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In 1988, I wrote a popular science
book called A Brief History Of Time,

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which sold over ten million copies.

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I say that not to brag,

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but to underline the deep fascination

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we all have with our universe.

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20 years ago, people rushed
to buy Stephen Hawking's book.

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It was an unlikely
sensational best seller,

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and he became an instant celebrity.

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In the book,

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he promised we would
soon have the ultimate answer -

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a theory of everything that
explained how the universe began.

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But 20 years on,

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it remains tantalisingly elusive,

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and Hawking's body is deteriorating.

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Now his only way of communicating

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is through one muscle in his cheek.

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For Hawking, time is running out
to unlock the mysteries

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that could finally make him
master of the universe.

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These films are a journey
into his extraordinary quest

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for a theory of everything.

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He does not see himself as a genius.

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He sees himself
as one of those lucky people

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who get paid to do what they love.

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It's just that his job is a little
bit different from most people's.

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20 years ago, Hawking said
he wanted to know the mind of God.

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He felt he was on the brink
of delivering a simple,
elegant set of laws

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that would explain
everything in our universe

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and, more importantly,
how it all began.

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How can we understand the universe?

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Is it arbitrary
or is there a grand design?

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Do we still need a God?

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20 years on,

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my need to find answers
to the fundamental questions
about our existence

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is undiminished.

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Hawking's need to find
answers started early.

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He was born in 1942, during
the darkest days of World War II.

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Hawking has always enjoyed
the fact

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that he was born
300 years to the day

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after the death of that other
revolutionary scientist, Galileo.

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As a schoolboy,
he was gifted and enquiring.

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His father hoped
he'd study medicine.

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He chose physics.

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But in 1963,
while studying for his PhD,

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he was told he had
a life-threatening disease.

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His response to the bad news
was later made much of in the press.

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How true is it that
when you were first diagnosed,

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that you listened to Wagner
and drank heavily?

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I took to listening to Wagner,

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but reports in magazine articles that
I drank heavily are an exaggeration.

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The trouble is,
once one article said it,

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other articles copied it,

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because it made a good story.

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The outlook was bleak.

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Motor neurone disease
is progressive.

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The nerves controlling the muscles
degenerate to complete paralysis,

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while the brain remains intact.

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He was given two years to live.

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Before then, as a student,

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Hawking had, by his own admission,
become somewhat directionless.

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Now faced with an uncertain
and nightmarish future,

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he developed a fierce determination
that would become his hallmark.

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Often to the exclusion of all else,

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he set his sights on
the greatest questions in physics.

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Professor Bernard Carr was
a graduate student of Hawking's,

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and became his close colleague.

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And of course it's required
a huge amount of effort for him...

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..but in some sense

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I think it's given Stephen
the determination to overcome
the problems

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and it made him even more
determined, I think,

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to crack the ultimate
problems of physics.

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So young Hawking set off to crack
the ultimate problem of physics.

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He wanted to get an idea

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of what the beginning of
the universe looked like.

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But to do that,

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he'd have to attempt what everyone
else thought was impossible.

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Hawking was going to have to
unify the two great,

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but very different,
theories of physics.

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Einstein's theory of relativity
is the theory of the very large.

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Of planets, galaxies and space.

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Quantum mechanics
is the theory of the very small.

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Of atoms, particles and forces.

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But to understand how
the universe came about,

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Hawking would have to
force the two together.

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My life's work has been to unify
the theories of the very large

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and the very small.

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Only then can we answer
the more challenging questions.

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Why are we here?

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And where did we come from?

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It's a quest that,
despite near total paralysis,

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he's not about to give up on.

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He's a very tenacious,
courageous individual,

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but he never thinks of it like that,
he just gets on with it.

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That's really how he gets on
with everything.

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He can be quite exhausting
as well, you know, very demanding.

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He doesn't get tired
like the rest of us.

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We all get very tired,
but he can keep going.

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Physicists love to explain how our
universe arose and how it works.

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We understand enormous amounts,

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but when asked,
"How did it all come to be?,

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we don't have one single answer yet"

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Can I have a minute, please?

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Stephen Hawking is the
Lucasian Professor of Mathematics

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at Cambridge University,

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a post once held by Sir Isaac Newton.

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Age 66, Hawking still tirelessly

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puts in a full week
of teaching and research.

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Hawking's schedule is frantic.

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As well as trying to find out
how our universe came about,

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he tries to satisfy
an incessant demand
for his illustrated lectures.

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Can you hear me?

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(ALL) Yes.

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According to the Boshongo people
of Central Africa,

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in the beginning
there was only darkness,

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water and the great god Bumba.

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One day Bumba, in pain from a
stomach ache, vomited up the sun.

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The sun dried up some
of the water, leaving land.

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Still in pain,
Bumba vomited up the moon,

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the stars and then some animals -

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the leopard, the crocodile,
the turtle and finally, man.

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This creation myth,
like many others,

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tries to answer the questions
we all ask.

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Why are we here?

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Where did we come from?

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"Why are we here?"

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was a question Hawking asked himself
a lot back in 1965,

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while contemplating
what the doctors had told him

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might well be a very short
life ahead.

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Then he heard reports
of a lecture given in London

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by a brilliant young
mathematician, Roger Penrose.

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Sorry to interrupt
but Roger Penrose is here.

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I was wondering,
shall I bring him up?

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Yes.

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Thank you, Stephen.

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Penrose's ground-breaking
work catapulted Hawking
out of his depression.

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I certainly remember
Stephen in lectures

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asking extremely awkward questions
at the ends of seminars,

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or in the course of seminars -

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that was the thing that
struck me particularly about him.

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They were penetrating questions
I should say, not just awkward.

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Penrose had given Hawking a glimpse

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of how physics could be used
to answer the question,

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"Why are we here?"

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For both Penrose and Hawking,

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the starting point
was Einstein's Theory of Relativity.

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The theory of the very large.

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It explains how the universe works,

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and how insignificant
our place in it is.

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One small planet in a tiny galaxy,
lost in the vast realms of space,

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as cosmologist
Pedro Ferreira explains...

