All language subtitles for From ice to fire 101 Frozen solid.en

Dr. Helen Czerski: Everything
around us exists somewhere

on a vast scale from
cold...to hot.

Whether living or dead,
solid or liquid, visible or

invisible, everything
has a temperature.

It's the hidden energy
contained within matter.

And the way that energy
endlessly shifts and flows

is the architect that
has shaped our planet

and the universe.

Across three programs,
we're going to explore

the extremes of the
temperature scale,

from some of the coldest
temperatures...

to the very hottest

and everything in-between.

In this program, we're going
to venture to the bottom

of the temperature scale.

We'll explore how cold has
fashioned the world around us

and why frozen doesn't
mean what you might think.

And we'll descend to the very
limits of cold, where

the everyday laws of physics
break down and a new world

of scientific
possibility begins.

Temperature is in every single
story that nature has to tell,

and in this series
we'll show you why.

[Dogs barking]

We've always
been familiar with the

experience of cold and heat,
but until recently we didn't

understand what
they actually were.

And as the era of modern
science dawned, that lack

of knowledge was becoming
a barrier to progress.

I'm here at the Radcliffe
observatory in Oxford and what

it was built to observe
is the cosmos.

Back in the 18th century,
this was one of the foremost

centers of the new
science of astronomy.

But while looking up there,
they discovered they had

a problem that
started down here.

Amy Creese is a
Meteorological Observer.

It's a role that was created
here over 200 years ago,

to solve a very specific
problem caused by temperature.

Creese: Early observers,
made quite meticulous records

of the temperature, and
that was because it was

important to know
what the temperature was like

in order to correct something
called atmospheric refraction,

which is how much the light
from a celestial object bends

as it comes into the
Earth's atmosphere.

And that depends quite a lot
on temperature so, in order to

make very accurate
measurements of positions

of stars, the observers found
that they needed to measure

temperature as well, so they
kept very good records of that.

Czerski: So even those people
who are looking up at the cosmos

and thinking grand thoughts
about the universe needed to

know about this quite mundane
thing down here, which was

the temperature.

And you've got a book there
with some of the earlier

recordings in it.
- I do.

I have a book here
from 1776.

It's some of the original
recordings from Thomas Hornsby

who founded this observatory,
and several times a day--he was

much more keen than I am--
he came up here and took

measurements of
pressure and temperature.

But he also made some quite
funny notes in the margins.

For example, on the 26th
of January in 1776,

he wrote about
how the wine in his study had

started to freeze because it
had got very cold that day.

Which is a very important thing
for a scientist to know about.

Creese: And I'm glad that
he wrote about it.

Ha ha ha ha!

Czerski: These are some of the
earliest regular measurements

of temperature ever made.

And they were only possible
thanks to one of the greatest

scientific innovations of
the 18th century:

the modern thermometer.

The first thermometers
were simple tubes filled

with liquid, and if you put
them in something warm,

the liquid level would go up,
and if you put them

in something cold, the
liquid level would go down.

That's not much use if
you're trying to establish

a universal temperature scale
that everyone can agree on.

Every inventor had their own
idea of what that scale

should be, and so no two
thermometers were alike.

A solution that was arrived
that was really clever.

It was to say that perhaps
we can find fixed points.

So perhaps there are
situations which are

absolutely always the
same temperature.

And then everyone can agree
on those points on the scale,

and then we can all
calibrate our instruments.

The choices that stuck were
those made by Daniel Fahrenheit,

who was a Polish physicist,
and he chose 3 fixed points

that everyone else
then followed.

So the first one of his fixed
points was this mixture here--

ammonium chloride and
liquid water and water ice.

And that is a very interesting
type of mixture because,

when you mix those 3
things together, they will

find an equilibrium at a
very specific temperature.

And Fahrenheit chose that as
his starting point, so this is

at 0 degrees Fahrenheit.

Fahrenheit's second fixed
point was a mixture of water

and ice, which will
always settle at the same

temperature,
32 degrees Fahrenheit,

more familiar to us these days
as 0 degrees Celsius.

And then there was one more
fixed point, and Fahrenheit

chose the temperature of
the human body. So if you put

a thermometer under your arm

or under your tongue,

Fahrenheit said that was
96 on his scale.

And that was the beginning
of the Fahrenheit scale.

