Original subtitles

All around the Universe, stars are exploding.

They are cosmic catastrophes.

But to these scientists,

they are beacons in the depths of space.

They illuminate an epic battle

between two mysterious and invisible forces.

To one we owe our very existence.

The other is trying to tear us apart.

Now we're in a struggle of our own

to understand these colossal forces,

to learn to see beyond the darkness.

Space, time, life itself.

The secrets of the cosmos lie through the wormhole.

You, me, the sun, stars --

everything we see has one thing in common.

We're all made of atoms.

Atoms make up almost all the matter in the known Universe,

but...There is a whole lot more to the cosmos,

a side we're only just beginning to see.

Our bodies, our homes, our world,

even the vast void of space

is teeming with a mysterious substance...

...A form of matter so strange

that many scientists once doubted its very existence.

But in 2009, an incredibly sensitive particle detector

caught the first glimpse of it.

It's an Earth-shaking discovery,

and it's forcing us to radically reassess

our place in the Universe

and even our eventual fate.

As a boy, I used to lie in my room at night,

gripped by fear that something was out there in the darkness.

Was that a demon...

Or my clothes slung over the back of a chair?

I'd shine my flashlight at the furthest corner of the closet,

hoping to catch the phantom presence I sensed lurking there.

Well, I never did find anything in the shadows.

But just because you can't see something

doesn't mean there's nothing there.

In the 1960s, a young astronomer called Vera Rubin

decided to explore an area of space that was little-studied.

I had 2 children, one almost 2 and one almost 4,

and I didn't like the idea

of competing with astronomers for real hot topics.

Vera Rubin knew

if she studied something sexy, like black holes,

other astronomers would end up beating her to publication.

So instead she began surfing the galactic backwaters.

I'm not sure I really know

why I was studying galaxies,

except they seemed very mysterious to me,

and there was not a lot known,

especially about their motions -- almost nothing.

Vera first trained her telescope

on the Milky Way's closest galactic neighbor, Andromeda.

Like most galaxies, it had a dense central bulge of stars.

She expected the billions of stars

circling around this central bulge

to orbit just like the planets in our solar system,

obeying Isaac Newton's laws of gravity.

The further away they are from the center,

the slower they orbit.

This is a model of the solar system

that my father built for me

about 40 years ago, when he retired,

that shows exactly what Newton knew from his theories.

The four that you're seeing here --

Mercury, Venus, Earth, and Mars --

Mars is going the slowest, the Earth the next slowest.

Mercury is the most rapidly moving.

Because the force of gravity is considerably less for Mars

than it is for Mercury,

the orbit is correspondingly slower.

This is exactly the pattern Vera expected to see

when she studied stars as they orbited in their galaxies.

The further from the center, the slower they should be moving.

But that's not what Vera found.

It took us about two years

to get velocities of 90 stars in the Andromeda galaxy.

And the results were rather startling.

We found that all of the stars

were moving at the same velocity,

the same number, 250 kilometers per second.

For the next few years,

every galaxy Vera looked at

gave her the same seemingly crazy results.

All the stars all the way to the edge of the galaxies

were moving at the same speed,

completely different from the way the solar system works.

The only explanation

was that the force of gravity did not get weaker

the further a star was from the center of a galaxy.

But that could only happen

if the galaxies had more mass than astronomers could see.

The explanation was that there must be

very significant amounts of matter that are invisible.

In fact, perhaps 90% or 95% of the material in the galaxy

is invisible.

This was a truly revolutionary idea.

Galaxies might be filled with an unseeable substance,

something scientists could only think to call "Dark Matter."

But such a radical theory demanded ironclad evidence.

Soon dozens of astronomers were checking Vera's observations,

either struggling to disprove her

or scrambling to discover

what or where this mysterious Dark Matter might be.

I did find it amazing, and amusing,

that I had picked this field because I was interested

in doing something that no one would care about,

and suddenly I was involved with lots and lots of astronomers

who had ideas and observations, and it was a hot topic.

Across the Atlantic in England,

leading cosmologist Carlos Frenk

began to investigate the idea of Dark Matter,

using not telescopes but equations.

Take Newton's laws of gravity and feed them

into a highly sophisticated computer simulation...

Then go for lunch.

This is the cosmology machine, a very large supercomputer

whose only purpose is to simulate the Universe.

