All language subtitles for The.UnXplained.Mysteries.of.the.Universe.S01E05.1080p.WEB.h264-EDITH_track3_[eng]

WILLIAM SHATNER:
Massive asteroids

on a collision course
with Earth,

deadly bursts
of cosmic radiation

with the power to wipe out life
as we know it,

and microscopic alien viruses
that can invade our planet.

When we look up at the stars
at night,

we see the peaceful,
shining tapestry of the galaxy,

yet just out of sight

are cosmic dangers
beyond our control,

each one able to end human
civilization as we know it.

Can we prepare
for the inevitable calamity

coming our way?

Or are we doomed to oblivion?

Well, that is
what we'll try and find out.

♪ ♪

SHATNER:
As this small industrial city
in the Ural Mountains

begins its day,

a 66-foot-long asteroid
suddenly streaks across the sky.

Within seconds of its arrival,

the giant rock abruptly explodes
in the sky...

(car alarms wailing)

...18 and a half miles
above the region...

...generating
a superheated shock wave

that rips through the city.

DAVID J. THOLEN:
When it entered
the Earth's atmosphere,

this asteroid
superheated the air

so rapidly that it created
effectively a thunderclap,

or a sonic shock wave.

But this was so powerful
that it shattered windows

throughout the city
of Chelyabinsk.

1,600 people were injured
by flying glass.

MICHAEL DENNIN:
With Chelyabinsk,

we were pretty lucky
'cause it was in the atmosphere

that it really detonated.

But imagine
if it had hit the surface,

this would've really caused
huge amounts of damage.

SHATNER:
Fortunately,
no lives were lost

as a result of the airburst
and shock wave

that created a blast radius
over 60 miles wide.

The Chelyabinsk asteroid is
a sobering reminder

that our planet is vulnerable
to numerous dangers from space

that have the power to unleash
incredible devastation

and obliterate life on Earth.

JASON WRIGHT:
We think of Earth
as a pretty safe place,

but there's actually
quite a few things coming down

from outer space
that might hurt life on Earth.

PAUL SUTTER:
The Earth has suffered

innumerable cosmic catastrophes,

and this happens more commonly
than you might think.

Any day now, a rock could come
from outer space

and strike the Earth.

Any day now,
a supernova could go off

and irradiate our atmosphere.

Any day now,

our Sun could blast off
a coronal mass ejection

headed right in our direction.

So, even though
we have it relatively safe,

any one of these dangers
could strike at any moment.

SHATNER:
The fact that
we could suddenly be wiped out

in a cosmic cataclysm
is profoundly unsettling.

But it also begs the question,

what is the most imminent threat
to Earth's safety?

Well, if the explosion
over Chelyabinsk

in 2013 is any indication,

the answer would seem to be
killer asteroids.

WRIGHT:
Asteroids are
the leftovers of the formation

of all of the planets
in the solar system.

When the Sun formed,

it had a disk of material
around it

that formed lots of
boulders and rocks.

Many of these came together
to form the Earth,

Mars, Venus and even
the cores of the giant planets,

but not all of the boulders
and rocks got used up.

We know of over a million
asteroids orbiting the Sun

that are in orbits

that sometimes come
near the Earth.

And of those,
there are several hundred

that are potentially
the sorts of asteroids

that might hit the Earth
one day.

SHATNER:
Is a massive asteroid headed

for Earth at this very moment?

And if so,
how catastrophic would it be

for life on our planet?

According to experts,

the answer can be found
by examining a place

where such a devastating
impact has happened before.

For many,
the lush vegetation

and tropical climate
of this region

makes it feel like paradise.

But when viewed from space,

the landscape tells
a much different story.

Because if you look closely,

the faint outline of
a 120-mile crater

can be seen stretching
from the jungle

out into the Gulf of Mexico.

The crater is a scar left
by a massive asteroid impact

that occurred
66 million years ago,

a disaster that is referred to
as the Chicxulub Impact Event.

THOLEN:
The Chicxulub asteroid was about
ten kilometers in diameter.

It did produce
a global catastrophe.

In fact,
it wiped out an estimated 75%

of all species
on the planet at that time.

It is believed to be responsible

for the extinction
of the dinosaurs.

