Nova (1974–…): Season 30, Episode 14 - The Elegant Universe: Welcome to the 11th Dimension (3) - full transcript

Are you wondering how healthy the food you are eating is? Check it -
Now on NOVA,

take a thrill ride into a world
stranger than science fiction,

where you play the game
by breaking some rules,

where a new view of the universe

pushes you beyond the limits
of your wildest imagination.

This is the world
of string theory,

a way of describing every force
and all matter,

from an atom to Earth
to the end of the galaxies,

from the birth of time
to its final tick,

in a single theory...
A theory of everything.

Our guide to this brave
new world is Brian Greene,

the best-selling author
and physicist.

And no matter how many times
I come here,

I never seem to get used to it.

Can he help us solve

the greatest puzzle
of modern physics?

That our understanding
of the universe

is based on two sets of laws
that don't agree.

Resolving that contradiction

eluded even Einstein,
who made it his final quest.

After decades, we may finally be
on the verge of a breakthrough.

The solution is... strings...

Tiny bits of energy vibrating
like the strings on a cello,

a cosmic symphony
at the heart of all reality.

But it comes at a price...

Parallel universes
and 11 dimensions,

most of which you've never seen.

We really may live

in a universe with more
dimensions than meet the eye.

People who've said that there
are extra dimensions of space

have been labeled crackpots
or people who are bananas.

A mirage of science
and mathematics,

or the ultimate
theory of everything?

If string theory
fails to provide

a testable prediction,
then nobody should believe it.

Is that a theory of physics
or a philosophy?

One thing that is certain...

Is that string theory
is already showing us

that the universe
may be a lot stranger

than any of us ever imagined.

Coming up tonight...

the undeniable pull of strings.

The atmosphere

was electric.

String theory goes through

a revolution of its own.

Five different string theories.

And reveals the new shape
of things to come.

Perhaps we live on
a three-dimensional membrane.

Our universe might be like
a slice of bread.

We're trapped

on just a tiny slice of the
higher dimensional universe.

That's actually a problem.

Watch "The Elegant Universe"
right now.

Captioning sponsored by SPRINT,






Corporate funding for NOVA
is provided by Sprint

and Microsoft.

Additional funding
is provided by:

Dedicated to education
and quality television.

Funding for "The Elegant
Universe" is provided by:

To enhance public understanding
of science and technology.

And by the National
Science Foundation,

where discoveries begin.

Additional funding is provided
by Volkswagen

and by:


Major funding for NOVA
is also provided

by the Corporation
for Public Broadcasting

and by contributions
to your PBS stations from:

Imagine that we were able
to control space...

or control time.

The kinds of things that we'd
be able to do would be amazing.

I might be able
to go from here...

to here...

to here...

to here...

and over to here
in only an instant.

Now, we all think that this kind
of trip would be impossible...

And it probably is...
But in the last few years,

our ideas about the true nature
of space and time

have been going through
some changes,

and things that used to seem
like science fiction

are looking not so farfetched.

It's all thanks to a revolution
in physics called string theory,

which is offering
a whole new perspective

on the inner workings
of the universe.

String theory
holds out the promise

that we can really understand

questions of why
the universe is the way it is

at the most fundamental level.

String theory is really
the Wild West of physics.

This is an area
of theoretical physics

which is so radically different

from anything
that's been before.

This radical new theory starts
with a simple premise:

that everything
in the universe...

The Earth, these buildings,

even forces like gravity
and electricity... are made up

of incredibly tiny,
vibrating strands of energy

called strings.

And small as they are,
strings are changing

everything we thought we knew
about the universe...

Especially our ideas
about the nature of space.

To see how, let's first shrink
all of space

to a more manageable size.

Imagine that the whole universe

consisted of nothing more
than my hometown... Manhattan.

So now, just one borough
of New York City

makes up the entire fabric
of space.

And just for kicks,
let's also imagine

that I'm the CEO
of a large corporation

with offices on Wall Street.

Because time is money, I need
to find the quickest route

from my apartment,
here in Upper Manhattan,

to my offices
in Lower Manhattan.