It's made up of 1,300 computers all working together.

Even then, it takes months

to complete a simulation of a small part of our Universe.

This is awesome computing power almost beyond imagination,

but that's what it takes if you want to emulate the Universe.

Carlos started out his simulation

with what scientists think the early Universe was made of --

a giant cloud of gas floating in empty space.

Then he sat back and waited

to see if his cosmology machine could build a galaxy

like the ones we see.

What happens if you try to make a galaxy in a computer

using simply the material that we can see?

What happens is, you end up with a failed galaxy.

Stars form, they evolve,

the biggest ones explode as supernovae,

and they inject so much energy.

But there just isn't enough gravity

to keep these gases together,

so the galaxy essentially blows itself apart.

The gas dissipates, leaving very little behind.

This is not how our Universe is made.

So Carlos started to add Dark Matter to his equations --

first a little, then more,

and eventually five times as much of it as visible matter.

After several weeks,

something strange came out of the cosmology machine --

strange because it was so familiar.

This is a computer simulation of the formation of the galaxy,

now with invisible Dark Matter and gas, shown here in green.

About a billion years after the Big Bang,

clumps of Dark Matter formed.

Gas fell into these clumps, turning to stars.

But attracted by the force of Dark Matter --

invisible Dark Matter, gravity --

these clumps came together,

fused to build ever larger structures,

so that 10 billion years later,

a beautiful spiral galaxy like our Milky Way was formed.

Carlos has shown

that galaxies should form when filled with Dark Matter.

But is there any way to prove

that this is what actually happened?

In Edinburgh, Scotland,

Richard Massey is still trying to answer that question

and is pioneering a new way of detecting Dark Matter --

gravitational lensing.

It's all thanks to the genius of this man.

Albert Einstein saw space in a new way --

as a bendable, malleable material

that is influenced by gravity.

Anything that has mass -- a star or a galaxy --

can bend the fabric of space and act like a lens.

As it bends space, so the light traveling past it is also bent.

Dark Matter doesn't reflect light,

it doesn't absorb light, it doesn't emit light.

Light just passes straight through it unaffected.

So we have to look for something else --

the way it affects, gravitationally,

things around it that we can see.

Now, this idea of light being deflected and bent

by warped space-time sounds crazy,

but actually it's very familiar.

We see light being bent all the time --

every time you look through the bottom of a wineglass.

Let me show you what I mean.

Although the bottom of the wineglass is transparent

and light passes straight through it, you know it's there

because of these distorted images in the background.

Dark Matter is exactly the same.

It bends light, through a different physical effect,

but the net result is the same -- that these images

of very distinct galaxies appear distorted

whenever there's some Dark Matter in front of them.

For two years,

Richard has been leading a team of international astronomers

and directing a fleet of telescopes

to scour one section of the night sky

for every single visible gravitational lens arc.

So, what we're seeing here is gravitational lensing in action.

All of the yellow blobs that we see are galaxies

in a group which are fairly near to us.

These strange shapes, these arcs,

are actually very distant galaxies,

and the light from those distant galaxies

has to pass nearer the yellow blobs,

which are foreground galaxies.

And because they bend space,

they bend the light rays from the distant galaxies,

distorting their images

into these circular, arclike patterns.

But when Richard runs calculations

on the amount the light from the distant galaxies is bent

and compares it to the visible mass of the foreground galaxies,

he finds it's warped much more than it should be.

His conclusion?

An invisible shroud of Dark Matter

must engulf all the galaxies.

From the amount of gravitational lensing they produce,

we find that there's about five times as much

of this Dark Matter as there is the ordinary material.

So what we can see is but the tip of an iceberg

in the Universe -- most of it is Dark Matter.

Everywhere astronomers look,

they are starting to sense the heavy presence of Dark Matter.

But Richard Massey is about to go a huge step further

and take the first picture of this cosmic giant.

And when he does, we've discovered

that Dark Matter is more important to us

than we ever imagined.

This is a real picture of the sky.

The Hubble Space Telescope sees an incredible number of galaxies

with minute precision.

So we're able to measure their shapes very accurately,

and it's the distortion in those shapes

when the light from those galaxies is bent

on its way to us, past Dark Matter,

that lets us map out the invisible part of the Universe.

As it bends its way towards Earth,

past galaxy after galaxy,

that light traces the contours of a cosmic map of Dark Matter.

