All language subtitles for How the Universe Works s08e03 Hunt for Alien Evidence.eng

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Narrator: Aliens...

Little green men.

A thousand eyes or one-eyed.

Narrator:
...Sci-fi movie monsters.

Free-floating with tentacles.

Some unknown
hyper-advanced civilization.

Narrator: Could science fiction
ever become fact?

I think it's really simple
why Hollywood

is fascinated with the concept
of first contact with aliens,

because that would be
probably the greatest

scientific discovery
in all of human history.

Narrator:
Problem is, our universe creates massive barriers

to meeting extraterrestrials.

It's almost as if
the universe is deliberately

stopping us
from making first contact.

Narrator:
We're searching the cosmos.

Will we ever find
intelligent alien life?

Or are we alone?

-- Captions by vitac --
www.vitac.com

captions paid for by
discovery communications

[ explosion ]

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Arecibo observatory,
Puerto Rico.

45 years ago,
it sent a powerful radio message

deep into space,

kickstarting our efforts
to make first contact.

Pacini: The arecibo message was
the first communication

or attempt to communicate
with a possible civilization

out there in the galaxy
or outside of our galaxy.

Narrator: Today, that message
is speeding towards

the m13 galaxy cluster

25,000 light-years away.

It contains information
about our world --

where we are,

even the makeup of our DNA.

Pacini: The purpose of
this message was, of course,

like, trying to say hi,

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

are we alone in the universe?

Narrator:
But what chances are there

that an intelligent alien race
is out there

waiting to receive our message?

Do I think there's other
intelligent life

out there in the universe?

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

We know that life began on earth

pretty much as soon
as our planet solidified.

So why wouldn't that
have happened somewhere else?

Narrator: If life has evolved
on other worlds,

just how many
alien civilizations

are out there that
we could potentially contact?

Astronomer frank Drake
developed an equation

to help answer
this crucial question.

The Drake equation
is a really admirable attempt

to apply
some quantitative reasoning

to the probability,
or the possibility,

that there is life
beyond the earth.

Freese: You multiply
the star formation rate

for stars in our galaxy

times the number of planets
that each star has

times the probability

that you would have life forming
on that planet

times the probability that that
life form becomes intelligent.

And they estimated
that there were about

10,000 intelligent civilizations
within our galaxy.

?

Narrator: Since the Drake
equation was first proposed,

our understanding of the galaxy
has radically transformed.

We have now discovered worlds
outside our solar system --

exoplanets.

Filippenko: Exoplanets are being
discovered all over the place.

There are about 4,000 of them
now known,

and techniques are finding more
every day.

Narrator: Scientists believe
what we've found

is the tip of the iceberg.

So if the cosmos is so good
at making planets,

perhaps it can produce
the conditions

to make life
throughout the universe.

When the Drake equation was
devised all those decades ago,

we didn't know
that exoplanets existed.

And now we think that there are
quite literally more planets

than there are stars
in the universe.

So even if life is really rare,

there are an enormous number
of chances

for it to take hold
in the universe.

And for this reason,
it is very likely that

there is life relatively
abundant in the universe,

including an uncountable number
of advanced alien civilizations.

This isn't science fiction.

It's just basic probability.

Narrator:
Probability suggests

a multitude of alien
civilizations are out there.

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

Thaller: I think there's
every reason to believe

that there are civilizations
out there,

but we have
no evidence of them yet.

Why haven't we found
other civilizations out there?

Narrator:
One answer could be

the sheer vastness
of the cosmos.

Bullock: Look at all these
lights out here

over the cityscape.

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

Now, if there's 10,000
communicating civilizations

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

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

The problem is

there are hundreds of billions
of stars in the galaxy,

which means that maybe
our nearest neighbor

that we can communicate with
is not right there

but way across the city.

Narrator: We live in the suburbs
of the milky way

75,000 light-years from
the furthest edge.

Radio signals travel
at the speed of light.

This speed limit means
that any signal sent

to the opposite side
of the galaxy

would take 75,000 years
to reach its destination.

Bullock: The thing
you have to remember

is the galaxy is gigantic.

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

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

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

Narrator: So the 45-year-old
arecibo radio message

could still be tens of thousands
of years away

from any potential
alien civilization.

