Stephen Hawking's Universe (2010–…): Season 1, Episode 3 - The Story of Everything - full transcript

Hello!

My name is Stephen Hawking...

Physicist, cosmologist...

And something of a dreamer.

Although I cannot move...

...And I have to
speak through a computer...

In my mind, I am free...

...Free to tour the universe

And tell the ultimate story...

The story of everything
there ever was...

...From the moment
the cosmos began...



To the creation of our world
and everything in it...

And beyond,
to the far, far future

And the end
of the universe itself...

A journey through all of space
and all of time.

Check it out.

I spend a lot of time
thinking about the universe,

But I never get bored.

After all, it's a pretty
extraordinary place.

This is the cosmos...

At a very large scale.

Each tiny point of light
is an entire galaxy,

Each a cluster of as many
as 400 billion individual stars.

This view of the universe
is only possible

Due to the latest
supercomputers.



I find it
indescribably beautiful...

Uncountable billions of galaxies
forming a vast web

Stretching away
in all directions.

What's more,
I never get over the fact

That within
this massive universe

Lies one perfectly ordinary
spiral galaxy.

Inside that galaxy exists
a commonplace yellow star...

...Orbited by eight planets.

On one of those planets
lives a species

That has only just worked out

What a remarkable place
the universe is.

Us.

We've discovered more about
the cosmos in the last century

Than in all previous
human history.

Finally, we are solving
the basic mysteries

That have perplexed
our ancestors

For at least 200,000 years.

What I like above all
is that the facts themselves

Are both breathtakingly elegant
and surprising.

We're living
just as it dawns on us

That the earth
and everything around us

Was made by the stars.

Boiling furnaces of hydrogen gas
like our sun

Made even the atoms
in your eyelashes.

We've worked out
that the universe

Is almost
unimaginably ancient...

About 14 billion years old...

And that it will continue
to exist

For at least twice that long.

But without a doubt,
the most remarkable fact of all

Is that the entire
enormous universe,

All the innumerable galaxies,

Even time and space and the
forces of nature themselves

Simply materialized
out of...Nothing.

So now is a good time
to be alive, I think.

We may only be
an advanced breed of monkey

Living on a small planet,

But we are able to contemplate
the universe as a whole,

Which makes us very special.

My goal has always
been simple...

To work out
how the universe works

And why it exists at all.

Luckily,
there are clues everywhere,

And the most important one
is right above our heads.

Examine any patch
of the night sky,

Even one as small
as the head of a pin,

And this is what you'll find...

A tiny part
of the vast web of galaxies.

It's less than a millionth

Of what we can see of the cosmos
from our little planet,

But even this tiny sample
is enough to find a clue,

The key to the past,
the present,

And perhaps the future, too.

The clue is that,
seen from earth,

All these distant galaxies
are slightly red in color.

They appear almost as if

We were looking through
rose-tinted glasses.

It's this very redness

That reveals
how the universe was born.

And to show you why,

I need a straight road
and a noisy car.

Listen to the sound
as it passes by.

As the car approaches,
the pitch of its engine rises.

As it goes away,
the pitch of its engine...

Falls.

This phenomenon
is called a doppler shift,

And the exact same thing
happens with light.

If our eyes were
more sensitive to color,

We could see that the car

Is actually very slightly blue
as it approaches...

...And very slightly red
as it goes away.

The same rules apply in space.

All distant galaxies
are slightly red in color,

So by the exact same piece
of basic physics,

They must all
be moving away, too.

In fact, the whole universe
is expanding...

In all directions...

Getting bigger and bigger,
like a balloon inflating.

I admit this sounds strange,

But to cosmologists,
it's like winning the lottery,

Because, to work out
where the universe came from,

Alwe need to do
is to stop time

And make it run in reverse.

Rewind far enough,

And everything gets
closer together...

.Lot closer together.

All the galaxies...

In fact, every single thing
converges to a single point,

The start of everything,

13.7 billion years ago.

So it's quite simple, really.

Follow the clues,

And we can deduce
that a very long time ago,

The universe simply burst
into existence,

An event called the big bang.

But I'm afraid
we have to stop a moment...

Before we get carried away
by fire and noise.

At the very beginning,

The big bang actually happened
in total darkness,

Because light didn't exist yet.

To see it, we'd have needed some
kind of cosmic night vision.

But even this,
a view from the outside,

Is impossible.

Again, it sounds strange,

But space didn't exist then,
either.

So there was no outside.

The only place there was
was inside.

This early universe was
a very strange thing, indeed.

There's still much I'd
dearly love to know about it,

But standard concepts of time
or space don't really apply.

It was just a very tiny,
ultra-hot fog of energy.

Then it expanded...

...With a tremendous flash
of radiation...