For one section of the Universe,

he's rendered the invisible visible.

For the first time, this is the map, in 3-D,

of what the Universe actually looks like --

what the main constituents of the Universe are.

And if some alien were to come to our Universe

and start to look around

and if he could see all of the constituents of our Universe,

this is what he will say it would look like.

It's a cosmic soup of Dark Matter.

Wherever the soup is thickest, that's where galaxies form.

Here we see the same map of Dark Matter,

just seen end-on.

On the left, what we see is actually the positions

of all the galaxies and all the gas in the Universe --

all the ordinary material.

So, wherever there's a giant cluster of galaxies,

there's a large concentration of Dark Matter.

Here we have a large cluster of galaxies,

and here is the corresponding halo around it of Dark Matter.

What we find when we overlay them

is that they're in the same place,

that the ordinary matter

lives inside this dark-matter scaffolding.

And what Richard has done for one corner of the sky,

Carlos Frenk has now done

with a simulation of the whole Universe.

We can see here

the intricate patterns that the Dark Matter forms,

this network of filaments and lumps

that we refer to as the cosmic Web.

It is in these clumps of Dark Matter

that galaxies like the Milky Way would have formed

as these gases cooled and condensed inside them,

eventually producing stars.

The Dark Matter is the skeleton of the Universe.

It is the scaffolding that allows galaxies to form.

The implication is extraordinary.

Dark Matter has allowed everything we know to form.

Without Dark Matter, there would be no galaxies.

Without galaxies, there would be no stars.

Without stars, there would be no planets.

Without planets, there would be no life.

Dark Matter,

an idea that came out of left field 40 years ago,

is now much more than an idea.

It turns out to be crucial to our very existence,

and, slowly, we're closing in on how it works.

We know it doesn't interact with light.

We know it feels the force of gravity.

Then, in 2004, a telescope caught this image,

and we learned something new about Dark Matter.

4 billion light-years away --

that's 1/3 of the way across the known Universe --

two clusters of galaxies are colliding.

It's a strike of incredible power.

Trillions of stars hurtle past one another

at 3,000 miles per second.

One galaxy cluster

is distorted by the shock wave into a bullet shape

and gives the event its name --

the Bullet Cluster Collision.

It's the kind of cosmic spectacle

that delights astronomers.

But even more exciting, it reveals Dark Matter

to be stranger than anyone could possibly have imagined.

The Bullet Cluster is actually

two separate clusters of galaxies,

both of which contain Dark Matter, shown in blue,

and ordinary material, here shown in pink.

And when they smashed into each other,

it was like a giant cosmic car crash.

The ordinary material slowed down.

It started glowing in x-rays, and it slowed down.

It stopped, basically, close to the point of impact.

But the Dark Matter, shown in blue,

kept going after the impact and ended up further away

from the point of collision than the ordinary material.

To understand how this can happen,

we need a crash course in galactic collisions.

So, in this experiment,

we're gonna represent the ordinary material with the cars,

but we're gonna add an extra ingredient --

these particles representing Dark Matter.

And we're gonna see how they behave differently

during a collision.

The ordinary matter behaved just like you'd expect it to --

it stopped.

Dark Matter is fundamentally different.

The Dark Matter doesn't interact in any way,

so it just passed straight through the collision.

It kept on going,

and we now see it further from the point of impact

than the ordinary material, which stopped.

The Bullet Cluster is the best proof that we have

that all this missing material

that astronomers have seen for decades

has very different properties to the ordinary matter.

It's something completely new,

and science knows very little about it.

It doesn't feel ordinary matter. It doesn't even feel itself.

And when the two lumps of dark matter smashed into each other,

they didn't even notice.

They just passed straight through.

Cosmic disasters halfway across the Universe

have proved that Dark Matter is out there

and unlike anything we know --

invisible, intangible, almost like a ghost.

Could we ever devise a way

to see a piece of this elusive substance?

Some scientists believe it may be possible,

but to find it, they're not looking up in the heavens.

They're headed down into the deep, dark bowels of the Earth.

We live in a Universe of matter and light --

matter that makes us and light that sustains us.

But now we know that's only a small fraction of reality.

Our Universe is also teeming

with a mysterious substance we call "Dark Matter."

We can't see it... We can't touch it...

But it's everywhere.

Billions of dark-matter particles

pass through our bodies every second.

