A Brief History of Time (1991) Script

Which came first... the chicken or the egg?

Did the universe have a beginning... and if so, what happened before then?

Where did the universe come from... and where is it going?


Luck. Luck. Well... we have been very lucky...

I mean, my family and Stephen and everybody.

You have your disasters, but the point is that we have survived.

Everybody has disasters, and yet some people disappear... and are never seen again.

Flying bombs are very alarming.

They came 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 that the glass was sticking dagger points all 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 Blackwell's 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 the day... when we traveled through London and the blackout was over.

And the trains, instead of being shut in... by blinds so that you just traveled in a train... we were coming over one of the bridges... and all the lights... well, such lights as were left... were on in London, but it was also a completely starry night... and you could see the light. It was beautiful.

I remember we all used to lie on the grass, looking straight 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 of Isobel... 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 different from ordinary people.

I can remember visiting the Hawking home... oh, several times.

It was the sort of place where, if invited to stay to supper... you might, uh... be allowed to have your conversation with Stephen... but the rest of the family would be sitting... at the table reading a book... a behavior which was not really approved of in my circle... but which was tolerated from the Hawkings... because they were recognized to be... very eccentric, 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, and I could only find ten.

I'm not sure where the other way was.

On the north side of the house was a bicycle shed.

It 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 around the corner... onto the roof... and from that level... you could get onto the main roof.

I think one of the ways...

Stephen could get in was on the main roof.

As I say, he was a much better climber than I was.

I still didn'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 old and die... the universe was eternal and unchanging.

I gave up playing games with Stephen... oh, when he was ill that time when he was about 12... because he started taking games terribly seriously.

We had Monopoly... and first of all... the Monopoly board sprang railways going across it... to add to the complications... and then Monopoly just wasn't adaptable enough.

He ended up with a fearful game called Dynasty... which, as far as I can make out... 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 to 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'd thought of this... but he'd even also... come across some calculations... as to how long it might take.

At that time, I think I made a comment... to one of my friends, John McClenahan...

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

I don't think I put it in quite those words... but I made some such remark to him... and he disagreed.

And so we made a bet on the subject.

In our childish way, we bet... a bag of sweets on the issue.

And incidentally, I reckon that my bet has come correct... and I think I'm entitled to payment... which has not yet been made.

The expansion of the universe... suggested the 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.

I said, "Well, Stephen..." do you really have to be as far down as that?"

And he said, "Well..." a 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 because his father used to read him...

Bible stories from a 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 great deal of practice of it now.

Everybody used to argue theology.

That's a good, safe subject.

You don't need any facts or... distracting things like that.

If you go in for arguing... you know, debating... you can quite happily debate about anything... including theology... and the existence or otherwise of God.

And then someone gets bored... or Journey Into Space comes on, or something like that... and the argument breaks up.

In an unchanging 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 may be 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 should come and live with us for a year.

He decided it would be nice... that we should have...

Scottish dancing in the evening.

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 you 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 four physicists in my year...

Gordon Berry...

Richard Bryan...

Stephen... myself.

I first remember Stephen... on an 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'd gone up to Oxford ridiculously early.

We used to have what we called a gathering net.

We used to organize a beer party and various things like that... to gather all these... collar as many freshman as we could get... to 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 eight... or the second eight?"

Well, coxes can be adventurous... and some coxes can be very steady people.

He was rather an adventurous type.

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

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

His sort of thinking gear was going... on different levels.

We were asked to read chapter 10... in a book called Electricity and Magnetism... by Bleaney and Bleaney, an unlikely combination... a husband-and-wife team... and at the end of that chapter, there were 13 questions... all of them final honors 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 11/2 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 9:00... and we came back about 12:00, maybe five past 12:00... and down came Stephen, and 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 do the first ten."

I think at that point we realized 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 three years I was at Oxford... an average of an hour a day.

I am not proud of this lack of work.

I am 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 thing... 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've put it in a frame 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 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 I only got a second...

I would stay in Oxford.

They gave me a first.

