Original subtitles

Ever worry about picking up a bug?

What if we have all caught something...

Something unidentifiable

and from unknown origins?

Not from each other.

From the heavens.

Drops of rain could be bringing us visitors

from another planet ... Aliens invading our bloodlines

or maybe even infecting our technology.

They could be hidden in packets of digital data,

in a form we don't even recognize as life.

Alien intelligence may be tracking our every move.

We haven't found any extraterrestrials yet,

but maybe we're looking in the wrong places.

Are aliens inside us?

Space, time, life itself.

The secrets of the cosmos lie through the wormhole.

Captions by vitac www.Vitac.Com

captions paid for by discovery communications

the size of the universe is really hard to comprehend.

Hundreds of billions of stars

in our galaxy and billions of galaxies beyond.

It seems impossible to imagine that the only place life

exists is here on earth.

Are we the only intelligent life-form in the cosmos?

If not, then where are the others?

In the past, we've always looked up to the heavens.

But to find alien life,

maybe we only need to look down, within our world

and inside our bodies.

This man has alien intruders inside of him right now.

Cedric Feschotte is a geneticist at the university of Utah.

He's well aware that he,

like every living being on the planet,

hosts foreign viruses and bacteria.

But Cedric is focused on more insidious intruders.

See them in genome sequences.

Many copies,

but we really don't understand how they got there.

Freeman: These alien entities are called transposons.

They're pieces of DNA which sneak in from the outside

and insert themselves into our genes.

So they copy and paste to new places in the genome.

This replication is independent from the replication

of the whole set.

And they do this much more often than the set actually replicate.

Freeman: They're not just invading human cells.

Virtually every living thing on earth contains transposons.

Feschotte: In fact, they are the single largest components

of the genome of many plants, many animals as well.

We like to call them space invaders.

Freeman: Our DNA comes to us in a direct line from our ancestors,

generation after generation.

And that genetic inheritance also includes the transposons

that snuck into our ancestors' DNA.

Every once in a while,

a new transposon mysteriously finds its way in,

like a skateboard that suddenly appears and becomes part

of the way Cedric's ancestor moved through the world.

These alien intruders can continue multiplying

and passing down to successive generations

until a single transposon

exists in the entire population of a species.

And transposons are so good at replicating inside of us

that half of our DNA is now alien.

When the transposon jump into the chromosome,

it's like a mutation.

Something new was introduced there.

So most of the transposons in your genome

don't really affect you,

just like these bunny ears today won't really affect my skating.

Freeman: Other transposons can be helpful.

In fact, one of these intruders

became the foundation for our immune system.

It's like a helmet suddenly appearing to protect

Cedric's head.

This transposon arrived millions of years ago

and gave us the ability to create antibodies,

a crucial line of defense against pathogens.

Feschotte: And without this transposon,

we just probably would not be here today.

Freeman: The transposons can also cause problems.

Sometimes, transposons can be harmful, too,

like this blindfold on my head.

Cant find my skateboard now.

There's over 100 different genetic disease

tied to transposition events.

This can really be so bad

that it could lead to extinction of a species,

just like a virus could spread and turn into a pandemic.

Freeman: Cedric thinks it's possible

that transposons break into our cells

by attaching themselves to viruses.

Feschotte: They could piggyback onto a virus.

And then this virus can infect a new cell.

And then the transposon

can infiltrate that new individual or that new species.

Freeman: As the virus goes about its business,

disrupting our DNA, the transposon sneaks in, too,

and never leaves.

But the biggest mystery of all is where these bits

of self-replicating DNA come from in the first place.

They are so abundant,

yet we know very little about them.

In fact, it's really like the dark matter of the genome.

Could the space invaders taking up so much room

in our DNA have actually come from outer space?

We still haven't found any other signs

of life in our solar system.

That means alien pieces of DNA

would have to come from a distant star system.

But how could anything biological

survive that kind of trip?

University of Michigan astrophysicist

Fred Adams believes he has an answer.

According to a theory, known as panspermia,

life spreads around the universe

when a comet or asteroid hits a planet.

The impact sends debris shooting all the way up into space

and eventually onto the surface of another planet.

We see meteorites from Mars on a somewhat regular basis.

So we do know that there's transfer from Mars to earth.

Freeman: However, martian rocks don't contain life.

And our other neighboring planets

don't appear to have any, either.

So Fred started wondering

if life could've made a much longer journey to earth

from outside our own solar system.

In order to be transferred, the elements of life,

basically bacterial kind of organisms,

have to be encased in rock.