Because with that particular
asteroid impact,

some of the finer materials,

the dust got injected
up into the atmosphere,

where it can linger for months,
if not years.

Now we've got dust

that's reflecting sunlight
back out into space

rather than making it
down to the ground.

You basically prevent plants
from growing.

Once the plants die off,
well, then the animals

that feed off the plants
start dying off.

And the whole food chain
gets disrupted.

That's one of
the reasons why there would be

such massive loss of life

if an asteroid a kilometer
or larger were to hit.

MICHIO KAKU:
Because the object that hit
the Yucatán of Mexico

wiped out the dinosaurs,

we want to know,
could it happen again?

Is there an object out there
in space with our name on it?

SHATNER:
According to experts,

there are some 2,300
known asteroids

that are considered
potentially hazardous.

Hopefully, we'll continue
to dodge these galactic bullets,

but what if it's only
a matter of time

before our luck runs out?

GRAHAM LAU:
NASA's doing sky surveys

using telescopes
and infrared and radar

and other ways to monitor

for these objects
that are out there.

We have most of those
identified and tracked.

But that's probably still
only a small fraction

of what's really out there.

And if we didn't catch one of
these things early enough,

that could really cause
massive devastation

for life as we know it.

SHATNER:
If another massive asteroid
heads towards our planet,

are we simply doomed
to extinction?

Or is there something
we could do

to protect ourselves?

MISSION CONTROL:
Three, two, one.

And liftoff.

SHATNER:
At Vandenberg Space Force Base,

a Falcon 9 Heavy rocket
blasts off,

carrying an experimental
payload in space.

Known as the Double Asteroid
Redirection Test-- or DART--

the spacecraft is bound
for a tiny asteroid

named Dimorphos, located
6.8 million miles from Earth.

Its mission is to crash into
the space rock at high speed

in an attempt
to change its orbit.

LAU:
The DART mission was

our very first attempt in space

to try out some method
of asteroid deflection.

The idea was to see
if we could redirect

an asteroid coming towards us,

to push it a little bit
out of the way.

SHATNER:
On September 26, 2022,

after ten long months
of traveling through space,

DART finally arrived
at Dimorphos

and successfully smashed into it
at almost 15,000 miles per hour.

LAU:
Hitting that asteroid was
actually very difficult.

We had a spacecraft roughly
the size of a school bus

that had to then hit a target
500 feet across.

Destroying such a target,

that's extremely difficult
to do.

WRIGHT:
NASA was hoping that all

of the momentum
that it hit that asteroid with

would go into moving
the asteroid out of the way,

and it was actually
extremely successful,

much more than they thought.

And that's great news
for protecting the Earth

because it means
we don't have to hit them

as hard as we worried we might.

SHATNER:
It's certainly a relief

that scientists have
a plan in place

to help save us
from giant killer asteroids.

But what about smaller rocks
from space?

Could they also pose
a threat to humanity?

Some scientists believe
that tiny meteorites

are potentially just as lethal

because they could carry
an alien virus

with deadly repercussions.

SHATNER:
The danger Earth faces

from a massive,
planet-killing asteroid

is both real and terrifying.

However,
another chilling scenario

involving space rocks
also exists.

Because at this very moment,
Earth is being bombarded

with millions
of micrometeorites.

And those seemingly
harmless rocks

could be carrying the seeds
of an extraterrestrial disease.

Every single day,
material from space

constantly rains down
onto the Earth,

somewhere around
100,000 pounds every day.

And we believe that it is
possible for some sort of

alien viruses to hitch
rides on micrometeoroids

and drift to the surface
of our planet.

LAU:
I think a lot of us
in astrobiology,

we've been so excited
for so long at possibly

finding definitive signs
of alien life out there.

But one thing
we don't talk about enough

is, what happens if there is
a malicious pathogen

coming from space to our planet
and infecting life

as we know it,
or changing life as we know it?

SHATNER:
Could an alien virus infect
and perhaps destroy

life on Earth?

It sounds like a horrific
scenario

out of a science fiction movie,
and yet scientists claim

that the threat posed by
an extraterrestrial plague

is very real.

There have been experiments
in which microorganisms

have been flown to
the International Space Station

and exposed to the hard
vacuum and the radiation

and the temperature changes
of deep space.

