How the Universe Works

We've seen the film.

A huge asteroid heads towards Earth.

It plunges through the atmosphere and slams into our planet's surface,

sending up a huge fireball and a deadly shockwave.

Humanity dies screaming.

But this is not one of those films.

This is how we and the Earth can fight back.

Putting the apocalypse on hold.

Planet Earth.

A cradle of life floating peacefully through space.

Or is it?

Our planet can be one of the most dangerous.

Most hostile places in the universe.

Think about what natural disasters befall humanity.

Earthquakes, hurricanes, tornadoes, all of these sorts of things.

We can't do anything about those.

But an asteroid, hey, this is a huge natural disaster that we can actually prevent.

When people hear the word asteroid, the first thing that comes to mind are

these Sci-Fi movies of these very dangerous asteroids coming to hit us.

The story of how the dinosaurs became extinct.

Yes, there are some asteroids out there that are dangerous.

When it comes to finding asteroids and defending the Earth, scientists are very solidly the heroes.

Across the world, teams of planetary protectors are working out ways to halt an apocalypse.

They're scanning the skies, doing the calculations, designing the technology,

and making the plans that could ensure planetary extinctions from space are nothing more than science fiction.

If you're facing an opponent, you need to know a lot about them in order to defeat them.

Their size, their strength, what they're made of, how they move.

Well, we need to know the same things about these asteroids, because we want to knock them out.

Kathy Plesko from Los Alamos National Laboratory is in Arizona.

Around 50,000 years ago, this was the site of an impact that left a crater over 170 meters deep.

This is Meteor Crater.

This is awe-inspiring to stand on the rim of a crater like this and see the scale.

Of something this large and feeling this small.

Understanding just how much energy it must have taken to excavate this much rock.

The meteor that carved out the crater landed with the power of a hydrogen bomb.

Yet it was just 40 meters across.

Meteor Crater is helping us understand how speed can turn a small projectile into a killer.

An asteroid came in at about 27,000 miles an hour.

That is 10 times faster than the muzzle velocity of a bullet coming out of a rifle.

It comes slamming into the surface and just explodes.

And that explosion then opens up the crater.

The force of the impact turned the surrounding solid rock to dust and sent an immense shockwave barreling outwards.

It's pretty windy here today, but that's nothing like it would have been in the shockwave from an impact.

Anywhere nearby here would have seen winds of thousands of miles an hour as the shockwave came out.

Scientists calculate there's a 20% chance of a similar strike on Earth every century.

If an asteroid like this struck today, it could destroy a city.

But Kathy's research is helping build up our defenses.

So we think that there's a variety of ways that we might prevent an asteroid from hitting the Earth.

My colleagues and I at Los Alamos and at Livermore and at other places can use

computer models on supercomputers to do very careful, high-fidelity simulations to

tell us what's a good idea, maybe what's not a good idea, and then be able to

present to policy makers, okay, here's what we can do in comparison to what Bruce Willis could do.

The most potent weapon that planetary protectors can currently utilize is a nuclear bomb.

However, using one to blow up an asteroid has its drawbacks.

It risks showering the Earth with hundreds of smaller meteors.

But Kathy's team is working on plans that would avoid this risk.

They'd use a nuclear weapon to deflect an asteroid instead.

So one of the things I do study is nuclear deflection.

In some cases, and in the near-term future, there could be a scenario where we

might need to shove something fairly large out of the way.

And those sorts of things, if they're large enough, we might need to use a nuclear device to do that.

We might launch a nuclear device, detonate it above the surface of the object, changing its velocity a little bit.

Detonating a nuclear device near an asteroid vaporizes part of its surface,

pushing the asteroid off course.

But firing nuclear weapons into space is no one's first option of choice.

So there are some pros and cons to using nuclear deflection.

There are some situations where it is definitely an appropriate technology,

where it may be the only option at the time.

But we hope in the future that we'll have other methods at our disposal that are not

as challenging diplomatically or politically.

And scientists are currently on the hunt for a new technology.

To find a way to deflect an asteroid without using nuclear weapons.

We're discovering more and more about the asteroids.

We're understanding them.

And we're realizing that there really are ways we can mitigate the destructive effects of an impact on Earth.

This could be the most important scientific endeavor humanity has ever undertaken.

And the best way to cancel the asteroid apocalypse could be to destroy them before they can be destroyed.

Before they even become a threat.

Our solar system is a dangerous place.

Fast-moving asteroids hurtle through space.

And many of these rocks are headed our way.

To counter the asteroid threat, scientists are drawing up battle plans.

The very first step in understanding this hazard and in preventing this hazard is to find them.

Not just the big ones that can end our civilization, but even the small ones that can devastate your city.

However, just finding these asteroids won't be enough.

We need to find them early in order to have time to deflect them.

The problem is that asteroids are smaller and darker than things such as planets.

And in the vast darkness of space, that makes them much harder to find.

Asteroids are pretty good at playing hide and seek in their own way.

