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Science's top alien hunters are combing the galaxy

for extraterrestrial life.

And what they're finding could change our lives forever.

It turns out that aliens are likely everywhere.

There's an exotic zoo of planets out there.

Alien life popping up everywhere.

Some would be masters

of intergalactic travel.

Open your mind to the possibility

that they are thousands, millions of years

more advanced than us.

And they could arrive in your backyard

any minute now.

An advanced civilization might well venture

here as a place to colonize.

If there is any time for the aliens

to arrive on Earth, it is surely now.

But when they get here,

will the extraterrestrial visitors come as our friends?

They would make contact in order

to learn about our culture.

Or as our conquerors?

As soon as the aliens spot that we're here,

they're probably going to destroy us.

If it comes to blows,

it's going to be like Kermit the Frog versus a T-rex.

78% of Canadians think

that extraterrestrial life is out there,

and leading scientists are convinced

the aliens will come to Earth.

But seeing as otherworldly visitors

haven't been down to meet us yet, it makes you wonder.

Are we alone?

Some scientists say that perhaps we

are the only life forms in the universe.

Give me a break.

I mean, how many stars are there out there

in the universe, anyway?

The Hubble Space Telescope can see about a hundred

billion galaxies.

That's the visible universe.

Each galaxy consists of hundreds billion stars.

Do the math.

100 billion times 100 billion is 10 sextillion.

That's 1 with 22 zeros after it.

As in our own solar system, where there's a star,

there are planets, billions of worlds for an alien to

call home.

There definitely are aliens in outer space.

They're out there.

But if extraterrestrial life isn't

just the stuff of Steven Spielberg's imagination,

then where does ET live?

Science fiction has long been obsessed

with the idea we earthlings might have

nasty neighbors from Mars.

3, 2, 1, 0, and liftoff

of the Atlas V with Curiosity.

And in November 2011,

NASA launched its first unmanned mission

with the specific aim of finding

extraterrestrials on the red planet.

Now, unfortunately for sci-fi fans, the Mars of today

is most likely dead.

But NASA believes there were once huge bodies

of water on its surface.

Touchdown confirmed.

For astrobiologist Chris McKay, studying the dried

up oceans of Mars could reveal carbon

based life once lived in its waters,

just as it does here on Earth.

Each day, I'm involved in the operations

of the Curiosity Rover in Gale Crater,

ancient lake 50 million miles away on Mars.

Salt-rich environments like the one

here are a good model for life on Mars.

So by studying the kind of organisms that

live in an environment like this,

we get a glimpse of what life might have been like on Mars

as it got drier and drier and colder and colder.

Eventually, the water all goes away

and we're left with a salt crust,

and that's a very good mechanism for preserving

evidence of that life.

So my hope is that we trundle along on the surface of Mars.

We drill down and pull out a sample,.

And in that salt is preserved the organic remains

of life that was growing when it was a saltwater pond.

Now, you might think that digging up long dead

pond slime isn't exactly a mind-blowing moment

of first contact.

Like saying "ack ack ack" to this guy.

But for scientists, finding organic matter on Mars

would be the biggest discovery in human history.

Because the chemical makeup of life

here could prove that aliens can come into being anywhere.

Life on Earth uses only left-handed amino acids.

Think of driving on the road.

We drive on a certain side of the road,

the right or the left.

So there's a handedness there.

If you are raised in one country where everyone was

driving on a certain side of the road

and you woke up one day and everyone was driving

on a different side of the road,

you would know that you were in an alien country.

If we go to Mars and find that all the amino acids there

are right handed, then that would

be indicative of a biology that's

very different from ours.

Alien life.

Then we would know that life started on Mars

separately from life on Earth.

And if life started twice in our own solar system,

once on Earth and once on Mars, that

would be very strong evidence that life

is popping up everywhere.

Yeah, I'd be very excited to know that.

If aliens made from the same carbon

compounds as us are alive and kicking on other worlds,

how do we find them?

To help, planetary scientists are

using this, Kepler, the most powerful deep space

observatory ever launched.

Right now, it's incredibly

exciting because every month, dozens of planets are found.

I'm sure in our own galaxy, there

are hundreds of millions to billions of planets

that could be habitable.

So just from the sheer number of planets out there

and the diversity and characteristics,

there could be way more alien life than we think.

At MIT, Sara Seager is scanning the galaxy,

but she's not interested in just any planets,

she's looking for prime alien real estate.

Worlds like Earth.

Our favorite kind of planet we're always looking

for are terrestrial planets.

These planets would be made of predominantly rock,

and these could be bigger than Earth.

We've seen evidence for planets that are a few to several

times the mass of Earth.

And those planets we think are ideal for life

if they're in the so-called Goldilocks zone.

Like the fairy tale of the Three Bears,

astrophysicists choose habitable planets like

Goldilocks chooses porridge.

A long way from its sun, the planet is too cold.

Too close means too hot.

But somewhere in between, like Earth,

could have the perfect conditions for alien life.

But finding these planets isn't easy.

The problem is that that faint Earth

is right next to a very, very, very bright star.

In fact, our sun is 10 billion times brighter than Earth.

That's a huge, huge number.

Looking for an Earth twin next to a sun like star

is like looking for a firefly 6 inches

from a searchlight, where that firefly and searchlight

are thousands of miles away.

It's painstaking work, but the results

have been incredible with potentially habitable planets

being discovered every month.

So let's take a look around.

20 light years from Earth, this world

has one side scorching hot, the other, frozen solid,

and a habitable sweet spot between the two.

And what about this little hideaway

which orbits a red dwarf star?

Aliens here could bask in blood-colored sunlight

and Caribbean-like heat.

The implications of these discoveries are mind-boggling.

The next step is to take a closer

look using new technology.

We're building a nanosatellite

called Exoplanet SAT, and this is the real size and real mass.

It will be a tiny space telescope

with deployable solar panels for power

that will point very precisely at a sun-like star,

searching for Earth-sized planets that go in front of it.

And we plan to launch a fleet of exoplanet SATs,

each identical to the next, and each studying their own star.

Exoplanet SAT may well find the first planet

to have alien life.

There could be countless Earth-like planets

able to support carbon-based life.

But what if the real ET were a form of life

unlike anything on Earth?

We have this old 18th century idea that

there's life and then there's death

or things that are not living.

That's it.

Nothing in between.

But now we have viruses, and now we

have a whole rich biochemistry of things in between.

So we now realize that this old idea of life versus non-life

is a dichotomy that should have gone out 100 years ago.

There could be shades of life, gradations of life,

just like perhaps there are gradations of intelligence

as well.

Life, it seems, can take almost any form.

Does that mean aliens could really

be like a classic B-movie space creature?

Could the Blob be real?

This guy thinks so.

So what we're trying to do in my lab

is to make new blobs, inorganic blobs

that can be ostensibly alive.

