We've all grown up wondering if we're alone in the universe,
or if, one day, we might come face to face with an alien.
This is the story of our search for extra terrestrials.
Does ET really exist?
We're going on a journey to find out.
We'll visit alien planets in search of life.
We'll dive into the oceans of distant moons.
Here on Earth, we'll scan the universe for alien life.
And seek out the answer to one of the greatest questions -
is there life on other worlds?
Or, in all the vastness of space,
could it really be that we are completely and utterly alone?
We already know that we are not alone.
We share our planet with at least ten million other species.
This is life on Earth.
From the ordinary...
to the utterly bizarre.
So, what about other planets? Could they have produced life, too?
There's one creature on Earth that would like to know -
us!
If intelligent life could evolve here on Earth,
then why not elsewhere?
We're the first generation that might actually find out.
Scientists have begun to discover new worlds out there in space.
Places where one day we might encounter alien life.
So, how long before we find the answer
to the question we really want answered?
Is there anybody out there?
Look at the stars.
Each of them is a sun like ours, and our sun has planet Earth.
Could this really be the only planet anywhere that's full of life?
To find out, we must leave our own world behind.
Let's travel further.
Beyond our sun and out into space.
There's Mars, cold and inhospitable.
Next is Jupiter, a vast and lifeless ball of gas.
Then another gas giant - Saturn.
Then Uranus, Neptune and on.
All the other planets of our solar system
are barren worlds, devoid of life.
But beyond our solar system are the stars
and, remember, each of these is another sun.
400,000 million of them in a vast, swirling cloud.
The Milky Way - our galaxy.
And when you leave our galaxy behind,
you begin to realise just how vast the universe is.
Because each of these is a galaxy just like ours.
And these are clouds of galaxies.
Is it really possible that the only planet with intelligent life
is this one?
It's all a question of numbers.
If there are enough stars out there,
the chances that alien life exists could be very good indeed.
It's hard to comprehend just how many stars there are.
Each point of light is a whole galaxy,
billions of stars in every pinprick of light.
Look at a handful of sand.
How many grains? Thousands? Hundreds of thousands?
How many grains on a whole beach?
The numbers are too big to think about.
Well, think about this.
For every grain of sand on our entire planet,
there are a million stars out there in space.
A million stars just like our sun for every grain of sand.
Where there are stars, there may be planets.
And where there are planets, there may be life.
It's happened here. So, where is everybody else?
If there are intelligent beings up there trying to contact us,
their messages will be picked up here probably before anywhere else.
But to hear the voices of the planets, you need a big ear.
This is the biggest ear on Earth.
For the last 35 years, scientists have been working on a project
to settle the question of whether we're alone.
Their mission - to scan every star in the sky
for signs of alien life.
It's called SETI - the Search for Extra Terrestrial Intelligence.
And they're still doing it today.
CQ, 20 metres,
this is N6 Uncle Donald Kilowatt calling and standing by.
Seth Shostack is a SETI astronomer.
His job is to listen out for ET on the radio.
Radio cuts right through the gas and dust that hangs between the stars.
Radio is an easy communication medium for us and them to use,
so we figure they're probably using a lot of radio.
There is so much cosmic real estate, so many stars,
that it's hard to believe that this is only bit in the entire cosmos
that's populated by beings able to develop radio technology.
In the first decade of searching, SETI had nothing to show.
Then, in 1977, that changed.
A SETI computer detected exactly what they were looking for -
a powerful radio beam from another star.
Could it have been a signal from an alien race?
We may never know.
By the time they could train more instruments on it,
the signal had vanished.
It remains unexplained.
One sniff of success in 35 years of searching might put you off,
but Seth Shostack is undaunted.
If we do this for 100 years and don't find a signal, I'd be nonplussed.
I'd also be dead, but it would surprise me.
I think that this experiment is almost guaranteed to succeed.
But despite Seth's optimism,
finding extra terrestrials could take some time.
There are too many stars to search.
The problem is, our galaxy is truly immense.
This is us, just here. That star is the sun.
And this is the area we've searched so far for alien signals.