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Now, let's imagine that this enormous
library is our visible universe,

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and we know that the universe
is sprinkled with galaxies -

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and I really mean sprinkled -

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there's a lot of empty space
around each galaxy.

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Let's take our galaxy, the Milky Way.

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It would comfortably fit
in a full stop in Stephen's book.

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Our galaxy is microscopic

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compared to the gigantic
tracks of empty space
that dominate the universe.

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But Einstein showed
that all that empty space

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turns out to have
some remarkable properties.

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Let's imagine that this basketball
is a celestial object like a star,

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OK, and let's imagine that this
book shelf with these books is space.

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In our classical view of space,
it would be rigid like this,

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it would just be this static thing,
this thing that is unresponsive,

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but in our modern view,
this star as it moves through space,

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it warps it, it dents it,
it bends it,

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and other objects that then
move through this space

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will feel this warp,
will feel these bends,
these warps and

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will move according to that.

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They won't move in straight lines,

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they'll feel these bends
and they'll curve.

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The fact that big objects like stars
can actually bend and curve space,

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is now an everyday notion to
astrophysicists like Kim Weaver.

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What we're talking about
in terms of astronomy

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and cosmology are objects that
have a huge amount of mass -

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a planet, a planet-sized object

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or a moon-sized object
or a star-sized object.

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The mass of this object
bends space around it.

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If the ball here that is
at the centre of this sheet

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is representing the sun,

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and this penny is representing
a planet like the earth,

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then you can use the penny
to demonstrate

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how the earth orbits the sun.

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Most of us think of gravity
as an invisible force,

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which holds us on the earth

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and keeps the earth in orbit
round the sun.

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So far, so good.

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But what physics
says is really happening

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is that planets are trapped
in areas of curved space.

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The earth is actually rolling round
and down into an area of space

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warped by the sun.

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The penny rolls in quickly,

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but of course it'll take the earth
billions of years to hit the sun.

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And it's the curvature of space
caused by the earth itself

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which holds us in place
on our planet.

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Hawking knew Einstein's work
like the back of his hand,

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but what excited him was that
Penrose had used the theory

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to discover something
altogether bizarre.

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It was possible not just
to bend space,

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but to twist it
right back in on itself,

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to create a black hole.

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Penrose showed that
when a massive star burns out,

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it collapses in on itself
in a spectacular way.

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Something that was many times
bigger than our sun

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is compressed
to a size smaller than an atom.

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It becomes so incredibly dense
that it pulls space back towards it.

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Everything in that
warped space is eaten up.

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Even light cannot
escape its clutches.

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Around the ultra-dense centre,
there forms a sphere of darkness,

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that we now call a black hole.

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But Penrose hadn't just shown
that a massive star

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could collapse into a black hole.

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What gripped Hawking was
that Penrose had proved,

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using Einstein¡¯s equations,

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that at the very centre
of a black hole,

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there had to be a plughole,

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down which matter,
space and time disappeared.

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The plughole had a fancy
mathematical name -

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a singularity.

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Hawking was excited and mystified.

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In 1965,

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Roger Penrose showed that
if a star collapsed below
a certain critical radius,

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it would inevitably
develop a singularity,

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at which time would come to an end.

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At first I didn't understand
either the significance

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or the proof of this result.

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Hawking became obsessed with
understanding the singularity.

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It was a poignant choice
of specialist subject.

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A young man who'd been told
he had two years to live

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was wrestling with a point in space

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where the universe disappeared out
of existence.

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This was typical
of Hawking's stubbornness,

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refusing to accept the limitations
of his body, or his brilliant mind.

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And even in his private life,
he exhibited the same bravado.

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Despite his family's concerns
over his health,

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he met, fell in love with,
and married Jane Wilde,
a languages student.

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As Jane later remembered
in an interview,

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death seemed to be all around.

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It was the time of the Cold War
with Russia,

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an age of defiance.

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It wasn't a terribly difficult
decision to take, to marry Stephen,

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because I think a lot of people
had forgotten that, at that time,

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every day, one read
reports in the newspapers

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that a nuclear war was likely to
break out in the next year or two.

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People said they weren't
going to have children

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because there
was going to be a nuclear war,

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00:17:48,500 --> 00:17:53,350
and the fact that Stephen
had been diagnosed as only
having a couple of years to live

247
00:17:53,400 --> 00:17:56,350
didn't really seem to be very much
different to the situation

248
00:17:56,400 --> 00:17:58,750
that was facing
the rest of us, anyhow.

249
00:18:05,800 --> 00:18:09,750
But out of this gloom,
Hawking managed to conjure up...

250
00:18:10,200 --> 00:18:11,950
light.

251
00:18:12,000 --> 00:18:14,650
Out of what seemed to be
the end of everything,

252
00:18:14,900 --> 00:18:17,050
he found a beginning.

253
00:18:19,100 --> 00:18:21,850
Penrose had shown
that bits of the universe

254
00:18:21,900 --> 00:18:24,250
could be sucked
into a singularity,

255
00:18:24,300 --> 00:18:27,550
a tiny plughole
at the centre of a black hole.

256
00:18:28,200 --> 00:18:32,650
Hawking took Penrose's
equations and reversed them.

257
00:18:32,700 --> 00:18:35,150
Like running a film backwards.

258
00:18:35,200 --> 00:18:39,550
Where Penrose showed the universe
disappearing into a black hole,

259
00:18:39,600 --> 00:18:42,650
Hawking showed it came from one.

260
00:18:42,700 --> 00:18:46,850
For thousands of years, man had
wondered how the universe began.

261
00:18:46,900 --> 00:18:49,750
Now, a young PhD
student from Cambridge

262
00:18:49,800 --> 00:18:51,650
had come up with an answer.

263
00:18:51,900 --> 00:18:56,650
It was an incredible turning point
in our understanding of the world.

264
00:18:56,900 --> 00:19:01,750
But Hawking's results raised
as many questions as they solved.

265
00:19:03,700 --> 00:19:08,050
He could prove the universe started
from a tiny, single point,

266
00:19:08,200 --> 00:19:12,450
but frustratingly, not how or why.

