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A BRIEF HISTORY OF TIME

Which came first?

The chicken or the egg?

Did the Universe have a beginning?

And if so, what happened before then?

Where does the Universe come from?

And where is it going?

Luck.

Luck, well

We have been very lucky.

I mean, my family, and
Stephen, everybody

We had a few disasters, but
the point is that we have survived

Everybody has disasters, and yet
some people disappears

and they're never seen again.

Flybombs were very alarming

Seeking, buzzing over,
and then they would cut out.

And when you heard the bang,
you knew it wasn't you,

so you went back to your meal,
or whatever.

But one did fall quite close to
our house.

and it blew the back windows out

so the glass was sticking dagger points
out of the opposite wall.

When Stephen was born,

we decided he'd better
be born in Oxford.

So while I was staying
in the hospital.

I went to Blackwells,
in Oxford,

and I bought

an astronomical atlas.

One of my sisters-in-law
said:

"This is a very prophetic thing
for you to have done."

How real is time?

Will it ever come to an end?

Where does the difference between
the past and the future come from?

Why do we remember the past
but not the future?

I can remember that day when
we travelled through London

and the black-out was over.

And the trains, instead
of being shut in

by blinds, so you just
travelled in a train.

We were coming over
one of the bridges

and all lights, well, such lights
as were left

were only in London.

but it was also a completely
starry night

You could see the might whole
against it.

I remember we all used to lie
on the grass,

looking staight up through a telescope

and seeing the wonders of the stars.

Stephen always had a strong
sense of wonder

and I could see that the stars would
draw him,

and further than the stars.

I was born exactly 300 years
after the death of Galileo.

I estimate that about 200 000

other babies were also
born that day.

I don't know whether any of them

was later interested
in astronomy.

My first memory is about
pushing a rather antiquated

carriage built[?] pram

along North Road,

with Stephen and Mary in it, sort of

looking very large, because they had
large heads

and pink cheeks, and they were
very noticeable.

They all looked diffrent from
ordinary people.

I can remember visiting the
Hawking home

several times.

It was the sort of place where,
if you were invited to stay to supper,

you might be allowed to have
your conversation with Stephen...

but the rest of the family would be
sitting at the table reading a book.

A behaviour which is not really approved
over my circle,

but which is tolereated from the
Hawkings because they were recognised to be

very excentric,

highly intelligent, very clever
people,

but still... a bit... odd.

My impression of the Hawking family
was that they were all like that,

except for Stephen,

who seemed to be the only
normal member of the family.

Stephen used to reckon he knew,
I think it was,

11 ways of getting into the
house.

But I could only find 10 of them.

I'm not sure what the other way was.

On the north side of the house was
bicycle shad

had a door at the front and a door
at the back.

Above that,

there was a window into the
L-shaped room.

And at the front you could
get sort of round corner
onto the roof

And from that level you could get
onto the main roof.

I think one of the ways that Stephen
could get in was

on the main roof.

I must say he was a much better
climber than I was.

I still don't know what
the 11th one was!

Before the 20th century,

it was thought that the Universe
had existed forever,

or had been created at some time
in the past

more or less as we observe it
today.

People found comfort

in the thought that even though
they may grow older and die,

the Universe was eternal and unchanging.

I gave up playing games
with Stephen

when he was ill that time about...
when he was about 12.

Becouse he started taking games terribly
seriously.

We had Monopoly.

And...

first of all the Monoply board
sprang

railways going across it...

tried to add complications.

And then Monopoly just wasn't
adaptable enough.

But he ended up with a fearful game
called 'Dynasty'

which, as far as I can make out,
for I say, I never played it,

went on forever, because there
was no way of ending it!

It was almost a substitute for
living as far as I could make out,

It took hours, and hours,
and hours.

I thought it was a perfectly terrible game.

I couldn't imagine anyone getting
taken up with that.

But Stephen always had a very
complicated mind,

and I felt as much as anything

it was the complication of it
that appealed to him.

When I was in high school,

I learned that light from distant
galaxies

was shifted at the red.

This meant that they were
moving away from us

and that the Universe
was expanding.

But I didn't believe it.

A static Universe seemed
much more natural.

It could have existed, and could
continue to exist forever.

We were discussing the possibility
of the spontaneous generation of life,

and I think that Stephen
made a remark

which indicated not only that he
thought of this, but he did even also

come across some calculations

as to how long it might take.

At that time I think I made a commen
to one of my friends, John McLennahan:

"I think that Stephen will turn out
to be unusually capable."

I didn't [say it] in quite
these words

but I made one such remark to him

and he disagreed.

And so we made a bet on the subject.

In a childish way we bet

a bag of sweets on the issue.

And instantly I reckon that my
bet has come correct

and I think I'm entitled to payment

which is not yet been made.

The expansion of the Universe

suggested a possibility
that the Universe had a beginning

at some time in the past.

The point at which the Universe
may have started out

became known as the Big Bang.

The first year he was at
St. Albans school,

he came, I think, third
from the bottom.

So I said: "Well, Stephen,

"do you really have to be as
far down as that?"

And he said: "Well,"

"lot of other people didn't do
much better."

He was quite unconcerned.

Somehow he was always recognized
as being very bright

and in fact they gave him
the Divinity Prize one year.

That was not surprising as his father
used to reach him Bible stories

from very early age

and he knew them all very well

and he was quite well versed in religious
things although

I don't think he makes a very great
deal of practice of it now.

Everyone used to argue theology.

That's a good safe subject.

You don't need any fact, sort of,

or distracting things like that.