Freeman: The rock provides protection from extreme cold,

heat, and damaging radiation.

The shield needs to be a little bigger than this ball.

In order for solar systems to share rocks,

two things have to happen.

The first is that the solar systems have to eject rocks

from their immediate vicinity.

And the second thing is that another solar system

has to capture them.

Freeman: A large enough impact from an asteroid or a comet

could easily produce enough energy

to shoot debris out of a solar system.

But whether it can hit a planet orbiting another sun

is much less certain.

Space is relentlessly empty,

which makes rock transfer between solar systems

very difficult.

Freeman: There's an average of four to five light-years

between solar systems in our galaxy.

Even if you could launch a space rock that far,

what are the chances of hitting another planet

up to 30 trillion Miles away?

Okay, let's consider a simple analogy.

Each of these lacrosse players will represent a solar system,

and the ball will represent a life-bearing rock.

As the players throw the ball back and forth to each other,

it's like a rock being transferred

from one solar system to another.

Let's see what happens.

Freeman: Suppose the length of a lacrosse field represents a light-year.

Even if a player could throw a ball four or five fields away,

consider how unlikely it would be for that player

to toss a ball blindly

and have it land in the pocket of a teammate.

And distance isn't the only factor.

Solar systems in our galaxy

are also flying around each other

120 times faster than the speed of sound.

So now the teammate has to be running full speed.

Even when an alien rock's trajectory is on target,

it's almost always moving too fast for gravity

in the new solar system to catch it.

Imagine the difficulty

in catching a speeding lacrosse ball from hundreds of yards

away while running and with a broken net.

Not surprisingly,

when Fred ran the numbers calculating the distance

between earth and other solar systems,

factoring in the movements of stars and planets,

it seemed impossible that an alien rock

could ever find earth from so far away.

But then Fred realized something he'd missed,

something that suddenly made it a lot more likely that aliens

could have landed here.

Four and a half billion years ago,

things were a lot different.

Alien suns

and their surrounding planets crowded earth's night sky.

Neighboring solar systems

were roughly 10 times closer than they are today.

Now the lacrosse players can be dozens of yards from each other

instead of hundreds.

In the early part

of the evolution of the solar system,

the solar system was living in a dense cluster.

Freeman: And solar systems back then were moving around each other

40 times more slowly than today.

On the lacrosse field,

that makes completing a pass a lot simpler.

Adams: If the players are close together and moving slowly,

it's easy for them to pass the ball from one person

to the other.

Freeman: If Fred is right, billions of years ago,

our home planet

would've been in position to snare ancient alien organisms.

Could they have seeded life on earth?

This biologist thinks they did

and that they're still raining down on us today.

He says he has proof that organisms from outer space

are in our atmosphere right now.

The seeds of life on earth

may have arrived billions of years ago

from a distant alien world.

But if life got here by hiding on a meteorite

fallen from the sky...

Could it still be raining down on us right now?

Milton Wainwright is a microbiologist

at the university of sheffield in england.

He believes he's found evidence

that extraterrestrial life falls like rain from the heavens.

Wainwright: So the basic idea of panspermia is that life came from space.

There was no life on earth.

That life was delivered by asteroids and comets.

Now, Neo-panspermia, Neo meaning new, uh,

suggests that life is continuing to come from space

at this very minute.

Freeman: In 2013, Milton and his team collected samples

from the stratosphere some 16 Miles up.

That's three times higher than commercial jetliners fly.

The lower atmosphere is full of life,

but Milton thinks the stratosphere is, too.

His controversial claim

is that it contains life forms from outer space.

The suggestion by the critics is this material is going up

and not coming down from space.

It's just earth material.

Now, there's a number of reasons why we think that's wrong.

Freeman: Milton counters that his samples

came from far too high to have been blown upward by the wind.

Wainwright: Physics tells us that the particles

we have are too big to reach the stratosphere.

Now, that's just physics.

And you can't argue with physics.

You can't argue with Newton's laws.

Freeman: But Milton is aware that the only way he's going

to convince the skeptics is to find more aliens.

If microorganisms or any life is coming in from space,

we have to go out and catch it.

[ Air hissing ]

Freeman: And that's exactly what Milton is doing.

He and his team are conducting a new series

of high-altitude missions.

Yep. Bon voyage, stratosphere sampler.

Whoa!

The team waits for about 90 minutes while the balloon

climbs 80,000 feet.

Once there, a drawer mounted inside the payload opens.

So this is what happens in the stratosphere.