I drove Stephen and his young brother... out to Woburn Park... and he climbed a tree.

He was testing himself out, I think. I didn't realize.

He did manage to climb a tree... and go along a branch of it and 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.

Univ has these square staircases... which are round but they're square.

It was just coming down from one of the rooms.

Steve actually fell on the stairs coming downstairs... and kind of bounced all the way down to the bottom.

I don't know if he lost consciousness, 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?"

We told him, "You're Steve Hawking."

Right away he would ask again, "Who am I?"

"Steve Hawking."

Then, after a couple of minutes, he remembered he was Steve Hawking.

Then we'd say, "Do you remember going down to the bar..." and having a drink on Sunday night?"

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

And his memory came back gradually... until he could remember the previous day's events, and then the previous hour... and by the end of the two hours, he could remember everything.

The question was, "Well, maybe you've lost... some of your mind because of this."

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

We said, "Of course you'll get in."

But he came back delighted he was able to get into Mensa.

Absolutely delighted.

I felt that there were two 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 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 a very cold year... and the ice on Verulamium Pond... it was frozen there... and we all went skating.

And Stephen managed to skate fairly well... but then, he and I were close together.

He wasn't skating in a very advanced way... but nor was I, if it comes to that.

He fell... and he couldn't get up.

So I took him to a café to warm up... and he told me then all about it.

And it was diagnosed.

I 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.

I won't mention the doctor's name... but I got to see him at the London Clinic.

He was rather surprised that I should bother to come 'round to see him.

After all, I was only Stephen's mother.

He was quite nice. He agreed to see me in a rather grand way.

And he said, "Yes, it's all very sad.

Brilliant young man cut off in the prime of his youth."

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

What can we do to sort of...

Can we get physiotherapy?

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

He said, "Well, actually, no."

There's nothing I can do, really. 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 radiopaque 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 could offer no cure... and gave me 21/2 years to live.

I went into the graduates' common room... looking, really, for someone to have lunch with.

There was nobody around that I particularly wished to have lunch with... and then Stephen walked through the door.

I don't know what he was doing at Oxford. I've certainly forgotten now.

And so Stephen generously went off... to buy the drinks... and brought them and put them on the table.

And as he put his pint of beer down... he spilled it.

I sort of said genially...

"Oh, heavens. Drinking at this time of day!"

He then told me he'd been in Addenbrooke's for three weeks... and they'd done a whole series of tests... and they'd decided... what was wrong with him.

And he told me very straight and flat... that he was gradually going to lose... the use of his body... that eventually... only his heart and his lungs... would still be operating, and his brain... and that they'd 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 there were a lot of worthwhile things...

I could do if I were reprieved.

I knew perfectly well that he had no faith... and... to me, that made it the 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.

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

At first, there did not seem much point... in working at my research... because I didn't expect to live long enough... to finish my PhD.

However, as time went by... the disease seemed to slow down.

I began to understand general relativity... and made progress with my work.

But what really made a difference was...

I had got engaged to a girl called Jane Wilde.

This gave me something to live for... but it also meant 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, you know... meeting the right person at the right time... because Stephen was very, very badly depressed... and he wasn't very much inclined to go on with his work.

He'd been told he's only got 21/2 years.

What can you do in that time?

But meeting Jane really put him on his mettle... 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 third 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 this animated conversation... and then we had to cross a road... and as we crossed the road, of course, the conversation stopped... and then we got to the other side.

Evidently, I had some idea crossing the road... but then the conversation started up, and it got completely blotted out of my mind.

It was only later, after my friend had gone home... and I began to have this strange feeling of elation... feeling wonderful.

I couldn't figure out why 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'd had while crossing the street.

Penrose announced this result... that when stars collapse indefinitely... they will become singular... as long as some very broad conditions are satisfied... that everybody would have regarded as reasonable.

And I remember Stephen Hawking, who was then approaching... his third year as a research student, saying...

"What very interesting results."

I wonder whether they could be adapted...

"to understanding 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 very giant star collapsing.

Roger Penrose proved... that a dying star, collapsing under its own gravity... eventually shrinks to a singularity... a point of infinite density and zero size.

