Einstein's Universe (1979) - full transcript

A documentary produced in 1979 to celebrate the centenary of the birth of Albert Einstein. Narrated and hosted by Peter Ustinov and written by Nigel Calder, the film takes place at the University of Texas' McDonald Observatory where a staff of renowned physicists take both Ustinov and the viewer through a hands-on experience of the exciting facets of Einstein's Theory of General Relativity.

All Texas. What?

All Texas. All Texas, yes, I know.

Might care to

look at that, Peter.

What is it? Oh...

"The essence of a man

like me lies just in

"what he thinks

and how he thinks,

"not in what

he does or suffers."

The time had

come for the rank amateur

to try to grasp the

way Einstein thought.

Yes, said Nigel

Calder, the writer,

my journey was really necessary.

There's the observatory now.

What,

those two little white

whatever they are?

That's right.

Well, the third

one I can see now.

Yes, they're the domes.

They, keep

a look out for aircraft

so as not to zap us

with their laser beam.

Are you serious? Quite serious.

They wanted me to

speak Einstein's words and

make the odd space flight,

but mostly just to attend to

the theory of relativity.

I was promised a tale of

how our perceptions of space

and time and color are distorted

according to where we are

and how we're traveling.

Amid such relativity,

Einstein found

reliable laws governing

atoms, planets, stars

and all creation.

Yes, an escort. Perhaps

to make quite sure I didn't

Funk the cerebral adventure

they had in store for me.

Very nice flying.

Thank you very much indeed.Thanks.

On my arrival,

I knew only that

Albert Einstein was

a gentle genius whose

reasoning anticipated

our world of

nuclear energy

and space flight.

The Big Bang. The black hole.

Things I'd only heard about.

My tutors were

to be leading experts,

assembled in this

remote corner of Texas,

for my benefit,

and of yours.

Our guides through

Einstein's Universe.

Dennis Sciama,

here, is a theorist

concerned with the overall

nature of the universe.

Roger Penrose,

he pioneered the

modern theory

of black holes.

You've heard of them.

Yes, yes, I have,

without understanding

what they are.

Well John Wheeler,

here, said they had to exist

and named them black

holes as a matter of fact.

He's very much a grand old

man of theoretical physics.

I see. Oh, there's

some more... Oh, yes.

And Wallace Sargent,

here, thinks he's discovered

a huge black hole.

Well he looks

as if he's photographed

just at the moment of

discovery, doesn't he?

Quite pleased

with himself. Yeah, with everything.

Irwin Shapiro,

you'll hear how he's been

getting radar echoes

from the planets. USTINOV: Yes.

And Sidney Drell's

a theorist from the

high speed world of

subatomic particles.

Gracious! And Ken Brecher,

here, he's checked

some of Einstein's

basic assumptions

with very precise

astronomical tests.

A formidable range

of expertise but they,

they look friendly enough.

I then became aware

that there might be

more to those motorcycles

than met the eye.

As we journeyed

into the mountains,

Calder told me that

the Theory of Relativity

burst upon the world

more than 70 years ago

when Special Relativity

proclaimed

the curious effects of

high-speed motion.

General Relativity,

he said, followed later

as Einstein's Theory of Gravity.

But we were to take them

in the reverse order and

approach the bewildering

distortions of time

by way of

a gravitational black hole.

I'm just nosing in towards

the black hole... now.

For our celebration

of Einstein's Relativity

and the famous formula

that powers the universe,

the venue was the

McDonald Observatory

of the University of Texas

and the observatory's main

telescope was our window

on Einstein's universe.

With a light

gathering mirror a

107 inches wide,

it's not the largest

in the world but

a very impressive

instrument all the same.

Oh, it's charming. Isn't it though?

Yes. Quite a telescope.

Already I found

a posse of relativists

at my shoulder

and affording us the use of

the telescope to embellish

our little seminar was the

director of the observatory,

Harlan Smith.

See the

gigantic counterweight here.

That's merely a counterweight?

Yes, many people ask

what that's for but

it's just dead weight.

The air was decidedly

thin on the mountain top.

They bring you up here,

getting you in some sense

closer to the stars I suppose,

and then present you with

stairways at every turn.

More steps? More steps.

You're standing very close

to one of the portholes

which the light can emerge.

We can put an instrument on

there to analyze the light.

Becomes a main

collecting mirror.

But it's also interesting

to see the control console

down there.

It's really remarkably small

for all the functions it does.

You mean that's

the dashboard for this?

That's all it takes.

Well this is McDonald and this

kit peak. This one...

They did everything

to help a greenhorn understand

modern astronomy in

it's Einsteinian modes.

And that's a tracking

station in Madrid,

the Bond telescope...

So basic are

Einstein's ideas to

modern knowledge

that confirming them is

now a global industry.

When I prowled through

the observatory it seemed

like a set

for some drama in space,

and in a sense it was.

About science, Einstein and

I had only this in common,

we both hated the way

it was taught to us at school.

He transcended that...

I drowned in it.

John Wheeler began

my rather belated rescue.

Thanks to you not

being a scientist,

we're all going to

have to give this account

the simplicity

that Einstein would

have loved.

Where do you think we

should the account, John?

With gravity?

Nothing could be better.

Everyone has to deal

with it every day.

Gravity.

Well let's see what the

astronauts made of gravity

on the moon.

I'm very proud

to have the opportunity here

to play postman.

What could be a better place

to cancel a stamp than right

here at Hadley Rille.

I, I remember this

from the time...

Now in my left hand

I have a feather...

In my right hand a hammer.

I guess one of the reasons,

we got got here today

was because of a

gentleman named Galileo,

a long time ago,

who made a rather

significant discovery

about falling objects

in gravity fields.

And we thought that

where would be a better

place to confirm his

findings than on the moon.

And, so, we thought

we'd try it here for you.

And the feather happens

to be, appropriately,

a falcon feather

for our falcon.

And I'll drop the two of

them here and hopefully

they'll hit the ground

at the same time.

How about that?

I have here a hammer

and a bird's feather.

How about that?

If you were Galileo,

how would you in the light

of that, try to persuade

people that everything

falls at the same rate?

Difficult.

Difficult.

Air resistance is a

whole problem isn't it?

So it's such a

wonderful thing

that air resistance

for objects like this

doesn't count so much.

Fantastic.

What a feat

for Galileo to realize

that everything falls

at the same rate.

But for Einstein it

was a still greater

act of imagination to realize

that the reason those

things all move the same,

they get their moving orders

from the same piece of space,

it's not the distant Earth,

it's the space right

where they are.

"There came to me the

happiest thought of my life.

"Consider someone in

free fall, for example,

"from the roof of a house.

"There exists for

him during his fall

"no gravitational field."

And Einstein really

tells us that gravity

is an illusion.

I can toss,

across to Dennis,

a ball

and that arc looks as real

as anything could be.

And I can toss a ball

across to Sid

and the arc looks as

real as anything could be.

But Einstein tells us that

the arc is a pure illusion.

If we could only cut away

this grid with a welder's

torch from underneath us

and all fall freely,

then, as I toss that

ball, it would

move in a beautiful

straight line.

Einstein tells us

that in a local,

freely falling frame,

there is no gravity.

Einstein would

have loved to see those

astronauts in Skylab.

They were weightless.

They were in free fall.

Einstein's great idea,

all objects fall

because they get their moving

orders right from space.

Skylab had no power in orbit

and no force acted on it.

It went just as straight

as possible through space.

But space is warped

around the earth.

So Skylab could end up and

did end up going in a circle.

Warped space was

Einstein's style of thinking.

Moving about in warped space

is no more mysterious

than traveling

about in these mountains.

You just can't go

in a straight line.

To go in a straight line you

must go down on the plain.

Well, like everything

else, light, it seems,

responds to gravity.

And so space is warped.

Coaxing me over that

fence was Irwin Shapiro.

One of the important

questions we have to decide

is whether something

is straight or warped.

How can we do that?

We need some frame of reference.

For example,

if you were to look at

this line of posts

and trying to decide

whether they were straight

or not, how would you do it?

Well, you'd presumably,

look along it.

I think I could have

told from there but

it's almost straight.

Right. You squinted

along it and really,

your frame of reference

was the light rays

and that's a very good

technique, however you

can get fooled

if the light itself gets bent.

For example, water bends light

and we can illustrate that

here with these two rulers.

I put these two rulers

in the water and ask

you to decide whether

the bottom one or the top

one is actually straight.

Well, since water bends light,

the bottom one looks straight

and obviously isn't.

That's right.

See, when we pull it out,

when they're out of the water,

you can see clearly that the

bottom one is the one

that's bent and the top

one is the straight one.

In fact, if you look

from the earth at light from

a star beyond the sun,

the sun's gravity bends

the light of the star as

it grazes it's limb.

And so, the position of the

star appears to change.

Einstein calculated

the bending of light

using this idea of curved space.

