Nova (1974–…): Season 38, Episode 21 - The Fabric of the Cosmos: What is Space? - full transcript

Simple, obvious, ever-present aspects of our daily lives give scientists fits trying to understand them. One of these aspects is space which physicists are convinced is something more than nothing. This program explains the experi...

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---
Lying just beneath
everyday reality

is a breathtaking world,

where much of what we perceive
about the universe is wrong.

Physicist and best-selling
author Brian Greene takes you

on a journey that bends the
rules of human experience.

BRIAN GREENE:
Why don't we ever see events
unfold in reverse order?

According to the laws
of physics, this can happen.

It's a world
that comes to light

as we probe the most extreme
realms of the cosmos,

from black holes
to the Big Bang

to the very heart
of matter itself.



I'm going to have
what he's having.

Here, our universe may be one
of numerous parallel realities.

The three-dimensional world
may be just an illusion,

and there's no distinction

between past, present
and future.

GREENE:
But how could this be?

How could we be so wrong
about something so familiar?

Does it bother us?

Absolutely.

There's no principle built
into the laws of nature

that say that theoretical
physicists have to be happy.

It's a game-changing
perspective

that opens up a whole new world
of possibilities.

Coming up...



What if you took
all this stuff away?

We're left with empty space.

But what seems like nothing

is actually teeming
with ferocious activity.

What is space?

It is one of the deepest
mysteries in physics.

Could its elusive ingredients
hold the key

to the fate of the universe?

"The Fabric of the Cosmos,"
right now on NOVA.

Major funding for NOVA is
provided by the following:

And...

And by the Corporation
for Public Broadcasting

and by contributions
to your PBS station from:

Major funding
for "The Fabric of the Cosmos"

is provided by
the National Science Foundation.

And...

Supporting original research
and public understanding

of science, technology,
engineering and mathematics.

Additional funding
is provided by...

And the George D. Smith Fund.

BRIAN GREENE:
We think of our world
as filled with stuff,

like buildings and cars...

buses and people.

And nowhere does that seem more
apparent than in a crowded city

like New York.

Yet all around the stuff that
makes up our everyday world...

is something just as important
but far more mysterious,

the space
in which all this stuff exists.

To get a feel for what I'm
talking about,

let's stop for a moment
and imagine.

What if you took
all this stuff away?

I mean all of it:

the people...

the cars and buildings.

And not just the stuff
here on earth,

but the earth itself.

What if you took away all the
planets, stars and galaxies?

And not just the big stuff,

but tiny things down to the very
last atoms of gas and dust.

What if you took it all away?

What would be left?

Most of us would say "nothing."

And we'd be right.

But strangely,
we'd also be wrong.

What's left is empty space.

And as it turns out,
empty space is not nothing.

It's something.

Something with hidden
characteristics as real

as all the stuff
in our everyday lives.

In fact, space is so real
it can bend...

Space can twist...

And it can ripple.

(claps)

So real that empty space
itself helps shape

everything in the world
around us

and forms the very fabric
of the cosmos.

CRAIG HOGAN:
You can't understand anything
about the world

unless you understand space

because that's the world--
the world is space.

With stuff in it.

We're not usually
very conscious of space.

But then again, I tell people,

fish are probably not conscious
of water either.

They're in it all the time.

Space is not really nothing.

It actually has a lot
going on inside.

GREENE:
When most of us picture space,

we think of outer space--
a place that's far, far away.

But space is
actually everywhere.

You could say

it's the most abundant thing
in the universe.

Even the tiniest of things
like atoms,

the basic ingredient in you and
me and everything else we see

in the world around us,

even they are almost
entirely empty space.

In fact, if you removed
all the space

inside all the atoms making up
the stone, glass and steel

of the Empire State Building,

you'd be left
with a little lump...

about the size
of a grain of rice,

but weighing hundreds
of millions of pounds.

The rest is only empty space.

But what exactly is space?

I can show you a picture
of Spain...

of Napoleon...

of my Uncle Harold.

But space looks like this.

Nothing.

So how do you make sense
of something

that looks like nothing?

LEONARD SUSSKIND:
Why is there space

rather than no space?

Why is space three-dimensional?

Why is space big?

We have a lot of room to move
around in.

How come it's not tiny?

Um...

We have no consensus
about these things.

What is space?

We actually still
don't really know.

