Horizon (1964–…): Season 44, Episode 9 - Are We Alone in the Universe? - full transcript

Why do we humans have such a
connection to the night sky?

The twinkling lights that seem like
oases out there and yet we're not
sure. Are there habitable worlds?

Around the world there are a
group of highly intelligent,

highly trained scientists
that share a surprising belief.

There are a couple of hundred
billion stars just in our galaxy and

at least half of them probably have
planets. That's 100 billion
planetary systems.

How many planets in each system?
let's say five.

That's a half trillion,
500 billion planets out there.

Keep in mind, there are 100 billion
other galaxies!

For these scientists the
vastness of our universe
can mean just one thing -

the existence of life.



So to think, "Look, man.
This is the only place where
anything interesting's happening",

you've gotta be really audacious
to take that point of view.

But proving it has not
been quite so simple.

I have conducted many, many
searches, none of which
have produced a discovery.

Until now.

In our local neighbourhood, just
200 trillion kilometres from Earth,

is a planet that we
might find rather familiar.

The discovery of Gliese 581c
is a marvellous discovery.

It shows how close we're getting to
planets that remind us of the Earth.

Occasionally you're sitting on a
plane and they guy next to you says,
"What do you do for a living?".

"I look for aliens".
I explain a little bit, and almost
every one everyone is interested.

Nobody says, "That's nice.
I'll go back to my magazine now".

In the desert, 300 miles north of
San Francisco, Dr Seth Shostak is
waiting for a message from an alien.

This is SETI,
the front-line in the search for
extra-terrestrial intelligence.



If a message ever comes our way,
this is where it will be received.

Anybody who can build a transmitter
can send messages between the stars.

If we can do that,
maybe they can do it.

Here we are, the Allen Telescope
Array, - designed to do one thing -

eavesdrop on any signals that
might be being broadcast our way by
some alien civilisation.

This vast array of telescopes
is the latest in a long line

of experiments designed to
eavesdrop on our nearest neighbours.

As chief astronomer of the project,
Shostak is more confident than most

that he'll be on the receiving
end of a close encounter.

There are 42 antennae here now,
you can count them up.

But eventually the idea is to have
350 and then this thing

will be able to scan
big chunks of the sky,

simultaneously observing five, six,
maybe more stars at a time, looking

for the signal that somebody's out
there, trying to get our attention.

It's the most powerful experiment
humans have ever attempted -

to discover if intelligent life
is the exception or the rule
in the cosmos.

But although it's early days
for Shostak and his team,
the omens are not good.

The SETI project has been
casting its ear out to the
universe for over 50 years.

For the founding father of
the search, Dr Frank Drake,
the dream has never changed.

Back in the 1950s, there were many
scientists interested in ET life,

but we were well aware that
there were no means even to detect

planets, let alone microbes,

or any sign
of non-intelligent life.

In fact, the only thing open
to us was radio transmissions
from intelligent civilisations.

Drake was the first scientist to
believe that technology could
answer the biggest question of all.

Despite widespread scepticism,

he believed that if there were
intelligent life forms out there

then the least we could do
is to try and listen to any radio
signals they may be sending out.

In 1960, we conducted a search for
radio signals from the two nearest

stars to the Earth that are like
the Sun - Tau Ceti
and Epsilon Eridani.

But to no-one's surprise,
the search failed.

We searched for two months.
We didn't find anything.

And that's actually an important
result, because it showed not every
star in the sky was radiating.

It also demonstrated that a search
was likely to be a very long
and difficult one.

Despite putting on a brave face,
Drake and his ideas remained on
the very fringes of astronomy.

Listening for aliens
just wasn't science.

Congress people would see that
they could get publicity by

attacking this project as a
waste of tax-payers' money.

Using tax-payers' money to search
for little green men was a
common theme.

So Drake would have to wait for
another generation of scientists

to bring alien-hunting
in from the cold.