Now, if science can somehow

trap one of these particles and study it,

then we might finally understand

what most of the Universe is made of...

And what this really means for us.

In the past century,

physicists have worked out that all matter is built

from about 20 basic subatomic particles.

They go by names

like bosons, electrons, quarks, and neutrinos.

But they also suspect other more exotic particles exist.

There are plenty of theories out there

for what Dark Matter might be.

We're gradually working through the list

and trying to rule them out one by one.

That's the scientific method.

The favorite theory for what Dark Matter is

is a supersymmetric particle -- that is to say

that all the ordinary particles that we know about

have this sort of a mirror image,

that there's this extra set of particles

that is in the dark sector

that don't interact in any way with the ordinary material

except through the force of gravity, which is very weak.

Scientists have another name

for these dark-matter particles --

weakly interacting massive particles,

"wimps" for short.

Wimps hardly ever interact with atoms of normal matter,

so capturing and studying them is really hard.

And since the world is full of particles of regular matter,

it's all too easy to end up snagging them by mistake

and letting the wimps get away.

Dan Bauer has found the perfect place to hunt for wimps --

down an abandoned Minnesota iron mine half a mile underground.

We're now heading down underground

into the Soudan Underground Laboratory.

It'll be about a 3-minute trip down.

This is the same way the miners used to go down before 1960

to do the iron mining.

It's about 2,341 feet underground,

or about half a mile.

It's not the first place you'd think of to do physics,

but, on the other hand, we're down here for a reason.

We're down here to avoid the particles coming from space --

the so-called cosmic-ray particles.

We've arrived at level 27.

You'd think half a mile of bedrock

would be enough of a shield from background noise

to make wimp-hunting a cinch...

But it's not.

The wimp detectors are buried

inside several more feet of solid metal

and heavy plastic shielding.

Throughout the rock of the cavern,

the materials around us, even in us,

there are small amounts of radioactivity.

Those particles, if they got to our detectors,

would be a huge background

such that we would never be able to see wimps.

And this shield

prevents those particles from reaching the detectors

because we're trying to find wimps, not background particles.

Inside the shield

is a stack of 18 hockey-puck-sized crystals

of solid germanium.

They're designed to pick up the faintest of vibrations

if and when a wimp bumps into one of the germanium atoms.

To have a chance of doing that,

they have to be ultrapure and ultracold.

This is our model of a germanium crystal.

These tennis balls represent the germanium atoms in the crystal.

And at room temperature,

what's happening is that all of these atoms are moving

relative to one another.

This is what we know as heat.

What would happen if you tossed a wimp into this crystal?

You wouldn't even notice the difference,

because the crystal is vibrating so much.

However, if I cool this crystal down to very near absolute zero

so that the motion of the atoms stops,

then if I toss our wimp into the crystal,

I see the vibration of the crystal,

and that's the signal we're looking for.

Looking for particles

that hardly ever interact with normal matter

is not a job for the impatient.

There are millions of wimps passing through us every second.

And because they're weakly interacting,

they do exactly that --

they pass right through us and just go on their way.

They pass through the entire Earth and go on their way.

We maybe expect one or two of these

to interact in our detectors per year.

So, incredibly low rate.

To help prevent false positives,

the data is blindly collected in a sealed box

on the hard drive of a computer.

No one on the team is allowed to search it for wimp signals

for an entire year.

And then they look and hope.

In 2007, when we last opened the box and found nothing,

it was certainly a bit disappointing

because we had been running the experiment for a year.

But it had taken us almost seven years to build the experiment,

and so it would have been nice to find something at that point.

But after seven years and tens of millions of dollars,

Dan and his team of wimp catchers

were not about to give up.

And in late 2009,

they opened the box on another entire year's worth of data.

What you see in this region

is where the background radiation would be.

These are events we're not interested in.

We know that they're not wimps.

In this area,

bordered by the magenta and above this green line,

is where we should see wimps.

If any of these are wimp candidates,

then they will turn red when we open the box.

So, let's just click through.

This detector doesn't have any red dots in that area,

so there are no wimp candidates.

Same with this one and this one.

Ah, but look here --

we do have one that appears right here

in the region that we would expect a wimp to appear.

Nothing here. Nothinghere.

Oh! But look right down here.

We have one that just made it into the region

that we think is the wimp region.