If you're going for arguing,

you know, debating, you can quite
happily debate about anything...

including...

theology and the existence of,
or otherwise, of God.

And then someone gets bored, or

Journey Into Space comes on
or something like that

the argument breaks up.

In an unhcnaging Universe,

one can imagine that God
created the Universe

at literally any time
in the past.

On the other hand, if the Universe
is expanding

there are maybe physical
reasons

why there had to be a beginning.

An expanding Universe does not
preclude a creator...

but it does place limits on when
he might have carried out his job.

When the family went to India,

it was arranged that Stephen to
come and live with us for a year.

He decided it would
be nice that he should have

Scottish dancing in the evening.

Now mind you, this was quite an
ordinary house,

but we had rather a lot of room
and a large hall,

and so we bought

some records, and

a book about what to do,

and Stephen took charge.

And he insisted to put on a jacket
and a tie.

And then he was the master
of the proceedings.

And Stephen took it very
seriously

But then he liked dancing, you see.

There were 4 physicists in my year.

Gordon Berry,

Richard Bryath,

Stephen

myself.

I first remember Stephen

on the occasion when Gordon and I
went up after dinner to his room,

to try to find him.

And Stephen was up there

with a crate of beer,

slowly drinking his way through it.

He was only 17,

he couldn't legally go into a pub.

He did come at Oxford ridiculously
early.

We used to have what we called
a "gathering net".

We used to organize that at beer
parties and various things like that

to gather under this cover as many
freshman as we could get, you see

get them to join the boat club.

And that's how we collected
him, you see.

But the question, always,
with Stephen, was

"Should we make him the cox
of the first 8,"

"or the second 8?", you see?

Well, coxes can be adventurous.

But some coxes can be very steady
people, you see.

He was rather an adventurous type.

You never knew could what he was going to do
when he went out with the crew.

I think he used to bring his work there
with him into the boat sometimes

Some thinking here was going on...
Different levels.

We were asked to read a chapter,
chapter 10

in a book about
electricity and magntism

by Bleaney & Bleaney,

an unlikely combination of a
husband and wife team.

And at the end of that chapter there
were 13 questions,

all of them final honours questions.

I discovered very rapidly that I
couldn't do any of them.

Richard and I worked together
for the week,

and we managed to do one a half
questions,

which we felt very proud of.

Gordon refused all assistance

and managed to do one all by
himself.

Stephen, as always, hadn't even
started.

But the next morning, he went up to his
rooms at 9 o'clock,

and we came back about 12, maybe
five past 12,

and down came Stephen, we were in the
college gateway, the lodge,

"Ah, Hawking," I said, "how many
have you managed to do then?"

"Well," he said:

"I've only had time to the first 10."

I think at that point we realised

that it's not just we weren't
in the same street,

we weren't on the same planet.

I once calculated that I did
about 1 000 hours work

in the 3 years I was at Oxford.

An average of one hour a day.

I'm not proud of this lack of work.

I'm just describing my
attitude at the time.

An attitude that nothing
was worth making an effort for.

He used to produce his work
every week for tutorial

and, as he never kept any notes,
or papers or that sort of things,

on leaving my room he would normally
throw it in my wastepaper basket.

And when he was with other
undergraduates at the tutorial

and they saw this happen

they were absolutely horrified, 'cause
they thought

he did this work in probably half
an hour,

if they could have done it in a year

they wouldn't have thrown it in the
wastepaper basket, they would have
put in a frame up on their walls.

Because of my lack of work,

I had planned to get through
the final exam

by doing problems in
Theoretical Physics,

and avoiding any questions that
required factual knowledge.

I didn't do very well.

I was on the borderline between a
first and a second class degree.

And I had to be interviewed
to determine which I should get.

They asked me about my
future plans.

I replied

if they gave me a first,
I would go to Cambridge;

if only got a second,

I would stay in Oxford.

They gave me a first.

I drove Stephen and his
young brother

at Woburn Park.

And he climbed a tree; he was testing
himself out, I think, I didn't realize.

And he did manage to climb the tree,
and to go along a branch of it

and to get himself down.

I think he began to notice that his hands

were less useful than they had been,

but he didn't tell us.

Uni has this square staircases

which are round but they're
square.

He was just coming down from
one of the rooms

Steve actually fell on the stairs

coming down the stairs and, he kind of
bounced all the way down to the bottom.

I don't know if he loss conciousness,

but he lost his memory.

We took him to either my room
or someone's room.

The first question of course was:
"Who am I?"

and we told him: "You're
Steve Hawking."

and a minute later
or right away

He would ask: "Who am I?"

"Euh.. Steve Hawking."

And then after a couple of minutes
he remembered he was Steve Hawking.

and we tell him: "Do you remember
going down to the bar and having a drink"

"on Sunday night?"

Or: "Do you remember rowing,
coxing on the river on Monday?"

And his memory came back
gradually, until he could remember
the previous days events

and then the previous hour.

By the end of the 2 hours
he could remember everything.

The question was: "Well maybe,
you know, you lost some of your mind
bacause of this"

And so, Steve decided: "Well, I'll take
the Mensa test."

We said: "Of course you'll get
into Mensa."

But he came back delighted

that he was able to get into Mensa,
absolutely delighted.

I felt that there were 2 areas
of Theoretical Physics

I might study at Cambridge

One was Cosmology, the study of
the very large.

the other was Elementary Particles,

the study of the very small.

However, I thought that
elementary particles

were less attractive

because there was no proper
theory.

All they could do was arrange the
particles in families,

like in botany.

In Cosmology, on the other hand,
there was a well defined theory:

Einstein's General Theory of
Relativity.