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

The message is now
45 light-years from here

'cause it's traveling
the speed of light,

so it's really far
from the target.

Narrator: The vast size of
the universe is a huge roadblock

to making first contact,
and the laws of physics

prevent radio signals
from overcoming it.

You just cannot go faster
than the speed of light.

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

but they're so far away.

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

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

Narrator:
The universe may be large,

but we're putting the most
advanced technology on earth

into action to try
and speed up the search.

There really is a serious,
scientifically valid way

to go looking for
other civilizations.

And the breakthrough
listen project is really

the best thing
we have right now.

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

radio telescopes,
optical telescopes, as well --

are all looking up to the sky
together.

Narrator: Breakthrough listen is
targeting the 1 million stars

and 100 galaxies
closest to earth.

It is the most
comprehensive search

for alien communications
ever undertaken.

If there was an aircraft
giving off a radar signal,

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

the breakthrough listen project
could hear that.

So if there's
something out there

that's actually giving off
a signal,

breakthrough listen
has a chance to find it.

Narrator: Breakthrough has
started by listening in

on the nearest 1,700 stars
to earth.

So far?

Silence.

Thaller:
This is the wonderfully,

beautifully frustrating position
that we find ourselves in.

We haven't heard anything yet.

So we're in this position
where a negative result

doesn't mean
there aren't civilizations,

but we have no proof
that there are.

Narrator: Breakthrough listen is
just beginning its hunt.

There's much more
real estate in the cosmos

for it to search.

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

Plait: If you go through
Drake's equation

and find this number

of 10,000 intelligent
civilizations out there,

there are something like
250 billion stars in the galaxy,

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

That's a lot of cold calling.

Narrator:
The size of our universe

means we could be waiting
a very long time

to pick up
any alien communication.

But even if we pick up a signal,

it may have arrived too late.

Oluseyi:
If we do receive a message,

given that it probably
took years to get here,

that civilization
could be long gone.

Narrator:
So are we simply too late?

Have any aliens out there
already died out?

[ Explosion ]

Narrator:
Earth has orbited the sun

for over 4.5 billion years,

time enough for humankind
to evolve into an intelligent

and technologically advanced
species.

But compared to the age
of the universe,

planet earth is just a kid.

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

and we think it's taken
this long

to create the first
technological civilization --

us.

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

The universe is
13.8 billion years old.

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

We're technologically capable,
we can build rockets,

and we can listen to
radio waves.

But a typical other intelligent
advanced civilization

would be literally
millions of years ahead of us

in technology.

Narrator: So if an alien society
has been around longer than us,

how much more technologically
advanced could they be?

One method of measuring
just how much

is provided by
the kardashev scale.

Tremblay:
The kardashev scale classifies

potential alien civilizations
into three types

based on the amount of energy
that they're able to harness

from their local environment.

A type-one civilization
can harness the energy

of only its home planet.

Type-two could hypothetically
harness the energy

of its own solar system.

And a type-three could harness
the energy

potentially of an entire galaxy.

Narrator: If you're wondering
where we fit on that scale,

prepare for some bad news.

We are somewhere between
zero and a one.

We can't use
all of earth's resources.

So we're at about a 0.7.

Narrator: An advanced species
reaching kardashev level two

or even three

could create
highly advanced structures

that can harness
the power of a star.

Plait: If you get to be
an advanced enough civilization,

eventually if your
energy demands are so huge,

you might build solar panels

that you have enveloped
your star.

This was first thought of
by Freeman Dyson,

and so we call these
Dyson spheres.

Narrator: If such epic
engineering occurs

in other star systems
or even other galaxies,

could we pick up some evidence

and then make first contact?

Plait: The thing about
a Dyson sphere is that

you've completely blocked

all the light
coming out from a star,

except for the infrared

because these panels are
absorbing that sunlight

and warming up.

When you warm up an object,

it gives off what's called
thermal infrared light.

You can scan the skies looking
for that signature

to see if there are
any Dyson spheres out there.

Narrator: 2015 --

NASA's wide field
infrared survey explorer

scanned 100,000 nearby galaxies

to locate advanced
kardashev civilizations

by observing infrared light
leaking away from Dyson spheres.

They detected...

Nothing.

Filippenko:
No such galaxy was found,

so they didn't find
any infrared smoking gun.

Narrator:
Given our universe is so old,

surely other civilizations
should have had time to evolve.

If so,
maybe we've simply missed them.

Plait: It's entirely possible
that civilizations arose,

tried to communicate
with the galaxy around them,

and the problem was they were
asking too early for us.

They're trying to
knock on our door,

but our house wasn't built yet.

Narrator: Earth has been around
for under one-third

of the universe's
13.8-billion-year lifespan,

the human race
just 300,000 years,

a relatively tiny window
of opportunity

to make first contact.

We've been looking at the sky
for tens of years,

something like that.

What is the likelihood
that at that exact moment

someone is gonna be beaming
a signal toward us?

Narrator:
Perhaps the universe prevents

intelligent civilizations
from surviving for very long,

making our chances
for first contact

even more unlikely.

Plait: Maybe there is
something out there

that is filtering us
from seeing them.

We actually call this
the great filter.

Maybe there is something
that says,

"yeah, you're not getting
past here."

Narrator:
Rocky planets like ours are ideal for hosting life,

but they're fragile.

And this fragility means
the universe

could filter out
intelligent life quickly.

?

We've discovered
very violent star explosions

like gamma-ray bursts.

These are powerful enough,
they may sterilize planets

even across an entire galaxy.

Narrator:
And even if intelligent species

survive natural phenomenon,

they may still be filtered out

by hitting
the self-destruct button.

Loeb: As we can tell from
our own experience,

the moment that we started
developing technology,

we also developed the means
for our own destruction

by changing the climate
on our planet,

by developing weapons
of mass destruction.

And so it's quite possible
that civilizations

that are advanced enough
are short-lived.

And if they're short-lived,

that would explain why,
at this point in time,

there are very few of them
that might be around

to communicate with us.

Narrator: Finding the relics
of an extinct alien civilization

could be the ultimate cosmic
warning for the human race.

Stricker: If we were to find
a civilization out there

that may have destroyed
themselves by pollution

or conflict,

it would be almost like
staring into a mirror,

and it would be
a very grim foreshadowing

and maybe a lessons-learned
for us humans here on earth.

Narrator: We can only hope
that some advanced alien species

escaped the universe's
deadly filter.

But even if e.T.S still exist
out there,

the odds are still stacked
against first contact.

?

One other way that we've got
this alien-contact story

a bit wrong is just down to
the laws of physics.

Narrator: Every day,
the physics of the cosmos

makes our chances
of contact worse

because our universe
is expanding,

and it's expanding fast.

[ Explosion ]

?

Narrator:
February 2018 --

astrophysicists
at the university of Oklahoma

find a potential series
of rogue planets

3.8 billion light-years away.

Ranging between the size
of our moon and Jupiter,

these would be
the first alien worlds

ever discovered
outside our galaxy...

...and maybe the first of many.

Our galaxy alone
has trillions of planets.

The observable universe
has trillions of galaxies --

it's estimated about 2 trillion.

So trillions of trillions?

Come on.

Narrator: But finding
exoplanets is no guarantee

of finding alien life.

And when it comes to contacting
extraterrestrials,

our efforts
have met with silence.

Oluseyi: Our search for life
has come up empty.

Do we need
to change our tactics?

Are we doing something wrong?

Carroll: I think it's gonna be
very, very hard

to find
extraterrestrial intelligence

the way that
we're looking for it.

We would have to get
really, really lucky.

But I don't think
we're gonna get lucky.

I think that if we want to know

whether there's life out there
in the cosmos,

we have to go visit it.

Narrator: We've sent
the new horizons probe

billions of miles across
the solar system to pluto.

Perhaps one day we'll be able
to send spacecraft

across the universe

to search for alien life
on distant rogue planets.

?

But if a craft left our galaxy
to visit these new worlds,

its mission would be tough

thanks to the physics
of the cosmos.

From our perspective
here in the milky way,

every galaxy is, on average,
receding away from us.

It looks like nobody likes us

and is trying to get as far away
from us as possible.

Narrator: This is because
our giant universe is expanding.