Two events, two possible wimp impacts

in one year of 24-hour-a-day detecting.

For the first time, we may have actually trapped

pieces of this elusive Dark Matter.

This could be a giant leap

toward understanding what Dark Matter really is.

But Dan's not 100% sure

that what he has are even wimps at all.

So the search must go on.

It's exciting,

but you have to temper that excitement as a scientist

and realize that you haven't proven it yet.

If we see half a dozen wimps, say, in this next run,

what we will be able to say is, definitively,

there is Dark Matter getting down to this level of Soudan,

which means that Earth is surrounded by Dark Matter

and the Milky Way has Dark Matter.

If a wimp is found, it opens up a whole new range of physics.

If there is this extra

supersymmetric class of particles out of there,

they're doing their own interruptions,

they're doing their own thing, and that really,

since it's the main stuff in the Universe,

that's what's going on in the Universe.

We're just the little bit on the side.

But just as scientists begin to feel

they're getting a handle on Dark Matter,

they discover something very strange.

Dark Matter may be the stuff

that's allowed our galaxy to form,

but it's not the end of the story.

At the dawn of the 21st century,

a space probe found something else hiding in the darkness.

While Dark Matter strives to hold us all together,

this force might be preparing to destroy the entire Universe.

We now know that the visible Universe

is nothing more than a layer of foam

floating on a vast sea of Dark Matter.

Astronomers find themselves adrift on this unfamiliar ocean.

Saul Perlmutter has been navigating these waters

for the past two decades, trying to determine

what Dark Matter might mean for our eventual fate.

As a young student in physics, I very much wanted to measure

something that seemed fundamental,

which is, what's the fate of the Universe?

Will the Universe last forever,

or someday will it come to a halt and collapse?

Saul chose to walk in the footsteps

of the 20th century's most illustrious astronomer,

Edwin Hubble.

Back in the 1920s, Hubble began a meticulous survey

of dozens of galaxies in the night sky.

But he noticed something strange.

Almost all of the galaxies were tinged red.

Just as sound coming from objects moving away from us

gets lower...

...Light gets redder.

Hubble deduced that every galaxy in the Universe

is actually hurtling away from us.

There was only one conclusion -- the Universe must be expanding.

But he couldn't tell how fast.

Why?

Because galaxies that are close and relatively dim

look very similar to those that are far away but very bright,

so he couldn't judge their distance.

Of course, the tricky thing is that you need to know

how bright the actual galaxies are

if you're going to tell how far away they are.

If you're a sailor out at sea

and you're looking at a distant lighthouse through the fog,

you don't know whether it's a very bright lighthouse

and you're very far away

or whether it's a very faint lighthouse

and you're very nearby.

This is the fundamental problem, then,

that astronomers have had to struggle with

through the last centuries.

But there is a solution to this problem.

Astrophysicists have known since the 1980s

about a particular type of star explosion

called a type 1A Supernova.

When a star slightly bigger than our sun

runs out of fuel to burn,

it shrinks down into a dimmer, denser state

known as a white dwarf.

There it hangs in a netherworld between life and death.

But the dwarf still has the potential

to spring back into life if it can find fresh fuel.

When a white dwarf is part of a two-star system,

the neighboring star can provide that fuel.

Once the gravity of the white dwarf

has snagged enough mass from its companion,

there's no turning back.

It explodes.

Its temperature rises to more than a billion degrees,

and most of its gas is blown off into space.

These type 1A Supernovae are just perfect for our purpose

because it's always the same amount of mass

just when it explodes, and so it makes the same brightness

when it reaches its peak.

It brightens in a few weeks, it fades away in a few months,

and if you can catch it

and watch just that little bit of an event,

even billions of years later, when the light arrives at us,

you have a standard star, a standard candle,

to recognize distances with.

Brilliant explosions borne from identical mass,

all giving off exactly the same amount of light.

How much reached us should tell us how far away each was.

In principle, the idea should have worked,

but in practice, there was a problem.

Now, it sounds great,

but they're a real pain in the neck to work with.

You only find a couple of them per millennium

in any given galaxy that you look at,

and you never know when one's gonna go off,

so it's not very easy

to schedule the largest telescopes in the world,

which have to be booked months in advance.

It doesn't make a very good proposal to say,

"I would like the night of march the 3rd

"because sometime in the next 500 years,

a supernova's going to explode."

