All language subtitles for How.the.Universe.Works.S11E04.1080p.WEB.h264-CBFM

This show is fictitious.

There is not actually
an asteroid

headed to New York City today,

but this is based on
simulations of such an event.

We run simulations of
fictional asteroid strike

to prepare for
the worst-case scenario.

November 4, 2029.

We face a countdown
to catastrophe.

A giant asteroid hurtles
towards Earth.

It's heading straight for

the eastern seaboard of
the United States.

The space rock could wipe out
an entire city

and cause
widespread devastation.

Can Earth survive?

New York City, November 4, 2029.

The deserted metropolis waited
for the asteroid to strike.

A giant space rock entered
the atmosphere,

heading straight for the eastern
seaboard of the USA.

Heading straight for the eastern
seaboard of the USA.

As it comes through
the atmosphere,

we would see something as
bright as the sun getting

brighter and brighter
and brighter.

At speeds of maybe
20 kilometers per second or so.

That's something like
18 times faster than

the speed of a bullet
coming out of a rifle.

This asteroid was headed towards

the most populous city
in America,

and when it impacts,
it would deliver

more energy than
1,000 Hiroshima nuclear bombs.

More energy than
1,000 Hiroshima nuclear bombs.

It would level some of the most
expensive real estate

in the world in seconds.

There would be a crater where
Central Park used to be.

There would be a crater where
Central Park used to be.

I actually don't even like
thinking about this,

of how horrible it would be.

This is beyond the
worst disaster

the world has...
Would have ever faced.

There's nothing in our history
that would have

done this much damage so
quickly and so devastatingly.

The story of the asteroid

and the Earth's fight back

started seven years ago,
here in Arizona.

September 2022,

the Catalina Sky Survey.

Guardian of heavens
Greg Leonard drives

to Mount Lemmon Observatory
near Tucson.

He's on the hunt
for asteroids and comets.

He's on the hunt
for asteroids and comets.

We are the watchers of
the skies for the planet.

We literally represent
the first line of defense

against potentially
incoming asteroids,

and I want to emphasize
the words planetary defense.

This is not in the benefit
for one nation.

This is for the entire planet.

Greg takes a series of images

over a 20-minute period.

Stars don't move in the photos,

Stars don't move in the photos,

but asteroids and comets do.

A-ha.

We can see four points of light

tracking across the background
of the stationary stars.

This one is moving very
quickly across the sky.

So this tells me

this is a real
near-Earth asteroid candidate.

It's one of over 27,000
near-Earth asteroids,

It's one of over 27,000
near-Earth asteroids,

or NEAs for short,
discovered by the early 2020s.

The huge gravity of Jupiter
can rip space rocks

from their home
in the asteroid belt.

Some race outwards,
away from the sun.

NEAs head inwards,
occasionally towards Earth.

We didn't know it
back in September of 2022,

but these were our first images

of a deadly incoming asteroid.

It's relatively close
to Earth's neighborhood.

We don't know exactly
how far it is yet,

but it's close enough where
its motion across the sky

appears rapid.

The discovery
of an NEA set a series

of planet protection protocols
in motion.

Step one, enlist
a global team of experts

to investigate
the asteroid's orbit.

We have
some of the brightest minds,

some of the best telescopes,

some of
the biggest supercomputers

working to protect Earth,

collaborating
across language barriers,

across international
borders to protect humanity.

This international
planetary defense team

was tasked with discovering
if the distant object

was tasked with discovering
if the distant object

would become
a serious threat to Earth.

Their first job...

Determine if the NEA's orbit
would intersect with our own.

Orbits are
a little like roads, right?

You've got a path
that something follows,

and they can intersect,
you can have a crossroads.

Now, typically, if only one
object is there,

that's not a big deal,

but if you have two objects
approaching that intersection

at the same time,
they could collide,

and that's the danger
from asteroids.

And that's the danger
from asteroids.

The team of scientists

track the asteroid
for four months.

Over time,
you can build up observations.

You can gradually narrow down
the possible number of orbits,

then determine whether there's
any chance of a future impact,

but if the asteroid
is orbiting the sun,

the Earth is orbiting the sun,
and there's this dance going on.

Sometimes the asteroid
is near the Earth,

Sometimes the asteroid
is near the Earth,

and we can observe it,
it's bright.

Other times the asteroid is

on the other side of the sun.

We can't observe it at all.

We were lucky.