Being an astronomer is a
bit sacrificial.

My wife is at home and she misses me.

I call her up and she says,
"When are you coming home?"

It's another four, five
nights, I have to tell her.

Professor Geoff Marcy is a planet
hunter, an explorer of alien worlds.

Staying up all night means
you don't get much sleep.

So it's a bit of a sacrifice, but
I wouldn't give it up for anything.
It's such a treasure.

For the last ten years,
Marcy has come here to

use the planet's largest telescope
in the hope of finding other worlds.

The Keck Telescope high up on
Mauna Kea, Hawaii is about as close
as you can get to the stars.

It's the world's largest, because the
collecting area of the mirror
is the largest in the world.

The mirror is ten metres across,

1/10 the length of a football field,
all to collect the starlight

coming from hundreds or
thousands of light years away.

But even using the
mighty Keck telescope,

Pluto, at the edge
of our solar system, is a colossal
4? billion kilometres away.

And this is the best image
astronomers have achieved.

And yet Marcy wanted to look
beyond our solar system,

to find the hypothetical worlds
that astronomers call exoplanets,
which lie around other stars.

Like our nearest star,
Proxima Centauri,

a staggering 40 trillion kilometres
away, or four light years.

Beyond lies the rest of our
galaxy - an unimaginable
100,000 light years across.

It's our local neighbourhood
of 200 billion stars.

Astronomers knew there had
to be planets out there.

We saw young stars with
proto-planetary disks of gas and dust

around them, surely making planets.

But we couldn't detect the planets.

And the reason is that even with the
largest telescope, like this one,

the mighty Keck, the planets were
lost in the glare of the host stars.

The problem is that compared
to the light of a star,

the reflected light from an
exoplanet is all but invisible.

The star burns a billion
times more brightly.

Indeed, even with the Hubble
space telescope, we can't detect
planets directly around nearby stars.

Using direct observational methods,
astronomers were confined within our
own solar system,

unable to prove even the existence
of exoplanets, let alone life.

So how do you look for
something you can't see?

The answer was first proposed in
an obscure paper published in 1952,

by a Russia astronomer called
Otto Struve.

Struve theorised that even
though the planets themselves

were invisible, there was still
a way of unlocking their secrets.

He knew that each planet was
held in orbit around its star
by an immense gravitational force.

This force works in two directions.

The star pulls on the planet but the
planet also pulls back on the star,

making the star move
with the minutest wobble.

It's not much, but this wobble is
just big enough

to make it theoretically detectable
back here on Earth.

If you have the right technology.

The real tipping point was not in the
telescopes, we've had big telescopes
for several decades.

The tipping point was having digital
detectors, like the digital cameras

that most of us enjoy, with the CCD
light detectors at their backs -
and computers.

Let's see what kind of a
night we're gonna have here.

Marcy script underscore
ETA underscore Earth.

Great. First object on the list...

Why don't you go ahead
and open the dome slit?

We're observing 80 stars, night
after night, with one key goal, and
that's to detect Earth-like planets.

Since the early 1990s, planet
hunters like Marcy have been gazing
to the stars for the tiniest wobble

that could signal the

The theory seemed correct.

They had the right technology,
and yet after years of searching,
the exoplanets were still missing.

We were confronted
with a contradiction.

On the one hand, it appeared
that young stars had the right
kind of planet building material,

but on the other hand,
humanity had failed to find any.

All the planet hunters had to
keep them going was their faith.

And the belief of the one man
who has never given up hope.

It occurred to me, we need to
know how often does life arise,
how often does intelligence arise.

I recognised that all you had to do
was multiply these factors together

and you have a very prime important
equation, of basic interest,

because it tells us how many
civilisations there are out there.

Without any hard evidence,
back in 1960, Frank Drake went

about creating an equation
that would answer the big question
once and for all.

We have an equation which gives
us N, the number of detectable
civilisations in our galaxy.