Not bad, until you see how many stars there are to search.
Finding extra terrestrial beings might seem like a daunting task,
but it may not be in vain.
We've started to find places where they could live.
Hawaii.
Far above the clouds of Big Island
sits the largest telescope in the world.
Scientists come here to search
for what they recently believed was impossible.
Evidence of planets circling around distant stars.
What object next, guys?
We'll continue stepping down 93 31.
All right, lining up on slit. We are ready for exposure.
And...shooting.
At first glance, their task seems hopeless.
Finding a planet around another star is like finding a grain of sand
on the moon.
But there's a trick to it.
Don't even look for the planet. Look at the star.
Geoff Marcy is one of a new breed of scientist -
a planet hunter.
If there's a planet going round a star,
we'll never see the planet lost in the glare of the star.
What we do, is we watch the star itself.
We watch if it wobbles in space.
It's very much like a hammer thrower.
As the hammer thrower wheels this huge mass around his head,
the hammer thrower wobbles around, pulled by the hammer.
Even if you couldn't see the hammer,
you'd be able to tell that he had a large mass at the end of a rope.
So, you can tell a lot about the planets going around a star
by just watching the star itself.
The idea that you can detect a planet
by the minuscule wobble it creates in a star is frankly astonishing.
Small wonder that success was a long time coming.
We started our planet search way back in 1986.
We went for nine years without finding anything.
And then in 1995, we started finding some.
And now we're finding planets so fast, we can barely keep up.
Every month, we find another two or three.
It's like we have to stuff the planets in our mouths
to pretend that we are keeping up, when, in fact, we're not.
There's almost no question
that there are literally hundreds of billions of planets
just in our own galaxy, many of which could harbour life.
One by one, astronomers were finding alien worlds.
But their hopes of finding alien beings soon faded.
Every world they've discovered appears lifeless.
These are gas giants, with no solid surface for life to live on,
and most are so close to their stars that the heat would be lethal.
To find worlds where aliens could live,
they'll need a whole new approach.
And this could be it.
A fleet of orbiting telescopes flying in laser-guided formation.
Each is many times more powerful than the Hubble space telescope.
When they are launched in 2025,
the telescopes won't be looking for the subtle wobble of a star.
They'll look straight at the planet itself.
They'll analyse its atmosphere, perhaps even tell us if there's life.
One day, we'll be able to look out into space
and see other worlds like ours.
I think, for almost any human being,
the picture of another Earth orbiting another star
would be like looking in the mirror,
but not one you see in the morning.
This would be a mirror of our whole solar system
and our beloved planet.
Seeing it mirrored in another star
would be one of the most exciting days in any life.
It is an astonishing prospect.
But if we're looking for alien life,
finding another planet so much like our own may not be necessary.
Our planet has everything life needs -
air, water, even sunlight, if you're lucky.
Conditions here are just right - for us.
But who's to say alien life would thrive on the same things?
What if it doesn't need sun or air?
Three kilometres down in the ocean
lies one of the harshest environments we know.
This is a volcanic vent.
The temperature here is over 100 degrees.
There's total darkness, pressures to crush a human to a pulp.
These creatures should literally be cooked.
But here they are.
If living things can thrive here, then where else?
Scientists' quests for new lifeforms have led them
to the most hostile environments.
This cave is the relic of a vast volcanic eruption
that occurred millions of years ago.
It's a lava tube - a gully left behind by a river of molten rock,
sterilised by the heat.
When the rock solidified, the tube was sealed off from the world.
There's nothing here to live on. No sunlight. Nothing but rock.
This truly is another world.
Penny Boston is a specialist in finding life
where it shouldn't exist.
The important thing about looking for life on other planets
is to keep your imagination as broad as you possibly can.
Try not to go with pre-conceptions,
because you never know what you'll find.
We can only go with our best guesses,
depending on what we find on Earth.
If Penny's team finds life here,
it is surviving conditions we used to claim were impossible.
If life can survive impossible conditions on Earth,
why not on other worlds?
And this is the first place to look - Mars.
