All language subtitles for How the Universe Works s03e02 The End of the Universe.eng

The universe was born to die.

But how and when
will it all end?

That's the reason
i became a cosmologist.

I wanted to be the first person
that would know

how the universe would end.

Two cosmic heavyweights
wrestle for control.

The winner seals our fate.

The tug of war is gravity,

which is trying
to shrink it down,

and the expansion of space
and time itself.

Will gravity triumph?

The universe will get smaller
and smaller, hotter and hotter.

Or will expansion
get the upper hand?

Even the electrons around
your atoms will be ripped apart.

The end is coming,

and it could be
sooner than you think.

The universe is everything

all space, all time, all matter.

The earth is a speck
by comparison,

a grain of rock orbiting just
one of the 200 billion stars

in our home galaxy,
the milky way.

In turn, this enormous structure
is just a drop

in an ocean of galaxies
that stretch

for 90 billion light years.

And all of this,

from the biggest galaxy
to the smallest atom,

will one day die.

We don't see evidence
of anything being eternal.

Eternity doesn't exist.

Even space and time
will come to an end.

The universe has been
expanding since its birth,

gradually burning through
the fuel that lights its stars.

But what happens
when the fuel runs out?

Will it all just fade away?

Stars die out,
use up their nuclear fuel.

We have an empty, cold,
desolate universe.

Just dead remnants of stars

black holes, neutron stars.

Eventually, they decay away,

and you're left with a thin haze
of very low energy light.

That's it.

We used to think the universe

would cruise gently
into old age.

But over the past few decades,

astronomers have
revealed a very different

and disturbing picture.

The universe isn't cruising.

It's fighting for its life.

It may seem peaceful here
on earth on a nice, sunny day,

but in fact, above us
and all around us,

throughout the universe,
a battle is raging,

and it has raged
since the beginning of time.

Two deadly forces
grapple for control.

The first, expansion,
pulls galaxies apart,

cooling the universe
and threatening it

with a frozen extinction.

The second, gravity, tries to
crush everything back together,

annihilating the universe
in a dense ball of fire.

Will gravity or expansion win?

Or will it end in a tie?

These two colossal forces
yield three endgames.

One is the big freeze.

Expansion wins, and the universe
just expands forever.

The second is that there is
a delicate balance

between the expansion

and the amount of gravitational
attraction,

and the universe gets
to a particular size,

and it pretty much stays there.

And the third outcome is that

the gravitational
attraction wins,

and the expansion stops,

and the universe
begins to get smaller

until, eventually,
it goes back to a big crunch.

So far,
the universe seems balanced

on a tightrope between
expansion and contraction.

But will it keep its equilibrium
until it runs out of steam,

or will something
tip the balance?

I don't think there's
any bigger question than,

where is the universe going?

To predict the future,
cosmologists have always looked

to the past, back to
the beginning of expansion,

the beginning of gravity,
the beginning of everything.

13.8 billion years ago,
An infinitely dense,

hot speck ignites
and suddenly expands outward

the big bang.

All energy, all space,
and all matter...

...the building blocks of
The universe we see today,

are created and set in motion.

Think of it.

Everything you see around us

concentrated into a primordial
fireball that exploded,

sending all the galaxies
into motion.

That outward blast,
the birth of expansion,

is still going on today.

Without it, we wouldn't have
a universe big enough

for stars
and galaxies to exist in.

Expansion is an astonishing
force of nature.

It works by inflating
the fabric of space-time.

Space between galaxies expands,

and it pushes
the galaxies apart.

Space carries objects with it
like a surfer on a wave.

It's going on
in every part of space.

Even inside your body right now,

there's a pressure
for space to expand.

Expansion generated
the vast, moving stage

on which today's universe
plays out.

But left unchecked,
it could have been a force

for utter annihilation.

If the universe had
been expanding much faster,

it would have emptied out
so fast,

you wouldn't have had time
to make galaxies,

planets, people.

The fact
that we're here

means that something must have
put on the brakes.