From smaller than an atom
to about the size of an orange

In less than a trillionth
of a second,

Almost no time at all.

The universe simply inflated
into existence,

Unfolding, unfurling,

Getting bigger and cooler
with every passing moment.

Within 100 seconds, it was
as big as our solar system,

Trillions of miles across.

While this was happening,

The pure energy of the cosmos
began to cool and create matter

In the form
of countless trillions

Of subatomic particles...

The first stuff there ever was.

Half these particles
were made of matter,

The same kind of stuff
which makes us.

The rest were made
of the opposite of matter,

Stuff called antimatter.

When the two meet, they destroy
each other in a flash of energy.

It seems as if
building a universe

Is a pretty wasteful process.

Fortunately, there was
just a bit more matter

Than antimatter.

Just one in a billion particles
of stuff survived...

...Which was lucky for us,

Because that residue

Is what our present-day universe
is made of.

You could say we are made
of the smoke of the big bang.

By the time the cosmos
was 10 minutes old,

It was already thousands
of light-years in diameter.

After that,
everything spread out and cooled

For about 330,000 years,

When, finally, the fog cleared

And the universe became visible.

So, that's how everything
got going,

Which I think is
a pretty fantastic story

And probably much stranger

Than anything our ancestors
came up with

By way of an explanation.

But the next thing
that happened...

Well,
that's pretty spectacular, too.

This is the universe
seen in extreme fast-forward,

All 14 billion years
in less than a minute.

It shows how the universe
changed from a cloud of gas

Into a place filled with perhaps
100 billion galaxies,

Swirling
in a vast chaotic dance.

What I love to get people
thinking about

Is that all this
had to be built atom by atom,

Celestial engineering
on a spectacular scale.

So, what drove
this cosmic clockwork?

I'd say it was
the force of gravity.

The idea of gravity was worked
out by sir isaac newton...

...Who had the same job as me
here at cambridge university

Back in the 17th century.

It supposedly dawned on him
when an apple fell on his head.

The apple helped him realize

That all objects
attract each other.

And the greater the mass,
the stronger the pull.

These apples
are attracted to the earth,

And although you can't see it,

The earth moves very slightly
up towards the apples.

All things come together
through the power of gravity.

Gravity was created
in the big bang

And has been at work
ever since.

It's what keeps
you, me, and apples

Stuck to the earth.

In the early universe, gravity
had a much bigger to play.

Right after the big bang,

The universe was just gas,

Almost perfectly spread out
throughout space.

Over the next 200 million years,

Gravity began to pull the gas
back together

To produce
the very first structures

From which everything else
would grow.

But even this
very nearly didn't happen.

If it weren't for another stroke
of cosmic luck,

There would be no you, no me,

No stars or planets
or anything at all.

We know this because, in 1982,

A group of scientists,
including myself,

Spent three solid weeks
working it out.

Although the calculations
were hard,

Demonstrating what we discovered
is easy.

First, I need a nice flat floor,

Like this one, for example.

This is the dining room
in my college.

I'm going to fill the place with
lots and lots of ball bearings.

These balls represent the matter
of the early universe,

A thin gas spread out evenly
across the vast cosmos.

Here's where luck comes in.

If they're all
the same distance apart,

Gravity pulls each ball the
same amount in all directions.

They stay perfectly aligned,
and precisely nothing happens.

Fortunately, one of
the basic rules of the universe

Is that nothing's perfect.

Perfection simply doesn't exist.

The early universe
had a tiny unevenness

That can be simulated
by removing

Just five ball bearings.

It may not look
like much has changed,

But to gravity,
those missing balls

Create a giant opportunity.

Gravity now pulls more strongly

On one side
of some of the bearings.

The tiny irregularities
in the sea of ball bearings

Have given gravity something
to sink its teeth into.

And this
is exactly what happened

Back where we left
the young universe.

Parts of the sea of early gas

Were ever so slightly thinner
than others.

The less dense areas

Were like the gaps
between the ball bearings.

The denser parts
of the sea of gas,

Where gravity
was having its way,

Clumped together.

And it was in these areas

That all the stars and galaxies
would fall.

The cosmos had taken
its first step

Towards the beautiful place
it is today,

All thanks to irregularity,
imperfection,

And lack of order.

So next time someone complains
that you have made a mistake...

...Tell him,
"that may be a good thing

"because without imperfection,

Neither you nor I would exist."

13.5 billion years ago,

The universe was mostly
hydrogen gas,

With gravity doing
what gravity does,

Which is to slowly pull it
into vast clouds.

Hydrogen is the simplest
of gases,

But it has
a very special property.

It's a tremendous
source of power.

Heat hydrogen
to around 10 million degrees,

And it begins to produce
the energy

That makes the stars shine...

And supplies the universe
with warmth and light.

