All language subtitles for Wonders of the Solar System E01 Empire of the Sun 1080p AC3+DTS_Subtitles06.ENG

We live on a world of wonders.

A place of astonishing
beauty and complexity.

We have vast oceans

and incredible weather.

Giant mountains
and breathtaking landscapes.

If you think that
this is all there is,

that our planet exists
in magnificent isolation,

then you're wrong.

As a physicist, I'm fascinated
by how the laws of nature

that shaped all this also shaped
the worlds beyond our home planet.

I think we're living through
the greatest age of discovery

our civilisation has known.

We've voyaged to the farthest
reaches of the solar system.

We've photographed
strange new worlds,

stood in unfamiliar landscapes,
tasted alien air.

And at the heart of it all
is the powerhouse.

A vast wonder that
we greet each day.

A star that controls each
and every world in its thrall.

Look at that!

'The sun.'

And when it goes,
it really will be the end of us all.

This is Varanasi.

For Hindus, it's one of the
holiest sites in all of India.

Part of what makes it so special

is the orientation of its sacred
river as it flows past the city.

This is the one place on the Ganges
where you can bathe in the river

on this shore and you can see the
sunrise on the eastern shore.

It's the only place where the
Ganges turns around to the
north so you can do that.

When the sun rises tomorrow,

a truly extraordinary
phenomenon will take place:

a total eclipse of the sun.

It's an auspicious occasion

for a place that ancient Hindus
knew as the Solar City.

Science is different to all
the other systems of thought,

the belief systems that
have been practised

in this city for millennia,
because you don't need faith in it.

You can check that it works.

So, for example, I can tell you that
tomorrow morning at precisely 6:24am

the moon will cover
the face of the sun

and there will be
a total solar eclipse.

I can tell you that in 2904

there will be five solar eclipses
on the earth

and I can tell you that
on July 16th, 2186

there will be the longest solar
eclipse for 5,000 - seven minutes.

The sun reigns over a vast empire of
worlds, all moving like clockwork.

Everything within its realm obeys
the laws of celestial mechanics

defined by Sir Isaac Newton
in the 17th century.

These laws allow us to predict
exactly where each world will be

for centuries to come.

And wherever you happen to be,

if there's a moon between you and
the sun, there will be an eclipse.

Of course, Jupiter, plenty of moons,
and this is a rare picture

taken by the Hubble space telescope
in spring 2004

where you can see the shadows
of three moons on the surface,

three eclipses simultaneously.

Now, this kind of event only
happens once every few decades.

Saturn, plenty of moons.

I think these are my favourite
of all the pictures of eclipses

in the solar system

because these are pictures taken
from the surface of Mars

by the Opportunity rover
looking up at the sun.

And you can see Mars's moon,
Phobos,

as it makes its way
across the disk of the sun.

So this is a solar eclipse,
partial solar eclipse,

from the surface of another world.

The astronomers of the future will
discover that these partial eclipses

can never measure up
to the ones back home.

And that's because, here on Earth,

humans have the best seat
in the solar system

from which to enjoy the spectacle
of a total eclipse of the sun.

All thanks
to a wonderful quirk of fate.

The sun is 400 times the
diameter of the moon but,

by sheer coincidence, it's 400 times
further away from the earth.

So when our moon passes
in front of the sun,

then it can completely obscure it.

Now there's something
like between, what,

145 and 167 moons
in the solar system,

depending on how you count them,

but none of them produce
such perfect eclipses
as the earth's moon.

This accidental arrangement
of the solar system

means we're living
in exactly the right place

and, tomorrow morning,
exactly the right time

to enjoy the most precious
of astronomical events.

Our closest star is the strangest,

most alien world
in the solar system.

It's a place we can never hope to
visit but I want to show you that,

through space exploration
and a few chance discoveries,

our generation is getting to know
the sun in exquisite new detail.

For us, it's everything
and yet it's just one ordinary star

amongst 200 billion starry
wonders that make up our galaxy.

This is the remote frontier
of the solar system,

a dwarf planet known as Sedna.

Seen from out here, 13 billion
kilometres away from Earth,

the sun is just another star.

Uranus is 10 billion kilometres
closer in,

but even so,
sunrise is barely perceptible.