Then Saul and his team had a flash of inspiration --

take identical wide-angle pictures of the sky

several weeks apart and use an automated program

to search them for the flashes of supernovas.

The idea being that if we could develop

a sophisticated enough computer software,

it could compare those thousands and thousands of galaxies

that we have in those images that we collected

and find the ones that had a new speck of light

that wasn't there three weeks earlier.

And those specks would be the supernova discoveries.

In just over five years,

Saul and his team spot 38 different stars

in 38 different galaxies go supernova.

Their ability to spot these exploding fireballs

becomes legendary,

and when they finally have enough data

to measure what is happening to the Universe,

they produce the biggest shock in astronomy

since the great Hubble himself.

The picture that we all had at the time was,

the Universe is expanding,

that all of the stuff in the Universe

gravitationally attracts all the other stuff in the Universe,

so it should be slowing the expansion.

The question has always been, "how far will that go?

How long will it last? Will it slow to a halt someday?"

What we found when we put the points on the plot

was none of the above -- it wasn't slowing at all.

Apparently, the Universe is, in fact,

speeding up in its expansion.

Saul's team had discovered

a totally unexpected and unexplained

repulsion between galaxies

that is gradually blowing the Universe apart.

They called it...

Dark Energy.

It was startling to think that the Universe

is apparently not mostly the stuff that we're used to seeing

that gravitationally attracts, but may be dominated

by something that we've never studied before.

We call it now "Dark Energy,"

where the "dark" refers to our ignorance,

not to the color of the stuff.

We know very little about it

except that it does want the Universe --

makes the Universe expand faster and faster.

Ignition. Lift-off. We have lift-off.

In the summer of 2001,

a Delta II rocket hurls a small scientific probe into space.

Little does anyone know at the time,

but this probe will tell us

something truly astonishing about Dark Energy.

It is called WMAP,

and its task is to peer further out across space

and further back in time than ever before,

to study the faint echoes of the Big Bang.

David Spergel is a WMAP scientist.

We're really getting a snapshot

of what the Universe looked like very close to The Big Bang,

back in a time when it was very simple.

And we can use that information about the early Universe

to learn a great deal.

We like to think about this

as kind of taking the Universe's baby picture.

For six months,

WMAP probe slowly builds up a mosaic of the baby Universe,

reading the tiny fluctuations

in the temperature of the embers of the Big Bang.

You can think about the early Universe a lot like this lake --

nearly perfectly uniform and smooth.

In the early Universe,

there were tiny variations in density from place to place.

These variations set off sound waves,

a lot like these ripples you see in the lake here.

The way these ripples behave

depends upon the depth of the lake,

the properties of the water.

And these ripples would look a lot different

if I was throwing this in a lake filled with Mercury.

So, by measuring the rate at which the ripples move,

how they spread with time,

I can learn about the properties of the lake.

Works the same way with the early Universe.

By studying the size and shape

of the ripples of the microwave background,

we can infer the composition of the lake, or the early Universe.

Untangling all those ripples

in the echo of the Big Bang

is a monumental task of data analysis.

David and his team crunch piles of numbers

and wrestle with complex equations tirelessly

for an entire year and a half.

But eventually they unravel, with incredible precision,

just what the Universe is made of.

So today, atoms make up about 5% -- 4.6% to be precise.

Dark Matter makes up about 23%.

And what's very strange is,

72% is made up of this Dark Energy.

Put another way, Dark Matter dwarfs us,

but Dark Energy, a mysterious, repulsive force

that scientists do not understand at all,

dwarfs Dark Matter.

It makes up very nearly 3/4 of the Universe.

In the last century, we've come on from thinking

that the entire Universe was within our own Milky Way

to knowing that there are actually

billions of other galaxies out there,

like the Milky Way but separate from us.

We now even know that the Universe is expanding.

They're all moving away from us.

What's more, that expansion is actually accelerating.

The Universe has gone from being

this very familiar, sort of homey place

to being this huge, vast, vast expanse of emptiness.

Dark Energy rules the Universe,

and it appears to be growing stronger day by day.

How long will it be before this mysterious force

rips apart every atom in the cosmos?

Peering into the darkness

is revolutionizing the way we see the cosmos

and ourselves.

Only 5% of the Universe is made of atoms,

the stuff we're made of.

Almost 1/4 of the Universe is Dark Matter,

a substance that allowed galaxies to form.

