonsensical answer.

We knew that Einstein
had invented something -

called 'dark energy'
or the 'cosmological constant',

which makes gravity push
rather than pull,

but that seemed pretty crazy -

that was, sort of,
Einstein's 'bad idea'.

If the universe continues
to expand forever

and indeed continues to accelerate
in its expansion,

then in the far future,

you end up with a universe
that's just a sea of photons

being stretched
by the expansion of space

and cooling down
to the same temperature,

so you end up with a universe
where there is no structure.

There's no possibility
of storing any information

or processing any information,

no possibility of consciousness
or life,

no structures at all,

and that sea of cooling photons
will last forever.

The idea that there is a mysterious
thing called 'dark energy'

which drives the accelerating
expansion of our universe forever

is the standard model of cosmology.

But it's not the only theory
about how our universe could end.

The 'heat death' -

this idea the universe
just gradually grinds to a halt

and carries on expanding forever -

is a bit miserable,

but the physics of the far future
is not very well understood.

So there are, in fact, other, and I
think more exciting, possibilities.

So, like the Robert Frost poem,

it seems like things will end
in ice, not in fire.

But there's a big caution here,

which is we don't really understand
dark energy very well,

and so this is really only one
of a couple of possibilities.

Cosmologists have come up with
an even more devastating idea

called 'phantom dark energy',

which eventually leads to
the universe ripping itself apart.

If the universe has
this dark energy,

this stuff causes gravity
to push from itself.

This is another really great way
to destroy the universe.

So as the universe gets bigger,

this stuff dominates the universe
more and more,

because it's part of space itself.

You make more space,
you have more dark energy,

which makes dark energy stronger
over the other forms of gravity.

Over time, this phantom dark energy

would start to pull apart
bound orbits.

So, first, it would pull apart
the galaxy.

Stars would start to wander off,
'cause it's still increasing.

It'll start to break up
all structure, all matter.

And then at some point,

the entire universe will be...
torn asunder, in some sense.

It's called the 'big rip'.

You reach the...
the breaking point, literally,

and the fabric of the universe
starts to tear a hole,

the laws of the universe
and the boundaries of the universe

just start going haywire.

So that's the big rip?
So that's the big rip.

I mean, that's one of
the theories, right?

There's the big rip
and the big freeze.

I love the big rip, 'cause...

...who doesn't like
a universe ripping, right?

The 'big rip' idea can be combined
with a theory we have

describing the beginning of
our universe, known as inflation,

which describes a time
before the hot big bang,

when our universe was expanding
extremely rapidly.

So, inflation...
That's right.

...that rapid expansion
before the big bang,

could be envisaged as being the end
of a previous universe

that's undergoing a big rip?

Exactly. It's... you know,
you have these big questions,

but when you look at it
fundamentally,

if you have a universe that grows
quickly through dark energy,

which rips,

that would mimic pretty similar to
what we think happened in inflation.

We are pretty confident we know
inflation had to happen in some form

to get the universe
that we see today,

so it's not crazy to think
that these two things are related.

We don't have
the evidence for it yet,

but it's not the worst idea
we've had.

We said that inflation stops
and the big bang happens.

But what if inflation
doesn't stop all at once -

it just stops in patches?

So then our big bang
would just be a little event

in an ever inflating space.

And there'll be other patches
that stop and you get a universe,

other patches that stop
and you get a universe.

And that process could go on forever.

So, although our universe dies,

other universes
are constantly being created.

This is called
the inflationary multiverse.

So you get
this wonderful process

of big bang after big bang
after big bang,

yielding universe
after universe after universe.

How are we to picture that?

Are we to picture our universe
riding on the back

of some kind of... potentiality
of expanding space-time?

You can.

I've got a more down-to-earth way,
which is,

think of a big piece
of Swiss cheese,

big block of Swiss cheese, right?

Each of the openings
is like a universe,

and the cheese itself
is the inflaton field

driving the ever accelerated
expansion of the universe.

And as this cheese expands,

more and more pockets
open up inside -

more and more universes are created.

And our universe
is simply one opening

in the block of Swiss cheese -

that's all that we are.

The idea of a multiverse is tricky
to get your head around.

This is where we keep...
the cream of the crop.

But I'm hoping
a glass of Aussie shiraz

will enhance my powers of analogy.

Cheers. Thank you.

I'm tempted to draw the analogy
with inflationary cosmology...

Well, of course.

...and say that each one of these
is like a different universe

with different physical laws.

Each barrel in this warehouse

is taken from a different part
of the vineyard,

so each barrel is a different
expression through the grapes

of the landscape.