To understand how the blob might materialize,

chemist Lee Cronin is first looking back to how life got

started on Earth.

About 4 billion years ago,

Planet Earth was dead.

There was no life on it.

And a few billion years later, it was teeming with life.

In the chemical soup of ancient Earth,

reacting elements battled it out, and voila,

carbon-based life was born.

But what if those chemical ingredients had been different?

I wonder if life just

took the available chemistry and used that to start biology.

And so does that mean that maybe we could start life again

and we could do it with a different chemistry set?

So could ET be based upon metal or something that isn't carbon?

Putting this theory to the test,

Cronin is throwing caution to the wind.

He's making a pet alien blob of his own.

Recreating the chemical competition that sparked life

on Earth, but with non-organic matter

like silicon and even metal.

What I'm going to do here

is just mix some chemicals together.

And by mixing these chemicals together,

a reaction will occur.

And this reaction will go backwards and forwards

and you'll see a color change.

So what we're trying to do is set up a competition.

Life, after all, is about a competition.

And evolution uses this competition

to make things better.

You know, the fittest survive.

And so what we have in this chemical reaction here

is an example of some chemistry that can switch, change team,

if you like, and set up lots and lots

of different properties where there can be a competition.

Whether red is more desirable than green, or green

is more desirable than red.

And then someone's going to win at some point.

And there may be a point, just a point

where at the end of the experiment,

something does crawl out that is alive.

And don't worry if it escapes in the environment,

because we have used very sophisticated

inorganic materials.

There will be none of those out there on the Earth,

so it will die and not take over the planet.

Thanks to Lee Cronin,

we're hopefully safe from a blob attack, for now.

But if aliens can be made from very different stuff

to life on Earth, that means they

could live almost anywhere, no matter how extreme.

As astrobiologists close in on alien planets,

they are now ready to reveal what these otherworldly beings

actually looked like.

And the truth is way more weird than Hollywood

has ever imagined.

Our image of aliens has mostly come from movies

and conspiracy theories.

There's the ugly, scary ones; the big-headed, brainy ones;

and, of course, the easy on the eye variety.

Then we're the only men on the whole planet?

Yes.

But if life really does exist on other worlds,

then what will aliens really look like?

For astrobiologist Lewis Dartnell,

the real face of life on alien worlds

is far stranger than fiction.

There's an exotic zoo of planets out there.

Many of them aren't anything like the kind of planets we

find in our own solar system.

Space telescopes have spotted

thousands of potential planets for extraterrestrials

to call home.

Using this data, Dartnell is zooming in on alien worlds

to check out what the locals might look like.

First stop, an ocean planet with a surface temperature

of 30 degrees Celsius.

One kind of planet common in the galaxy

is a water world, a planet with a very deep ocean, perhaps

hundreds of kilometers deep.

Life in these water worlds, it might look pretty recognizable,

like the ray we have behind here or these more

torpedo, bullet-shaped fish.

But how can we know what's swimming

around on a world 5,000 trillion kilometers away?

The answer is evolution.

By comparing conditions on Earth with the environment

on the alien planet, Dartnell can theorize how

life there may have evolved.

So the propulsion mechanisms

that are adapted and evolved by alien fish

would be pretty similar to the propulsion mechanisms

that we find on Earth, simply because they're solving

the same survival situation with the means

that are available to them.

Kilometers below the ocean's surface,

it's pitch black.

Alien fish evolve elaborate ways to hunt.

So what you might have

is alien fish with panels of bioluminescence

down their sides so they can flash signals to each other,

coordinate their attack, and all swoop

in at the same moment, unbeknownst to their prey.

Like on Earth, hunters become hunted.

And on a world covered in deep oceans,

it's likely alien marine predators will evolve

to be very big and very scary.

But on super sized habitable worlds like this one,

42 light years away, alien beings

would evolve to perfectly suit the mega planet's heavy gravity

and rule the vast open skies.

They would have stronger gravity,

but they'd also have a thicker, more dense atmosphere

pulled down around the planet.

So flight would become easier on a super Earth

because you'd be able to generate lift.

But like on Earth, not

every part of the alien bird has evolved

just for better flight.

So with soaring animals darting

between the clouds, we'd expect them to have things like fronds

streaming behind them, which hamper the aerodynamics

but advertise their fitness as a mate.

Even more amazing, Dartnell

believes life exists on ice worlds, way

colder than an Arctic winter.

Under such extreme and unrelenting environment,

there'd be nothing but hardy microbial life, the kind

of bacteria that we find living inside solid icebergs on Earth.

They may grow by a very exotic form of energy,

not by absorbing sunlight.

We do find on Earth bacteria that have joined end to end

to create biological wires.

And on an alien ice world, you might have long fibers

of bacteria all joined together to create vast networks

of biological circuitry to extract

energy in a magnetic field.

A much stranger alien hangout

is the carbon planet, with its rivers and oceans of oil

and a thick inner shell made entirely of diamond.

Yep, a bling planet.

Life on the diamond world, in the oily oceans

would have to be even more exotic, even more alien,

because they wouldn't be based on liquid water at all.

Here, solitary aliens hide in lakes of oil

and produce bursts of energy to attract prey.

Zooming in to his final destination,

Dartnell thinks the biggest, baddest extraterrestrials

of all could live on a planet much like our own,

but where evolution has taken a very different route.

For the best possible chances

for life, especially complex animal life like ourselves,

would be an Earth-like place, a true twin of our home world.

But even if we were to rerun the story of evolution

on Earth, you wouldn't expect the specifics of life

to come out the same because there's

so much chance and randomness inherent in the process

of evolution.

So perhaps on an alien Earth-like world,

there's an octopus species which

has developed a hard exoskeleton to support itself

against the gravity once it's come out

of its aqueous environment.

So in a galaxy where life can evolve

in an infinite number of scary ways,

what are the chances of a planet developing

intelligent, self-aware life like Yoda, Dr. Who,

or even Dr. Zoidberg?

Well, as it turns out, scientists

think it's possible aliens are not just smart.

They're way smarter than us.

And they've taken evolution to the next step

by becoming a robot species.

In our galaxy alone, there's

an estimated 60 billion planets that

could be home to alien life.

But is ET just a fish, a bird, or a blob?

Or have otherworldly beings created great civilizations

way more advanced than us?

Like, say, the Vulcans?

In other words, will aliens be smart like Spock?

There are three basic ingredients to become

an advanced civilization.

First, you have to have stereo eyes, eyes of a hunter.

Because predators are smarter than prey.

That's why we say sly fox and dumb as a bunny.

If you are a predator, that means you have

to have camouflage, stealth.

You have to be able to outsmart the prey.

Second, you have to have an opposable thumb, a hand,

a claw, a tentacle, something by which you can

manipulate the environment to create machines

and eventually starships.

And third, language.