To see how this works,

Let's imagine we can make
a small star here on earth.

First, we need plenty
of hydrogen gas,

About a sports stadium full
would be perfect.

Next, we need to imagine

Squishing
this hydrogen together,

Just as gravity does in space.

As the hydrogen compacts,

The atoms of gas start
bouncing off each other,

And the temperature
begins to rise.

By the time it's compressed down
to the size of the soccer ball,

The hydrogen reaches the
critical 10 million degrees...

...And a process
called nuclear fusion begins.

The hydrogen starts
to fuse together,

Making a new,
heavier material...

Helium.

With every step
of this tiny bump and grind,

Some matter gets converted
into pure energy.

We have created
a miniature star.

Of course,
if this was a real experiment,

You wouldn't want to go
anywhere near it.

The energy given off
even from a star this small

Would be devastating.

Back in the early universe,

The same process happened
for the first time

On a much, much bigger scale.

Gravity compressed
the hydrogen gas clouds

Over millions of years,

Until, deep in the center,

The hydrogen became hot enough
for fusion to occur.

The first star
burst into life...

...Pouring its energy
into the vast universe,

A product of the laws of nature

And the raw materials left over
from the big bang.

It was almost 1,000 times bigger
than our own sun

And burned a deep blue.

What's more,
this star soon had company.

The stars were turning on.

This same process still happens
in our sun,

Which is where we get
the energy we need to live.

But there was still
a long way to go

To get from this
to where we are today.

You can't build
a world like ours

From simple gases
such as hydrogen and helium.

You need all sorts
of other elements.

You need elements like oxygen
and carbon and iron

And many more.

But we got lucky yet again,

Because the very same process
that causes the stars to shine

Also just happens
to make materials

Like oxygen and carbon and iron.

Stars, simply by accident,
are giant factories.

To see a star in action,

Let's imagine
I can split one in half.

Just as in the soccer-ball star,

The hydrogen atoms
are fusing together,

Creating helium, which produces
the star's energy.

But helium is slightly heavier
than hydrogen,

So it sinks
to the center of the star.

And now the helium atoms
take center stage.

As they fuse together,
they produce even more energy

And form yet another
new element...

Carbon...

A vital building block
of every living thing.

The process repeats itself
over and over,

And the star becomes layered,
like an onion...

A really big onion.

The closer to the center,
the heavier the elements,

Like neon, oxygen,
and last of all, iron.

Now things change.

Iron doesn't produce energy
when it fuses,

So the fire begins to go out.

More and more iron builds up
in the star's core

Until almost all
the remaining fuel runs out.

Now gravity takes over and
squashes the star in on itself.

As its core gets
more and more compressed,

Its temperature soars

Until it's over 100 times hotter
than the core of our own sun.

Finally, the star collapses
and explodes.

This is a supernova...

...The death of a star
and the birth of something new.

In these brief microseconds,

A massive shock wave
passes through the star.

The blast is so powerful
that it forces some of the iron

To fuse
into even heavier elements.

And that's how heavy elements,

Such as gold or platinum
or lead,

Are made, forged in the heart
of an exploding star.

So, if you have a gold ring,
make sure you appreciate it.

The metal was made
in a blinding flash of light

Billions of years ago,

The finale of the process

That produced the elements
all around us today.

It never ceases to amaze me...

...That our bodies
are constructed

Of the stuff of stars

And that our hearts beat
because of the energy

Given off
as those materials are made.

But as magical as the star is,

There are even more fascinating
and powerful things

In our enormous cosmos.

Around 300 million
years after the big bang,

The early stars
began to form galaxies,

Which slowly took on

A bewildering variety
of shapes and sizes.

Our galaxy, the milky way,

Is thought to be
one of the oldest,

Having started
to assemble itself

Some 13 billion years ago.

It's roughly
6,000 billion miles in diameter

And contains something like
200 billion individual stars.

Nobody's quite sure
exactly how many,

Since they can't all be seen
from earth,

And, anyway, it would take
a long time to count them.

Because all these stars
were built by gravity,

You could say gravity's
the hero of the universe.

After all, it turned
a meaningless soup of gas

Into something of beauty
and power.

But like all interesting heroes,

Gravity has its dark side.

Right in the center
of our galaxy

Lies an example of what happens
when gravity rules unchallenged.

A black hole.

When I was in my 20s...

...I did some of the basic
mathematics of black holes,

But few people shared
my fascination.

These days,
they are a popular subject.

Physicists all over the world

Are studying
black-hole behavior.

We now know that black holes

Are not only fascinating
in their own right,

But that they play
a fundamental role

In the formation of galaxies.

They also give us a glimpse
of how the universe may end.

A black hole forms
when a large star...

One, say, 20 times
the mass of our sun...

Comes to the end of its life.