Like the caves on Earth, there's little here for life -
not much water or air, nothing but rock to live on.
But perhaps the rocks of Mars
will hide similar wonders to those of Earth.
The miracle of life.
That is cool. Look how much it narrows down there.
Could that be a nematode?
Penny's discoveries in these caves
make the odds of finding life on Mars far higher.
And life on Mars could mean life on other planets as well.
If we find life on Mars,
I think that our chances of finding life beyond Mars,
and other places in the universe, go up enormously.
Two planets in just one solar system have life on them.
That means that life is a pretty common phenomenon in the universe.
So, where to search after Mars?
This is probably the strongest candidate for alien life
in our solar system.
It's one of Jupiter's 16 moons - Europa.
It appears tiny next to Jupiter,
but Europa is almost as big as Earth.
This is an ice world,
its surface frozen to a crippling 150 below zero.
Life here looks impossible.
But there is a plan to drop a probe onto Europa.
And if they do, scientists expect to find something amazing.
Beneath Europa's ice, there is an ocean.
What will we find there?
Scientists are almost certain the probe will find
deep sea vents similar to those on Earth.
Could the vents on Europa have life?
If so, it seems certain we'll find life across the universe.
I think there's frankly no doubt
that there must be life elsewhere in our galaxy, at least primitive life.
The bio-chemists tell us that if a planet has liquid water,
you will get replicating molecules.
The most successful would compete with other replicating molecules,
and there, voilą, you have life, ever more complex.
The question for which we don't have an answer
is whether our Milky Way galaxy harbours any intelligent life.
And that is the $64 million question.
So, are we alone?
The only intelligent creatures
in a universe teeming with simpler lifeforms?
It's hard to believe.
With so much life, some of those creatures
should surely have evolved into intelligent beings.
Perhaps beings a little like us.
That just begs more questions.
Where are they? Why haven't THEY contacted US?
After all, we've been making noise for more than 50 years.
(RADIO PLAYS ''MOONLIGHT SERENADE'' BY GLEN MILLER)
Here's the puzzle. Our radio broadcasts don't just reach us.
They also beam out into space.
(GEORGE W BUSH) I do solemnly swear
that I will faithfully execute the office of President of the USA.
Planet Earth's history is being broadcast to the universe.
So, if extra terrestrials exist,
they should already know that we are here.
(BILL CLINTON) I do solemnly swear...
(''ALL RIGHT NOW'' BY FREE PLAYS)
But even radio takes years to reach the stars.
(RONALD REAGAN) I do solemnly swear...
# I'm the urban spaceman, baby... #
(JIMMY CARTER) I do solemnly swear...
# And it's hi ho, silver lining... #
(RICHARD NIXON) I do solemnly swear...
Our radio broadcasts have beamed into space for five decades.
But in all that time,
they've only reached a handful of the closest stars.
To most of space, our planet appears completely silent.
(DWIGHT EISENHOWER) I do solemnly swear...
# Life could be a dream, sweetheart Hello, hello again, she-boom... #
There's this bubble of TV, if you will, moving out into space.
The earliest shows have gone 50 light years.
There's only a few hundred stars that close.
The aliens don't know we're here.
That's why we haven't heard from them.
Some day, as that radio bubble expands,
someone out there might learn that we're here, but when?
And what happens next?
It's the sheer size of the galaxy. That's the problem.
If extra terrestrials exist,
they could live on the other side from Earth.
It would take our radio and TV broadcasts
100,000 years to reach them.
We've only been sending out signals for around 50I
It just depends where ET lives.
Our signals have only reached a handful of stars,
but that may be enough.
This star is just receiving our first radio broadcast.
So, if ET lives on a planet round here,
they might have just found out that we exist.
If they choose to answer,
the message will take another 50 years to come back to us.
So we might be waiting a while
before we discover we are not alone.
Unless, of course, they had one of these.
Intelligent beings from another world.
Gee whiz!
What would they be like?
Almost certainly like nothing we've ever imagined.
For now, we can only speculate, but our search continues.
And that means that one day, we may actually find out.