As seen from the earth,

certain fixed stars appear

to be in the neighborhood

of the sun

and can be observed during

a total eclipse of the sun.

At such times these stars

ought to appear to be

displaced outwards

from the sun as compared

with their apparent

position in the sky when

the sun is situated at another

part of the heavens.

A ray of light going past the

sun undergoes a deflection of

1.7 seconds of arc.

That prediction, in 1915,

led to world fame for Einstein.

In fact, there was a total

eclipse of the sun in 1919

and a team of

British astronomers

went to observe this total

eclipse in the tropics.

And here's a plate taken

from that expedition,

of the sun during

the total eclipse.

This is a negative

so you don't see the sun at all,

it's a blank field...

...and these

black striations are

the solar corona.

And very tiny black dots

are the stars in

the field of view.

And the relative positions

of these stars were

measured very accurately

and compared with

corresponding measurements

of a photograph taken

of the same stars

when the sun wasn't

in the field of view

and the results showed

the star positions shifted

during the total eclipse

in approximate agreement

with Einstein's predictions

and certainly quite different

from what Newton

would have predicted.Oh.

Newton, forgive me.

You found the only path

barely open in your time

for a man of the

highest powers of

thought and ordering.

The concepts which you created

still guide our thinking in

physics even today

although we now know

that they will have to

be replaced by others,

farther removed from the

realm of direct experience,

if we aim at a deeper

understanding of

relationships.

Nowadays, we

needn't await a total

eclipse of the sun

to attempt to make

measurements of the

deflection of light,

we can use radio waves.

According to Einstein's theory,

radio waves, just like light and

x-rays or any other

light-like radiation,

is predicted to behave

the same way under the

influence of gravity.

Instead of ordinary

stars in our galaxy,

with radio waves we observe

the much more distant

objects called quasars.

Just like the visible stars,

quasars seem to change position

in the sky when the sun

comes into line with them.

With the radio technique,

we can also achieve

far better accuracy.

The most accurate

measurements were done

at the National Radio

Astronomy Observatory in

Greenbank, West Virginia.

This experiment confirmed

Einstein's prediction

for the bending

to within about one percent.

Powerless, then,

to question that gravity

bends light,

we tried our skills with

an impressionistic

model of warped space.

They urged me to

believe that the

distortions of space due to

a massive body like the sun

could shape the course

of lesser objects like

the planets.

The table maker

gratuitously added

bottomless pits of gravity,

black holes that would

swallow an unskillful ball.

Black holes aren't

getting much to eat today.

Einstein wouldn't

be happy if we didn't tell

you his story

in the simplest words.

Space tells matter how

to move and matter tells

space how to curve.

That's it.

Throw this ball past the sun.

That's light

changing its direction,

but not through some

mysterious force

acting through space

but through the

warping of space itself.

Or put a planet

into orbit around the

sun and watch it go.

And where does it get

it's moving orders from?

Not from that sun

but from the space

right where it is.

Or put Skylab

into orbit around the earth

and ask those people on

Skylab what do they see.

They get their moving orders

from space itself,

right there, where it is.

Einstein's wonderfully

simple picture of it all.

Or the moon going

around the earth.

Pull the earth away,

unwarp space and

the moon will fly off.

Happy to go in a

beautiful straight line.

But cosmic

space isn't, after all,

a distorted tabletop.

I bared my misgivings

to Dennis Sciama.

How on earth, or rather,

how in the universe

can nothingness have shape?

That is indeed

a difficult question

and the Greeks struggled

with it very much.

They had a geometry of their own

and light, responding

to that geometry,

would move in straight lines.

That's not at all the

case in Einstein's theory.

He uses a different

geometry from the Greeks.

A geometry in which space is

warped and light responding

to that geometry

doesn't move in straight

lines but is bent.

And a planet responding to

that geometry would move,

let's say, in a circle

around the sun.

Einstein himself was very

concerned to stress

this difference from the old

geometry and he tried to

make it plain to all of us.

On the basis of the

general theory of relativity,

space, as opposed

to what fills space,

has no separate existence.

There is no such

thing as empty space,

that is space without

a gravitational field.

The geometrical properties of

space are not independent but

they are determined by matter.

It seemed that either

Newton's force of gravity or

Einstein's warped geometry,

would keep the planet circling

in the same stately fashion.

But who was right?

In Einstein's theory,

the orbits are predicted

to be slightly different

than they are in

Newton's theory.

For example, let us

consider a single planet

in orbit about the sun.

In Newton's theory, this

planet would be predicted

to follow an elliptical path,

that is a path sort of

like a stretched out circle.

And in Newton's theory

this path would be

followed continually,

ad nauseum, following

the same elliptical

path all the time.

Whereas in Einstein's theory,

this path actually

swivels around.

That is the ellipse rotates

very slowly in space.

Near the sun,

gravity's a little stronger in

Einstein's theory

than in Newton's.

So close in, the planet

teeters for a moment

before climbing away.

This

different prediction

of Einstein's theory

actually cleared up a

nineteenth century mystery

about the orbit of

the planet Mercury,

the closest one to the sun.

The ellipse corresponding

to the orbit of Mercury

is not stationary

with respect to the

fixed stars, but rotates

exceedingly slowly.

The value obtained for this

rotary movement is

43 seconds of arc

per century.

This effect can be explained

by classical mechanics only

on the assumption of

hypotheses which have

little probability.

On the basis of the general

theory of relativity,

it is found that the

ellipse of every planet

must necessarily

rotate in this manner.

In the late 1960s

we used the Haystack radio

telescope in Massachusetts

to measure the swivel

of Mercury's orbit.

This telescope is enclosed in

a ray dome to protect it from

the wind and the sun.

What we did was use

this radio telescope

with an attached radar system

to send pulses of radio energy

towards Mercury and

to detect the echoes.

In fact, although the power in

the transmitted radar signals

is about 500,000 watts,

enough to supply the

electrical needs of

a small town,

the echo we detect is so weak

that its power is even

less than that expended

by an average housefly

crawling up a wall at the

rate of only a millimeter

per millennium.

By measuring these echoes

from Mercury, periodically

over several years,

we were able to detect the

swivel of Mercury's orbit

because the echo delay is

different for a swiveling than

for a non-swiveling orbit.

Our results confirmed

Einstein's prediction

to within one percent.

There's an amazing object

that's been discovered in

the sky that swivels in

its orbit far more than

Mercury does.

This object illustrates

beautifully Einstein's

relativistic effect.

The object is called

a binary pulsar.

An object lying

far off among the stars,

the binary pulsar,

was evidently quite invisible.

By what new ingenuity

could they track its orbit?

Kenneth Brecher

patiently explained.

Imagine a rapidly moving

vehicle coming down the

road... A motorbike say.

As it comes towards you,

you hear a high pitched roar.

When it passes you,

the pitch drops

with a change in frequency

according to whether

the source of sound is coming

towards you or going away.

That's the Doppler Effect.

The same thing happens with

light or with radio waves.

Police speed traps

use Doppler radar.

It sends out radio waves that

bounce off the vehicle

and come back with a

higher frequency.

The faster you're going the

more the frequency is changed.

The Doppler Effect is an

unbeatable way of measuring

relative speed.

Now imagine an object,

circling, giving out

its own radio pulses.

You'd find the frequency

rising and falling repeatedly.

You could tell it was circling

even if you couldn't see it.

Completely out of sight

among the stars there's

an orbiting pulsar.

It's nature's gift

to the relativist.

A pulsar is a collapsed star,

a neutron star we call it,

which ticks like a

very accurate clock

emitting regular beeps

of radio energy.

This particular pulsar

changes its beep rate

in an eight hour cycle as it

sweeps forwards and backwards.

But did you discover

this binary pulsar?

No, I didn't discover the

pulsar but all of us who

are working on

relativity and astrophysics

are incredibly excited

about it.

It's a unique object and

a unique opportunity to

test the laws of general

relativity in a very

precise way.

It's being studied at

the Arecibo radio observatory

in Puerto Rico.

Joe Taylor and Russell

Hulse of the University of

Massachusetts discovered it

and Taylor has been checking

up on it every few months

ever since.

We're right on source? Yeah.

Following errors? No.

Thank you. Good.Okay.

Hello, everything still

going all right?

Yeah, fine.

One of the marvelous

things about it is the changes

are so predictable

that when they switch

on the pulsar always

clocks in right on cue.

The pulsar is in a very tight,

fast orbit

around another collapsed

star that's not directly

detectable.

And the pulsar's

orbit changes in the

Einsteinian manner.

It swivels 30,000 times faster

than Mercury's orbit does,

four degrees a year.

The binary pulsar's

very nice evidence

for Einstein's effect.

But really, to milk it

for all it's worth in

confirming relativity,

Taylor still has years

of work to do.

And in fact there's

some things still more

exciting in prospect,

which is that as the binary

pulsar goes round,

according to Einstein, it

radiates gravitational waves.