The drawer opens.

The samples are collected on electron microscope stubs.

We can take those directly from here, under sterile conditions,

into the electron microscope.

Freeman: Sixteen miles up,

the air pressure is so low that the balloon

continues to expand until it ruptures

and tumbles back to earth with this precious cargo.

Wainwright: This is a fishing trip.

We're sending these balloons up.

We don't know what we're catching.

So, on some trips, we'll catch nothing.

On some trips, we'll catch something.

And maybe we'll go for five launches with nothing,

and then the sixth launch,

we get an amazing array of organisms.

Freeman: He's hoping his latest launch will yield something like this.

These are photos of samples Milton

and his team collected on their first mission in 2013.

And Milton believes they contain evidence

of extraterrestrial life.

Wainwright: This is the first amazing organism we found.

If we go to a textbook,

for algae, bacteria, we don't see something like this.

Freeman: Milton's supposed aliens

are only about 30 microns across,

roughly twice the thickness of a human hair.

Wainwright: At first, I was very upset about this structure

because I thought it was a ... a pollen grain.

But when we do the chemical analysis,

we found it was primarily titanium.

And you can see that there's material coming out of the ball.

And when we analyze this, it turns out to be biological.

This is carbon and oxygen.

It's biological.

Freeman: No life form yet discovered has a titanium shell.

This might be the first.

And, more crucial to Milton's case,

no earthly organism would be moving fast enough

to leave an impact crater on the collector.

Wainwright: We see that there's an impact crater here.

So this ball was coming in from space, impacted the sampler,

and caused a crater.

The impact event means it's coming from outside.

It is not lazily drifting up from the earth.

It's coming at a great speed.

Milton thinks comets might be the source.

Wainwright: The temperature is right.

The amount of water is right.

The amount of carbon and organic material is right.

Freeman: Debris from their frozen tails could be

littering our atmosphere with alien organisms.

Hoping to replicate the success of his first launch,

Milton has another half dozen planned.

The big fear I have is that we got these amazing images

and we never repeat it.

Now, in science, of course, a one-off is nothing.

We need to get a repetition of something.

Freeman: Even if Milton does find more alien microbes,

he cautions that they might look more familiar than we expect.

If they've been arriving for eons,

we may already share a lot in common with their biology.

Everyone expects something from space to be special.

There's not necessarily anything special about them.

If they're coming in, they've been coming in

from millions of years.

They're here.

We are part of space.

These organisms are part of our biology.

Freeman: If alien microbes are capable of reaching earth

from across the galaxy,

then could intelligent extraterrestrials

also come here?

We've seen no sign of them.

Or are we searching for the wrong kind of signal?

If intelligent aliens were to send us a message

from a distant planet, would we hear it?

200 years ago,

no one would have picked up a morse code

on a telegraph wire,

much less a voice on the cellular network.

Perhaps we just don't have the technology yet

to answer a call from an alien.

University of Hawaii physicist John learned

thinks alien messages may be within our reach.

We cannot guess what some extraterrestrial intelligence

may be having in mind

for why they would communicate or how they would communicate.

So the best we can do is just look to see what is there.

Freeman: If extraterrestrials are out there

and can send messages throughout the galaxy,

John says they'll be using communications technology

very different from our own.

When we send messages over long distances on earth,

we rely on pulses of light or radio waves.

However, using light for interstellar communication

would be spotty at best.

Learned: There's a lot of dust and gas out there in the universe,

and that scatters light.

So it wouldn't do to try to have light signaling

from even our own galactic center.

Freeman: And messages sent with radio waves

would have a lot of interference to fight through.

There's hiss coming from all over the universe,

from all the stars and galaxies.

So there's background noise that you have to get around.

By tuning around with this radio,

there's all kind of noise that comes and goes.

You have to find a frequency where the extraterrestrials

would be choosing to communicate.

The problem in tuning in is there's no schedule

and no list of ... of stations.

So we don't know quite where to look.

Freeman: John thinks there's a better technology

to send messages across the galaxy.

Aliens might be using a tiny particle called a neutrino

they're subatomic particles produced by nuclear reactions,

like those in our sun,

and violent events, like exploding stars

and gamma ray bursts.

The most intriguing property of neutrinos

is that they are so small they can pass through matter

as if it wasn't there.

The kind of dense matter that stops all light

and most radio waves can't stop neutrinos.

They pass right through things.

Coming through the walls,

coming up out of the ground here.

We're in a breeze of about a million neutrinos

through your thumbnail per second.