And many of those organisms
survived.

So I think it is
quite conceivable that material

raining down on
the surface of the planet Earth

could carry biology in
the form of viruses from

some other body
in our solar system

or even from
a distant star system.

SHATNER:
Is there anything we can do
to protect ourselves from

an extraterrestrial virus?

Perhaps a clue can be found
by examining how humanity

has prepared
for this threat before.

At Johnson Space Center,
dozens of NASA scientists watch

with nervous anticipation

as the Apollo 11 Lunar Module
descends onto the Moon.

But their concern is
not only for a safe landing.

NASA is also extremely worried

that the astronauts
may get infected

with alien microbes.

When Apollo 11 landed
on the Moon,

there were still
a lot of mysteries about

what they would
actually find up there.

Because no one could
be certain that there wasn't

some evil Moon plague up
on the Moon that the astronauts

would bring back with them,
the Apollo 11 crew was actually

quarantined for three weeks
starting the moment

they closed the hatch
after their Moon walk.

Being quarantined was easy
during the return trip home

because there was nowhere to go.

But once they were back
on Earth, this became a very

delicate dance of
transporting them from the ocean

to Houston without
exposing them to anything

or exposing what they might have
to the world.

SHATNER:
The Apollo 11 astronauts
spent a total of

21 days in isolation
after returning to Earth.

Fortunately, they emerged
with a clean bill of health.

But they weren't
the only ones NASA subjected

to a strict quarantine.

Nearly 50 pounds of Moon rocks
were collected on the mission,

and this material
was also rigorously tested

for alien pathogens.

Scientists did a bunch
of experiments to make sure

that there was nothing alive

and nothing
potentially disastrous

involved in those samples.

They actually injected crushed
up rock into insects and mice

to make sure that if
there was anything ingested

or something that entered
a human's bloodstream,

it wouldn't have
an adverse effect.

In the end, NASA scientists
realized that there

was nothing nefarious
up on the Moon.

There was no Moon plague
that the astronauts were going

to bring back with them.

And everything was safe
coming home.

SHATNER:
It's comforting to know
that NASA has procedures

in place to quarantine
a virus that astronauts could

potentially bring back
from space.

But what happens if
our safety measures fail?

How would we handle the outbreak
of an alien disease?

If an individual gets infected
by an extraterrestrial

microorganism or virus, the next
steps would be very critical.

That person would need
to be isolated right away.

And hopefully that person is not
exposed to the general public

because the unknown
component of what is causing

the outbreak would be very
difficult to handle right away.

Especially if it's not
measurable by our science.

At that point, that's when
the military would come in

to understand the nature
of the outbreak, how fast it is,

and then would there
be a way to contain it?

We haven't really dealt
with this yet because it's

such a hypothetical case.

But are we ready for that
worst-case scenario?

I'm not really sure we are.

SHATNER:
Deadly plagues have ravaged
our population

throughout human history.

So far, we've managed to survive
all of the lethal outbreaks.

But if an alien disease
ever spread across

our planet,
would we be so lucky?

All life on Earth shares

some basic biochemistry
in common.

We all use the same set
of amino acids, we all use DNA,

we all use proteins.

But alien life may have
a completely different set

of chemical rules
that it uses to govern itself.

So an alien pathogen
may try to get under our skin,

literally, and simply
nothing happens because

we're playing by
different rules.

On the other hand,
if an alien pathogen finds

itself on the Earth,
it could very quickly adapt

and evolve to
our local environment

and hijack our DNA
replication mechanisms.

Because it's-it's just
how life works.

Life finds a way.

Could a virus from
another planet invade Earth

and our bodies,
making us its new host?

It's a distinct possibility.

But experts warn that we face
an even graver danger.

One that's hit
our planet in the past

and can strike again.

A blanket of deadly radiation

that's millions of years old.

SHATNER: When we gaze up at
the stars, it's easy to forget

that the picturesque dots
of light we see are actually...

massive balls of fire
floating in space,

which burn at
unimaginably high temperatures,

just like our own Sun.

One day, some of these
stars will eventually die

in a giant explosion so bright,

it can momentarily outshine
the entire galaxy.

It's a cataclysm
that scientists refer to

as a supernova.