It's based on what we know of
the history of our galaxy

and particularly the history of our
solar system and of life on Earth.

The equation defines
all the necessary ingredients for
intelligent life to arise.

There are seven
factors in the equation.

Since life needs a home,
it begins with a known observation.

For the rate of star
formation, we know that very well.

It's about 20 stars per year.

For the fraction of planets, we
didn't used to know that at all.

Everything else in the equation,
from the number of stars
with planets

to the number of planets
per star capable of supporting life,
was a total mystery.

But over the years, it hasn't
stopped people from guessing.

This is our number N.

The number of technical
civilisations in the galaxy.

Into the now famous, or infamous,
Drake equation goes everything,
from astrophysics, through

evolutionary biology to whatever
it is that governs the lifetime
of a detectable civilisation.

Not surprisingly, no-one's solved
it yet, but anyone can have a go.

It's almost a game the
whole family can play.

If you sort of take
the average of people's guesses,

it gives you a total number
of detectable civilisations,

which is about 10,000.

A big number.

And yet with no call from ET, and
no sign of another Earth, Drake's
guess seemed wildly optimistic.

When I was a child, I was living in

We spent evenings
with my sister laying down on the
grass and looking at the sky.

And that's really good
for the imagination.

I'm sure there are other
Earths similar to our own Earth.

And on some of them, you
even may have life developing.

Professor Stephane Udry is part of
a Swiss team of planet hunters

who began searching for life-bearing
planets in the mid-'90s.

They had developed a new planet
detector,

which had just been installed at
their observatory in central France.

When you have a new instrument,

you want to check the short-term
precision of the instrument.

Tests of their new detector where
scheduled to last a few weeks.

Among their target stars was
one similar to our own sun,
called Pegasi 51.

The light from Peg 51
should remain constant,
but there seemed to be a problem.

The star...

appeared to be wobbling.

The thinking was, "Oh, that should
be some crazy effect of the star
that could explain the observations".

They tried to reject, one after the
other, all the possible explanations.

And at the end, the best explanation
was the presence of a planet.

With ingenuity and
a little bit of luck,

the Swiss had discovered the first
planet outside our solar system.

It was massive,
half the mass of Jupiter, but in a
rapid orbit lasting only four days.

The planet was so close to its star,
that surface temperatures
exceed 1,000 degrees Centigrade.

Being part of these teams
finding planets around other stars

is very exciting in that sense.

That's really a new
domain that is opening in science.

The discovery of this planet
opened the flood gates.

Hundreds of exoplanets
have since been discovered,

but none of them have
proved suitable for life.

My favourite planet
is a little planet that orbits
the star Gliese 756.

My favourite
planetary system is called 55 Cancri.

My favourite
planetary system is called 55 Cancri.

There are two planets which I have
an emotional attachment to.

It has an orbit of two days.

The planets of the star Tau Ceti.

That means
its seasons occur in two days.

And the star Epsilon Eridani.

So summer-winter would alternate
in two days.

It's like the solar system because
it's a planet like Jupiter
on a Jupiter-like orbit.

Those stars were my targets

when I first searched for the first
evidence of extra terrestrial life
in 1960.

It's unlike the solar system because
it has three other planets that are

very close into the star,
hot Jupiter-type planets.

In the last decade, astronomers
have found over 260 exoplanets,

most of them searingly hot
gas-giants.

As a biologist, I don't really have
a favourite exoplanet at the moment,

because the astronomers keep
finding me hot Jupiters and they
don't do much good for biology.

What I'm looking for is
something really Earth-like.

Something that's got a
good chance of liquid water.

And then I'll have a favourite.

So just how rare is our blue planet?

Dr Lynn Rothschild is an
astrobiologist who has studied our
own solar system

in an effort to understand
what makes Earth so special.

Let's pretend that this fire here is
our sun and that this rock is Venus.

It's about as close to the sun you
can get and still have liquid water.