The asteroid was visible
throughout the fall of 2022.

However, our observations of
the space rock's orbit

showed a very real possibility

that it would slam into Earth
in just seven years.

Astronomers gave
the incoming asteroid

a suitably appropriate name,
Apep.

Apep was
the Egyptian god of chaos,

so that's a fairly good name
for an asteroid

that could hit the Earth

because that's exactly what
would happen.

You'd have chaos,
destruction, and death.

A catalog of devastation
to be
unleashed on Earth.

But just how bad would
the impact be?

January 2023.

Asteroid Apep was on
a collision course with Earth.

Step two in our
planetary defense...

Know your enemy and build up
a picture of the asteroid.

Apep was 1,800 feet wide,

Apep was 1,800 feet wide,

five times the length of
a football field.

Its huge size bumps it up into
a new category of asteroids.

Apep was what we refer to as

a PHA, a potentially
hazardous asteroid.

We're talking about something

that is a third of a mile
across.

This is enormous.

An 1,800-foot-wide asteroid is
about 112 million metric tons.

An 1,800-foot-wide asteroid is
about 112 million metric tons.

That's over 300 times the weight
of the Empire State Building.

Computer simulations
of the impact

of an asteroid that massive
hitting a city

revealed extraordinary levels
of destruction.

An 1,800-foot-diameter asteroid,

that would create a crater

that's 3 or 4 miles across,
1,600 feet deep.

It would have a radiation
blast wave that

It would have a radiation
blast wave that

would set things on fire
for about 20 miles,

but no sooner would things be
lit on fire,

there would be
a 500-mile-an-hour wind

radiating out,

leveling buildings,
knocking down trees,

destroying highways.

100 miles away, you'd still feel
a magnitude seven earthquake.

It's not easy to say what is
going to kill you first.

It's probably going to be
simply the flash of energy.

It's probably going to be
simply the flash of energy.

There's so much heat from this
thing that you can be vaporized.

If you somehow survived that,

then there's going to be
the blast wave that will

pulverize anything in its path.

To build an accurate simulation,

the scientists used
more than size and mass.

They also studied
its composition

and the speed of its orbit.

You need to know what
an asteroid is made of,

the speed of that asteroid,

how large it is in order
to understand,

how large it is in order
to understand,

will it make it through
Earth's atmosphere,

and what might the impact
effects be?

Asteroids vary in
composition and structure.

Some are loose collections
of small rocks,

others rocky and compact.

The most dangerous are metallic.

A metal asteroid can be five
times as dense

as some of
the lower density asteroids,

as some of
the lower density asteroids,

and so for the same speeds
on the same orbits

they pack way more punch
when it comes to an impact.

If you want to see exactly

what a metallic asteroid can do,

go no farther than
Barringer Crater in Arizona.

Now that crater is about
a mile across,

and the meteor that made it was
only about 150 feet across.

Arizona, 50,000 years ago.

The last major asteroid strike
on present day North America,

The last major asteroid strike
on present day North America,

a tiny metallic space rock

hits the ground
at 25,000 miles an hour,

releasing energy equivalent to
2.5 million tons of TNT.

Scale that up to the size of
1,800-foot Apep,

and it would create a blast
wave the size of Delaware.

If Apep were a metal
asteroid, it would tear through

If Apep were a metal
asteroid, it would tear through

the atmosphere
like a cosmic bullet.

In a modern city,
without warning,

it could kill a lot of people.

But although
they're very dangerous,

they're also very rare.

More common are rubble piles,

loose collections of small
rocks held together by gravity.

Rubble pile is kind of
the perfect name for them,

but you can think of them as
like a literally

a pile of stuff out of a dump
truck in your driveway,

but if you take that and you
put that in space,

they don't have much gravity
but they have enough to stay

bound to each other,

and that's your rubble
pile asteroid.

They are just barely holding
on to themselves.

If you were to come and just
apply sufficient gravity,

you could rip it apart.

You could rip it apart.

Pressure and heat from
entering our atmosphere

can also tear a rubble
pile asteroid to pieces,

but that can be just
as dangerous to a city below.

The breakup of an asteroid in

the upper atmosphere is...
Is pretty devastating.

It's like a nuclear weapon
going off in the atmosphere,

flattening buildings
and breaking windows.

Flattening buildings
and breaking windows.

There are going
to be mass casualties

from an event like that

due to just the injuries
from flying glass and debris.

