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 bestselling 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 have said that

There were 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...

It all started with an apple.

The triumph of Newton』s equations

Come from the quest to understand the planets and the stars.

And we've come a long way since.

Einstein gave the world a new picture for

What the force of gravity actually is.

Where he left off,

String theorists now dare to go.

But how close are they to fulfilling Einstein』s dream?

Watch the elegant universe right now.

Fifty years ago,

This house was the scene

Of one of the greatest mysteries of modern science,

A mystery so profound that today

Thousands of scientists on the cutting edge of physics

Are still trying to solve it.

Albert Einstein spent his last two decades

In this modest home in Princeton, new jersey.

And in his second floor study

Einstein relentlessly sought a single theory so powerful

It would describe all the workings of the universe.

Even as he neared the end of his life

Einstein kept a notepad close at hand,

Furiously trying to come up with the equations

For what would come to be known

As the "theory of everything."

Convinced he was on the verge of the most important discovery

In the history of science,

Einstein ran out of time, his dream unfulfilled.

Now, almost a half century later,

Einstein』s goal of unification—

Combining all the laws of the universe in one,

All-encompassing theory—

Has become the holy grail of modern physics.

And we think we may at last achieve Einstein』s dream

With a new and radical set of ideas called "string theory."

But if this revolutionary theory is right,

We're in for quite a shock.

String theory says we may be living in a universe

Where reality meets science fiction—

A universe of eleven dimensions

With parallel universes right next door—

An elegant universe composed entirely of the music of strings.

But for all its ambition,

The basic idea of string theory is surprisingly simple.

It says that everything in the universe,

From the tiniest particle to the most distant star

Is made from one kind of ingredient—

Unimaginably small vibrating strands of energy called strings.

Just as the strings of a cello

Can give rise to a rich variety of musical notes,

The tiny strings in string theory

Vibrate in a multitude of different ways

Making up all the constituents of nature.

In other words,

The universe is like a grand cosmic symphony

Resonating with all the various notes

These tiny vibrating strands of energy can play.

String theory is still in its infancy,

But it's already revealing

A radically new picture of the universe,

One that is both strange and beautiful.

But what makes us think we can understand

All the complexity of the universe,

Let alone reduce it to a single "theory of everything?"

We have r mu nu,

Minus a half g mu nu r—

You remember how this goes—

Equals eight pi g t mu nu...

Comes from varying the Einstein Hilbert action,

And we get the field equations and this term.

You remember what this is called?

No that's the scalar curvature.

This is the Ricci tensor.

Have you been studying this at all?

No matter how hard you try,

You can't teach physics to a dog.

Their brains just aren't wired to grasp it.

But what about us?

How do we know that we're wired to

Comprehend the deepest laws of the universe?

Well, physicists today are confident that we are,

And we're picking up where Einstein left off

In his quest for unification.

Unification would be

The formulation of a law that describes,

Perhaps, everything in the known universe from

One single idea, one master equation.

And we think that there might be this master equation,

Because throughout the course of the last 200 years or so,

Our understanding of the universe

Has given us a variety of explanations that are all pointing

Towards one spot.

They seem to all be converging

On one nugget of an idea that we're still trying to find.

Unification is where it's at.

Unification is what we're trying to accomplish.

The whole aim of fundamental physics

Is to see more and more of the world's phenomena

In terms of fewer and fewer

And simpler and simpler principles.

We feel, as physicists,

That if we can explain

A wide number of phenomena

In a very simple manner,

That that's somehow progress.

There is almost an emotional aspect

To the way in which the great theories in physics.

Sort of encompass

A wide variety of apparently different physical phenomena

So this idea that

We should be aiming to unify our understanding is inherent,

Essentially,

To the whole way in which this kind of science progresses.

And long before Einstein,

The quest for unification

Began with the most famous accident

In the history of science.

As the story goes,

One day in 1665,

A young man was sitting under a tree when,

All of a sudden,

He saw an apple fall from above.

And with the fall of that apple,

Newton revolutionized our picture of the universe

In an audacious proposal for his time,

Newton proclaimed that the force pulling apples to the ground

And the force keeping the moon in orbit around the earth

Were actually one and the same.

In one fell swoop,

Newton unified the heavens and the earth

In a single theory he called gravity.

The unification of the celestial with the terrestrial—

That the same laws that govern the planets in their motions

Govern the tides and the falling of fruit

Here on earth

It was a fantastic unification of our picture of nature.

Gravity was the first force to be understood scientifically,

Though three more would eventually follow.

And, although Newton discovered his law of gravity

More than 300 years ago,

His equations describing this force

Make such accurate predictions that

We still make use of them today.

In fact

Scientists needed nothing more than Newton』s equations

To plot the course of a rocket that landed men on the moon.

Yet there was a problem.

While his laws

Described the strength of gravity with great accuracy,

Newton was harboring an embarrassing secret

He had no idea how gravity actually works.

For nearly 250 years,

Scientists were content to look the other way

When confronted with this mystery.

But in the early 1900s,

An unknown clerk working in the Swiss patent office

Would change all that.

While reviewing patent applications,

Albert Einstein was also pondering the behavior of light.

And little did Einstein know

That his musings on light

Would lead him to solve Newton』s mystery

Of what gravity is.

At the age of 26,

Einstein made a startling discovery

That the velocity of light is a kind of cosmic speed limit,

A speed that nothing in the universe can exceed.

But no sooner had the young Einstein published this idea

Than he found himself squaring off

With the father of gravity.

The trouble was,

The idea that nothing can go faster than the speed of light

Flew in the face of Newton』s picture of gravity.

To understand this conflict,

We have to run a few experiments.

And to begin with,

Let's create a cosmic catastrophe.

Imagine that all of a sudden,

And without any warning,

The sun vaporizes and completely disappears.

Now, let's replay that catastrophe

And see what effect it would have on the planets

According to Newton.

Newton's theory predicts that with the destruction of the sun

The planets would immediately fly out of their orbits

Careening off into space.

In other words,

Newton thought that gravity

Was a force that acts instantaneously across any distance.

And so we would immediately feel

The effect of the sun's destruction.

But Einstein saw a big problem with Newton』s theory,

A problem that arose from his work with light.

Einstein knew light doesn't travel instantaneously.

In fact,

It takes eight minutes for the sun's rays

To travel the 93 million miles to the earth.

And since he had shown that nothing,

Not even gravity, can travel faster than light,

How could the earth be released from orbit

Before the darkness resulting from

The sun's disappearance reached our eyes?

To the young upstart from the Swiss patent office

Anything outrunning light was impossible,

And that meant

The 250-year old Newtonian picture of gravity

Was wrong.

If Newton is wrong,

Then why do the planets stay up?

Because remember,

The triumph of Newton』s equations come from the quest

To understand the planets and stars

And particularly the problem of