Such a star looks
nothing like our sun

Because it's become unstable,

Convulsing violently
as its death throes begin.

Finally, it runs out of fuel
and begins to shrink,

Getting denser and denser,
hotter and hotter.

But with a star this massive,

There is no force
in the universe

Capable of stopping
the collapse.

The core is so heavy

That it just keeps on
falling in on itself.

Gravity is running wild.

In just 15 seconds or so,

The unstoppable force
crushes the star

From millions of miles
in diameter

To as little
as 12 miles in diameter.

All the mass that was
in the star is still there,

But its own weight
keeps forcing it down

Smaller and smaller still.

The temperature of the core
sores to 100 billion degrees.

The outer layers are blasted
away in a massive supernova,

But deep in the center,

The core falls down what we call
a gravitational well.

It crushes itself
into a single point.

A black hole is born.

Nothing nearby can escape
its pull, not even light.

It's hard to imagine just
how dense a black hole can be.

But I'll try and put it
into perspective

Using something familiar...

The earth.

Imagine, piece by piece,
I could compress our planet

And crush it
until gravity took over...

And it became a black hole.

How small would it have to be

To vanish down its own
gravitational well?

From 8,000 miles in diameter,

I'd have to crush it
to the size of a pea.

In my years
studying black holes...

...One of my most
unexpected discoveries

Was that a black hole
cannot be perfectly black.

For much the same reason...

...As the early universe

Could not have been
perfectly spread out.

There is no such thing
as perfection.

Black holes
must give off radiation.

The smaller the black hole,
the grter the radiation.

An even tinier black hole,

With only the mass
of a mountain range,

Would actually shine.

Out in space, most black holes
are much larger.

The smaller ones have around
four times the mass of our sun

And are 15 miles in diameter.

Some are much larger,

Containing the mass
of thousands of suns.

And then there are
the really big ones...

Supermassive black holes...

That exist at the centers
of galaxies like our own.

This black hole

Is thought to have the mass
of 4 million suns

And a diameter
of 11 million miles.

Black holes like these
are the heavy hubs

Around which many galaxies,
including the milky way, rotate,

A kind of stabilizer
that gives them form and shape.

So, 8 billion years
after the big bang,

After a long and remarkable run
of good luck,

We have stars
and we have galaxies

Slowly rotating
around giant black holes.

Now the scene is set for
something close to our hearts...

The formation of our sun,
the earth,

And, ultimately, us.

Our solar system,
the place we call home,

Lies about 26,000 light-years
from the center of our galaxy,

The milky way...

Or around 2/3 of the way out.

The story of how
these huge planets

Came to be orbiting
an average yellow star

Is 6 billion years long,

And since we don't have
that much time,

I'll speed it up a bit.

It starts with a bang.

Long ago,
an ancient star exploded,

Littering space
with swirling clouds

Of the materials
it had made while it lived

And the heavier metals
it created as it died.

We know this because we can see
similar fields of dust

Out in space today.

They are called nebulae,

And they are very beautiful.

Every nebula is different,

And in our case,

The clouds contained nitrogen
and oxygen and iron and silica

And all the other stuff needed
to build a world like ours.

Then the tireless force
of gravity

Started to pull it all
back together,

And the heavy engineering
that produces planets began.

Vast swirls of dust
began to form,

And at the center
of one of these,

A rocky planet called earth
started to take shape...

...Built of stardust
and assembled by gravity.

Fast forward 100 million years,

And it had grown
into a giant ball,

Sweeping up billions of tons
of celestial debris.

This is where
the earth came from

And, therefore,
how you and I began.

But our planet would have
remained a large, sterile ball

Of rock and metals
and minerals forever

Were it not for one more event,

One more expression
of the forces of nature.

93 million miles away,

At the heart
of the giant nebula,

The pressure and temperature
of a ball of hydrogen gas

Had become so great that the
atoms were beginning to fuse.

A new star, our sun,
was coming to life.

As the sun ignited,

It gave off a huge blast
of solar wind,

A radioactive gust of energy.

This blew all
the remaining dust and gas

That was left over
from the nebula

Out to the edge
of the solar system,

Which is why everything
is nice and orderly today.

In the outer reaches
of the solar system,

We have the huge gas planets...

Jupiter...Saturn...

Uranus...And neptune.

Further in are the denser,
rockier planets...

Mercury...

Venus...

Mars...

And, of course, the earth.

Lucky for us, the sun
is 865,000 miles in diameter,

Or just the right size
to burn consistently

For a very long time...

8 billion years...

Long enough to allow the next
development to take place...

Life.

Life is one of
the strangest phenomena known.

In my opinion,

It shows that the universe
is capable of almost anything.

Yet it amazes me
that we can know so much

About how the universe began
many billions of years ago,

But we have yet to discover
how life itself began.