The sun hangs in the sky 300 times
smaller than it appears on Earth.

Further in, we come to Saturn.

Its spectacular rings reflect
the sun's light onto its dark side.

This planet is bathed, not just
in sunshine, but in ring-shine.

230 million kilometres out,

we arrive at the first world

with a more familiar
view of the sun.

This is sunset on Mars, as
seen by the robotic rover, Spirit.

Past Earth,
150 million kilometres out,

we continue to head to the heart
of the solar system.

Mercury is the closest planet,
just 46 million kilometres out.

It spins so slowly that sunrise to
sunrise lasts for 176 Earth days.

Beyond,
there is nothing but the naked sun,

a colossal fiery sphere
of tortured matter,

burning with a temperature
at its core

of over 15 million degrees Celsius.

Throughout human history,
this majestic wonder

has been a constant source
of comfort, awe and worship.

This is Death Valley in California,

regularly the hottest place
on the planet,

and today the car says it's
111 degrees Fahrenheit,

45 degrees Celsius.

For centuries, the finest minds in
science struggled to understand

the origin of the sun's seemingly
endless heat and energy.

What is it made of?

Where did it come from?

And what is the source
of its phenomenal power?

Then, in 1838, British physicist
John Herschel, took on the endeavour

in his experimental attempt
to catch a sunbeam.

So how much energy does fall on the
surface of the earth from the sun?

You can work it out with a
beautifully simple experiment

using only a thermometer,
a tin full of water and an umbrella.

Basically, you let the water heat
up in the tin to ambient temperature

which, here in Death Valley today,
is about 46 degrees Celsius.

And then you put the
thermometer in the water

and you take the shade away

and let the sun shine on the water.

In direct sunlight, the water
temperature begins to rise.

By timing how long it takes the sun

to raise the water temperature
by one degree Celsius,

you can figure out
exactly how much energy

the sun has delivered
into the can of water,

and from that, how much
energy is delivered

to a square metre of the surface.

It turns out that, on a clear day
when the sun is vertically overhead,

that number is about a kilowatt.

That's ten 100 watt bulbs can be
powered by the sun's energy

for every metre squared
of the earth's surface.

In an audacious leap of imagination,
Herschel used this figure

to calculate the entire energy
given off by the sun.

So imagine adding up those kilowatts
over this entire landscape.

And then imagine
following the sun's rays

as they cover the
entire surface of the earth.

But then, imagine this,

the earth is 150 million kilometres
away from the sun,

so actually, the sun is radiating
energy out across a giant sphere

with a radius of 150 million
kilometres surrounding our star.

How much energy does that make?

It's four x pi x the distance to
the sun squared, which is about...

It's 400 million million
million million watts.

That is a million times
the power consumption

of the United States every year,
radiated in one second.

And we worked that out
by using some water,

a thermometer,
a tin and an umbrella.

And that's why I love physics.

It's a wonder of our star
that it's managed to keep up

this phenomenal rate of
energy production for millennia.

Stars like the sun are
incredibly long-lived and stable.

Our best estimate for the age of
the universe is 13.73 billion years

and the sun has been around
for five billion years of that.

That's more than a third
the age of the universe itself.

So what possible power source
could allow the sun to shine

with such intensity day after
day for five billion years?

The best way to find the answer is
to go back to the very beginning.

And it all began from,
well, pretty much nothing.

There was a time when this corner
of the galaxy was without light.

The sun had yet to begin.

The story of how our star was
born can be read in the night sky.

If you take a picture
of the Milky Way,

then one of the first things you
notice are these dark lines,

these dark clouds running through
it, an absence of stars and,

in fact, those dark areas
are called molecular clouds.

They're clouds of
molecular hydrogen and dust

that are lying in between us and
the stars of the Milky Way galaxy.

These dark clouds contain the raw
material from which stars are made -

vast stellar nurseries

that are amongst the coldest and
most isolated places in the galaxy.

In the centre of some
of those clouds,

the temperature is as low as
ten degrees above absolute zero.

Now, that matters because
temperature is a measure

of how fast things are moving.

So, in these clouds, the
clumps of hydrogen and dust

are moving very slowly.

Only in this extreme cold

can gravity grab hold of the
clouds' constituent particles.

Over millennia,
they begin to condense.