267
00:19:15,900 --> 00:19:20,550
It seemed to many
that this inexplicable,
sudden appearance of the universe,

268
00:19:20,600 --> 00:19:24,450
expanding out
from a microscopically tiny point,

269
00:19:24,500 --> 00:19:26,750
had to be a miracle.

270
00:19:32,500 --> 00:19:35,250
There are two attitudes one can take

271
00:19:35,300 --> 00:19:38,350
from the results of Penrose
and myself.

272
00:19:39,300 --> 00:19:42,550
One is that God chose
how the universe began

273
00:19:42,600 --> 00:19:45,550
for reasons we could not understand.

274
00:19:45,900 --> 00:19:49,350
At a conference on cosmology
in the Vatican,

275
00:19:49,400 --> 00:19:52,450
the Pope told the delegates
that it was OK

276
00:19:52,500 --> 00:19:55,450
to study the universe after it began.

277
00:19:56,200 --> 00:19:59,550
But they should not enquire
into the beginning itself,

278
00:19:59,600 --> 00:20:03,850
because that was the moment
of Creation and the work of God.

279
00:20:07,000 --> 00:20:12,350
I was glad he didn't realise I had
presented a paper at the conference

280
00:20:12,400 --> 00:20:15,250
suggesting how the universe began.

281
00:20:16,100 --> 00:20:20,550
I didn't fancy the thought of
being handed over to the Inquisition

282
00:20:20,600 --> 00:20:22,250
like Galileo.

283
00:20:22,300 --> 00:20:25,250
LAUGHTER

284
00:20:25,300 --> 00:20:26,750
APPLAUSE

285
00:20:26,800 --> 00:20:29,050
Hawking's response to his results

286
00:20:29,100 --> 00:20:31,750
was to decide that
the equations he'd used,

287
00:20:31,800 --> 00:20:36,550
Einstein's Theory of Relativity,
were not the whole story.

288
00:20:38,400 --> 00:20:41,150
General relativity
makes a prediction

289
00:20:41,200 --> 00:20:44,050
that the universe
was once infinitely small,

290
00:20:44,100 --> 00:20:48,850
but it loses the ability to describe
the universe when it was tiny.

291
00:20:57,000 --> 00:21:00,050
Hawking now knew
that our entire universe

292
00:21:00,100 --> 00:21:02,750
did start out as a tiny dot,

293
00:21:03,100 --> 00:21:04,950
but he wasn't going to be happy

294
00:21:05,000 --> 00:21:08,650
until he could describe
how that dot came about.

295
00:21:09,500 --> 00:21:12,950
Hawking had lain down
a huge challenge for himself

296
00:21:13,100 --> 00:21:15,450
and the rest of physics.

297
00:21:15,500 --> 00:21:18,750
As physicist Michio Kaku explains.

298
00:21:19,500 --> 00:21:20,950
"The bottom line is,

299
00:21:21,100 --> 00:21:26,050
Einstein's equations are useless
at the instant of the Big Bang.

300
00:21:27,600 --> 00:21:30,150
We physicists say that
a long time ago,

301
00:21:30,200 --> 00:21:33,350
the universe was so small
it was smaller than a basketball,

302
00:21:33,400 --> 00:21:35,450
you could put the universe
in your pocket,

303
00:21:35,500 --> 00:21:38,250
it was smaller than an electron.

304
00:21:38,300 --> 00:21:41,950
Some people call it a
"singularity of infinite gravity".

305
00:21:42,000 --> 00:21:43,450
Now, that's silly.

306
00:21:43,500 --> 00:21:46,250
There's no such thing as
infinite gravity,

307
00:21:46,300 --> 00:21:50,750
it just means that
we use the word "singularity"
to hide our ignorance.

308
00:21:50,800 --> 00:21:53,850
We don't know what
this singularity is.

309
00:21:56,200 --> 00:22:00,650
Unraveling this singularity,
this tiny point of creation,

310
00:22:00,800 --> 00:22:03,750
became Hawking's life's work.

311
00:22:04,100 --> 00:22:06,950
(MOUTHS)

312
00:22:07,200 --> 00:22:11,650
But it was a race against time,
against encroaching disability.

313
00:22:12,300 --> 00:22:15,950
Hawking has defied all
the predictions of his doctors,

314
00:22:16,100 --> 00:22:20,250
his disease has progressed much more
slowly than they thought it would.

315
00:22:20,600 --> 00:22:25,050
But today, he has only
the use of his facial muscles.

316
00:22:27,400 --> 00:22:31,750
"He communicates, actually using
just one muscle on his cheek.

317
00:22:33,200 --> 00:22:36,150
There's a little censor,
and whenever he moves his cheek,

318
00:22:36,200 --> 00:22:39,150
that sends a pulse through
to his computer.

319
00:22:40,800 --> 00:22:42,850
By tensing that one muscle,

320
00:22:42,900 --> 00:22:45,250
he can do everything
from checking his e-mail,

321
00:22:45,300 --> 00:22:48,950
to speaking,
to browsing the internet.

322
00:22:50,400 --> 00:22:55,250
I was there with him when he changed
from using the finger switch

323
00:22:55,300 --> 00:22:59,250
on to the blink switch,
and it was quite a...

324
00:22:59,400 --> 00:23:03,150
Well, the blinks which sat
in a cupboard for 13 years

325
00:23:03,200 --> 00:23:05,350
before he would even
think of trying it,

326
00:23:05,400 --> 00:23:08,450
so he tends to go
with what he knows.

327
00:23:10,300 --> 00:23:13,350
Every time he changes to another
type of technology,

328
00:23:13,400 --> 00:23:16,450
he seems to see
that as admitting defeat.

329
00:23:16,500 --> 00:23:20,550
So, he's very resistant to
changing to other technologies.

330
00:23:23,700 --> 00:23:26,450
Can you finish in 10 minutes?

331
00:23:26,500 --> 00:23:29,150
10 minutes? 15. Maybe!

332
00:23:32,700 --> 00:23:35,950
It becomes very apparent
that his struggle is daily,

333
00:23:36,000 --> 00:23:40,450
it's not just
something that he gets used to,

334
00:23:40,700 --> 00:23:42,950
then it's not a problem any more.

