All language subtitles for The Universe s07e04 Deep Freeze.eng

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 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.

Sync and corrections by n17t01
www.addic7ed.com

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

even atoms could exist.

The entire universe was nothing
except for pure energy.

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 out 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.

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 the 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 can

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.

[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 underway 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.

Narrator: 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 9,000 BC.

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.

[Rapid clinking]

[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?

Narrator: 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-- 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.

[Explosion]

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-390LB.

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

and, according to researchers,
could consist

of Earthlike 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 it's temperature could
be only 50 degrees above

absolute zero.

So this would be an icy,
large Earthlike 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 H2O 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 at 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.

Narrator: 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.

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 shockwave
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...
The expanding gas in this can...

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.

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 nanokelvin-- 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.

Narrator: 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.

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 some
day, 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 it, 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 places
into the many forms that it can

flow into in the universe.

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.

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