It was very a very cold year

and the ice on Veralamian pond
was, it was all frozen then.

and we all went skating.

And Stephen managed to skate
fairly well.

But then, he and I were closed
together,

he wasn't skating in a very advanced
way, but nor was I as it comes to,

and he fell

and he couldn't get up.

So I took him to caf� to warm up

and he told me then all about it

and it was diagnosed.

I've insisted on going to see his doctor

because, it seemed to me,
however long you're going to live

there's probably something
someone can do about it.

at least anyhow to make things
easier for people.

And, I won't mention the doctor's name,

but I got to see him at the
London Clinic.

And he was rather surprised that I should
bother to come down to see him.

I mean afer all I was only
Stephen's mother!

He was quite nice, I mean, he agreed
to see me in a rather grand way.

And he said: "Yes, it's all
very sad, I mean,

a brilliant young man, cut off in
the prime of his."

But of course I said:
"What can we do?"

"What can we do to, sort of...
Can we give him... can we get
physiotherapy?"

"Can we get anything like that
that will help in any way?"

He said: "Well, actually no,"

"there's nothing to it", more or less.
That's it.

Shortly after my 21st
birthday,

I went into hospital for
tests.

They took a muscle sample from
my arm,

stuck electrodes into me,

and injected some radio-opaque fluid
into my spine

and watched it going up and down with
X-rays

as they tilted the bed.

I was diagnosed as having ALS

Amyotrophic lateral sclerosis...

or motor-neuron disease,
as it is also known.

The doctors offered no cure

and gave me 2 and a half years
to live.

I went into the graduates common
room and

looking really for someone to have
lunch with

and there was nobody around that
I particularly wished to have lunch
with

and then learned about Stephen
walk through the door.

don't know what he was doing in
Oxford either, I've certainly forgotten that.

And so...

Stephen generously went off
to buy the drinks

and brought them over, put them
down on the table,

and as he put his pint of beer
down, he spewed it.

And I sort of said, genially:

"Ah, haven't you been drinking
at this time of day?"

and he then told me that he'd been
in Edinburgh for 3 weeks

and they'd done a whole series
of tests

and they decided what was wrong
with him.

And he told me very straight and
flat

that he was gradually going to
lose the use of all of his body.

And that eventually

only his heart and his lungs would
still be operating,

and his brain.

And that they told him that,

eventually, he would essentially have
the body of a cabbage.

but his mind would still be
in perfect working order,

and he would be unable to communicate
with the rest of the world.

My dreams at that time
were rather disturbed.

Before my condition had
been diagnosed,

I had been very bored with life.

There had not seemed to be
anything worth doing.

But shortly after I came
out of hospital,

I dreamt that I was going
to be executed.

I suddenly realized that there
were lots of worthwile things

I could do

if I were retrieved.

I knew perfectly well
that he had no faith.

And to me that made it more difficult,

because you must ask yourself:
"Why me? Why this?"

"Why now?"

But he just totally,

flatly, accepted

that this was what was going
to happen to him.

And as far as I can gather at that
point he started to do some work.

At first, there di not seem to be
much time in working at my research,

because I didn't expect to live long
enough

to finish my Ph.D.

However, as time went by,

the disease seemed to
slow down.

I began to understand
General Relativity

and make progress with my work.

But what really made a difference
was

I got engaged to a girl called
Jane Wilde.

This gave me something
to live for,

but it also meant that I had
to get a job

if we were to get married.

Stephen was already ill,
Jane knew it.

And it was another instance of
Stephen's luck.

Meeting the right person at the
right time,

because Jane...

Stephen was very very badly depressed.

And...

he wasn't really very much inclined to
go on with his work, I mean,

you're told you got 2 and a half years,
what can you do in that time?

But meeting Jane, really put him
on his metal,

And he started to work.

I wanted to understand
how the Universe began.

Einstein's theory of General
Relativity

showed that the Universe was
expanding.

But there was no answer to the
crucial question:

"Must there have been a Big Bang?"

"A beginning to time?"

Then, in my 3rd year at Cambridge

Roger Penrose made his
discovery about the death of stars.

I remember talking to this
friend, Ivor Robinson,

and we were having some very
animated conversation.

and then we had to cross the road,

and as we crossed the road of course
the conversation stopped, and then
we got to the other side, well evidently
I had some idea in crossing the road

but then the conversation started up

and it got completely blotted
out of my mind.

And it was only later, after my
friends had gone home.

and I began

having this strange feeling
of [?]elation, it feeling wonderful.

And I couldn't figure out why on earth
I should feel like that,

so I went back over the day, thinking all possible things
which might have contributed to such a feeling,

and then gradually I unearthed

this thought which I had while
crossing the street.

Penrose announced this
result, that

when stars collapse indefinetly

they will become singular

as long as certain very broad
conditions are satisfied

that every body would have
regarded as reasonable.

and I remember Stephen Hawking,

who was then approaching his
3rd year as a research student, saying:

"What, very interesting results,"

"I wonder wehter they could be adapted"

"to understand the origin of the Universe."

and what he had in mind, you see,

was that if, just mentally,
you reverse the sense of time,

you can think of the expanding universe

as a collapsing system, it's a bit like a giant,
a very giant star collapsing

Roger Penrose proved
that a dying star

collapsing under its own gravity

eventually shrinks to a singluarity,

a point of infinite density
and zero size.

I realized that if I reversed
the direction of time,

so that the collapse
become an expansion,

I could prove

that the Universe had a beginning.

But my proof,

based on Einstein's theory
of General Relativity,

also showed that
we cannot understand

how the universe began,

because it showed
that all scientific theories,

incuding General Relativity itself,

break down
at the beginning of the Universe.