It was, of course,
our universal glue -- gravity.

Gravity and matter
go hand in hand.

The more massive the object,

the more pull it exerts
on everything around it.

It draws atom to atom,
particle to particle...

...building stars, nebulas,

Galaxies

the hardware of the universe
we see today.

But gravity
is a double-edged sword.

Too much, and the early universe
would never have gotten

out of the starting blocks.

If it had been
expanding more slowly,

it would have re-collapsed
into another singularity.

And again, you wouldn't have had
the time to make galaxies,

planets, or people.

So we live in the goldilocks
universe.

We live in the universe
that lasts long enough

that we can be here,
but expands gently enough

that we have time to form.

The universe has
lasted for 13.8 billion years,

thanks to the opposing forces
of gravity and expansion.

But just how stable
is this balancing act?

Does our universe have just
the right amount of stuff in it

to keep it from
runaway expansion

or catastrophic collapse?

In the 1920s,
scientists did the math,

and the results were
anything but reassuring.

The more matter you have,
the more gravity you have.

If you have lots of matter
in a very dense universe,

perhaps the universe
begins to re-collapse.

Or, if you have
very little matter,

the universe would
freeze to death.

So what is the critical density,
the border between the two?

It's approximately five hydrogen
atoms per cubic meter.

So think of a cubic yard,
and put just five hydrogen atoms

inside,
and that is the tipping point.

If you put more than five atoms,

then the universe will
begin to collapse.

If you have
less than five atoms,

then the universe
just keeps on going.

If we thought
the universe was balanced

on a tightrope before,
the critical density question

showed us that the rope
was more like a razor blade.

Yet, when astronomers took
additional measurements,

they liked what they saw.

The universe appeared to contain
just the right amount

of matter to stay
at the critical density.

More and more,
the indirect evidence

and the theoretical
arguments suggested

that the universe must be
exactly at the boundary

between a universe
that would collapse

and one that
would expand forever,

that we were teetering
on the hairy edge of expansion.

The universe seemed
so perfectly balanced

that it would head quietly
into old age.

Then, in the 1970s, astronomers
made an observation

that shocked them.

The cosmos was filled
with invisible stuff,

and its gravity could cause
a catastrophic collapse.

The universe
is balanced on a tightrope.

On each side of the drop
lies an early death

a big freeze, fueled by
the runaway stretching of space,

or a big crunch, the result of
gravity overcoming expansion.

40 years ago, scientists
Believed we'd stay balanced

between these fates
for eternity.

Now things have changed
tremendously,

because we've discovered
something we never knew about

40 years ago.

In the 1970s,
astronomers are stunned.

Some unknown form of matter,
invisible to telescopes,

dwarfs what we thought was
out there,

not a fraction more,
but five times more.

We used to think
that gravity came from stars

and objects you can see
end of story.

Now, we realize that that naive
picture is actually wrong.

Astronomers make
the discovery,

studying the clockwork
nature of our universe.

The huge gravity of the sun
holds the earth

and all the other planets
in a delicate circular dance.

The sun's mass controls
the speed of these orbits.

If it were more massive,
the planets would orbit

much more quickly.

And if it were smaller,
it would take much longer

for a planet to complete
an orbit.

Galaxies run
like clockwork, too.

The vast mass at the center
pulls the outer stars

into circular,
planet-like orbits.

Astronomers make
precise measurements

of these galactic
orbits in the 1970s.

The results change everything.

The galaxies
were spinning too fast.

Way too fast.

Even accounting for
the supermassive black holes

at their center, nine-tenths
of their mass was missing.

By rights,
the galaxy should fly apart.

By rights, the earth
should have been flung

into intergalactic space
billions of years ago.

We should have no
milky way galaxy, and yet,

our universe is
full of galaxies.

An immense
additional source of gravity

must be holding galaxies
together.

But no matter where astronomers
point their telescopes,

they see nothing.

Not a glimmer, not a shadow.