It is one of the deepest
mysteries in physics.

Fortunately, we're not
completely in the dark.

We've been gathering clues
about space for centuries.

Some of the earliest came

from thinking about how objects
move through space.

To get a feel for this,
take a look at that skater.

As she glides across the rink,

she's moving in relation
to everything around her,

like the ice.

And when she goes into a spin,

not only can she see
that she's spinning,

she can also feel it,

because as she spins, she feels
her arms pulled outward.

But now let's imagine

that you could take away
all the stuff around her,

from the rink...

to the most distant galaxies.

So the only thing left is
the skater

spinning in completely
empty space.

If the skater still feels
her arms pulled outward,

she'll know she's spinning.

But if empty space is nothing,

what is she spinning
in relation to?

Imagine you're that skater.

When you look out,
you don't see anything.

It's just uniform, still
blackness all around you.

And yet, your arms are being
pulled outwards.

So you say to yourself,

what could I be spinning
with respect to?

Is there something out there
that I'm not seeing?

Trying to answer questions
like these,

scientists came up with
a bold new picture of space.

And the key was to make
something out of nothing.

(actors reciting lines
in distance)

When you go to the theater,
you watch the actors...

I do confess that I love nothing
in the world so well as thee.

...the scenery, the story.

I protest I love thee...

Well, then God forgive me!

What offence,
sweet Beatrice?

GREENE:
But there's
something important here

that you won't find mentioned
in the playbill.

Something we hardly ever notice.

The stage.

It's an absolutely vital
part of the show,

and yet most of us, we don't
even give it a second thought.

But Isaac Newton, he did.

This is how the father of modern
science pictured space:

as an empty stage.

To Newton,
space was the framework

for everything that happens
in the cosmos,

the arena within which the drama
of the universe plays out.

And Newton's stage was passive--

absolute, eternal
and unchanging.

The action couldn't affect
the stage

and the stage couldn't affect
the action.

By picturing space in this way,

Newton was able to describe
the world

as no one had ever done before.

His unchanging stage allowed him
to understand

almost all motion
we can see around us,

yielding laws that can
predict everything

from the way apples fall
from trees...

to the path the earth takes
around the sun.

These laws worked so well
that we still use them

for the things we do today,

from launching satellites...

to landing airplanes.

And the laws all hinge on one
radical idea: space is real.

Even though you can't see it
or smell it or touch it,

space is enough of a real,
physical thing

to provide a benchmark
for certain kinds of motion,

like that skater.

Newton would say that when she
spins, her arms splay out

because she is spinning
with respect to something

and that something
is space itself.

(applause)

GATES:
Philosophers had been debating
the nature of space

for a very long time.

What Newton does is change
the terms of the debate,

and with that,

essentially,
modern science gets born.

GREENE:
Newton's stage was a huge hit.

It enjoyed the limelight
for over 200 years.

But in the early decades
of the 20th century,

a new set of ideas emerged

that shook Newton's stage
to its very foundations.

Ideas put forward

by a young clerk working
in a Swiss patent office.

His name?

Albert Einstein.

Einstein grew up
in the late 1 800s,

at the dawn of the age
of electricity.

Electric power was
lighting up cities,

giving rise to all kinds
of technologies

Newton could never
have imagined.

All of these developments tapped
into something

that had captivated Einstein
since he was a child: light.

Not light bulbs
and street lamps,

but the very nature
of light itself.

And it was his fascination

with one particularly weird
feature of light-- its speed--

that would lead Einstein
to overturn

Newton's picture of space.

To see how, let's take a ride.

Right now, we're traveling
at about 20 miles per hour.

To go faster, all the driver
needs to do

is step on the gas
and the cab's speed changes.

Now, you can feel that change,
but you can also see it

on the cab's speedometer or on
one of those radar speed signs.

Okay, you can slow it down now.

(tires squealing)

But now imagine that instead of
measuring the speed of the cab,

you have a radar sign
that measures the speed

of the light
coming off its headlights.

That sign would measure
the light traveling

at an astounding 671 million
miles an hour.

Now, when the cab starts moving,

you'd think that the speed
of the light would increase

by the same amount as the car.

After all, you'd think that the
moving cab would give the light

an extra push.

But surprisingly,
that's not what happens.

Our radar sign-- or any
measurement of light's speed--

will always detect
light traveling

at 671 million miles per hour,

whether the cab
is moving or not.

