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 café 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 49/
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, étais-je enclin à 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.