A supernova happens when

the nuclear fusion
powering the star

is no longer strong enough
to prevent gravity

from causing a massive collapse
of all the matter in the star.

And the amount of energy
released is incredibly intense

and happens
in a very short time.

If you have a star
somewhere around at least eight

to ten times
more massive than our Sun,

when it dies,

the entire star rushes inward
and bounces off of itself,

releasing a tremendous
amount of energy in

one spectacular burst.

And so, when the largest stars
in the universe die,

all that material
from the star...

...swirls around and
launches these beams

of radiation that appear
to us as a gamma ray burst.

And gamma ray bursts represent
some of the most

powerful explosions
that can happen in the universe.

SHATNER:
Could gamma rays
that originate light years away

actually pose a threat to life
here on Earth?

According to experts,
the answer is yes.

Because unlike the normal
types of solar radiation

that we experience every day,

gamma rays are often described
as death beams from outer space.

Gamma rays are the most powerful
form of light,

or electromagnetic radiation.

They're more powerful
than ultraviolet light,

they're more powerful
than X-rays.

They're all the way at the top

of the scale when it comes
to energy light can have.

PYLE:
Gamma rays are off the scale

in terms of dangerous radiation.

Even short exposure
to gamma rays

can scramble your DNA.

Extended exposure to gamma rays
are the absolute

top of the scale, and over time
will basically liquefy you.

A gamma ray burst
could easily destroy

not just one star but
many stars in the process.

We're talking about the energy
release that's comparable

to the Big Bang itself,
the creation of the universe.

If a gamma ray burst
were to happen in our vicinity,

not only would it affect
our solar system,

it would probably wipe out

all the neighboring
solar systems as well.

And so this is a threat
that could affect

a good sector of
the Milky Way galaxy itself.

SHATNER:
While the hypothetical threat of

a dying star
destroying our solar system

is terrifying to consider,

is there any evidence
to suggest that

our planet has been hit
by gamma rays before?

Curiously, the answer lies
at the bottom of the ocean.

In the scientific journal
Physical Review Letters,

a group of German physicists
announce a remarkable discovery.

By analyzing deep-sea
mineral deposits,

they are able to detect
a rare iron isotope

not typically found on Earth.

Known as iron-60,

it is formed only
in the explosion

of the most powerful supernovas,

and its presence on Earth
proves that our planet

was once struck by gamma rays.

SUTTER:
Not all gamma ray bursts

have happened billions
of light-years away.

Some have happened
much closer to home.

In fact,
astronomers estimate that

about 2.6 million years ago,

there was a significant
supernova burst

that may have led
to what we call

the Pleistocene
megafauna extinction,

which eliminated
something like 30% of

all large animals living
in the ocean at the time.

DENNIN:
The best theory we have
for the cause of

this gamma ray burst
about 2.6 million years ago

is the death of a massive star
that was 160 light-years away.

This sounds far away,
but in cosmic scales,

it's actually quite close,

so that kind of
gives you a sense of

the scale of this explosion.

SHATNER:
When a gamma ray burst

wiped out a third of life
in the oceans

2.6 million years ago,

mankind's early ancestors

were just beginning
to learn how to use tools.

Scientists aren't sure how
our species was able to survive,

but the event does raise
an important question.

Are scientists aware of any star
that is about to go supernova?

Surprisingly, there is one

that most people are
already familiar with,

whether they know it or not.

One of the most famous
constellations in the night sky

is known as Orion.

Orion consists of
seven primary stars

in the shape of
a mythical hunter,

but perhaps
the most recognizable

is the reddish-orange star
that forms its right shoulder.

It is a supergiant star named

Betelgeuse.

One of the stars
in our Milky Way that's

a good candidate
for going supernova

kind of soon is Betelgeuse.

The key for
a star to go supernova

is when the nuclear fusion
finally gives out

and isn't able
to support the gravity.

And that's going to
show up in various signatures

as you measure the light
coming from the star.

And that's the type of behavior
we're seeing with Betelgeuse.

SUTTER:
Betelgeuse is about
to go supernova any day now.

In fact,

because it's hundreds
of light-years away,

it may have already
gone supernova

and we're simply not
gonna find out about it

until the light reaches us.