But how could this be?

How could all measurements
of light's speed

always come out the same?

If you're running at a wall,
it's coming at you faster

than if you're standing still
with respect to that wall.

But that's not true with light.

The speed of light
is the same for everybody.

That's really extraordinary.

GREENE:
So here's how Einstein
made sense

of this extraordinary puzzle.

Knowing that speed is just
a measure of the space

that something travels
over time,

Einstein proposed
a truly stunning idea:

that space and time
could work together,

constantly adjusting
by exactly the right amount

so that no matter how fast
you might be moving

when you measure
the speed of light,

it always comes out to be
671 million miles per hour.

LEVIN:
To respect that absolute quality
about light,

time had to cease
to be absolute.

Space had to cease
to be absolute.

And those two had to become
relative in such a way

that they slosh
between each other.

GREENE:
If space and time being flexible
sounds unfamiliar,

it's only because we don't move
fast enough in everyday life

to see it in action.

But if this cab could move
near the speed of light,

the effects would
no longer be hidden.

For example, if you were
on a street corner

as I went by
close to the speed of light,

you'd see space adjusting,

so that my cab, it would appear
just inches long,

and you'd also hear my watch
ticking off time very slowly.

But from my perspective
inside the cab,

my watch would be ticking
normally

and space in here would appear
as it always does.

But when I look outside the cab,
I'd see space wildly adjusting.

All to keep the speed
of light constant.

So with Einstein,

time and space are no longer
rigid and absolute.

Instead, they meld together
with motion,

forming a single entity that
came to be called "spacetime."

ROCKY KOLB:
I think as we live our life
every day,

we live with a Newtonian picture
of space and time.

It's something that we are
comfortable with.

But Einstein was able to make
reason conquer sense.

That really was
the genius of Einstein.

GATES:
This notion that space and time
are a unity

to me is one
of the greatest insights

that has ever occurred
in science.

It's so counterintuitive

to everything we've ever
experienced as human beings.

GREENE:
And in the hands
of Albert Einstein,

this new picture of space
would solve a deep mystery

having to do with the most
familiar force in the cosmos:

gravity.

Newton knew that gravity is
a force that attracts objects

to each other.

And his laws predicted
the strength of this force

with fantastic precision.

But how does gravity
actually work?

How does the earth pull
on the moon

across hundreds of thousands
of miles of empty space?

They behave
as if they are connected

by some kind of invisible rope.

But everyone knew
that wasn't true.

And Newton's laws provided
no explanation.

FILIPPENKO:
Einstein found

that no band-aid patches would
fix Newtonian gravity.

He had to invent a mechanism
for it, he had to understand it.

GREENE:
After puzzling over this problem
for more than ten years,

Einstein reached
a startling conclusion:

the secret to gravity lay
in the nature of spacetime.

It was even more flexible
than he had previously realized.

It could stretch,
like an actual fabric.

This was a truly radical break
from Newton.

Think of this table
as spacetime,

and think of these balls
as objects in space.

Now, if spacetime
were nice and flat

like the surface
of this table,

objects would travel
in straight lines.

But if space is like a fabric
that can stretch and bend?

Well, this may seem
a little strange.

But watch what happens
if I put something heavy

on the stretchy
spacetime fabric.

Now if I take my shot again...

The ball travels along an
indentation in the fabric

that the heavier object creates.

And this, Einstein realized,
is how gravity actually works.

It's the warping of spacetime
caused by the objects within it.

In other words, gravity is
the shape of spacetime itself.

The moon is kept in orbit not
because it's pulled to the earth

by some mysterious force,

but rather because it rolls
along a curve

in the spacetime fabric
that the earth creates.

SUSSKIND:
With Einstein, space became
not only real, but flexible.

So suddenly space had
properties.

Suddenly space had curvature.

Suddenly space had a flexible
kind of geometry

almost like a rubber sheet.

GATES:
It opens up a whole new way
of thinking about reality

that describes
the entire universe.

Einstein becomes "Einstein"
because of that observation.

Where Newton saw space
as passive,

Einstein saw it as dynamic.

It's interwoven with time and
it dictates how things move.

So after Einstein,

space can no longer be thought
of as a static stage.

It's an actor,

and it plays a leading role
in the cosmic drama.

Now, it's one thing
to think of space

as dynamic, active and flexible
like a fabric.