Now, we all know that
the shortest distance

between two points
is a straight line,

but even if there's no traffic...

A bit of a stretch even
in our imaginary Manhattan...

It'll still take us some amount
of time to get there.

By going faster and faster,
we can reduce the travel time.

But because nothing can go
faster than the speed of light,

there's a definite limit

to how much time we can cut
from our journey.

This Manhattan universe

fits with an old,
classical vision of space...

Basically a flat grid
that's static and unchanging.

But when Albert Einstein looked
at the fabric of space,

he saw something
completely different.

He said that space
wasn't static.

It could warp and stretch.

And there could even be unusual
structures of space,

called wormholes.

A wormhole is a bridge
or a tunnel

that can link
distant regions of space...

In effect, a cosmic shortcut.

In this kind of universe,

my commute would be
a New Yorker's dream.

But there's a hitch.

To create a wormhole,

you've got to rip, or tear
a hole in, the fabric of space.

But can the fabric of space
really rip?

Can this first step

toward forming a wormhole
actually happen?

Well, you can't answer these
questions on an empty stomach.

Turns out that by looking
at my breakfast...

Coffee and a doughnut...

We can get a pretty good sense
of what string theory says

about whether the fabric
of space can tear.

Imagine that space
is shaped like this doughnut.

You might think
that it would be very different

from a region of space shaped
like this coffee cup.

But there's a precise sense

in which the shape of the
doughnut and the coffee cup

are actually the same...
Just a little disguised.

You see,
they both have one hole.

In the doughnut
it's in the middle,

and in the coffee cup
it's in the handle.

That means we can change
the doughnut

into the shape of a coffee cup
and back again

without having to rip or tear
the dough at all.

Okay, but suppose you want

to change the shape
of this doughnut

into a very different shape...
A shape with no holes.

The only way to do that is to
tear the doughnut like this...

and then reshape it.

according to Einstein's laws,

this is impossible.

They say that space can stretch
and warp, but it cannot rip.

Wormholes might exist
somewhere fully formed,

but you could not rip space
to create a new one

over Manhattan or anywhere else.

In other words,
I can't take a wormhole to work.

But now, string theory
is giving us

a whole new perspective
on space...

and it's showing us that
Einstein wasn't always right.

To see how, let's take
a much closer look

at the spatial fabric.

If we could shrink down

to about a millionth of a
billionth of our normal size,

we'd enter the world
of quantum mechanics...

the laws that control
how atoms behave.

It's the world of light
and electricity

and everything else
that operates

at the smallest of scales.

Here, the fabric of space
is random and chaotic.

Rips and tears
might be commonplace.

But if they were,

what would stop a rip
in the fabric of space

from creating
a... cosmic catastrophe?

Well, this is where
the power of strings comes in.

Strings calm the chaos.

And as a single string
dances through space,

it sweeps out a tube.

The tube can act like a bubble
that surrounds the tear...

A protective shield
with profound implications.

Strings actually make it
possible for space to rip...

Which means that space is
far more dynamic and changeable

than even Albert Einstein

So does that mean
that wormholes are possible?

Will I ever be able
to take a stroll on Everest?

Grab a baguette... in Paris?

And still make it
back to New York

in time for my morning meeting?

It would be kind of cool,

though it's still
a very distant possibility.

But one thing that is certain...

is that string theory
is already showing us

that the universe
may be a lot stranger

than any of us ever imagined.

For example, string theory says

we're surrounded
by hidden dimensions...

Mysterious places

beyond the familiar three-
dimensional space we know.

People who've said that there
are extra dimensions of space

have been labeled as, you know,

or people who are bananas.

I mean, "What do you think,
there are extra dimensions?"

Well, string theory
really predicts it.

What we think of as our universe

could just be one small part
of something much bigger.

Perhaps we live on a membrane,

a three-dimensional membrane
that floats

inside a higher
dimensional space.

There could be entire worlds

right next to us,
but completely invisible.

These other worlds would,

in a very literal sense,
be... be parallel universes.

This isn't a particularly exotic
or... or strange notion.

No wonder physics students
are lining up

to explore the strange world
of string theory.

String theory is very active.

Things are happening.