335
00:23:43,500 --> 00:23:46,950
At the same time, you realise
how much help he's got.

336
00:23:47,800 --> 00:23:51,250
You know... That doesn't mean
it's easy for him.

337
00:23:55,200 --> 00:23:58,050
But Hawking is nothing
if not determined,

338
00:23:58,100 --> 00:24:03,550
and back in the 1970s, he set his
sights on solving the big problem -

339
00:24:03,700 --> 00:24:07,550
what happened
at the moment of Creation?

340
00:24:21,200 --> 00:24:25,550
In the early 1970s, black holes
were the agents of death,

341
00:24:25,600 --> 00:24:28,250
the place where everything
we know about the cosmos

342
00:24:28,300 --> 00:24:30,250
came to a chilling end.

343
00:24:30,300 --> 00:24:33,550
But to a young physics researcher
like Stephen Hawking,

344
00:24:33,700 --> 00:24:35,850
they were an exciting challenge.

345
00:24:40,800 --> 00:24:45,350
He'd already shown that the universe
arose from a single, tiny point

346
00:24:45,800 --> 00:24:49,150
now he wanted a complete theory
of everything.

347
00:24:49,200 --> 00:24:53,150
A theory that would describe
the moment of universe's creation

348
00:24:53,200 --> 00:24:58,850
in precise detail, and again,
black holes would point the way.

349
00:25:04,000 --> 00:25:06,150
My own work on black holes

350
00:25:06,200 --> 00:25:11,550
began with a Eureka! moment
while getting into bed in 1970.

351
00:25:14,700 --> 00:25:19,450
In 1970, getting into bed was
a protracted business for Hawking.

352
00:25:19,600 --> 00:25:21,750
His paralysis was increasing

353
00:25:21,800 --> 00:25:25,950
and he needed constant care
and attention from his wife, Jane.

354
00:25:26,000 --> 00:25:27,950
And they'd started a family.

355
00:25:28,200 --> 00:25:31,850
But despite his disability,
the couple were managing.

356
00:25:31,900 --> 00:25:34,950
He'd taken a research post
at Cambridge University

357
00:25:35,000 --> 00:25:39,150
and was eagerly pursuing his quest
to understand the universe.

358
00:25:49,700 --> 00:25:53,050
What Hawking had glimpsed
that night getting into bed

359
00:25:53,100 --> 00:25:56,850
was something very peculiar
about black holes.

360
00:25:57,000 --> 00:25:59,950
Hawking knew that every object
in the universe

361
00:26:00,000 --> 00:26:02,750
could be heated up or cooled down,

362
00:26:02,900 --> 00:26:05,450
but black holes were different.

363
00:26:06,900 --> 00:26:10,550
Heat, would never get out
of a black hole, it seemed.

364
00:26:10,800 --> 00:26:13,050
This started to niggle Hawking,

365
00:26:13,100 --> 00:26:17,750
but it would turn out to be the key
to the mystery of creation.

366
00:26:25,200 --> 00:26:27,550
Hawking was about to
attempt something

367
00:26:27,600 --> 00:26:30,450
no other physicist
had ever achieved.

368
00:26:30,500 --> 00:26:34,850
For 50 years physicists
had failed to unite the theories

369
00:26:34,900 --> 00:26:37,850
of the very big and the very small.

370
00:26:37,900 --> 00:26:40,050
Einstein's theory of gravity

371
00:26:40,100 --> 00:26:44,350
would not fuse with the very
different theory of how atoms work -

372
00:26:44,400 --> 00:26:46,350
quantum mechanics.

373
00:26:46,400 --> 00:26:48,150
But what Hawking had glimpsed

374
00:26:48,200 --> 00:26:50,950
was a point
where the two must clash -

375
00:26:51,200 --> 00:26:54,450
at the very edge of a black hole.

376
00:26:54,500 --> 00:26:57,650
What happens
if you have a black hole

377
00:26:57,700 --> 00:27:00,650
which is sitting there, it's black,

378
00:27:00,700 --> 00:27:02,150
that's why it's called a black hole,

379
00:27:02,200 --> 00:27:04,750
no light comes out of it.

380
00:27:04,800 --> 00:27:08,550
What happens if you include
the effects of quantum mechanics?

381
00:27:08,900 --> 00:27:14,350
Einstein's theory said the black
hole was a smooth, perfect sphere.

382
00:27:14,900 --> 00:27:19,250
Hawking plunged it into a sea
of particles and atoms.

383
00:27:19,300 --> 00:27:22,450
The two theories
sputtered and fought each other.

384
00:27:22,500 --> 00:27:26,250
Somehow, Hawking must
bring them together.

385
00:27:27,000 --> 00:27:32,650
The problem of
reconciling Einstein's theory
with quantum mechanics

386
00:27:32,700 --> 00:27:36,750
is one of the holy grails
of modern physics.

387
00:27:37,600 --> 00:27:43,050
What Hawking did
in the early '70s was,

388
00:27:43,100 --> 00:27:47,350
he didn't try to
solve this problem completely,

389
00:27:48,400 --> 00:27:53,650
but he tried to put quantum mechanics
and general relativity together

390
00:27:53,700 --> 00:27:56,150
in a very limited fashion.

391
00:27:57,400 --> 00:27:59,350
What was all the more remarkable

392
00:27:59,400 --> 00:28:03,450
was that now unable to write down
long equations and calculations,

393
00:28:03,500 --> 00:28:07,550
Hawking had to imagine
the whole process in his head.

394
00:28:23,000 --> 00:28:25,850
As well as space and black holes,

395
00:28:25,900 --> 00:28:30,350
Hawking had to visualise a world
we are all unfamiliar with,

396
00:28:30,400 --> 00:28:35,250
the bizarre realm of the very small,
of the atom.

397
00:28:36,500 --> 00:28:39,750
A good way to think of an atom
is a bit like our solar system.

398
00:28:39,800 --> 00:28:43,550
You've got a nucleus at the centre
and electrons whizzing around.

399
00:28:44,400 --> 00:28:48,250
Now, let's imagine that this marble
is the nucleus of an atom.

400
00:28:49,000 --> 00:28:51,650
An electron will be
the width of this hair.