You have to be able to accumulate

knowledge between generations.

The knowledge you get from this generation

has to be handed down in order to create

vast civilizations capable of taking you to the stars.

If alien species are intelligent,

the evolution of language will be essential.

But the way ETs talk to each other

could be far more advanced than how we chat.

Aliens are more than likely not going

to be individual entities.

They will be connected into a Borg.

Would be much more powerful.

Be very, very difficult for us to understand, to reason with.

And the only way we're going to understand them

is if we can communicate in the same sort of way.

Kevin Warwick is an expert in cybernetics.

He believes some aliens are so smart,

they will have taken control of their own evolution,

merging with technology.

Forget smartphones.

That's old school.

Cyborg ETs can communicate using only their minds.

And Warwick is doing the same.

Taking science to the edge.

Turning himself into the world's

first cybernetic organism.

I had this brain gate

implanted into the nervous system of my left arm,

and we linked my nervous system to the computer

and onto the internet.

As I opened and closed my hand, my brain signals also opened

and closed the robot hand.

So the hand has little sensors in the fingertips.

And I was able to receive feedback from those sensors

so I could feel with signals in my brain,

how much force the robot hand was

applying to different objects.

As long as there's a network connection,

your brain and your body don't have to be in the same place.

This proves aliens could use

thought to communicate with robots.

The next stage is for Warwick to talk

telepathically with another living being,

as he believes aliens do.

So he's enlisted an ET stand-in, Mrs. Warwick.

My wife also had electrodes pushed

into her nervous system.

So every time she closed her hand,

my brain received an electrical pulse.

So it was communicating directly nervous system

to nervous system.

Aliens clearly will be communicating

directly brain to brain, full-on synthetic telepathy.

Could an advanced alien species work as one

nonspeaking collective mind?

It sounds far out.

But something similar happens here on Earth,

right under our feet.

Ants have a collective type

of intelligence, which means they're extremely powerful.

And if you destroy one ant, it doesn't

really have much of an effect over the overall ant colony.

It's the colony.

A more networked type of intelligence that's important.

Take the Borg from "Star Trek," for example.

Throwing in a bit of extra machine intelligence.

So it's a super intelligent network.

If the extraterrestrials

are as technologically advanced as the Borg,

they could be capable of almost anything.

Astronomer Geoff Marcy believes some ETs

will create power in a way that is straight

out of science fiction.

If some other advanced civilization needed

enormous amounts of power, there

is a way to collect vastly more amounts of energy

by simply capturing the light from the host star.

On Earth, we collect small amounts of sunlight

to convert to energy.

But technologically advanced aliens

could have electricity demands so immense,

they need all the star power they can get.

The best way is by using solar panels

like you see here.

And the idea is really very simple.

One should attempt to pave around a star in an effort

to capture that starlight, convert it

into electricity, and power the needs

of the advanced civilization.

So imagine paving a sphere around our sun

and collecting all of the sunlight that is emitted.

This enormous alien solar power station

is known as a Dyson sphere.

But as you might imagine, building one won't be easy.

An advanced civilization

would start off for economic and engineering reasons

by putting one solar farm in space, then,

when possible, a second solar farm, and then a third, and so

on, slowly but surely building up

a complex swarm of solar farms around the host star.

Any alien civilization that's attempting to build a Dyson

sphere is going to have to face some very serious

engineering challenges.

For one, the sheer amount of material,

the challenges of the structural integrity, how it

can survive against comets and very severely against the star

in the center moving and maybe crashing into the Dyson sphere.

So if aliens this smart do exist,

it's fair to assume they have a good idea

of what's happening in their galactic neighborhood.

And they might know all about us.

So will extraterrestrials make first contact,

or have they tried already?

August 1977, a radio telescope in Ohio

picks up a mysterious signal.

It's a narrowband signal.

A lot of electromagnetic energy at a narrow frequency.

The signal comes from deep space.

And the implications are out of this world,

leading astronomers to wonder if it's a message from aliens

and ask, are we missing ET's calls?

When the observer was looking through,

he was so excited when he saw that signal that he took

the printout and he wrote "Wow!"

in the margins of the signal.

The Wow! signal is exactly the kind of signal

that we would expect to see from ET.

The scientists monitoring the wow signal

are part of SETI, the Search for

ExtraTerrestrial Intelligence.

At the time, they believed it could be a message from aliens.

But after 72 seconds, the signal stops

and is never heard again.

The aliens, it seems, hung up.

Many different astronomers

have gone back and looked at it for hours and hours

at many different wavelengths, and no signal

has ever been detected from that position again.

No one knows why it came only once.

And today the Wow!

Signal is in the X Files, along with other mysteries,

such as Area 51 and the Nazca Lines.

But if the signal was from outer space,

said SETI astronomer Andrew Siemion wants

to be ready if ET calls again.

I wouldn't be doing radio SETI experiments if I

didn't think there was a chance that we could detect a signal

from another technology.

SETI is ramping up the search, collecting more

space data than ever before.

We actually have several radio experiments

going on at any given time.

And right now we were showing a display

here from the Arecibo radio telescope in Puerto Rico.

Any time anyone is using the telescope,

our instrument is always running in the background,

looking for signals from ET.

So when we see a signal like this,

the next thing we want to do is apply additional tests

to try to rule out the signal as coming

from some kind of interference on the surface of the Earth.

The next thing that we would do is

we would request time on a large radio telescope

to try to reobserve that sky position.

If both widely separated radio telescopes in maybe,

you know, two different continents

see the exact same radio signal when they look at that position

in the sky, then we can be pretty sure that it's actually

coming from a distant planet.

In that case, we would notify the world.

SETI is maximizing the chances of hearing

new radio messages from space.

Problem is, the telescopes generate tons of data.

To analyze it, SETI astronomer Dan Werthimer is

enlisting the people of Earth.

So we're asking people

all around the world to help us hunt for radio signals

from other civilizations.

And the way to do that, if you're interested in being part

of this search, is to download the SETI@home

screensaver program.

Everybody is assigned a little part of the sky.

And when you install that screensaver,

you're talking to this computer in this closet.

This computer is coordinating the activity

of 8 million SETI@home volunteers

all around the world.

This is not a very big computer by itself,

but it's the central brain of the world's

largest supercomputer.

8 million people, all looking for alien life.

Now you can be an alien hunter too.

And with us doing all the grunt work,

this is SETI's biggest mission yet.

Sounds great.

Unless it's just a shot in the dark.

Because if you belonged to some futuristic alien race,

would you really still send messages using

old-fashioned radio waves?

Biological engineer Sriram Kosuri

thinks there's a better way.

He's doing cutting-edge research that suggests ET could

send messages biologically instead,

stored on molecules of DNA.

So if you wanted to send a bunch of messages

into space to other planets, DNA would actually be

a very useful way to do that.

DNA storage can be incredibly dense.