Imagine you're flying over the Sahara, and you're looking for a pebble that's the same color as the desert.

That's what looking for asteroids is like in the solar system.

Astronomers believe there are more than a million asteroids a kilometer wide within our solar system.

And that there could be millions or even billions more that are smaller.

There's an uncountably large amount of asteroids in our solar system.

We're constantly looking and it's hard to find them all because they're tiny dots in a very dark background of space.

High in the mountains of the Catalina Sky Survey in Arizona, asteroid hunter Greg Leonard is leading the search.

We are the eyes for the world on this night at this telescope on the summit of this mountain.

By comparing four images of the same patch of sky taken over a 20-minute period,

Greg can hunt for elusive asteroids hidden among the stars.

That's because in these images the stars don't move, but the asteroids do.

If it's a really bright asteroid, we will see some bright, points of light tracking across the four images.

You have to kiss a lot of frogs before you get a prince or a Princess, and this is

the case tonight, as it is almost every night.

Ah, here we go.

This is a real object.

You can see it's moving across the sky here, from the lower right to the upper left.

We are very, very excited to have discovered one tonight, because this is an

object that's approaching, nearer to space, likely in the neighborhood of Earth.

Greg's research revealed this 30-meter asteroid could get as close as 1.

01 million kilometers to Earth.

That's less than three times the distance to the Moon.

Yet in the future, this asteroid's orbit could move closer to Earth and even onto a collision course.

If that happens, we need to be prepared.

And the earlier we spot it, the better our chance of altering its course.

Space is so big and the Earth is so small, and the asteroid would be starting from so

far away, that if you just deflected it a little bit, gave it a little nudge,

a tiny course correction, by the time it got to where the Earth's region is,

it would miss us completely.

To do that, we need to move asteroids off their trajectories.

Think of a golf swing.

Hook or fade the ball by just one degree off the tee, and you'll miss the green completely.

Now scale that up to asteroids.

Over time, these space rocks can leave their home in the asteroid belt,

becoming threatening near-Earth objects 50 million kilometres away that could one day hit our planet.

But if planetary protectors can change the course of a dangerous object by just a

tenth of a degree, it would miss the Earth completely.

And scientists have developed a very direct way to do it.

In a football game, if somebody on the defense is seeing the quarterback running into the end zone, what do they do?

Boom, hit him, knock him out of bounds, knock him down, do something like that.

That's what we want to do with asteroids.

So if we send something moving towards an asteroid very quickly to hit it, we call that a kinetic impact or.

Slams into it really hard, changes not just the velocity of the asteroid,

but also its trajectory.

Scientists have already intercepted asteroid-like objects in space.

In 2005, the Deep Impact spacecraft arrived at Tempel 1.

A 14-by-4-kilometer comet.

This spacecraft shot a little probe at the comet,

which slammed into Tempel 1, kicking up material from the surface.

Research is continuing into kinetic impactors.

In 2022, a spacecraft called DART will slam into an asteroid at over 20 meters.

21,000 kilometers per hour.

That transfer of momentum would change the velocity of the

asteroid just a little bit, maybe a fraction of a mile per hour.

But over maybe a decade, that change in velocity, even though it's very tiny,

would add up to a change in position big enough to completely miss the Earth.

Knocking a giant space rock off course might sound unusual.

But astronomers have discovered that in space, it's occurred a lot.

When you have a lot of traffic driving down the highway and a lot of Lane

changing going on, sooner or later there's going to be a Fender bender, and that happens in our solar system as well.

It's a busy place out there in the asteroid belt.

Asteroids will run into each other at many miles per second relative speeds.

And when that happens, the sparks fly.

If you started with two asteroids and they collided, suddenly you'd have ten asteroids.

Those ten asteroids are now going to collide again and now you have a hundred asteroids.

Those asteroids will collide and now you have a thousand, a million, a billion possible impactors for the Earth.

But this isn't just a numbers game.

Even though any one of the millions of asteroids could result in a major impact,

they're not identical.

This means each one presents a different type of threat.

Its speed, size, and distance from the Earth help dictate the degree of danger.

The more we can really understand about an asteroid, the better prepared we are to be able to defend against it.

This is definitely a case of know thy enemy.

We need to know something about the planet.

We need to know the properties of these objects.

If we have any hope of moving a threatening one out of our path one day.

But scientists are realizing that an asteroid's composition could be the deadliest factor.

Knowing what asteroids are made of can help us find chinks in their armor.

To do so, Marina Brozovic from the Center for Near-Earth Object Studies uses a

technology developed during World War II, radar.

Planetary radar is really like a big cousin of airport radar.

And so the same way like the airport radar is tracking the airplanes, we are tracking

asteroids that are, you know, hundreds of thousands, sometimes even millions of kilometers away.

Another thing that radars do is they tell us about how this asteroid looks like.

You want to know what's their size, what's their shape, what's their chemical composition.

Considering the detail that we see on the surface, short of sending a spacecraft,

you cannot achieve that.