The most likely explanation

Is probably
that we are an accident.

Just by chance,

Some molecules
bumped into each other at random

Until, finally, one formed
that could copy itself.

Then began the slow process
of evolution

That led to all
the extraordinary diversity

Of life on earth.

Life seems to be
simply what matter does,

Given the right conditions
and enough time.

I think that life

Is probably quite common
throughout the universe,

But that's another tale
altogether.

As life developed, it changed
the planet on which it was born,

Altering the very fabric
of the earth.

After 4 1/2 billion years,

The human race
arrived on the scene.

But one thing
often troubles people...

...When they hear this story.

How could such
an astounding chain of events,

Which resulted in us,
be an accident?

Perhaps science has revealed

There is some higher authority
at work,

Setting the laws of nature

So that our universe
and we can exist.

On the face of it,
life does seem

To be too unlikely
to be just a coincidence.

Think about it.

The earth lies at exactly
the right distance from the sun

To allow liquid water
to exist on its surface.

And the sun just happens
to be the right size

To burn for billions of years,

Long enough for life
to have evolved.

The solar system is littered

With all the elements
needed for life.

These elements themselves
are only possible

Because of older stars
that have burned up.

These older stars only existed

Because of a tiny unevenness
in the early primordial gas...

That was itself produced
by a one-in-a-billion imbalance

In the sea of particles
that came from the big bang.

So is there a grand designer

Who lined up
all this good fortune?

In my opinion, not necessarily.

Look at it this way.

What if there were
other universes,

Ones not as lucky as ours?

Each of these universes

Could have come
from its own big bang,

With different laws of physics
and different conditions.

In some,
gravity might not exist,

And there could be no life.

In others,
hydrogen might not fuse,

So there would be no stars
and, again, no life.

And for any number of reasons,

Universes could have
come and gone

Without producing
ything at all.

So perhaps we should not be
too surprised

To find ourselves
in a perfect universe

Orbiting a perfect sun

On a perfect planet,

Because such perfect places

Are the only ones
where life like us can exist.

We are one of the many products
of the universe,

The result of an ancient
and elegant mechanism.

But even this
remarkable discovery

Is only just the beginning
of what physics can tell us.

We can find out what human kind
will face in the distant future.

And, ultimately,

We might discover the fate
of the universe itself.

One reason I love cosmology

Is that it tells us
not only where

The vast web of galaxies
in our universe came from,

But also what lies in store

For both the universe
and for us.

I think it's pretty exciting

To be among
the first human beings

Able to look forward

For hundreds
and even billions of years,

Maybe as far
as the end of time itself.

What I see
is not only the future

Of the cosmos we inhabit...

...But also
the enormous challenges

Our species will face.

After all,
we are puny organisms

Compared to the mighty universe
that made us.

The earth that gave us life
will not always be

The blue sanctuary it is today.

The continents
of our planet are drifting.

Fast forward 75 million years,

And they will be clustered
towards the south pole.

No one knows if the earth
will still be habitable then,

But the sad truth is

That we may not last long enough
to find out.

As we gaze into the future,

It turns out that the universe
is a pretty dangerous place.

Just look at our neighborhood.

It's littered
with billions of asteroids,

Ancient remnants left over

From the process
that built the solar system.

The possibility of one of these
wiping us out

Isn't just the stuff
of hollywood disaster movies.

The threat from asteroids
is real.

We've even given
some of them names.

This one is called apophis,

After a mythical egyptian demon,

A god of darkness
and destruction.

Discovered in 2004,

Apophis is the size
of a 100-story skyscraper.

It weighs about 20 million tons.

Speeding through space
at 28,000 miles an hour,

10 times as fast as a bullet,

It carries almost as much energy

As all the world's
nuclear weapons combined.

And we know roughly
where it's headed.

The precise path
is not yet fully known.

But on April the 13th, 2029,

This huge rock is likely to pass

Within 23,000 miles
of the planet's surface,

Close enough to pass

Beneath satellites in orbit
around the earth

And give us all a scare.

Luckily,
there is very little chance

That apophis
will actually hit us,

But the problem for humanity
is that in space...

There's always a bigger rock.

There thousands of really large
asteroids out here.

Some are over 10 miles long...

The size of manhattan.

An asteroid this size
hits the earth

Every 100 million years or so.

The last one struck the earth
65 million years ago

And probably was responsible
for wiping out the dinosaurs.

We don't know when
the next asteroid will strike,

But if it was big enough,
it could sterilize our planet.

That would be the end

Of the 5 billion-year-long story
of life on earth.

But even if we avoid
such a natural catastrophe,

We could all too easily end up
destroying ourselves.

In the last 10,000 years,

Humans have come
to dominate the planet.

We're so successful

That it's tempting to think
we are evolution's grand prize.