So in theory, you can store 100 billion

DVDs in about a gram of DNA.

Holding the genetic blueprint inside every living

organism, DNA is nature's very own high-capacity hard drive.

And Kosuri believes it's perfect for

interstellar travel.

And the really nice aspect of that

is that if you were to send information over long distances

to many places, it takes less energy to send

something that's less massive.

DNA, as a chemical, is very long lived.

So it's known to last very stably over thousands of years,

especially in dry environments like in space.

But how would DNA be sent through space to Earth?

Astrophysicist Paul Davies thinks advanced aliens could

use microscopic spacecraft made from organic matter

that could already be here.

I think we should look for alien messages

in a bottle.

Now, how would those messages be etched?

And what would the bottle be?

Supposing the aliens had decided to create little

nanomachines or even to co-opt nature's own existing machines,

namely living cells, and upload information into it--

and the bottle itself could be the coat

of a virus or a living cell.

And I don't think it's any more crazy that we would discover

a message in the genome of a bacterium

than to discover a message in radio

waves coming from the sky.

From surfing deep space for radio waves

to sifting the galaxy for ET DNA, alien hunters

are primed for messages from life out there.

But is this enough to guarantee first contact?

We're just learning how

we might communicate with other civilizations,

and it might be that our ideas are completely wrong.

If you had asked me 200 years ago what to look for,

I would said smoke signals.

So if you'd asked me 200 years from now,

it might be something completely different-- tachyons

or subspace communication or something

that we don't know anything about yet.

But while SETI waits and waits and waits some more,

a more direct way to let ET know we exist

is to open all hailing frequencies

and say hello to them.

For decades, scientists

have sent a steady stream of messages into the cosmos,

aimed at grabbing the attention of ET.

Voyager 1 left for deep space with a gold disk containing

information about Earth--

music, pictures, and even a message

from President Jimmy Carter.

More recently, we've beamed text messages

to known habitable planets.

But so far, no reply.

So how do we get ET's attention?

Dr. Doug Vakoch thinks the reason aliens don't

respond to our messages is because they

don't understand them.

So he's looking for some common ground.

We are a mathematical species

and that mathematics is the universal language,

the key to communicating with another civilization.

For Vakoch, encoding messages

in the language of science, rather than, say,

Urdu or Welsh, is the key to starting

interplanetary dialogue.

But Vakoch doesn't want to teach aliens algebra.

Because using math, we can describe to aliens

all the wonders of our world.

And here's a great example.

We start with a very simple number series

called the Fibonacci series.

We start with the number 1 and add it to itself, 1 plus 1.

We get 2.

1 plus 2 equals 3.

And 2 plus 3 equals 5.

And what we find is that if you connect those squares together,

you get this spiral that we see in shapes throughout nature.

We see it in the spiral of a Nautilus shell,

spiral galaxies.

We see it in structures that we humans

have created as well, like the facade

of the Parthenon in Greece.

And so by starting with basic mathematical principles

like counting, we can go well beyond a description

of our physical world to describe something

like our sense of beauty.

Vakoch's ultimate goal is not only

to send aliens info about Earth, but to tell them what

it means to be human, warts and all.

We're creating CGI images, computer graphics that

show human beings in their full three-dimensional form,

in motion and also doing things that

really matter to human beings.

Well, one of our highest ideals is altruism.

But how would we convey that?

Well, we can start by showing a person who

sees someone else in need and going

down and helping that person.

And in this case, it turns out well for the altruist,

but that's not always the case.

But of course, altruism also implies a sense of choice,

that you might see someone in danger.

We also have the option of turning and walking away.

So when we think about the messages we want

to send to an extraterrestrial, we

may want to talk about our ideals,

but also how well we meet those ideals and, in some ways, how

we fall short.

Showing the galaxy mankind's dark side

might not be such a good idea.

But even if ETs do pick up our messages

and they didn't flunk math, will they care?

What will aliens think of us?

The aliens probably already have been scanning us.

I mean, for the past 50 years, we've been sending perhaps

the best of our cultural archives

into outer space, like "I Love Lucy" and "Leave It to Beaver."

And any star within 50 light years of the Earth

will pick up our cultural emissions.

And they'll be convinced, there is no intelligent life

on the Earth. Earth?

No. Crossed it on the list.

Intelligent? No.

We've been scanning their TV emissions.

No way.

We have this prejudice that the aliens are perhaps a hundred

years more advanced than us.

Open your mind to the possibility

that they are thousands, millions of years

more advanced than us.

The distance between ants and our civilization

is very small compared to the technological distance

between us and an advanced civilization that

could reach us from the stars.

I mean, if you're walking down a country road

and you see an anthill, do you go down to the ants

and say, I bring you trinkets, I bring

you beads, I give you nuclear energy,

take me to your ant queen?

Or perhaps you may want to step on a few of them.

So what do we have to offer them,

if their technology is thousands or millions of years

more advanced than us?

A futuristic alien race

may have no interest in humanity,

but we might well have something they do want.

Planet Earth itself.

Since the 1970s, nations have sent

probes into space to search for evidence

of extraterrestrial life.

So if we've been doing it, have they?

Are aliens watching us?

The first thing that comes to mind

are things like probes.

An alien probe might have fantastic

information processing capability of

enormous intellectual power.

And it's not inconceivable that over the history of the Earth,

there's been some alien technology in the solar system

or right here on our home planet.

Paul Davies believes an intelligent alien species

could be analyzing Earth right now.

We could be surrounded by such things

without even knowing about it.

It sounds like a sci-fi fantasy,

but extraterrestrials could be watching us in real life.

And cyberneticist Kevin Warwick thinks the aliens alien's

next step would be to launch a more

sophisticated recon mission in the form of cybernetic avatars.

It may well be robots

that actually appear on Earth to start with.

Not the aliens themselves.

The aliens would be on a distant planet,

maybe galaxies eons away, and controlling the robots

that we see here directly as extensions of themselves,

if you like.

So their thoughts and feelings are controlling the robots,

and information's being fed back.

I think we should be able to get some idea of what

the alien life form actually is like from the robots that

appear here.

As we have robot hands on our robots that we send out,

they may have some sort of that is

similar to the original alien life form.

So if extraterrestrials

are spying on our planet and us right now,

what will aliens want from us?

Astronomer Geoff Marcy has a shocking theory,

that some extraterrestrial visitors

won't be interested in mankind at all, but they'll love Earth.

An advanced civilization

would surely recognize the Earth

as one of those precious planets

with that combination of liquid water and continents.

They might well want to venture here, perhaps as a place

to colonize for their own development,

their own proliferation.

So does this mean, with its abundance

of natural beauty and nice beaches,

aliens will see our charming little planet as

the perfect vacation getaway?

Marcy thinks not, because aliens will more likely come

to Earth on serious business.

