All language subtitles for The universe S07E04 Deep Freeze

Male narrator: In the beginning,
there was darkness,

and then, bang,

giving birth to an endless
expanding existence

of time, space, and matter.

Every day, new discoveries
are unlocking the mysterious,

the mind-blowing,
the deadly secrets

of a place we call
The Universe.

Between stars, between galaxies,

in the vast majority of space,

the temperature reads

more than 450 degrees
below zero.

- The deep freeze of space

would turn
even the air you breathe

into nothing more
than solid ice.

Narrator:
Now far-off frozen places

bring strange new mysteries.

- The Boomerang,
or a Bow Tie Nebula,

is actually colder
than the surrounding space.

Narrator:
Is there life on frozen worlds,

and why does the ultimate cold
change physics as we know it?

- We can take light
and slow it down

to the speed of a bicycle.

Narrator: Join us as we travel

in search of the lowest
temperatures in the universe

and the ultimate deep freeze.

[dramatic music]

♪ ♪

To appreciate the coldest places
in our universe,

it's important to remember

just how hot
all of existence once was.

[explosion]

We think of the big bang
as the ultimate hot event,

an excitement
of plasma and energy.

- When the universe
was really hot,

it was really without form.

There was just radiation
and particles

all zooming around,

turning into each other.

[explosion]

- The big bang
was a supremely hot event,

roughly a hundred million
trillion trillion kelvins.

Narrator:
Scientists measure temperature

using the Kelvin scale,

which begins at absolute zero,
the coldest cold we know,

a complete lack
of atomic movement.

On Earth,

the average temperature
is 288 kelvins,

or 59 degrees Fahrenheit,

two different ways of noting
the same temperature.

- When our universe
first formed,

it was so hot
that not even atoms could exist.

The entire universe was nothing
except for pure energy.

It took a hundred seconds

for our universe
to cool to the point

that it was only
a billion degrees.

- For a long time,
everything was so hot

that everything was divided
into subatomic particles,

not real traditional atoms

the way that we think
of matter now.

- The universe had to cool down

to a sufficiently low
temperature

that, first of all,
atomic nuclei could form,

and then neutral atoms
could form.

So without the universe
cooling down

to a sufficiently low
temperature,

we wouldn't exist.

- The universe kept cooling

until, 56,000 years
after the big bang,

it had cooled
to 9,000 degrees.

And the universe kept cooling

until, 380,000 years
after the big bang,

temperatures reached
about 3,000 kelvin.

And that was the point
at which matter and energy

finally parted company.

Narrator:
As temperatures dropped

to a level we can start
to comprehend,

it's important to understand

the relationship
between heat and temperature.

Heat is a measurement
of energy transfer.

Temperature is action.

- One of the easiest ways
to think of temperature

is as the constant collision
of particles.

You increase the amount
of gas in a room,

they start colliding,

one particle
against another,

like people in a busy crosswalk
on a Tokyo rush-hour afternoon.

As those gas molecules collide,
one with another,

the temperature goes up.

And as those people collide,
one with another,

their velocities
get transferred.

People get bumped forward.

Their temperature goes up.

Now, you start removing people,

those collisions,
they become less frequent.

Nerves become less frayed.

The temperature drops.

And in the same way,
as you remove gas from a room,

the collisions
become less frequent,

and it becomes cooler
to experience.

Narrator:
As mankind has spread out

over all the lands

that make up our home
in the universe,

areas of extreme cold
hold a special fascination.

- The coldest temperature
ever measured on Earth

was measured in Antarctica,
at over 125 degrees below zero.

Dry ice, like the ice
in this drink,

freezes out
at about 109 degrees below zero.

So you could have
naturally occurring dry ice

in the conditions
found in Antarctica,

it's so cold.

[wind blowing]

Narrator. Having found
the coldest place on our planet,

we now journey to the coldest
place in our solar system.

And surprisingly,
we don't have to go very far.

In fact, it's a place
where humans have already been.