401
00:28:52,600 --> 00:28:55,050
Now again, we're used to
seeing in textbooks

402
00:28:55,700 --> 00:28:59,250
that an electron is more or less
this distance from a marble,

403
00:28:59,300 --> 00:29:01,250
but it's not, it's not this far,

404
00:29:01,500 --> 00:29:03,350
it's not this far.

405
00:29:08,700 --> 00:29:10,350
It's not this far...

406
00:29:13,600 --> 00:29:15,550
It's not even this far...

407
00:29:19,800 --> 00:29:21,250
Not even here.

408
00:29:27,000 --> 00:29:30,550
On this scale, where the nucleus
is the size of a marble

409
00:29:30,600 --> 00:29:32,750
and an electron
is the width of a hair,

410
00:29:32,800 --> 00:29:37,450
the electron would actually be
two miles away from the nucleus.

411
00:29:42,900 --> 00:29:47,750
At the atomic level,
particles are almost not there.

412
00:29:47,800 --> 00:29:50,250
They're less like
solid lumps of matter

413
00:29:50,300 --> 00:29:53,750
and more like tiny empty
force fields,

414
00:29:53,800 --> 00:29:56,850
and as force fields, they shimmer.

415
00:29:56,900 --> 00:30:00,450
Physicists often describe
them as waves.

416
00:30:04,100 --> 00:30:08,050
Water, sound and light
can behave like waves,

417
00:30:08,100 --> 00:30:11,050
but so too can the parts of the atom

418
00:30:11,300 --> 00:30:13,550
and that means they can spread out

419
00:30:13,600 --> 00:30:16,550
to be in more than just
one place at a time.

420
00:30:19,200 --> 00:30:22,550
Common sense says that
when I fire this gun,

421
00:30:22,600 --> 00:30:26,150
one ball hits one target,
that's it.

422
00:30:26,200 --> 00:30:30,050
If this is an electron gun
hitting many targets,

423
00:30:30,100 --> 00:30:33,350
I find out that one electron
has a probability

424
00:30:33,400 --> 00:30:36,350
of hitting many targets
at the same time.

425
00:30:37,200 --> 00:30:40,850
Now, that violates common sense.

426
00:30:40,900 --> 00:30:43,850
I thought it was
one ball, one target.

427
00:30:43,900 --> 00:30:47,650
In the quantum world,
common sense is violated.

428
00:30:47,800 --> 00:30:51,750
Common sense has no place
in the quantum world.

429
00:31:00,100 --> 00:31:04,550
Hawking knew that atoms were not
like little billiard balls.

430
00:31:06,000 --> 00:31:09,850
They turn out to be
much more fuzzy and erratic.

431
00:31:10,300 --> 00:31:13,950
How could he join
Einstein's stars and planets

432
00:31:14,000 --> 00:31:17,150
that float sedately
along nice curved lines,

433
00:31:17,200 --> 00:31:20,850
with atoms that
buzz around in a frenzy?

434
00:31:25,100 --> 00:31:27,150
At a very tiny level,

435
00:31:27,200 --> 00:31:30,650
our universe
is like a crazy dance of waves

436
00:31:30,700 --> 00:31:33,250
jangling to a myriad of beats.

437
00:31:33,300 --> 00:31:36,650
Particles appear and disappear
at random,

438
00:31:37,100 --> 00:31:41,950
and at this level nothing is certain,
not even existence.

439
00:31:48,300 --> 00:31:50,450
Atoms are a bit like people.

440
00:31:50,700 --> 00:31:54,550
They're very hard to predict
with absolute certainty.

441
00:31:56,200 --> 00:31:58,650
They do roughly
what you'd expect of them,

442
00:31:58,700 --> 00:32:00,550
but never exactly.

443
00:32:01,700 --> 00:32:04,750
With atoms, it's even hard
to be totally certain

444
00:32:04,800 --> 00:32:06,550
whether they exist or not.

445
00:32:08,000 --> 00:32:11,050
Sometimes, Hawking knew,
atoms pop up

446
00:32:11,100 --> 00:32:14,650
where there should be
absolutely nothing around.

447
00:32:15,600 --> 00:32:19,750
In fact, out in space,
it happens all the time.

448
00:32:27,100 --> 00:32:32,050
The theory of the very tiny
says space is never empty.

449
00:32:32,300 --> 00:32:33,750
At an atomic level,

450
00:32:33,800 --> 00:32:37,450
there is always a tiny,
tiny amount of activity.

451
00:32:38,100 --> 00:32:40,050
But the theory of the very big

452
00:32:40,100 --> 00:32:43,850
says nothing exists
at the edge of a black hole.

453
00:32:44,900 --> 00:32:49,150
Hawking realised this was where
the two theories clashed.

454
00:32:50,000 --> 00:32:53,550
He had to find out
what was really going on.

455
00:32:56,500 --> 00:33:01,250
According to the theory
of the very tiny, in empty space,

456
00:33:01,300 --> 00:33:05,450
there are pairs of subatomic particles
that emerge out of the void,

457
00:33:05,500 --> 00:33:09,550
exist for a tiny moment
and then destroy each other.

458
00:33:11,800 --> 00:33:15,350
And so the idea is that
out of nothing if you like,

459
00:33:15,400 --> 00:33:19,150
a pair of particles is created
and then exists for a short time

460
00:33:19,200 --> 00:33:20,750
and then annihilates,

461
00:33:20,800 --> 00:33:22,950
and that's happening throughout space,

462
00:33:23,000 --> 00:33:25,250
so it's happening there
and it's happening there

463
00:33:25,300 --> 00:33:27,050
and it's happening there.

464
00:33:31,800 --> 00:33:35,350
This pair of particles
is like yin and yang,

465
00:33:35,400 --> 00:33:36,350
night and day,

466
00:33:36,400 --> 00:33:40,050
opposites that would not exist
without each other.

467
00:33:40,200 --> 00:33:44,850
One has positive mass
and the other has negative mass.

468
00:33:45,800 --> 00:33:48,350
But Hawking asked, what would happen

469
00:33:48,400 --> 00:33:52,650
if this pair of particles
bumped up against a black hole?