We know there are natural resources here

on the Earth that we cherish.

I imagine that other advanced civilizations might

cherish those same resources.

We may be living on a more precious planet

than we realize.

In the movie "Avatar,"

humans travel to an alien world to mine its natural resources.

And Dr. Jan Zalasiewicz believes that's exactly

what ET will do on Earth.

[Speaker 13] And when the aliens come here

to this corner of the galaxy, this

is the Earth that they will come.

Because here they will find a wealth of minerals and metals

they will not find anywhere else.

On Earth, aliens will find a planet

with a priceless geology that is

formed over billions of years.

So why is the Earth so special

compared with, let's say, outer space?

Now outer space is just dull in terms of minerals.

Maybe a dozen different sorts floating in the mineral dust.

When you form a star system, then the number of minerals

goes up.

The star lights up, the dust melts, then you maybe get

50 minerals appearing in that.

We begin to form a planet, a planet the size of Earth.

You maybe then have 500 minerals.

The same as the moon.

The same as on Mars.

Then let us start the engine of the Earth.

Let us start plate tectonics.

Ocean split apart.

Ocean crust sinks into the mantle of the Earth.

And all of that distills more minerals out of the Earth.

Then we have a key moment in the history of the Earth.

Life appears.

Meeting life here may not be on the agenda

for super advanced aliens.

But the fact living things exist on Earth

makes our world even more resource rich.

It's when life learns a different trick

to produce oxygen, then for every mineral,

you have an oxide.

And because the world is wet, it has free water.

You have a hydroxide as well.

And that takes a number of minerals on the Earth,

up to about 4,000.

Our planet is a treasure trove for aliens.

And by picking up our space greetings

and seeing what we earthlings have been up to,

ET will know where to find our resources and how to use them.

And look what humans have done here.

Here, 200 years ago, they found a lump of copper ore

the size of a skyscraper.

And it's gone.

It's been converted by humans into all manner

of goods and objects.

And this is what humans have done all over the Earth.

And they've made new metals, new minerals that

have not been found in nature.

So if there was any time for the aliens to arrive on Earth,

it is surely now.

If otherworldly beings send probes to Earth

and they like what they see, it won't

be long until intelligent extraterrestrials

decide to check out our planet for themselves.

Our galaxy contains around 60 billion planets

that aliens could call home.

Astronomers are sending messages into space,

trying to reach them, but they could be watching us already.

And it may only be a matter of time

until the aliens come to Earth, but are

we prepared for first contact?

Are you wondering, where are the men in black?

OK, so he's not exactly Will Smith,

but Paul Davies is chief of the post-detection task

group for SETI, the Search for ExtraTerrestrial Intelligence.

It's his job to figure out what to do when aliens reach out.

If we did have some sort of contact with

an alien civilization, then it's not

going to be like in the movies like "Men in Black."

It basically boils down to a tiny group of people.

There's the SETI scientists themselves

who listen in for signals, and then there's me.

Our job is to come up with some sort of protocol or plan

in the event that there is irrefutable evidence that we

are not alone in the universe.

What do we do next?

Who do we tell?

How do we respond?

Should we respond?

And who speaks for Earth?

But no matter which VIP gets to speak for mankind,

be it the president, the queen, or Oprah,

don't expect to see the moment of first contact live on TV.

Any sort of first contact scenario

is likely to happen in a way that nobody anticipated.

So it's really important to try to prevent this leaking out

to the media before the scientists are

really ready to evaluate what they did involve.

These steps involve all sorts of checks

to make sure the signal is genuine

and then informing various scientific and government

organizations in a certain sequence.

But is it really just

this guy standing between us and a possible

alien apocalypse?

Not quite.

If aliens break radio silence, NASA

will mobilize its men in white, the Office

of Planetary Protection.

Here, Dr. Carlton Allen's crucial task

is to analyze the contamination risk to Earth

from extraterrestrial exposure and pinpoint

any biological threat we might pose to them.

[Speaker 14] The idea from "War of the Worlds"

that Martians came to Earth and died from the common

cold sounds bizarre.

But in fact, we don't know what happens when

ecosystems collide like that.

And that's what the field of Planetary Protection is about--

to protect the Earth from materials coming from space.

Keeping Earth safe from alien germs,

the Planetary Protection Department

has been busy since the 1960s.

When NASA went to the moon, its returning heroes

were quarantined.

And today, Allen's focus is on contagion from the red planet.

We're looking now at missions to bring back

samples from the planet Mars.

The story of planetary protection

goes to a whole new level.

And there may be places on Mars where some extreme forms

of Martian life could exist.

As we explore Mars, we certainly

don't want to contaminate any parts of the planet.

But we also, as we bring back samples,

we want to make very sure that we

don't contaminate Earth with any kind of Martian organisms.

An alien plague spread

by interplanetary microbes could decimate humanity

as viciously as any alien invader

dreamed up by science fiction.

But as mineralogist Mike Zolensky knows,

these mini ET's could unlock one of the biggest

questions in astrobiology.

55% of Canadians think otherworldly beings

may have been to our planet, but what do scientists think?

Are aliens here already?

So are aliens here already?

I don't know, but what I do know

is that the building blocks of life

are arriving on Earth every day.

And they've been arriving on Earth

for 4 and 1/2 billion years.

They're arriving in meteorites, asteroids, and comets.

Meteorites are flaming

balls of interplanetary rock that have smashed into Earth

since the dawn of time.

Once, they were a mystery.

But now, thanks to new imaging technology,

Zolensky can see what's inside meteorite fragments.

The results are amazing.

[Speaker 15] This is a meteorite

that fell in West Texas.

And amazingly, inside this meteorite,

there are little crystals of salt.

And the interesting thing about these crystals

is that they contain tiny little droplets

of liquid water, the only samples

we have of water from off the Earth.

Zolensky knows that where there's water,

there is often life.

[Speaker 16] We have main engine start 0.

And liftoff.

And to gather more evidence from an intact space

rock, NASA sent a robotic probe called STARDUST to study

a comet as it hurtled through our solar system

at 22 kilometers per second.

The STARDUST mission

brought back dust grains from the cloud of dust and gas

that surrounds a comet, Wild 2, which

is a comet that comes pretty close to Earth every few years.

And as the comet passed by the spacecraft,

the spacecraft opened up a little dust collector

chip like a tennis racquet.

And thousands of grains of dust smashed into the tennis racket.

We're still just beginning to scratch the surface

on what these samples are.

And for instance, we've found amino acids,

and these are in all of us.

One of the first steps towards life.

And there they are in the comet.

Zolensky has an astonishing theory,

that amino acids crashing into planets could have seeded life,

both on Earth and throughout the galaxy.

There's this idea that once

life arises in one place, it spreads

throughout the universe.

We know that the building blocks of life

are in comets and asteroids in our solar system,

and we see evidence for these same objects

around other star systems.