We had this meeting at the Institute
of Space Physics in New York.

I said: "Before we reach
a final conclusion,"

"we ough to throw into the pot"

"still another object:"

"a gravitationally completely
collapsed object."

Well, after you've used the phrase:

"a gravitationally completely
collapsed object"

ten times,

you conclude you've get to get
a better name,

so that's when I switched
to the word 'black hole'.

The word 'black hole', which
John Miller coined, suddenly caught on.

Everybody adopted it

and from then on people around the world,
in Moscow,

in America, in England and elsewhere,

could know they were speaking
about the same thing.

And not only that, but suddenly
the hole range of concept's

got throught to the general public,
and even science fiction writers

all of a sudden could talk about it.

Tonight, my friends,

We stand on the break
of a feat unparalleled in space exploration.

If the data in my returning probe ship
matches my computerized calculations,

I will travel where no man
has dared to go.

Into the black hole?

In...

Through...

And behind!

Why that's crazy!

Ah! Impossible!

As a massive star contracts,

its gravity becomes so strong

that light can no longer escape.

The region from which
nothing can escape

is called a 'black hole'

and its boundary is called
the 'event horizon'.

One might say
of the event horixon

what Dante said
of the entrance to Hell:

"Abandon all hope
ye who eneter here."

I was once asked
to actually be an adjudicator

on an essay of which
the subject was:

"How to fall into a black hole
and live"

Now, the problem I had was

that I wouldn't know how
to give out the prize,

because if I said: "Well, that
looks like a really good essay",

the only real way
of showing that this was right

was to actually follow it,
to do the experiment of fall in,

but then having fallen in,

also I would assume
taking the person who wrote the essay with you,

the question would be:
"How do you tell the rest of the world?"

Do you take the prize in with you

that you'd give to him, and what
do they do with it when do when get to the center?

Beleive me

I've benn waiting a long time
for someone like you

to record this moment.

Thank you, doctor.

Then, I'm ready.

Ready to embark

on man's greatest journey.

Certainly his riskiest.

The risk is incidental

compared to the possibility to possess

the great truth of the unknown.

There,

long cherished laws of nature
simply do not apply.

They vanish.

And life?

Life?

Life forever.

If you were watching
an anoustronaut

fool hardly enough
to jump into a black hole,

at some time on his watch,
say 12 o'clock,

he will cross
the event horizon

and enter the black hole.

But no matter how long you waited,

you would never see the astronaut's
watch reach 12 o'clock.

Instead, each second
on the watch

would appear to take
longer and longer

until the last second before midnight
would take forever.

Thus, by jumping
into a black hole,

one could ensure
that one's image lasted forever.

But the picture
would fade very rapidly

and grow so dim
that no one could see it.

When somebody disappears
into the black hole

as seen from the outside, you...
it looks like time actually slows down.

and the person becomes...
who's moving or at least he thinks
he's moving

and talking in his spaceship
at a normal rate,

seems to slow down
and ends up by being frozen

in a particular position

as seen from somebody watching
from the outside,

and as seen from the outside
you never see what happens after that.

The astronout
wouldn't notice anything special

when his watch
reached midnight

and he crossed
the event horizon

into the black hole.

Until of course he approached
the singularity

and was crushed into spaghetti.

One can fall though
this event horizon

without feeling anything,
without noticing it.

After about a week of falling,
one begins to feel

a pinch, and one extends longer and longer
and gets slightly thinner

and of course one begins
to get squeezed,

until one gets very long
and very thin

and rather nasty.

By the end of two weeks
one's fallen right into the center

and one is of course dead.

Before you lose sight
of the outer world,

you would see things happening

and you would see them
at a greater rate

so that it would look like
a firework display.

And the frustration would be that,
although you would be able

to see everything that happens
in the future,

it would be going so fast
from the scientific point of view,

you would have no time to analyze it,

you wouldn't be able to take it in.

And eventually things
would be going so fast

and it would be so explosive that
you yourself

would be destroyed by the explosion
and that would be the end.

But it would be a very exciting way
to end one's life.

It would be the way I would choose
if I had the choice.

In the long hisroty
of the Universe,

many stars must have
burned up their nucelar fuel

and collapsed in on themselves.

The number of black holes
may be greater

than the number of visibile stars,

which totals about
a hundred thousand million

in our galaxy alone.

We also have evidence

that there is a very large black hole

at the centre of our own galaxy.

Friends ask me:

"Well, if a black hole is black,
how can you see it?"

And i say: "Have you have you ever
been to a ball?"

"Have you ever watched the young man
dressed in their evening tuxedos"

"and the girls in their white dresses,
whirling around, held in each other's arms?"

"And the lights turn low,
and all you can see is the girls."

Well, the girl is the ordinary star

and the boy is the black hole.

You can't see the black hole
any more that you can see the boy,

but the girl going around

gives you convincing evidence
there must be something there,

holding her in orbit.

One evening, shortly after
the birth of my daughter, Lucy,

I started thinking about black holes
as I was getting into bed.

My disability made this
a rather slow process,

so I had plenty of time.

Suddenly, I realized

that the area
of the event horizon

must always increase
with time.

The increase in the area
of the event horizon

was reminiscent of a quantity
called entropy,

which measures the degree of
disorder of a system.

It is a matter of common experience

that disorder tends to
increase with time

if things are left at themselves.

Jacob Bekenstein came in
at the office one day.