Freeman: In fact, if there was such a thing

a sunblock for neutrinos,

a neutrino protection factor

of 1 trillion or more wouldn't suffice.

Even though just a thin layer of this on my hand

is good enough for photons, uh, it would have to be vastly,

vastly thicker for stopping neutrinos.

And, in fact, this umbrella,

which stops the photons from the sun just fine,

wouldn't do the job.

It would have to be a lead umbrella a light-year thick

to do the job.

Freeman: John thinks an alien civilization

might decide to create a beam of neutrinos

and pulse them,

manufacturing a message in a kind of cosmic morse code.

But because neutrinos are so ghostly,

they're extremely tough to detect or measure.

The largest detector on earth,

called icecube, lies buried under nearly three kilometers

of ice at the South pole.

86 strands of sensors

wait for one of the neutrinos streaming through earth

to bump into one

of the electrons in the surrounding ice.

Icecube picks up only a handful of neutrino collisions

each year.

Neutrinos vary in energy.

The highest-energy neutrinos are the most rare.

There's a great controversy going on right now about,

what are the source of these?

What ... what are the mechanisms

that produce these high energies?

Freeman: Because they're so rare,

John believes they could be great communication tools

for aliens.

If one of these high-energy neutrinos

makes contact with an electron inside icecube,

we'll know it.

It'll make this little explosion,

which is so characteristic that we could identify it uniquely.

If you saw one,

it would certainly get your attention.

Freeman: Physicists call this characteristic burst

the glashow resonance.

The way a high-energy neutrino interacts with an electron

is similar to what happens when music meets a wine glass.

[ Wine glass resonates ]

Hey, guys.

Hey.

All matter has a natural frequency.

When energy from an outside source

matches that natural frequency,

the object will vibrate much more than usual.

That's known as resonance.

So what we've got here is a ...

A glass, hopefully, a nice, resonant glass.

And we've got a speaker,

which is attached to an amplifier.

And we're driving acoustic energy, sound,

very high-intensity sound toward this.

And we'll try to hit the resonance in the glass

and break the glass.

Freeman: You can think of each note

as a different energy level neutrino and the wine glass

as the electron.

First, John tries various notes on an organ.

[ Organ plays ]

Now the singer.

[ Vocalizing ]

Finally, the guitar player.

[ Solo plays ]

Learned: It's a matter of, uh,

getting the right frequency,

getting enough energy right on the right frequency.

Man, that's gone.

Freeman: The glashow resonance is the explosion that results

when just the right type of high-energy neutrino arrives.

John thinks a string

of these rare explosions wouldn't be a coincidence

but rather a sign of an extra terrestrial intelligence.

Learned: And if we see those neutrinos coming from the same direction,

then we certainly

know that that is not a natural phenomenal.

Would be the greatest discovery ever.

I can't think of anything

that would be a more amazing discovery

than to find the first signs of extraterrestrial life.

It would change our world.

Freeman: As exciting as it would be to find an alien message,

the simple act of reading it could threaten our existence.

Alien communication could carry a lot more than a greeting.

The moment of first contact with an alien civilization

will be the most important event in human history.

But if we already missed it?

What if an alien message has arrived and we didn't notice?

Maybe it's here right now,

hiding inside our technology.

Andrew siemion

specializes in the search for extraterrestrial intelligence

at u.C. Berkeley's SETI research center.

He and his colleagues

are looking for unusual signals in outer space,

hoping to find one that might come from an alien civilization.

I think that our first encounter with very advanced life

probably will not come in a spaceship landing

in golden gate park.

It's quite likely that it will come via a signal

that we just happen to eavesdrop on.

Freeman: But it may be that aliens are already listening

to our radio signals.

If there were very advanced life nearby to earth,

they've monitored our radio signals

that have left this planet.

And so they almost certainly know quite a lot about us.

Since the 1960s, communications satellites

have been relaying information from one computer to another.

And that information has been leaking out into space.

If aliens understand how our computer networks

operate and know that we're actively listening for them,

Andrew believes they could take advantage of the situation.

They could deliver a digital virus

and know that we'd scoop it right up.

We gather millions of radio signals from space

each year in our search for intelligent communication.

Those signals go straight to our computers

so researchers can analyze them.

Hunting for evidence of advanced technology,

these radio signals,

is kind of like hunting for easter eggs.

We're looking for that one small nugget

that stands out from the landscape.

The signals that we look for are very, very weak,

so we have to sift through all of the noise,

noise produced from other astrophysical sources,

quasars and pulsars.