So, in that analogy,

our universe would be
just one barrel -

of shiraz viognier, in this case -

amongst a whole possible warehouse
of barrels,

different expressions
of possibilities.

It's a good analogy.
It's not too forced.

Physicists refer to each different
possibility as a different vacuum,

and this opens up the chance that
we could be instantly annihilated.

My favourite way to destroy
the universe is vacuum decay,

which is a really fun idea

and... and one that's gotten
really popular lately

because of things that we're seeing
at the Large Hadron Collider.

The Large Hadron Collider at CERN,
on the French-Swiss border,

is the largest scientific machine
in the world.

In 2012, the Higgs boson
was discovered here.

But its properties suggest

that our universe could be in
an unstable 'false vacuum' state.

There is some true vacuum somewhere,

and we could... maybe tunnel into it
at any moment...

...you know,
and just destroy the universe.

By any moment, you probably...
I mean, it's unlikely.

You're a cosmologist.

If you're still watching this,
it hasn't happened yet.

The timescale for vacuum decay is
many times the age of our universe,

so it's not gonna happen tomorrow.

But it's still disconcerting
to think that our universe

ISN'T the stable, eternal home
we once believed it to be.

But you might think, "Well,
quantum mechanics, could it save us?"

"Could there be a little fluctuation
that allows something to happen"

"and reboot
part or all of the universe?"

You know, you never know.

But probably not.

Whether it's vacuum decay, a big rip

or a sad, slow heat death over
the next 10 to the 1,000 years,

now is the time
to explore our universe,

while it's still visible to us.

We live in a special time
in the universe's history -

the time when the universe
is young enough

that we can look out into the night
sky and see billions of galaxies.

The galaxies are not receding
away from us fast enough

that they outrun the light.

So, our descendants,
when they look out into deep space,

will see black, inky,
dark stillness.

And they'll think that this little
collection of galaxies

that are all bound together
gravitationally nearby,

they'll think that's it.

And that's a wrong picture
of the universe,

but nevertheless, that's the picture
which our descendants

are gonna naturally be led to
through their own observations.

The future astronomers
in 2 and 4 and 6 billion years

will think we're crazy, 'cause they
can't see the evidence that we have.

I think, actually, it was
Brian Greene who said to us

that cosmology essentially
becomes a religion.

That's right, yeah.

'Cause all you've got is
history books telling you...

Exactly.

...about the oldest light
in the universe.

That's right. You can't go
and reproduce the experiment.

We would just have to believe
someone else's word.

And then... what are we doing?

Who are we to think,
who are we to say

that WE have a complete record
of the universe to draw from?

What chapters of
our book of the universe

had been removed before
we even acquired the book?

The fascinating thing
about the far future

in an accelerating
and expanding universe

is that you get to a point where
you can't do cosmology anymore -

there's no such science as cosmology.

You couldn't deduce from what you see

that you live in
an expanding universe

that had an origin
at some point in the past.

So cosmology becomes a subject

that is only accessible
through ancient books

and not accessible through
the things you can see.

So, in that sense, I think that
the future of the universe is sad,

because your ability
to gather knowledge

about the universe
as it was in its past

disappears.

How will the universe end?

I have no idea.

I don't know.

I don't know.

You know, it's very difficult
to make predictions

about the fate of the universe

when there's 95%
we don't understand.

OK.

We should just make a documentary
called I Don't Know.

Galaxies are forming
and stars are exploding

and, you know, we're seeing evidence
of things happening in the big bang

and the universe is expanding
ever faster,

and we're just sitting here
drinking our tea.

Yeah.
You know?

I've had the good fortune

to share my enthusiasm
for physics and the cosmos

with Australian audiences
curious to contemplate

the nature of our universe.

Amazing.
Absolutely tremendous. Yeah.

Oh, he takes us on
a great journey, I think.

Did you understand it all?

Uh... not all of it, but, yeah,
bits and pieces of it, yes.

I love the fact that when I finish
work after a really hard day,

I can come to something like this

and he can make me feel
really insignificant

compared to the rest
of the universe.

And I've met scientists under
a truly inspiring southern night sky

who share that curiosity
and desire to know more.

We've got work to do!

I suppose there are two ways

of looking at the future
of the universe.

You might feel depressed

that although the universe will
almost certainly exist forever,

we certainly won't.

There will come a time in the future

when it's not possible
for ANY life to exist.

Or you might feel fortunate.

You might feel fortunate
that we live in a time

when we can look out
into the night sky

and see the light from
distant stars and galaxies

and from the very origin
of time itself

and understand how our universe began

and make predictions
about how it might end.

Captions by Ericsson Access Services

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Broadcasting Corporation