To discover what type of
asteroid Apep belonged to,

the planetary protection team

train their telescopes
onto the space rock.

Analysis revealed that Apep
was a rocky,

carbonaceous chondrite asteroid,
or C-type for short.

Carbonaceous chondrite asteroid,
or C-type for short.

C-type asteroids like Apep

are less dense
than metal asteroids,

but more solid than
rubble piles.

If a big enough C-type asteroid

penetrates the Earth's
atmosphere,

it has the chance to make it
all the way down to the surface.

It doesn't necessarily burn up
in the atmosphere.

Apep's size, mass, and
composition told us

Apep's size, mass, and
composition told us

it would punch through our
atmosphere and hit the surface.

The final piece of information
needed to accurately predict

the true amount of damage
from the impact

was Apep's kinetic energy,
the amount of energy

the asteroid would punch
into the ground.

The kinetic energy of an object
depends on the mass,

and it depends even
more strongly on the speed.

And it depends even
more strongly on the speed.

More mass creates more
kinetic energy,

but more velocity will
increase the kinetic energy by

a squared factor.

For example, if something has
twice the velocity,

it will have four times
the same energy.

Scientists calculated how
much energy Apep,

weighing in at 123 million tons

and traveling at 40,000
miles an hour,

would transfer into the Earth.

Would transfer into the Earth.

So what kind of energies
were involved here?

Uh, you know,
1,800-foot diameter asteroid.

It's 112 million tons,

and it's traveling
at 40,000 miles per hour.

That's something on the order of

10 to the 19th joules of energy,

a one followed by 19 zeros.

1.8 times 10 to the 19 joules
is equivalent to 5,000 megatons.

1.8 times 10 to the 19 joules
is equivalent to 5,000 megatons.

Take a one megaton nuke,

a substantial nuclear weapon,
and then blow up 5,000 of them.

That is roughly the same
amount as all the nuclear

weapons on Earth,

detonating all at once.

A strike this large would
affect the whole planet.

This would have global impacts.

We would have to deal with
the fallout,

We would have to deal with
the fallout,

the literal fallout
from this event for...

For potentially 1,000 years.

Spring, 2023.

We had two choices...

Do nothing and face
a planet-changing catastrophe,

or fight back.

We chose to take on Apep.

It was the first time
in human history

that we might actually be able
to prevent a natural disaster

that we might actually be able
to prevent a natural disaster

from happening.

We could plan and launch
a response mission,

so we don't have
to get out of the way.

Make it get
out of the way instead.

The mission's objective
was simple...

Stop the asteroid,
and save the world.

We can't superglue
an earthquake fault shut.

We can't cork volcanoes,

but planning
for an asteroid impact

but planning
for an asteroid impact

is something we really could do.

June 2023.

A large asteroid
was headed towards Earth.

It was predicted to strike on
November 4, 2029.

To protect our planet,

A team of scientists plan to
deflect the asteroid.

A team of scientists plan to
deflect the asteroid.

An 1,800-foot wide asteroid

was headed towards the Earth.

We needed it to go in
literally any other direction.

So how could we
push Apep off course?

Scientists found a clue in
the asteroid belt.

Sometimes the lumps
of space debris collide

Sometimes the lumps
of space debris collide

and change their trajectory.

Maybe we could replicate this
and deflect Apep.

We could try to deflect the
asteroid and change its orbit

so that it actually
misses the Earth.

If you do it early enough,

it may not be much, less than
half a millimeter per second,

but that is enough.

These asteroids travel for
millions of miles, and so over

the course of days, weeks,

the course of days, weeks,

months, and years, it will have
a radically different orbit.

Sounds simple.

Send up a rocket with
a robotic space probe,

travel millions of miles,
and knock Apep away from Earth.

Piece of cake.

In the movies,

when there's a threatening
asteroid that's found,

there's always a rocket on
the pad ready to go after that,

and it's not the case
in real life.

And it's not the case
in real life.

It takes years
to design the mission,

to build the satellite,
to launch it,

and then it has to get there,

and that might be millions
of miles away from Earth.

Fortunately,
Earth had a head start.

We detected Apep early,

and we'd already built
an asteroid deflector called

the Double Asteroid
Redirection Test,

or DART for short.

In 2021 we sent DART
6.8 million miles

to rendezvous with
an asteroid called Didymos.

Didymos posed
no threat to Earth,

but allowed us
to test the technology.