That means that the weak force
of gravity can take over

and begin to clump
the hydrogen together.

Now, we have a name
for clumps of hydrogen

collapsing under their own gravity -
stars.

So, as those clouds of hydrogen
collapse further and further

under the force of gravity,

they begin to heat up and
eventually, in their cores,

they become hot enough
for the hydrogen

to begin to fuse together
into helium.

The stars ignite,
the clouds are no longer black

and the lifecycle
of a new star has begun.

This very story played out
five billion years ago

when a star was born that would
come to be known as the sun.

And its birth reveals
the secret of our star's

extraordinary resources of energy,

because the sun,
like every other star,

was set alight by the most powerful
known force in the universe.

The fusion of hydrogen
into helium

is the foundation
of all the sun's power.

Boundless energy that reaches out

and connects this wonder
to all of the worlds in its realm.

This is the Iguazu River
which flows into the Parana,

one of the great
rivers of the world,

and it's these river systems
that drain all the rainfall

from the southern Amazonian basin
eventually into the Atlantic.

Just look how much water there is.

Every molecule in this river,

every molecule in every
raindrop in every cloud,

has been transported from
the Pacific over the Andes

and into the
continental interior here.

Just imagine
how much energy that needs.

And all that energy
- every bit of it,

comes from the sun.

The sun is the power that lifts
all the water on the blue planet.

And in places, it comes down again

to create some of the most
breath-taking sights on Earth.

This is Iguazu Falls.

A quarter of a million
gallons of water

flow through here every second.

The spectacular energy of the falls

is a wonderful example of how
this planet is hard-wired

to the constant and unfailing power
of the sun.

The energy we see from the sun
may seem utterly constant,

but tiny fluctuations in
its brightness can be seen

with a digital camera
and the right know-how.

Now, it's not too difficult
to take a picture of the sun

even though it's 93
million miles away

because it's big.
Of course, you've got to be careful.

We've got a filter on here

that takes out
pretty much all of the light

because focusing the light
from a nuclear reactor

onto your camera or your retina

wouldn't be a great idea,
so you've got to be careful.

I'll take a picture.

Well, this is our picture of the
sun that we took on June 20th, 2009.

You can see it's a beautiful...

..orb,

with not a mark on the surface.

I suppose that's pretty much
what most people would expect.

It's certainly what Aristotle and
the ancient astronomers expected

because they thought the heavens
were perfect and unchanging.

But, look at this picture taken
on March 29th, 2001.

You see a completely
different story.

The surface of the sun is covered
in black spots - sun spots.

Some of these vast structures

are large enough to engulf
the entire Earth.

Space observation has allowed us
to track their numbers

as they ebb and flow
across the face of the sun.

The greater the number of sunspots,
the more powerful our star becomes,

threatening everything
from astronauts

to the electricity grids
back on Earth.

We've discovered
that the sun has seasons.

For decades, scientists
have sought to understand

how these subtle changes
in the sun's power

might be affecting the earth.

It's a puzzle that led one man
to look away from the sun

and focus instead on the rivers
around the Iguazu Falls.

Argentinean astrophysicist,
Pablo Mauas.

It's a very large river.

It's the fourth river in the world.

Unlike other larger rivers
than the Parana,

for example, the Amazon or Congo,

we have data of this river
for the whole 20th century.

So you can look back
to what, about 1900 or...?

Yes, from 1900, 1904.

And this is because this is a river

that can be navigated
by very large ships.

Pablo brought the statistical
tools of a physicist to bear

on 100 years worth of
precious river records.

What emerged was that the
river, too, had a rhythm.

We found that the stream flow
of the river goes up and down

and up again and down again
three times during the century.

And then we went further,
trying to understand why.

The amount of water
in the Parana River

seems to be following a pattern.

The question is,

what could be driving the change
in these vast river systems?

Pablo first looked to the 11-year
sunspot cycle, but found no fit.

So instead,
he turned to calculations

that described the sun's underlying
brightness during the last century.

He showed me what happened when
you superimpose this solar data

on the water levels in the river.

You see that when the sun goes up,
the river goes up.

So what this is saying is,
around 1925 or so,

there was more solar activity,

so the amount of, really, the solar
radiation falling on the earth.

Right, there was relatively more
activity, solar activity,

in these three periods
we can see here.

