# Nova (1974–…): Season 42, Episode 21 - Inside Einstein's Mind - full transcript

On November 15th, 1915, Einstein published his greatest work: general relativity. The theory transformed our understanding of nature's laws and the entire history of the cosmos, reaching back to the origin of time itself. Now, in celebration of the 100th anniversary of Einstein's achievement, NOVA tells the inside story of Einstein's masterpiece. The story begins with the intuitive thought experiments that set Einstein off on his quest and traces the revolution in cosmology that is still playing out in today's labs and observatories. Discover the simple but powerful ideas at the heart of relativity, illuminating the theory-and Einstein's brilliance-as never before. From the first spark of an idea to the discovery of the expanding universe, the Big Bang, black holes, and dark energy, NOVA uncovers the inspired insights and brilliant breakthroughs of "the perfect theory."

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It's a mysterious force

that shapes our universe

It feels familiar,

but it's far stranger

than anyone ever imagined

And yet, one man's

brilliant mind tamed it

Gravity

Using simple

thought experiments,

Albert Einstein made

an astonishing discovery:

time and space

are shaped by matter

You get rid of this force

of gravity,

and instead, we have

curvature of spacetime

Right now, the space around me

is being squeezed and stretched

He called it the "General Theory

of Relativity"

How did one person,

working almost entirely alone,

change everything we thought

we knew about the universe?

Einstein is toiling

as the world seems to fall apart

He was able with pure thought

to solve the riddle

of the universe

"Inside Einstein's Mind,"

right now on NOVA.

Gravity

The most familiar yet most

mysterious of nature's forces

100 years ago, Albert Einstein

made a mind-blowing discovery:

what we feel as gravity

is in fact the push and pull

of space and time itself

He called his idea

"general relativity"

It is perhaps

the most remarkable feat

of thinking about nature

to come from a single mind

General relativity

is undoubtedly one of the

greatest scientific theories

ever conceived

It's a theory of space, time,

and gravity

One mathematical sentence,

and from it, you can derive

the understanding

of the entire universe

on the largest scales,

and that is beautiful

Only now, a century

after it was first proposed,

do we have the technology

to explore the extremes

of Einstein's great theory

Supermassive black holes

at the center of galaxies

Waves of gravity that

distort space and time

The evolution

of our entire universe

How did a concept

that explains so much

come from the mind of one man?

Einstein had a magical talent

He could take a hard,

physical problem

and boil it down

to a powerful visual image,

a thought experiment

Suddenly he realizes,

"This is how the world works

All this abstract nonsense is

the correct theory of reality"

To gain an insight

into Einstein's mind

and the true wonder

of general relativity,

we need to trace

the crucial thought experiments

that led to his great

breakthrough

The seeds for his ideas

were planted

when he was just a child

Einstein grew up

in a small house in Munich,

in southern Germany

His unique personality

was evident early on

Like many great innovators,

Einstein was a rebel, a loner,

but deeply curious

He was slow in learning to speak

as a child,

so slow that his parents

consulted a doctor,

but he later said that

that's maybe why he thought

in visual thought experiments

His sister remembers him

building little card towers

using playing cards

He was a daydreamer,

but he was deeply persistent

Einstein's father, Hermann,

manufactured electrical

equipment

He nurtured his son's interest

in science

On one occasion,

he brought him a compass

Now, you and I maybe remember

getting a compass

when we were kids,

and we were like,

"Oh look, the needle twitches

and points north,"

but then we're on

to something else,

like, "Oh look,

there's a dead squirrel"

But for Einstein,

after getting that compass,

he developed a lifelong devotion

to understanding how things

can be forced to move

even though nothing's

touching them

The young Einstein

became gripped by a desire

to understand the underlying

laws of nature

He developed a unique way

of thinking

about the physical world

inspired by his favorite book

The book Einstein loved

told little stories,

like what it'd be like

to travel through space

or go through an electrical wire

And it made Einstein think

visually

These imagined situations

that we often call

"thought experiments"

became a defining feature

of Einstein's thinking

One of the critical

thought experiments

that Einstein began to play with

very young,

around the age of 16,

was trying to imagine

what would happen

if he could catch up

with a light wave

It's one thing to imagine

a light wave zooming past him

at some seemingly

impossible speed,

but what if he could somehow

just propel himself

really quickly?