There are a lot of people
doing it.

Most of the young kids,
given the choice,

at a ratio of something
like ten to one,

they will go into string theory.

But strings weren't
always this popular.

The pioneers of string theory
struggled for years,

working alone on an idea
that nobody else believed in.

Here's the gist of it:

For decades, physicists believed

that the tiniest bits inside
an atom were point particles.

Flying around the outside
were the electrons,

and inside were protons
and neutrons,

which were made up of quarks.

But string theory says
that what we thought

were indivisible particles

are actually tiny
vibrating strings.

It's nothing really mystical.

It's a really tiny string.

It either closes in
to its little circle

or it has end points,
but it's just a little string.

In the 1980s,
the idea caught on,

and people started jumping
on the string bandwagon.

Well, the fact that suddenly

all these other people
were working in the field

had its advantages
and its disadvantages.

It was wonderful to see

how rapidly the subject
could develop now,

because so many people
were working on it.

One of the great attractions
of strings is their versatility.

Just as the strings on a cello

can vibrate
at different frequencies,

making all the individual
musical notes,

in the same way, the tiny
strings of string theory

vibrate and dance
in different patterns,

creating all the fundamental
particles of nature.

If this view is right,
then put them all together,

and we get the grand
and beautiful symphony

that is our universe.

What's really exciting
about this

is that it offers
an amazing possibility:

If we could only master
the rhythms of strings,

then we'd stand a good chance

of explaining all the matter
and all the forces of nature,

from the tiniest
subatomic particles

to the galaxies of outer space.

This is the potential
of string theory...

To be a unified theory
of everything.

But, at first sight, in our
enthusiasm for this idea,

we seem to have gone too far.

Because we didn't produce
just one string theory...

or even two.

We somehow managed to come up
with five.

Five different string theories,

each competing for the title
of the theory of everything.

And if there's going to be

a "the fundamental theory
of nature,"

there ought to be one of them.

I suppose a number
of string theorists thought,

"Ah, that's fantastic,
that's wonderful,

"and maybe one of these
will end up

being the right theory
of the world."

And yet, there must have been

a little nagging voice
at the back of their head

that said,
"Well, why are there five?

With five competing players,

the stage of string theory
was looking a little crowded.

The five theories had
many things in common...

For example, they all involved
vibrating strings,

but their mathematical details
appeared to be quite different.

Frankly, it was embarrassing.

How could this unified
theory of everything

come in five different flavors?

This was a case where more
was definitely less.

But then, something
remarkable happened.

This is Ed Witten.

He's widely regarded

as one of the world's
greatest living physicists,

perhaps even Einstein's

Ed Witten is a very special
person in the field.

He clearly has a grasp,

particularly of the underlying
mathematical principles,

which is far greater
than most other people.

Well, you know, we all think
we're very smart.

He's so much smarter
than the rest of us.

In 1995, string theorists
from all over the world

gathered at the University
of Southern California

for their annual conference.

Ed Witten showed up
at Strings '95

and rocked their world.

I was really trying
to think of something

that would be significant
for the occasion.

And actually since five
string theories was too many,

I thought I would try to get rid
of some of them.

To solve the problem,
Witten constructed

a spectacular new way of looking
at string theory.

Ed announced that he
had thought about it

and moreover he had solved it.

He was going to tell us
the solution

to every string theory
in every dimension,

which was an enormous claim,

but coming from Ed,
it was not so surprising.

The atmosphere was electric,

because all of a sudden,
string theory

which had been going
through a kind of doldrums,

was given an incredible boost,
a shot in the arm.

Ed Witten gave
his famous lecture.

And he said a couple of words
that got me interested.

And for the rest of the lecture,

I got hooked up on the first
few words that he said

and completely missed the point
of... of his lecture.

I remember I had to give
the talk after him

and I was kind of
embarrassed to.

Ed Witten just blew
everybody away.

Ed Witten blew everybody away
because he provided

a completely new perspective
on string theory.

From this point of view,

we could see that there weren't
really five different theories.

Like reflections
in a wall of mirrors,

what we thought
were five theories

turned out to be just
five different ways

of looking at the same thing.