- From what we know today,

the coldest place isn't exactly
where you'd expect it.

The lunar reconnaissance orbiter

has detected a temperature
of minus 397 degrees Fahrenheit

in one of those places
where the Sun's light

never quite reaches.

It's actually in the bottom
of a crater

of our Earth's own moon.

As the Moon
goes around the Earth,

it slowly rotates.

In fact, it rotates exactly once
per time around the planet,

allowing us to always see
the same face of the Moon.

But as it goes around,

sunlight is never able
to reach down

into the northern pole

or reach up
into the southern pole.

And craters in those two regions

are able to stay
in constant shadow,

because the sunlight

simply glances
past the edge of the crater

but never actually
shines inside.

Narrator:
Once scientists discovered

the ultra-deep freeze
on our own moon,

they realized
there was another place

that could be equally cold—

On a planet of fire.

- The realization that craters
like those on the Moon

could protect ices
from sunlight,

made us start to realize

that it's possible to find ices
in craters almost anywhere.

- Mercury is the closest planet
to the Sun.

And its sunlit side
is incredibly hot,

many hundred of degrees
above absolute zero.

But there's some parts
of Mercury

that are perpetually cold,

among the coldest places
in the solar system.

Narrator: It's Mercury's tilt,
or lack thereof,

which keeps its polar craters
in a deep freeze.

- The tilt of a planet
is called its obliquity.

Earth is tilted
about 23 1/2 degrees.

So our poles see sunlight

about six months
out of the year.

On Mercury, the obliquity
is almost zero.

So at some deep craters
at the poles,

there are spots that
are permanently shadowed

and never see sunlight.

Narrator: Although
the solar system gets colder

the further you travel
from the Sun,

the icy conditions
of the outer planets and moons

do not rule out
the possibility of life.

- Out in the outer edges
of our solar system,

we see a whole variety
of frozen moons

orbiting the outer planets.

Around Jupiter, Saturn,
Uranus, and Neptune

are all of these
little frozen worlds.

And what's amazing is,
maybe, just maybe,

some of them
could support life.

- Scientists have
overwhelming evidence

to support the notion
that on Jupiter's moon Europa,

there is an icy crust overlying
a liquid ocean underneath.

A common tenet of astrobiology:

where there is liquid water,
there's the chance for life.

- Scientists desperately want
like ice fishermen

to go and dig a hole
in the ice

and see what life
we can pull up,

'cause it could be that

deep in the heart
of those oceans of Europa,

just like deep in the heart
of the Earth's oceans,

there's volcanoes that support

not just bacteria
but entire colonies of life:

seaweed, sea cucumbers.

Life as we know it could exist
in the oceans of Europa.

Narrator: One of Saturn's moons
is a bit more active,

blasting snow out into space.

- Saturn's moon Enceladus
has ice geysers.

And scientists,

in trying to find a mechanism
for these geysers,

can find no good mechanism

that doesn't involve
liquid water.

Narrator:
Ice from the erupting geysers

on Enceladus
is coating nearby moons,

making them more reflective.

So how did scientists know
that frozen places

such as Europa and Enceladus
were geologically active?

The key lies
in their smooth surfaces.

- When the Voyager spacecraft
sent back

the first up-close images
of Saturn's moon Enceladus,

they saw huge regions
with no craters.

This tells us
that whatever craters were there

were filled in;
they were resurfaced.

It tells us,
this is an active object;

stuff's going on here.

The number of craters
on a planetary surface—

Moon, asteroid, planet—

Tells us about
the age of that surface.

On Jupiter's moon Callisto
or our own moon,

we see a lot of craters,

telling us
we have a very old surface,

just like this ice here.

This ice is obviously old ice.

It has cuts.
It has snow.

Obviously, it has not been
resurfaced for some time.

But there's a solution for that.

[rock music]

♪ ♪

[motor hums]

[beep]

♪ ♪

When planetary scientists
talk about resurfacing,

this isn't usually
what we have in mind.

Right here, we can tell
the Zamboni has passed.