All of those scientists and
engineers could calibrate

their thermometers using those
same 3 points. They could

divide up the temperature
scale in exactly the same way,

and finally the really science
of temperature could begin.

The thermometer opened up
a whole world

of possibilities for
astronomy, meteorology,

and of course medicine,

but it also brought with
it a paradox.

While we now had a standard
scale to record temperature,

we still didn't have any
scientific explanation of what

temperature really was,

of what made
things hot or cold.

Some of the earliest
scientific theories proposed

that temperature was
a physical substance.

One idea was that heat was
a weightless liquid, called

"caloric," that
warmed things up.

Another theory, suggested
that cold consisted

of "frigorific" particles.

These ideas persisted until
the late 18th century,

when they were thrown
into doubt by a discovery

about heat that would
ultimately transform our

understanding of cold.

In the 1790s, an American-born
inventor working in Germany

called Count Rumford applied
his mind to the study of heat.

And this is the report that
he wrote on his work.

And I love this document
because it's written

in a very human way.

Count Rumford was overseeing

the manufacture of cannons by
German artillerymen, when he

noticed something very
curious as they bored holes

into the cold metal.

And you can see just what that
was using a simple hand drill

and an infrared camera.

And I'm just gonna drill
through this piece

of metal here.

[Drilling]

And have a look on the
infrared camera. You can see

the spot around where I
was drilling has warmed up,

and I can feel the heat with
my fingers.

So even a simple drilling
experiment like this

can generate heat.

And this was exactly what
Count Rumford observed,

as he watched the
cannon-makers at work.

As they bored through
the metal, the cold iron

got hotter.

[Drilling]

Rumford had discovered
something fundamental

about temperature, of what
makes matter hot or cold.

Yet it would be nearly a
century before it was fully

recognized and explained.

And the first step towards an
explanation would come from

a completely different branch
of science altogether.

In 1827, Scottish botanist
Robert Brown was deep into his

research on flowering plants.

It was an exciting time in
biology because of the new

realization that inside the
very tiny plant cell, there

was an even tinier mechanism
making everything work.

Brown was particularly
interested in pollen.

So, he took pollen grains back
to his laboratory, suspended

them in drops of water,
and looked at them under

his microscope.

And what he saw was the pollen
grains sitting the water,

but from them, there were
emerging even smaller particles.

And when he watched
those particles, they were

moving, they were
jiggling about.

So the first thing that Brown
did was check whether they

were alive.

But they weren't. And he
tried with lots of different

materials, and what he saw
was that every time there was

a particle that small, just
on the edge of what

the microscope could see, it
would always be just jiggling

about, whatever it was made of,
and he no idea why that was.

The answer didn't come until
1905 in a paper written by

Albert Einstein that drew
together two crucial ideas...

first, that all matter
was made of atoms,

and second, that these atoms
were constantly moving about.

This finally solved the
mystery of Robert Brown's

jiggling particles.

They were being bombarded

by billions of
smaller, invisible atoms.

And Einstein's explanation

depended on one
fundamental point:

that the movement of atoms
was directly linked to

their temperature.

The physical existence of
our universe is all

about the relationship between
matter and energy, and this

paper was where that
story really started.

Einstein understood that heat
is just the energy that atoms

have due to their movement,
and the measure of that

movement energy
is temperature.

The more energy, the faster
the movement, and the higher

the temperature.

More than a century after
Rumford had puzzled over what

was heating up his cannons,
Einstein had explained it.

The very act of boring through
the metal was adding energy to

the atoms, increasing their
movement, and so making

the metal hotter.

This definition of heat also
means something profound

for our understanding of cold.

Because if heat is the measure
of energy of the movement

of atoms, then cold is simply
an absence of energy, a lack

of motion.

And this is vital to
understanding how every single

solid thing in our entire
universe came into being.

To show you why, we're in
Iceland, the perfect place to

explore the relationship
between cold and matter.

This is Breidamerkurjokull
glacier.

Here, matter exists
side-by-side in 3 very

different forms.

[Plop]

Nearly everything in this cave
is made of water molecules,

from the ice itself to the
water flowing through it

and even in the air.

Billions upon billions of the
same type of molecule, all

in the same place but behaving
in 3 different ways:

as a solid,
a liquid and a gas.

Each of these 3 states is
a consequence of temperature,

Of how fast the molecules
of water are moving.