So probably life is everywhere in space, if it's here.

Microbial life can hitch a ride to our planet

on the back of a meteorite, like a cosmic convertible.

But how will a fully evolved alien species get here?

Because for intelligent ETs to visit Earth,

they'll have to overcome one galactic-sized challenge--

a potential journey lasting 73,000 years.

Alien-hunting scientists

think intelligent aliens could visit Earth

any time now, while 10% of Canadians

say they've already seen a UFO.

But given that the nearest star system to ours

is 40 trillion kilometers away, it makes you wonder,

how will aliens get here?

Les Johnson, a physicist with NASA's Advanced Concepts

office, thinks alien engineers might

approach the challenge of traversing

the galaxy the same way we do.

As a physicist, I have

to make assumptions about the way the universe works.

The way it works in my lab is-- has

to be about the same way it works

in the lab, across the street, across town,

somewhere else on the planet, or somewhere else

on the other side of the galaxy.

And when you start thinking about that

and what it's going to require to travel between the stars,

you have to think big.

You have to think bigger than the Saturn V rocket,

which took people to the moon.

The liquid propellant-fueled Saturn V is

still the most powerful rocket ever built.

It allowed astronauts to travel 384 thousand kilometers

to the moon in just four days.

But for aliens to get to Earth from even Alpha Centauri,

our neighboring star system, makes the Apollo missions

look like a walk in the park.

If we were going to try to go to the stars

and the distances are just huge, right now,

with a chemical rocket like this,

it would take 73,000 years.

Faced with thousands of years in the cockpit,

the aliens need either a lot of magazines to read

or a plan B. That's why Johnson thinks

extraterrestrials might consider using

a more explosive fuel system.

Now, instead of the Saturn V,

imagine a battleship, something really big

with big pressure plates underneath it.

And instead of chemical rockets,

you explode small hydrogen bombs--

--one every few seconds.

And as the bomb explodes, it gives it a kick.

And it starts moving.

And it keeps it going faster and faster.

And if you accelerate for hours instead of the minutes that

a chemical rocket does, you could potentially propel

a spacecraft to another star in a few centuries

instead of 73,000 years.

Exploding multiple devastating h-bombs during

takeoff could make for a fast journey to Earth, but it

might be a one-way trip--

because the aliens would nuke their home

planet in the process.

So Johnson thinks environmentally conscious

aliens could develop something much faster and safer

using alternative energy.

My personal favorite technology.

It's called a solar sail.

What a solar sail does is it reflects

the light to get propulsion.

You can't really feel it here on the ground.

But the sunlight, as the light reflects from you,

are pushing on you.

They exert a force.

If you get out into deep space, this force can be significant.

And it's plentiful.

It's always there.

Well, this prototype solar sail, which is actually one

that we developed for solar sail applications,

is a very thin, lightweight reflector.

Now imagine something like this only scaled up dramatically,

something the size of Texas with the thickness

of a human hair.

If that were to be deployed in space by us or someone else,

they could use that to get a big kick from sunlight

to travel very, very fast.

We don't know how to build something like this the size

of Texas today, but we could probably, within a few years,

build one that's a few kilometers in size

and, within the next 50 to 100 years,

scale that up to the sizes you might need

or anyone might need to travel between the stars.

But even using solar sails,

traveling the four light years to Earth

could take a century or more, which could get kind of dull.

For a really express journey of just a few decades,

aliens need to harness the incredible power

of a mysterious substance called antimatter.

Now, antimatter is really the ultimate fuel

for interstellar travel.

And just to be clear, it's not the stuff of science fiction.

It's very real.

Antimatter consists of subatomic scale particles

that are a mirror image of the ordinary particles that make

up all matter in the universe.

But when matter and antimatter come together,

the explosive result is perfect for space travel.

The reason it's a good fuel

is because when a particle of matter and antimatter

come into contact, they annihilate and produce energy.

Now, to give you an idea of how much energy that is,

take a look at the shuttle behind me.

That external orange tank contains

all the fuel necessary to get the shuttle to orbit.

It would take 50 of those tanks to produce

the same amount of energy as 3 grams of antimatter.

Just a tiny amount of antimatter

could help alien explorers cruise across the galaxy

at up to 107 million kilometers per hour,

reaching Earth in a relatively speedy 42 years.

And unlike the flying saucers of science fiction,

an alien spacecraft could survive

such unimaginable speeds no matter what it looked like.

When we think about spaceships,

we usually think about the shape of a rocket--

tall and thin and very aerodynamic.

And that's really because we live on a planet

and we've got an atmosphere above us.

Well, once you get out of that atmosphere,

you don't have to worry about that anymore.

You don't have drag.

So you can have a spacecraft that has lots of things

sticking out on it or not.

It could be a cube, like a Borg cube.

Basically, once you're in space and in vacuum,

the shape just doesn't matter anymore.

But once aliens have built the perfect

vessel for getting from A to B, they

face a much bigger challenge--

traveling to Earth across the infinite and deadly void

of space without getting lost.

As you may have noticed, there's a lot of space

out there.

Our galaxy alone is 100,000 light years across,

contains 100 billion stars and as many planets,

all in constant motion.

Just one of 200 billion galaxies

believed to exist in the known universe.

So when ET loads up the ship and sets off

on the insanely long ride to Earth,

will aliens get lost in space?

Dr. John Pye is an astrophysicist

who thinks aliens could plot a course

through space in the same way sailors navigate the sea.

Imagine this boat is an alien spacecraft.

The ocean is the galaxy through which it's trying to navigate.

We've been using lighthouses for thousands of years

to navigate the oceans.

We can use the lighthouse to show

how an alien might navigate the galaxy using pulsars.

Pulsars are a rare type of star

that spin around hundreds of times

a second, shooting out characteristic flashes

of radiation at regular intervals, exactly

like a lighthouse.

From our spacecraft

here, we can use the light from the two pulsars

here and here to triangulate our position.

Pye believes an alien navigator could use

the flashing beams of two or more pulsars

as a kind of galactic marker to constantly gauge the position

of their spacecraft.

We need to be able to measure very accurately

the time it takes each pulse of light

to travel from the lighthouse to the boat.

Using the known speed of light, we can

then draw a circle on the map.

We've got a second lighthouse.

We can draw a second circle where the two intersect.

That's where our boat is.

An alien can do the same using pulsars

to triangulate the position of the spacecraft.

In space, an alien would need three pulsars at least

to measure position, because, obviously,

space is three dimensional.

On the sea, it's two dimensional.

So we only need two lighthouses to fix our position.

With pulsars triangulating

their exact location, the extraterrestrial ship can steer

a perfect course for Earth.

But to avoid obstacles along the way,

aliens could try another technology that's been

used by sailors for years.

This boat has radar to avoid

any obstacles in its path.