We can tell there's been
a resurfacing event.

The Zamboni has passed,
clearing off the snow,

eliminating the grooves.

This is just like we see
on some of Saturn's moons,

like Enceladus and Titan,

where the fresh ice
without craters

tells us
that we have a young surface.

Narrator: The cold places
in the distant solar system

are of extreme interest
to scientists.

- Studying these outer bodies
in our solar system teaches us

about what the solar system
was composed of

in its very initial stages.

So these icy bodies represent

pristine material
that really represents

the beginning
of our solar system

and the building blocks

out of which
our solar system formed.

- Three, two, one.

We have ignition and liftoff

of NASA's New Horizons
spacecraft

on a decade-long voyage
to visit the planet Pluto

and then beyond.

Narrator:
Now a new effort is under way

to get a closer look
at some of the frozen leftovers

from our solar system's
formative years.

- The New Horizons mission
is NASA's latest mission

to explore the outer edges
of the solar system.

It's currently
the fastest-moving object

in the solar system.

And in 2015, it will reach

the once-and-former planet
Pluto.

Narrator: But after Pluto,
where to?

It's a once-in-a-generation
opportunity

to get a close-up look
at frozen objects

dating back billions of years.

The only problem:

scientists don't yet
have a second target

for new horizons.

Without one,
the probe is speeding

at more than
37,000 miles an hour,

straight for the icy blackness
of deep space.

If you want to know
how our sun and planets formed,

you just might find answers

in the deep freeze
of the distant solar system.

The New Horizons mission
to Pluto

is expected to provide
a wealth of new information

about the former planet.

But after its rendezvous
with Pluto,

what else can we learn

about the coldest corners
of outer space

and where we came from?

That's where thousands

of citizen scientists
across the world

are hoping
to make a difference

by finding a frozen needle
in a haystack.

- The New Horizons mission's
destination—

After it visits this
once and former planet—

Has yet to be found.

And right now, there are
scientists around the world

using some
of the largest telescopes—

Subaru, CFHT.

They're peering
into the region of space

where we expect to find

the object that will have
just the right orbit

that it will move itself

into the path
of the New Horizons mission.

Now, the catch is,
we have to find that icy object

in the outer solar system

by flipping through
all these thousands,

millions of images.

Narrator: This is a chance
for the general public

to be part of the exploration

of the coldest zone
of the solar system.

- This is where we need
the public's help.

We need everyone with eyes

to help us look
through all of these images,

to try and find
that piece of ice

that New Horizons will visit
after it visits Pluto.

Narrator: All it takes

is visiting a website
and looking at images,

and you could change
the course of history.

- And that's the amazing thing
about this project.

Narrator: It's expected
that this mystery object—

Whatever it is
and whenever it's found—

Will likely be cold,
very cold.

After all,
other Kuiper belt objects

are among the coldest places
in our solar system.

- As you get further
and further away from the Sun,

its energy is less and less
able to keep humans,

to keep spacecraft,

to keep anything warm.

You're down at temperatures
around 40 kelvin.

These are temperatures
when nitrogen becomes a solid,

when carbon dioxide
becomes a solid,

when all the things
we're used to thinking of

as the gases
in the air around us

start to become
the ground you walk on.

And when we look
at Pluto and its surface,

what we're seeing
is a completely frozen world

that sees so little sunlight

that the things
that we're used to—

Rivers flowing,
a glass of water to drink—

They can't exist,

because even the air we breathe
would freeze out to a solid.

Narrator: Another world
dominated by deep freeze—

A far-off
trans-Neptunian object

named for an arctic
ice goddess, Sedna.

- Some objects
in the outer solar system,

like Sedna,
have very eccentric orbits,

and they spend
the bulk of their time

in the solar system's
deep freeze.

However, when they come close
to the Sun

for a short period
of their orbit,

like 200 years,

they actually develop
a very thin,

a very tenuous atmosphere.

As the planetoid recedes,

that atmosphere collapses
back to the surface.