String theory was unified
at last.

Witten's work sparked
a breakthrough

so revolutionary, that it was
given its own name, "M-theory,"

although no one really knows
what the M stands for.

Ah, what is the M for?





The M-theory.

M-theory is a theory...

I don't actually know
what the M stands for.

Well, the M has...

I've heard many descriptions.

"Mystery theory,"
"magic theory"...

It's the Mother Theory.

"Matrix theory."

"Monstrous theory"?

I don't know...
I don't know what Ed meant.

M stands for magic, mystery
or matrix, according to taste.

I suspect that the M is
an upside-down W for "Witten."

Some cynics have
occasionally suggested

that M may also stand
for "murky,"

because our level
of understanding of the theory

is in fact so primitive.

Maybe I shouldn't have told you
that one!

Whatever the name,
it was a bombshell.

Suddenly everything
was different.

There was a lot of panic,
if you like,

realizing that big things
were happening,

and all of us not wanting
to get left behind

in this new revolution
of string theory.

After Witten's talk,
there was renewed hope

that this one theory
could be the theory

to explain everything
in the universe.

But there was also
a price to pay.

Before M-theory,
strings seemed to operate

in a world with ten dimensions.

These included one dimension
of time,

the three familiar
space dimensions,

as well as six extra dimensions,

curled up so tiny that they're
completely invisible.

Well, we think these
extra dimensions exist

because they come out of
the equations of string theory.

Strings need to move
in more than three dimensions.

And that was a shock
to everybody,

but then we learned
to live with it.

But M-theory would go
even further,

demanding yet another
spatial dimension,

bringing the grand total to...

11 dimensions.

We know that there would
have to be 11 dimensions

for this theory to make sense.

So there must be 11 dimensions.

We only see three
plus one of them.

How is that possible?

For most of us,
it's virtually impossible

to picture the extra,
higher dimensions.

I can't.

And it's not surprising.

Our brains evolved sensing just
the three spatial dimensions

of everyday experience.

So how can we get
a feel for them?

One way is to go to the movies.

We're all familiar
with the real world

having three spatial dimensions.

That is, anywhere I go,

I can move left-right,
back-forth, or up-down.

But in the movies,

things are a bit different.

Even though the characters
on the movie screen

look three-dimensional,

they actually are stuck
in just two dimensions.

There is no back-forth
on a movie screen...

That's just an optical illusion.

To really move in
the back-forth dimension,

I'd have to... step out
of the screen.

And sometimes moving
into a higher dimension

can be a useful thing to do.

So dimensions all have to do

with the independent
directions in which
you can move.

They're sometimes called
degrees of freedom.

The more dimensions
or degrees of freedom
you have,

the more you can do.

That's right.

And if there really
are 11 dimensions,

then strings can do
a lot more, too.

People found fairly soon

that there were objects
that lived in these theories,

which weren't just strings,
but were larger than that.

They actually looked like
membranes or surfaces.

The extra dimension Witten added

allows a string to stretch
into something like a membrane,

or a "brane" for short.

A brane could be
three-dimensional, or even more.

And with enough energy, a brane
could grow to an enormous size,

perhaps even as large
as a universe.

This was a revolution
in string theory.

String theory has gotten
much more baroque.

I mean, now there are not only
strings, there are membranes.

People go on calling this
"string theory,"

but the string theorists
are not sure

it really is a theory
of strings anymore.

The existence of giant membranes
and extra dimensions

would open up a startling
new possibility:

that our whole universe
is living on a membrane,

inside a much larger,
higher dimensional space.

It's almost as if we were living
inside... a loaf of bread.

Our universe might be like
a slice of bread...

Just one slice...

In a much larger loaf

that physicists sometimes call
the "bulk."

And if these ideas are right,

the bulk may have other slices...
Other universes...

That are right next to ours...
In effect, parallel universes.

Not only would our universe
be nothing special,

but we could have
a lot of neighbors.

Some of them could resemble
our universe.

They might have matter
and planets

and, who knows,
maybe even beings of a sort.

Others could certainly be
a lot stranger.

They might be ruled

by completely different
laws of physics.