In the same way, our alien spacecraft

will need radar to avoid any space

debris or other obstacles.

We already have radar on Earth, which can detect

space debris in Earth orbit.

So it's highly likely that any advanced civilization

will have something at least as advanced as our radar today.

But even if the extraterrestrials don't

get lost along the way, the voyage to Earth

will take decades.

So how will aliens survive a space odyssey?

Astronaut Michael Barratt has spent months living

aboard the International Space Station

and understands the challenges long distance

travelers will face.

So every civilization

that wants to travel has to think about mimicking some

of the conditions on their home planet

that would sustain their body.

Remember that their bodies developed under gravity.

So they would have to think about their transit,

in particular bones and muscles, which would

deteriorate in 0 gravity.

For beings with carbon-based bodies

like ours, years spent in weightlessness would be deadly.

But Barratt thinks that, unlike our spacecraft,

an advanced extraterrestrial vessel would be equipped

with artificial gravity.

You can spin the ship, and a lot of people

have the notion of a big spinning wheel

a la Stanley Kubrick.

A spinning craft would create

outward centrifugal force, pulling the alien crew

towards the sides of their ship, just as gravity on Earth

keeps our feet on the ground.

Spinning a ship has its problems.

It can actually be somewhat disorienting.

More elegant solution would be to have a propulsion system

that continually thrusts and gives you a linear G force,

so to speak.

With no friction in space,

rockets don't need to fire continually to keep moving.

But if they did, the resulting linear G force

could create artificial gravity,

the same way accelerating in a car pushes

a driver back into the seat.

Now, if you had the technology,

perhaps you've mastered the ability to manipulate gravity

and that you really could have artificial gravity

field on your ship.

So it really depends on the technology level

that a civilization has attained

before it ventures outward.

Gravity will make the ship comfortable

and help the aliens stay physically fit.

But what about their mental state?

Just imagine being stuffed in a spacecraft on a voyage

lasting decades without losing your mind.

Will aliens go mad in space?

Even with the largest space station

we've ever had, you can see that it's

still fairly confining.

It's not a very big area, especially when you're used

to roaming free on the ground.

And it really causes you to think

about the psychological factors that will come into play

when we do a very long voyage.

For the extraterrestrials, boredom,

solitude, and cabin fever could destroy

morale and even their sanity.

The only thing they can do is stay busy.

So we have to think about what

will occupy the crew.

What will keep them busy.

And I think there are many things.

Keeping the ship's systems in top shape will be part of that.

Keeping the crew members' bodies

in top shape, whatever exercise or countermeasures they

might have to do.

Faced with an endless round of pushups,

ship maintenance, and staring into space,

the in-transit aliens could decide to kill time like

the crew in the sci-fi movie "Alien,"

by taking a very long nap.

Even at light speed,

it's years between stars.

So everything has to be considered.

You have to think about wild technologies out there that

includes cryostasis or putting living beings in a state

of suspended animation to allow them to take

these very long voyages.

But could a race of interstellar aliens

be so advanced that what we think

of as futuristic technology is their idea

of ancient space junk?

And instead, extraterrestrials are masters of space and time,

traveling through the cosmos in ways we think impossible.

In science fiction, alien spacecraft

zip across galaxies faster than the speed of light.

But unfortunately, science fact just has to ruin all the fun,

with the laws of physics saying nothing

can go quicker than light.

But physicist Michio Kaku thinks

the law has a loophole that could allow aliens to travel

through space using the same propulsion system

that powers the Starship Enterprise.

Can aliens travel at warp speed?

Warp drive is science fiction,

but it's based on a kernel of scientific truth.

In Einstein's equations, there are solutions

allowing you to take shortcuts to the fabric

of space and time.

You can compress space in front of you.

So instead of going to a nearby star,

the star comes to you because you compress the distance

between you and the star.

By engaging warp drive,

faster-than-light travel is possible,

meaning aliens could reach Earth

from the nearest solar system to ours in just two weeks.

But how could a spaceship survive

the unimaginable forces of bending the galaxy

without being torn apart?

Physicist Harold White thinks an extraterrestrial spaceship

would protect itself with a force field of normal space.

What does something like this

actually look like?

You've got this central ship that would be surrounded

by some type of equatorial ring that would have

all the negative vacuum energy that's necessary to make

this trick work.

The ship would create a cocoon

of unmanipulated space to sit inside,

while the universe around it is compressed to make

the journey super fast.

So the spacecraft sits

inside of this well-behaved region of space-time.

The proper acceleration is formally 0.

So when you turn the field on, rather than everybody smacking

against the bulkhead and making for a very

sad episode of "Doctor Who," they don't feel anything.

The proper acceleration is 0.

Twisting the universe sounds far fetched.

But White is convinced warp drive is possible,

and he wants to prove it.

So what we're doing now

is we're trying to actually generate a microscopic instance

of this phenomenon in the lab.

It's a very scientific pursuit.

You know, don't get too excited.

It's not anything we're going to bolt to a spacecraft

anytime soon.

But it could be existence proof, as it were.

Don't worry, Harold, we won't get too excited.

And besides, even if an alien spacecraft had warp drive,

they'd need a lot of gas in the tank.

Because to make the trip, it would require

the energy of 300 Earths.

It sounds impossible, at least for a primitive civilization

like ours.

When physicists talk

about civilizations in outer space,

we don't talk about little green men.

We talk about scales of energy.

Now, what are we on this energy scale?

We are a type 0.

We don't even rate on the scale.

A type 1 civilization is planetary.

They harvest all forms of planetary energy.

They can control the weather.

Perhaps they can manipulate earthquakes and volcanoes.

They have cities on the ocean.

Eventually, they exhaust the power of the planet.

And they become type 2, stellar, consuming the energy

of the mother star itself.

They have the ability to deflect meteors and comets

and delay ice ages.

An example might be the Federation of Planets in "Star

Trek," where they have colonized a few

neighboring star systems.

Eventually, they exhaust the power of a star

and become galactic.

They roam the galactic space lanes.

They have colonies and hundreds of billions of planets

within the galaxy, sort of like the Empire in the "Star

Wars" saga.

Traveling in imperial class star cruisers

and bending space and time to their will,

a galactic alien empire eons more advanced than us might

reach Earth any minute now.

But when the big moment arrives and aliens emerge

from their spacecraft to stand face-to-face with humanity,

just how alien will aliens be?

Astrobiologist Lewis Dartnell thinks

the kinds of extraterrestrials likely to come to Earth

would have a physiology similar to ours.

If an alien were to visit us,

to land his or her spacecraft on the lawn of the White House,

and to step down, we'd expect that it

would blink back at us with a pair

of uncannily familiar eyes.

We'd expect an intelligent species

to probably have descended from a predator ancestor,

to be carnivorous.

And you want to have a through flow gut with an entrance

and an exit, which is a very effective way, an efficient way

of extracting nutrients out of the food

that you take into your body when you eat.