What would it look like

if he could catch up

with that light wave?

What would he see?

He said it caused him

to walk around in such anxiety,

his palms would sweat

Now, you and I may remember

what was causing our palms

to sweat at age 16,

and it was not a light beam

But that's why he's Einstein

This dream-like thought

about the nature of light

was Einstein's first step

on the path to his great theory

It stayed with him throughout

his time at school and college

He was extremely gifted

in science and math

as a young person

and very bad at other classes,

mostly because

he kept cutting class

and being very rude

to his teachers

Many teachers

from his high school days on

were convinced he'd never amount

to anything

He was a discipline problem,

and he was bad news

He applies to the second best

university in Zurich,

the Zurich Polytech,

and gets rejected

I'd love to meet

the admissions director

who rejected Albert Einstein

But eventually he gets in,

and he does moderately well,

but not good enough

to get a teaching fellowship

And so he ends up

at the Bern Swiss patent office

as a third class examiner

Undaunted by his

university results,

Einstein started work

at the patent office in 1902,

age 23

Here, his job was to assess

the originality of new devices

He was immersed

in the kinds

of technical details

that he'd been fascinated by

as a very young kid

And here he was,

sitting in the kind of wave

of the modern age

This was the era

of electrification

So all the latest clever ideas

for switching technology,

for coordinating clocks

in particular,

those were all

passing through his office

Time zones had recently been

introduced in central Europe,

and accurately

synchronizing clocks

was a major challenge of the day

Switzerland was a world leader

in time technology

Dozens of patents to link clocks

passed through Einstein's office

He could whip through

these patent applications,

and then out of his drawer,

he'd pull his physics notes,

and his boss was very indulgent

and would sort of turn

a blind eye

as Einstein was doing

his theories in his spare time

It's really important

to remember that

theoretical physics was new

when Einstein was a young man

You could do quite a lot

of this work by reading

a relatively small number

of science journals

and making the calculations

yourself

Einstein's world in 1905

was dominated

by two kinds of physics

One was about 200 years old,

founded by Isaac Newton,

a British natural philosopher

For Newton, all there is

in the world is matter moving

Newton showed that the motion

of falling apples

and orbiting planets

are governed by the same force:

gravity

His equations are so effective,

we still use them today

to send probes to the farthest

reaches of the solar system

The other important theory

of Einstein's day

covered electricity

and magnetism

That branch of physics

had been revolutionized in 1865

by the Scottish physicist

James Clerk Maxwell

Maxwell's theory describes light

as an electromagnetic wave

that travels at a fixed speed

In Newton's world,

the speed of light is not fixed

Einstein could see that

there's a contradiction

between Newton and Maxwell

They just don't fit together

And one of the things

Einstein hated... hated...

Was contradiction

If there's one kind of physics

that says this

and another kind of physics

that says that

and they're different,

that's a sign that something's

gone wrong and it needs fixing

For months, Einstein wrestles

with the problem

Eventually,

to resolve this contradiction,

he focuses on a key element

of speed: time

He realized that

any statement about time

is simply a question

about what is simultaneous

For example, if you say

the train arrives at 7:00,

that simply means that

it gets to the platform

simultaneous with the clock

going to 7:00

In a brilliant

thought experiment,

he questions what "simultaneous"

actually means

and sees that the flow of time

is different for an observer

that is moving

versus one that is

standing still

He imagines a man

standing on a railway platform

Two bolts of lightning strike

on either side of him

The man is standing

exactly halfway between them

and the light from each strike

reaches his eyes

at exactly same moment

For him, the two strikes

are simultaneous

Then Einstein imagines a woman

on a fast-moving train,

Traveling at close to the speed

of light,

what would she see?