And then you have to deal with

the large-scale
ecological collapse

that will follow it.

SHATNER:
If Betelgeuse is, in fact,
on the verge of going supernova,

then is there anything we can do

to protect ourselves from
the deadly gamma rays

it would unleash?

SUTTER:
The honest truth is

if a gamma ray burst
were to strike us

or were to be headed
in our direction,

there's nothing
we can really do.

We wouldn't know it
until it's too late.

Gamma ray bursts may be
the most powerful explosions

in the known universe.

However, some scientists
are concerned about a threat

that's much closer to home.

One where our oceans boil,

the atmosphere blows away,

and the Earth itself...

...dies.

SHATNER:
Since the dawn of the space age,

Earth has often been
referred to as The Blue Marble

because, when viewed
from outer space,

it's clear that 70% of our
planet is covered by water.

However, what cannot
be seen with the naked eye

is that Earth is surrounded

by a magnetic field,

which is
an invisible energy shield

that blocks damaging rays
from the sun.

Without this protection,

all of our planet's
life-sustaining water

would be in jeopardy.

Fortunately for us,
and all life on Earth,

our magnetic field protects

our atmosphere from
the sun's radiation.

But, more importantly
for the Earth,

it keeps the liquid water
on Earth's surface

instead of escaping to space.

The Earth's magnetic field

is our force field

that protects our planet

from the solar wind,

which is a stream
of charged particles

constantly coming
out of the sun.

KAKU:
Without our magnetic field,

the solar wind then
hits the planet,

and temperatures start
heating up too much.

And, at that point,
water boils away

and drifts into outer space.

So, it's a question
of life and death.

SHATNER:
The magnetic field
has shielded Earth's water

for billions of years.

And while scientists
have imagined

what would happen if
we lost our protection,

is it really possible for

a planet's magnetic field
to disappear?

According to experts,
the answer is "yes,"

and evidence of this
doomsday scenario

can be found on
the dry and dusty surface

of Mars.

SUTTER:
Mars had liquid water
and a magnetic field

at the exact same time that

the Earth did
billions of years ago.

And at the exact same time that

life was first
arising on our planet,

and the conditions on Mars,

as far as we can tell,
were exactly the same.

So this means Mars
may have also been

a home for life.

Then the magnetic field
of Mars shut down.

Without its magnetic field

that it had when
it was very young,

Mars, with its low gravity,

was simply not able to hold on
to its liquid surface water.

And so, Mars lost its oceans

and all of its water,
which is why

today, it's a dry desert.

BEN McGEE:
The Martian environment
right now

is completely inhospitable.

It lets radiation right
on in down to the surface.

It's ice cold.

I mean, these are extremes
the likes of which

no human being,

or life as we know it,
could survive.

SHATNER:
If Mars once had a magnetic
field and then lost it,

as scientists believe,

it begs the question

how did this occur?

And, more importantly,

could the same calamity
ever happen

on Earth?

McGEE:
The magnetic field

for a planet,
as we understand it today,

is all related to a molten core.

Any planet can have
a magnetic field if it has

a hot core and it's rotating.

It works like an electromagnet.

And that's why Earth has one.

Mars doesn't have
a magnetic field today

because its core went cold.

SHANNON CURRY:
One of the main theories on

why the magnetic field of Mars

effectively died was that

its core just stopped churning.

And we really don't
understand enough about

the interior of Mars to know
what the dynamics there were.

In fact, we barely
understand it on Earth.

But Earth's dynamo
could, in fact, stop.

WRIGHT:
The Earth has changed a lot over
its 4.5 billion year history.

We know today, though,

that as planets get older,
they get cooler,

and the mechanisms that generate

their magnetic fields
in their cores get weaker.

And over time,
that, in principle,

could ultimately lead to
the loss of Earth's water.

SHATNER:
Could our planet
become a barren,

lifeless world
like Mars one day?

It's a disturbing possibility,

and what's even more terrifying,
is that some experts think

it may already be happening.

Scientists from NASA
make an unsettling announcement.

Using data
collected by satellites,

they discovered a "dent"
in the magnetic field

where it is actually

getting weaker.

CURRY:
Earth is actually
losing some of its

global magnetic field.

What's less clear
is how much and how fast

that erosion is happening.