But is it really?

Is this just a metaphor?

Or does it actually describe
what space is?

Well, Einstein's theory predicts
that one way to find out

would be to take
a little journey

to the edge of a black hole.

Black holes are collapsed stars,

massive objects crushed to a
fraction of their original size.

Gravity around them
is so strong

that according to Einstein's
math, a spinning black hole

can literally drag space
along with it,

twisting it like
an actual piece of cloth.

The nearest black hole
is trillions of miles away,

making it a challenge
to test this prediction.

But in the late 1 950s,
a physicist named Leonard Schiff

began searching for a way

to test Einstein's ideas about
space much closer to home.

Schiff was inspired by something
we usually think of

as a child's toy: a gyroscope.

He thought that if space
really twists like a fabric,

a gyroscope might allow him
to detect it.

It was a strange idea,

and he chose a strange place
to share it with the world...

the faculty swimming pool
at Stanford.

Here, in 1 959, Schiff met

with two colleagues, William
Fairbank and Bob Cannon.

He was excited about an ad he'd
seen for a high-tech gyroscope.

Though it looked different,

it basically worked the same
as the child's toy.

Then and there,

the three decided to launch
a device like this into orbit

around the earth.

Normally, a gyroscope's axis
points in a fixed direction.

But if Earth is actually
dragging space,

then the gyroscope's axis would
be dragged along with it,

shifting its orientation
in a way that could be measured.

It was a brilliantly
simple plan.

There was just one problem.

Einstein's theories predict

that the earth's rotation twists
space by only a tiny amount--

an amount so small, it would be
like trying to measure

the height of a penny
from 62 miles away.

The team spent more than two
years trying to figure out

how to make
such a precise measurement.

They finally devised a plan
to attach

four freely floating gyroscopes
to a telescope

aimed at a distant star.

If space twists, then over time,

the gyroscopes would no longer
point at the star,

since they'd get caught up
in the swirl of space.

And in 1 962, they applied
to NASA for a grant,

requesting around
a million dollars

for what would come to be
called Gravity Probe B.

Members of the team
originally thought

the project would take
about three years.

They were just
a little optimistic.

With an ever-growing team,
Gravity Probe B became

one of the longest-running
experiments in history.

Decade after decade was spent

trying to realize
the original vision,

which meant launching
a telescope into space

and building gyroscopes

that were among the smoothest
objects ever created.

BRAD PARKINSON:
The technology is just
frightening.

It was like the carrot
on the front of the mule.

It was like it was always
five to ten years away

when we could do this,

and it was five to ten years
away for about 35 years.

GREENE:
Consuming more than four decades
and $750 million,

the project was nearly cancelled
by NASA nine times.

MISSION CONTROLLER:
Ten, nine, eight...

GREENE:
Finally, in April of 2004,

the team gathered
to witness the launch.

MISSION CONTROLLER:
And liftoff!

(applause and whistling)

GREENE:
Of the three men who sat
by the pool back in 1 959,

only one was alive to see it.

ROBERT CANNON:
There we were, watching.

It's a terribly exciting moment
in your life.

Just a thrilling experience.

It was flawless.

Ten thousand things
did not go wrong.

GREENE:
For over a year, Gravity Probe B
orbited the earth

while the team nervously
monitored its every move,

trying to see if the earth
would actually twist space.

Finally, the data began
to trickle in.

And there was a problem.

The gyroscopes were experiencing
a tiny, unexpected wobble,

and to clean up the data
would cost millions.

With funds running out,

it looked like nearly half
a century of work

was about to go
down the drain.

Then, at almost the last
possible moment,

two sources of additional
funding emerged:

the son of original team leader
William Fairbank,

who made a private donation;

and Turki al-Saud, a member
of the Saudi royal family

with a degree in aeronautics
from Stanford,

who arranged for a large grant.

Over the next two years,

the problem with the data
was solved,

revealing that the axes
of the gyroscopes shifted

by almost exactly
the amount predicted

by Einstein's equations.

PARKINSON:
I think it's the first time

that you can actually see
Einstein's effect, his drift,

with the naked eye.

GREENE:
This experiment provides the
most direct evidence ever found

that space is something real,
a physical entity like a fabric.

After all,
if space were nothing,

there would be nothing to twist.

But at the same time that Albert
Einstein was investigating space

on the largest of scales,

another band of physicists
was probing the universe

on extremely tiny scales.

