A Brief History of Time Page #7

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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

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