As the light travels out

from the strikes,

the train is moving towards one

and away from the other

Light from the front strike

reaches her eyes first

For the woman on the train,

time elapses

between the two strikes

For the man on the platform,

there is no time

between the strikes

This simple thought

has mind-blowing significance

Simultaneity,

and the flow of time itself,

depends on how you're moving

If there's no such thing

as simultaneity,

then there's no such thing

as absolute time everywhere

throughout the universe,

and Isaac Newton was wrong

This concept that time,

and space as well, are relative

became known as

special relativity

It led to remarkable results,

such as the famous equation

relating energy to mass

Einstein published

this article in 1905

to exactly no acclaim

Most people ignored it

This was not setting the world

on fire

Two years go by

before a very eminent physicist,

Johannes Stark, invites Einstein

to write a review article

on Einstein's own work,

precisely because no one

was paying attention

And he begins thinking

about ways to generalize

and to push his own results

from 1905

What if he considers

not only a train

moving at a fixed speed

past the platform?

What if that train begins

to speed up or slow down?

What if there's acceleration?

Adding acceleration to the

equations was his first task

Then there was that mysterious

Newtonian force of gravity

to contend with

In Newton's theory,

gravity is a force

that acts instantaneously

But special relativity says

that's impossible...

Nothing can travel

faster than light

What Newton's theory

tells you is that

suppose the sun

were to disappear,

the orbit of the earth should

change at that very moment

But the notion of

"at that very moment"

in two different places

is exactly one of these notions

that special relativity

has told you

isn't a good physics notion

So you've now got this challenge

of trying to work out

how to take the success

of Newton's theory of gravity

but fit it into this new

special relativistic picture

It was only when Einstein

began to understand the link

between gravity and acceleration

that things began

to fall into place

We all know that

when we are accelerated,

and of course now we have cars

and airplanes

to give us the physical feeling,

if you're in an airplane

and it's taking off,

you are pushed back

in your chair,

you feel actually kind of

a force pushing you back,

which feels very similar

to the force of gravity

But you need the brilliance

of Einstein

to explain why they are related

Suddenly, he hits

upon what he describes as

the happiest thought of his life

If gravity and acceleration

feel the same,

perhaps they are the same

Again, he examines the idea

in a beautiful

thought experiment

He imagines a man in a box

floating weightlessly

in a distant region of space

in zero gravity

Suddenly, the man stops floating

and accelerates downward

until he's standing in the box

What has happened?

Either the box

is now close to a planet

and the force of gravity

has pulled the man to the floor,

or someone has attached a rope

and the box is now

being pulled continuously

and accelerated upwards

So which is it?

Gravity?

Or acceleration?

Without being able

to see outside,

the man can't tell what's

causing his fall to the floor

Einstein realized

there is no way

to tell the difference

between sitting

in a gravitational field

and being accelerated

These are equivalent situations

The fact that these two effects

are the same,

give the same result,

means that gravity

is acceleration

It's not just like acceleration;

it's the same thing

It's a big breakthrough

Einstein's theory

of special relativity worked

for motion at a constant speed

By extending his ideas

to acceleration,

he could begin to formulate

a new theory of gravity

In 1912, Einstein is living

in Zurich with his wife Mileva

and two young sons,

Hans and Eduard

The academic world had realized

the importance

of special relativity,

and his career had taken off

He's now a professor

at the esteemed Swiss Federal

Institute of Technology,

but spends as much time as

possible working on his theory

He needs mathematics

that describes how objects move

in space and time

and soon realizes that

the best tool for the job

is a strange but powerful

concept called "spacetime"

If I think of space,

I know that I can find anything

if I know where it is

north-south, east-west,

and up-down, three points

But that doesn't mean

I can find it,

because I also have to know

where it is in time

And so if we start to think,

to know everything

about an event in the universe,

I have to know not just

its spatial coordinates,

but also its time coordinate

I can begin to think

about where it is in spacetime

Imagine a camera

filming an action,

capturing each moment in time

as a single frame

Einstein basically tells us,

"Think of the movie reel"