I mean, it's a beautiful correlation
between the water flow,

the flow in these rivers
and the solar output.

Yes, it is. We find it's a
very striking correlation.

Changes in the sun seem to move
weather systems elsewhere, too.

In India,
the monsoon appears to follow

a similar pattern
to the Parana river,

whereas in the Sahara,
the opposite seems to occur.

More solar activity, less rain.

The exact mechanisms by which our
star may affect Earth's weather

remain, for now, a mystery.

We know that the energy
production rate of the sun,

the power released in the
fusion reactions at the core,

is very constant indeed.

It doesn't change
as far as we can tell,

and so the changes that we see

must be to do with the way
the energy gets out of the sun.

And, whilst it's only at the
tenths of a percent level

in the amount of radiation that
falls onto the surface of the earth,

it really does reveal
the intimacy and delicacy

of the connection between
the sun and the earth.

And this connection is the secret
to another of the sun's wonders.

Of all the stars in the universe,

we know of only one where
a phenomenon has arisen

which feeds on starlight.

These leaves are wonderful machines,

nature's way of harnessing
the power of the sun.

But they're fussy eaters.

They've evolved to use just
a fraction of the sunlight

that makes its way
through Earth's atmosphere.

Here on the surface,
sunlight may appear white.

But when you pass it
through a prism,

you see it's made up of all
the colours of the rainbow.

The prism splits sunlight
into its component colours,

revealing the red,
green and blue photons.

And it's not just their
colour that distinguishes them.

The red photons don't carry much
energy, there are lots of them,

whereas the blue photons,
although there are fewer,

carry a lot of energy.

And plants use the red bit
of the spectrum,

and they use the blue bit
of the spectrum,

but they don't use
as much of the green.

That's reflected
and so that's why,

when you look around a forest
like this on a sunny day,

you just see a sea of green.

So the wonderful colour of
the forest is all down to how

plants have adapted to the
quality of our star's light.

And it's this ability
to harvest sunlight

which lies at the base
of the complex food chain

which nourishes, well,
pretty much all life on Earth.

Each and every one of us is
sustained by the sun's light,

an umbilical cord of sunshine

that stretches across 150
million kilometres of space.

But beyond the visible power of
the sun lies another realm.

These are the unseen forces

by which it maintains
influence over its domain.

And, very occasionally,
the solar system arranges itself

so that we can glimpse this
invisible kingdom with our own eyes.

It's 5.28,
so that's time of first contact

and you can't see the disc
of the sun at the moment,

it's obscured by low cloud.

The edge of the moon is,
at this point, just beginning
to touch the disc of the sun.

You can see the sun emerging
through the clouds, see the disc.

Oh, and you can see the moon.
Can you see the moon on the top?

Oh, yeah!

It just vanished.
Can you see the rim of the moon
there? Absolutely fantastic.

Yeah? See the sun?

CROWD CHATTERS

You can see the celestial mechanics,
the clockwork
of the solar system at work.

The alignment is absolutely perfect.

CHATTERING STOPS

Look at that!

If you EVER needed convincing
that we live in a solar system,

that we are on a ball of rock
orbiting around the sun with other
balls of rock, then look at that.

That's the solar system coming down
and grabbing you by the throat.

'The sun's face is now
completely shrouded by the moon.

'Only now, during totality, is the
hidden wonder of the sun revealed.'

Look, I mean, that's the sun's
atmosphere, that's not clouds.

There are no clouds there now.

That's the solar corona. That's the
atmosphere of our star shining out.

The sun's atmosphere is strange.

It's made up of a thin collection
of charged particles,
protons and electrons.

Through mechanisms that we don't yet
fully understand, the corona is
much hotter than the surface.

Here, temperatures soar to
over a million degrees Celsius,

some 200 times hotter
than the visible surface.

Each and every day, right at
the very top of the atmosphere,

some of the most energetic
coronal particles are escaping.

The sun leaks nearly seven
billion tons of corona every hour
into space, a vast,

superheated, supersonic
collection of smashed atoms

that en masse are known
as the solar wind.

This is the beginning
of an epic journey that will see

the sun's breath reach out to the
furthest parts of the solar system.

Look at that!