The result of that would

be that the orbital period

would change slowly

and Joe Taylor is trying

to detect this change.

In fact, just the other day,

Joe Taylor sent me a

new manuscript of his

in which he claims to

begin to measure this effect

and it does seem to fit

Einstein's theory very well.

These gravitational

waves that Einstein predicted

are ripples of warped space.

And with the help of a

computer, theorists have made

movies of gravitational waves

that ought to pour out

from violent events

like the collapse of a star.

And there's an interesting

kinship, isn't there, between

gravitational waves

and the familiar

tides of the sea

that are raised on the

earth by the warped

space around the moon.

We're a long way from

the sea here so we can't

actually see

the ocean moving up and down

the way it does

in a spectacular

fashion on the coast but,

as a matter of fact,

at this observatory

they have measured how the

rocks of the earth move

under the moon's influence.

They move up and down by as

much as a foot twice a day.

Unsettling

to think of the earth

heaving like that.

But the force of the tides

gave a certain palpability

to warped space.

Wheeler then offered me a

warped miniature table and

a jar of quicksilver.

You'll notice that you have

one of the blobs of

mercury pulled right out,

stretched out

and nothing is a more

beautiful illustration of

a tide effect than that.

What you can, if you'd like to,

to illustrate that

gravitational waves

are also tides,

is take that blob of

mercury and jiggle it

and you notice it changes

its shape, first this way

and then that way

and there just isn't a more

beautiful illustration

of what a gravitational wave is

than the tidal stretching of

that little blob of mercury

or the tidal stretching of a

gravitational wave detector.

One of the things that

interests me most about

the whole thing

is the push it's going to

give to technology,

because looking for

gravitational waves,

we have to get down to what

everybody calls the quantum

limit of measurement,

and that's a new

thing in the world,

and it's going to mean

new kinds of equipment

that show up all over the map.

Engineering, biology,

medicine... What have you.

You can try to detect

very slight ringing

in great super cool metal

cylinders like the one at

Stanford in California.

In Glasgow, they have

a different method.

Look at some of the

details of the optical

systems down in here.

Ronald Greaver uses laser beams

that shuttle to and

fro many times.

And that's to measure

shifts in the position

of different masses,

shifts that might be caused

by gravitational waves

washing through the earth.

But it's incredibly delicate.

They're getting ready to look

for movements far, far smaller

than the width of an atom

between masses mounted about

30 feet apart.

It's possible that

stars going round one another

very rapidly can be detected.

It's possible that violently

exploding star like supernovae

will be detected

and it's even possible that

objects falling into massive

black holes

will produce gravitational

waves we can pick up.

And if any of those

things happen,

we'll be seeing the effects

Einstein predicted

of warped space propagating

actually with the

speed of light.

The McDonald

Observatory had its

own laser

and after hearing about clever

experiments in other places

I was to see one

in progress myself.

We've put those waves

of gravity behind us, Peter,

and come back to basic issues

about gravity and orbits

and warped space.

What they do here is shoot

their laser at the moon

to check its distance

and movements to within

a matter of inches.

The moon's a heavy object

but the earth is heavier still

and they might respond

differently in the

sun's gravity.

Then, we might see the

moon's orbit drifting a

few feet closer to the sun

and Einstein would be wrong.

Fantastic sight of the moon.

The moon looked splendid.

No amount of scrutiny

by science can efface

its terrible beauty.

You probably want it back now,

don't you, Robert?

Yes.Yes.

Very wise.

To reflect the laser

pulses from the moon,

the Apollo astronauts

set down a series of corner

cubes on the surface

at various locations.

Exactly like the cubed corner

I have here in my hand.

Take a look at it,

you look in at this face,

and you'll see that no matter

what direction the light

enters the corner cube,

it has he remarkable property

of coming out again in

exactly the same path, but

in the opposite direction.

The Soviet Union

landed two Lunar HUD

vehicles on the surface

of the moon and each of them

carried an array of corner

reflectors that were

built by the French.

And tonight we're going to

try and get echoes back

from one of these

Lunar HUD vehicles.

Lunar HUD 21, which you can see

in the upper right hand

corner of the moon,

over there.

Oh yes.

Eric Silverberg

took up the story.

We fired

the laser every three seconds

which produces an

extremely intense pulse of

light that starts at the

far end of the room and

then expands

up through this tube

hitting two reflections

and then more until it

fills the entire mirror,

107-inch mirror, which

gives us a very parallel

beam of light

to send up to the moon.

We typically fire from

300 to 400 shots in

each 45 minute period.

Since the laser pulse

is about three feet long,

going up to the moon we can

very accurately time

how long it takes

to get there and back.

We always have to station

an aircraft observer outside

the dome to keep track

of any possible nearby

aircraft because of the

intensity of the beam.

We're going to start ranging

on the reflector now

and Robert will

start firing at

the Soviet, site.

His job is the most demanding

because he has to

point the telescope

with an accuracy which is

equivalent to trying

to hit a penny

at a distance of perhaps a mile.

And we help him out

as much as we can

by putting a small

red flash on the image

of the moon in order

to, show him precisely

where the beam is pointed.

In really good conditions

we can get a return

back on the teletype

perhaps every fifth or

every tenth laser shot.

And when it happens

they ring a bell

so that Robert knows precisely

whether or not he's located

at the right position.

But even with such precise

measurements, it's not easy

to calculate the moon's orbit

because of the myriad

of small effects that

influence its motion.

My colleagues and I use the

measurements made here at

McDonald to actually compute

the moon's orbit to very high

accuracy and found

it to agree very well

with Einstein's claim.

So Einstein's theory has again

withstood another stringent

test and rival theories

are put under much greater

constraints if they're

going to be in

accord with the

behavior of nature.Fantastic.

I left them

contentedly ringing the

bell for Einstein while

tending a half-baked bun

of comprehension in my brain.

I'd pictured the moon

faithfully circling in

the warped space

around the earth and the

sun's gravity toying with

our own great planet.

Einstein wouldn't be happy

if we didn't tell you his

story in the simplest words.

Space tells matter how to move

and matter tells

space how to curve.

Warped space didn't

trouble me too deeply.

I remembered how easily

any exercise in straight line

geometry can be botched.

If the young Ustinov could

bend the world...

Why not Einstein?

But to step onto

the quicksands of

Einsteinian time,

er, that was uncanny.

Unsuspectingly, I watched

next morning as a visitor,

John Engelbrecht,

measured the speed of light.

I'm generating the light pulse

with a sparker which

I'm going to turn on here.

And that creates sparks,

essentially, short beams

of light

that travel across

to the other dome

where we have the mirror

and the mirror reflects the

beam of light into this

telescope right here, where we

have a photo-multiplier tube

to pick up the light signal

so that we can look at it

on the oscilloscope right here.

We measure the time interval

by measuring the distance

between the two blips on the

oscilloscope where distance

across the screen is time.

Looks like about

450 nanoseconds?

And the round-trip distance

is 134 meters.

Yes.

Well it's not bad.

You've determined the

speed of light this

morning to be about

298 million meters per second.

An accuracy of about, oh about,

oh, about, one percent.

Um, the speed of light is in

fact, Peter, known to,

great accuracy.

It's one of the most

precisely known numbers

in all of physics.

The national Bureau of

Standards in the United States

has a figure of

about 299,792,457.4

meters per second.

Point four?

Well, the National Physical

Laboratory in London

er, perhaps would disagree

with the last figure.

Yes, I thought so.

Einstein

was emphatic that

a blast of light is

always a constant no matter

what the motion of the source

or the motion of the observer.

I've checked this, in fact,

using not light but x-rays

which are a form of light

but at very high energies.

In 1970, a satellite

was launched off the coast

of Kenya for the purpose

of doing x-ray astronomy.

It was called Uhuru.

It discovered and

began observing a

peculiar class of star.

An x-ray binary pulsar gives

off regular bursts of x-rays

while orbiting at high

speed around another star.

Now suppose that

Einstein were wrong

and that x-rays go faster

if they were launched

when the pulsar is moving

towards the earth.

Then x-rays from that part

of the orbit could overtake

x-rays that are coming from

the other part of the orbit,

making a simple picture

quite complicated.

For example, you could see

the pulsar coming and going

at the same time.

Peter, from my

friend Ethan Schreier

at the Smithsonian

Astrophysical Observatory,

who worked on the

Uhuru satellite,

I got the following

tracing of x-ray pulses

coming from the

x-ray pulsar Centaurus X-3.

And as you can see by

looking at these pulses,

they're absolutely regular.

Each pulse comes along

at a specific time interval

and there are no spurious

ghost pulses lying in between

the pulses that we see here.

This is direct proof that

the speed of light

is indeed independent of the

velocity of the source.

I looked at three

separate sources.

The most distant one, lying

in the small Magellanic Cloud,

the light took 200,000 years

to arrive at the earth

from that source.