The asteroid called Didymos

has a small moon asteroid
going around it.

The point of the DART mission

was to send an impactor
into this little moon

and see how much we nudge
it off the orbit that it's in.

Lessons learned from DART

would inspire a new mission.

November 2025.

We launched the DAAFE mission...

Deflect Apep away from Earth.

This wasn't a test run to
a safe asteroid.

This was the real deal,
a mission to save our planet.

It was an enormous
technical challenge,

and we had no idea
if it would work.

And we had no idea
if it would work.

When you think about
a spacecraft going from Earth

millions of miles away
to hit an asteroid

at an exact point in time,

at an exact point in space.

It's really
the ultimate bullseye.

It's like trying to hit one
bullet with another bullet

launched from the other
side of a continent.

November 2028.

After three years in space,
DAAFE arrived at Apep.

After three years in space,
DAAFE arrived at Apep.

This was our last chance.

This was our only chance.

The kinetic impactor

smashed into Apep
at 14,000 miles an hour.

On Earth, telescopes and radar
tracked the collision.

Did it work?

Did we push the asteroid
off course?

Did we push the asteroid
off course?

At first glance, the
mission worked.

We deflected Apep away from us.

It looked like the
mission worked.

As an astronomer, and, you know,

a human who has to live
on this planet,

I was very happy, right?

We've just literally
saved the world.

But the happiness
was short-lived.

There was a problem.

The collision had pushed Apep
away from Earth,

The collision had pushed Apep
away from Earth,

but it also sheared off
a 300-foot chunk of rock.

This smaller asteroid,
called Apep 2.0,

could still be
a significant threat.

A 300-foot chunk of rock
is still very, very large.

300 feet wide.

That's almost a football field.

So the important things
we needed to know...

So the important things
we needed to know...

Was it going to hit us?

And if so, where is it going
to hit us?

March 2029, we got our answer.

Its point of impact...

The east coast
of the United States,

with New York City
in the firing line.

A smaller chunk headed
for New York City.

This was
the worst-case scenario.

This was
the worst-case scenario.

I want to emphasize,

there's no asteroid
headed toward New York tonight.

This is just a discussion about

what this process would be like.

In 2028,

we tried to deflect
Apep away from Earth.

The mission wasn't
a complete success.

The mission wasn't
a complete success.

Yes, we managed to
actually divert

the large asteroid away from
hitting the Earth,

but in doing so, we broke off
a clump big enough

to be very dangerous heading
toward the eastern seaboard.

June 2029,
five months to impact.

The future looked bleak for
New York,

but it wasn't the time
to give up.

They reassessed an idea

first suggested to destroy
the original 1,800-foot Apep,

first suggested to destroy
the original 1,800-foot Apep,

a nuclear strike.

It worked in Armageddon.

Maybe it would work in
real life.

However, studies revealed
that nuking an asteroid

wasn't as simple as it looks
in a Hollywood movie.

Hey, let's blow it up.

Let's nuke it, right?

Well, instead of one
big problem,

now you have
slightly smaller problems,

and they're radioactive,
by the way.

And they're radioactive,
by the way.

So you don't want to do that.

Computer simulations revealed

that even the world's largest

nuclear weapon had only
1 percent of the energy needed

to destroy the original
1,800-foot Apep.

We needed the world's most
powerful nuclear weapon

and 99 of its best friends,
launch them all simultaneously,

and have them simultaneously
hit the asteroid.

And have them simultaneously
hit the asteroid.

It was simply beyond our
technological capabilities.

Fortunately,
thanks to the DAAFE mission,

we only had to take out
the 300-foot Apep 2.0.

Could we blow the smaller
asteroid out of the sky?

Maybe, but launching
a nuclear Hail Mary

would be very controversial.

Would be very controversial.

Nuclear devices
are the most powerful,

really, one of the
most emotional

things that humans have
ever invented.

They are the most
powerful tool in our toolbox.

We've got a hammer,
and it's a very big hammer,

but there are a lot of
concerns with them,

so they cannot be
tested in space,

according to international law.

According to international law.

Without being able
to test nukes in space,

they were considered
too big a risk,

but New York had one final
potential savior,

the Earth itself.

2013, Chelyabinsk, Russia.

An asteroid blew up
in the atmosphere.

An asteroid blew up
in the atmosphere.

It didn't make it all the way
to the surface,

and the people in Chelyabinsk
are very lucky because of that.