470
00:34:00,200 --> 00:34:03,150
Hawking realised
that the positive particle

471
00:34:03,200 --> 00:34:06,850
would have just enough energy
to escape the black hole,

472
00:34:07,700 --> 00:34:11,550
but the particle with negative mass
would fall in

473
00:34:13,000 --> 00:34:17,150
and it would do something
extraordinary to the black hole.

474
00:34:19,100 --> 00:34:21,950
The particle that goes
inside the black hole

475
00:34:22,000 --> 00:34:25,750
eventually decreases
the mass of the black hole.

476
00:34:25,800 --> 00:34:27,750
It effectively has negative mass.

477
00:34:27,800 --> 00:34:31,750
But the particle that goes off
to the distant observer,

478
00:34:31,800 --> 00:34:35,750
is there observed
as part of radiation.

479
00:34:39,900 --> 00:34:42,850
Although we now understand
why black holes

480
00:34:42,900 --> 00:34:45,250
have to give off thermal radiation,

481
00:34:45,300 --> 00:34:48,750
it came as a complete surprise
at the time.

482
00:34:50,900 --> 00:34:54,850
At first I thought
I must have made a mistake.

483
00:35:00,200 --> 00:35:02,850
But Hawking had not made a mistake.

484
00:35:04,100 --> 00:35:09,950
Around a black hole is an almost
imperceptible microscopic glow.

485
00:35:10,600 --> 00:35:13,750
Positive mass particles
fly off from it,

486
00:35:13,900 --> 00:35:16,650
behaving just like heat.

487
00:35:18,600 --> 00:35:22,250
Negative mass particles fall in.

488
00:35:22,300 --> 00:35:25,350
Slowly, almost imperceptibly,

489
00:35:25,400 --> 00:35:28,350
they decrease the mass of the black hole

490
00:35:28,400 --> 00:35:32,650
and this eventually
has catastrophic consequences.

491
00:35:36,700 --> 00:35:39,550
So what the Hawking result implies,

492
00:35:39,600 --> 00:35:42,850
it means that the black hole,
instead of being black,

493
00:35:42,900 --> 00:35:46,250
is actually always
emitting radiation.

494
00:35:48,200 --> 00:35:50,450
What is happening
is that for most of its life,

495
00:35:50,600 --> 00:35:53,850
the black hole
is gently sizzling away,

496
00:35:53,900 --> 00:35:56,150
but eventually
it gets smaller and smaller,

497
00:35:56,200 --> 00:35:58,250
the temperature
gets hotter and hotter

498
00:35:58,300 --> 00:36:00,850
and eventually it gets to a point
where it's so hot

499
00:36:00,900 --> 00:36:02,550
that it essentially explodes,

500
00:36:02,600 --> 00:36:06,350
it loses all the rest of its mass
in a very, very short time.

501
00:36:11,300 --> 00:36:15,350
Hawking had transformed the black
hole from a ball of nothing

502
00:36:15,400 --> 00:36:19,450
into a galactic monster,
that chews up the universe

503
00:36:19,500 --> 00:36:22,650
and spits out fire and brimstone.

504
00:36:27,900 --> 00:36:29,750
When black holes were first thought of

505
00:36:29,800 --> 00:36:31,550
and when I first started
studying black holes,

506
00:36:31,600 --> 00:36:35,050
I remember thinking, "Oh, a black
hole, it's the end of everything,

507
00:36:35,100 --> 00:36:38,050
a star collapses down
and everything disappears into it

508
00:36:38,100 --> 00:36:39,450
and nothing ever comes out,

509
00:36:39,500 --> 00:36:41,750
so maybe it's really boring?"

510
00:36:43,200 --> 00:36:47,050
But really, black holes
represent our best way

511
00:36:47,100 --> 00:36:51,550
to have an ultimate test of the physics
of understanding the universe.

512
00:36:56,600 --> 00:37:00,550
And astronomy has borne out
Hawking's discovery.

513
00:37:00,800 --> 00:37:04,450
Black holes now seem to be
where it all happens.

514
00:37:04,700 --> 00:37:09,350
They're the engines that rip up
the cosmos and create new stars

515
00:37:09,400 --> 00:37:12,450
and jets of energy and matter.

516
00:37:14,700 --> 00:37:17,350
"Black holes are not
ultimate end points,

517
00:37:17,400 --> 00:37:20,250
they really are beginnings
of something -

518
00:37:20,300 --> 00:37:24,950
around a black hole
you have enormous amounts
of activity going on.

519
00:37:25,000 --> 00:37:26,850
You have stars being ripped apart

520
00:37:26,900 --> 00:37:29,850
and you have discs of accreting
matter swirling around,

521
00:37:29,900 --> 00:37:33,250
you have cauldrons of heat
and light around a black hole,

522
00:37:33,300 --> 00:37:35,750
you have jets being produced
by a black hole.

523
00:37:35,800 --> 00:37:38,550
You have particles coming out
at half the speed of light,

524
00:37:38,600 --> 00:37:40,250
being shot away from a black hole,

525
00:37:40,300 --> 00:37:43,150
you have stars being born
around a black hole.

526
00:37:43,200 --> 00:37:45,550
There's an enormous amount
of stuff going on

527
00:37:45,700 --> 00:37:48,950
caused by the fact that
that black hole's really there,

528
00:37:49,200 --> 00:37:50,950
and that's exciting.

529
00:37:56,700 --> 00:38:00,550
Hawking had taken a great
leap forward in his quest.

530
00:38:00,600 --> 00:38:04,150
He'd linked the theories
of the big and the small

531
00:38:04,300 --> 00:38:07,550
for the first time ever in physics.

532
00:38:18,700 --> 00:38:22,850
What was really amazing
about this paper,

533
00:38:22,900 --> 00:38:26,850
really one of the most beautiful
papers in the 20th century,

534
00:38:27,100 --> 00:38:31,450
is that his argument
that this could happen

535
00:38:31,600 --> 00:38:34,950
relies on almost no assumptions.

536
00:38:35,900 --> 00:38:39,550
The assumptions about
the nature of quantum mechanics

537
00:38:39,600 --> 00:38:41,450
and the nature
of general relativity,

538
00:38:41,800 --> 00:38:47,850
that basically every living
physicist will agree with.