So you have

all these little pictures

Now, cut them apart one by one

and stack them on top

of each other,

you get this pile

And if you go up in the pile,

you go up in time

And now kind of glue them

all together into one big block,

and that block

has both space and time,

and that's the spacetime

continuum

It's almost looking at a movie

not frame by frame,

but seeing the whole movie

at once

They would now be

kind of two strands

going up in space and time,

and they would be

kind of spaghetti strands

In fact, we all are

spaghetti strands

moving in this spacetime

Einstein feels that spacetime

is the natural arena

in which his theory

of relativity should play out

But now he needs

sophisticated mathematics

By your standard or mine,

Einstein was good at math

He was Einstein

But he was not really

a mathematician per se

He didn't prove theorems,

he didn't pore over math books

He was a physicist

He did thought experiments

He thought of very tangible,

concrete situations

and what would happen

So when it came time for him

to really bear down

to the absolute cutting edge

mathematics of his day,

he required help

At university, Einstein had

skipped the geometry classes,

letting his friend Marcel

Grossman take notes for him

Grossman had excelled

in geometry

and was now chairman

of the math department

He suggests Einstein

uses advanced mathematics

in which the shape of space

and time could be curved

Because spacetime

has a geometry,

he thinks to himself,

"Well, maybe it's the actual

shape of spacetime itself

that is giving rise to gravity"

After months of work, Einstein

has an extraordinary idea

"What if spacetime

is shaped by matter,

and that's what we feel

as gravity?"

In struggling to figure out

what causes gravity then,

Einstein has this great insight

It is simply that a mass

distorts the shape of spacetime

around it

So you get rid of this force

of gravity,

and instead we have

curvature of spacetime

In Einstein's universe then,

if space were empty,

it would be flat

There'd be nothing going on

But as soon as you

put objects down,

they warp the space and time

around them,

and that causes a deviation

of the geometry

so that now things start moving

Everything wants to move

as simple as possible

through space and time

But Einstein tells us that mass

sculpts space and time,

and it's the curved motion

through this sculpture

that's the force of gravity

We have this feeling that

the reason I can feel pressure

on the soles of my feet,

that the reason things are going

to drop when I throw them,

are because there's a force

attracting us down

to the center of the earth

What general relativity tells

you is that's not the right way

to think about

what's going on there

What's really going on is that

your natural path in spacetime

would take you to the center

of the earth,

and what's actually happening is

the floor is getting in the way,

it's pushing you upwards

When we look at it, we go,

"Ah, the force of gravity"

But Einstein says, "No, no, no,

the curvature of spacetime"

It's a stunning insight

Just as an ant might feel forces

pulling it left and right

as it walks over crumpled paper

when it's simply the shape

of a surface dictating its path,

Einstein saw that what we feel

as the force of gravity

is in fact the shape of the

spacetime we're moving through

Einstein now has

everything he needs

to formulate his final theory

of gravity

But he makes a critical mistake

He misinterprets

one of his equations,

and unaware of his error,

continues working

on incorrect ideas

The point at which Einstein

is going to give

the most essential equations

of the theory,

Einstein considers

something like them

and then says,

"Ah, but these don't work,"

and then writes down

the wrong equations

What follows are alternations

of confidence and despair

as he convinces himself

that everything was fine

with this theory,

and then he realizes

that things aren't so good

with the theory

It is a long, dark period

for Einstein

as he struggles

to reconcile himself

with a theory

that is just not working

Two years later,

Einstein is in Berlin

At just 36 years old,

he has one of the most

prestigious positions in physics

But he is still struggling

with his theory

By 1915, he'd reached

the pinnacle of the profession

He's in the Prussian Academy

and a professor

at the University of Berlin

But his marriage

is falling apart,

his wife and his two kids

have moved back to Switzerland,

so he's pacing around

almost all alone

in this apartment in Berlin

And now he has a competitor

Einstein had enthusiastically

shared his ideas

with the brilliant mathematician

David Hilbert

Hilbert was so impressed,

he decided to work

on the theory himself

Einstein is now

in a race to the finish

with one of the world's

best mathematicians

This is unfolding

in a remarkably dramatic period

in history

World War I has begun

to ravage central Europe

Einstein is not just toiling

in the abstract;