And when the water reaches
its freezing point and changes

from a liquid to a solid,
something extraordinary is

happening in the hidden
world of its molecules,

something we can't see
by looking at ice at this

massive scale.

To understand it, we need
to look at something very

much smaller

and something that's also
frozen, even if it might not

look like it.

This is table salt, sodium
chloride, about as common as

you can get.

And even here, you can see
that salt's a little

bit sparkly.

If I put it under
the microscope,

now you can see
what's going on.

Those tiny little grains of
salt here have flat faces.

They're little cubes.

And every single grain is
the same, not a perfect cube,

but they've all got a cubic
shape and it's those flat

faces that are reflecting
the light and making

the salt sparkle.

And that's an indication
of something deeper down

in the structure of the salt.

Salt is made of equal numbers
of sodium and chloride ions.

The chloride ions are
assembled in rows and columns

so that they sit on
a square grid.

The smaller sodium ions fit
into the spaces in-between.

A salt crystal is just a giant
grid like this, a cube that's

a million or so atoms
long on each side.

This is the hidden
structure of a crystal.

Its atoms are no longer free
to move around each other.

Each one is locked in its
own place on the grid.

So the salt looks like
that here.

It would look like that
if I took it into a sauna

because it's frozen,
it's a frozen solid.

Freezing is simply what
happens when the molecules

of a substance no longer have
enough energy to move past

each other, and so they
become fixed in position.

And this doesn't always happen
at a temperature that we would

consider "cold."

For salt, it happens at
800 degrees Celsius.

Liquid iron freezes to
become a solid metal

at around 1500 degrees Celsius.

Liquid tungsten turns into a
solid at nearly 3500 degrees.

It's exactly the same process
that transforms liquid water

into solid ice at
0 degrees Celsius.

As with other liquids,
the molecules in liquid water

have enough energy to keep
moving past each other.

But as they cool,
the molecules slow down.

As water reaches its freezing
point, they arrange themselves

in tightly fixed positions
forming a hexagonal lattice,

a crystalline structure.

The beautiful symmetry of
snowflakes comes in part from

this microscopic,
hexagonal form.

Here, deep in this cave
of ice, it exists

on a massive scale.

And in fact, the very process
of cooling and freezing is key

to how the entire
planet formed.

Some 4 billion years ago,
the Earth was covered

in molten rock.

As we've seen in the striking
landscapes of Iceland,

that lava eventually cooled
and froze into solid rock.

And sometimes, the way it
cooled created something

truly extraordinary.

The hexagonal columns
of basalt

at Reynisfjara are one of
Earth's natural wonders.

And Professor Thor Thordarson,
a volcanologist from the

University of Iceland, is one
of the world's leading experts

in how they were formed.

Thordarson: So here we have
these beautiful regular

columns, and, these extend
at 10, 15 meters up

into the cliff face.

Columns like this are
fairly unusual.

Czerski: These columns tell a
story of how the intricacies

of cooling and freezing
have shaped

the fabric of our planet.

Thordarson: So this column here
which is about 80 centimeters

in width here, this width
is actually a function

of the cooling.

So if you think of a lava
flow, it starts cooling from

the surface, and it also
cool fastest where it is close

in contact with
the atmosphere.

As the lava cools and freezes,
it also shrinks, as its

molecules arrange themselves
into a solid structure.

This happens more quickly at
the surface, where the lava

meets the air, and more
slowly underneath, where it

stays warmer.

And if the rate of shrinking
is great enough, the cooling

lava at the surface is under
so much stress that it cracks.

And often the most efficient
way to dissipate this huge

buildup of stress is to crack at
an angle of 120 degrees,

the angle that gives
us a hexagon.

As the rock beneath the
surface also continues to cool,

these cracks extend
downwards creating the

colossal pillars we see today.

Czerski: Can you tell from the
size of these how quickly

these cooled?

I mean, did these take
a day to form

or a week or a year?
Can you tell?

Thordarson: Not exactly, but
I would guess between

10 and 20 years.

Czerski: This landscape
was formed

because lava
began to cool and freeze

at just the right
speed for the laws of physics

to create a masterpiece.

A little faster or slower,
and these columns

wouldn't exist.

They stand as evidence that
solid rock, the fabric of our

world, is frozen and the
architect that sculpted it

is temperature.

And as we humans have built
architectural wonders of our

own, so we've learned to
harness this potential

of cooling and freezing
to change the very nature

of matter.

This is Ely Cathedral.

It's been here for nearly
1,000 years and over

the centuries, countless
craftsmen have taken local raw

materials, limestone and oak,
and transformed them into this

vast and intricate structure.

But we're not here because
of those materials.

We're here to see
something else.

The stained-glass windows
here are breathtaking.

And they only exist thanks to
the unique properties of glass

that emerge as it cools.

It's only when you're
right in close like this that

you can really appreciate
these fabulous windows.

Each one of these panels is
illuminating the cathedral

with a story.

But the story that you can
see from down there is built

of 1,000 smaller stories
that you can only see up here,

because every single one
of these pieces of glass

is carrying its own
distinctive history of how

cooling shaped it and
locked in its properties.

To understand why, we're going
to meet someone who works

with glass day in, day out.

This is Walter Pinches,
a glassmaker carrying on

a tradition that's changed
little in 800 years.

How hot is it in there?

Pinches: 1250, 1300.

Czerski: 1300 degrees C.

It's only 2 meters away.
Ha ha ha!

Standing next to the fiery
glow of the furnace, it's easy

to think that the key
to glassmaking is heat.

But the real key to this
process is what happens when

the glass comes out of the
furnace and begins to cool.

And the color's just mixing into
the liquid as you go along.

Color's already twisted in,
you've already got your pattern.

Czerski: Cooling is a process
that craftsmen like Walter

learn to control precisely.

When the hot glass first
emerges, it's molten, so like

all liquids, its molecules are
still free to move and slide

over each other.

And this gives Walter a brief
window of time to manipulate

its shape.

But with every passing second,
the glass is cooling,

especially at the surface,
where it's in contact

with the air.

What's amazing about
this is that the inside

and the outside are different
temperatures, and right

in that molecular level,
everything in there is

different--everywhere
is behaving differently

because of its temperature.

Starting at the surface,
the glass begins to freeze.

Its atoms slow down and come
to rest in fixed positions.

And they do so in a way that's
unlike many other solids.

This is my favorite bit,
when it just blows up

like a balloon.

As we've seen when other
substances freeze, like water

or salt, their atoms become
fixed in the ordered structure

of a crystal,

but glass is different.

It cools more quickly, and so
its atoms don't have time to

arrange themselves in
a regular pattern.

Instead, they freeze in
the disordered, chaotic

arrangement of a liquid.

And this gives glass one of
its most valuable properties.

Unconstrained by a rigid,
crystalline structure, it can

be worked and manipulated into
an infinite number of forms.

This is the clever bit.

Hot molecules at the bottom
flowing quickly, cooler ones

at the top flowing
more slowly.

By precisely controlling the
heating and cooling of glass,

craftsmen like Walter can
create shapes and forms that

are truly unique.

The modern
world is built of solids,

like glass, that we have
created by controlling

the process of cooling
and freezing.

But that change, from liquid
to solid, isn't the end

of the story.

As a solid becomes colder,
it may look

outwardly the same,

but in the hidden world of
atoms and molecules, it can

still be changing in ways
that utterly transform how

it behaves.

And occasionally, when we've
failed to understand these

changes, our pursuit
of progress has ended

in catastrophe.

On the 15th of April 1912,
"Titanic," that unsinkable

symbol of luxury, struck
an iceberg and sank.

There were 2,200 people
onboard, and more than

1,500 of them died.

Titanic was built of
state-of-the-art steel.

As with glass, we'd learned
over centuries to make steel

incredibly strong, through
precisely honed processes

of heating and cooling.

Nobody doubted she was strong
enough to stand up to

the extreme cold of the Arctic.

To understand
what went wrong,

we've come to the Cammell
Laird shipyard in Merseyside,

where marine engineers
are working on their

latest project.

This is the Royal Research
ship "Sir David Attenborough."

When complete, she will be
one of the most modern

and advanced polar research
ships in the world.

And Captain Ralph Stevens,
will be responsible

for navigating this
huge vessel through icy

polar waters.

It's astonishing to
me that we're still building

ships of steel. You know,
we associate steel with

the Industrial Revolution
150 years ago,

and yet we are still building
ships from steel.

Why is it so good?

Stevens: Well, for us,
it's quite

a revolutionary material, and
that allows us to take in ...