539
00:38:50,000 --> 00:38:54,750
But Hawking had done more than just
show that black holes were complex.

540
00:38:54,800 --> 00:38:57,250
The theory of the very tiny

541
00:38:57,300 --> 00:39:01,250
was starting to unlock
the secrets of the very large.

542
00:39:01,400 --> 00:39:04,550
Could he now apply it
to the entire universe?

543
00:39:04,600 --> 00:39:07,950
Could he now explain the big bang?

544
00:39:15,800 --> 00:39:22,050
By applying quantum mechanics
to the edge of the black holes
in the 1970s,

545
00:39:22,100 --> 00:39:26,150
I was able to revolutionise
our understanding of them.

546
00:39:27,000 --> 00:39:29,850
To expand our understanding further,

547
00:39:29,900 --> 00:39:34,450
we need to bring quantum mechanics
into the heart of the black hole.

548
00:39:43,300 --> 00:39:44,950
In the 1970s,

549
00:39:45,000 --> 00:39:48,550
it seemed Hawking had only to
wrest the key to the universe

550
00:39:48,600 --> 00:39:51,750
from the inner reaches
of his brilliant mind.

551
00:39:51,900 --> 00:39:55,850
But more humble problems
of health, love and fame

552
00:39:55,900 --> 00:40:00,050
would try to tempt him away
from his devotion to physics.

553
00:40:16,000 --> 00:40:18,550
This world that is so familiar,

554
00:40:18,800 --> 00:40:21,050
how did it come about?

555
00:40:21,300 --> 00:40:25,250
Can we ever discover
how all this came to be?

556
00:40:28,800 --> 00:40:31,250
Stephen Hawking runs a department

557
00:40:31,300 --> 00:40:33,850
that is still trying
to find the answer.

558
00:40:36,600 --> 00:40:40,850
He has his PhD students
and they have supervision,

559
00:40:40,900 --> 00:40:43,850
and they come in
every week and have lunch,
and they talk about ideas,

560
00:40:43,900 --> 00:40:46,050
and if they get stuck,
they can come to him.

561
00:40:47,800 --> 00:40:52,250
You have to have exceptionally
good students to be able to

562
00:40:52,300 --> 00:40:56,450
cope with the heavy work that
they have to have, and also with

563
00:40:56,500 --> 00:40:59,350
the communication, they really
have to know their subject.

564
00:41:01,900 --> 00:41:04,950
You have all survived the summer.

565
00:41:05,000 --> 00:41:06,350
LAUGHTER

566
00:41:07,100 --> 00:41:08,350
Very well.

567
00:41:08,400 --> 00:41:10,250
Start

568
00:41:12,300 --> 00:41:15,750
Aged 66, when many are retiring,

569
00:41:15,800 --> 00:41:19,050
Hawking shows no sign
of giving up his quest.

570
00:41:20,700 --> 00:41:24,950
The food's improved!

571
00:41:25,700 --> 00:41:28,450
Has it improved the work-rate
of the students?

572
00:41:31,100 --> 00:41:33,350
No!

573
00:41:33,400 --> 00:41:37,650
I think he caught you there!

574
00:41:37,700 --> 00:41:42,250
Hawking's life's work has been to
come up with a theory of everything,

575
00:41:42,300 --> 00:41:47,450
a theory that explains how our
universe works and how it arose.

576
00:41:50,500 --> 00:41:53,250
In the 1970s, he had huge success

577
00:41:53,300 --> 00:41:56,450
using the theory of the tiny,
quantum mechanics,

578
00:41:56,500 --> 00:41:59,050
to better explain black holes.

579
00:41:59,100 --> 00:42:01,050
But in the 30 years since,

580
00:42:01,100 --> 00:42:03,750
using it to explain
the entire universe

581
00:42:03,800 --> 00:42:06,450
has turned out to be
just a bit harder.

582
00:42:08,900 --> 00:42:12,050
Hawking has admitted that
he was over-confident.

583
00:42:12,200 --> 00:42:16,750
The early 1960s idealism of his work
and his personal life

584
00:42:16,800 --> 00:42:18,650
have waned somewhat.

585
00:42:18,700 --> 00:42:20,550
His relationship with his family

586
00:42:20,600 --> 00:42:23,750
was often strained by
his drive to succeed.

587
00:42:23,900 --> 00:42:27,050
His wife Jane, interviewed in 1989,

588
00:42:27,100 --> 00:42:28,850
said despite her dedication,

589
00:42:28,900 --> 00:42:33,850
she struggled to cope with someone
whose whole focus was physics.

590
00:42:33,900 --> 00:42:37,550
His determination has now
rather outstripped mine.

591
00:42:37,600 --> 00:42:39,450
I cannot keep up with him.

592
00:42:39,600 --> 00:42:43,150
I do think he tends to
overcompensate for his

593
00:42:43,200 --> 00:42:48,750
condition by doing absolutely
everything that comes to his notice.

594
00:42:49,200 --> 00:42:50,750
I'm not a scientist.

595
00:42:50,800 --> 00:42:55,350
I'm not an appendage of Stephen,
as I very much feel I am.

596
00:42:55,400 --> 00:42:58,550
When we go to some of these
official gatherings, I mean,

597
00:42:58,600 --> 00:43:01,550
sometimes I'm not even introduced
to people.

598
00:43:04,000 --> 00:43:08,650
Hawking's dedication to his science
came with a personal cost.

599
00:43:08,700 --> 00:43:12,950
By 1985, just before his meteoric
rise to fame,

600
00:43:13,000 --> 00:43:15,950
the Hawkings' marriage
was under considerable strain,

601
00:43:16,000 --> 00:43:18,350
and the couple were drifting apart.

602
00:43:22,200 --> 00:43:24,250
Jane took her family on holiday,

603
00:43:24,300 --> 00:43:28,550
while Hawking went on a working trip
to Switzerland alone.

604
00:43:31,000 --> 00:43:35,550
But as he was visiting
the huge particle accelerator
at CERN, near Geneva,

605
00:43:35,700 --> 00:43:39,050
Hawking suddenly contracted
severe pneumonia.