There are
leading theories on why,

but the loss
of Earth's magnetic field

would seriously impact life
as we know it.

There would be
huge shifts in radiation,

and, certainly,
that can seriously disrupt

the entire balance
of this system.

We would slowly lose our oceans,

and as things dried up,

it would become
much more barren,

and possibly lifeless.

It would certainly
have effects on human life.

KAKU:
In the coming centuries,
it'll probably go down to zero,

our magnetic field,

so we have to make sure that

the magnetic field of
the Earth is preserved

so that we don't have
an evaporation of the atmosphere

and the boiling of the oceans

like what happened on Mars.

We're talking about
a tremendous danger

to the planet Earth.

It's unsettling to think
that our bright blue Earth

could become as desolate
and lifeless as the Red Planet.

But even if we avoid that fate,

astronomers fear that right now

we might be
on a collision course

of galactic proportions.

SHATNER:
A team of astronomers
with the Canada-France

Brown Dwarf Survey project
announce a remarkable discovery.

Using infrared telescopes,
they are able to locate

a distant world
100 light-years from Earth.

But unlike every other planet

previously identified
by scientists,

this one isn't orbiting
around a star.

Instead, it is drifting alone
through our galaxy.

It is the first-ever observation
of a mysterious object

known as a rogue planet.

A rogue planet is
a planet that is

not attached to any star.

It simply floats free
throughout a galaxy.

♪ ♪

We think rogue planets happen

through the formation
of solar systems.

When solar systems form,
it's a chaotic mess

of planets that are
crashing into each other

and interacting with each other,

and they can eject
some of those planets

and send them flying out
throughout the galaxy.

But on top of that,

they can have all sorts of
wild and crazy motion

because they were ejected
from solar systems

in all sorts of wild
and crazy directions.

And so there could be
a rogue planet headed at Earth.

SUTTER:
It sounds preposterous
to most people,

the idea that another planet
could enter the solar system

and be the end of us.

But that doesn't mean
that one can't come

hurtling out of the darkness.

And if one of them
happened to come in

on a collision course
with Earth,

that could be it.

SHATNER:
Could a rogue planet
actually drift

into our solar system
and collide with Earth?

It may sound far-fetched,

but experts believe
the impact would unleash

apocalyptic levels
of destruction.

The result of us getting hit
with another planet

would hypothetically
be devastating.

Based on our best estimations,

if you actually had
a titanic impact,

you're talking about a complete
global reset for both worlds,

the likes of which
no human being

or life as we know it
could survive.

SHATNER:
But is the threat of
a collision with a rogue planet

an actual concern,

or are experts simply
fearmongering?

As it turns out,
scientists may be

on to something because,
in fact,

the Earth has been hit
by another planet before.

LAU:
Earth has certainly gone
through many periods

of bombardment of objects
from space.

We had this early impact event

on our own planet,

roughly 100 million years
after it formed,

when a Mars-size world
that we call Theia

crashed into the Earth.

And in the process,
it blew off a bunch of material

from our surface
and made the moon.

SHATNER:
According to experts,
the impact with Theia

left the Earth in a fiery,
molten state

for millions of years,
inhospitable to all life.

But could it happen again?

Fortunately,
experts do not currently believe

that there is a rogue planet on
a collision course with Earth.

However, even the mere presence
of a rogue planet

in our vicinity could have
catastrophic implications.

Something like
the mass of the Earth

passing through
the inner solar system is--

we're barely gonna notice.

But something the mass of,
say, Jupiter

passing through
the inner solar system

will destabilize
all of our orbits.

It might send our planets
crashing into each other.

It will wreak havoc
through pure gravity alone.

SHATNER:
The notion that a rogue planet

simply passing
through our solar system

could cause so much chaos
is deeply unnerving.

And unlike a direct collision,
there is a distinct possibility

that a rogue planet might wander
into our neighborhood.

Because the sheer number
of rogue planets

currently roaming our galaxy
is mind-boggling.

WRIGHT:
These rogue planets tend to be
very difficult to find.

They're not orbiting a star,
so they're very dark.

So it can be very tricky
to figure out

how many of them
there might be out there.

But we think that there are
probably a few times

as many rogue planets as
there are stars in the galaxy.