It's quite common for us to
say some of the ice is as hard

as steel, and some of the
glacial ice, it's rock-hard,

and it's noticeably different.
When you hit a piece, you'll

hear a big clang
throughout the ship.

[Loud clang]

And so we want
the hull to be able to take

all of these forces that it's
exposed to without cracking.

And steel can do that job?

Stevens: Steel can do that.
The right steel can do that.

Czerski: But ironically, steel
may actually have been Titanic's

Achilles' heel.

Because what the engineers
of the day didn't fully

understand is that under
certain conditions,

the behavior of steel can
fundamentally change.

And the key to this
change was cold.

Steel, like many metals,
is ductile.

That means that it can
stretch when put under

stress, a property that's
useful in a huge structure

like a ship.

Few had imagined that, in the
cold, this crucial property

might change.

Got a sample
of shipbuilding steel here

with a little
notch in the bottom.

And I'm gonna do this
experiment twice--once

with this one, which is at
room temperature, and once

with an identical sample which
has been in the dry ice here,

-80 Celsius,
very, very cold.

The difference will
be very obvious.

So here we go.

First... the steel
at room temperature.

[Banging]

So, here's the cold one.

Down at -80 Celsius.

[Banging]

This is the sample at room
temperature, and you can see

that it bent, absorbed the
energy, absorbed the energy,

but it didn't snap.

Whereas this one, this is
the cold-temperature one,

and the surface looks really
different. There's all this

speckled pattern,
and that's the snap.

This was brittle fracture.

You don't want your ship
doing this.

Cold has changed the nature
of the steel, making it

more brittle.

And it's this that some
experts now think could have

played a significant role
in the "Titanic" disaster.

Analysis of metal taken from
the wreckage suggests that

rather than flexing on
collision with the iceberg,

the hull and rivets had become
brittle, and they fractured.

[Bang]

With this in mind, modern
shipbuilders are able to avoid

the mistakes of
their predecessors.

Stevens: We did some
calculations. We went through

the last 10 years
of temperatures our ships have

been exposed to, and that we
came to 25 degrees and then

reduced it down to -35.

So the game is that
you want the steel to give

a little bit,
but--and not snap.

Stevens: That's it. We can't
afford to have it fracture.

And if the worst
came to the worst,

you want that steel to deform
rather than crack.

Czerski: The tragic irony of
"Titanic" is that she was

constructed from metals

that we've
been using for centuries.

We thought
we understood them...

but cold altered them in
ways that no one expected.

Since then, we've been much
more aware of the hidden

changes that can occur within
materials, when they're cooled

far below their
freezing point.

And by pushing temperatures
lower and lower, we're

beginning to unlock some
strange and exciting new

properties of matter.

This is a material with
a very long name.

It's yttrium barium
copper oxide, and it doesn't

look like very much. There's
very strong magnets here,

and it's not responding to
them. It doesn't conduct

electricity, doesn't
seem very interesting.

But when you cool it down,
it changes completely.

Using liquid nitrogen,
we're reducing the temperature

of the disc to -196
degrees Celsius.

And now,
when I bring it close to

the magnets, something
unexpected happens.

It's levitating.

And it will scoot around
on a little track here

for quite a while.

So something's changed.
We've cooled it down.

The behavior
changed completely.

And that's because cold
has altered the material

at the atomic scale.

Materials conduct electricity
when electrons travel

through them.

But the atoms in a conductor
are an obstacle to the flow

of electrons, because as
electrons bump into them they

lose energy.

At extremely low temperatures,
the electrons can team up into

pairs, and then the attraction
between the electron pairs

helps them navigate through
the atoms far more easily.

So, when I bring the disk
close to the magnetic track,

a strong electric current
begins to flow in the disk.

This in turn, generates
its own magnetic field.

The magnets in the track and
the disc repel each other,

and so the disk levitates.

This is an example of
superconductivity. Once it's

cooled down below the critical
temperature, the properties

of the material change.
It becomes able to conduct

electrical currents without
any resistance, and it also

changes how it
responds to magnets.

The peculiar electromagnetic
properties of super-cooled

materials have given us
a powerful new tool

in engineering and medicine.

Some countries already use
a supersized version of this

magnetic levitation effect in
their high-speed rail systems.

Having no contact with the
track, trains run faster

and more smoothly
and efficiently.