"Jakob," I said,
"it always troubles me:"

"when I put a hot tea cup next
to a cold tea cup, I've increased,"

"by letting heat flow
from one to the other,"

"the amount of disorder
in the Universe."

"But Jakob, if a black hole
swirls by,"

"and I drop both tea cups
into this,"

"I can seal the evidence
of my crime, have I not?"

Bekenstein's a man
of great integrity

and he looked troubled,
and he came back to me later

and he said: "No, you have not
concealed the evidence of your crime."

"The black hole records
what's happened to you."

Stephen Hawking read the paper

in which Bekenstein
announced his result

and thought it was preposterous

and he decided to prove
that he was wrong.

My dicoveries led
Jacob Bekenstein

to suggest that
the area of the event horizon

actually was
the entropy of the black hole.

But there was one fatal flaw
in Bekenstein's idea:

if black holes have
an entropy,

they ought to have
a temperature.

And if they have a temperature,
they ought to give off radiation.

But how could they give off radiation

if nothing can escape
from a black hole?

As it turned out, Bekenstein
was basically correct,

thought in a manner far
more surprising

than he, or anyone else,
had expected.

As he gradually lost
the use of his hands,

he had to start developing...

carefully chosing
research projects

that could be tackled and solved

through geometrical arguments
that he could do pictorially in his head.

and he developed a very powerful
set of tools

that noboby else really had

so in some sense,
when you lose one set of tools

you may develop other tools,

but to get new tools on a minimal to
different kind of problems in your tools

and if you're the only master
in the world of this new tools,

that means certain kinds of problems

you can solve and nobody else can.

My work up to 1973
was in General Relativity

and was summurized in a book
which I wrote with George Ellis

called "The large scale structure
of space-time".

Even then, it was difficult for me
to write things down.

So I tended to think in pictures
and diagrams
Aussi, �tais-je enclin � penser
en images et en diagrammes

that I could
visualize in my head.

I remember visiting Stephen
and Jane

at their home in Cambrigde.

After supper in the evening

when it was time for Stephen
to go to bed

Jane instisted and Stephen acquiesced,

I guess this was standard,
that Stephen make his way up.

I forgot whether there's one flight of stairs
or two flight of stairs, alone

and this was appearen
that he can no longer walk.

the way he got up the stairs was
he grabbed hold of the pillars
that support the banister

and pulled him up with the strenght of his own,
pulled himself up the stairs by the
strenght of his own arms,

dragging himself up
from the ground floor up to the second storey

in a long, arduous effort.

Jane explained that this
was an important part of his physical therapy

to maintain his coordination

and strenght as long as possible.

at first, it was sort of hard
renting[?] to watch

what appeared to be the agony
of pulling up the starirs

until I understood it was just part of life

pulling himself up the stairs like that.

General Relativity is
what is called a classical theory.

It predicts

a single definite path
for each particle.

But according to
quantum mechanics,

there is an element of chance
or uncertainty.

A particle does not have
just a single path through space and time.

Instead, there is
an uncertainty principle

according to which both the exact position
and velocity of the particle

can never be known.

I began investigating

the effect of quantum mechanics might have

on particles near a black hole.

I found

that particles could escapoe
from a black hole,

that black holes
are not completely black.

At first, I didn't believe it.

But when I ridid the calculations,
I couldn't get the effect to go away.

I met martin Reese
and he was shaking with excitement.

And he said: "Have you heard,
have you heard!"

"What Stephen has discovered? Everything
is different! everything is changed!"

I was still unsure
of my discovery

so I only told
a few colleagues.

But word soon spread.

Roger Penrose phoned up
on my birthday.

He was very excited
and went on so long

that my birthday dinner
got quite cold.

It was a great pity

because it was goose,
which I'm very fond of.

To me it's a miracle, because
it's a complicated and messy calculation.

we can now do these things
very much better

and it's more transparent
what happens.

But out of this messy calculation,
he showed that black holes

aren't black.
With this quanto-mechanical effect

which was a residual radiation.

Stephen came to a meeting

and people were flabbergasted.

I remember someone getting up and saying:
"You must be wrong Stephen."

"I don't believe a word of it!"

I once said that I was unhappy

with the explanation given in terms of
negative energy particles being created.

But I feel this is part
of the controversy of science.

You must have the give and take.

And I'm delighted to be able
to be part of that.

I mean, it's what makes it fun.

You know, if you all sat down
and said: "Oh, lovely!"

when you do have niggling
questions in your mind

that's not doing a good service
to science.

But I was not antagonistic to it
in any way,

except for that one time
when I questioned.

I finally conviced myself

that black holes radiated

when I found a mechanism
through whcih this could happen.

According to quantum mechanics,

space is filled
with virtual particles

and anti-particles

that are constantly
materializing in pairs,

separating,
coming together again

and annihilating
each other.

In the presence of a black hole,

one member of a pair
of virtual particles

may fall into the hole,

leaving the other member without
a partner whith which to annihilate.

The forsaken particle appears
to be radiation

emitted bu the black hole.

And so, black holes
are not eternal.

They evaporate away
at an increasing rate

until they vanish
in a gigantic explosion.

Quantum mechanics has allowed
particles and radiation

to escape from
the ultimate prison:

a black hole.

Einstein never accepted
quantum mechanics

because of its element
of chance and uncertainty.

He said:
"God does not play dice".

It seems that Einstein
was doubly wrong.

The quantum effects
of black holes

suggests that not only
does God play dice,

he sometimes throw them
where they cannot be seen.

He says himself that

he wouldn't have got where he is
if he hadn't been ill.

And I think that's quite possible,
because it's like Johnson said, you know:

"Knowledge to be hanged in the morning
concentrates the mind wonderfully".

And he has concentrated on this
in a way

that I don't think
he would have done

because he always took a great
interest in a lot of things in life

and I don't know if he would have
applied himself in quite the same way

if he'd been able to get around as is.

So in a way...

No, I can't think anyone's lucky
of having an illness like that, even still,

but it's bad less luck for him
that it would be for some people,
if you see what I mean,

because he can so much
live in his head.

When I lived with the Hawking family
I would usually get up around

7h15 or 7h30, and

take a shower and then
read my bible some in the morning and pray.

And then I would go down at 8h15
to get Stephen up.

And then at breakfast I would often
tell him what I'd been reading in the bible

hoping that, you know, maybe this
would eventually have some influence.

So then we would get into work
and usually we'd go and see

if there were any scientific papers
that people sent out and.

I did discover that despite
Hawking's great brains

he reads quite slowly.
I mean, I can read about twice as fast as him.

But of course, the point is
he would have to read to memory

because it would be very difficult
for him to go back and access the thing.

Wherheas I can skim the paper
rather quickly

and see if there was anything interesting in it and
if I wanted to work on it

I can pick the thing up and look at it.

Black hole radiation

has shown us that
gravitational collapse

is not as final
as we once thought.

If an astronaut falls
into a black hole,

he will be returned
to the rest of the Universe

in the form of radiation.

Thus, in a sense,

the astronaut will be recycled.

However, it would be
a poor sort of immortality

because any personal concept of time
would come to an end

as he is torn apart
inside a black hole.

All that would survive
would be his mass, or energy.

One year the Hawkings
took me along

when we went to a cottage
in Wales near the river Wye.

And this cottage was
up a hill

and there was a bit of a

paved, well, sidewalk
that went up to the cottage

which I had not been up.

And of course I wanted to do it
in the least number of trips that I could imagine,

so we put Stephen's batteries
under his chair, I mean

his wheelchair has space for batteries,
and put extra batteries under there, which we...

Stephen didn't realize he had...
that I put under there,

he didn't realize his chair
was as heavily laden as possible.

So Stephen was quite a bit ahead of me
and then he was turning the corner
to go on to...

around to his house,
but that was on a slope and...

So I looked up and I noticed

Stephen's wheelchair
was slowly tipping backward.

And of course that was about
10 meters away.

I tried to roll up there

but of course I wasn't able to get there
nearly rapidly enough

before he've toppled over backward
into the bushes.

And this was a bit
of a shocking sight,

to see this master of gravity getting
overcome by the weak gravitational force of Earth!

One of the worst things for me
would be having people there all the time,

never alone I reckon, really.

And yet he finds thigs funny

and he enjoys life and he goes
dashing about all over the place.

And I think this is tremendous,

that this is the sort of courage I haven't got,

that his father hadn't got.

And we cannot but admire it,

but I wonder
how on earth he got it, really!

There must have been 50 people there

and I was standing off
in a corner, sort of,

watching quietly
for a few minutes, relaxing.

And Stephen was not far from me.
Jane walked over to Stephen

and looked at him and he was
sitting with his head on his lap,

like only Stephen can put
his head in his lap,

and Jane said to Stephen:
"You look miserable Stephen!"

Sit up straight!"

"Some of your guests
don't understand"

"that you're sitting there thinking
about physics and having a wonderful time,"

"it looks like you're in pain.
Sit up straight and go talk to your guests."

In 1979, I was elected
Lucasian Professor of Mathematics.

This is the same chair
once held by Isaac Newton.

They a have a big book

which every university
teaching officer is supposed to sign.

After I had been Lucasian Professor
for about a year

they realized I had never signed.

So they brought the book
to my office

and I signed it
with some difficulty.

That was the last time
I signed my name.

My interest in the origin
and fate of the Universe

was reawakened
when I attended a conference

on cosmology in the Vatican.

Afterwards, we were granted
an audience with the pope.

He told us that it was all right to study
the evolution of the Universe

after the Big Bang,

but we should not inquire
into the Big Bang itself,

because that was
the moment of creation,

and therefore, the work of God.

I was glad that he did not know

the subject of the talk
I had just given:

the possibility that
the Universe had no beginning,

no moment of creation.

There were theories in the early 70s,
in fact the first type

of creation theories,

where the people concerned
started off with

a fixed external space and time which
for eternity was empty.

Then suddenly, for some unknown reason,
Universe nucleates

in a point and then Bang!
It blows apart.

But the trouble is that when
the space and time appear
in the classical theory

the actual point itself
is a singualr point in the mathematics.

Mathematics breaks down,

and so you cannot in fact use that
to give you a creation theory.

If one goes back in time,

one comes to
the Big Bang singularity,

where then laws of Physics
break down.

But there's another
direction of time

that one can go in,

which avoids the singularity.

This is called
the imaginary direction of time.

In imaginary time,

there need not be any sigularities

which form a beginning
or end to time.

When you come to imaginary time,
you have this rather peculiar possibility

of having a 'now', as it were,

not necessarily having a sort
of a chain of past moments.

If we start to lay out the moments
that run in backwards in time, as it were,

then for a long time
things work perfectly normally.

But then as you begin to get
further and furhter back towards

what would be the origin point
in a conventional real time picture

you'd find that
the nature of time changes,

that the imaginary component
becomes more and more prominent,

and in the end, what ought be a singular point
in the classical theory

just gets smoothed away
s'estompe

and you have this beautiful picture,
this bowls,

where the creation of the Universe

is pictured, as where we are now

in a smooth sort of bowl past
where there's no initial point,
just a sort of smooth shape.