Now, all these other universes
would exist

within the extra dimensions
of M-theory...

Dimensions that are
all around us.

Some even say they might be
right next to us,

less than a millimeter away.

But if that's true, why can't
I see them or touch them?

If you have a brane living
in a higher-dimensional space,

and your particles, your atoms,
cannot get off the brane,

it's like trying to reach out,
but you can't touch anything.

It might as well be on
the other end of the universe.

It's a very powerful idea,
because if it's right,

it means that our whole picture
of the universe is clouded

by the fact that we're trapped

on just a tiny slice of
the higher-dimensional universe.

It is a powerful idea,

especially because
it may help solve

one of the great mysteries
of modern science.

It has to do with gravity.

It's been more than 300 years
since Isaac Newton came up

with the universal law
of gravity,

inspired, as the story goes,

by seeing an apple fall
from a tree.

Today, it seems obvious that
gravity is a powerful force.

It would seem to most people

that gravity is a very important
force, it's very strong.

It's very hard to get up
in the morning, stand up.

And when things fall,
they break,

because gravity is strong.

The fact of the matter is
that it's not strong.

It's... it's really
a very weak force.

Gravity pulls us down
to the Earth

and keeps our Earth in orbit
around the sun.

But in fact, we overcome the
force of gravity all the time.

It's not that hard.

Even with the gravity
of the entire Earth

pulling this apple downward,

the muscles in my arm
can easily overcome it.

And it's not just our muscles
that put gravity to shame.

Magnets can do it, too...
No sweat.

Magnets carry
a different force...

The electromagnetic force.

That's the same force
behind light and electricity.

It turns out
that electromagnetism is

much, much stronger
than gravity.

Gravity, in comparison,
is amazingly weak.

How weak?

The electromagnetic force is

some thousand billion billion
billion billion times stronger.

That's a one
with 39 zeroes following it.

The weakness of gravity

has confounded scientists
for decades.

But now, with the radical world
of string theory,

filled with membranes
and extra dimensions,

there's a whole new way
to look at the problem.

One way of approaching
the question

of why gravity is so weak
compared to all the other forces

is to turn the question
completely on its head and say,

"No, actually gravity
isn't very weak

"compared to all
the other forces.

It just appears to be weak."

It may be that gravity is

actually just as strong
as electromagnetism,

but for some reason,
we can't feel its strength.

Consider a pool table,
a very large pool table.

Think of the surface
of the pool table

as representing our
three-dimensional universe,

although it is
just two-dimensional,

and think of the billiard balls
as representing atoms

and other particles that
the universe is made out of.

So here's the wild idea.

The atoms and particles

that make up stuff
in the world around us

will stay on
our particular membrane...

Our slice of the universe...

Just as the billiard balls

will stay on the surface
of the pool table...

unless you're
a really bad pool player.

But whenever the balls collide,

there is something that always
seeps off the table.

Sound waves.

That's why I can hear
the collision.

Now, the idea is that gravity
might be like the sound waves...

It might not be confined
to our membrane.

It might be able to seep off
our part of the universe.

Or... think about it
another way.

Instead of pool tables,
let's go back to bread.

Imagine that our universe is
like this slice of toast

and that you and me
and all of matter, light itself,

everything we see,
is like jelly.

Now, jelly can move freely
on the surface of the toast,

but otherwise, it's stuck.

It can't leave
the surface itself.

But what if gravity
were different?

What if gravity were more
like cinnamon and sugar?

Now, this stuff isn't sticky
at all,

so it easily slides
right off the surface.

But why would gravity be so
different from everything else

that we know of in the universe?

Well, turns out that
string theory... or M-theory...

Provides an answer.

It all has to do with shape.

For years, we concentrated
on strings

that were closed loops,
like rubber bands.

But after M-theory, we turned
our attention to other kinds.

Now we think that
everything we see around us,

like matter and light,
is made of open-ended strings,

and the ends of each string
are tied down

to our three-dimensional

But closed loops of string
do exist,

and one kind is responsible
for gravity.

It's called a graviton.