Whatever this new stuff is,
it doesn't emit light,

reflect light,
or even block light.

They call it dark matter.

What we've learned is that most
of the matter in the universe

is not ordinary stuff.
it's not atoms.

It's not particles we've yet
detected in any experiment

done here on earth.

It's some new kind of particle
that we call the dark matter.

Dark matter fills the universe,

outstripping normal matter
by 5-to-1.

Vast filaments spread out
throughout the cosmos,

and bright galaxies cluster
where dark matter is thickest.

Dark matter provides
the scaffolding that underlies

how the matter in the universe
structures itself,

where it goes,
and what it does.

So,
dark matter dictated

how the universe unfolded.

It seems as if
out of the hot big bang,

dark matter condensed first,
before atoms,

and dark matter began
to become clumpy.

The clumpiness then began
to attract atoms

as they were formed later,
and that formed galaxies.

And in some sense,
the dark matter therefore

provides kind of a womb that
allows the birth of our galaxy.

Dark matter holds
the universe together,

but it also threatens
to destroy it.

One of the most
amazing discoveries

of the past few decades
is dark matter,

the fact that there's much more
matter in the universe

than we were aware of.

And all of that matter
has a lot of gravity.

So all this new matter,
all this new gravity

must be slowing down
the expansion of the universe.

Dark matter may even
tip the cosmic scales

in favor of gravity,

defeating expansion
and pulling the entire universe

towards a death by fire.

It's called the big crunch,

and this is how
it would play out.

For a fraction of a second,
the universe stalls,

poised between
expansion and contraction.

Then, gravity kicks off
a cataclysm.

When you looked out,
the very first things

as it began to turn around
that you began to see

is that galaxies, instead of
moving away from us on average,

would begin to be moving towards
us on average.

The whole universe would look
like it was coming to get us.

As space
contracts further,

the density of matter increases,
gravity gets stronger,

temperatures soar
as the crunch gathers momentum.

Galaxies begin to collide,

gas clouds begin to collide,

planets slam into the earth.

Black holes will execute a death
dance around each other.

Temperatures, of course,
will continue to skyrocket.

Matter, space,
and time implode

until everything in the universe
is compressed

into a tiny speck of infinite
mass, heat, and pressure.

For the last stages
of the big crunch,

galaxies will collide
and form a primordial atom.

And then, life as we know it
will be impossible.

We're back
to where it all began,

back at the big bang.

The universe that we live in
will cease to exist.

But some believe a big crunch
could herald a new beginning.

We don't know what the end point
of a big crunch would be,

because the laws of physics
break down.

It's possible, and indeed,
philosophically very pleasant,

to imagine that that crunch
would somehow end up evolving

into an expansion again, and you
could have a cyclic universe

which goes on forever.

Perhaps at that point, we will
recreate another big bang.

It's conceivable that as
everything comes together

in the crunch, something sort of
keeps it from just continuing

and pushes out in a hot,
dense, smooth state,

and from the other side,
it looks like a big bang,

and a new universe has been
created.

Our big bang might have been
someone else's big crunch.

But just when
scientists came to terms

with dark matter's big crunch,
the universe threw them

another, even bigger curve.

Some ghostly force seemed to be
sending us hurtling toward

a completely different death.

My postdoctoral
scholar showed me the results.

I nearly fell off my chair.

Gravity and expansion
battle for control

of our universe
for 14 billion years...

...expansion
Pushing it outwards,

gravity pulling it in.

With dark matter in its corner,

gravity seems to be
the inevitable winner.

The extra mass will drag
the universe into a big crunch,

until a stunning discovery

revolutionizes our understanding
of the universe.

Around 1990, two teams of
researchers decided to measure

the expansion history
of the universe

to determine whether
it's been slowing down so much

that it'll eventually have
a big crunch,

or whether it hasn't been
slowing down much

and will eternally expand.

Astronomer alex filippenko
was on one team.

Saul perlmutter led the other.