And there they found
a completely uncharted realm

where Einstein's picture
of space,

it was nowhere to be found.

To see what I'm talking about,

imagine you could shrink
billions of times smaller

than your current size.

This is the realm of atoms
and subatomic particles,

the fundamental building blocks
of everything we can see.

And when you get down
to this size,

the world plays by a wildly
different set of rules

called quantum mechanics.

According to these rules,
even if you try to remove

every last atom and particle,

you'd find that empty space
is still far from empty.

In fact, it's teeming
with activity.

Particles are constantly popping
in and out of existence.

They erupt out of nothingness,

quickly annihilate each other
and disappear.

In quantum mechanics, empty
space is not that empty.

It's full of fluctuating fields,

full of all sorts
of jittery things going on.

It's a place where particles

are constantly fluctuating
and annihilating each other

and being created again
and annihilating.

It's a place of chaos
and bubbling.

GREENE:
While the theory predicted this,
it wasn't until 1 948

that a scientist named
Hendrik Casimir suggested

that even though we can't see
these particles,

they should cause empty space
to do something we can see.

And he predicted

that if you take two ordinary
metal plates...

and place them
extremely close together--

say, closer together than the
thickness of a sheet of paper--

then particles with certain
energies would be excluded

because in some sense, they
wouldn't fit between the plates.

With more
of this frenetic activity

outside the plates than inside,

Casimir thought the plates
would be pushed together

by what we usually think of
as empty space.

And some years later,
when the experiment was done...

Casimir was proven right.

In empty space, the plates
were pushed together.

So on atomic scales,
empty space is not empty.

It's so flooded with activity

that it can force objects
to move.

And today,

the quest to understand space on
the smallest scale is continuing

with one of the most expensive
science experiments in history.

This is CERN,

the European Organization
for Nuclear Research in Geneva.

And here, buried a few hundred
feet below the ground,

is the Large Hadron Collider,

the world's most powerful
accelerator.

With a price tag
of about $1 0 billion,

it accelerates
subatomic particles

to more than 99.99%
of the speed of light

and smashes them
into each other.

In the showers of debris
produced by these collisions,

scientists at places like this
have discovered a whole zoo

of strange and exotic particles.

And right now, they are chasing
one of the most elusive,

a particle thought to be
essential to shaping everything

from the atoms in our bodies
to the most distant stars.

If this particle is found,

it will redefine
our picture of space

and fulfill a quest begun
more than 40 years ago.

It all started in 1 964,

when a young English physicist
named Peter Higgs

suggested something about space
that was so radical,

it nearly ruined him.

HIGGS:
I was told that I was talking
nonsense,

that I couldn't be right.

So they clearly hadn't
understood what I was saying.

GREENE:
Higgs and a few others

were wrestling with a puzzle
which comes down to this:

The fundamental particles
in the universe

all contain different amounts
of mass,

which we usually
think of as weight.

Without mass, these particles
would never combine

to form the familiar atoms
that make up all the stuff

we see in the world around us.

But what creates mass?

And why do different particles
have different masses?

Try as they might,

no one had been able to answer
this perplexing question.

Then, one weekend,

after a walk outside Edinburgh,
Higgs had a peculiar idea.

Using mathematics, he imagined
space in a new way,

as something like an ocean.

Particles are immersed
in this ocean

and gain mass
as they move through it.

To see how this works,

think of a particle's mass
like an actor's fame,

and the Higgs ocean
is like the paparazzi.

Some particles, like unknown
actors, pass through with ease.

The paparazzi simply aren't
interested in them.

But other particles,
like superstars,

have to push and press.

And the more those particles
struggle to get through,

the more they interact
with the ocean,

and the more mass they gain.

Higgs was convinced he'd made
a great discovery.

But when he submitted his idea
to a journal at CERN,

it was rejected.

Undaunted, Higgs honed
his theory further

until he was offered
the chance to present it

at Einstein's old haunt:

the Institute for Advanced Study
in Princeton.

There, he expected his new idea

would meet some of its
toughest critics.

HIGGS:
I was happily driving
up the freeway,

and then there was a sign
to turn off for Princeton,

and that really confronted me
with what I was going into.

I broke out in a cold sweat
and started trembling,

and I had to pull off the road
to recover.

GREENE:
But Higgs persevered.

It was the first
in a series of talks

that would convince colleagues
far and wide

that he was
onto something profound.

HIGGS:
Eventually I sort of
wore them down.

I felt I had sort of triumphed.

(laughing)

So I enjoyed the parties
which followed.

GREENE:
Today, the idea Higgs pioneered,
called the Higgs field,

is crucial to our understanding
of space.

LYKKEN:
The Higgs field is everywhere.

It's something that, even in
the emptiest vacuum of space,

has an effect:
it gives you mass.

So I think Higgs actually
deserves credit

for being one of the people
that said space is stuff,

it has properties in it
that are intrinsic,

that you can't get rid of,
you can't turn them off.

GREENE:
The only problem?

There's no physical proof
that the Higgs field exists,

at least not yet.

But here at CERN,

scientists are attempting
to smash particles together

with so much energy

that they will knock loose
a piece of the Higgs field...

producing a tiny particle
of its own.

It's as if they're trying
to chip off a piece of space.

We think that if we knock
into space hard enough

with particle accelerator
collisions,

that we can actually
make a Higgs particle

come out of empty space.

Our whole understanding
of matter as we now have it

would just fall apart if
the Higgs field didn't exist.

I don't think anybody seriously
doubts that we will see it.

Certainly if we don't, that will
be an extremely bizarre outcome.

GREENE:
Finding the Higgs particle
would be a major milestone,

establishing that the emptiest
of empty space

has an impact on all of matter.

But it turns out that space
contains an ingredient

far more elusive than anything
Higgs ever imagined,

an ingredient that may hold
the key

to the greatest
of all mysteries,

the very fate of the cosmos.

It's a mystery that began
some 1 4 billion years ago

in what we call the Big Bang.

In a fraction of a second,

the universe underwent
a violent expansion,

sending space hurtling outward.

Space has been expanding
ever since.

For decades, most scientists
thought that expansion

must be slowing down
thanks to the pull of gravity.

FILIPPENKO:
When I toss an apple up,

the gravity of the earth
eventually stops it

and brings it back.

And just like the apple
slows down with time,

so too the universe
should have been slowing down

in its expansion because of
the gravitational attraction

of all matter and energy
for all other matter and energy.

GREENE:
But that raised the question:

what is the ultimate fate
of the cosmos?

Would space go on
expanding forever,

or would gravity eventually stop
space from expanding,

causing it to collapse back
on itself in a "big crunch"?

To solve this mystery,
two teams of astronomers

set out to measure
the slowing of the expansion

using a novel tool,

exploding stars
called supernovas.

ADAM RIESS:
So a supernova is a star

that ends its life
in a massive explosion.

They're extremely luminous.

They can be as bright
as a billion suns.

SAUL PERLMUTTER:
What makes supernova great

is that they are very similar
when they explode.

They all get to
about the same brightness

and then they fade away
in just about the same way.

GREENE:
Because the explosions
are so bright and uniform,

the teams reasoned
that these supernovas

would act as very precise
cosmic beacons,

allowing them to track
how the expansion of space

has slowed over time.

The trouble is, supernovas
are extremely rare.

To find enough of them,

Perlmutter spent years calling
astronomers around the globe,

begging for time
on their telescopes.

PERLMUTTER:
We needed the biggest telescopes
in the world.

We needed perfect conditions.

And in those perfect conditions,

I would be calling people up
at the middle of their night

when they're trying to do
some serious work,

and I'd be saying,

"I know that you have
a very busy schedule,

"but by any chance,

"if you could just squeeze in
this half-hour observation,

it would really be
very interesting to us."

GREENE:
When they finally
had enough data

to chart how much
the pull of gravity

was slowing the expansion
of the universe,

they were in for a surprise.

PERLMUTTER:
The results looked
a little bit strange.

They didn't really show any
slowing of the universe at all.

Very surprising.

Actually, a universe
that's actually speeding up.

It was as though space, which we
really thought was nothing,

actually had an inherent
springiness to it.

And so space did not want
to be compressed;

space actually wants to push
the universe apart.

It looked like the universe

was expanding faster and faster
with time,

accelerating
rather than decelerating.

My immediate response was,

"I have to figure out
why this is wrong.

This can't be right."

GREENE:
But it was right.

And most scientists converged
on one explanation:

There's something
that fills space

and counteracts the pull
of ordinary attractive gravity,

pushing galaxies apart

and stretching the very fabric
of the cosmos.