And in all that time,

the pulses emitted

when the pulsar came

towards us, never

overran those that were

emitted when it went away.

By more than a factor of

perhaps a part in a billion.

To put it in earthly

terms, that would be

about the speed of a

turtle moving along the ground.

That's a very earthly term.

In deference

to this evident obsession

of Einstein's,

I accepted that in cosmic

space the speed of x-rays

or visible light or

radio waves, never varies.

But, dear me, how promptly

that golden rule was broken.

If we send radio pulses

to another planet like

Mercury or Venus

when they're on the other

side of the sun from earth,

they can appear to be slowed

down by the direct effect

of the sun's gravity

on the waves as they

pass near the sun.

It looks,

from where we are,

as if the sun's gravity

acts very like a lens, bending

the light and slowing it down.

About fifteen years ago

it occurred to me

that this increase

in the travel time

was a direct consequence

of Einstein's general

theory of relativity.

In those days of increasing

science budgets and

low rate of inflation

it took less than two years

to convert that idea into

a very sophisticated radar

system which we installed

on the Haystack telescope

to make these measurements

on Mercury and Venus.

Now the actual predicted

effect is very small,

it's only 200

millionths of a second out

of a total round-trip time

of about 1,500 seconds

or approximately

one part in 10 million.

And we were able to

measure it with an accuracy

of approximately five or

ten percent with this

radar experiments.

Now, if we could turn to Mars...

You can't expect

to make that image

of Mars just now

because it's right

on the far side

of the sun

and it's close to the horizon.

But, maybe

we'll get an impression.

Mars is now

very near the far side

of the sun

as we view it from Earth

and is in a good position

to see this effect.

And in fact, the last time

Mars was in this position,

we used radio waves

sent to the Viking spacecraft

which we landed on

the surface of Mars

to measure

this predicted slow-down

much more accurately.

And with such measurements

we're able to verify

the predictions of

general relativity on

regard to the slow-down

to an accuracy of about

one-tenth of one percent.

Okay, you say

light slows down

near the sun.

But Ken Brecher told us just now

that light seems

always to go at

the same speed.

I think, Peter,

that as a theorist,

Roger Penrose here

might resolve that

contradiction for us.

Yes, well, you see,

it really depends where

the measurement is done.

If you measure

the speed of light

as it appears at

the surface of the sun

from here

then it would seem

as though it slows down.

It would seem as though

the sun was surrounded

by some sort of lens

that should not only

slow the light but

also bend the light.

But if you did

the measurement at

the surface of the sun

then you would get

the same answer

for the speed of light

as you get from

the speed of light at

the surface of the Earth.

We had come to the nub.

To keep his blessed

speed of light always

reading the same,

Einstein decided that

time itself must slow down

near a massive object.

So gravity has

the apparent effect of

reducing the speed of light

and slowing down time.

So if you imagined

the extreme situation

of a black hole

then light would be reduced

to zero speed apparently

and time would apparently

have been stopped

completely at the surface.

Apparently?

Well, I feel awfully guilty

asking this because

I'm opening,

as they say here,

a new can of peas,

but we've heard so much

about black holes.

What is a black hole apparently?

Yes, well, according

to Einstein's theory,

if you have the final fate

of a very massive star,

would be an object

so concentrated

that light itself

couldn't escape from it.

The object collapses inwards

and, signals,

light, any other kind

of signal, any object,

cannot escape from this region

into which the star

would collapse.

The black hole that results

from the collapse of a star

several times

the mass of the sun,

would be an object

several miles in diameter.

But if you, say,

imagined the Earth

compressed right down

until it became a black hole,

the dimension would be

a bit less than an inch

or something like that.

That's the Earth? The Earth would have

to be compressed

into that size to be

a black hole. USTINOV: I see.

So, you shouldn't be candid.

- Don't worry.

- I see.

Light at

the surface of a black hole

trying to escape

would hover there forever.

And judged by us,

looking from a safe distance,

time there appears to stop.

You'd wait forever for

the next tick of the clock.

A short distance away

from the black hole,

time does seem to pass

but rather slowly

by our reckoning.

You can think of

the black hole to be

surrounded by shells

in which time runs

progressively faster.

That's what happens

in the immediate vicinity

of a black hole.

But the effects on time extend

for thousands of miles

with time getting

gradually closer to what

we regard as the normal rate.

If you imagine

that little black hole

with the same mass as the Earth

and surround it by

a sphere representing

the Earth's surface,

where we live,

our clocks run at

the appropriate rate.

There isn't really

a black hole at

the center of the Earth

but time at the Earth's surface

is so little

just as if they were.

Compared with

the very gradually

increasing rates of time

way out in space high above

the Earth's surface.

"The observer will

interpret what he sees

"as showing that one clock

"really goes more slowly

than another clock.

"So, he will be obliged to

define time in such a way

"that the rate of a clock

depends on where

the clock may be."

Peter, the interesting thing

about general relativity

is that my clock,

whether I'm sitting here

on the surface of the Earth,

whether I'm orbiting

around a black hole,

will appear to me

always to be running

at the same rate.

The gravitational effects

don't change the actual

clockwork mechanism,

and don't affect it in any way.

Nonetheless, from

your point of view,

you might see my clock

running at a different rate

and we would appear

to have time running

at different rates.

We could correct for this,

and general relativity

in fact tells us

exactly how to do that,

um, but the,

the clocks themselves

are in fact not disturbed

by the gravitational field.

Yeah. I... I don't quite

understand one thing

because obviously

we are our own

terms of reference

and therefore our clocks

are our own terms

of reference,

they become part of us.

If I take an airplane,

as we all do

and fly very high,

is there what is shown

on the clock face

affected by the fact

that I have flown high

or not, by the time I arrive?

Yes, it is in fact affected

and when you come back

it will read differently

from the identical clock

which you left behind

which didn't take part

in the airplane ride.

But although the clock reading

is different when you come

back on the ground,

the clock,

once it's back

on the ground

will continue to run at

the same rate it used to

run on the ground.

So that the difference

in reading will then

remain constant

as time goes on.

The important point

is that this effect is

not a psychological effect.

It's a genuine,

measurable, physical effect.

In the last decade or so,

extraordinarily accurate

atomic clocks

have been made

which are sensitive enough

to see these very small effects.

Such that, for example,

the difference between

the rate of a clock

running on the ground

and one running

on the second story

of a building

could be observed and

measured very accurately.

Oh, so Big Ben's been

wrong all the time

because it's at

about the eighth floor?

I see. Right, it's gaining

relative to your clocks.

My common sense

was outraged, of course.

Yet, recent results

have evidently smothered

all expert

and inexpert doubts

about Einsteinian time.

Sidney Drell set the scene.

The atomic clock is

not just an instrument

for scientific laboratories

to run their equipment with

or part of their play

equipment.

In fact, in everyday life

it sets the time

by which we live.

Here, one has

a crystal oscillator

which keeps time

relative to an atomic clock

which signal is

being received here

with due allowance for

the time it takes for light

to bring the signal here.

Here is the time

that it's reading out.

I notice that my own

crystal watch

is two seconds slow

by the time given there.

Well... Mine is

six seconds out.

That's terrible.

Well, this will go

back to the maker.

Back in Washington,

there sits the master

atomic clock

against which all

other time is referenced

for an international

time standard.

The atomic clocks

keep time to an accuracy

which approaches one second

out of a million years.

That is how far they have come.

To understand the atomic clock

we have to now enter

into the theory of atoms.

And this is another theory,

the theory of,

how light is emitted

and absorbed by atoms

and how light propagates

with very sharply

defined frequencies.

There's another,

theory to which Einstein made

very enormous contributions.

Sometimes we think

of the year 1905,

when Einstein was 26 years old,

as one of the miracle years

of the world.

Because in that year

when he was giving us

special relativity, Peter,

he was also giving us

the theory of light

occurring in discrete packages

and with precise frequencies.

It was, in fact,

with this work

that in 1921,

he received the Nobel Prize,

when the relativity theory

was still viewed as

too mathematical,

too controversial

and not really of

practical importance.

This side of

Washington, they keep

the clocks

that directly answer

your question, Peter,

about how time passes

in an aircraft.

Karel Ally of

the University of Maryland,

and his colleagues,

put one set of atomic clocks

aboard a US Navy airplane.

And this was starting in 1975.

And you remember, on the moon,

those man-made

corner reflectors,

well, the aircraft

carried one of them

to throw back

yet more laser pulses.

Providing a link to

another set of clocks

kept in a cabin

on the ground for comparison.

The same types of atomic clock?

Yes,

they're twin brothers

in effect.

The prediction

of general relativity

is that as you get

higher above the ground,

the grip of gravity

on time weakens

and your clock

should run a little faster.

The laser flashes

coming from base

serve to check the time

recorded in the air

against the readings

of the clocks on the ground

while the aircraft flew around

and around Chesapeake Bay.