With closed loops, there are
no loose ends to tie down,

so gravitons are free to escape
into the other dimensions,

diluting the strength of gravity

and making it seem weaker than
the other forces of nature.

This suggests
an intriguing possibility.

If we do live on a membrane

and there are parallel universes
on other membranes near us,

we may never see them,

but perhaps we could one day
feel them through gravity.

If there happens
to be intelligent life

on one of the membranes,

then this intelligent life might
be very close to us.

So theoretically,
and purely theoretically,

we might be able to communicate
with this intelligent life

by exchanging strong gravity
wave sources.

So who knows?

Maybe someday we'll develop
the technology

and use gravity waves

to actually communicate
with other worlds.

Yeah, hey, it's Brian.

How you doing?


We don't really know
if parallel universes

could have a real impact on us.

But there is one
very controversial idea

which says they've already
played a major role.

In fact, it gives them credit
for our existence.

As the classic story goes,
the vast universe we see today

was once extremely small...
Unimaginably small.

Then, suddenly, it got bigger...

a lot bigger

during the dramatic event
known as the "big bang."

The big bang stretched
the fabric of space

and set off the chain of events

that brought us to the universe
we know and love today.

But there's always been
a couple of problems

with the big bang theory.

First, when you squeeze
the entire universe

into an infinitesimally small,
but stupendously dense package,

at a certain point, our laws
of physics simply break down.

They just don't
make sense anymore.

The formulas we use start giving
answers that are nonsensical.

We find total disaster.

Everything breaks down,
and we're stuck.

And on top of this,
there's the "bang" itself.

What exactly is that?

That's actually a problem.

The classic form of the big bang
theory really says nothing

about what banged, what happened
before it banged

or what caused it to bang.

Refinements to
the big bang theory do suggest

explanations for the bang,

but none of them turn
the clock back completely

to the moment
when everything started.

Most people come at this

with the naive notion
that there was a beginning,

that somehow
space and time emerged

from nothingness
into somethingness.

Well, I don't know about you,
but I don't like nothing.

Do I really believe

that the universe was
a big bang out of nothing?

And I'm not a philosopher,
so I won't say.

But I could imagine, to a
philosopher, that is a problem.

But to a physicist,
I think it's also a problem.

Everyone admits
there are problems.

The question is,
can string theory solve them?

Some string theorists
have suggested

that the big bang wasn't
the beginning at all,

that the universe could have
existed long before...

Even forever.

Not everyone is comfortable
with the idea.

I actually find it
rather unattractive

to think about a universe
without a beginning.

It seems to me that a universe
without a beginning is

also a universe
without an explanation.

So what is the explanation?

What if string theory is right,
and we're all living

on a giant membrane inside
a higher-dimensional space?

One of the ideas
in string theory

that was particularly
striking to me

and suggested perhaps
a new direction for cosmology

is the idea of branes

and the idea of branes moving
in extra dimensions.

Some scientists have proposed

that the answer
to the big bang riddle

lies in the movements
of these giant branes.

It's so simple.

Here's a brane on which we live,
and here's another brane

floating in
the higher dimension.

There's absolutely
nothing difficult

about imagining that
these collide with each other.

According to this idea,
some time before the big bang,

two branes carrying
parallel universes

began drifting
toward each other...


All of that energy has
to go somewhere.

Where does it go?

It goes into the big bang.

It creates the expansion
that we see,

and it heats up all
the particles in the universe

in this big, fiery mass.

As if this weren't weird enough,

the proponents of this idea make
another radical claim...

The big bang was not
a special event.

They say that parallel universes
could have collided

not just once in the past,
but again... and again...

and that it will happen
in the future.

If this view is right, there's
a brane out there right now

headed on a collision course
with our universe.

So another collision is coming,

and there'll be
another big bang,

and this will just repeat itself

for an indefinite period
into the future.

It's an intriguing idea.

Unfortunately, there are
a few technical problems.

Well, that was
a very ingenious scenario

that arose naturally
within string theory.

However, the good old problems
creep back in again.

The fact is, we don't
really know what happens

when two branes collide.

You can wind up
with the same situation

we had with the big bang.

The equations don't make sense.