So the orbit of Venus
would be, say, like this.

This is getting pretty hot, cos
I'm awfully close to the sun here.

Now on the other extreme, this is
Mars, which is the farthest planet

from the sun that has any chance
of liquid water.

There's no liquid surface
water today, but we know

that there used to be in the past.
So let's trace the orbit of Mars.

Now right between these two circles,
where the orbit of Mars would be

and the orbit of Venus,
this is where liquid water is stable.

And right in this habitable zone
in our solar system is planet Earth.

Our beautiful watery world
that's just covered with life.

Just 10% closer in,

and Earth would no longer be capable

of supporting liquid water.

Almost miraculously,
Earth slots right into the
heart of the habitable zone.

Giving this once lifeless rock
just the right elements for
life to take hold and flourish.

Over billions of years,
microbes, plants and animals

have transformed Earth into
a living, breathing world.

A world where one evolutionary line

has led to modern humankind
and civilisation.

But even with our civilisation's
most advanced technology,

finding other planets like Earth
has proved impossible.

Rotator is vertical, angle mode zero.

The very factors that enable life, a
small planet at a safe distance from

the sun, means the telltale wobbles
that these planets produce are tiny.

Our Earth, when it orbits the sun,
causes our sun to wobble with a speed

of 1/10th of one metre per second,
a smaller motion than we can detect.

Or there could be another, more
profound explanation for the
missing Earth-like planets.

It's possible that other stars
didn't have planets around them.

That we're just one of the
freaks of nature that grew
up on a rocky planet.

Either way, despite
decades of searching, until 2007,

Earth remained entirely alone.

Between the Andes mountains and
the Pacific Ocean, on the remote
southern edge of the Atacama desert

lies one of the most extraordinary
observatories on Earth.

The high elevation
and the low rainfall,

just one millimetre a year, makes it
the perfect place for uninterrupted
views of the southern night sky.

Please come in, I have
something to show you in here.

Professor Stephane Udry is the proud
owner of a machine which could
change the course of human history.

Inside this big box is an enclosure
and inside there is a vacuum tank

with the instrument,
that is the most sensitive in the
world now for planet detection.

With this instrument we can detect
low mass planet five, ten times
the mass of the Earth. Can we go in?

No. Of course not, because just
opening the door will destroy
the measurement for a few days.

Because we need to have a very stable
instrument to be able to repeat the
measurement with the same precision,

day after day,
month after month, years after years.

And that's exactly
what they've been doing.

They drew up a list of a thousand
targets taken from the Gliese
Catalogue of Nearby Stars

and began measuring and
re-measuring each candidate,

hunting for wobbles that had
previously been too small to detect.

But one star
caught Stephane's attention.

Gliese 581 was in our
target list since the beginning.

Categorised as Gliese 581a,
it's a red dwarf star,
a third of the mass of our own sun.

When the wobble was plotted
it revealed 581b, a massive
planet the size of Neptune,

close into the star

and orbiting once every 5? days.

It was no Earth,

but the star's wobble held some fine
detail that intrigued Stephane.

We noticed that there was
something else in the system.

There seemed to another, smaller
planet lurking in the detail.

That something else
could be a five Earth
mass planet very close to the star.

If Stephan's hunch was right,
it would be the smallest planet
ever detected around a distant sun.

And this planet
seemed to be habitable.

We got excited because the distance
was just right for the planet to
possibly be in the habitable zone.

After years of hunting, the search

for the first "Second Earth"
was over.

European astronomers have spotted
a new planet outside our solar system

which closely resembles
the planet Earth.

The probability that there
is life somewhere else in
the Universe goes up a bit.

This latest find has
set the world of astronomy alight.

For the Swiss team,
the breakthrough was a triumph.

It is always very exciting
to be the first one to know.

The discovery of Gliese 581c
is a marvellous discovery.

It shows how
close we are were getting to
planets that remind us of the Earth.