And inside MRI scanners,
liquid helium super-cools

massive coils of copper wire
to a temperature of

-269 degrees Celsius.

At this extreme cold,
an electric current can flow

with almost zero resistance
which helps generate the

powerful and stable magnetic
field that the MRI

machine needs.

The extraordinary discoveries
we've made at extremely low

temperatures are now driving
one of the biggest scientific

quests of the modern age:

How cold is it possible to go?

And how do we get there?

[Liquid bubbling]

We know that as you cool
materials down, they tend to

turn into liquids and
then solids, but actually

the question of how cold you
could make something started

with gasses, and this was
the kind of experiment

that was used.

What I've got here are
4 beakers, each of which is

at a different temperature.

They range from -5
to 50 degrees Celsius.

Into each, we're placing
a syringe containing

15 milliliters of air
at room temperature.

This air will heat up or cool
down until it's at the same

temperature as what's
in the beaker.

So much science is about
waiting, and this is one

of those experiments.

But it's not the change in
temperature that's interesting

here, it's something else.

After 5 minutes, the air
that's heated to 50 degrees

has expanded from 15 to
16 milliliters, while

the air that's cooled to
-5 has reduced to

14 milliliters.

In other words, there's a
direct relationship between

the temperature of a gas
and its volume.

So the first scientists who
saw this kind of relationship

did something very
straightforward. They plotted

a graph that showed
temperature against volume.

And at the higher
temperatures, the volume is

higher, and as you go down to
the lower and lower and lower

temperatures, the
volume decreases.

And then there's a question.

Because at some point, even
though they couldn't see it,

if that line kept going,

it was going to pass through
zero volume,

and at that point and past
that point, what happens to

the temperature?
What does it mean?

And that was the first hint
that there might be a limit

on just how cold you can go.

This observation led to
a concept known as

Absolute Zero,
the theoretical limit of cold.

And now we know
exactly what it is.

On the Celsius
scale, it's -273.15--

a fantastically low
temperature, but below that

there's nowhere to go. That's
the coldest you can get.

[Wind howling]

And it remains a
theoretical point

on the temperature scale.

The Boomerang Nebula,
5,000 light years away

from Earth, is the coldest
place we know of in nature.

It's a star in the late stages
of its life that's shedding

huge plumes of gas.

As this gas expands rapidly
into the void of interstellar

space, it loses energy
quickly, resulting in its

unusually low temperature of
-272 degrees Celsius.

But even this is one
whole degree warmer than

Absolute Zero.

Though we've yet to find
Absolute Zero in the far

reaches of the Universe,
we're trying to create it

ourselves, much
closer to home.

At Imperial College London,
Professor Ed Hinds and his

team are working at the very
limits of the ultra-cold,

within fractions of a
degree of Absolute Zero.

It promises to open up a whole
new world of physics, which

could revolutionize our future.

The stuff they're cooling here
is tiny clouds of molecules.

Chilling them to
Absolute Zero requires two

phases of cooling.

First, using liquid helium,
they take them down to within

4 degrees of Absolute Zero,

but it's these last few
degrees that pose the problem.

Hinds: There are ways
to make helium a bit colder,

but to get to the millionth
of a degree, there is no fluid

that you can use
so instead, we use light.

By scattering the light,
the molecules will

get colder.

Czerski: Even at this
temperature,

the molecules still
have some movement.

Photons in the laser light
collide with the slowly moving

molecules, and in that
instant, what little momentum

they have is
transferred to the photons.

The photons are scattered...

but the molecules slow down
and so get even colder.

By using an array of different
colors of laser light in just

the right order, Ed and his
team can reach temperatures

within a few millionths of
a degree of Absolute Zero.

At these incredibly low
temperatures, materials begin

to behave differently at the
subatomic or "quantum" level.

In this "quantum" state,
they exhibit strange

properties which might lead
to a new type of computer.

A normal computer bit can only
represent a 0 or a 1,

but these quantum
materials can be 0 and 1

at the same time.

Link these multi-tasking bits
together, and they can do vast

numbers of calculations
simultaneously,

far faster than any
conventional computer chip.

Hinds: This opens up
the possibility, of quantum

computing, quantum sensing,
quantum cryptography, these

are all ways of doing useful
things but much better

than can be done with
conventional techniques.

Czerski: The world of
Absolute Zero

is a strange new realm
of physics

and one we're only just
beginning to get to

grips with.