The ground radar

kept track of it.

The aircraft's speed,

by the way, also had

a very small effect on time

by a quite different

prediction of relativity

but the experimenters

took that accurately

into account.

Yes, I'm sure they did.

The main effect

on time related to

the aircraft's height.

At 35,000 feet,

the airborne clocks gained

about three billionths

of a second every hour,

and each flight lasted

about 15 hours

and five flights like that

accurately confirmed

the effect of gravity on time.

So Einstein's account

of how the world works

triumphs yet again.

"To punish me

for my contempt for authority,

"fate made me

authority myself."

And what's true

of atoms and atomic clocks

is also true of atoms

in ordinary objects

like an apple.

And perhaps

we could draw some

of these threads together

by telling, how in a time shell,

starting at the top of a tree

and moving into a time shell

lower down,

an apple manages to accelerate

in the way that's so familiar.

It's moving

into shells, very fine shells,

of ever slowing time.

Its atoms are

operating more slowly.

It seems to be

losing internal energy

which has to reappear

in some new form

and the form it takes

is energy of motion.

So the apple is going faster

and faster as it moves down

into slower and

slower zones of time.

Until finally it hits the ground

and that energy of motion

is destroyed.

Well, Nigel,

just two little points

I'd like to clarify

before we all go further

into this adventure.

It seems to me that

the apple has acquired

such a particular status

with Newton, that perhaps

one ought to realize

for uninitiated agriculturalists

that pears and grapes and,

in fact, people are subject

to the same laws,

that pears are not exempt.

Exempt from

the action of gravity.

Well, certainly not, because,

especially since Einstein,

the emphasis in present thinking

is that gravity

affects everything

in just the same way.

And in the case of people

our atoms also are affected

in that rate of operation

according to whether

we're living down

in the valley

or up on the mountain.

I found the propositions

of general relativity

easy to state.

Gravity bends light

and warps space.

Gravity slows down light

and slows down time.

Bewilderingly simple, really,

as their full meaning sank in.

You could think,

if you dared, of visiting

a black hole

and hovering there for a while.

And there in

the slow running time shells

close to the black hole,

perhaps only

a few years would pass

while hundreds of years

were passing on Earth.

Maybe you'd like

to imagine yourself

as twin brothers

testing this theory.

"The adventurous one

is my twin brother, Peter,

"and my cautious one

is... Albert."

And Peter

wanted very badly to

investigate this black hole.

He's always

been reckless. You coming?

You silly boy.

It's going to be great up there!

That's certain.

How about that?

That's the last

we've seen of Peter on

this Earth anyway.

Would I dare make

the imaginary journey

to the black hole now proposed?

Well... Why not?

Goodbye!

Goodbye.

Oh, do take care.

I shook the dust

of the 20th century

from my feet

as my imagination bounded

towards the black hole.

I'm just nosing in

towards the black hole now.

I'm just nosing in towards

the black hole now.

Well...

At least that black hole

has slowed down

the hectic pace of his life

but I hope to God

he takes care.

The rate of time

seemed entirely normal to me,

but on the Earth

it was evidently racing along.

The gravitational

effects don't change the

actual clockwork mechanism.

Nonetheless,

from your point of view,

you might see my clock

running at a different rate.

Pictures from

the Earth showed the days

passing in a matter of minutes.

I saw who won

the Grand National

in 1990 but I shan't tell.

It was hard to make out

what Albert was saying

in mission control.

Anyway, your will is in spirit

and we'll be able

to celebrate any moment now.

Yes!

A happy new century!

Happy day... Yeah.

Missed the bloody bottle!

I see, you look very spry,

yes, you do.

Twenty-first century?

We're still 20 years off

by my reckoning.

As years passed

on Earth and only months

on my spaceship,

my greatest concern

was for Albert.

My twin brother was aging

before my eyes.

As for me, I was only

a few months older.

Well,

it would appear that

Mr. Einstein was right.

Eh, Peter?

As you can see,

I'm still trying

to look after you

in spite of...

Nurse...

It wasn't long before

the Earth forgot all about me.

Time to go home.

Before I could even think

of playing Rip Van Winkle

in the world of

the 21st century,

there was one visit

I had to make.

Alas, poor Albert.

Even in imagination,

this time travel

by means of gravity

seemed a joyless enterprise.

There was no method

for retracing my steps

through Einsteinian time

and returning

to the 20th century.

We've talked about

the warping of space

and about the effects

of gravity on time,

in space and time.

But relativists like

to combine the two

into space-time.

With time as being

the fourth dimension.

"The

non-mathematician is seized

by a mysterious shuddering

"when he hears of

four-dimensional things.

"By a feeling not unlike

that awakened by thoughts

of the occult.

"And yet, there is no more

commonplace statement

"than that the world

in which we live

"is a four-dimensional

space-time continuum."

Here we are

at a certain place

in Western Texas.

And the time

is half past eleven.

Put the two together...

I clap my hands,

that's an event

in space-time.

Now each of our lives is

a series of such events

strung together

into a world line in space-time.

And here we meet together,

our world lines more

or less intersect.

In order to get

a picture of space-time,

it's convenient to think

of space as represented as

a two-dimensional flat plate

and that frees

the third dimension

to represent time.

Now, let us imagine

an object which is

stationary in our description.

Then this would be represented

by a vertical straight line.

An object

which is moving uniformly

but with some velocity,

would be represented again

by a straight line but

now tilted over.

What about an object

which is accelerating?

Then that would be represented

by a curved line.

This is the world line

of the object.

Now let's think of the sun,

that again,

thinking of it as stationary

would be represented

by a straight line

and the Earth,

in orbit around the sun,

would be represented

by a spiral line.

But then the Earth, as we know,

is in free fall and should

therefore be represented

by as straight a line

as you can draw.

And how is it that it's drawn

as this spiral line?

Well, this is because

the space-time is

really curved.

Now, remember

our deformed billiard table,

the space then would be

warped in a certain way.

And as the space evolves

to give us our

space-time picture,

the whole space-time

is slightly deformed.

And this is why

the apparently curved picture

of a spiral motion of the Earth

is really as straight

a line as you can have

in this curved geometry.

And I gather

that I feel the burden

of gravity here on Earth

because I go against

the grain of space-time.

Gravity feels

the same as acceleration

but, according to Einstein,

in an important sense,

gravity is the same

as acceleration.

In a gravitational field

things behave as they do

in a space free of gravitation.

If one introduces

a reference system

which is accelerated.

Do you want me to try it?

Try it. Never get off the ground

with me in it.

What Einstein

called a reference system

which is accelerated

was for me a curiously

dumpy helicopter

to be flown

as delicately as possible.

I'd ridden

some awkward steeds

for the movies

but nothing quite

as undignified as

doctor's scales.

As the helicopter

lurched upward,

my weight increased.

Each brief acceleration

adding pseudo-gravity.

Whenever we climbed steadily

or hovered, my weight

went back to normal.

And when the pilot

let the machine

accelerate downwards,

a nasty feeling that...

"Oh! How the pounds

melted away."

In some neglected

slot machine of my mind

a penny dropped.

When a vehicle accelerates,

lurching in one direction,

all its loose contents

are left behind

and seem to fall

in the opposite direction.

As the master said,

"It's just like gravity."

Acceleration could also put me

on different scales of time.

Stand by, Albert.

It's not only gravity

that affects the rate

of a clock

and sew the passage of time,

even motion can do that.

And Einstein showed that

already in 1905,

ten years before he developed

the general theory

of relativity.

What Einstein showed

was that if an observer

moves out

into interstellar space

at high speed

and finding himself

amongst the stars,

then turns round

and comes back at

close to the speed of light,

while the journey for him

will seem short,

for the people who stay at home

it will seem much longer.

For instance, he will find

that he has aged less

during that journey

than the person

who has stayed at home.

A little lonely

up here in space.

Long after I'd fired

my motors to turn for home,

my twin brother Albert

was still receiving signals

sent by me

on the outward leg

of the journey.

Again, time seemed

to me to pass normally.

But it was

in this melancholy phase

of my return journey

that I observed poor Albert

growing older by the hour.

Just as for the visit

to the black hole,

this high speed

relativistic flight plan

took me on a one-way ticket

into the twenty-first century.

Although he lived

before the space age,

Einstein made many

imaginary journeys like this.

Gedanken experiments.

"Thought experiments,"

the physicists called them.

"One could imagine

that the organism,

"after an arbitrarily

lengthy flight,

"could be returned

to its original spot in

a scarcely altered condition

"while corresponding organisms

which had remained in

their original positions

"had long since given way

to new generations."

Einstein said that

many years ago,

but, people for many years

didn't really accept

that notion.

It, in fact, was

the source of much argument

and was elevated

at times into the notion

of a paradox.

But now,

with very fast moving

atomic particles,

we have displayed

this affect with

extreme accuracy.