It shows that potential
life-bearing planets exist.

When you know, when you realise it,
and you are the only one,
it's like being in the spaceship

coming to a planet and being the
first one to see the landscape.

For those tempted to make
the journey, pick a clear night

and look for the constellation
Libra.

Invisible to the naked eye,

Gliese 581 lies just north of the
brightest star in the constellation.

Remarkably, it's one of our
closest neighbours,
a shade over 20 light years distant.

At the heart of the
system is the parent star.

Close by is 581b,
16 times more massive than Earth and
too hot for life to survive.

Beyond, just on the inner warm
edge of the habitable zone,

lies Gliese 581c -

the smallest and most
Earth-like exoplanet yet detected.

At last, scientists have
found another planet that may
just be capable of supporting life.

Not much out here.

See if there's any under the rock.

Nope. A lot of UV radiation.

Nothing green, nothing
coloured I can see. Very dry.

For astrobiologists
like Dr Lynn Rothschild,

its discovery means they can begin
to imagine what it would be like
to spend a day on a Super-Earth.

We're up here on the edge of
the Atacama desert in Chile
right near the Bolivian border.

You can see it's very dry, in fact,
one of the driest places on Earth.

This is a great place to get an
idea of what an extra-solar planet,

for example Gliese 581c,
might be like.

Let's imagine that
we're on Gliese 581c.

There's an awful lot of rocks around.
It's dry.

The planet's mass is
five times that of Earth.

This means that gravity
will pull twice as hard.

Whereas on the moon, the
astronauts could jump with no effort,

on this planet you would
be suffering from extra gravity.

If you took a rock and you threw
it, it would come crashing down,

much faster than that of the Earth.

High gravity will affect the
look of the planet. No mountains.

Just low hills and vast plains.

And the last thing is it's
close to the parent star,

and so the radiation from the sun
would be much stronger on Earth.

Here we're getting burned,
there we would probably be fried.

The planet's red dwarf star
will dominate the sky -

a fiery ball five times larger
than our own sun back home.

And a few hours into their trip,

interstellar visitors will discover
that this sun never moves.

The planet is so close to its star

that immense gravitational forces
have united the two.

They're tidally locked,
with the planet presenting
just one face to the light.

On the Earth, we're used to getting
up in the morning, the sun rises.

We have our midday meal,
in the evening we have dinner,
if we're lucky, we get a nice sunset.

But on something like Gliese 581c
it would be totally different.

If I wanted to see the equivalent
of a sunset, I'd be the one who'd
have to get into the car and move.

Beyond this point is the dark side

of the planet, perpetually turned
outwards to the cold of space.

I wouldn't want to live here,
I wouldn't want to be a colonist

on another world that
was barren like this.

I'd take even a year-long field trip,
but I wouldn't sign up for
the rest of my life.

Comfortable as Gliese 581c
may be for a day trip,

for life to exist there, for it
truly to be second Earth, it must
have one other vital ingredient.

Water is the one thing life on
Earth has in common, so we think

looking for water on other planets

is a way to look for
life on those planets.

For astrophysicists like
Sean Raymond, finding water

on other worlds is the key
to finding life.

Every day in his laboratory,
he makes new solar systems
from scratch.

So the way we do this
is computer simulations
of a disc of rocks orbiting

a star, and we let them collide and
let their orbits evolve, and such.

And it turns out these take
quite a long time to do.

Over the months,
Sean's computer calculates

how alien planetary systems
evolve over millions of years.

Here's a movie of one of these
simulations. You can see everything

on the inner disc
starts off red meaning, quite dry.

All these guys start off
being the size of the moon,
or actually a little smaller.

And then the number of bodies
is going down as they collide
and grow into larger things.

And by about 10 million years or so,
a planet almost the size of the
Earth is formed right there.

And you can see it's still red.

These new planets are all dry.
Only far out from the star

are temperatures low enough
for water to collect.

