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 caf
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.