- Sedna is currently
about three times

Neptune's distance
from the Sun.

And upon closest approach,

it's 2 1/2 times
Neptune's distance.

Now, when it's farthest away,

it's about 33 times
Neptune's distance.

And a total orbital period
is about 11,000 years.

So the last time
it was this close to the Sun

was around 9000 B.C.

narrator:
So how did Sedna end up

with such a strange orbit?

- Some people initially thought
that Sedna

got ejected
out to where it is

by an interaction
with Neptune.

But since the closest Sedna
ever gets to the Sun

is 2 1/2 times
Neptune's distance,

this may be unlikely.

Instead, it's possible
that a passing star

actually dislodged Sedna,

from where it formed
near Neptune

out to where
it is right now—

Perhaps even one of the stars
in the cluster

in which the Sun initially
is thought to have formed.

Sedna may be just
the first known object

in a whole swarm
of other icy bodies

that would be the inner part
of this Oort cloud

that we think exists
out there.

Narrator:
When it comes to ice on Earth,

we're usually talking
about water

in its frozen state.

But ice in the deep freeze
of a place like Sedna

doesn't necessarily refer
to water.

- When most people
think of ice,

they think of the stuff
that comes out of their freezer.

But when scientists
talk of ices,

we're just talking
about a chemical transition.

We're talking
about how you can take

sometimes a gas,
sometimes a liquid

and drop its temperature,
leech out the energy,

until the atoms change how
they behave and become a solid.

In the outer solar system,
we find ammonia,

cleaning solution,

freezes out to a solid.

We find methane, natural gas,
freezes out to a solid.

Dry ice, something that we make
in labs here on Earth,

our solar system's completely
filled with it.

To a scientist,
ice is just something

that is in a different state,

that readily,
when you add heat,

becomes either a gas
or a liquid.

[rattling]

[rattling stops]

Some ices,
like this frozen carbon dioxide,

don't go from a solid
to a liquid, like water.

Instead, they go
straight into gas.

This type of ice is
the exact same sort of stuff

that makes up
part of the composition

of Pluto and Eris,

and many of the other
outer worlds

in our solar system.

When we see a comet,
when we see its tail

what we're actually seeing
is gases—

like the gases
coming off of this dry ice

that are getting streamed
out behind the comet

by the Sun's radiation.

Here on Earth,
it's just fun to play with.

- In this room, I'm surrounded
by blocks of water ice.

And indeed, water ice
is quite common here on Earth,

and even some other places
in the solar system,

like Jupiter's moon Europa.

But there are some places
that have other kinds of ices.

Saturn's moon Titan,
for example,

has methane and ethane ices
on its surface.

So water ice is not the only
kind of ice that there is.

Narrator: If you're looking
for a variety of ices

in one convenient location,

check out a comet.

- What's exciting
about studying comets

is that you're seeing
the material out of which

our whole solar system,
including the Earth, was made

flash-frozen at an early time
in the solar system's evolution.

Narrator:
Many scientists believe

comets are responsible
for Earth's vast oceans,

that eons of comet impacts
brought liquid water

to Earth's surface.

If that's the case,

these water-carrying comets
are likely responsible

for every living thing
on the planet.

So what's colder:
a comet or an asteroid?

That's what Travis S.
of Cedar Rapids, Iowa,

wanted to...

- Travis, comets are actually
colder than asteroids

over most of their journey
through space.

And that's because
comets start out

from the deep freeze
of the solar system.

That's really cold out there.

Asteroids are always
reasonably close to the Sun,

so they're, in general,
warmer than comets.

Narrator: Frozen comets,
icy asteroids.

But what about whole worlds
covered in ice and snow?

As we continue our search

for the coldest places
in the universe,

how low can we go?

And could life survive
under the icy surface

of a planet
wandering between the stars?

Cold plays a key role
in our universe.

It's a preserving medium,

a protector
against the scattering

of life-giving elements

such as hydrogen,
oxygen, and carbon.