It's not until a little later...
you'll see in a second, it
gets collided by something that's

blue and turns - right there,
it went from being completely dry to
having some water.

And that process of water
delivery continues over the next
100 million years or so.

Over this time,
icy comets and asteroids from

the outer solar system are drawn
inwards towards the young planets.

Shaun's theory is they bring
with them vast amounts of water,

transforming dead worlds
into blue planets.

That's a pretty good Earth analogue.

And we think this is how the solar
system terrestrial planets formed.

Sean has run
hundreds of simulations.

And each time, some something
happens to the planets
in the habitable zone -

they nearly all have water.
Water is very abundant.

In the solar system,
water is two to four times more
abundant than rock and iron.

It looks like Earth might, on
average, be a little bit water-poor.

And many planets may end up
with a lot more water than the Earth.

Including the newly discovered 581c.

Gliese 581c especially, is very
exciting, a very big discovery.

These planets would have acquired
some water-rich material, so they

probably have some water contents
comparable to Earth at least.

Far from being a barren rock,

this new planet may be
awash with liquid water.

But in their rush to tell
the world of another world,

the Swiss had overlooked one
thing - the planet's atmosphere.

We got very excited about Gliese 581c

when we realised that it was just at
the right distance from the star.

But then, talking with specialists
of the evolution of atmospheres

on the planet, they told us
that maybe the greenhouse effect
could be big.

And so the temperature could be too
high for the development of life.

If the planet's atmosphere
contains too much water
vapour or carbon dioxide...

a runaway greenhouse
effect could take hold.

Rather than resembling Earth,
581c could be a super-Venus.

Instead of liquid water,

steam would shroud a searingly hot
world, incapable of supporting life.

It's probably too hot
to be habitable.

If it has water at all,
which is doubtful, that water would
be boiled off, evaporated and gone.

581c may, after all, lie on the
hot side of the habitable zone,

but the light the Swiss team were
collecting from the planet's star
held another surprise.

After decades of fruitless
searching for habitable worlds,
out popped another one.

We had to wait for one more year

before being able to actually find
another planet a bit further out.

There is a third
planet in the system.

They'd discovered a second
super-Earth in the same system -

Gliese 581d.

This world lies on the far,
cold edge of the habitable zone.

On first calculations, this
would make it a giant frozen world.

But if it too enjoys a greenhouse
effect, then it could be just
warm enough for liquid water.

If there is some atmosphere,
and a greenhouse effect,
then the temperature could

be even better on that planet
for the development of life.

Perched on opposite edges
of the habitable zone,

the conditions on the planets
in this system will be harsh.

Perhaps too harsh
for life to survive.

Here on Earth, Dr Lynn Rothschild
is investigating places where
conditions mirror the extreme

environments found on
both the G581 planets.

We're up here in the altiplano
in Bolivia. Up at about...

well over 4,000m, or 15,000ft.

In the winter it's frozen - it's not
a whole lot warmer in the summer,

and yet life lives up here.

Every place we've gone that's
cold - the Antarctic,
the ice caps, we've found life.

And even under here, there's plenty
that's growing. It's just amazing.

So life in the freezing
conditions of the outer
planet is a possibility.

And even the on the inner hotter
world, where temperatures could
exceed the boiling point of water,

scientists are beginning to
understand how life could survive.

We don't actually know how life
actually got started on Earth.

But we do know that when we look
at modern organisms,

and at their evolution,
the most ancient ones

seem to be the ones that
live at extremely high temperatures,

just like these areas around here.

Indeed, the more scientists look,

the wider the range of habitats
they find in which living
organisms can thrive.

So this gives us hope, this gives
us optimism that when we go elsewhere

to other worlds,
that there might be life.

For now, no-one knows for sure if
life could survive in the massive,

strange worlds of the G581 system.

And Earth-bound planet hunting may
have reached the end of the line.