And 3/4 is Dark Energy,

an inexplicable force that's trying to push everything apart.

How will this struggle end?

Could it eventually tear our Universe to pieces?

Brenna Flaugher plans on solving this puzzle

by measuring just how powerful Dark Energy is.

And this is the device she's going to use.

It's the digital eye of a new telescope

called the Dark Energy camera.

So, we want to understand Dark Energy as best we can.

We need to gather as much information as possible.

This sensor has an incredible 520 megapixels.

Each one, chilled by liquid helium,

is capable of picking up particles of light

that have traveled across the Universe for billions of years.

We're going deeper than other cameras have in the past,

so we're measuring stuff further and further back in time

and also doing it quickly with this big camera.

The Dark Energy camera

will be able to cover huge swaths of the sky

in a single night

and will keep on doing so for five years,

slowly building up more detail in its images,

searching for clues about how Dark Energy has evolved

as our Universe has evolved.

Right now the information that we have about Dark Energy

is that it's getting stronger and stronger

and the Universe is expanding faster and faster.

And we don't know why.

And since we don't know why, we don't know what comes next.

We want to take these deeper surveys

to try to understand that.

The hope is that these surveys

will reveal our Universe's future

by looking back at its 14 billion years of development

in unprecedented detail.

As best as scientists understand it now,

Dark Matter was the dominant force

in determining the form of the Universe

in its first 7 billion years.

It was Dark Matter, after all, that allowed galaxies to form,

attracting regular matter with its invisible mass.

In its second 7 billion years,

Dark Energy grew, overtook Dark Matter,

and now seems to be winning the cosmic contest,

driving galaxies further and further away from one another.

The way that we're going to understand better

what is this Dark Energy

that's accelerating through the Universe today

is to go back in time and look at,

when did Dark Energy first start to become important?

When did we switch from a Universe that was slowing down

to a Universe that's speeding up, and how did that happen?

What was the actual history

of the switch from slowing to speeding?

If you can get a very detailed history

of the expansion of the Universe,

that will differentiate

between these different theories of Dark Energy.

And that's one of the jobs that we're tackling right now.

Where will this mighty battle end...

A truce or a crushing victory for one side?

It all depends on what Dark Energy actually is,

and there are several competing theories.

One of the more ominous calls it "Phantom Energy."

Out of all these many theories of Dark Energy,

one of them is that it's this Phantom Energy, it's called.

And that has this interesting consequence

that as it's accelerating the expansion of the Universe,

making it bigger and bigger,

its acceleration gets faster and faster and faster.

If Dark Energy is this phantom energy,

it's accelerating the expansion of the Universe

so much that the Universe gets bigger and bigger,

more rarified and diluted,

and eventually galaxies will start to get torn apart.

Even after that, solar systems will get pulled apart,

and then stars, and eventually even the constituent

atoms and particles that the Universe is made of

will get ripped apart in what is known as the big rip.

But there is one bright spot

in this dark and threatening picture.

One thing that we know little about, Dark Matter,

may end up being the best tool to study Dark Energy.

Dark Energy is a force

that's trying to push the Universe apart.

Dark Matter is trying to clump things together.

And it's the interplay of these two things

that has led to the formation

of the structures that we see in the Universe today.

And so by understanding

how fast the galaxy clusters form and clump together,

that tells us about Dark Matter but also about how much

Dark Energy was pushing it apart at the same time.

Scientists using something they barely understand

to try to get a handle

on something they don't understand at all.

These are truly strange days in cosmology.

We have come a long way

in a quest to understand the Universe.

I remember 30 years ago,

when the mere concept of Dark Matter

was deemed to be revolutionary.

It was speculative. It was even somewhat heretical.

I would have never dreamt then that 30 years later,

truly alien concepts like Dark Matter and Dark Energy

are actually taken for granted.

Turns out I was right.

There really is something in the shadows.

But I never knew just how important it was.

From the corner of my own bedroom

to the farthest reaches of space,

darkness dominates the Universe...

And controls our fate.

So far, the struggle between Dark Matter and Dark Energy

has been good to us.

After all, without it, there would be

no galaxies, no planets, no you, no me.

But our days may be numbered.

One day...

Darkness could extinguish the light...

Forever.

Until we fully understand these colossal forces,

what ultimately lies in store, heaven only knows.