The intelligent alien would need

to have its brain, its processing center at the front

of its body, where its sense organs are as well to minimize

its reaction time and for the sense organs to be on the front

so it can sense where it's going

rather than where it's been.

But what happens when

the extraterrestrial visitors point their sense organs at us?

This is the toughest question of all, a question scientific

research alone cannot answer.

Will aliens be friend or foe?

At the SETI Institute, Doug Vakoch

is optimistic about alien intentions.

For him, when otherworldly beings get here,

it could be high-5s all around.

We're not a danger to any civilization that

has warp drive and that can travel,

so it makes no sense to think another civilization

would come to do us harm.

It's much more reasonable to think

that they would make contact in order

to learn about our culture.

Astronomer Geoff Marcy agrees.

He thinks it's common sense to assume

that a more advanced alien civilization means aliens

that are more civilized.

Hopefully, they have found a way

to interact cooperatively among themselves in such a way

that introspectively, they can imagine how to interact with us

in a peaceful way, in a mutually

cooperative way, and maybe even mutually beneficial way.

We might be able to share our libraries,

our music, our poetry, and something

about our philosophies of life.

Like the United Federation of Planets in "Star

Trek," futuristic extraterrestrials

could have matured beyond conquest and greed.

And once they meet humankind here on Earth,

they might want us to join them.

Are they interested in us

because they think we're dangerous

and they don't want to let us run amok

in the galaxy or something so they're

coming here to control us?

I think that's unlikely.

Is it that they feel that we have

something to contribute to some sort of cosmic community?

Any civilization that is aggressive and expansionary

will quite likely have spread already.

We would know all about it.

Or they would have destroyed themselves.

So if there is a galactic club out there,

I think that they would be fundamentally altruistic.

And we have nothing to fear.

Even if the interstellar visitors

are friendly and come to Earth to exchange culture,

can our primitive society cope?

Even a few of the crumbs

off the technological table could

destabilize our civilization.

Think of it.

If all of a sudden we were given disintegrator

rays and given telepathy machines and the ability

to recreate matter in any form or replicator, that

could destabilize modern civilization.

We're not ready to handle this vast technology.

Cyberneticist Kevin Warwick thinks such concerns

could be the least of our worries.

For him, aliens won't be just showing

mankind their technology.

They'll be using it to kill us.

As soon as they spot that we're here,

they may well say, hey, let's go and destroy that planet

and take some of the things off it.

If they have the technology to come to Earth now,

they will have technology and a weapons

system that is way beyond anything we can deal with.

So it may well be the case that we simply

can't defend against it.

Best, really, if we're so insignificant,

keep our heads down rather than argue or fight against them.

If it comes to blows,

it's going to be like Kermit the Frog versus a T-Rex.

It's going to be no contest whatsoever.

Instead of coming in peace, extraterrestrials

may be here as ruthless space invaders.

And what they have planned for us

could be nothing short of an alien apocalypse.

In the movies, alien invasion usually means

we get enslaved, tortured, or just annihilated.

And our own human history has shown

us what happens when the forces of one powerful culture

arrive on the shores of a weaker one.

So will a ruthless extraterrestrial force

come to our world as space conquistadors?

What will aliens do to us?

Astrobiologist Charles Cockell has a theory of what

the alien plan might be.

But a word of warning, do you really want to know?

(ROARING)

[Speaker 21] So why would aliens want to come to Earth?

Well, life.

The incredible diversity of organisms

on this planet, an incredible proliferation of life.

(ROARS)

But one of the things that life does need is energy.

It needs energy to grow and reproduce.

And there are a number of ways in which it can do that.

One way is through photosynthesis.

These leaves are collecting sunlight,

and they're using the energy from the sunlight

to grow and reproduce.

But it's not a very efficient way of gathering energy.

A much better way is to eat the plants.

And an even better way is to eat the animals

that are eating the plants.

At each step, the energy becomes

concentrated as it moves further up the food chain.

So animals that are at the top of a food chain

are generally hunters, the sorts of animals that like

to eat other animals or meat.

(GROWLS)

So if aliens come here, they'll probably be predators.

And like us, they'll eat other animals.

(ROARING)

And if the marauding extraterrestrial invasion force

see life on Earth as one huge combo

platter, then the special would surely be us.

[Speaker 21] So if aliens decided they wanted to eat us,

it'd be very easy for them to harvest us.

First of all, we're very concentrated,

and there's a very large number of us in cities.

And secondly, we're the most intelligent

species on the planet.

So if they decided they wanted this planet

as a habitable world, we would be their first target.

Mankind's only chance

is that the taste of human flesh makes aliens sick.

[Speaker 21] Their biology just may be incompatible with ours.

The proteins and the way in which they're made

may be very different from the stuff of our biology.

So even if they did want to eat us, they might not be able to.

But as the aliens take control of our planet,

being eaten could be the easy way out.

Because Cockell believes that instead of becoming lunch,

humans could be rounded up for a more terrible fate--

dissection.

[Speaker 21] For thousands of years,

we've had a bloodthirsty history of probing

and analyzing the human body to try and understand

how it works.

Maybe aliens will do the same to us.

But it's not all bad news.

Human beings have developed technology

to scan the human body.

That allows us to study some of our biology and medicine

without dissection.

If they really are intelligent aliens out there,

maybe they've developed technologies that would allow

them to scan our bodies and understand

what's inside without having to pull us apart.

Advanced and hostile alien invaders

will have no end of ways to make our lives hell,

but there is some hope because perhaps,

as a US president once predicted, we inferior

humans would fight back.

Whatever we think of President Ronald Reagan,

everybody agrees that he was a shrewd judge

of human character.

And one day, sitting right next to Mikhail Gorbachev,

talking about the fate of the planet Earth itself,

all of a sudden, Ronald Reagan says, if one day the aliens

invade us, you and me, we would join forces against the aliens.

Well, you can imagine what the Gorbachev thought.

He probably thought, oh my god, I'm sitting next to a nutcase.

But in reality, it was a shrewd observation of who we are.

If the aliens do invade, yes, we would band together.

It's part of human nature to set

aside our differences, to come up against a common enemy.

It's part of our genetic makeup that we

realize there's strength in numbers, strength in unity.

There have been hundreds of books written by philosophers

and theologians and strategists about not

how to deal with the weaker enemy,

but how to deal with a stronger enemy.

We would have to learn from the alien invaders.

We'd have to learn their weak points.

We would have to learn how to use

their energy against them, how to use their technology

to defeat them.

That is the art of war.

Be it to fight invaders or befriend

curious visitors, scientists are

preparing Earth for first contact

with extraterrestrial life.

We've seen where aliens might live,

what they could look like, how intelligent they are,

and how they can travel across time and space.

The aliens are coming, and it could be sooner than you think.