This mysterious substance
filling space

has been dubbed "dark energy,"

and it's turned our picture
of the universe upside down.

FILIPPENKO:
Over the largest distances,

dark energy dominates
the contents of the universe,

and we don't know what it is.

GATES:
If you do sort of a survey,

a census of all the energy
in the universe,

dark energy turns out to be
about 70% of the universe.

And up until a decade ago,

nobody imagined
such stuff even existed.

GREENE:
So in essence,
the weight of empty space itself

is 70% of the weight
of the entire universe.

That's roughly the same
percentage of Earth's surface

that's covered by water.

Imagine we didn't know
what water is.

That's where we stand
with dark energy.

LYKKEN:
We're really clueless
about how to explain it.

We have all of this fancy
scientific apparatus

of quantum mechanics and
relativity and particle physics

that we've developed
in the last hundred years,

and none of that works
to explain dark energy.

GREENE:
And the discovery of dark energy
held another surprise:

The idea that the universe
contains such an "ingredient"

had actually been "cooked up"
80 years earlier.

GREENE:
I'll let you in
on a little secret.

Although he didn't call it
dark energy,

long ago, Albert Einstein
predicted that space itself

could exert a force that would
drive galaxies apart.

You see,

shortly after discovering his
general theory of relativity,

his theory of gravity,

Einstein found that,
according to the mathematics,

the universe would either
be expanding or contracting.

But it couldn't hover
at a fixed size.

This was puzzling because before
they knew about the Big Bang,

most scientists,
including Einstein,

pictured the universe as static:
eternal and unchanging.

When Einstein's equations

suggested an expanding
or contracting universe--

not the static universe
everyone believed in--

he had a problem.

So Einstein went back
to his equations

and modified them to allow
for a kind of anti-gravity

that would infuse space
with an outward push,

counteracting the usual inward
pull of gravity,

allowing the universe
to stand still.

He called the modification
the cosmological constant.

Adding the cosmological constant
rescued his equations.

But the truth is, Einstein had
no idea if this outward push,

or anti-gravity, really existed.

KOLB:
The introduction of the
cosmological constant

by Einstein was not
a very elegant solution

to try to find
what he was looking for:

a stationary universe.

It achieves this effect
of anti-gravity.

It says that gravity sometimes
can behave in such a way

as not to pull things together
but to push things apart.

Like the clash of two titans,

the cosmological constant and
the pull of ordinary matter

could hold the universe in check
and keep it static.

GREENE:
But about a dozen years later,
the astronomer Edwin Hubble

discovered the universe
is not static.

It's expanding due to the
explosive force of the Big Bang

1 4 billion years ago.

That meant Einstein's
original equations

no longer had to be altered.

And so suddenly, the need
for a cosmological constant

went right out the window.

Thank you.

You're welcome.

Einstein is said to have called
this his biggest blunder.

But here's the thing.

With the recent discovery

that the expansion
of the universe is accelerating,

scientists are convinced that
there is something in space

that is pushing things apart.

So 70 years later,
Einstein's biggest blunder

may rank among
his greatest insights.

LYKKEN:
It was something that nobody
else was thinking about.

But it might be that Einstein's
cosmological constant is the key

to understanding the expansion
of the universe

as we see it today.

GREENE:
Though no one knows
what dark energy actually is,

it raises an astounding
and troubling possibility.

Einstein pictured the strength
of his anti-gravity as constant,

but is the strength
of dark energy constant?

And what if it changes
over time?

The answer could overturn
everything we thought we knew

about the fate of the cosmos.

At the moment,
everything in our world,

from the molecules
making up my body

to the molecules
making up the moon,

is held together by forces

that overwhelm the outward push
of dark energy.

And that's why we don't
see things expanding

in our everyday lives.

But that situation
might not last forever.

In one scenario,

dark energy will continue
to push the galaxies

farther and farther apart,
until ultimately,

they'd be pushed so far apart

that the universe would become
a cold, dark and lonely place.

In another scenario,

the strength of dark energy
might increase over time,

becoming so strong that it
would tear apart everything

within the galaxies,

from stars, to planets,
to matter of all kind.

FILIPPENKO:
If the dark energy
grows with time,

then ultimately even atoms
will get ripped apart

when there's enough dark energy
between the nuclei

and the electrons
to rip space apart.