Because to find true
Earth-sized planets,

the hunt is moving into space.

This is a spaceship factory.

In these category A clean rooms,
machines are built

that their designers hope will
unlock the secrets of the universe.

That's the interferometer.

There's the focus mechanisms right
here. Here's one focus mechanism.

This is the actual focus mechanism.
This is the flight hardware.
Wonderful.

Today the team are midway through
assembling their latest mission -

the giant Kepler space telescope.

But it's not scheduled to fly
until 2009, so currently
the spaceship is in bits.

This is where the primary mirror
is gonna sit, on top of this.

So that measures how well
you've got the optics aligned?

That's right, you
can measure how well it's working.

Leading the NASA team assembling
the space telescope is Bill Borucki.

It's magnificent, it's just
wonderful to see it come together.

We've been planning
this for years and years.

So to actually see it here...

This is the flight equipment,
this will go into space.

It's this
that will make our discovery.

I'm delighted to see all
the details that seem to be right.

When Kepler flies,
it will undertake a four-year
mission to seek out new worlds.

But it won't be looking for wobbles.

Instead, Kepler will be hunting for
planets that pass in front of their
stars, creating a tell-tale wink.

Looking at the star, it seems to
wink, it gets dimmer for a while.

Like it closed its eye for a second
and then opened it.

This is because the planet
moved in front of it
and blocked some of its light.

It happens in our solar system too.

We had a transit, Mercury going in
front of the sun fairly recently,
we could see that with a telescope.

For the wink technique to work,

a space telescope is essential.

Free from the interference of
Earth's atmosphere, it gives

Kepler an uninterrupted view of a
very special part of the galaxy.

Kepler only looks at
one area of the sky.

It's a good area for us, in that
it has a huge number of stars.

Kepler will scan the same
100,000 stars

over its entire four-year mission,

constantly measuring
the brightness of each one.

And from day one, it will be
sensitive enough to detect the wink

of an Earth-sized planet crossing
its sun, tens of light years away.

It's always very exciting, because
we've always wanted to know - are
there lots of Earths out there?

Geoff Marcy and Stephane Udry
and all these other people
are extremely competitive.

They want to find planets,
they want the answers too.

Well, we all do, and the best
way to do that is to co-operate.

There's a bit of a race going
on, but it's a delightful race.

The competition is lovely, and it
makes us get up in the morning,
go to work, and work a little harder.

So who's gonna
find the first Earth-sized object?

We are. Kepler's going to find the
first Earths in the habitable zone.

Between them, the planet hunters
are beginning to define the first
galactic map of Earth-like worlds.

At last, a phone directory for those
listening for a message from ET.

They're gonna allow us to
sharpen our gaze of the heavens,

where we're pointing these antennas,

trying to pick up a signal,
they're gonna tell us, "You don't
have to look at every star,

"these ones have planets", and
eventually they'll be able to say,

"These are the ones that have
planets the same size as Earth."

And ten years after that,
they'll be able to say,

"These are the ones with oxygen
or methane in their atmosphere.

"So they have some biology, and
it's up to you to find out if any
of that biology is smart or not."

Rather than the entire galaxy of 200
billion stars, in the future, SETI

need only tune into the handful of
star systems that Kepler discovers.

Everything has caused us
to become more optimistic.

We really believe in the next 20
years or so, we're going to learn

a great deal more
about life beyond Earth

detected that life

and perhaps even intelligent
life elsewhere in our galaxy.

Remember, there's a flip side to
this - it could be that advanced

technological civilisations, species,
are a rarity, one in a million,
maybe one in a billion.

If so, we humans could be
quite a precious rarity
in the Milky Way galaxy.

Maybe, in fact,
they're not out there watching us.

We may be the ones to be the first
to go out and explore the galaxy.

If you'd like to explore

Dr Frank Drake's famous equation

and come up with your own estimate

of the number of alien
civilisations in the galaxy,

log on to: