All language subtitles for How.the.Universe.Works.S07E08.Hunt.for.Alien.Life.1080p.WEB.x264-CAFFEiNE

�

narrator: Earth --
a planet defined by life.

Stricker: The amazing thing
about life here on earth

is no matter where you look,
you'll find it.

Narrator: But is earth unique?

Thaller:
The big question of our day is,

does life exist somewhere else
beside the earth?

Are we that special,
or is life everywhere?

Narrator:
The ingredients for life

are spread throughout
the universe.

But then we started looking
into space and saying,

"wait a second.
That chemistry is everywhere."

Narrator:
Is life inevitable?

I think that there have to be
planets out there

that are capable
of hosting life.

Narrator: What does life need
to get started,

and once started,
can life spread?

It's possible that life
started on Mars

and was transferred to earth
inside of a meteorite.

Narrator:
Life has conquered our planet,

but can life conquer
the universe?

�

-- captions by vitac --
www.vitac.com

captions paid for by
discovery communications

�

the universe
is a very big place.

There are trillions of galaxies,

each one home
to millions of stars

and an unimaginable number
of planets.

So where is everybody?

One of the most basic
philosophical questions is,

are we alone?

Are we the only ones
looking out and thinking,

"what is all this?"

Is it all just for us, or do
we get to share it with anyone?

I mean, that's about
as fundamental a question

as you get.

Narrator: What are the odds of
life existing somewhere else?

We just don't have a good
insight

to how probable life
is anywhere in the universe.

Life could possibly
be forming everywhere.

We don't quite know.

There's a lot about life
that we don't understand.

All we know is that
it happened at least once.

But beyond this
one little planet,

we don't know whether or not
it happened anywhere else.

�

narrator: The universe is
an unfriendly place.

Planets with lava oceans
circle too close to their stars.

Pulsars Blaze with
deadly gamma rays and x-rays.

Black holes consume
everything in their path.

Temperatures plummet close
to absolute zero.

�

it may seem impossible for life

to survive in such
hostile environments,

but here on earth,
life exists against the odds

in some very strange places.

Life has actually permeated
every part of our planet.

There are places
where you're like,

"how did you even get there?"

Narrator: At first glance,
a beautiful lake

might seem like
a good place for life,

but California's salton sea
is no paradise.

The toxic salt waters
are killer...

...surrounded by scorched desert

and volcanic geothermal fields.

It's a deadly environment.

One of the last places on earth
you'd expect to find life

would be in boiling mud vents.

You can start to hear
these vents because there's gas,

and there's water and mud slurry
that's coming out, right here.

So these are
active mud volcanoes.

It's really hot.

It's, like...
164 degrees fahrenheit.

Narrator: But life is resilient,
finding a home even here,

inside volcanic vents
in the California desert.

We're in the middle
of a really hot desert,

and as the mud comes up,
it's coming up hot,

and it's kind of acid,

and yet there can be microbes
in environments like this,

happily thriving away.

This is an environment that is
actually conducive to life,

even though we think
it might not be.

Narrator: Almost every inch
of the earth's surface

is teeming
with microscopic life-forms.

The thing about life on earth

is that it exists in so many
different environments

under such harsh,
extreme conditions.

It's like it hangs on,
no matter what you throw at it.

Very dry, high pressure,
very hot,

even in high radiation
environments,

which would kill
a human within seconds.

Narrator: Life even survives

being bombed with asteroids
and meteorites.

We have a wonderful
indirect example

of just how tenacious life is,
and that's the fact

that it survived
the late heavy bombardment.

Narrator:
The late heavy bombardment

was a violent assault
on young earth,

where life had just gotten
a foothold.

Experts think
around 4 billion years ago,

asteroids comets
and space debris

rained down
on the inner solar system.

This rocky barrage
would've melted parts

of the earth's crust
and boiled away oceans.

It was a violent time
called the hadean period.

The hadean named, after Hades,
named after the underworld,

after hell.

It was a brutally unpleasant
place to be.

It was spewing its own innards
out into the surface

in this intense cycle
of hot volcanism.

Narrator: If life on earth

overcame these
hellish conditions,

then perhaps life
can survive anywhere.

Straugh: I think
if it can happen on earth,

I think it can happen
on other planets.

I think life finds a way,

and I think we need
to go looking for it.

Narrator: The question is,
what exactly are we looking for?

Plait: What is life?

You know, that seems
like a simple question,

but it's not
that easy to answer.

Life is incredibly hard
to define, right?

It's sort of like, you know it
when you see it,

but how do you
write down the rules?

Stricker: Every time we think
we have a grasp,

there's this new form
that comes about

and completely questions
that entire definition.

There's a joke in astrobiology
that if you ask

200 scientists
for a definition of life,

you'll get
200 different answers.

Narrator: Life can be
as intricate as us humans

or as simple as single-celled
organisms, like bacteria,

but there are some things
all life-forms do.

Plait:In broad terms,
life consumes things.

It breathes. It eats.
It excretes.

It grows. It reproduces.
It's complex.

Narrator: Life has transformed
the earth in all sorts of ways,

but life is
still just an accident.

Life, as I see it,
is just a chemical reaction,

but it's the most important
and special chemical reaction

in the universe.

Narrator: If life is just
a product of chemistry,

then what are the odds of it

starting anywhere
in the universe?

One thing we know
about chemistry

is that
given the right conditions,

the same chemical reaction
will reliably occur.

Narrator:
It's like a game of chance.

For life to win, the conditions
need to be just right,

but to figure out the odds,
we need to understand

what those conditions are
and how common they are.

Oluseyi: So it comes down
to a numbers game.

It's about statistics and
probabilities and likelihoods.

Narrator:
It's like having to roll a 6

for each condition for life.

But how many 6s would you need?

How many precise conditions
does life require to get going?

You might have 100 dice,
roll them all, get all 6s.

Only then do you get life.

Narrator:
You could need hundreds

or hundreds of thousands
of dice.

We just don't know.

We honestly have no clue

how common or rare life is
in the universe.

Plait: We don't know how life
originated here on earth,

where we kind of understand
the conditions.

There are a lot of different
ways life could've started.

Is life rare? Is life common?
We don't where it lands.

Narrator:
Putting odds on life existing

is a waste of time
until we understand it better,

and maybe our answers
don't lie here on earth.

One way to crack this problem

is to go looking for life
elsewhere.

If we can find
other examples of life,

we can immediately begin
to put a quantitative answer

to how probable it is
for life to happen anywhere.

Narrator: And the best place
to look for life

might be in our own backyard...

...Mars.

If life can start here,

then maybe life
could conquer the universe.

�

narrator: For life to conquer
the universe,

first, it has to get going.

When we look at life on earth,

it's possible that it all
has a common ancestor.

Life started at one spot,
branched out, and became

all the different kinds
of life that we see.

Narrator:
But how did it start?

The first question to answer is,
what is life made of?

Top of the list are the most
basic building blocks --

chemical elements.

Here's what I know about
the universe --

the laws of physics
appear to be same everywhere.

The chemical composition,

the elements are the same
everywhere.

And the cosmos creates
these elements,

not from the big bang
but from stars.

Narrator: Over the course
of a star's life,

it creates elements.

And when a star dies,

these elements are blasted out
into space in a supernova,

spreading the ingredients
for life out into the cosmos.

We, the earth, our solar system,

all the ingredients
that make us,

us were forged in nuclear fires.

So the death of stars
leads to the birth of life.

Narrator: Those key ingredients
include oxygen,

nitrogen, sulfur,
and phosphorus,

but the element most central
to life as we know it is carbon.

All life as we know it on earth
is based on carbon.

Carbon forms the structure,

the architecture
of our living molecules.

Narrator: Carbon is
an incredibly versatile

building material.

It can bond with other elements
to form long-chain molecules,

each with different properties.