So long as the Universe
had a beginning,

we could suppose
it had a Creator.

But if the Universe
is completely self-contained,

having no boudary or edge,

it would neither be created
nor destroyed,

it would simply be.

What place then, for a Creator?

What we can really say
is that the Universe is,

bacuse it is a self-consistent
mathematical structure.

There's no past because,
unlike the creation point scenario

there's nothing for it to

So to say it's created from nothing
is actually a bit of a misnomer,

it's a misleading use
of the word 'nothing'.

It's not just that there was empty space
in which the Universe appeared,

which you might call 'nothing',
there was really nothing at all

because there wasn't even
a creation event, you see.

The use of past tense in a verb
becomes inappropriate in these theories.

Unfortunately, tenses were set up

when people believed
in real time, of course,

and we don't yet have a linguistic form
to describe tenses in imaginary time.

The word 'time' was not
handed down from Heaven,

as a gift from On High.

The idea of 'time' is
a word inventend my men,

and if it has puzzlements connected with it,
whose fault is it?

It's our fault!

Where does the difference
between the past and the future come from?

The laws of science

do not distinguish
between the past and the future.

Yet, there is a big difference
between the past and future

in ordinary life.

You may see a cup of tea
fall off a table

and break into peaces
on the floor,

but you will never see
a cup gather together

and jump back on the table.

The increase of disorder
or entropy

is what distiguishes
the past from the future,

giving the direction to time.

He fell ill in Switzerland.

When he came back,
he was on a ventilator.

Because he was on a ventilator,
you've got a tube down you throat,

and therefore you can't speak,
just for that reason.

For that period, which
might have been a couple of months,

I spent probably one in two nights,
one in three nights, at the hospital,

because when he was in hospital

he couldn't communicate
with the nurses.

And it's not just like
being seriously ill,

but you're in a position where
the nurses

couldn't understand what
Stephen wanted.

If Stephen was unconfortable,
they couldn't tell why.

Before I caught pneumonia,

my speech had been getting
more slurred

so that only a few people
who knew me well

could understand me.

But at least
I could communicate.

I wrote scientific papers
by dictating to a secretary

and I gave seminars
through an interpreter.

And then, a tracheotomy
operation

removed my ability
to speak altogether.

After a long time,
well it seemed like along time,

somebody came up
with this brilliant gadget.

They didn't have it
in Cambridge hosptal,

they got it from
somewhere in London.

This was high technology:
how can you communicate
with a person with no voice?

It's plastic piece of Perspex,
about so big,

and you've got the letters of the alphabet
arranged like that and a hole in the middle.

You hold it up between you
and the other person

and they look at a letter,
and you can see of course
which letter they're looking at,

most of the time,
sometimes you can't quite be sure,

and so you get the patient
to spell out what they wanted, you know,

so each letter you have to look:
speak out the A,

and you say: "A?" You get it right.
It's like a guessing game.

Stephen wasn't going to accept
that he wasn't going to speak again

and he thought that he would be
giving in by trying to find

a method of communicating
without speech.

And I remember
I went to him one evening,

and this was the first time
that he asked

to be gotten out of bed
to use a computer.

Sometimes, they were sitting him up
so that he wasn't lying in the bed all the time,

as you do with a patient,

but this time, when I turned up,
he asked the nurse
could he be gotten out of bed

so he could use the computer,
and he did.

I remember the first thing he typed
in there, after saying 'hello',

-Stephen's always being
very polite about things like that-

was: "Will you help me
finish my book?"

A computer expert in California
heard of my plight

and sent me a computer program
called Equalizer.

This allowed me
to select words

from a series of menus
on a screen

by pressing a switch
in my hand.

These words could then
be sent to a speech synthesizer

attached to my wheelchair.

Much to my surprise,

I found I was able to communicate

much better than before.

When eventually
he went home from hospital,

and he was told he needed 24h nursing,

and everyone was saying:
"Well, how is he gonna go in and do work,"

"is he going to trail around
with a series of nurses after him
working in the office?"

And of course he did!

I mean, they talked originally
of him working at home,

which he wasn't happy with,

so after a period
of recuperation home

he just decided
to go back into the office,

and he made the trip
Il faisait donc le trajet

from his house to the office which is,
I don't know, half a mile, in his wheelchair,

And the nurses
were walking along with him.

And this is at the time when
he was still driving around

with a bag and a nasal drip[?].

Going into the department, working,
going back home.

I began to wonder

what would happen
when the Universe stopped expanding

and began to contract.

Would we see broken cups
gather themselves together off the floor

and jump back on to the table?

Would we be able
to remember tomorrow's prices

and make a fortune
off the stock market?

It seemed to me the Universe
had to return to a smooth and ordered state

when it recollapsed.

If this were so,
time would go backwards

when the Universe
began to collapse.

People in the contracting phase
would live their lives backwards,

they would die before they were born

and get younger
as the Universe got small again.

Eventually, they would
return to the womb.

He gave me
my first problem to do.

He asked me to look at
this mathematical problem

and ususally,
when he gives a problem,

he has a good idea
of what the answer should be.

And I went to look at it

and it took me a few months
to understand what was it about

and I came back and I said:
"Stephen I get this answer."

And he said to me: "No,
that is not what I expected."

I said: "Stephen that's what I get."

And so I went to the blackboard,
explained to him what it was.

He said: "Did you think about that
particular case?"

I said: "Oh no I didn't!"

So I went back

I calculated
what he talked to me about,

came back a few weeks after
and I said:

"Stephen, I don't get this thing.
I still get the same answer
I had originally."