But I believe intelligence
is probably overrated.

It's not necessarily a good
thing for a species's survival.

Bacteria have managed without it
for over 3 billion years.

Intelligence,
at least in our case,

Leads to technology.

And there are many ways
technology could wipe us out...

The most obvious, of course,

The threat from nuclear weapons.

Even if the risk of a nuclear
war happening in one year

Is miniscule...
say only one in a million...

If we run those odds
over 100,000 years,

The chance of catastrophe
falls to one in 10.

Personally, I worry that even
this might be overoptimistic.

Although we are clever enough
to have designed such weapons,

I'm not sure we are
clever enough not to use them.

As time marches relentlessly
into the future,

The universe has
other surprises in store.

There are some powerful things
out there...

...Some of which
could destroy the earth

Without any help from us.

As the universe
continues to dance

To its ancient rhythm,

Stars will come and go
in a relentless cycle.

And because there are
hundreds of billions of stars,

There's always one dying
in a supernova somewhere.

In our galaxy, for instance,

A star dies
every 50 years or so...

Which is but the briefest
of moments to the universe.

It's just about conceivable

That a supernova
could damage the earth,

If you consider the likelihood
over a long enough time scale.

One kind of supernova,
discovered entirely by accident,

Is thought to be
particularly dangerous.

In 1967, when the cold war
was at its height,

U.S. Military satellites
picked up a massive burst

Of something called
gamma radiation.

Gamma radiation

Is the most dangerous type
of radiation known.

It's also the telltale sign
of an atomic weapon.

Were the gamma rays detected

Evidence of a new
and powerful soviet bomb?

Thankfully, the answer was no.

After careful analysis
of the data,

They discovered that
the sudden bursts of gamma rays

Were actually coming from space.

Not even the russians
had that kind of technology.

Decades later,
we still don't have proof

Of what causes
the bursts of radiation.

But there's
a well-respected theory

That they are produced
by a special kind of supernova

Called a gamma-ray burster.

What's more,
there might be one quite nearby.

Hidden within this massive
spiral plume of plasma,

8,000 light-years from earth,

Is a star called wr 104.

Deep inside the star itself
is a bright sphere

Throwing off a shell of hot gas
as it nears its end.

If this star
is what we think it is,

Then as it dies,

It will produce two tightly
focused beams of radiation,

One from each pole.

The star destroys itself
as it produces these beams,

Which contain more energy

Than our sun will produce
in its entire life.

The brightest known phenomena
in the entire universe.

No one is sure if wr 104
will do this

Or if the beam
would strike the earth,

But if so, we could be bathed
in high-intensity radiation...

...With some devastating
consequences.

The beam would cause
spectacular auroras,

Stripping the ozone
from the atmosphere,

Allowing deadly radiation from
the sun to strike the earth.

It may sound like
science fiction,

But this could be
the second time

Skies like these have been seen
on our world.

450 million years ago,

Over half
of all living creatures

Were wiped out
in a great extinction.

One explanation
is that a gamma-ray burster

Irradiated the planet so badly

That earth's ecosystem
virtually collapsed.

I don't want to worry anyone,

But I think
it's definitely a good idea

For the human race
to venture far beyond the earth.

We would be wise
to keep our eggs...

...In as many baskets
as possible.

Thankfully, that process
has already begun.

In my opinion,
the launch of apollo 11

Is probably the most important
moment in human history.

It was a turning point
for the universe, too.

Life, in the form of us,
escaped its home planet...

And stepped on another surface.

The astronauts' footprints
stand preserved to this day...

...A testament to the beginning
of what I think

Could be the next chapter
in the story of the cosmos...

The spread of life
to other parts of the universe.

As the universe gets older,

We will have to get wiser.

I think we'll have to go
much further than the moon...

At the very least, to mars.

The red planet is likely to play

An important part
in our evolution,

And maybe even
in the story of the cosmos.

It's the second

And possibly the most important
stepping stone

On humanity's journey
to the stars.

Robot missions to mars

Have revealed
a spectacularly beautiful

Yet dangerous
and desolate place.

I imagine that being
a human pioneer here

Would be an exciting business.

For a start, it's cold.

It's 50 million miles further
from the sun than the earth,

And so it receives
half as much warmth,

And the temperatures
fluctuate wildly,

From 80 degrees...

To minus 200
in a matter of minutes.

If the cold doesn't get you,
the low gravity will.

Mars is just
half the size of the earth

And has just 38% of its gravity.

Over time,
explorers' bones would weaken,

And their muscles
would waste away.

Spend long enough on mars,

And you could find yourself
too weak

To safely return to earth.

The low gravity also means

Mars struggles to hold on
to an atmosphere.

Here, there's nothing more than
a thin wisp of carbon dioxide

At just 1/100 the pressure
of our air.