We realized that it was possible
for the first time

to go and actually make
a direct measurement

of how much the universe had
been slowing down in the past.

Both teams want
to measure

the speed of distant galaxies.

But because the galaxies are
too dim and too far away,

they look for something
brighter.

Billions of light years
from earth, a star detonates.

This is a supernova,

a dying star's
brilliant final gasp.

It burns brightly, 5 billion
times brighter than the sun,

but briefly.

Perlmutter and filippenko
have a window

of just one or two weeks
to measure

how much the galaxy it sits in
is slowing down

as it moves away from us.

The teams look for supernovas
for eight years.

They measure 42, and the results
seem impossible.

We plotted the points
on the graphs,

and...it didn't make any sense.

They were not slowing down
at all.

They were actually speeding up.

What both groups found
stunned the world.

In the last 4 or 5 billion
years,

the universe has actually been
speeding up in its expansion.

An accelerating universe,

propelled by something
mysterious.

For so long, we've been arguing
whether the universe would

expand forever or collapse
back in on itself,

but nobody thought
the answer was going to be

that the universe was
accelerating,

going faster and faster
all the time.

The acceleration
bewilders the scientists.

It seems to defy
the laws of physics.

Imagine i've got a baseball

and i throw it straight up.

And instead of slowing down
once it leaves my hand,

which is what
normally it will do,

it begins to slow down at first,

but then it starts
speeding away.

Somehow, it's getting energy.

The new energy seemed
to be coming from nothing,

the vacuum of space.

The word "vacuum" to a scientist
means completely empty space,

no particles there at all,
no temperature,

no energy to speak of.

But there's an intrinsic energy
in space and time.

Empty space has energy,
and that energy produces

a gravitational repulsion,
a kind of anti-gravity.

Without a clue what
this force is or how it works,

all scientists can do is give it
a name -- dark energy.

We could have called it
we-don't-know energy.

We could have called it
anything.

But we don't know what it is,
and dark or not,

it's the biggest mystery
in physics.

Nasa calibrates
its finest space telescopes

to measure how much dark energy
is out there,

and the result is mind-blowing.

It dominates the mass of
the universe by nearly 3-to-1.

And the more space expands,

the more dark energy
there seems to be.

Dark energy is the energy
of nothing,

and it's repulsive.

Therefore, as this dark energy
repels galaxies,

there's more of it,
there's more vacuum.

And so there's more repulsion,

and perhaps that's the reason
why the universe is accelerating

right now
rather than slowing down.

Dark energy seems to
kill the big crunch theory,

but scientists aren't yet sure
how dark energy,

expansion, and space
are connected.

If a volume of space doubles
in size,

does the dark energy
inside it double, too?

Or does it increase more?

A 1-to-1 relationship leads
to a steady expansion.

The universe ends
in a big freeze.

But if dark energy increases
above and beyond expansion,

a new, even more terrifying end
awaits the universe -- a big rip.

In a big rip scenario,
the expansion is so great

that even the galaxies begin
to expand internally,

which means that literally

our bodies
are going to be ripped apart.

Scientists calculate

just how the big rip
will play out.

One by one, the galaxies in
the night sky will blink out

as space pulls them away
from the earth

faster than the speed of light.

60 million years before the end,
Dark energy overcomes gravity

on smaller and smaller scales.

First galaxies start
to rip apart,

then insides of galaxies
will begin to rip apart,

and then solar systems will
begin to rip apart...

Then planets...

And then rocks, people, atoms.

The end will
be mercifully quick.

In the space of a few minutes,

all the stars and planets in the
universe will be destroyed,

their remains pulled apart
into ever-smaller pieces

until finally,
when the universe has

less than a second to live,

the subatomic particles
that made all matter

will be destroyed,

and all that remains will be
individual photons

becoming scarcer and scarcer

as the space between them
expands.

All you're left with is very low
energy light

that gets stretched
and stretched

until it might as well
not exist at all.

The last thing to go --

the empty vacuum
of space itself.