The 60-foot-wide
Chelyabinsk asteroid

was rocky like Apep,

and it moved
at a similar velocity,

around 40,000 miles an hour,

but it met its match when it
entered Earth's atmosphere.

Earth's atmosphere
doesn't look like much.

You think, oh, it's just air,
it doesn't matter,

You think, oh, it's just air,
it doesn't matter,

but all of those molecules
actually exert pressure

on the front edge
of the asteroid,

slowing it down
and heating it up.

Rock heated up

and began to crumble and explode
as it came through.

The midair explosion,
called an airburst,

released more energy
than 440,000 tons of TNT.

The shockwave traveled
100 miles,

damaging 7,000 buildings

and injuring 1,500 people.

But a ground strike
hitting a city

would have been a lot worse.

Apep 2.0 was five times larger
than the Chelyabinsk Rock.

Would it break up during its

10-second trip down
through the atmosphere,

or would it pierce
right through?

Or would it pierce
right through?

The planetary defense team
ran simulations.

As that comes through
Earth's atmosphere,

some of that hot air can get
into the cracks.

Friction and pressure
would heat Apep 2.0's

surface to thousands of
degrees Fahrenheit.

At those temperatures,
even rock burns.

We would see this
flaming monster

We would see this
flaming monster

of death coming racing
through our atmosphere.

There are gonna be pieces of
debris vaporizing

and coming off of it.

So you get these flashes of
light that happen

one after another... pop, pop,
pop, pop, pop, pop, pop,

as these things are blowing up.

The computer simulations

showed that the extra bulk of

Apep 2.0 would stop it from
blowing up.

Some of the asteroid would
blast away,

but most of the space rock

would reach the Earth's surface.

So that close to the
actual impact,

we pretty much just had to
hunker down and take it.

The prospects for
New York City were grim.

It was facing annihilation.

October 2029.

Three weeks to impact.

For the citizens of the New York
metropolitan area,

there was only one goal...
Get out of the firing line.

Now we had to have

the plans in place
to evacuate these cities.

The plans in place
to evacuate these cities.

It was a major emergency for
New York and its citizens.

Time to move out of the way.

To work out who
should evacuate and to where,

Scientists ran detailed
projections

of the potential blast area.

There's an ellipse there that
we call the hazard ellipse that

says somewhere in this area is
where the asteroid will hit.

That means there's
a little wiggle room

and a range of areas
that are in danger.

And a range of areas
that are in danger.

Based on the hazard
ellipse projections,

the government issued
evacuation orders

for the tri-state area,

and as far south
as Philadelphia.

It was the biggest evacuation
in US history.

Millions were displaced.

It was physically horrific.

I live in the New York
metropolitan area.

It was horrible for me and my
family and my friends,

It was horrible for me and my
family and my friends,

but we can't just sit here and
cross our fingers and hope that

we don't get struck.

The freeways out of the
city were jammed.

Trains were packed.

Over 23 million
people evacuated,

leaving behind a deserted city.

Computer models
show that the epicenter

of the strike
would be Manhattan.

Of the strike
would be Manhattan.

The blast would reduce
the city to rubble and ash.

There would be a one-mile-wide
crater resulting from it,

so deep that
it would actually take

the entire subway system and
turn it upside down and lay it

onto the rim of the crater.

You would have
a magnitude 5 earthquake

at even six miles away
from that,

and there would be
a big air blast,

400-mile-an-hour winds.

400-mile-an-hour winds.

Something as light as a pencil
could be a lethal weapon

when picked up by a shock wave
like that.

As the crater is blasting out
and excavating itself,

there would be little blobs of
molten rock that get thrown out

in this wave, going faster than
the speed of sound,

Like drops a fiery rain,

if you will, landing back miles
away from the crater.

The city would be on fire.

So, um, there's just
no upside to this.

There's nothing good.

It's just all
from bad to horrific.

But New York is by the ocean.

What would happen if Apep 2.0
hit the sea?

Detailed simulations have
revealed two very

different outcomes

for an asteroid hitting
the ocean at high speeds.

If a giant asteroid
strikes the deep ocean,

less than 1 percent
of its energy

gets converted into waves.

Those waves quickly disperse.

They quickly lose energy as
they travel.

By the time they reach
the coast, it might just be

a little ripple,

you might not even be able to
surf on it.

If the asteroid hit
shallow coastal waters,

it could cause significant
damage along the shoreline.