Mars is also bathed in harmful
radiation from the sun.

Even though it's further away,

Unlike earth,
it has no magnetic field

And no ozone layer
to protect it.

Early explorers
would have to be careful

To minimize their exposure.

Perhaps they'd even
have to live underground.

But one day,
I think it'll be possible

To drastically alter
conditions on mars,

Perhaps using
space-borne mirrors

To supply warmth and power.

With perfectly foreseeable
technology,

Much more could become possible.

If we could erect giant domes
made of glass and plastic

To block out the radiation,

Inside them,
we could enrich the atmosphere.

500 years from now...

Which really is
a very short time, indeed...

I think mars will have
its own language,

Its own currency,
it's own cuisine...

Although I'll bet you

You'll still be able
to get a hamburger somewhere.

But it's clear that,

As the universe
continues to age,

Even advances like these

Will not be enough to guarantee
humanity's existence

For a very long time.

Look further into the future,

And ultimately our solar system
will follow the same path

As countless billions
of solar systems before it

And cease to exist.

Right now, the sun is
in the middle of its life cycle.

During this phase,

It is getting gradually
hotter and brighter all the time

By about 6% every billion years.

In about 5 billion years,

The sun's temperature
will have grown

To nearly 200 billion degrees.

At this point, the earth will be

An unrecognizable ball
of molten rock,

All life
having long since perished.

This is our planet's
unavoidable destiny,

But that's not all
the sun has in store.

As it runs out of fuel,
the sun will start to expand,

Turning into what's called
a red giant.

It will change from being
the object that gave us life

To the one that annihilates it.

In about 7 billion years,

The sun will be
200 times bigger,

About 200 million miles across.

So vast, it will obliterate
the inner planets

One after the other...

Mercury, venus,

And most probably
the lifeless earth.

But as the universe
continues to evolve...

...At its own relentless pace,

New opportunities
will present themselves to us,

If we are able to preserve
the life that the cosmos made.

This is gliese 581d.

It's a large, rocky,
earth-like planet,

The nearest known.

It's just possible
that this world or one like it

Could, in the future,
become home to the human race,

A second sanctuary against the
unforgiving blackness of space.

Discovered in 2007,

It's seven times bigger
than earth.

It orbits a star smaller
and redder than our own,

But it lies at just
the right distance from its sun

To allow water to exist
on the surface.

But even if this is
the perfect home away from home,

There is a fundamental problem
we will have to overcome.

Gliese is
a very, very long way away...

...More than 20 light-years
from earth.

That's 120 trillion miles.

To get some idea
of this extraordinary distance

And the challenge it presents,

I'm going to imagine
that we could hitch a ride

On the fastest man-made object
in existence.

Voyager was launched in 1977.

Now over 30 years old,

It's traveled
more than 13 billion miles.

Its mission so far has taken it
to jupiter and saturn.

By using their gravity
to boost its speed,

The little spacecraft
has entered the record books.

It might not look fast,

But voyager is racing through
space at 11 miles a second.

On earth, 11 miles a second
looks like this.

It's 39,000 miles an hour.

At this speed,

We could circle e globe
1 1/2 times in an hour.

So, how long
would it take a spaceship

Traveling at voyager' speed

To get to the nearest
earth-like planet, gliese?

The answer reveals
the true scale of the cosmos...

...For even traveling
at 11 miles a second,

The journey to gliese

Would still take
over 350,000 years.

I think we have a chance

To become a lasting part
of the ever-changing universe

And to discover what
other wonders it might hold,

But to do this,

We will have to develop
new technology

On an enormous scale.

And that's going to take
some serious engineering.

There are many
in the field of cosmology

Who believe, as I do,

That finding ways
to travel great distances

Will be essential

To keeping humankind alive
in the universe.

If we could build a machine

Capable of traveling
to other solar systems,

We'd open up
a fascinating possibility...

The survival of the human race
for billions of years.

Present-day engineers
have begun thinking

About the principals
of building such a ship.

This is what it might look like.

It could use atomic energy

Or perhaps more exotic fuel,
such as antimatter,

Supplying it
with enormous amounts of power,

Yet I think the main challenges
won't be technical.

The first will be financial.

The cost of constructing
an interstellar spacecraft

Would be huge,

And for the society
that made it,

There would be little payback.

They would never see it again.

So constructing such a machine

Will either be the greatest act
of generosity in history,

Or it will have to be funded
by the travelers themselves.

And that raises
the second problem.

Even if it could travel
mind-numbingly fast...

Say 1,000 times faster
than voyager,

11,000 miles a second...

A journey
to the nearest star system

Would still take...

73 years.

Such a long trip means

That at least one whole
generation of humans

Would have to live
their entire lives in space,

And we couldn't exactly say they
had volunteered for the mission.