Most precisely,

atomic particles in

a storage ring at CERN,

so-called new mesons

which normally live

a very fleeting fraction

of a second,

perhaps a millionth

or two millionths of a second,

have been shown to

have their lives extended

by a factor of thirty or so

just by having them move

at speeds very close

to the speed of light.

Well, I understand

that this is possible

for particles

but it does sound rather

like science fiction to me

and like fantasy, would it be...

Would it be really

possible for this to happen?

For people, I mean.

Well,

this is a matter of faith,

not a matter of science.

There's nothing in principle,

I believe, that stands

in the way

of getting one up to speeds,

that are a significant fraction

of the velocity of light.

And, when one thinks

of the incredible things

that we do with

instruments these days,

measuring with accelerators

that are many miles long,

timed to precisions of

billionths of a second,

I would be the last

to think it's impossible,

and won't be done.

After all, we did send men

to the moon and look

for how many centuries

that seemed impossible.

Presumably, one of the great

advantages there would be

if human beings ever

attempted to travel

between the stars,

that you not only gain in

an apparent extension of life,

as compared with the Earth,

but also you can travel

greater distances

than you would think possible

by normal reckoning of

speeds from the Earth.

I would say it's not

only an advantage,

it's a requirement

because distances

to other, stars,

and their presumed planets

are so great that

there's no way

we're going to ever

explore them if we don't

stretch out our lives,

our time scale.

It was one of

Einstein's earliest

ideas in relativity

that you could distort

time and space just by

traveling fast enough.

We've now left gravity

and general relativity

aside for a while

to hear instead

about special relativity

and the strange

effects of motion.

Now let's imagine

that these bikes

are capable of, say,

half the speed of light.

That's what

their speedometers

show anyway,

fractions of C,

the speed of light.

What kinds

of Einsteinian effects

can we illustrate

with bikes like these?

Perhaps you should start

with the simplest point

of all.

From the point of view

of the rider,

he's at rest and

it's the landscape

that's rushing towards him.

In Einstein's

democratic universe,

that point of view

is just as valid

as yours or mine.

And then recall

the Doppler effect,

the change in frequency

in color of light.

An object rushing towards you

looks blue because the light

gets crowded together.

It has a higher frequency.

When it's going away

it looks red because

the light gets stretched out

and then it has

a lower frequency.

I'd like to emphasize

something there, Peter.

Compared with ordinary

white light,

blue light has

a higher frequency

and more energy too.

But red light represents

a low frequency and

less energy.

Einstein made

two important discoveries

about the Doppler effect.

First, it doesn't make

any difference who is said

to be moving.

It's just the relative speed

that counts.

Einstein's second discovery

about the Doppler effect

is that when

a high speed vehicle

is just passing you,

strange things happen.

Imagine that you were

quick enough to

photograph it with your camera.

You ready, Peter?

As the vehicle passes us by,

you'd think it would be

neither red-shifted

nor blue-shifted

because it's moving

perpendicular to

our line of sight.

But, in fact,

it's slightly red-shifted.

What's more,

it's rotated away from us.

Not shortened.

Many accounts of relativity

would have the bike

squeezed short.

No, it still appears

to be undistorted

but slightly

rotated away from us.

But from the point of view

of the rider,

it could be

very peculiar distortions

of the scenery

if you rode past buildings,

say, almost at

the speed of light.

Perhaps the first thing

you notice...

...is the building

and the truck

curve in a little.

Then, as you speed up,

you see that they seem

to be twisted towards you.

Indeed, as your speed

increases closer

and closer

to the speed of light,

you start seeing the far sides

of the building and truck.

You seem to be seeing

right around the corners.

It's like walking

through a rain storm

when your front gets wet

and your back stays dry.

The light approaches you

from unexpected directions.

Consider two bicycles

coming at each other at

close to the speed of light.

You might think that

their combined speed,

the rate at which

they are coming together,

is faster than light.

But from each rider's

point of view, it's not

like that at all.

Their combined speed,

as they measure it,

always remains less

than the speed of light.

Einstein launched

his disconcerting ideas

from very simple premises.

The riders demonstrated

why time runs slowly in

a fast moving vehicle.

They just rode in company

and threw a ball to

represent a signal,

a flash of light.

From their point of view,

the light went straight

across between them.

But from our point of view,

as onlookers watching

the bikes go by,

the signal went obliquely

and on a longer path.

But light always moves

at the same speed

so that the time

it takes for the signal

to go from there to here

takes longer from

our point of view

than from the point

of view of the riders.

So Einstein tells us

that their clocks

in the moving frame

move slower than ours

in exactly proportioned

of this line to this line.

High speed travel

also makes you seem heavier.

Time for rapidly moving bikes

slows down and it accelerates

more sluggishly.

Mass means resistance

to acceleration

and the bike's mass

piles on as it gets

near the speed of light.

In fact, it continues

to grow more massive

without limit

as it gets very close

to the speed of light

so that, in fact,

it never can go

faster than light.

But from the point

of view of the rider,

his mass seems

the same as usual.

When Einstein realized

just how much

the way things look

depend on where you stand,

he also saw a danger.

Because, he reasoned,

the laws of physics

must be the same

for the rider, as for

the fixed observer.

Special relativity

was born brilliantly

out of that requirement.

But the price

Einstein exacted from us

was the scrapping of

the old ideas about time.

Einstein realized that

although each person's

view of events

is a little different,

everyone's view

is equally valid.

And yet we are observing,

all of us, the same

laws of physics.

And the touchstone

for the reliability

of physical laws

was Einstein's old obsession,

the speed of light

remaining constant

amid all the commotion

of the cosmos.

Now, because

of its motion in orbit

around the sun,

our Earth is traveling

at a speed of about

30 kilometers a second.

If the principle of relativity

were not valid,

we should expect

the laws of nature

to depend on

the Earth's direction

of motion at any moment.

But the most

careful observations

have never revealed

any lack of prevalence

of different directions.

This is a very powerful argument

in favor of

the principle of relativity.

But Einstein's

revelations shook the planet.

From the reasoning

of special relativity

emerged a law

of creation and destruction.

It was time for us

to consider the realm

of the atom,

where relativistic events

are more usual than on

the roads of Texas.

First, for real motorcycles,

the velocities are much too low

for the effects

of relativity to

be noticeable.

Even, with a spacecraft,

circling the Earth

every 90 minutes,

the speeds are too low.

They're being moved, in fact,

about one forty-thousandth

the speed of light

and, their increase

in mass due to motion

is less than

one part in

a thousand million.

Astronomers looking

at distant stars

and distant objects

are seeing systems moving

with a substantial fraction

of the velocity of light.

And when we enter

the atomic realm,

we, enter into an area where

the relativistic effects

are very noticeable.

Even on your television screen,

the electrons that paint

the television screen,

are moving with perhaps

20 to 30% of

the velocity of light.

And, thereby their mass

is increased to the order

of a percent or so.

Out at Stanford, at the

linear accelerator center,

we produce the highest

energy electrons in the world.

They come so close

to the speed of light

that their mass is increased

by a factor of 40,000,

compared to what

they started with.

As a result of this very high

velocity and high energy

that they acquire,

their clocks are slowed down,

and they don't realize

that they have moved

a full two-mile

of our accelerator.

In fact, from

the electron's point of view,

their clocks

are moving so slowly

they think they have gone

only two and a half feet

by the time they come

to the end of the accelerator.

At the end of the accelerator,

we also have a storage ring,

so-called sphere ring,

where we smash the particles

into one another.

We create new matter.

And in this way we can

very accurately measure

the conversion of energy

of motion into matter.

And into mass. And in this way

confirm with great accuracy

the Einstein equation, E = mc2.

What an equation that is.

It looks so innocent.

E... Energy, M... Mass,

and C...

Not the speed of light

but the square

of the speed of light.

An enormous number.

So that a little mass

is worth a lot of energy.

It's hard to appreciate

what an enormous

leap of intuition

and imagination

it took to come

to this simple formula.

Einstein had been thinking,

from the age of 16 to 26,

consistently about

the nature of light

and electromagnetic radiation

and almost as a by-product

of his... Of his,

thinking on this subject,

he came to

the following conclusion,

that if you look at light,

say, from the sun,

and if you were moving

towards the sun,

as we've already discussed,

the light would become bluer.

Now, the blue light has more

energy than the white

light we normally see,

and therefore, he reasoned,

there must be more energy

apparently coming from the sun.

But if that energy is not

drawn from any change

in the motion of the sun,

it must mean that

that energy is coming

from the mass itself.

And so he concluded

that the mass of the sun

itself is converted

directly into energy.

He then made the enormous leap

to generalize this result

to all forms of energy.

In the 19th century,

there had been

energy of motion,

and energy of light,

energy of heat,

but not inter-convertible.

And so he came to

the startling conclusion

that all mass

and all energy

are in fact equivalent.