CHEERING AND APPLAUSE

'All too soon, this brief glimpse
of the solar wind's origin is gone.'

It's the most incredible thing
I've ever seen, actually.

Amazing when, when the sun
re-emerged from behind the moon.

Everybody just...like that...

Goes... Wow!

The solar wind
may be invisible to us,

but each day, tiny pieces of our
star are constantly blowing our way.

Now, by the time the solar
wind reaches the Earth,
it's pretty dilute.

You know if you were to go out
into space close to the Earth

and hold your hand up there,
you wouldn't feel anything.

In fact there are about five protons
and five electrons for every sugar
cube's worth bit of space,

but still they're travelling
very fast and
they carry a lot of energy,

enough energy in fact
over time to blow the
earth's atmosphere off into space.

So how does life on our
planet survive this lethal gale?

'To find the answer,
I need to head north.

'On a beautiful sunny winter's day
in the Arctic, it's hard to imagine
that our star could be a threat.

'But high above us,
deadly solar particles are streaming

'our way at speeds topping a
million kilometres an hour.'

Down here on the Earth's surface,
we're protected from that intense
solar wind that's battering

our planet because the Earth
has a natural shield that deflects
most of the solar wind around it.

And to see that shield,
you just need a simple
shield detector which is a compass.

And that's because the
earth's force field is magnetic,

an invisible shell that surrounds
the planet in a protective cocoon.

It's very similar to the shape
of the field around the bar magnets

and you can see that shape
by moving a compass around it.

The compass needle follows
the magnetic field lines,

and the Earth field is actually
very similar in shape to this one.

The magnetic field emanates from
deep within our planet's spinning
iron-rich core.

And it's this gigantic force field,
known as the magnetosphere,

that deflects most
of the lethal solar wind
harmlessly away into space.

But the planet doesn't
escape completely.

When the solar wind hits the Earth's
magnetic field, it distorts it.

It stretches the field out
on the night side of the planet

and in some ways it's like
stretching a piece of elastic.

More and more energy
goes into the field.

Over time, this energy builds up
stretching the tail,

until it can no longer
hold onto it all.

Eventually, the energy is released,
accelerating a stream

of electrically charged particles
down the field lines
towards the poles.

And when these particles that have
been energised by the solar wind

hit the Earth's atmosphere,
they create one of the most
beautiful sights in nature -

the aurora borealis,
or Northern Lights.

'I've come
to the far north of Norway

'in hope of seeing the solar wind's
influence on our planet for myself,

'to see the mystical aurora
for the first time.'

Seeing the aurora on any
given night is far from certain.

'So to shorten the odds,
I've recruited the help
of an astrophysicist,

'Professor Mike Lockwood.'

So Mike, not that I'm complaining,
but other than for reasons
of pure enjoyment,

why did we have to come
to the Arctic Circle on snowmobiles?

The city street lights produce
a light pollution

that actually make it
hard to see the aurora

and it's good we've come
at the end of winter

because the energy we take out
the solar wind is stronger.

Yes, so this is, I suppose then,
the perfect day because we're in
late March, completely blue sky.

Fabulous. If this stays,
we've got 80% chance tonight.

Soon after dusk, and despite
clear skies, there's no early
performance from the aurora.

So while we wait, Mike runs
a film loop of the Northern Lights

as seen from
an extraterrestrial perspective.

So that's a beautiful image.

I haven't seen an
image like that before.

It was taken from above the pole?

Yeah, that's a spacecraft
in orbit around the planet,
yes, going from pole to pole.

'From space, you can really see
the impact of the solar wind.

'Its energy feeds
an unbroken circuit
of aurora that surrounds the pole.'

And we will feel that it's a
display put on just for us here.

When you see the pictures from space,
you realise everybody on that oval
is getting the display.

Well, my hope is that we'll be
directly underneath that tiny
thin band tonight here in Tromso.

Thankfully, our luck holds
and the skies remain crystal clear,

until at last,
energy brought by the solar wind
sets the upper atmosphere alight.

Absolutely amazing sight.

Arcs, but more like
curtains of green.

It doesn't look to me
like it's cascading down.

It looks like it's rising up
from the ground.

It is quite incredibly beautiful,

and I thought
before I'd seen it that I would

think it was all the more wonderful
because I knew that I was seeing

a visual manifestation of the
earth's magnetic field protecting us
from the solar wind,

but I don't think that.