he's toiling as the world

seems to fall apart

By November 1915, Einstein

is scheduled to present his work

in a series

of four weekly lectures

at the esteemed Prussian Academy

But he's struggling

to formulate his ideas

In the midst

of these challenges,

letters arrive

from his wife in Zurich

pressing the issue

of his financial obligations

to his family

and discussing contact

with his sons

As his lectures begin,

his theory is still

far from complete

The pressure on Einstein is huge

He would give a lecture,

revise it, give it again

Spot mistakes, correct them,

get up on the podium,

explain what was wrong

in the previous week's lecture,

correct it and then move on,

and then do that again and again

for four weeks running

His work to convince them

of the truth

of this absolutely radical

new theory of relativity

that he was proposing

is one of the most intense

periods of work

in the history of science

Somehow, he's able

to focus on his theory

with an incredible intensity,

and he makes his breakthrough

He tests his equations

on a problem

that Newton's theory of gravity

couldn't solve:

the orbit of Mercury

Mercury's path around the sun

has an anomaly

that Newton's theory

can't explain:

it deviates slightly

each time it goes round

Einstein calculates the orbit

with his new equations

The answer is correct,

exactly what astronomers

had observed

He'd found the final equations

for his general theory

of relativity

You have to think about the

hubris of being Albert Einstein

He had already thrown out

Newtonian mechanics

with special relativity,

and then he had gone off

on his little personal quest

to incorporate gravity

And at the end of the day,

he boils it down to a prediction

for a number

that had been observed:

the procession

of the orbit of Mercury

And, miraculously,

when the pages of algebra

work out to their end,

you get the right answer

And suddenly, it's not just

playing with equations anymore;

he realizes

this is how the world works

All this abstract nonsense is

the correct theory of reality

Einstein is at last able

to present a successful theory

That's a triumphant moment,

one of the great moments

in the history of physics,

and, for Einstein, a victory

very much against the odds,

and he'd won

On the 25th of November 1915,

Einstein lays out his findings

in his climactic fourth lecture

at the Prussian Academy

He presents general relativity

The theory can be written

as a single equation

It condenses

sprawling complexities

into a beautifully compact set

of symbols

So the formula is really simple:

G-mu-nu equals

G for the shape of spacetime

and T for the distribution

of mass and energy

So this very simple formula

captures all of Einstein

general relativity

It's a beautiful,

simple equation

but it's a lot of work

to unpack the symbols,

the mathematical symbols,

and see how

in this very simple formula,

the whole geometry

of the universe is hidden

It's kind of an acquired taste

to see the beauty

It's also a signature formula

for Einstein

The true mark of his genius

is that he combines two elements

that actually live

in different universes

The left hand side lives

in the world of geometry,

of mathematics

The right hand side lives

in the world of physics,

of matter and movement

And so perhaps the most powerful

ingredient of the equation

is this very simple

equal sign here,

these two lines that actually

are connecting the two worlds,

and it's quite appropriate

they're two lines

because it's two-way traffic

Matter tells space and time

to curve,

space and time tells matter

to move

When Einstein presented

his great theory,

few people understood it

He needed a way

to prove to the world

that the counterintuitive

features of his theory

were real

The general theory of relativity

made predictions of things

which looked really strange

For example,

the idea that light bends

when it passes near

a very heavy body

No one had ever looked for that

No one had ever observed it

Einstein was desperate,

desperate to get astronomers

to make that test

Einstein's theory predicts that

when light from a distant star

travels close to the sun,

the warped space around the sun

bends the light's path

In May 1919, the English

astronomer Arthur Eddington

traveled to the African island

of Principe to record images

that would show this phenomenon

What Eddington

had been able to do

was take photographs of stars

during a total eclipse

of the sun

so the moon blocked most

of the brightness of the sun

and little pinpricks of light

could be seen around the sun...