Freeman: Once SETI researchers gather potential alien signals,

they take a closer look.

But analyzing the signal on one of our computers

wouldn't be enough to unleash an alien virus.

Researchers would have to run the code.

We have to take that data,

and we have to run it on a computer.

And that's sort of akin to opening one of these eggs.

Freeman: Advanced alien hackers would probably notice,

and they'd likely know there's another way into our networks,

a way that wouldn't be dependent on a decision by one of us

to run their code.

Hundreds of radio antennas on earth are specifically

designed to exchange computer code with each other

and immediately run those programs.

Siemion: A signal that was sent by another species

to one of those antennas

could be received and executed in the same way

that it executes code that it receives from ...

From human transmissions.

Freeman: In fact, an alien code

could already be here, operating undetected in our networks.

The whole idea of a virus or a trojan horse is to ...

Is to run some code

on a computer or on a computer network

that no one knows anything about.

It ... it runs itself, uh, surreptitiously under the radar.

Freeman: Human hackers have already shown it's possible

to hide computer viruses for long periods.

The stuxnet virus,

developed in secret by the U.S. and Israel,

lurked in the network of an iranian nuclear facility

for over a year, slowly damaging hundreds of iranian centrifuges.

The virus sent signals to the plant's control room,

indicating everything was normal,

until the centrifuges finally broke in 2010.

A program from an advanced civilization could go unnoticed

for much longer and be far more destructive.

We might be able to recognize it because it would be a ...

A piece of computer code

that we had never seen before that was devised by a ...

A completely different species.

Freeman: Could aliens programs already be inside our technology,

preparing an attack on our networks?

Or is there perhaps an even more unnerving possibility?

The aliens themselves may be in our networks

as digital life-forms.

If so, this man believes he knows how to find them.

Could alien visitors have already arrived on earth?

Perhaps they have,

and we just don't recognize them.

Maybe they aren't made of flesh and blood or metal

or anything we can touch.

What if aliens are digital life forms?

Chris adami of Michigan state university

is an evolutionary biologist and a computer scientist.

He studies the border between life as we know it

and life as it might be.

What we really want to do is have a definition

that does not depend on the very specifics

of the form of life that we encounter here on earth.

What is life?

The dictionary will say it involves metabolism, growth,

reaction to stimuli, and reproduction.

So plants and animals are obviously alive.

But what about a robot?

We could imagine a robot like that to be alive if,

in fact, it could not only build another robot just like it

but also, in fact,

makes copies of the programming and inserts

that into the baby robot that it makes.

If it is doing that,

it will be able to create a population of robots.

But this thing is actually not alive.

It was programmed by the people who built this plant.

It does not actually have the capacity to self-perpetuate.

Freeman: Because a robot's operating instructions

come from an outside entity,

it can't adapt or evolve on its own.

But that doesn't mean that something artificial

can't be alive.

Chris believes alien digital life forms

could do everything we do ... Consume resources,

reproduce, evolve, all inside a computer.

He knows because he and his colleagues

created organisms just like that.

Their digital organisms

live in virtual environment called avida.

Each dot is an avidian.

Different colors represent different species.

Adami: They're more like computer viruses

that can replicate and make copies of themselves

except these are special in the sense that,

when they make copies of themselves,

they might make flawed copies,

in a sense of mutations.

So these copies can actually evolve in a darwinian manner,

just like it would be doing in a petri dish.

But in this case, they are digital organisms.

Freeman: The survival of any species

depends on having just the right rate of mutations.

Zero mutations would mean avidians could only copy

themselves and never evolve.

With too many mutations, the new version

would no longer be a program, just random bits of data.

Chris programmed his virtual organisms

to mutate every generation.

In other words, avidians evolve.

I'm standing in the middle of a grid that is going to help

us understand how avida works.

And I'm gonna be playing the role of digital organisms.

And I'm gonna do it like this.

The different color shirts

that I wear represent different digital organisms.

Freeman: The grid represents a limited amount

of computer processing power over which the avidians compete.

Avida is designed to reward complex calculations,

which we can represent with movements.

Make a simple fairly useless movement,

like raising one arm,

and the program doesn't replicate.

Make a complex, useful movement,

like going from sitting to standing,

and the program can copy itself.

The more copies of the same program there are,

the more computing power they can grab.

Just like real life, avidians pick up new movements

and new combinations through trial and error.

Going from sitting to jumping is a highly complex movement.

That represents a complex calculation.