It'll be pulling on the universe
so hard,

it could tear the fabric
of the universe apart.

Reality could dissolve.

Will the universe end
with a big rip,

or a big freeze?

The answer is locked inside
the mystery of dark energy.

Solve that, and the fate
of the universe becomes clear.

The end
of the universe is coming.

But how will it play out?

For a time, a big crunch
was the likely answer.

Dark matter, the invisible bulk
of the universe,

causes space
to fall in on itself.

Galaxies collide.
Planet merges with planet.

Everything becomes hotter
and hotter, denser and denser.

The universe is like
one giant star.

Dark energy kills
the big crunch theory.

It acts like rocket fuel
for the expansion of space

between galaxies.

They're not just coasting.
They're getting pushed outward.

Only two possible fates
remain --

a big rip or a big freeze.

Both scenarios rely
on dark energy.

For the universe to be torn
to shreds in a big rip,

dark energy must increase
exponentially in the future.

But a big freeze requires
a steady increase

in dark energy,

pushing galaxies away
from each other.

We can't write the last chapter
of our universe

until we understand the nature
of dark energy.

May 2009.

The european space agency
launches the planck satellite

to search for the birth
of dark energy.

Its ultra-sensitive telescope
peers through space and time

back through billions of years,

towards the beginning of
everything, to capture this.

This is our universe
as it appeared

over 13 billion years ago,

380,000 years
after the big bang.

So what planck has done
is take a picture

of the early universe

and told us about what
the early universe is like

and given us our most detailed
and accurate picture

of that moment in time.

The universe in this picture

is a hot soup of protons,
electrons, and photons.

Hydrogen atoms have just started
to form,

and it's the light from this
genesis of matter

that we see here.

Blue areas are colder.
Reds are warm.

Eventually, those hot spots,

those red spots you see
in the map,

are going to form large
superclusters

made up of hundreds or thousands
of galaxies.

Each one of those galaxies will
contain billions of stars.

Gravity
and expansion alone

appear to drive the formation
of these embryonic galaxies.

Dark energy doesn't seem
to have switched on yet.

So, when did dark energy take
control of the universe?

Astronomer brenda frye
is part of a team

using massive
ground-based telescopes

like this one at kitt peak,
arizona.

She peers back in time
to capture the universe

through its childhood
as it was growing.

Right.
So this is an aluminum plate,

and into this plate are
drilled 640 individual holes.

Each one is put at a very
specific place on the mask

which will correspond to one
particular galaxy in the sky.

During each observation,

the light from 640 individual
galaxies is collected

using fiber optic cables.

The speed and relative position
of each galaxy is measured

to pinpoint exactly where it is
in space.

So far, the team
has accurately mapped

around a million galaxies
in 3d,

and this is what they look like.

Each one of these fuzzy patches

is a fully grown galaxy

containing around
200 billion stars.

This is a very basic
measurement,

and we think that
this will be able to help us

to get a grasp into the nature
of dark energy.

Scientists compare
this adolescent universe

to its baby pictures.

It shows dark energy emerging

when the universe is
half as old as it is today.

About 8 billion years
after the big bang,

this expansion of the universe
begins to accelerate,

and we're in the middle
of this acceleration.

The data also shows
that as space expands,

dark energy
increases in lockstep with it.

If you had a box and you put
some dark energy in it,

and then you went and you
weighed that box...

Now you take the box,
you make it twice as big.

You don't open it.
You don't put anything in it.

You weigh it again, it's gonna
weigh twice as much.

This remarkable
observation means

that we should be safe
from a big rip.

Dark energy will continue
to increase gradually.

The universe is heading
for a big freeze,

and scientists can finally
calculate a timeline

for the end of everything.

It now seems
that we live

in an almost perfect universe,

with just enough gravity
to hold the galaxies together

and just enough dark energy
that it will expand forever

without ripping itself
to shreds.

Cosmologists can finally
envision the end of it all.

30 years ago,
It was debatable.