I realized that if I reversed the direction of time... so that the collapse became 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... including 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 ought 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 got to get a better name.

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

The word "black hole," which John Wheeler 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 whole range of concepts got through to the general public... and even science-fiction writers all of a sudden... could talk about it.

Tonight, my friends... we stand on the brink of a feat unparalleled... in space exploration.

If the data on 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 beyond.

Why, that's crazy!

Ha! 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 horizon... what Dante said of the entrance to hell...

"Abandon all hope, ye who enter here."

I was once asked to actually... be an adjudicator... on an essay of which the subject was...

"How to fall through 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, "That looks like a good essay"... the only real way of showing this was right... was to actually follow it, to do the experiment and fall in.

But then, having fallen in...

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 that you give to them... and what do they do with it when they get to the center?

Believe me...

I've been 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 astronaut... foolhardy enough to jump into a black hole... at some time on his watch... say, 12:00... he would 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 12:00.

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.

As somebody disappears into a black hole... as seen from the outside, it looks as though... time actually slows down, and the person who's moving... at least he's thinking he's moving... he's perhaps talking in his spaceship at a normal rate... seems to slow down and ends up being frozen... in a particular position... as seen by somebody watching him from the outside.

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

The astronaut 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 through this event horizon... without feeling anything, without noticing it.

After about a week of falling, one begins to feel the 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 is, of course, dead.

Before you lose sight of the outer world... you would see things happening and see them at a greater rate... so that it would look like a firework display.

The frustration would be that, although you would be able to see... everything that happens in the future, it would be going so fast... that from a scientific point of view, you'd have no time to analyze it.

You wouldn't be able to take it in.

Eventually things would be going off 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 history of the universe... many stars must have burned up their nuclear fuel... and collapsed in on themselves.

The number of black holes may be greater... than the number of visible 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 center of our own galaxy.

Friends ask me, "Well, if a black hole is black... how can you see it?"

And I say, "Have you ever been to a ball?"

Have you ever watched the young men... dressed in their black evening tuxedos... and the girls in their white dresses... whirling around, held in each other's arms... and the lights turned 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 than 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 to think about black holes... as I was getting into bed.

My disability makes this rather a 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 very 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 to themselves.

Jacob Bekenstein came into the office one day.

"Jacob," I said...

"It always troubles me..." when I put a hot teacup next to a cold teacup.

I've increased, by letting heat flow from one to the other... the amount of disorder in the universe.

But Jacob, if a black hole swims by... and I drop both teacups into this...

"I've concealed 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 this result... thought it was preposterous... and decided to prove it was wrong.

My discoveries led Jacob Bekenstein to suggest... that the area of the event horizon... actually was the entropy of a 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... though 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 choosing 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 nobody else really had.

So in some sense, when you lose one set of tools... you may develop other tools, but the new tools... are amenable to different kinds of problems than the old tools.

And if you're the only master in the world of these 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 summarized in a book 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... that I could visualize in my head.


I remember visiting Stephen and Jane... at their home in Cambridge.

After supper in the evening... when it was time for Stephen to go to bed...

Jane insisted and Stephen acquiesced... I guess this was standard... that Stephen make his way up...

I've forgotten whether it was one flight of stairs or two... alone... and this was a period when he could 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 strength... pulled himself up the stairs with the strength of his own arms... dragging himself up... from the ground floor up to the second story... in a long, arduous effort.

Jane explained that... this was an important part of his physical therapy... to maintain his coordination... and strength as long as possible.

At first it was sort of heartrending... to watch what appeared to be the agony of pulling himself up the stairs... until I understood it's 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 a particle can never be known.

I began investigating... the effect quantum mechanics might have... on particles near a black hole.

I found that particles could escape... from a black hole... that black holes are not completely black.

At first I didn't believe it.

But when I redid the calculations...

I couldn't get the effect to go away.

I met Martin Rees, 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, 'cause 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 quantum mechanical effect.

There was a residual radiation.