If an asteroid, the size of
Apep hits the continental shelf

where the water is
relatively shallow,

then it could potentially
cause a tsunami.

But that would just be
the start of the problems.

With a shallow water impactor,

huge amounts of steam are
generated basically by

the energy of that impactor
vaporizing all the water.

Well, all the water is then put
up into the atmosphere,

and water is a really good
greenhouse gas.

So you have warming from
the launch of water

up into the atmosphere.

You have cooling
from all of the ash and dust.

A short bout of warming

would be followed
by a brutal winter.

Would be followed
by a brutal winter.

Crops would fail.

This impact has so many
horrible follow-on consequences.

That tells us how difficult
it would be to...

To rebuild from an event
like this.

The eastern seaboard

would suffer a serious economic
downturn.

It would take decades
to recover.

November 3rd, 2029.

One day until impact.

The space rock was just
400,000 miles away,

and traveling 13 times faster
than an F-15 fighter jet.

It was first a dim star,
and then a brighter star,

and then in the hours before,
you can actually see it

approaching the Earth.

New York looked outmatched.

New York looked outmatched.

It looked like Apep would win,

but this was not the end of
the game.

Earth had one final card
to play.

November 4th, 2029.

The 300-foot Apep 2.0
reached Earth.

The space rock pierced our

atmosphere and hurtled
towards the surface.

Then the asteroid passed
over Manhattan,

over Brooklyn,

and over Coney Island.

It hit deep ocean,
350 miles off the coast.

Apep 2.0 missed New York.

But how?

Our 7-year battle with
the asteroid

resolved in a matter of seconds

thanks to orbital dynamics.

The orbit of the asteroid
and the orbit of the Earth

and the way the Earth spins in
this great cosmic ballet

means that

a few seconds earlier or later
makes the difference between

hitting the ocean
and hitting land.

Hitting the ocean
and hitting land.

Earth rotates at
1,000 miles an hour

and orbits the sun at close
to 65,000 miles an hour.

Apep orbited
at 40,000 miles an hour,

but Apep 2.0 traveled
fractionally slower.

The impact of the DAAFE mission
that sheared off

the 300-foot chunk of rock
had also slowed it down.

Slowing down Apep

Slowing down Apep

changed when it's going to
intersect the Earth.

So New York spun out of
the crosshairs.

Apep 2.0, hit
the ocean and exploded,

breaking up instantly.

The strike threw up a wall of
water into the air,

followed by huge clouds
of steam.

The impact created small
surface waves that quickly

died away.

Died away.

It's like doing a gigantic
interplanetary belly flop.

It evaporates, it obliterates,
and it generates

an enormous amount of steam,
and it sets up shock waves.

All that energy is still
released,

but the ocean is capable of
absorbing it.

New York dodged the
bullet and escaped unscathed

thanks to the
dedication, ingenuity,

and enterprise of a global
team of scientists.

And enterprise of a global
team of scientists.

Apep was an imaginary asteroid,

but there are many potentially
hazardous space rocks out there.

Thankfully,
this was a fictional scenario.

It's a thought exercise, but
it's informed by our real,

actual knowledge we've gained
over the years of dealing with,

you know, potential close
approaches and the hazard from

you know, potential close
approaches and the hazard from

real asteroids that we actually
know about.

Asteroid research is a good
insurance policy

for our species.

Hopefully we will never need
to carry these things out

for real.

Large asteroid strikes are rare,

but we cannot be complacent.

The most important thing to
do in planetary defense

The most important thing to
do in planetary defense

is to find them early.

If we find them early, we have
a chance to predict

the possible impacts and we
have a chance to mitigate them.

Our technology is improving,

so we can detect incoming
space rocks earlier,

but we need to be vigilant,

because the threat from
asteroids is not going away.

Apart from climate change,

asteroid strikes are, in my
opinion, the most dangerous

thing to life on Earth.

A lot of the times
the question I get is,

"What are the chances of this
happening?"

And they don't like the answer
because I say 100 percent.

It takes time.

It may not be for a week,
a month, a year, a century.

But studying these asteroids
informs us on

what we can do
to prevent an impact.

There are a lot of natural
disasters that we can do

nothing about...
Earthquakes, hurricanes,

nothing about...
Earthquakes, hurricanes,

that sort of thing.

Here is
something way more devastating

than any of those,
and we can prevent them.

So we have to keep our eyes on

the prize and our eyes on
the skies.