They have to make a lot
of assumptions in their models,

and I don't think they've
really solved the problem

of the big bang
in string theory.

If string theory is the one
true theory of the universe,

it will have to solve the riddle
of the big bang.

And there's a lot of hope

that someday string theory
will succeed.

But for now, there's also
a lot of uncertainty.

As promising and exciting
as the theory is,

we don't entirely understand it.

It's as if we've stumbled
in the dark into a house

which we thought was
a two-bedroom apartment

and now we're discovering is
a 19-room mansion, at least...

And maybe it's got
a thousand rooms...

And we're just beginning
our journey.

So how sure are we

that the universe is the way
that string theory describes it?

Is the world really made up
of strings and membranes,

parallel universes
and extra dimensions?

Is this all science
or science fiction?

Well, the question
we often ask ourselves

as we work through
our equations is

is this just fancy mathematics

or is it describing
the real world?

These exercises in our
imagination of mathematics

are all, at the end of the day,
subjected to a single question:

Is it there in the laboratory?

Can you find its evidence?

String theory and string
theorists do have

a real problem.

How do you actually test
string theory?

If you can't test it in the way
that we test normal theories,

it's not science,
it's philosophy.

And that's a real problem.

Strings are thought to be
so tiny...

Much smaller than an atom...

That there's probably no way
to see them directly.

But even if
we never see strings,

we may someday see
their fingerprints.

You see, if strings were around

at the beginning
of the universe,

when things were really tiny,

they would have left impressions
or traces on their surroundings.

And then, after the big bang,
when everything expanded,

those traces would have been
stretched out

along with everything else.

So, if that's true,
we may someday see

the tell-tale signs of strings
somewhere in the stars.

But even here on Earth

there's a chance we can detect
evidence of strings.

This pasture in Illinois serves
as command central

for a lot of this research.

Well, actually, the real work
happens underground,

where the hunt is on

for evidence supporting
string theory,

including extra dimensions.

Not too many years ago,

people who talked about
large extra dimensions

would have been considered
crackpots, to put it lightly.

But all that has changed,
thanks to string theory.

This is Fermilab, and right now
it's our best hope

for proving
that extra dimensions are real.

Fermilab has
a giant atom smasher.

Here's how it works.

Scientists zap hydrogen atoms

with huge amounts
of electricity.

Later, they strip them
of their electrons

and send the protons zooming

around a four-mile, circular
tunnel beneath the prairie.

Just as they're approaching
the speed of light,

they're steered into collisions

with particles whizzing
in the opposite direction.

Most collisions are
just glancing blows

but occasionally
there's a direct hit.

The result is a shower
of unusual subatomic particles.

The hope is that among
these particles will be

a tiny unit of gravity:
the graviton.

Gravitons, according to
string theory, are closed loops,

so they can float off
into the extra dimensions.

The grand prize would be

a snapshot of a graviton
at the moment of escape.

And then the graviton goes
to the extra dimension

and then it shows
in the detector by its absence.

You see it by its absence.

Unfortunately, Fermilab hasn't
yet seen the vanishing graviton.

And the pressure is on,

because another team is
hot on the same trail.

4,000 miles away,

on the border of France
and Switzerland,

a lab called CERN
is constructing

an enormous new atom smasher.

When it's finished,

it will be seven times
more powerful than Fermilab's.

There's a great sense of urgency
that every minute has to count

but eventually CERN,
our rival laboratory,

will frankly blow us
out of the water.

CERN will blow Fermilab
out of the water

not only in the search
for extra dimensions,

but other wild ideas.

At the top of the to-do list
for both labs is

the hunt for something
called supersymmetry.

That's a central prediction
of string theory.

And it says, in a nutshell,

that for every subatomic
particle we're familiar with,

like electrons, photons
and gravitons,

there should also be
a much heavier partner

called a "sparticle,"

which, so far, no one
has ever seen.

Now, because string theory says
sparticles should exist,

finding them is
a major priority.

So, it's a big discovery
to find supersymmetry.

That's... that's
a humongous discovery

and... and I think it's a bigger
discovery to find supersymmetry

than to find life on Mars.