But there's something ironic
about the vast efforts

required to push things

extremely close to
Absolute Zero...

because wait long enough,
billions of years,

and everything will get there.

The universe itself is cold,
and it's getting colder.

In 1964, in a small laboratory
in New Jersey,

astrophysicists Robert
Wilson and Arno Penzias

stumbled upon a discovery that
changed our understanding

of the universe forever...

revealing something profound
about its temperature.

And helping us decipher exactly
what they found is Tim O'Brien,

an astrophysicist at
The University of Manchester

and the Director of the
Jodrell Bank Observatory.

So, at some point during
every undergraduate physicists

degree, they hear the names
Penzias and Wilson.

Tell me what they did.

O'Brien: So these were
these two great characters

that, were working in the
USA in the 1960s.

They built themselves
a remarkable telescope.

It was incredibly well-built
to try and study the outer

regions of the Milky Way,
and they were measuring very

weak signals
coming from space.

But there was this last bit
of noise that they had no idea

where it came from. They
could not get rid of it.

[Faint hissing]

It was a faint hiss, and
that faint hiss came from

everywhere in the sky.

It had the same sort of
strength, the same brightness

of the radio signal
everywhere on the sky.

And they tried
everything. They tried all

kinds of things, didn't they?
- They did try everything.

At one point, they thought it
might be coming from pigeon

droppings in the telescope,
so a big telescope that

the pigeons were sitting in.
Washed it all out--

No, the stuff was still there.

Czerski: There remained only one
possible explanation for this

noise, and it had enormous
implications for our view

of the universe.

This strange
hissing was coming from beyond

our own galaxy.

O'Brien: It's what we
now know, and they didn't know

at the time, is what we
call the Cosmic Microwave

Background, the fading
glow of the Big Bang.

Where was
this coming from?

O'Brien: Yeah, it's coming from
the whole sky,

so it's coming from
everywhere,

and it's actually
the light that was emitted by

the universe about 380,000
years after the Big Bang.

The Cosmic Microwave
Background radiation

is invisible to
the naked eye.

but it fills the universe.

If we could see it, the
entire sky would glow

with a brightness that is
astonishingly uniform

in every direction.

What's remarkable is
that these microwaves

carry information.

They allow us to take
an accurate temperature

of the entire universe without
the use of a thermometer.

A thermometer has a
fundamental limitation,

which is that it has to be
touching the thing that

it's measuring.

And that's not much use if
you're looking at the rest

of the world, or even
the rest of the universe.

But the laws of physics
themselves offer another route

because every single object
in the universe

with a temperature
is radiating some of that

energy away as light,
and every single object has

a temperature.

The reason you can see me now
on the infrared camera is that

I have a temperature and so
I'm glowing in the infrared,

effectively a human
infrared light bulb.

The temperature of an
object determines the exact

wavelengths of the
light it radiates.

And this means there's a
precise relationship between

temperature and color.

So, when an astronomer sees
a star of a certain color,

they know it has a
certain temperature.

The reddest star visible to
the naked eye is Mu Cephei.

The wavelength of red light
that it radiates tells us this

star has a temperature of
around 3200 degrees Celsius.

And this is Spica, a star
that glows a brilliant

bluish-white.

This shorter wavelength
is indicative of a young,

hot star that's burning at a
temperature of around

22000 degrees Celsius.

Travel back the other way
towards longer wavelengths,

and things get cooler.

Eventually, you reach the very
long wavelengths of the

Cosmic Microwave Background.

They're not part of
the visible spectrum,

but the wavelengths of
these microwaves reveal

its temperature,

and that temperature is cold.

Today, the Cosmic Microwave
Background radiation glows

at a temperature of
-270 degrees Celsius,

Only 2.7 degrees warmer
than Absolute Zero.

Away from our nice warm bubble
on planet Earth, the universe

isn't just very empty,

it's very, very cold.

But that's not the end of
our story of temperature.

Because amidst the
vast swathes of cold

and nothingness, we're
starting to find other bubbles

of warmth out there in the
universe...

planets with a temperature
similar to our own,

which means they may have the
right conditions for liquid

water and complex chemistry.

These discoveries are
causing huge excitement among

scientists, because they
offer up the tantalizing

possibility, that maybe,
just maybe,

we might not be alone
in this vast universe.