The coldest places
in our universe

may hold answers
to fundamental questions

about where we came from.

So imagine a world
where it's always an ice age.

- In science fiction,
ice planets are common:

Hoth, Rura Penthe.

And who could forget
The Gun on Ice Planet Zero?

Narrator: But here,

science fiction
may be eclipsed by science fact.

Researchers are looking
for exoplanets

that could really be like Hoth,

the ice world from
The Empire Strikes Back:

large, rocky,
and snow-covered.

- Hoth was kind of
a realistic depiction

of what a planet might be
if it's sufficiently covered

with water that's then frozen

because it's too far
from the star.

You could have a planet
that basically has

just a frozen ocean

with no land continents
sticking out.

- It turns out
that an all-ice planet

is not only realistic;

it's happened to Earth
several times in our history.

Several occasions, the Earth
has completely frozen over.

We call that phase
"snowball Earth."

What happens is that
the ice sheet grows.

Earth cools.
We get more ice.

Ice is light.
It reflects off sunlight.

Earth cools.
You get more ice.

Reflect off more sunlight,
more ice,

and you get a runaway freeze.

- And then something changed,

and good fractions of it
warmed up,

and the glaciers melted.

In fact, you might expect
that the Earth

should be frozen
most of the time.

And the reason it's not
is that we have

a thick atmosphere
that retains a lot of the heat.

If we didn't have
the atmosphere,

Earth is at such a great
distance from the Sun

that, in fact, the water
should be frozen.

Narrator: By 2012,
scientists had identified

more than 700
extra solar planets,

a number that keeps climbing
every year.

Many are gas giants,

worlds that
more closely resemble

Jupiter and Saturn than Earth.

Detecting smaller snowy worlds
is a difficult

but not impossible task.

- Our current detection methods
tend to find very large planets

very close
to their parent stars.

As our detection methods
grow better,

we're likely to find
more frozen worlds.

Narrator: One such world:

the planet known
as OGLE-2005-BLG-390LDb.

It's believed to be about
five times the Earth's size

and, according to researchers,

could consist
of Earth like rocks and ice.

- The distance of this exoplanet
from its sun

is about the same
or may be a little further

than Mars is from our sun.

So in our solar system,

it would reside
between Mars and Jupiter.

- This particular exoplanet
is interesting

in that it has about
five times Earth's mass.

So it's considered
a super-Earth,

one of the lower-mass exoplanets
ever found.

But its temperature could be

only 50 degrees
above absolute zero.

So this would be an icy,
large, Earth like planet.

Narrator:
Another type of exoplanet

that's expected
to be dark and freezing:

rogue planets.

These are planets that,
for one reason or another,

have been hurled
from their solar systems,

cast off
into the icy nothingness

between stars.

- As far as we know,
planets form orbiting stars.

They don't have to stay there.

Gravity can actually
cause planets

to get slingshotted
out of their solar systems.

And this is where you can end up
with rogue worlds

not orbiting a star

but instead
traveling between them.

Narrator: Without a star
to provide warmth,

these planets are likely
to be dark, cold, and barren.

But cold doesn't mean dead.

And many scientists believe
that it's quite possible

that life could exist

under the frozen oceans
of a rogue planet,

even after a billion years
of wandering through space.

- Once they're far away
from the star,

they could freeze out
and become quite icy.

But it's also conjectured
that some of them

could retain a thick atmosphere,

which would then
keep the heat trapped in

that's created through
geothermal processes

and radioactive decay
within the planet.

So not all of them
are necessarily

completely frozen
at their surface.

Narrator: As our view
of the cosmos improves,

our estimate
of the number of rogue planets

keeps climbing.

- Recent simulation suggests

there may be twice as many
rogue planets in the galaxy

as there are stars.

Narrator: So what would happen
if a passing star

sent Earth spinning
out of our solar system?

As the entire planet goes rogue,

tumbling out into the
cold blackness of deep space,

would life survive?

- If that happened,
we'd very quickly radiate away

not all our energy,
but a lot of it.