Freese: When we talk about
the expanding universe,

we don't mean that galaxies
are doing something active

to run away from one another.

Actually, it's the underlying
space that's expanding,

and the galaxies
are embedded in that,

and that's what causes
everything to move apart

from everything else.

Narrator:
The regions of the universe

within 3 million light-years
of us

are expanding
at around 45 miles a second.

That's over 160,000 miles
an hour.

Thaller:
So with our current technology,

do we have any chance
of actually seeing

what these other planets
are like?

Well, think about the fastest
and farthest things

we have right now,
like the voyager spacecraft.

They've been in space
for more than 30 years

going incredibly fast --
38,000 miles an hour.

Narrator:
38,000 miles an hour is fast.

But the closest galaxies to us

are moving away at over
four times that speed.

And the further away a probe
is sent to travel,

the tougher its task.

The thing about the expansion
of the universe

is that the farther away
something is,

the faster it's moving
away from you.

The more distant two objects
are away from each other,

the more space there is
between them,

and the more space
there is between them,

the more space there is
to expand.

Oluseyi: The rate at which
they're moving away

is proportional
to their distance.

If it's twice as far away,
it moves away twice as fast.

It is three times farther away,

and moves away
three times as fast.

Narrator: Scale it up to
the planets we've discovered

3.8 billion light-years away,

and thanks to the expansion
of the universe,

those extra-galactic worlds
are moving away from us

at over 49,000 miles per second.

Imagine that you're a runner,
and you see the finish line.

You're getting
a bit closer to it,

but now, actually,
the track itself is expanding.

And as the track expands
faster and faster,

it's expanding faster
than you can possibly run.

All of a sudden, that
finish line starts receding,

and you're never, ever
gonna reach it.

Narrator: Say one day
we're able to build probes

that travel at the fastest speed
physics allows --

the speed of light.

Even that might not be enough

because sometimes
the universe itself

doesn't play by the rules.

It's not possible for things
to travel through space

faster than the speed of light,
but it is possible for space

to expand faster
than the speed of light.

Tremblay: Everywhere we look,
we see very distant galaxies

that are apparently receding,
or moving away from earth,

at greater than
the speed of light.

Bullock:
There are distant galaxies we can see in the sky that,

even if we were to build the
most advanced spaceship possible

that could even move
at the speed of light,

we could never get there.

97% of the galaxies that we can
see in the distant sky

are actually unreachable to us.

Narrator: So for all
the galaxies out there

and all the planets
that could harbor life,

most of them
are out of our reach.

The physics of the universe
has dealt an immense blow

to first contact.

The true reality of the universe
will always be hidden from us

because of this,
because of this expansion.

Narrator: The further we look
out into the universe,

the more unlikely
first contact becomes.

We might need
an advanced alien race

to come and visit us instead.

Suppose we get that lucky.

Even then, would first contact
actually be feasible?

Oluseyi:
We think aliens are like us.

They're not.

We're assuming that
the life is like us

and that their planetary
environment is like ours.

I don't think
that's gonna be the case

for most of the life
in the universe.

Narrator:
So, could extraterrestrials

even survive first contact
with us and our planet?

[ Explosion ]

Narrator: July 2019 --

the test satellite
discovered a new alien world

31 light-years from us

named gj 357 d.

At over six times the mass
of our home planet,

it's thought to be
a super earth.

And from our observations,

super earths appear to be
prime real estate.

What we see is that
the most common type

of terrestrial planet
is what we call a super earth.

So that means
it's a terrestrial planet,

but much more massive.

Narrator: More massive can mean
more gravity,

creating a planetary environment
completely unlike our own

and life completely unlike ours.

Oluseyi: If they're on
the surface of a super earth,

it could be that gravity
is gonna be way stronger.

So these aliens
aren't gonna be very tall,

but they are gonna be
very strong.

Narrator: Super earths are just
one of the many avenues

the universe creates.

There are other exoplanets
orbiting red stars

10 times smaller than our sun

and others making binary systems

comprising two stars
instead of one.

We see planets of all shapes
and sizes around stars

of all shapes and sizes,
of all sorts of configurations.

The potential for life
is much more rich and varied

than we ever thought before.

Retro rockets
five and six fired.

Narrator:
Images of science fiction

have fueled numerous fantasies
of first contact,

but our knowledge
of the universe suggests

reality could be
far, far stranger.

If anything,
Hollywood has kind of

constrained our imagination

in terms of presenting
so many aliens

that basically look like,
you know,

humans wearing a rubber suit
or something.

Lower landing legs.

We have to, have to,
let go of this obsession

that they're gonna be
anything like us.

So if we're looking for
two-legged dudes, forget it.

?

Narrator: Say an intelligent
alien species lives

in our stellar neighborhood

and wants to make
first contact with us.

If that alien evolved
on a super earth

or orbited a red star
instead of a yellow one,

it's wildly different biology

may prevent it
from ever setting foot,

or tentacle, on planet earth.

Stricker: When you look at life
here on earth,

it's almost as if it was
custom-made

for this temperature,
for these elements,

for this environment.

An exoplanet with conditions
to support life

could still be
completely different

than life here on earth.

Plait: What are things gonna be
like on an alien world

which has a little bit
more potassium

or is warmer than average
on earth

or has a thicker atmosphere?

Each one of these
small variations

can mean a completely different
ecosystem.

Narrator:
So could an alien organism

really adapt to our ecosystem
when it lands on earth?

Maybe we haven't made
first contact

because they can't
actually visit us.

Dartnell: They could step
through the airlock

of their spaceship
and onto the earth

and just find something toxic
with our environment,

some some reason
they're not compatible

with the surface of the earth.

It's almost as if
the universe is out there

deliberately trying to stop us
meeting any aliens.

Narrator: Biology creates
another obstacle

for making first contact,

but as planetary scientist
jani radebough finds,

even life on earth
can get pretty weird,

taking extreme measures to adapt

to a potentially hostile
environment.

Radebough:
This is the great salt lake.

It is the remains
of what used to be

a much larger lake in the past.

And when it evaporated away,
it left behind all of the salt.

Narrator: The great salt lake
is nearly 10 times saltier

than earth's oceans.

The extreme salt content

should make it an inhospitable
place for life.

Despite this, there are
organisms thriving in the water.

Radebough: As we look at life
in this vast lake

and find that there are billions
of microbes living here

in this unexpected environment,
then we start to realize,

well, life forms in ways
that we just don't expect,

in places we don't expect.

Narrator: Microbial life
known as extremophiles

have developed an ingenious way
to survive in the lake.

Well, they actually use
these solar-powered pumps

to pull the salt
out of their cells

so that they can operate
more normally.

But in order to do that,
they have to live

very close to the surface,

which means they get
a huge amount of U.V. radiation.

So all this pink color
that you see behind me

is actually the pink
of the organisms,

and it's sort of like
a built-in sunscreen

that helps protect them against
the U.V. radiation.

Narrator: Extremophiles are
rewriting our expectations

of where life can survive
on earth.

Could alien biology be much
more resilient than we think?

These extremophiles
should be a little reminder

that we haven't been
thinking big enough.

Narrator:
Maybe e.T. Could readily adapt to our environment,

or perhaps they've got
other ideas,

using technology to overcome
any biological barriers.

Maybe the first aliens we meet
will be robots.

They can build
much more powerful life

if they don't limit themselves
to meat bags.

Narrator: Advanced aliens
could have left

their biological brains
and bodies behind,

traveling instead as
mobile artificial intelligence.

Tegmark: We tend to think of
intelligence and consciousness

as something mysterious
that can only exist

inside of biological organisms
like us

and somehow therefore
can't be copied.

But what's given us the whole
a.I. Revolution, right --

the idea that, no,

intelligence and probably
consciousness, too,

is just information processing,

and it's just the information
processing that really matters.

Perhaps an alien would be
able to download

its consciousness
into some sort of computer

and travel as
a disembodied consciousness.

In this state,
you'd be essentially immortal.

Narrator: So it's possible an
advanced species could find ways

to face the challenges
of first contact.

But if an alien civilization
is out there

and more advanced than us,

could there be
an even bigger issue at play?

Maybe the reason
that intelligent aliens

haven't ever come to the earth
to visit us

is maybe we're just
not that interesting.

Narrator: So maybe the biggest
barrier for first contact

is the fact that aliens
don't actually want to meet us.

[ Explosion ]

?

Narrator: In the movies,
first contact usually leads

to an alien invasion.

Cities get zapped.

[ Explosion ]

Humanity faces annihilation.

[ People screaming ]

Maybe a visit from e.T.

Isn't such a good thing,
after all.

Imagine if we if we got
an intergalactic e-mail,

so from, you know,
superioraliencivilization. Org,

saying, "hey, we're gonna
show up in 30 years."

Would we just be like,
"oh, all right,

let's get back to
watching our reality TV shows

and worry about that
when they get here"?

No, we would seriously
freak out.

Narrator:
People might freak out,

but the truth is we've been
sign-posting our location

into the cosmos for decades.

Dartnell: The earth has been
a detectably technological world

for about 100 years.

We've been broadcasting signals,

and yet, that apparently hasn't
attracted anyone's attention.

It's pretty noteworthy

that none of them
has shown any interest,

when they could have
turned earth into a parking lot

if they wanted, right?

Narrator: Perhaps no one
has redeveloped planet earth

because an advanced civilization

simply doesn't want to
make first contact.

Frankly, if they're
that intelligent,

they're not gonna be
very interested in us.

So maybe that's why they haven't
bothered to make contact.

Filippenko: And if the alien
is that advanced,

we're probably not
very interesting to it.

It's a little bit like,
you know,

wandering around outside
and seeing ants on the sidewalk.

Narrator: Alien invasion makes
for great science fiction,

but what do we actually
have on earth

that's worth
all that alien effort?

Dartnell:
How realistic really are

these depictions from Hollywood?

One common trope is the aliens
coming to devour the human race.

But the science doesn't really
support this being possible.

Would an alien even be able
to digest the human body?

Narrator: When eating,
enzymes in our digestive system

break down molecules
in our food.

The food we can eat, and these
enzymes are very specific

to the molecules
they can attack and break down.

The same rules would apply
to a hungry alien.

Dartnell:
To be able to digest us

and for us to be nutritious
for them,

we'd have to have a very, very
similar biochemistry

to what exists
on the alien's home world,

what their bodies
have adapted to.

Narrator:
So it seems highly unlikely

that aliens would come
looking for food.

But how about a drink?

In order for life as we know it
to exist,

one needs liquid water.

Narrator: If aliens live
on a barren desert planet,

a water world like ours
could be highly attractive.

While we call ourselves
the blue planet,

our oceans are not unique.

The universe offers
far greater water resources.

Sutter: In our solar system,
we're finding that

most of the liquid water exists
in moons around the gas giants.

Narrator: We believe
Jupiter's moon europa

has a layer of water ice
around 15 miles thick

floating on an ocean
up to 100 miles deep.

This single moon may have
twice as much water

as all earth's oceans combined.

Europa is the water world
of our solar system

and not the earth.

So if you were an alien
looking for water,

you wouldn't bother going to
a big planet like the earth

to suck it up through
some kind of giant straw.

You'd go to
the outer solar system.

You might harvest icy moons.

Narrator:
Instead of working against

the powerful gravitational pull
of earth,

an alien race could draw water
from europa,

where gravity is almost
10 times weaker.

So what other resources
have we got to offer?

Maybe aliens come to strip mine
the earth's crust

for metals -- iron or titanium
or platinum.

Aliens might use these metals

for exactly the same things
that we do --

for building spaceships,
for building their technology.

Narrator:
Such materials could be useful

for any alien civilization
short on mineral resources.

Problem is,
a lot of our planet's metals

are buried deep
in the earth's interior.

When the earth formed,
the great deal of its iron

sunk down into the core
of our planet

and took a lot of metals
with it.

So they're actually quite hard
to mine on the earth.

Narrator: An alien race would be
better off prospecting

for more accessible minerals
situated in the asteroid belt.

In the asteroid belt, there's
an asteroid called psyche,

which is made up
of pure iron nickel,

just like the core of the earth.

Narrator: Psyche provides
a near-150-mile

exposed strip of iron nickel,

yet another reason e.T.
Wouldn't need to bother with us.

For my money,
none of those reasons

would draw aliens to earth.

All these things can be found
far more easily elsewhere.

Narrator: The possibility
of first contact

is beginning to sound
increasingly remote.

The universe throws up
massive barriers

stopping us from communicating
with an intelligent alien race,

a race that might very well
have absolutely no interest

in contacting us,

unless, of course,
they already have.

Is it possible that
there have been alien signals

that we've already detected but
we didn't realize what they are?

Narrator:
Scientists have discovered

a powerful cosmic signal
that they cannot explain.

Could this finally be
first contact?

[ Explosion ]

Narrator: July 2018 --

the chime telescope
in British Columbia

detected a short flash
of radio energy

quicker than a blinking eye.

It's called a fast radio burst.

These are intensely powerful,
very, very short

lived radio bursts
that can be 1,000 times brighter

than the sun
at radio wavelengths,

that arrive and disappear
in an instant.

Narrator: Most fast radio bursts
are one-offs,

blinking into existence,
then disappearing forever.

But not this one.

A few days later, scientists
caught the flash again.

The amount of energy
that it takes to produce

a burst like this,

for us to detect it
here on earth

from billions of light-years,
is immense.

And we've run across
things like this before --

exploding stars,
gamma-ray bursts.

These are all
very strange objects,

but that does not explain these

because some of these
fast radio bursts repeat.

So whatever it is that can
generate this kind of energy,

it can do it more than once.

Narrator: Light comes in
many different wavelengths.

Radio waves are the longest,
making them good

for long-distance communication.

We've used radio waves
for over 100 years,

from wireless radio to TV,

from cellphone calls
to communications

with space probes.

Could alien civilizations
be using radio waves,

but on a much larger scale?

What if we already intercepted
alien communications,

but we just don't know it?

Narrator:
Our radio and television signals

only use a very narrow band
of the radio spectrum.

Fast radio bursts are different,

and that's a problem.

Here's the thing
about fast radio bursts --

they are emitting
a broad range of wavelengths,

so it's not the best way
to communicate.

If these are aliens,
they're not very smart aliens.

Narrator: It turns out
that broad-range wavelengths

are easy to distort.

There is a very thin gas
out there between the stars,

and when you emit radio waves,

the radio waves interact
with this gas.

And the way they interact

depends on the wavelength
you're talking about.

If you use a broad range
of wavelengths

to send a signal
across interstellar space,

by the time
somebody receives it,

it can be a little distorted
and weird.

Narrator: If aliens are
sending out radio bursts,

the signal would get so degraded
that by the time it reaches us,

we wouldn't be able
to decipher it.

As a calling card,
not incredibly useful.

Narrator: Whether these
mysterious bursts really are

aliens trying to say hello
or just a natural phenomenon,

this is not first contact,

at least not yet.

I want to be careful here,
right?

I'm not a naysayer.
I'm not gonna pooh-pooh aliens.

But, you know, let's go through
the other things first

because the universe is filled
with weird stuff,

and let's see what that is.

And if we eliminate all those,
and all that's left is aliens,

yeah, let's talk.

Narrator: If extraterrestrial
species are out there,

our universe makes it
extremely difficult

to contact them.

But in spite
of all the obstacles,

maybe there's still hope.

We once thought that
there could be 10,000

intelligent civilizations
in the milky way alone.

Now we know that our cosmos
is filled with planets

just waiting to be found.

Our technology is evolving.

Searches are expanding.

The truth about our mission
to make first contact is this --

we are only
just getting started.

I'd love for tomorrow morning
some sort of interstellar tweet

to be beamed at the earth,

and we would then realize

that we are not alone
in this cosmos.

Pacini:
I'm all ready to celebrate.

Here we have already
a champagne on ice

[laughs]
To pop when they find it.

Thaller: Scientists really do
hope we find evidence

of extraterrestrial life
someday.

We have observatories and
satellites that look at the sky.

All day, all night, every day.

The discovery of alien life
would simultaneously be,

in a way, unsurprising

and yet the greatest discovery
in all of human history.

Even if life
is really, really rare,

the universe
is really, really big,

and so there could be countless
alien civilizations out there.

But the actual discovery
or confirmation of that --

I can think of no greater
scientific discovery.

It would quite literally change
our entire civilization.

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