"We are led to the more

general conclusion

"that the mass of an object

is a measure of

its energy content.

"It is not impossible

"that with materials whose

energy content is variable

"to a high degree,

for example with radium salt,

"the theory may be

successfully put to the test."

What Einstein is noting here

is that the energy released

in nuclear reactions

is so great that there is

actually a measurable change

in the mass.

That can be detected

and his formula

can be verified.

The, nuclear burning together

with the Einstein

relation, E=mc2,

solved a long-standing riddle,

namely, how is it that

the stars, the sun,

can burn for billions of years

without running out

of, material?

This equation, E=mc2,

and the efficiency

of nuclear burning,

were tested

quantitatively in 1932,

by Cockcroft and Walton

with their accelerator.

They verified it

for the first time.

But it was

a long time before any

practical use was made of it.

Einstein was hounded

out of Germany,

he came to Princeton,

where I had the pleasure

of seeing him

after his arrival.

But it was five years

from that until

that fateful day

when I went down

to the pier in New York,

and a ship came in

with Niels Bohr,

and the word of

the discovery of

the fission of uranium.

January 16, 1939,

and not long after

that Einstein wrote

that fateful letter

to Roosevelt with

all its consequences.

"Extremely powerful

bombs of a new type may

thus be constructed.

"I understand that Germany

has actually stopped

the sale of uranium

"from the

Czechoslovakian mines."

And it was hardly 200 miles

from here across the desert,

that that first

dramatic explosion took place

that brought us into

the true atomic era.

Einstein,

who set it all in train,

was appalled by

the nuclear arms race.

It's ironic that this humble,

gentle man who had been

an avowed pacifist

should now be etched in

the history of mankind as

the father of nuclear weapons.

He believed, as do many today,

including many scientists

who are familiar with

the devastating effects

of these weapons,

that survival in a world

with nuclear weapons

is one of the great

challenges of our generation.

It was, I believe,

his last official act,

to endorse a manifesto in 1955

with Bertrand Russell,

which I believe

you have here.

Yes.

"We appeal to you

as human beings

to human beings.

"Remember your humanity

and forget the rest.

"If you can do so,

the way lies open

to a new paradise.

"If you cannot, there lies

before you the risk

of universal death."

I think, in talking about

Einstein's great achievement,

we should really stress

the fact that it lies at

the basis of all life.

The nuclear weapons

are only a small by-product

of human folly.

Even when I strike this match,

a minute amount of the mass

is converted into energy.

If I took all the mass

in this match,

and converted it

into free energy,

there's enough energy here

to lift the entire mountain,

on which we're sitting now,

about ten feet off the ground.

This energy plays a role

in the hum of a violin,

in the growing plants here,

and in fact in the expansion

of the universe.

All of astrophysics is

about nature's attempt

to release the energy

hidden in ordinary matter.

Energy defined by

the equation E equals MC2.

So I learned

to perceive the sun,

hot enough in Texas,

as a natural nuclear furnace

and a typical star.

Energy can create matter,

so matter has hidden energy.

Falling down, like the apple,

can liberate some of it.

So Wallace Sargent led me

back to gravity,

saying it can overwhelm a star.

When the sun

grows old, it will

first of all

become a red giant,

in which it becomes

much bigger

and a little cooler

than it is now.

At this time, the Earth

will be consumed,

but fortunately,

it will not happen for

several more billion years.

After that,

the sun will shrink

and become a white dwarf

which is about the

size of the Earth.

During this time,

a lot of hidden energy

will be released,

but not as much as

has been released by

nuclear burning at

earlier stages of

its evolution.

Stars much more

massive than the sun

end their lives as supernovae,

that is they undergo

gigantic explosions.

During this event,

the inner parts of the star

is driven inwards

in an enormous implosion.

This forms a neutron star,

which in turn becomes

a pulsar.

The matter in

the neutron star

is extraordinarily dense,

and the atoms

are crushed together,

and a substantial fraction

of the hidden energy

originally in the star

is set free.

Well, so neutron stars exist,

but theoretical calculations

tell us

that some thing of three

times the mass of the sun

can't exist as a neutron star.

It's a short step

from a neutron star

to matter being crushed

by implosion into

a black hole.

In the case of

a collapsed star,

ten times the sun's mass,

the resulting black hole

would be only about

40 miles across.

Nothing could escape

from it, not even light.

Material falling into

such a black hole

would liberate tremendous energy

just before disappearing

into the hole,

giving out intense x-rays.

And these x-rays

could be seen

from the Earth,

and that's in fact how

we could expect to

detect such a thing.

Well, the x-ray source

called Cygnus X-1

meets these specifications

and may well be

a black hole.

And it's sucking

material apparently from

a companion super giant star.

Well, now we're on Cygnus X-1.

What we can actually see here

is the companion to the star.

Not the black hole itself.

The black hole is

orbiting around the

star that you can see.

This is a record of

the extra emissions

from Cygnus X-1.

And you see there's

no regularity in it

as there would be

if it were a neutron star.

No, they're not

very regular, are they?

The quest for

black holes was, for me,

the culminating proof

that Einstein's theories

still inspire the very

latest research.

It led us to distant

galaxies of stars

as big as our own Milky Way,

but erupting most violently.

In order to explain many of

the phenomena out there

in the universe,

we have to invoke

enormous energy sources.

And it looks more and more

as though black holes

may be the only possibility

to provide such large

sources of energy.

In this kind of theory,

an enormous black hole

with a mass

probably several billion

times the mass of the sun,

sits at the center of the

galaxy and releases energy

in some way, which we

don't yet understand,

by swallowing entire

stars and gas from

the surrounding galaxy.

For the past couple of years,

several of us

have been paying particular

attention to the galaxy M87.

It's a very distinctive galaxy

with a jet of luminous matter

poking out at one side.

M87 is a strong source

of radio waves

and also x-rays.

And all together,

it's a very energetic galaxy.

Most of the work

that we've done

has been observations

at the Kitt Peak

Observatory in Arizona

and at Palomar Observatory

in California.

We've used a very

sensitive light detector

brought out from London

by Alec Boksenberg.

What we do is to

look at slices of M87

at different distances

from the center and

use the Doppler shift

to tell how fast

the stars in the galaxy

are moving around.

What we find is that

the stars in the

very center of M87

are moving around

much more rapidly

than we would expect.

As far as we can see,

they're moving fast

because they're orbiting

around an invisible object.

But we can use

the speeds of the stars

to estimate the mass

of this invisible object.

It turns out to be about

5,000 million times

as big as the sun.

Just about the kind of mass

that we would expect

for a black hole,

if it really is powering

all the phenomena

that we see in M87.

The problem is

that the volume you would

expect for a black hole

of the mass that we think

the one in M87 has

is very small indeed.

And so, really,

the problem is to try

and resolve much smaller

angular distances.

Small, angular distances.

I suppose that's the penny

at a distance of

a mile again.

In order to try and do this,

I've turned radio astronomer

and with colleagues used

the radio telescopes

at Goldstone in California,

and at Madrid in Spain,

5,000 miles away.

The object is to try

and get a telescope

as large as the Earth

by means of which you can

resolve very small distances.

I'd just like to know,

at this juncture,

to what extent is all this

a logical consequence

of Einstein's work

or has it already

taken off on its own?

Well, it was certainly

not known to Einstein

that black holes would be

a consequence of his work.

On the other hand, later work,

since Einstein died in fact,

has pointed very clearly

to the fact that

within his theory,

at least, within

general relativity, one...

This is a very clear

prediction of the theory.

And of course,

independent of

the actual nature

of the underlying object,

we know that it has to

put out a great deal

of energy because

we see that directly.

And that implies huge

underlying mass from E=mc2.

And of course the light

that we get directly

from the object

as analyzed by

Wallace Sargent...

Well, they used the

Doppler Effect

and didn't pose

to us as photons.

So the richness

of Einstein's ideas

bears on the entire range

of actual observations

of these objects.

A computer charted

the fathomless warp of space

in an imagined collision

between two black holes.

Our ancestors

frightened themselves

with dragons and hobgoblins,

we have Jaws and black holes.

In fact, at the dead center

of a black hole,

I found that even

Einstein's ideas falter.

Here, if general relativity

can now be

adequately applied to

the black hole itself

and a certain distance in,

then it's possible to show

that even the theory itself

predicts its own downfall.

And this is one of the things

which was not appreciated

before Einstein died.

Certainly, everything

does get compressed into

a very, very small region.

And there comes

a point somewhere,

when new physics has to come in.

The argument really is

at what point

and what new physics comes in.

Of course, when you're

at states of very

high density,

you can no longer deal with

gravitation in isolation,

while the other

forces of matter,

the strong nuclear forces,

the weak forces of

radioactive decay

and the electromagnetic forces.

Nor can you stay strictly

within the realm of

classical physics

and ignore the quantum ideas.