The oceans would freeze.

The atmosphere
would become a solid.

We'd be left probably dead.

But imagine finding that world
later on,

intact with its cities.

We don't have to worry
about this fate.

But a civilization growing up
around a binary star—

You never know
what could happen.

Narrator: Humans may not
be able to survive,

but under the sea,
the way our water freezes

would give life
a fighting chance.

- One of the things
that helps keep fish

here on the planet Earth safe

is our normal water,
our H20 water.

When it freezes,
it freezes from the top down,

leaving the fish
safely protected

and swimming
beneath the frozen surface.

Now, if we go to another world,

one experiencing
a deep freeze.

That alien planet might have
ammonia oceans

or methane lakes.

And those liquids,
as they freeze,

they freeze from the bottom
all the way up to the surface,

leaving any fish living
in those frozen lakes

flapping around on the surface.

And that's not a good place
for a fish to be.

- If Earth were to become
a rogue planet,

the life-forms we see
in the very depths of the ocean

in subduction zones,

where these thermal vents
are filling the local ocean

with very, very hot water,

those life-forms would go on
like nothing ever happened

for millions,
maybe billions of years.

So it's very possible
that in the very depths

of an ice planet
that's gone rogue,

life could exist.

Narrator: Life could exist
on a rogue planet,

but not forever.

After all,
space is very, very cold,

and life-giving Earth remains,
thankfully, warmer.

- We're close to the Sun.

The typical place
in the universe,

far from any galaxy or star,

has a temperature of only
2.7 degrees above absolute zero.

That's the temperature
of space itself—

Really cold,
a really deep freeze.

Narrator:
So what is the coldest

naturally occurring place
in the universe?

It's a place
where a simple principle

you can test in your home
has led to a very big chill.

Having explored
the role of coldness

in our immediate neighborhood,

we now embark on a journey
to even more frigid places.

Astronomers
have recently discovered

what they think may be

the coldest star like object
ever found,

a mere 40 light-years
away from Earth.

It's what's called
a Y-class brown dwarf.

And according to scientists,

the temperature on its surface

is about that
of a warm spring day.

- Just in 2011,

we found the coldest
Y dwarf ever found.

And this is an object
that's so cool

that it's actually cooler
than you or I,

as human beings, are.

And this is an object that's
just 80 degrees Fahrenheit.

Narrator:
Our sun, by comparison,

registers at a toasty
10,000 degrees Fahrenheit.

So is this brown dwarf a star
or not a star?

- A brown dwarf
is sort of intermediate

between a planet
and a full-fledged star.

It's more massive than
even a Jupiter-sized planet.

But it's not massive enough
to ever have had

sustained nuclear fusion
in its core.

So a true star
has nuclear fusion going on

for a long, long time.

A brown dwarf has nuclear fusion
for just a short time.

- What brown dwarfs do is,
they bridge the gap

between what we call planets
and what we call stars.

So brown dwarf are cool,
not only because they are cold

but because they have
a lot of exotic stuff

going on in them.

Because they have
such low temperatures,

you can actually get clouds

in the outer atmospheres
of these almost-stars.

And these can be
either icy clouds,

or, in some cases,
they can be even iron clouds.

So we think
that some brown dwarfs

actually might have iron rain,

where iron condenses
out of the atmosphere

and rains down
into the lower layers.

But even with the coolest kinds,

you can get ices
much like the ones

that we see in the cloudy bands
that are on Jupiter,

in these almost-stars
but almost-planets.

Narrator: As we continue
to move out into the universe,

we get about 400 light-years
away from Earth

when suddenly,

stars appear
to wink out of existence,

the temperature drops,

and we encounter the inky
blackness called Barnard 68.

- Barnard 68 is significant
because of what you don't see.

It's just a black patch.

There's no light coming from it.

There's no light
coming through it.

It is a black, opaque spot
on the sky.

Narrator:
What was once thought of

as a hole in the sky

is now known
as a dark molecular cloud.