The ethics of sending a
human cargo on such a voyage

Would have to be
carefully considered.

Unless we could extend
human life spans

To long enough
to make such massive journeys.

And that, I think, is what
we will ultimately end up doing.

The process has already begun...

...As I know
from personal experience.

My muscles no longer function,

Although my eyes and my brain
are still working pretty well.

But technology helps me
to move and communicate.

In the future,

Technology will do much more
than that for all of us.

Within the next 1,000 years,

We will see
unprecedented changes

In our physical capabilities.

Genetic engineering
will give us longer life spans

And greater intelligence.

Modifying our genes
could give us skin

That protects us
from radiation...

The ability to breathe
poisonous atmospheres...

Resistance to infection.

We may even develop

Sophisticated
artificial life-forms,

Using synthetic dna,

Custom-designed for
the challenges of space travel.

These advances would allow us
to survive long journeys

And inhospitable worlds.

I imagine a time
when our descendants

Spread to planets orbiting
other stars all over our galaxy

And perhaps further still,

Carrying their biological cargo

To solar systems
we have yet to discover.

Ships like this one

Could be designed
to split up and spread out.

A true diaspora of life

That would have started
with us.

As we journey
across interstellar space,

I'm sure that we will unlock
nature's deepest secrets.

My great hope
is that we will discover

How the universe will end

And solve
the ultimate mystery...

Why the universe
ever existed at all.

I once gave a lecture in japan,

Where I was asked not to mention
the end of the universe

In case it affected
the japanese stock market.

Well,
I don't know if or when...

...The universe will end,

But for those of you who are
nervous about your investments,

I think it's a bit early
to sell.

At 13.7 billion years old,

Our universe
is still in its youth.

The earliest date we
cosmologists think it could end

Is 30 billion years from now.

There's still
plenty of action to come.

Even long after our sun
has died,

New stars will be born,

Some of which will have
new planets around them,

Made of the same atoms
that make you and me.

Maybe we'll end up as part
of some future alien ecosystem,

Although that's probably
a bit of a long shot.

What's true is that we are only
the temporary custodians

Of the particles
which we are made of.

They will go on to lead
a future existence

In the enormous universe
that made them.

Certainly, gravity will continue
its tireless, incessant work.

It will go on shaping
the vast strings of galaxies

As it has
ever since the big bang.

Using supercomputers, we can
simulate how gravity, even now,

Causes galaxies
to be attracted to one another,

Resulting in vast,
slow collisions.

Our galaxy will merge
with its nearest neighbor,

The andromeda galaxy,

In around 3 billion years.

A slow-motion collision

That will take place
over 2 billion years.

The same process is happening
all over the cosmos.

Entire clusters of galaxies

Are constantly colliding
and reforming...

...Giant collisions

As trillions of stars
pull on one another,

Their vast masses
causing them to spin and dance.

Gravity is driving
the cosmic clockwork

As it has done
ever since the big bang.

This is what
the universe looks like

When we are released
from time on a human sle.

But will this cosmic whirlpool
go on forever...

As an endless maelstrom
of mass and energy,

Space and time?

What an extraordinary question
to even be able to ask.

I think the solution
lies back where we began...

With the big bang.

Ask yourself this.

What caused the expansion
or inflation of the universe

In the first place?

When we can answer that and
fully understand the big bang,

We will also learn
the fate of the universe.

The key to it all
is something called dark energy,

A mysterious form of energy
that pushes space itself apart,

Even as gravity
is making matter clump together.

It seems as if dark energy

Supplied the kick
that inflated the universe,

Although
we're not quite sure how.

What is certain is that
the fate of the universe

Depends on how
this dark energy behaves.

If the dark energy
slowly weakens,

Then gravity
could get the upper hand,

And in 20 billion years or so,

The universe
would go into reverse

And drive everything back
to whence it came.

In a strange reversal
of the big bang,

Space itself would contract.

This theory is known
as the big crunch.

In the end,
if the theory is right,

In 30 billion years from now,

All the matter of the universe

Would be swallowed
by a single black hole.

The entire universe would exist
as one tiny point,

Much as it was at the instant
of the big bang.

But although
that's a neat ending,

I think that it's more likely
that dark energy

Will drive the expansion
of the universe forever

And that, ultimately, everything
will just keep spreading out

Until the universe
is cold and dark.

Everything will become
so far apart

That even gravity
will be defeated.

I think a big chill
is what we've got in store,

Not a big crunch.

So will this be the end of us
and life as we know it?

Or will we have figured out
how to navigate

To a new universe before then?

I think we will only know
when we truly understand

Why the universe exists at all.

Perhaps then,

When we finally unravel
the whole cosmic puzzle,

We will become masters
not just of our universe,

But the universe next door.