Otherwise, it would be lost

in the glare...

And Eddington and his colleagues

were able to measure

that the appearance

of those stars had been shifted

compared to where

they would have been

had that big mass of the sun

not been deflecting that light

from far away

So Eddington's able to show

that Einstein's general

relativity theory is right

and a revolution in science

has been accomplished

When the eclipse experiments

prove Einstein's theory right,

he rockets to fame

not just because he's explained

a new way of looking

at the universe,

but at the end of World War I,

you had the predictions

of a German scientist

be proven right

by some British astronomers,

and it becomes headlines

across the world

The New York Times says,

"Lights all askew

at the heavens,

men of science

more or less agog"

This is back when newspapers

knew how to write

great headlines

But Einstein kind of loves

this fact

that he is now an icon

of science

Einstein becomes

a worldwide celebrity,

the icon of genius

we still recognize today

The only person

who was more widely known

was Charlie Chaplin,

and they got on

like a house on fire

Chaplin said, "The reason

they all love me

"is because they understand

everything I do,

"and the reason they love you

"is that they don't understand

anything you do

Can you explain that?"

And Einstein said

But in 1930s Berlin,

the Nazi party is gaining power

As a Jewish scientist, Einstein

becomes increasingly caught up

in the political turmoil

Einstein's theories

became a target

They were deemed

aesthetically repugnant

to a kind of Aryan sensibility

So people attacked not just

Einstein the Jewish scientist,

but they would actually

have people

denouncing general relativity

In January, Nobel Prize

mathematician Albert Einstein

visited California

He begins to make trips

to America,

where he is welcomed

with open arms

Germany's loss, America's gain

And in 1933,

he settles in Princeton

with his second wife Elsa,

taking up a position at the

Institute for Advanced Study

Today, the Institute is headed

by Professor Robbert Dijkgraaf

He basically was still

very much by himself,

just actually

as he was in Berlin,

just concentrating

on his deep ideas

and struggling

with understanding the universe

Of course, his office was here

At the Institute,

Einstein worked to unify

his theory of gravity

with the other laws of physics

With Einstein,

you see this phenomena

you see with many great

scientists...

That they climb

this very high mountain

and instead of celebrating

their success,

they're privileged to see

a much wider landscape,

and they see all these mountains

behind it

And I think he was

very much aware

how much still there was

to be done

Till the very last days

of his life,

he was trying to push

these equations

and find a description

of nature, all of nature,

in terms of the geometry

of space and time

But general relativity was

fading from mainstream science

Physics was now focused

on the quantum theory

of atoms and tiny particles,

a theory incompatible

with Einstein's ideas,

but one that could be tested

in the lab

Most of general relativity

was then beyond the reach

of experiment

When Einstein died in 1955,

age 76,

his theory was seen as one

with little hope

of future discovery

The best theories in physics

always take us to places

where the people who invented

them didn't imagine

And a truly wonderful theory

like general relativity

predicts all sorts of things

that Einstein didn't conceive of

The theory has a life of its own

We understand general relativity

much better right now

than Albert Einstein ever did

Liftoff of space shuttle

Discovery

with the Hubble space telescope,

our window on the universe

Today, 100 years

after general relativity

was first presented

Telescopes released,

okay, thank you

new technology

is allowing us to explore

the most remarkable predictions

of the theory:

an expanding universe,

black holes,

ripples in spacetime,

and perhaps the most bizarre,

the idea that not just space,

but time itself

is distorted by heavy objects

To prove it,

a team of physicists

is carrying out

a remarkable experiment

They're using two atomic clocks

that are in near perfect sync,

accurate to a billionth

of a second

The master clock

remains at sea level

while they take the second clock

to the top of New Hampshire's

Mount Sunapee

General relativity tells us that

as you move away

from the mass of the planet,

time should speed up

After four days

at the top of the mountain,

the test clock is taken back

to the lab for comparison

There, they compare it

to the sea level master clock

We'll put that one

into Channel A

Four days ago,

they were ticking in unison

Master clock in Channel B

But what about now?