You start with simple calculation,

maybe an addition, maybe a small subtraction.

If you could do multiplication, you can an actually

do better than than just poor adders and subtractors.

Then somebody doing square roots or logarithms

or integrals would dominate

over those that are just the pure multipliers.

Freeman: The red avidians look like they're going to take over.

But then yellow stands up and executes a new,

highly complex jumping Jack move.

Suddenly, yellow starts

replicating faster than the other colors.

Adami: Very quickly, you'll see a yellow type taking over,

which then is followed by a red type

and then an orange type.

And you'll see many different colors emerge,

take over, and then go extinct again

in a long, long period of evolution.

Freeman: Studying avidians makes Chris feel confident that,

if digital aliens are hiding inside our networks,

he'll be able to find them.

He's found a telltale signature of life,

whether it's biological or digital.

Like all life forms,

avidians are born with a finite set of instructions.

If Chris removes the rewards that cause avidians to evolve,

then each instruction

will be used at roughly the same frequency.

But living avidians find certain instructions

more valuable than others and use them far more often.

That is Chris' signature of life.

Biological life has an equivalent signature.

The pattern of amino acids used in our bodies

is very different from the random pattern

in nonliving matter.

But could aliens

be even closer to us than inside our technology?

This physicist believes an endless variety of aliens

may be only a fraction of an inch

away from every part of our world

but could remain forever out of reach.

We assume that, if alien life is already on earth,

it had to have traveled here from somewhere else.

Whether primitive microbes or advanced beings,

the assumption is they had to cover vast distances.

But what if aliens have always been right next to us,

living on a different plane of reality?

Theoretical physicist Alejandro Jenkins

is constantly amazed by the diversity of life

in his native Costa Rica.

But he's noticed that the seemingly endless variety

of plants, animals,

and insects tend to cluster in separate domains.

Think of the difference between the canopy ecosystem

that you have on the tree tops.

And then there would be entirely different ecosystem,

um, right here, on ... On the ... on the beach floor.

Maybe you can also think of another ecosystem

on the surface of the ocean.

Freeman: Alejandro believes our universe may be like one

of these ecosystems,

surrounded by an incredible variety of alien life,

not in nearby star systems,

but right under our noses.

He thinks the aliens could be within fractions

of an inch of you,

me, this spider, everything.

If that's true, then where exactly are they?

They would be displaced in another additional dimension

that is not one of the three dimensions that ...

That we see in everyday life.

Freeman: Many physicists are convinced there are dimensions

of space and time that we cannot detect.

Could aliens be living right among us yet still out of reach?

Jenkins: It's hard to think in terms of more than three dimensions.

So let's suppose that instead of living in three dimensions,

we lived in two.

So, uh, the surface of a ... of a playing card

is two dimensional.

But if you have a ... An additional third dimension,

you can stack as many cards as you want.

So I can have this card,

but right ... right below it,

I can have a different one and so forth.

So perhaps our world, our universe,

is just one particular slice

through that higher dimensional space.

You would have to move only a very tiny distance

in this other additional direction in order to get there.

Freeman: Alejandro believes the life

that may exist in these extra-dimensional universes

could be in a form that's hard for us to recognize.

We would expect on ... on ... On theoretical grounds

that a lot of these other universes would have

different matter contents and different kinds of ...

Of forces between ...

Between the particle, upon the matter.

Perhaps in some cases, even though the forces

are different, uh,

you would still be able to get a form of life.

Freeman: In this wild section of Costa Rica,

most creatures in one ecosystem

are unaware the living things in an adjacent ecosystem exist.

Jenkins: What we have here is a line

of ants that's carrying leaves back to its nest.

And I imagine that, as they move down the trunk,

they're only aware of the fact

that they can move up or down to their left or to their right.

And we know that there's another dimension

in which the ant cannot move.

It's not like they're butterfly.

Cannot fly away in that direction.

So maybe they're not aware of the fact that there's something

else out there.

Freeman: We might be like the ants,

unable to see other universes around us.

Could we ever find another dimension or even travel there?

Alejandro thinks probably not.

It would seem like we would never be able

to see those other universes

because light would not be able to cross that divide.

The old saying about the search for aliens

was, "the truth is out there."

Well, there's a good chance that they're also in here.

When we discover aliens, will we

also discover a completely new concept of life, consciousness,

and intelligence?

I certainly hope so.

The only thing we really know for sure

is that our civilization is just a tiny speck

in the greater scheme of things.

And we'll never stop wondering

who else might share this universe with us.

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