- Dark molecular clouds
are huge clouds in space

of gas and dust,

and when we say "dust,"

we mean little chunks
of water and silicates

not unlike you would sweep
off your countertop.

- Sunlight, starlight,
is only able to penetrate

the outermost regions
of the gas cloud.

As you move deeper
and deeper within,

this opaque system blocks

all the visible wavelengths
of light.

Only the infrared light
is able to make it

all the way
into the depths of the cloud.

And this protects the cloud
from heating up

and, in fact, makes
the inside of these clouds

one of the most shadowed places

and one of the coolest places
in the universe.

- Not only is Barnard 68

a nippy 16 kelvins
at its periphery;

as you work your way in,
it actually gets colder.

This is one cold cloud.

- One of the most amazing things
about objects like Barnard 68

is that right now,

they're some of the coldest
things in the universe.

But all it takes is a shock wave
to collapse them down

and trigger star formation.

And the first stars to form,
the largest stars to form,

are some of the hottest things
in the universe.

So in one instant,

one of these
dark molecular clouds

can become
the hottest thing around.

But the moment before,

they were the coolest things
in the universe.

Narrator:
Continue our trip,

and we've arrived
at the coldest place

we know of in the universe,

approximately 5,000 light-years
away from Earth.

We are now entering
the Boomerang Nebula.

This bow-tie shaped nebula

is actually colder
than the rest of the universe.

It's been chilled
by the outflow of gas

to approximately
negative 458 degrees Fahrenheit,

just one degree
above absolute zero.

- The Boomerang Nebula consists

of rapidly expanding gases
from a dying star.

And those gases expand
so quickly,

that they've cooled
to a temperature

below that
of the surrounding space.

- And part of the reason
it's able to achieve

its extremely low temperature

is simply because
it's made of expanding gas.

And expanding gas,
just like...

[gas hisses]

The expanding gas in this can...

[gas hisses]

Drops in temperature

as the gas spreads out
over a larger volume.

In fact, I'm able to take
this everyday drinking water...

This room-temperature
drinking water,

and freeze it with
the gas coming out of this can.

[gas hissing]

Now I'm not going to claim
that the Boomerang has ice,

but you can see
that a little expanding gas

can create
one heck of a deep freeze.

Narrator:
Using modern technology,

it is possible to create

even lower temperatures
in a lab.

So the true coldest place
in the universe

may be right here
on planet Earth.

Narrator:
In laboratory experiments,

we can reach
very low temperatures now.

In fact, the lowest temperature
ever reached

is something like
1/2 of a nano kelvin—

A billionth of a degree.

That's really low.

Narrator: As the temperature
in these experiments

approaches absolute zero,

weird things start happening
to matter.

Atoms react to the deep freeze

by clumping together
in a bizarre form of matter.

- This is where the atoms

all go into essentially
the same state.

That is, they behave
in a similar way

or even the same way.

These are weird,
weird substances.

Narrator: Super-cold substances

that can even
stop light in its tracks.

- One of the coolest things
we can do

is actually stop
a beam of light.

I know it sounds insane,

but we can take a beam of light
and be able to slow it down

and then play with it,
do whatever you want with it,

and then release it again.

One of the things that you can
do with that is stop it,

turn it into
an electrical signal,

and then re-release it
and turn it back into light.

And this is really interesting,

because it has all kinds
of practical applications

in electronics.

Narrator:
It's just another example

of how a really deep freeze
seems to transform

fundamental properties
of the universe.

Then again,
many scientists believe

the universe itself

is in for one final
fundamental transformation—

To a permanent state
of deep freeze,

from which there is no return.

The universe is doomed.

That's the belief
of a number of physicists

who study potential endgames
for all existence.

[explosion]

All of the heat and power

that was present
at the start of time

is slowly, quietly
slipping away.

- The whole story
of the history of the universe

starts from the injection

of this enormous amount
of energy in the big bang,

and watching it dissipate
as the universe expands.