You guys ready?

This is it right here

The time interval counter

is gonna show us

the time difference

between these two clock ticks

20 nanoseconds

You can see the time

difference between them

represented here graphically

of the clock that was up

at the mountain for four days

and our master clock

Gravity, the distortion

of space and time,

becomes weaker as you move away

from the surface of the planet

So while the test clock

was up the mountain,

time sped up

It's now 20 nanoseconds,

20 billionths of a second,

ahead of the sea level clock,

This is really awesome

This distortion of time

has surprising consequences

The Global Positioning System,

something we all take

for granted,

wouldn't work without

taking this into account

The engineers who built

the GPS system

we use every day

to pinpoint locations

had to ensure it adjusted

for the time difference

between clocks on satellites

and receivers on the ground

If they didn't, GPS would be off

by six miles every day

Your GPS units

use the results

of general relativity

When you navigate in your car,

you perhaps should give a word

of thanks to Uncle Albert

Of all general relativity's

predictions

that new technology

has allowed us to explore,

there's one that's

straight out of science fiction:

a black hole

Everything that we're

familiar with in ordinary life

is made from matter

But not black holes

Black holes are made

from warped space and time

and nothing else

A black hole is an object

that is spherical,

like a star or like the Earth,

with a sharp boundary

called the horizon

through which nothing

can come out

So it casts a shadow

on whatever is behind it

It's just a black, black shadow,

unbelievably black

This simulation shows

the distortion of starlight

around a black hole

Even though Einstein knew his

theory predicted black holes,

he found it hard to believe they

would really exist in nature

In the 1960s,

Professor Kip Thorne

worked on the mathematical

concept of black holes

The idea made sense on paper,

and he began to feel that these

science fiction-like objects

might actually be real

Must be here somewhere,

it's in one of these piles

Kip Thorne made a bet with

fellow physicist Stephen Hawking

about whether or not

a strong source of x-rays

known as Cygnus X-1

was in fact a black hole

I think it's in here

Yeah, here we go, relativity,

stars and black holes

Yeah, there it is

So that is a copy

of the famous bet

"Stephen Hawking

bets a one-year subscription

"to Penthouse magazine

"against Kip Thorne's wager

of a four-year subscription

"to a political magazine called

Private Eye

"that Cygnus X-1 does not

contain a black hole of mass

"above the Chandrasekhar Limit

It's witnessed this 10th day

of December 1974"

Stephen Hawking had

a terribly deep investment

in it actually being

a black hole,

and so he made the bet against

himself as an insurance policy

that at least he would get

something out of it

if Cygnus X-1 turned out

not to be a black hole

The evidence mounted thereafter

over the period

of the '70s and '80s,

and in June 1990,

Stephen snuck into my office

and signed off on the bet,

that finally, the evidence

was absolutely overwhelming

that Cygnus X-1

really is a black hole

And Penthouse magazine arrived

He sent me the British version

of Penthouse,

which was ever

so much more raunchy

than the American Penthouse,

actually

Enough to make my face turn red

when I received it at first

Today, we have evidence

suggesting that

there are millions of black

holes in our galaxy alone

But perhaps the most profound

prediction of general relativity

is that our universe

had a hot, dense beginning

that we call the big bang

The discovery that distant

galaxies are moving away from us

and that there's a background

radiation permeating space

provided evidence

for the big bang

and a universe that's growing

With this picture

of an expanding universe,

there were natural questions

Is the universe slowing down

as it expands?