Stephen came to a meeting... and people were flabbergasted.

I remember someone 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 a part of that.

That's what makes it fun.

If you all sat down and said, "Oh, lovely"... when you do have niggling questions in your mind... that's not doing a service to science.

But I was not antagonistic to it in any way... except for that one time when I questioned.

I finally convinced myself... that black holes radiate... when I found a mechanism through which this could happen.

According to quantum mechanics... space is filled with virtual particles... and antiparticles... 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... with which to annihilate.

The forsaken particle appears to be radiation... emitted by 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... suggest that not only does God play dice... he sometimes throws them... where they cannot be seen.

He says himself... that, uh... he wouldn't have got to where he is if he hadn't been ill.

And I think that's quite possible... because it's like Johnson said:

The knowledge you're to be hanged in the morning... concentrates the mind wonderfully.

And he has concentrated on this in a way...

I don't think he would have, because he took a great interest... in a lot of things in life... and I don't know that he'd have applied himself the same way... if he'd been able to get around as he used to do, so in a way...

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

But it's less bad luck for him than it would be for some people... because he can so much live in his head.

When I lived with the Hawking family, I would usually get up... around 7:15 or 7:30 and take a shower... and then read in my Bible some in the morning and pray... and then go down at 8:15 to get Stephen up.

And at breakfast I would often tell him what I'd been reading in the Bible... hoping that this would eventually have some influence.

So then we would go into work... and usually we'd go in and see if there were any scientific papers... that people sent out.

I did discover that despite Hawking's great brilliance, he does read quite slowly.

I could read about twice as fast as he.

But of course he would have to read to remember it... because it would be very difficult for him to go back and access the thing... whereas I could skim the paper rather quickly and see...

"Is there something interesting in this?"

If I wanted to work on it, I could 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 the 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 little 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 I could imagine... so we put Stephen's batteries under his chair... his wheelchair has space for batteries... and put extra batteries under there... which Stephen didn't realize that I'd put under there... so he didn't realize his wheelchair was as heavily laden.

Stephen got quite a bit ahead of me, and he was turning the corner... to go around to his house, but that was on a slope... so I looked up, and I noticed Stephen's wheelchair slowly tipping backward.

Of course, I was about ten meters away... and tried to run up there, but I was not able to get there... rapidly enough before he toppled backward into the bushes.

So it 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 couldn't bear that.

And yet he finds things funny... and he enjoys life and he goes dashing about all over the place... and I think this is tremendous.

But it's a sort of courage I haven't got... and his father hadn't got it, and we cannot but admire it... but 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 over there, not far from me.

Jane walked over to Stephen and looked at him.

He was sitting there with his head in 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 thinking about physics and having a wonderful time.

"It looks like you're in pain. Sit up 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 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 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... the first type of creation theories... where the people concerned started off with a fixed, external space and time... which for eternity was empty... and then suddenly, for some unknown reason, the universe nucleates... at a particular point and then, bang, it blows apart.

But the trouble is that when space and time appear in the classical theory... that actual point itself is a singular point in the mathematics.

Mathematics breaks down, and so... you cannot use that to give you a creation theory.

If one goes back in time... one comes to the Big Bang singularity... where the 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 singularities... 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... without necessarily having a sort of a chain... of past moments.

If we start where we are at the moment and start running backwards in time... then for a long time, things work perfectly normally.

But as you begin to get further and further back towards... what would be the origin point in the conventional real-time picture... you'd find that the nature of time changes... that the imaginary component becomes more and more prominent... until what ought to have been the singular point in the classical theory... gets smoothed away, and you have this beautiful picture... of these bowls where the creation of the universe is pictures... of where we are now, and a smooth bowl of the 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 boundary or edge... it would neither be created nor destroyed.

It would simply be.

What place, then, for a creator?

All you can really say is that the universe is... because it's a self-consistent mathematical structure.

There's no past because, unlike the creation-as-a-point scenario... there's nothing for it to be created in.

So to say it's created from nothing is 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.

The use of a 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... invented by man... 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 pieces on the floor... but you will never see the cup gather itself back together... and jump back on the table.