So that means there could be
a trillion rogue planets

throughout the Milky Way.

SHATNER:
A trillion rogue planets
in our galaxy alone?

It's a disturbing notion.

But what's even more unsettling
is that Earth itself

might one day
become a rogue planet.

SUTTER:
A rogue planet passing
through the solar system

might destabilize Earth's orbit
to such a degree

that we become ejected
from our own solar system

and become a rogue planet.

This would be a game changer
for humanity.

Because the vast majority
of energy we receive

on the surface of our planet
comes from the Sun,

the source of light,
heat and warmth

and ultimately
of life on the Earth.

And that would be
cut off from us.

SHATNER:
Could a rogue planet
send the Earth careening out

into the cold depths
of the Milky Way?

Perhaps,
but many experts believe

the true threat to Earth
isn't a rogue planet

but a different type of visitor

to our solar system

in the form of
extraterrestrial invaders.

We officially inaugurate
the newest branch

of our military.

This is a very big
and important moment.

It's called the Space Force.

SHATNER:
President Donald Trump signs

the National Defense
Authorization Act,

creating the U.S. Space Force.

According to
its official mission,

the Space Force is intended

to protect the United States'
national interests

in outer space,

but some have wondered
whether it may also have

a secret objective.

Could the Space Force
have been created

to protect Earth
from an alien invasion?

The government has
a track record

of saying as little as possible
about UFOs.

But there is an argument

that extraterrestrials
may take the view

that it is logical to eliminate

any potential threat
to their own existence,

and emerging civilizations
like humanity

might be that threat.

So, there's a great logic

that governments should have
a range of contingency plans

because this is going to be
hugely impactful.

SHATNER: The idea of
aliens invading Earth

has been a staple of pop culture
since the early 20th century.

But is there any evidence

that the Space Force could
actually mount

a successful defense against
an extraterrestrial attack?

The U.S. Space Force created
their own military organization.

And just like
the Army has brigades,

the Air Force has wings,

the Space Force came up with
these deltas.

And there's several
different deltas,

with Delta 9 being
the one that's been charged

with orbital warfare.

So actually engaging in warfare
in orbit.

Delta 9 is focused exclusively
on what we might do

in the event
of something hostile

in space,
orbital combat, essentially.

So, if something
extraterrestrial

actually came into our airspace,

they have a detection system
and an intercept system

that launches very fast

and physically smashes something
out of the sky.

Right now,
we have 44 interceptors.

So, in a way, we're prepared

for someone to try
and kick down our door.

SHATNER:
It's fascinating to know

that the U.S. military
has systems in place

that could be used
in the event of

an orbital invasion by aliens.

But would our current
defense systems have

any hope of overcoming
advanced alien technology?

TRIMBLE:
The U.S. military has a pretty
vast and diverse arsenal.

But when you're talking about
alien spacecraft technology,

it's impossible to know
if we have any weapons

available to us
that would do us any good

in that kind of situation.

POPE:
Civilizations with, maybe,

millions of years
head start on us

probably have technology that
could crack this planet open

like a nut if they wanted to.

This is an existential threat.

SHATNER:
Is humanity able
to defend itself

in the event of
an extraterrestrial incursion?

Or are we doomed?

Let's hope we never find out.

But the fact is
that an alien invasion

is just one of
many dangers from space

that--
while they may seem remote--

are very real threats
to Earth's existence.

We believe that
the Earth is calm,

everything's okay.

Stuff happens in the universe,
but it's far away.

But we have been hit
by giant rocks

going tens of thousands
of miles per hour.

We have been slammed
by supernova.

That is going to happen
to the Earth

again and again and again.

DENNIN: When you think
about what would happen

that could wipe out
the human race,

it does feel like
we're always on the edge.

But I feel like

we keep moving to better
and better understanding,

and we're gonna better
and better protected.

At least if there is
a mass extinction

and some things survive,
I hope we're one of them.

It appears that
the universe is far more chaotic

than we tend to think.

I mean, just look at
all the planets around us.

They've been devastated
by numerous disasters.

From killer asteroids
and rogue planets

to deadly viruses
and lethal radiation,

so far Earth has survived
these dangers from space,

but will our luck run out?

For now, the answer remains...

unexplained.

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