Narrator: A universe
that begins with a big bang

and continues to expand

will eventually have
an energy shortage

for which
there is no solution.

[electricity buzzing]

- In a sense, the universe
is slowly winding down,

kind of like when you wind up
the spring in a wind-up toy

and you let that toy run
for a while.

Eventually, all the energy
gets used up—

There's nothing stored
in the spring anymore.

And you'd have
to wind it up again

to get it to do
something interesting.

- These toys have
some initial energy.

And as they go through
their little motions,

you're seeing that energy
be used up and dissipated.

Eventually,
these toys will stop.

They'll be
in their lowest energy state.

And there'll be no more possible
energy output from them.

- Well, once all the stars
have died,

once all the energy

has spread out uniformly
in the universe,

nothing interesting happens,

because, like the wind-up toy,
it's not wound up.

The universe
isn't wound up anymore.

Narrator:
But the universe itself

is getting larger,
expanding,

and there is no new energy
or heat coming into that system.

- If the universe
doesn't tear itself apart first,

the universe will end
as a deep freeze:

cold, dark,
and depressing.

Narrator: Suns burn out.

Planets are destroyed.

[explosion]

Galaxies collide, collapse,
ignite then fall apart,

frozen shells
of their former selves.

Over hundreds
of billions of years,

every bit of energy
in our universe gets used up,

lost to the ever-expanding void

as the entropy of our universe

reaches a final,
fatal maximum state.

- Eventually,
it will expand to the point

where there will be no heat left
in the universe.

That means
no chemical reactions.

That means
no biological reactions.

What you will see is...

- The final state
of our universe

is really just going to look
like a whole lot of nothing.

Nothing to see here,
no black holes,

no white dwarf stars,
no neutron stars,

not even any protons.

Just nothing.

- In a very cold,
dark universe,

you could say that this will be
the ultimate deep freeze.

Narrator:
But does it have to be that way?

Is there anything
that could prevent our universe

from ending up
as a frozen, dark void?

- In order to prevent an
ultimate death of the universe,

gravity—or some attractive
force like gravity—

Will have to pull back together

all the constituents
of the universe.

Right now,
the universe is expanding.

And the force of gravity
as we measure it

isn't enough
to pull everything together.

But we recognize
that we don't even know

all the players at work.

It's only been
the last 20 years

that we've even known
that dark energy—

Which is a repulsive force,
in essence,

something that pushes
the universe apart—

We didn't even know it existed
more than about 20 years ago.

- But it's conceivable
that someday,

the dark energy
that's accelerating

the expansion of the universe

will become
gravitationally attractive.

If that's the case,
and if there's enough of I,

then the universe
may halt its expansion

and re-collapse.

We don't know that
that will happen,

but it might happen.

In that case,
the universe will experience

a really hot heat-death,

where all the particles

are slamming
into all the other particles,

high temperatures,

stars get destroyed,
planets get destroyed.

You get a different form
of a lifeless universe,

one which is hot
instead of in the deep freeze.

Narrator:
Still, don't break out

the sunscreen yet.

- My bet is that
the universe will end up

in a very low temperature
deep freeze,

because it seems
that the current dark energy

might be the type

that will continue to accelerate
the expansion forever.

If that's the case,

the temperature of the universe
will become

arbitrarily close
to absolute zero—

The ultimate deep freeze.

Narrator:
Cold is a critical ingredient

of our universe.

- Cold is essential to having
the universe that we see,

because without a cold spot,
energy doesn't flow.

You need energy
to flow from hot to cold.

And it is the flow of energy

that leads to all the structures
that we see in the universe,

including ourselves.

So we wouldn't be here

if energy weren't
trying to flow

from hot, concentrated,
organized place

into the many forms
that it can flow into

in the universe.

Narrator: So the next time
you feel a winter chill

or get hit with a snowball,
just remember,

if it weren't for cold,
you wouldn't be here.

And if it's any consolation,
you won't be around

hundreds of trillions
of years from now,

when the universe enters
its final state of deep freeze.