Yes, you're right.

It's ironic that Einstein,

who was a founder of

the quantum theory

through his discovery of

the quantum of the photon,

which is the particle of light,

never felt comfortable,

never felt satisfied

with that theory because of

the element of uncertainty,

the element of chance

that it brings in

to a description

of the behavior

of particles.

Apprehending

more than I could

possibly comprehend,

I listened like a child

allowed to stay up late

to ideas that might

surpass Einstein's.

On a theoretical front here,

I might say that

it seems to me

we're no closer to knowing

where we're going.

They are the very

beginnings of efforts

to make a super gravity theory,

a quantum theory that

embraces gravity and

the other forces of matter

that are all unified

together in this great

dream, the grand synthesis

that Einstein spent 30 years,

the last 30 years of his life

trying to create and failed.

That in alone is a measure,

a statement of how difficult

the problem is.

When you get

down to the size of

an elementary particle,

the question is,

does the concept

of space and time

still apply at a

smaller scale than this.

And I think most physicists

would take the view

that it does apply

and that it goes on

until you're down to

a tiny fraction of

the size of a particle.

But this sort of line

that we're following

is one which suggests

that perhaps things go wrong

before that and the idea

is that the point,

the concept of

a point in space is

not the primary concept.

This is only

a mathematical artifact,

and that something

a little closer to the idea

of a particle, although

not actually a particle.

It's a thing that

we call a twister,

which is, um...

Well, it's something

I couldn't explain in detail,

but the idea is that

the concept of a particle

and of space itself

are both things

which emerge out of this

more primitive concept.

And this is the line

we've been pursuing

for many years now.

And one of the great

problems is to see

how to tie it in

with general relativity

in a very clear way.

And there are some

encouraging features,

but it's certainly

not finished yet.

From the minutest

quantities of space

to the immensities

of the universe,

the director recognized

the little boy in me

and he let me drive the big

telescope across the sky.

Beautiful, isn't it? USTINOV: Yes,

that's fantastic.

The rings of Saturn

mapped for me

the warped space

surrounding the giant planet.

As I scanned the Milky Way,

Harland Smith reminded me

that the stars,

billions of them,

and including the sun,

all circle under

their mutual gravity.

And we looked beyond

our own galaxy

to similar whirlpools

of stars far away

in space-time.

To sample a few of

the billions of galaxies

prepared me for

contemplating the

whole of Einstein's universe

and its presumed origin

in the Big Bang.

And it was brought home to me

how Einstein's discoveries

about space and time,

light and matter,

all connect and make

a girdle of the universe.

Could we pull Einstein's

ideas all together.

Energy has mass

and mass has energy.

And the mass of the sun,

so gigantic,

has only to be burned up

a little at a time

to provide us with all the

heat and light and power

that we see here on Earth.

But that mass has

more gravitational pull

that pulls light, bends it,

pulls other stars,

and when stars

start flying apart,

in the earliest days

of the universe,

that gravitational pull

slows down their

outward flight.

The universe

comes into being

out of nothingness.

Matter, light, energy.

All at once.

And this matter, this light

and this energy,

all expand, get more dilute.

Contract into stars,

galaxies, planets

and the whole thing

goes on expanding,

getting bigger, farther apart,

and that's the phase

we live in now,

as these galaxies are flying

apart from each other.

But then comes the moment,

we believe, down the line,

when they stop flying apart

and their gravitational

attraction

pulls them back together again.

The whole thing contracts,

energies go up once more,

we get to a

gigantic, big crunch.

In its pristine form,

60 years ago,

general relativity clearly

required the Big Bang

for the birth of the universe.

But that melodramatic story

conflicted with the astronomy

of the day,

and Einstein doctored

his equations to describe

a more restful universe.

"In order to arrive

at this consistent view,

"we admittedly had to

introduce an extension

"of the field equations

of gravitation,

"which is not justified by

our actual knowledge

of gravitation."

"The introduction of

that cosmological term

"was the biggest

blunder I ever made."

"Death alone can save one

from making blunders."

In fairness to Einstein,

just about the time that

he made this remark,

astronomers' ideas

of the universe were

changing rapidly.

It was discovered

about that time

that not only

was there our Milky Way galaxy

but there were billions

of other galaxies in

the universe as well.

But more surprisingly,

it was found that they were

rushing away

from one another

at enormous speeds.

This was discovered

by means of the Redshift

that occurs in the

spectrum of the light

due to the Doppler shift

when things are

moving away from us.

I'm using this particular

machine to measure

the Redshift of the galaxy.

This is the galaxy and

this is the spectrum

of the galaxy

under the nearby object

which has no Redshift at all.

When I change the magnification,

here is a spectral line

due to sodium.

And in the distant galaxy,

the spectrum line

is shifted towards the red

and from the separation

of the two lines,

one can tell that, roughly,

the Redshift is about

7000 kilometers per second.

This is one of the most

important kinds of

measurements that

astronomers make.

We often make

Redshift measurements.

It was first discovered

about 50 years ago,

and this led to the idea

of the expanding universe.

Later, in 1965,

a radio telescope

in New Jersey

revealed that

the whole universe,

even the apparently

empty parts of the sky,

were aglow with radio emission.

This is apparently left over

from the birth of

the universe.

It's this particular

discovery that makes

the Big Bang theory

the dominant theory

of cosmology at the

present time.

They represented

the expanding Einsteinian

universe

by a balloon studded

with galaxies.

They told me that it

served as a note

of the entire universe

with its space curving

right back on itself

because of the gravity

of all its contents.

And they induced

a cooperative Texan

bug to travel in it.

In sympathy with

that cosmic bug,

my mind voyaged

among the galaxies.

I couldn't really

visualize the overall warping

of cosmic space. Who can?

But I sensed that gravity

might indeed close up

the universe,

so that if I traveled

far enough,

I should find myself

coming full circle

back to my starting point.

The bug has

nowhere to go but around.

There's no end.

Nowhere at end to the universe.

It's closed universe

but unbounded universe.

Einstein's picture was

the universe is closed.

At least that's what he

wrote in the last edition

of his book

published in the year

of his death, 1955.

Today, of course,

we don't really know

how the evidence is.

Whether there's enough matter

to curve the universe

up into closure.

But to predict, as Einstein did,

the expansion of the universe,

and to predict it correctly,

and to predict it against

all expectation...

So fantastic a thing...

To my idea,

is the greatest prediction

that mankind has ever made.

And to my mind, gives us

more faith than anything

that we could have,

that some day we'll find

how the universe itself

came into being.

I think it's quite right to

have celebrated Einstein

out here on the far

frontier of Texas.

Because not only is it

the site of a major

observatory...

And observatories

are going to be

where Einstein's theories

will have to be tested

in the distant future...

But also, because we have

all around us still,

the great frontier,

the American West.

And this symbolizes, in a way,

Einstein's general relativity

which is at the far frontier

of the human mind.

The most beautiful thing

that we can experience

is the mysterious.

It's the only source of

true art and science.

And he to whom

this emotion is a stranger,

he who can no longer

pause in wonder

or stand rapt in awe,

well, he's already half dead.

His eyes are shut.

It was Einstein's passion

to understand the universe.

For him, that understanding

was the only real power,

and he did more to create it

than any other man

who's ever lived.

Well, that's a very large claim,

and I'm sure you're right,

but would you agree

with that, Wall?

Yes. Astronomers use

Einstein's ideas

all the time,

often without remembering

who thought of them.

It's the ultimate distinction

in science to be part of

the furniture, like Newton.

You ask me if

one can eventually express

everything in scientific terms.

Yes, it's possible,

but it is useless.

It is as though

one were to reproduce

Beethoven's Ninth Symphony

in the shape of an

air pressure curve.

I propose a toast

to Albert Einstein.

One of our greatest heroes.

Musicians have

Mozart, Beethoven.

We have Newton and Einstein.

And it's appropriate

that most of our talk

has been about his physics,

but we shouldn't forget

the other side,

Albert Einstein the folk hero.

Though widely honored,

he was a simple man

who spurned

and shunned wealth,

power and status.

A refugee on the

run from Hitler,

he was a dignified

and gentle symbol

of scientific inspiration

that was a great

particular inspiration

for young refugees

and immigrants

interested in science.

The reputed grandfather

of the atom bomb,

he was the moral leader

of the efforts

to bring that dangerous and

deadly application of E=mc2

under international control.

I propose a toast

to the memory of

Albert Einstein.

Hear, Hear.

To Albert Einstein.

The most daring

proposition in relativity

is that the laws of nature

must remain the same

at all places and

at all times,

even in galaxies so far away

that their light has traveled

for thousands of millions

of years to reach us.

If so, Albert Einstein's

own laws of nature,

conceived with pen and

paper on the planet Earth,

hold good everywhere.

"What really

interests me is whether

God had any choice"

"in the creation

of the world."