So he said to me:
"No no no, this is not right,"

"did you think about that?"
"Oh no!"

"I'd forgotten about that particular case."

So I went back to the drawing board,

started calculating again.
And again, get the same answer!

I went back to see Stephen, and this
dragged on for about 2 or 3 months.

Finally he said to me: "Maybe,"

"one of you approximations
isn't valid."

So me and a collegue decided
to do this thing with computers,

and than this takes a lot of time
to write the programs

and to be sure
the program was correct...

We get the answer and it was
still the way that I said before and

not the way that Stephen has said,

so we went to see Stephen
and we said: "You see? Again!"

I had make a mistake.

I had been using too simple
a model of the Universe.

Time will not reverse direction

when the Universe
begins to contract.

People will continue to get older,

so it is no good waiting
until the universe recollapses

to return to our youth.

Einstein once
asked a question:

"How much choice did God have
in constructing the Universe?"

If my proposal that the universe
has no boundary is correct,

he had no freedom at all

to choose how
the Universe began.

He would only had had
a freedom

to choose the laws
the Universe obeyed.

This, however, may not have been
all that much of a choice.

They may be well be
only one unified theory

that allows for the existence
of structures as complicated

as human beings,

who can investigate
the laws of the Universe

and ask about
the nature of God.

I don't know how clear-cut
these experiments are,

but there are experiments that
have been done on, sort of,
timing of conciousness,

and they seem to lead
to a very odd picture

which doesn't even quite
make consistent sense.

Whether refinement of these experiments
might actually get rid
of this kind of anomaly

I'm not sure,

but it does look a little as though
there's something very odd about conciousness,

and somehow almost as though
future affects the past in some way

over a very tiny limited scale

but something maybe of the order
of a reasonable fraction of a second.

And there's no reason to believe

that one's conscious experience
shouldn't be part of somebody else's

at some other stage, I mean.

I don't if it's fair to say what happens
after one dies but you could...

it's a plausible picture

that you could be sombody else.

And that somebody else could be somebody
who lived in the past, not in the future.

If there's only one
possible unified theory

that is just a set of
rules and equations,

what is it that breathes fire
into the equations

and makes a Universe
for them to describe?

Why does the Universe go
to all the bother of existing?

Is the unified theory
so compelling

that it brings about
its own existence?

Or does it need a Creator?

And if so,
who created Him?

I think I would say
that the Universe has a purpose,

it's not somehow just there
by chance,

I mean, I think it's...

Some people, I think, take the view
that the Universe is just there

and it sort of rumbles along
and it just sort of computes,

we happen somehow by accident
and found ourselves in this thing.

But I don't think
that's a very fruitful

or helpful way
of looking at the Universe.

I think that there's
something much deeper about it.

In real time,
the time in which we live,

the Universe has two
possible destinies:

it may continue
to expand forever,

or it may recollapse
and come to an end at a Big Crunch.

It would be rather like
the big Bang,

but in reverse.

I now believe that the Universe
will come to an end at a Big Crunch.

I do, however,
have certain advantages

over many other prophets of doom:

whatever happens
10 billion years from now,

I don't expect to be around
to be proved wrong.

Of all the pictures that I know,

the simplest of any cosmology

is that in which the Universe
is closed,

has a finite lifetime,

and collapses with the same
kind of collapse

that a black hole does.

If it should turn out that indeed
the Universe is limited in its life,

how is that different
from the life of each one of us?

On the evening of Tuesday,
March 5th,

at about 10h45,

I was returning to my flat
in Pinehurst.

It was dark and raining.

I came up to Grange Road

and saw headlights approaching,

but judged that
they were far enough away

that I could cross safely.

The vehicle must have been
travelling very fast,

for when I got just past
the middle of the road,

my nurse screamed:
"Look out!"

I heard tires skidding

and my wheelchair was struck
a tremendous blow in the back.

I ended up in the road,

with my legs over the remains
of the wheelchair.

The accident destroyed
my wheelchair

and damaged my computer system

with which I communicate.

I required 13 stitches in my head,

but I was able to go back to work
several days later.

The memories I have
are very much,

kind of,

visual pictures
of what Stephen was.

I've seen Stephen
in certains situations.

He was always moving,

always.

He was hardly ever still.

It was the same thing
about his face and gestures,

which he used a great deal,
I should say.

But it's only memory.

I found some photographs recently

which reminded me
of the general look of everybody.

I must say Stephen looked
very much as he does now.

If one thinks of him like that.

He does believe very intensely

in almost infinite possibility
of the human mind.

You have to find out
what you can't know

before you know you can't,
don't you?

So I don't think that
thought should be restricted at all,

and there's... why shouldn't you
go on thinking about the unthinkable?

Somebody's got to start sometime.

I mean, think how many things were
unthinkable a century ago.

And yet people have thought them.

And often they seemed
quite impractical.

Not all things Stephen says

probably are to be taken
as Gospel.

truth is, he's a searcher,
he's looking for things

and if he is sometimes,
he probably talks nonsense as we all...

but the point is:

people must think.

People must go on thinking.

They must try to extend the boundaries
of knowledge,

and they don't sometimes even know
where to start.

We don't know where
the boundaries are, do we?

We don't know what
the taking off point is.

If we do discover
a complete theory of the Universe,

it should, in time,
be understandable,

in broad principle,
by everyone,

not just a few scientists.

Then we shall all,

phylosophers, scientists and just
ordinary people,

be able to take part
in the discussion

on why it is that we,
and the Universe, exist.

If we find the answer to that,

it would be the ultimate
triumph of human reason.

For then we would know

the mind of God.