The increase of disorder, or entropy... is what distinguishes the past from the future... giving a direction to time.

He fell ill in Switzerland.

When he came back, he was on a ventilator.

Because he's on a ventilator, you've got a tube down your throat... and therefore you can't speak, just for that reason.

For that period, which may 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.

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 uncomfortable, 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 tracheostomy operation... removed my ability to speak altogether.

After a long time... well, it seemed like a long time... somebody came up with this brilliant gadget.

They didn't have it at the Cambridge hospital.

They got it from somewhere in London.

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

It's a 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.

They look at a letter, and you can see which letter they're looking at... most of the time. Sometimes you can't be sure.

So you would get the patient to spell out what they wanted.

So each letter... they have to look to pick out the A.

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


Stephen wasn't willing to accept that he wasn't going to speak again... and he thought he would be giving in... by trying to find a method of communicating other than speech.

I remember I went in one evening... and this was the first time that he asked... to be gotten out of bed to use the computer.

Sometimes they'd sit him up so he wasn't lying in 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 on there after saying hello...

Stephen's always 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... he was told he needed 24-hour nursing, and everyone was saying...

"How is he going to go in and do work?

Is he going to trail around with nurses after him in the office?"

And of course he did.

They talked originally of him working at home... which he wasn't happy with.

And so, after a period of recuperation at home... he just decided to go back into the office.

And he'd make the trip from his house to the office... which is, I don't know, half a mile in his wheelchair... with a nurse walking along with him.

This is at the time when he was still driving around... with the bag and the 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 onto 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 backward.

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.

Usually when he gives a problem, he has a good idea... of what the answer should be.

I went to look at it, and it took me a few months... to understand what it was about, and I came back and said, "I get this answer."

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

I said, "That's what I get." So I went to the blackboard, explained what it was.

He said, "Did you think about that particular case?" I said, "No, I didn't."

So I went back... and I calculated what he'd talked to me about.

I 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, no.

This doesn't work. Did you think about that?"

I said, "Oh, no. I'd forgotten about that particular case."

So I went back to the drawing board and started calculating again... and again I got the same answer.

So I went back to see Stephen, and this dragged on for two or three months.

Finally he said to me...

"Maybe one of your approximations is not valid."

So me and a colleague decided to do the thing with computers.

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 I'd said before... and not the way Stephen said, so we went to see Stephen and said, "See? Again."

I had made 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 the 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 have had the freedom... to choose the laws the universe obeyed.

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

There may 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 the timing of consciousness... and they seem to lead to a very odd picture... which doesn't even quite make consistent sense.

Whether refinement of these experiments... might get rid of this kind of anomaly I'm not sure... but it does look a little as though there is something very odd about consciousness... and somehow almost as though the 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 don't know if it's fair to say what happens after one dies... but it's a plausible picture... that you could be somebody else... and that somebody else could be somebody that lived in the past, not in the future.

Even if there is 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 think it's... Yeah.

So... it's... it's...

Some people, I think, take the view that the universe is just there... and it sort of runs and runs, and it just sort of computes... and we happen somehow by accident to find 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 is 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 the 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 the Big Crunch.

I do, however, have certain advantages... over many other prophets of doom.

Whatever happens ten 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 10:45...

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 traveling 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... of seeing Stephen in certain situations.

He was always moving.

Always.

Well, hardly ever still.

It was the same thing about his face and gesture... 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... and I must say Stephen looked very much like he does now... if one thinks of him like that.

He does believe very intensely... in the 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.

Why shouldn't you go on thinking about the unthinkable?

Somebody's got to start sometime.

Think how many things were unthinkable a century ago... and yet people have thought them.

And often they also seemed quite unpractical.

Not all the things Stephen says probably... are to be taken as gospel truth.

He's a searcher. He's looking for things.

And sometimes he probably talks nonsense. Well, don't 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.

You don't know where the boundaries are, do you?

You don't know what your 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... philosophers, scientists, and just ordinary people... be able to take part in the discussion of 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.