How the Universe Works

Aliens...

Little green men.

A thousand eyes or one-eyed.

...sci-fi movie monsters.

Free-floating with tentacles.

Some unknown hyper-advanced civilization.

Could science fiction ever become fact?

I think it's really simple why Hollywood

is fascinated with the concept of first contact with aliens,

because that would be probably the greatest

scientific discovery in all of human history.

Problem is, our universe creates massive barriers

to meeting extraterrestrials.

It's almost as if the universe is deliberately

stopping us from making first contact.

We're searching the cosmos.

Will we ever find intelligent alien life?

Or are we alone?

captions paid for by discovery communications

Arecibo observatory, Puerto Rico.

45 years ago, it sent a powerful radio message

deep into space,

kickstarting our efforts to make first contact.

The Arecibo message was the first communication

or attempt to communicate with a possible civilization

out there in the galaxy or outside of our galaxy.

Today, that message is speeding towards

the M13 galaxy cluster

25,000 light-years away.

It contains information about our world...

where we are,

even the makeup of our DNA.

The purpose of this message was, of course,

like, trying to say hi,

and also, like, to light up this question about,

are we alone in the universe?

But what chances are there

that an intelligent alien race is out there

waiting to receive our message?

Do I think there's other intelligent life

out there in the universe?

The answer is a resounding yes. Yes, I do.

We know that life began on earth

pretty much as soon as our planet solidified.

So why wouldn't that have happened somewhere else?

If life has evolved on other worlds,

just how many alien civilizations

are out there that we could potentially contact?

Astronomer frank Drake developed an equation

to help answer this crucial question.

The Drake equation is a really admirable attempt

to apply some quantitative reasoning

to the probability, or the possibility,

that there is life beyond the earth.

You multiply the star formation rate

for stars in our galaxy

times the number of planets that each star has

times the probability

that you would have life forming on that planet

times the probability that that life form becomes intelligent.

And they estimated that there were about

10,000 intelligent civilizations within our galaxy.

Since the Drake equation was first proposed,

our understanding of the galaxy has radically transformed.

We have now discovered worlds outside our solar system...

exoplanets.

Exoplanets are being discovered all over the place.

There are about 4,000 of them now known,

and techniques are finding more every day.

Scientists believe what we've found

is the tip of the iceberg.

So if the cosmos is so good at making planets,

perhaps it can produce the conditions

to make life throughout the universe.

When the Drake equation was devised all those decades ago,

we didn't know that exoplanets existed.

And now we think that there are quite literally more planets

than there are stars in the universe.

So even if life is really rare,

there are an enormous number of chances

for it to take hold in the universe.

And for this reason, it is very likely that

there is life relatively abundant in the universe,

including an uncountable number of advanced alien civilizations.

This isn't science fiction.

It's just basic probability.

Probability suggests

a multitude of alien civilizations are out there.

So isn't it a little strange we haven't made first contact?

I think there's every reason to believe

that there are civilizations out there,

but we have no evidence of them yet.

Why haven't we found other civilizations out there?

One answer could be

the sheer vastness of the cosmos.

Look at all these lights out here

over the cityscape.

You could think of these lights as, like, stars in the galaxy.

Now, if there's 10,000 communicating civilizations

out there in the galaxy, you might think, "oh, man, look.

There's one right there right down the street."

The problem is

there are hundreds of billions of stars in the galaxy,

which means that maybe our nearest neighbor

that we can communicate with is not right there

but way across the city.

We live in the suburbs of the milky way

75,000 light-years from the furthest edge.

Radio signals travel at the speed of light.

This speed limit means that any signal sent

to the opposite side of the galaxy

would take 75,000 years to reach its destination.

The thing you have to remember

is the galaxy is gigantic.

Even if there are 10,000 civilizations in the galaxy,

it's possible that the distances between stars are just so huge

that we're never gonna be able communicate with each other.

So the 45-year-old Arecibo radio message

could still be tens of thousands of years away

from any potential alien civilization.

The target was 25,000 light-years from here.

The message is now 45 light-years from here

'cause it's traveling the speed of light,

so it's really far from the target.

The vast size of the universe is a huge roadblock

to making first contact, and the laws of physics

prevent radio signals from overcoming it.

You just cannot go faster than the speed of light.

So our galaxy may be filled with life, filled with civilizations,

but they're so far away.

I don't want to be the bearer of bad news.

But the universe is just really, really far too large.

The universe may be large,

but we're putting the most advanced technology on earth

into action to try and speed up the search.

There really is a serious, scientifically valid way

to go looking for other civilizations.

And the breakthrough listen project is really

the best thing we have right now.

State-of-the-art facilities around the world...

radio telescopes, optical telescopes, as well...

are all looking up to the sky together.

Breakthrough listen is targeting the 1 million stars

and 100 galaxies closest to earth.

It is the most comprehensive search

for alien communications ever undertaken.

If there was an aircraft giving off a radar signal,

and that aircraft was around any of the 1,000 nearest stars,

the breakthrough listen project could hear that.

So if there's something out there

that's actually giving off a signal,

breakthrough listen has a chance to find it.

Breakthrough has started by listening in

on the nearest 1,700 stars to earth.

So far?

Silence.

This is the wonderfully,

beautifully frustrating position that we find ourselves in.

We haven't heard anything yet.

So we're in this position where a negative result

doesn't mean there aren't civilizations,

but we have no proof that there are.

Breakthrough listen is just beginning its hunt.

There's much more real estate in the cosmos

for it to search.

It's a big job, demanding a lot of patience.

If you go through Drake's equation

and find this number

of 10,000 intelligent civilizations out there,

there are something like 250 billion stars in the galaxy,

so that's only 1 civilization per 25 million stars.

That's a lot of cold calling.

The size of our universe

means we could be waiting a very long time

to pick up any alien communication.

But even if we pick up a signal,

it may have arrived too late.

If we do receive a message,

given that it probably took years to get here,

that civilization could be long gone.

So are we simply too late?

Have any aliens out there already died out?

Earth has orbited the sun

for over 4.5 billion years,

time enough for humankind to evolve into an intelligent

and technologically advanced species.

But compared to the age of the universe,

planet earth is just a kid.

The earth is over 4 1/2 billion years old,

and we think it's taken this long

to create the first technological civilization...

us.

There are star systems out there much older than we are.

The universe is 13.8 billion years old.

We tend to think we're hot stuff, right?

We're technologically capable, we can build rockets,

and we can listen to radio waves.

But a typical other intelligent advanced civilization

would be literally millions of years ahead of us

in technology.