But now, it appears
that the universe most likely

will suffer a deep freeze.

If you look at the data,
it stares out at you.

In a big freeze,

dark energy pushes galaxies
further and further apart,

but they remain intact.

The stars inside them
fade away.

Every star you see in the sky,
including our sun,

is burning through
its nuclear fuel.

The gas will run out,
stars will stop being made,

and the ones that exist are it.
those are the last ones.

A hundred trillion
years from now,

the biggest stars will be
the first to go extinct.

Big stars burn bright
and die hard.

The star's core collapses,

unleashing a supernova.

Then gravity crushes
the dead star down

to a single dense spot.

The bright star
is now a black hole.

Sun-like stars go next.

As their supply of hydrogen
runs out,

they swell to a bloated fireball

over 200 times
their current size.

And when the core
has no more hydrogen,

it's going to bloat up
into a red giant star.

Now, red giant stars are so big,
they will actually

eat up their own planets.

We know of examples
of red giants

that go all the way out
to where the orbit of jupiter is

in our solar system.

Its fuel exhausted,

the sun-like star
gives in to gravity

and shrinks to a white dwarf,

a dense ball of matter

just a few thousand miles
in diameter.

It will glow with heat
for a further 10 billion years

before cooling to a black dwarf,

a ball of compressed carbon,
perhaps even diamond.

As the biggest stars die,

the universe
will slowly turn red.

The blue stars
will blow up,

and then the slightly less blue
stars will blow up,

and then stars like the sun
will fade away and die,

leaving just the red stars
to exist.

Red stars
are the smallest

and coolest in the universe.

They burn their fuel slowly.

But, after another
10 trillion years,

even these smallest
of dwarf stars

will use up their fuel.

Stars as we know them
will cease to burn energy,

and the night sky
will turn black.

Black holes,
the corpses of dead stars,

and cold clouds of gas and dust
are all that remains.

The age of stars is over.

The age of black holes begins.

Black holes become
the fundamental building block

of the universe.

A galaxy will basically be
a supermassive black hole

in the center, with smaller
black holes orbiting it.

In some ways, it's kind of
a ghost universe.

It's the corpses,
the zombie stars,

that will take us
into the future.

Zombie galaxies
filled with black holes

continue to evolve.

They sweep up the dead remains
of stars.

Black hole merges
with black hole.

They'll eat each other
and they'll get bigger,

and maybe they'll fall into
the supermassive black hole

and it'll get bigger.

The universe will still be
an exciting, dynamic place,

it's just that the time scales
you're talking about

are now trillions of years

instead of thousands
or millions of years.

Any material that
evades the pull of a black hole

eventually dies away
as its protons disintegrate.

A proton, one of the fundamental
building blocks

of atomic matter,
of what makes us up,

can just spontaneously
fall apart,

and it turns out this takes
a tremendously long time.

but even that will go away.

All that will be left
is a sea of black holes.

Scientists used to think
black holes were immortal,

but even these will one day die.

Now we're talking about
time scales

of unimaginable length --

quadrillions of years
into the future.

But on that time scale,

even the black holes
begin to evaporate.

They'll get smaller and smaller
and smaller,

and then, poof, they'll be gone.

The universe will end

when the last remaining
black hole dies.

As it gets smaller,
the evaporation rate

increases exponentially.

Before long,
it reaches a size

a billionth of a trillionth
of a trillionth of an inch.

At that instant,
the laws of physics break down,

and the last black hole explodes
in a flash of gamma rays,

leaving nothing.

And it will die
in a sudden burst of light,

the last burst of light

in the entire history
of the universe.

The big freeze is coming.

The universe will suffer a cold,
slow, dark death

which will play out

over trillions upon trillions
of years.

But quantum physics leaves
the door open

for an alternative end,

an event so powerful,
so destructive,

that it could destroy everything
we see in the blink of an eye.

And it could happen tomorrow.

The end of the universe --

it's coming.

Dark energy accelerates
the space between galaxies,

pushing everything we see
to a long, cold,

and very slow death.