Actually over there,
there's a green shaft of light
that looks like it's rising up

out of the mountain in the distance
and it looks like spirits drifting
up from the mountain into heaven.

Absolutely magnificent.

Our environment doesn't stop
at the edge of our atmosphere.

In fact our environment stretches
at least as far as the sun

which is an obvious statement
to make in the daytime

because you can feel the heat
of the sun, but in the night time,
you see this other side.

You see this unseen
and constant solar wind.

Beyond earth, the solar
wind continues to race
out into the solar system

and wherever it encounters
a planet with a magnetosphere,
aurora spring up.

Jupiter's magnetic field
is the largest and most
powerful in the solar system.

Seen from the Hubble space
telescope, the aurora here

are a permanent fixture
over the Jovian poles.

Saturn, too, puts on
an impressive display
as seen in this remarkable footage.

Eventually, though,
way beyond the planets, the solar
wind begins to run out of steam.

It's travelled
non-stop for 16 billion kilometres,

over 100 times the
distance of the Earth from the sun.

And incredibly,
we have a probe out there

which is about to discover exactly
where the wind from the sun ends.

When I was about five, I collected
these cards, the Race Into Space.

It starts with Sputnik and it's a
history of space, and right at the
end there's the speculative stuff

about moon base and then a manned
mission to Mars, on November 12th
1981, it was going to leave.

In there is the Grand Tour
proposal by NASA to go

to Jupiter, Saturn, Uranus, Neptune
and it actually went.

I remember in '77 being excited
and watching the launch

and thinking this is, my card
has come to pass, it's come to be.

And astonishingly, I
think, we're still in
contact with this thing now.

A pair of spacecraft
were sent out on the Grand Tour,
Voyagers one and two.

Both are alive and well, and Voyager
one reports back to earth here.

Now, also in my book was this
picture, the Goldstone Mars
station in the Mojave desert.

And there it is, 210 feet or it was
at the time this book was written.

It's been expanded since
and it's one of the few telescopes
in the world that's capable

of communicating with Voyager which
is ten billion miles from the Earth.

Today, the Goldstone station
is listening out for the faintest
whisper from Voyager one.

Call 233, oh, it's almost there now,
so we should be seeing it coming in.

'Voyager is so far away
that it takes the signal

'around 15 hours to arrive,
travelling at the speed of light.'

Oh, that triangle?

Yeah, that's it, right there.

There.

'It may appear as little
more than a blip on a screen
but for me, it's beautiful.'

I mean, you just have to think about
it, this little thing,

it's no bigger
than a double-decker bus,

designed in the late '60s,
launched in the mid-'70s

and still functioning
32 years later,

and good science data
is still coming out
of that little space craft.

I think it's absolutely wonderful.

Both Voyager spacecraft are
constantly measuring the solar wind
as it fades away.

One day soon, they will
find the place where the sun's last
physical trace finally runs out.

They'll leave the star that
raised them behind and head off
into interstellar space.

But even at that place, ten billion
miles away where the solar wind
meets the interstellar wind,

that isn't the end of the story.

That isn't the edge
of the sun's influence.

'The sun has a final invisible
force that reaches out much further.

'Our star is, by far, the largest
wonder in the solar system.

'In fact, it alone
is 99% of the solar system's mass.

'It's this immensity
that gives the sun its furthest
reaching influence...

..gravity.

So its gravitational field
dominates and all the planets
are bound gravitationally to it.

The Earth for example,
93 million miles away,

also known as one astronomical unit

so let's represent that
by one centimetre...

And the most distant planet,
Neptune, 30 astronomical units
so 30 centimetres.

We then meet the Kuiper belt objects
of which Pluto, the ex-planet,
is a member.

They inhabit a region around
50 astronomical units

so that is the size
of the solar system in terms of...

well, all the planets and all
the Kuiper belt objects out to
Pluto, but it doesn't stop there.

'Beyond Pluto, space is a cocktail
of extremely dilute gas and dust,'

mostly just hydrogen and helium
left over from the universe's
beginning at the Big Bang.

But every now and then,
you encounter lumps of ice
in vast orbits

that take millennia
to loop around the sun.