If we were to hear tomorrow that
supersymmetry was discovered,

there would be parties
all over the planet.

The problem is, if they exist,

the sparticles of supersymmetry
are probably incredibly heavy...

So heavy that they
may not be detected

with today's atom smashers.

The new facility at CERN
will have the best chance,

once it's up and running
in several years.

But that won't stop
the folks at Fermilab

from trying to find them first.

The competition is

friendly and fierce
at the same time.

We're competing
like bad dogs, essentially.

It has always been like that
and it will always be like that.

We have to make sure
that we don't make any mistakes,

that we do absolutely the best
we can do at these experiments

and take advantage
of what is really

one of the great golden
opportunities for discovery.

If we do find sparticles,
it won't prove string theory,

but it will be really strong
circumstantial evidence

that we're on the right track.

Over the next ten to 20 years,

the new generation
of atom smashers

is sure to uncover
surprising truths

about the nature
of our universe.

But will it be the universe
predicted by string theory?

What if we don't find sparticles
or extra dimensions?

What if we never find
any evidence

that supports
this weird new universe

filled with membranes
and tiny vibrating strings?

Could string theory,
in the end, be wrong?

Oh, yes, it's certainly
a logical possibility

that we've all been wasting
our time for the last 20 years

and that the theory is
completely wrong.

There have been periods
of many years

where all of the smart people,
all of the cool people

were working on
one kind of theory,

moving in one kind of direction,

and even though
they thought it was wonderful,

it turned out to be a dead end.

This could happen
to string theory.

Even though there's
no real evidence yet,

so much of string theory
just makes so much sense.

A lot of us believe
it's just got to be right.

I don't think it's ever happened

that a theory that has
the kind of mathematical appeal

that string theory has,
turned out to be entirely wrong.

I would find it hard to believe

that that much elegance
and mathematical beauty

would simply be wasted.

I don't really know
how close we are to the end.

You know, are we almost there
in having the complete story?

Is it going to still be
another ten years?

Nobody knows.

Um, but I think it's going to
keep me busy for a long time.

We have been incredibly lucky.

Nature has somehow allowed us

to unlock the keys to many
fundamental mysteries already.

How far can we push that?

We won't know until we...
until we try.

A century ago,
some scientists thought

they had pretty much figured out
the basic laws of the universe,

but then Einstein came along and
dramatically revised our views

of space and time and gravity.

And quantum mechanics unveiled

the inner workings
of atoms and molecules,

revealing a world
that's bizarre and uncertain.

So, far from confirming
that we had sorted it all out,

the 20th century showed

that every time we looked
more closely at the universe,

we discovered yet another
unexpected layer of reality.

As we embark
on the 21st century,

we're getting a glimpse
of what may be the next layer:

vibrating strings, sparticles,
parallel universes

and extra dimensions.

It's a breathtaking vision

and in a few years
experiments may begin to tell us

whether some of these ideas
are right or wrong.

But regardless of the outcome,
we'll keep going,

because, well,
that's what we do.

We follow our curiosity,
we explore the unknown.

And a hundred
or a thousand years from now,

today's view of the cosmos
may look woefully incomplete,

perhaps even quaint.

But undeniably the ideas we call
string theory are a testament

to the power
of human creativity.

They've opened a whole new
spectrum of possible answers

to age-old questions,

and with them,
we've taken a dramatic leap

in our quest to fully understand
this elegant universe.

On NOVA's Web site, go behind
the scenes with Brian Greene,

journey into the subatomic
world, play with strings,

picture other dimensions,
and much more.

To order this program
on VHS or DVD

or the book The Elegant Universe

please call WGBH
Boston Video at

NOVA is a production
of WGBH Boston.

Corporate funding for NOVA
is provided by Sprint

and Microsoft.

Additional funding
is provided by:

Dedicated to education
and quality television.

Funding for "The Elegant
Universe" is provided by:

To enhance public understanding
of science and technology.

And by the National
Science Foundation,

where discoveries begin.

Additional funding is provided
by Volkswagen

and by:


Major funding for NOVA
is also provided

by the Corporation
for Public Broadcasting

and by contributions
to your PBS stations from:

I am PBS.