Unless, that is, something
bizarre happens first.

A monster called
phase transition

is lurking in the shadows,

and it could annihilate
the fabric of space and time

at any moment.

When we cool down water,
it turns into ice.

The properties change.

If you lived in the water,
when it changed to ice,

your world
would be very different.

Water phase changes
into ice when it loses energy.

I once left a water
bottle in my car overnight.

It was still liquid,
but the moment i touched it,

the slight imperfection,

the little bit of ice
that it formed, spread,

poof, and filled up
the whole bottle.

That rapid change
to something new

is called a phase transition,

and bizarrely, the same thing
could happen to empty space.

We've really come to understand

that we shouldn't take
for granted that...vacuum,

what we call nothing,
is actually stable.

It could be that the energy
stored in empty space

is just waiting to be released
in a phase transition.

If it is, the laws of physics
will change.

A spontaneous glitch
in the fabric of space-time

could trigger
a phase transition of space,

a tiny bubble of new universe
that spreads out,

overwriting the old.

We know it can happen,
because it's happened before.

At the moment of the big bang,

the universe
that's first created

is completely different
to the one we see today.

Hot and without form,

there's no matter, no time.

The laws of physics
are different.

Suddenly, less than a trillionth
of a second later,

a glitch triggers
a phase transition.

A tiny bubble of the universe
we live in today forms,

and it races outward,

destroying everything it touches

like ice
spreading through water.

The energy that spills out
creates the space and time

that we exist in,

the building blocks of matter
and the forces that govern them.

All that energy was released,
producing all the matter

and radiation we observe
in the universe today.

The old universe
gives up its energy

to create the new.

But it holds some back.

The vacuum of space
still has energy bound to it.

Perhaps this is the dark energy
we see today.

Physicists believe
that someday in the future,

a brand new glitch in the fabric
of space-time

may trigger another
phase transition,

one that wipes us
and everything we see

out of existence.

This is a way to destroy
an entire universe,

because within your universe

are the seeds
of its own destruction.

It would spread out at the speed
of light in a death bubble,

ruining all the galaxies
as it passes through,

and ultimately completely
destroying our universe.

Nothing can survive
the expanding phase transition.

Planets, nebulas, galaxies --
all are ripped apart

as the boundary
of the bubble reaches them.

Inside this bubble,
protons are unstable,

atoms begin to rearrange
in a new form of matter.

As these bubbles
begin to expand,

a new universe is being born

in the corpse
of the old universe,

and the beginning
of a new law of physics.

And so, the expanding universe
we now see

may end in a phase transition,
but we won't know what hit us,

'cause the laws of physics
will change,

and we will essentially most
likely disappear

at the instant it happens.

This bubble will expand
at the speed of light,

and as the bubble passes you,

all the atoms of your body
rearrange themselves,

and you would never know it.

You would have no warning,
because the bubble itself

is expanding
at the speed of light.

You can't predict precisely
when it could happen.

You only have a probability.

So what you really
are predicting is a rate.

Does it happen once a year?
Once every 10 billion years?

Once every googol years?
Or whatever.

It's very possible that
these bubbles get nucleated

and grow about once every
10 or 20 billion years.

So it hasn't happened yet
because we got lucky.

It's unlikely it would happen
the next year or the next day,

but the laws of physics
absolutely allow it.

A phase change
may happen, or it may not.

The universe plays its cards
close to its chest.

And, like dark energy
and dark matter,

there may be more surprises
to come...

...surprises that will only
Add to the mystery and wonder

our universe holds for us.

Whatever the universe
is up to,

we still don't know enough.

We're in an age of discovery
right now.

Perhaps there is something else
out there

that we don't know about.

So, i'm not going to draw
any conclusions

until things are conclusive.

We don't understand
the nature of dark energy.

And without that understanding,
virtually anything is possible.

The future is still uncertain,

and that means
there's still a mystery.

And for me, that's the most
exciting possibility of all.

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