And that cloud of snowballs
is called the Oort cloud.

'And astonishingly,
the sun's grip is so strong

'that objects in the Oort cloud keep
popping up all the way to out here.'

Now, that cloud of dirty snowballs,
still gravitationally bound

to the sun, extends out
50,000 astronomical units.

On our scale,

that's half a kilometre
from the sun and remember,

the Earth was one centimetre away.

This, then, is the full extent
of the sun's empire,

the lightest gravitational touch
which retains a cloud of ice,

enclosing the sun
in a colossal sphere.

Beyond the Oort cloud,
there is nothing.

Only sunlight escapes,
light that will take four years

before it reaches even the sun's
closest neighbour, Proxima Centauri,

a red dwarf star
among the 200 billion others
that make up the Milky Way.

And it's by looking here,
deep into our local
galactic neighbourhood,

that we're learning to read
the story of our own star's
ultimate fate.

The sun's empire is so vast and so
ancient and its power so immense,
it seems like

an audacious thought to think that
we could even begin to comprehend
its end - the death of our sun.

But that's what
astronomers are trying to do

and many of them come here
to the most arid and barren desert
on earth, the Atacama in Chile,

and that's because the skies here
are some of the clearest on earth.

'It's the end of my journey
through the empire of the sun.'

I've come to Paranal,
high up on an extinct volcano.

It's home to the world's most
powerful array of telescopes.

I've got to tell you this.
This is great.

You get important information you
should know for a safe stay
on Paranal

because it's about 2,500 metres,
two and a half kilometres
in the air, and it says here

that if during your stay you
experience any of the following,
consult a paramedic immediately...

So there's headache and dizziness,
breathing problems, ringing or
blocking of the ears...SEEING STARS.

It honestly says 'If you see stars
at the Paranal Observatory,
consult a paramedic immediately!'

'Perched high above the clouds,
four colossal instruments

'make up the European Southern
Observatory's Very Large Telescope,
or VLT.'

Even with the naked eye,
the seeing here is spectacular.

The first thing you notice streaking
across the sky is the Milky Way.

You can have no doubt when you look
at that that we live in a galaxy
of billions of stars.

The next thing you notice, if you
look a little bit more carefully,

is the stars are not just
white points of light
against the blackness of the sky.

They're actually coloured.

You see orangey-red stars,
yellow stars and bluey-white stars.

Absolutely beautiful.

Astronomers have
gazed upon the galaxy full of stars
at all stages of their lives,

from youthful, bright stars
to middle-aged yellow stars
very similar to the sun.

They've meticulously charted
the nearest 10,000 of them,

and then arranged each according
to its colour and brightness.

What emerges is one of the
most powerful and elegant

tools in the whole of astronomy,
the Hertzsprung-Russell diagram.

And so this diagram allows
astronomers to predict
the history and evolution of stars,

and in particular,
the future life of our sun.

There's real structure here.

There's this line that goes up
from red stars through yellow stars

to white stars, and this is
called the main sequence.

The sun will spend most of its life
in the main sequence,
steadily burning

its vast reserves of hydrogen fuel
which will last for at
least another five billion years.

But eventually the fuel will run out
and its core will collapse.

'Then something
remarkable will happen.'

The sun's outer layers will
expand and its colour will shift.

Mercury will be little more
than a memory as it's engulfed
by the expanding red sun.

It will grow to 200 times
its size today,

stretching all the way out
to the Earth's orbit where
our own planet's prospects are dim.

The wonder that has remained
so constant throughout all

of its ten billion years
of life will end its days
as a red giant star.

For a few brief instants, it will be
2,000 times as bright as it
is now but that won't last for long.

Eventually it'll shed its outer
layers and all that will be left
will be its cooling core,

a faint cinder that will glow,

well, pretty much
to the end of time.

And all its wonders, the aurora
that danced through the atmospheres
of planets of the solar system,

and its light that sustains all the
life here on earth, will be gone.

'But the gas and dust of the dying
sun will drift off into space,

'in time to form a vast dark cloud
primed and full of possibilities.

Until one day,
another star will be born,

perhaps,
with a similar story to tell,

the greatest story of the cosmos.

Subtitles by Red Bee Media Ltd

E-mail subtitling@bbc.co.uk