The Big Rip.

GREENE:
Our picture of space

has gone through
a remarkable transformation.

Back in Newton's time,
space was just the container.

It didn't do anything at all.

Then through Einstein,

space begins to affect
how objects move.

Then with Casimir,
literally objects can be pushed

by the activity
even in empty space.

And now, through the ideas
of Higgs and dark energy,

the very expansion
of the universe may be coming

from the energy
of empty space itself.

I don't think anybody
would have thought

that space would have this kind
of rich and profound impact

on the nature of reality.

But as far as we've come,

the journey that began with
Isaac Newton's picture of space

as something like a stage
is not yet finished.

As we examine the fabric
of the cosmos ever more closely,

we may well find
far more surprises

than anyone ever imagined.

Take me, for example.

I seem real enough, don't I?

Well, yes.

But surprising new clues
are emerging that everything--

you and I
and even space itself--

may actually be...

a kind of hologram.

That is, everything we see
and experience,

everything we call our familiar
three-dimensional reality,

may be a projection
of information that's stored

on a thin, distant,
two-dimensional surface,

sort of the way the information
for this hologram

is stored on this thin
piece of plastic.

Now, holograms are something
we're all familiar with

from the security symbol
you find on most credit cards.

But the universe as a hologram?

That's one of the most
drastic revisions

to our picture of space,
and reality, ever proposed.

And the evidence for it

comes from some of the strangest
realms of space: black holes.

SUSSKIND:
This is a real disconnect

and it's very hard
to get your head around.

Modern ideas coming
from black holes

tell us that reality
is two-dimensional,

that the
three-dimensional world,

the full-bodied,
three-dimensional world

is a kind of image of a hologram

on the boundary
of the region of space.

This is a very strange thing.

When I was a younger physicist,
I would have thought

any physicist who said that
was absolutely crazy.

GREENE:
Here's a way to think
about this.

Imagine I took my wallet and
threw it into a black hole.

What would happen?

We used to think that since
nothing, not even light,

can escape the immense gravity
of a black hole,

my wallet would be lost forever,

but it now seems that may not be
the whole story.

Recently, scientists exploring
the math describing black holes

made a curious discovery.

Even as my wallet disappears
into the black hole,

a copy of all the information
it contains

seems to get smeared out
and stored on the surface

of the black hole
in much the same way

that information is stored
in a computer.

So in the end, my wallet exists
in two places:

there's a three-dimensional
version that's lost forever

inside the black hole,
and a two-dimensional version

that remains on the surface
as information.

CLIFFORD JOHNSON:
The information content
of all the stuff

that fell into that black hole
can be expressed

entirely in terms of just
the outside of the black hole.

The idea then is
that you can capture

what's going on
inside the black hole

by referring
only to the outside.

GREENE:
And in theory,
I could use the information

on the outside of the black hole
to reconstruct my wallet.

And here's the truly
mind-blowing part:

Space within a black hole
plays by the same rules

as space outside a black hole
or anywhere else.

So if an object
inside a black hole

can be described by information
on the black hole's surface,

then it might be that everything
in the universe--

from galaxies and stars to you
and me, even space itself--

is just a projection
of information stored

on some distant, two-dimensional
surface that surrounds us.

In other words, what we
experience as reality

may be something
like a hologram.

Is the three-dimensional
world an illusion

in the same sense that
a hologram is an illusion?

Perhaps.

I think I'm inclined
to think, "Yes,"

that the three-dimensional world
is a kind of illusion

and that the ultimate
precise reality

is the two-dimensional reality
at the surface of the universe.

This idea is so new that
physicists are still struggling

to understand it.

But if it's right,
just as Newton and Einstein

completely changed
our picture of space,

we may be on the verge of an
even more dramatic revolution.

For something that's
such a vital part

of our everyday lives,

space remains kind of like
a familiar stranger.

It's all around us,

but we're still far from having
unmasked its true identity.

That may take a hundred years,
it may take a thousand years,

or it may happen tomorrow.

But when we solve that mystery,

we'll take a giant step
toward fully understanding

the fabric of the cosmos.

Major funding for NOVA
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And by the Corporation
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Major funding
for "The Fabric of the Cosmos"

is provided by
the National Science Foundation.

And...

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and public understanding

of science, technology,
engineering and mathematics.

Additional funding
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