Is it so dense that someday,

it will come to a halt

and collapse?

Will the universe come

to an end?

These seemed like good questions

To find answers, in the 1990s,

Saul Perlmutter and his team

observed exploding stars,

called supernovae,

to track the growth

of the universe

When we made the measurement,

we discovered that the universe

isn't slowing down enough

to come to a halt

In fact,

it's not slowing at all;

it's speeding up!

The universe is expanding

faster and faster

But what's pushing it?

In order to explain

the acceleration of the universe

within Einstein's theory

of general relativity,

we're considering an energy

spread throughout all of space

that we've never seen before

We don't know what it is

We call it dark energy

And, if so, it would require

something like 70%

of all the stuff of the universe

to be in this form of previously

unknown dark energy

So this is a lot to swallow,

and you might imagine that

at that point,

you should go back

and revisit your theory

The problem is that Einstein's

theory is so elegant,

and it predicts many, many,

many digits of precision,

that it's very, very difficult

to come up

with any other theory

There is one final prediction

of general relativity

that remains untested:

gravitational waves

There are huge things

in the universe happening,

like black holes colliding

or stars exploding,

and they create these

gravitational waves...

Waves in the shape

of space and time

that travel through the universe

at the speed of light

And so right now,

the space around me

is being squeezed and stretched

by gravitational waves

just getting here

from, let's say, two black holes

colliding a billion

light years away

But the squeezing and stretching

is so minute,

I absolutely could not

personally detect it

And so what we're trying to do

is build an instrument that can

In Louisiana

and Washington state,

a vast experiment called LIGO

is in the final phases

of calibration

It's hoped that laser beams

traveling two-and-a-half miles

between precisely aligned

mirrors

will measure

the squeezing of space

caused by gravitational waves

This could open up an entirely

new window on the universe

For 100 years,

general relativity

has been proven to be correct

time and time again

But Einstein himself knew that

his great theory had limits

It remains incompatible

with the quantum world

of tiny atomic particles

Here at the Institute

for Advanced study,

where Einstein worked,

the world's leading

theoretical physicists

are trying to solve the problem

Einstein never could:

finding a single set of rules

that applies to both the cosmic

and atomic scales

A unified theory

The Holy Grail of physics

We are now in what at this time

is the school of physics

So here,

people are still struggling

with many of the same issues

that Einstein would struggle

and are still trying to capture

the laws of the universe

from the very small to the very

large in a single equation

And it's still blackboards

that are the weapon of choice

The brightest minds of the world

are coming here

to work 24 hours,

seven days a week,

struggling to grasp the great

mysteries of the universe

And I think we are still driven

by the same dream:

that at some point,

we can capture everything

in elegant mathematics

100 years after Einstein

transformed our understanding

of nature,

the stage is set

for the next revolution

When we finally move

beyond Einstein,

it might be another singular

genius that comes along...

Someone struggling in a poor

school in Kenya right now

that we don't know about

Or it might be

20 different people

with 20 different points of view

gradually building

brick-by-brick

to finally figure out

a more comprehensive view

that includes general

relativity in it

I think the most important thing

that you learn from Einstein

is just the power of an idea

If it's correct, you know,

it's just unstoppable

It's extremely encouraging that

he was able with pure thought

to solve the riddle

of the universe

Once we had general relativity,

the world changed completely

Our point of view on the world

changed completely

I mean, the origin

of the universe

is a prediction straight out

of general relativity

We didn't have that before

I often wonder

what Einstein would make

of today's theoretical physics

I think he would really be

saying, you know,

"Get on with it, get the right

story, get the details right"

You know, you have

the huge universe,

and it obeys

certain laws of nature,

but where in the universe are

these laws actually discovered?

Where are they studied?

And then you go

to this tiny planet

and there's this one individual,

Einstein, who captures this

And now there's

a small group of people

walking in his footsteps

and trying to push it further

And I often feel,

well, it's this small part

of the universe

that actually is reflecting

upon itself,

that tries to understand itself