As an element, it seems to be
capable of producing

a vast and complex chemistry,

and that complex chemistry
is what we find in life.

Narrator:
We call this organic chemistry.

�

but getting from
basic organic molecules

to complex life-forms
is a big leap.

We don't really have
the slightest idea,

to be honest, about how life
on earth got started.

Scharf: A really big question
is, how do you go from a mix

of relatively simple organic
molecules to a living system?

Narrator: We know it all starts
with basic elements created

in massive quantities...

...by the death of stars.

But how do you start connecting
those lego bricks together

to build that first cell?

The short answer is,
"we don't know,"

but we have some ideas
of potential steps.

Narrator:
Chains of organic molecules

become more and more complex.

Amino acids form proteins.

Fatty acids form phospholipids,
which makes cell membranes.

Nucleic acids form DNA,

the molecule that stores
genetic information.

Eventually,
a simple cell emerges.

So all of the bits you need
to plug together

to build a cell from scratch

seems to exist in outer space.

We found organic compounds
everywhere.

They're all over the place --

planets, comets, gas clouds.

The very basic
ingredients of life

available elsewhere
in our solar system,

so there could be life
everywhere.

�

narrator: In 2018,

NASA announces it's found
organic molecules

on another planet,

a planet we've always suspected
of harboring alien life --

...Mars.

So whenever NASA has a
press conference, and they say,

"hey, I have some results
to report on about Mars,"

everyone goes nuts.

Dartnell:
The Internet goes mad.

Maybe we've got photograph
evidence of the green men

in a ufo.

Lanza:
This time, it's the martians.

They're going to tell us
they found a martian.

The world listens
'cause everyone wants to know.

Everyone asks the question,

"have we found evidence
of life?"

Narrator: For 6 years,

the Mars curiosity
rover has been exploring

a region called Gale crater,

hunting for signs of
ancient life.

A bit like
fossil-hunting on earth.

Gale crater is not unlike
places on earth

that can preserve fossils,
so a really good example of this

would be the petrified forest
in Arizona.

This looks like a piece of wood,
but in fact, it is stone.

It is all stone,
but it used to be a tree.

This fossil lived
200 million years ago.

Narrator:
This patch of desert in Arizona

once looked
completely different.

Lanza: This landscape looks
very dry right now,

but 200 million years ago,

it was wet swampland
with trees and flowing water.

Narrator:
Like the petrified forest,

Mars has also changed over time.

Gale crater was once a lake bed
filled with fresh water.

And it was just so exciting
because we knew then

that we had landed
right on top of an environment

that once had tons
of flowing water

and could very well have
preserved organic materials,

even though it looks very barren
and desolate to our eyes.

Narrator: In 2018,

curiosity drills into
this ancient martian lake

and discovers organic molecules.

Finding organics on Mars
is so exciting

just because, I mean, wow.

That is -- those are
the building blocks of life,

not just the elements,
but actual molecules.

There was a wave of excitement

after the announcement
of organics

found on Mars
and complex organics.

It's not totally indicative
that life is there,

but it's a really good
telltale sign

that there may be
possibly life-forms on Mars.

Narrator: The results aren't
proof of martians,

but the ancient lake bed
is evidence that the red planet

once had something else
crucial for life --

liquid water.

�

it's one thing if you have
all these ingredients

lying around for life.

You could have, you know,
carbon over here and hydrogen

over here,
maybe methane or whatever.

You have to mix them together,

so you need something for them
to be in, a medium of some sort.

Narrator: Life needs a liquid

to mix essential chemicals
together.

We're used to thinking of earth

as the only water world
in our solar system,

but new evidence says
otherwise...

...as extraterrestrial visitors

carrying liquid water
from outer space reveal.

�

narrator: It's no coincidence

our blue planet is
a water world.

There are more than
366 million trillion gallons

of water on earth.

It even makes up
60% of our bodies.

I think life on earth
could be easily described

as water chemistry.

That is the essential feature
of life on earth.

Narrator:
Some is locked up in ice caps

or as vapor in the air,

but 96% of liquid water
is in our oceans.

Well, earth is really special.

There's no other place like it
that we've found.

It's a pretty substantial planet
with liquid water

covering 70% of the surface.

All life on the earth requires
bodies of water

in order to survive.

No water, no life.

Narrator: Water is what chemists
call a solvent,

and it's the best solvent
we know of.

It can dissolve more substances
than any other liquid,

allowing molecules
to mix and interact.

Wherever water goes,
it transports

valuable chemicals, minerals,
and nutrients.

Oluseyi:
If there was no liquid,

things would just sit around
separately.

You need this constant
interaction,

and you need
a different chemical mix,

and water does all of that.

And so a lot of our searches
for lifelike planets,

or earthlike planets,
outside our solar system

are based on this sort of
primary assumption

that we need liquid water.

Narrator: We've long thought
earth has liquid water

because of its unique position
in the solar system.

It's right in this zone that
we call the habitable zone

where the sunlight
can support liquid water

on the surface of the planet.

�

narrator: But we have now
discovered that liquid water

might exist in places
we never expected.

In 1998, a meteorite crash-lands
in Texas.

Today, scientists
at Arizona state university

are still studying its secrets.

We had no idea
that it would contain

this really,
really spectacular finding.

Narrator: It contains
a mysterious purple mineral.

The exotic color comes from
exposure to cosmic radiation,

but the compound itself
is very ordinary.

It's actually sodium chloride,

which is essentially
the same mineral as table salt,

but what's really cool
is that it actually contains

little globules of liquid water,

and that liquid water
was trapped in these crystals

4 1/2 billion years ago.

Narrator: In 2018, scientists
reexamined the crystals

and discovered the liquid water
wasn't traveling alone.

We've now actually found
organic compounds in association

with this liquid water
in these salt crystals,

and that's something
that's really new

and really spectacular.

Thaller:
We actually found amino acids,

the building blocks of all
of our proteins, even our DNA,

and we found liquid water,

the very building blocks
of life, inside a meteorite.

Narrator: So could life exist

somewhere else
in our solar system?

�

a NASA mission to saturn
turned up some shocking results.

The cassini space probe flew
beneath saturn's moon enceladus.

Dartnell:
Enceladus, no one cared about.

It was a tiny, little snowball
of a world.

Narrator: But enceladus
surprised everyone.

Geysers of liquid water,
dozens of them,

blast out of trenches
along the moon's surface,

coming from
a vast subsurface ocean.

Oceans on earth
are full of life.

Could the same be true
of enceladus?

McKay:
I'm a big fan of enceladus.

I think it's by far and away
the best place to go

to search for evidence of life.

Narrator: In 2018,

researchers analyzing
the cassini data

discovered that the plumes
of enceladus

contain
complex organic molecules.

Just simple molecules,
we find those, like methane,

but the cassini results
are showing that there are

these more complex, larger
organic molecules as well.

Narrator: This is the first ever
detection of complex organics

on an extraterrestrial
water world.

All of a sudden,
here's water jetting out,

carrying organic material, all
the ingredients needed for life.

It was, like, too good
to be true.

Narrator: But enceladus isn't
the only small world

with a subsurface ocean.

Other moons and dwarf planets
have liquid water, too.

We think the most important
thing for life to form

is the presence of liquid water,

and our solar system
seems to be full of it.

Sutter:
The discovery of liquid water

in the outer solar system

changes the rules of how life
might originate in the universe.

�

narrator: Across the universe,

alien life could be hiding
underneath the surface.

Internal water oceans are
far more common

than surface water oceans,

so if there is a lot of life
out there in the universe,

chances are it's in an internal
ocean under miles of ice.

Narrator:
Who knows what might be lurking

inside icy exoworlds?

There may be jellyfish
and octopuses all over the place

in exomoons and exoplanets
under ice

that have civilizations
that we just don't know about.

Narrator:
Finding liquid water oceans

could open up a world
of possibilities.

If you're not excited about

intelligent extraterrestrial
octopus civilians,

I don't know what to say.

Narrator: The chances of finding
life in our solar system

just got a heck of a lot better.

Building blocks
and liquid water are common,

but you need more than
just these two conditions

for life to take hold.

Life needs a spark.

Life appears to need
some form of energy

to actually get
the molecules interacting.

One thing that may have helped
kick-start life on earth

is ultraviolet radiation
from the sun.

Narrator: Ultraviolet light
is emitted by all stars.

There are billions of stars
in our galaxy.

Can life get started
around any star,

or is our sun unique?

Narrator: Earth is
a solar-powered planet.

At the bottom of the food chain,
plants use photosynthesis

to convert sunlight
into chemical energy --

food for the rest of us.

Dartnell: I like eating
both grass, essentially wheat,

and I also fancy
the odd hamburger from a cow

that has eaten that grass.

This whole ecosystem
is powered by sunshine.

Narrator: But recent studies
have shed new light

on how life developed
under our sun,

specifically the role of
ultraviolet light.

U.v.a. Radiation is useful
for breaking molecules up

and triggering reactions.

Maybe that played a role
in the origin of life.

It breaks down
simple organic molecules,

and then they can
rebuild themselves

into things
that are more complex.

You do that over and over again,
eventually,

you somehow get life.

�

narrator: Scientists think
life on earth

started around
4 billion years ago...

�

...a time
when earth's atmosphere

gave little protection.

U.V. radiation levels
were 100 times higher.

Was U.V. essential

for the development
of life's code, DNA?

We know that life on earth
stores information in DNA

and then uses that information
to build proteins,

so you have the blueprints
and the bricks.

The blueprints are the DNA,
and the bricks are the protein.

Dartnell: But we think that
the first life on earth,

we used a chemical
which is much simpler.

Narrator:
This simpler chemical was rna,

DNA's single-stranded
forefather.

Rna is almost like
a two-for-one offer.

It does both of
the fundamental things

you need for a cell
in the same compound.

So it was simultaneously
the bricks and the blueprint.

Narrator: Unlike other
molecules, rna is more resistant

to the high U.V. environment
of early earth,

allowing it to flourish.

Rna eventually evolved
into DNA,

and life started.

Oluseyi:
To have life on the planet,

one important consideration

is a certain amount of light
that's going to be needed

and a certain type of light
that's going to be needed.

�

narrator: So if all stars emit
some U.V. radiation,

can life start around any star?

When we think about
looking for places

that are conducive for life,

we want to find a planet

that might have enough
U.V. radiation,

so the star is, you know,
bright enough or close enough

that's providing enough energy
to the surface for life,

but we also don't want to have
too much U.V. radiation.

Narrator: It seems you need just
the right amount of U.V.

�

the most common stars in
the galaxy are red dwarf stars.

If red dwarf stars can harbor
life on planets around them,

there's an awful lot
of real estate like that

in our galaxy.

Narrator: Red dwarf stars
could be good for life's chance

of conquering the universe
in a number of ways.

One, they represent over
three-quarters

of all stars in the universe.

Two, they live for over
a thousand times longer

than sunlike stars,

and, three, they seem to have
rocky planets around them

much more often
than sunlike stars do.

Narrator:
Those are the pros,

but red dwarf stars
also have cons.

For instance, they might not be
bright enough for life to begin.

Some of the red dwarf stars
that we know emit

less ultraviolet light
than the sun.

They don't give off
much U.V. light at all.

Maybe on a planet around them,

there isn't enough energy
to get life started.

Narrator: Red dwarf stars are
also much more temperamental.

They can go from being
gentle and quiet

to having violent outbursts...

...stellar flares.

These types of stars
have incredibly strong flares.

That means they're shooting off

a bunch of energetic particles
and radiation

and light that's baking
the surface of those planets.

Radebaugh: If the star is just

bombarding the surface
with U.V.,

then it will destroy all of
those things necessary for life.

It will actually destroy
the life itself.

�

narrator:
These stellar flares

could strip away
a planet's atmosphere,

sterilizing the surface.

�

more research is needed,
but for now,

the odds of life thriving around
dwarf stars are a toss-up.

�

so far,
the only thing we know

is that there is one kind
of star

that's definitely
right for life --

our sun.

We know of life in one place in
the universe, and that's here.

That's earth.

Narrator: Only 4% of stars in
the universe are like our sun.

So if life can only get started
around these rare,

medium-sized stars,

the chances
are not looking good.

�

but life may have an Ace
up its sleeve.

What if life can start on
just one planet and then spread?

What if life travels
across the cosmos

looking for planets to conquer?

�

narrator: Earth is
our only example of life

emerging anywhere
in the universe.

But what if life on earth
didn't start on earth at all?

There's one idea that life
on earth

actually didn't get going here
but was delivered from space.

Narrator: Scientists
call this theory panspermia.

Scharf: The idea of panspermia
essentially talks

about the transferral of life
throughout the cosmos.

Narrator: We know asteroids
and comets

carry organic molecules.

But could they carry
life itself?

What if life starts
on one planet?

Can it actually get itself
to a nearby planet?

Is it possible that meteorites

could actually transport
living beings?

Narrator: For life to travel
around the cosmos,

first, it needs to take flight.

An asteroids is on a collision
course with an inhabited planet.

So what happens if there's
a huge cataclysmic

collision on a planet?

Material is blasted off
into space.

�

narrator:
The impact might kill life

on the surface of that planet,

but it's possible
some bacteria might escape,

hitching a ride on chunks
of the planet's surface.

A meteorite being ejected
from a planet

after an asteroids impact --

I mean, that's not going
to be an easy ride.

But it turns out
it's not as bad as you think.

Some bacteria are
very, very hard to kill.

Some we don't even know
how to kill.

Even the impact that actually
threw that rock into space --

the bacteria, no problem.

If those chunks of rock expelled
during asteroids collisions

could actually hold onto
viable organisms,

then it really could change
the way

in which we think about life
spreading in the universe.

Narrator: If the microbes
can survive takeoff,

then they can start
their journey to a new home.

The odds of life
conquering the universe

seem to be getting better.

The important question now is,
how long could that life,

those bacteria,
those microorganisms

inside that rock,
survive the space environment?

Narrator: Exposure to
U.V. radiation could be fatal,

killing any life on the surface
of an asteroid.

But experts think
that microbial passengers

could still survive
by hiding underground.

It doesn't take much to shield
a microorganism from U.V.

Just a little bit of rock,
and you have enough protection

to just hold on throughout
a journey to the next body,

to your next home.

Narrator: Eventually, they could
arrive at an uninhabited world

that's ready and waiting
for life,

but they're in for
a bumpy landing.

Would the rock burn up coming
through a planet's atmosphere?

It's in for a hot ride
but only for a few seconds,

and only the outer layers
of that rock will blow off,

and then it just falls and hits
the ground not that fast,

a couple hundred miles an hour.

If a human were in there,
that would be bad.

But for bacteria, no big deal.

Narrator:
The panspermia theory says

life could start on
just one planet,

then spread to another planet,
and possibly another.

If we found alien life-forms,
would they look familiar?

One of the biggest questions
about finding other life

in the solar system is,
how similar will it be to us?

If it's just like us,
it begs the question,

did we have a common Genesis?

Did we originally
come from another planet?

Narrator: One radical idea

is that life on earth
came from Mars.

Imagine Mars
3 1/4, 4 billion years ago.

It was more earthlike then
than earth was at that point.

The earth was still quite warm.

Mars actually had cooled
off faster,

had a thick atmosphere, water.

Life could've arisen there.

Narrator: Mars has been
hit repeatedly by meteors,

sending chunks of the planet
flying off into space,

and some of those chunks
have landed here, on earth.

So this is
a really unusual meteorite.

It was found near
the city of Los Angeles,

and we actually know

that it actually came from
the planet Mars,

and we know that because it has
gases trapped inside it

that have the exact same
composition

as the martian atmosphere.

There's been a lot of transit

between meteor strikes
hitting Mars and then earth.

There's a little bit of Mars
on earth.

There's a little bit
of earth on Mars.

It's possible that life
started on Mars

and was transferred to earth
inside of a meteorite.

When you think about it,
maybe we're the immigrants.

We are the martians.

Life on earth started on Mars
and got transferred here.

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narrator:
Panspermia could allow life

to spread from planet to planet,

conquering our solar system,

but what about
even greater distances?

In 2017, the cigar-shaped
space rock 'oumuamua

appeared in our solar system.

It came from interstellar space,

and experts think it could be
carrying organic matter.

One of the fascinating
things about 'oumuamua

is it has sort of
a reddened surface.

Now that could actually
partially be

from the presence
of organic molecules.

Narrator: Could life survive

interstellar
or even intergalactic travel?

Whether or not this is an easy
way to transfer life around

in the universe,
it's still an open question.

The possibility of transferring
life from star system

to star system
seems a little bit remote.

Narrator:
The immense distances

and dangers
of interstellar travel

would be hard to survive.

Some experts think there is
one way for life

to conquer the universe,

but it won't be life
as we know it.

Narrator: The universe is
unimaginably large.

Many experts believe
there is life out there.

We just have to go find it.

Oluseyi: One of the things
I love about being a human

is the fact that
I'm born with this curiosity.

This curiosity drives us to
explore -- explore earth,

explore our solar system
and beyond into the galaxy,

look for other life-forms.

Narrator:
But with current technology,

it would take thousands of years
just to reach the nearest star.

It's unlikely humans
will ever leave our galaxy.

If life one day does spread
from earth into the cosmos,

it's probably not just going to
be a bunch of meat bags,

like us, but other forms of life
that are more suited

for interstellar
and intergalactic travel.

Narrator: Our fragile bodies are
not suited to the distances

and dangers
of interstellar travel.

Machine life may be more robust
for traveling between planets

and between stars
than biological life.

There are a lot of scientists
that think

when we encounter aliens,
we won't be encountering them.

We'll be encountering
their machines

because we can build machines
that can last a million years,

go from one star to the next.

It's much easier
than transporting us,

fragile gloppy bags of meat.
And so if we go out into space,

we're more likely to find robots
than we are biological life.

Narrator: For humanity to
discover alien life,

humanity itself may have
to evolve

from biological life
to artificial life.

Oluseyi: What's really ironic
here is that

while we're figuring out
the origin of life on earth,

we humans could be inventing
a form of life on our own,

and that is what we call
artificial intelligence.

The development of a.I.,
self-replicating machines even,

may very well be
just the next key transition

in our evolutionary history.

Narrator:
Could a superintelligent
self-replicating machine

conquer the universe?

Maybe this a.I. Can fashion
its own machines,

create factories to create
resources to replicate itself,

create ships
that will allow it travel

from one place
in the universe to another.

Narrator: But would a.I.
Represent a new form of life?

Thaller:
I think the answer is yes.

I think it actually goes on
from there.

I think artificial intelligence
might be

the next necessary stage
in evolution.

We made the computers.
They are our children.

I think of life as a process
that can retain its complexity

and reproduce,
so bacteria are life.

Humans are life,
and some future creation

of advanced
artificial intelligence

that can do those things
should also count as life.

Narrator:
Life could take many forms,

and in such a vast universe,

it could be that life
is inevitable.

With all those stars
and all those planets,

I think, without a doubt,
there is a good chance

that life has developed
elsewhere in our universe.

Must life happen
in our universe?

Is it an inevitable consequence
of processes in operation?

Maybe, maybe not.

Narrator: Until we find it,
we won't know for sure

whether life can conquer
the universe.

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