606
00:43:40,000 --> 00:43:42,150
It seemed he might not make it.

607
00:43:42,300 --> 00:43:44,450
Jane rushed to his side.

608
00:43:44,700 --> 00:43:48,050
For days, he struggled
on life support.

609
00:43:48,300 --> 00:43:52,450
But with characteristic stubbornness,
Hawking pulled through.

610
00:43:52,500 --> 00:43:54,850
He'd needed a tracheostomy,

611
00:43:54,900 --> 00:43:58,850
which meant he completely lost
his ability to speak unaided.

612
00:43:59,100 --> 00:44:02,350
The famous voice box
followed soon after.

613
00:44:02,400 --> 00:44:04,450
Then came the book.

614
00:44:04,500 --> 00:44:05,750
Through it all,

615
00:44:05,800 --> 00:44:10,250
Hawking's eye was,
and still is, on the prize.

616
00:44:10,500 --> 00:44:12,650
The theory of everything.

617
00:44:17,100 --> 00:44:18,550
Nevertheless,

618
00:44:18,600 --> 00:44:22,150
even though the job has been more
difficult than one might have hoped,

619
00:44:23,200 --> 00:44:25,950
I think there is still
every indication

620
00:44:26,000 --> 00:44:29,550
that there is a final theory
and that we may get there,

621
00:44:29,600 --> 00:44:33,050
but it just proves much more
complicated than we originally hoped.

622
00:44:34,400 --> 00:44:37,150
It is, after all,
the toughest job in science.

623
00:44:37,300 --> 00:44:41,650
Hawking's trying to peer back
to 13.7 billion years ago,

624
00:44:41,700 --> 00:44:43,650
to the start of everything.

625
00:44:43,900 --> 00:44:47,350
His main stumbling block has been
getting the theory to explain

626
00:44:47,400 --> 00:44:50,450
what the entire universe
was like back then,

627
00:44:50,500 --> 00:44:54,650
when it was all compressed
to a size smaller than an atom.

628
00:44:55,200 --> 00:44:57,150
Although the universe
is very big now,

629
00:44:57,200 --> 00:45:01,250
the observable universe
is something like 13,000
million light years,

630
00:45:01,300 --> 00:45:04,150
the distance light
has travelled since the Big Bang,

631
00:45:04,200 --> 00:45:06,750
we know that that entire region

632
00:45:06,800 --> 00:45:10,350
must once have been compressed
into a very, very small scale.

633
00:45:10,500 --> 00:45:15,050
But, of course, once the universe
is compressed into a very small scale

634
00:45:15,100 --> 00:45:16,950
or a very high density,

635
00:45:17,000 --> 00:45:20,450
we know we are in the domain
of quantum theory.

636
00:45:21,500 --> 00:45:23,350
Using the theory of the tiny,

637
00:45:23,400 --> 00:45:25,250
Hawking has made huge progress

638
00:45:25,300 --> 00:45:28,250
in describing the birth
of the universe.

639
00:45:28,700 --> 00:45:30,950
But there is one part
that eludes him.

640
00:45:31,100 --> 00:45:33,350
He's found it impossible so far

641
00:45:33,600 --> 00:45:36,550
to describe how gravity
must have worked

642
00:45:36,600 --> 00:45:39,150
at the moment of the Big Bang.

643
00:45:40,800 --> 00:45:44,650
If we want to know what happened
when the universe began,

644
00:45:44,700 --> 00:45:49,850
we have to have a theory
that can describe gravity
on a very small scale.

645
00:45:53,900 --> 00:45:55,750
For the last 30 years,

646
00:45:55,800 --> 00:45:57,950
Hawking has struggled to find a way

647
00:45:58,000 --> 00:46:01,250
to describe gravity with quantum theory,

648
00:46:01,500 --> 00:46:03,750
but he has unshakeable faith

649
00:46:03,800 --> 00:46:07,750
that the theory of the tiny
will eventually win through.

650
00:46:10,800 --> 00:46:12,650
And he's not alone.

651
00:46:12,700 --> 00:46:16,250
Today all of physics
is racing along beside him.

652
00:46:16,300 --> 00:46:18,850
Incredible experiments
are now being built

653
00:46:18,900 --> 00:46:21,850
in outer space and deep underground,

654
00:46:21,900 --> 00:46:26,650
which will try to probe deeper
into the very moment of creation.

655
00:46:26,800 --> 00:46:28,650
There is excitement in the air,

656
00:46:28,700 --> 00:46:33,450
a sense that the problem
of gravity in the early universe
will be solved,

657
00:46:33,500 --> 00:46:37,750
and that a theory of everything
is just waiting to be found.

658
00:46:38,200 --> 00:46:40,450
Whether he finds it first or not,

659
00:46:40,600 --> 00:46:45,450
Hawking is philosophical about
his part in this great journey.

660
00:46:46,300 --> 00:46:49,650
I was unlucky to get
motor neurone disease,

661
00:46:49,700 --> 00:46:52,750
but lucky in almost everything else.

662
00:46:54,200 --> 00:46:56,950
I have three very attractive children,

663
00:46:57,000 --> 00:46:59,450
success in my scientific work

664
00:46:59,500 --> 00:47:03,750
and a real sense of satisfaction
at having achieved all of this,

665
00:47:03,800 --> 00:47:06,250
despite the difficulties.

666
00:47:06,600 --> 00:47:09,450
Not many people can say this.

667
00:47:11,100 --> 00:47:13,350
Is there anything you wish
you'd achieved professionally

668
00:47:13,400 --> 00:47:15,250
that you haven't already?

669
00:47:18,100 --> 00:47:20,950
I feel I have achieved quite a lot,

670
00:47:21,000 --> 00:47:24,250
but one would always
like to have done more.

671
00:47:24,500 --> 00:47:28,650
In particular, I would like
to have found a complete theory

672
00:47:28,700 --> 00:47:32,350
of quantum gravity
in the early universe.

673
00:47:32,700 --> 00:47:37,650
Still, that wouldn't have left
much for anyone else to do.

674
00:47:39,000 --> 00:47:44,650
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