an asteroid was on a collision course for earth?

Could we detect it ahead of time? And more importantly could we stop it? I believe

I have an answer, now you see, asteroid impacts

are serious business, when I was in second grade Ms. McGonigal told us

that the dinosaurs the ancient dinosaurs died out because they had small brains

may be like

my old boss. But even she knew that was kinda lamethat theory was

nothing.

It turns out in my lifetime people found this crater,

off Chicxulub mexico. This crator was so big, how big was it, it was so big

that an asteroid hit the earth (or impactors hit the earth).

Threw so much stuff into the Earth's sky it was bigger in diameter

than the earth itself so the earth was surrounded by red hot rock for weeks at

a time,

it cooked everything. And just the animals that lived in burrows and caves,

our ancestors lead to us so serious business you may recall Valentine's Day

2013?

Chelyabinsk Russia (boom) air burst.

See if you are an asteroid, and you are going 10 km /s or 20 km /s

And you hit the Earth's atmosphere, the atmosphere is like concrete.

you can't get out of the way so the asteroid just explodes in air burst.

So these asteroids are serious, most of them

are very small. If you're under 10 meters in diameter you hit the Earth's atmosphere you burn up all Big

Blue streak, green streak

white streak and then humans make wishes upon you.

(I don't know house efficacious those wishes are but people do that), alright

so,

if ther asteroid starts to get bigger, starts to get into the twenty-five meters and the

45 meters in diameter then you get Meteor Crater Arizona (wham) huge

thing.

That would be like a city killer, or a county killer.

And then when they get to be a 100 meters / 140 meters now you're into a country killer,

and then they get bigger than that and it's a continent killer, much bigger than that

and you're taking out

whole races of ancient species.

So, what if we found an asteroid that was headed our way, how would we find it?

How would we find an asteroid headed our way? That's a good question, well

you can use telescopes. Skilled people can point the cameras at the sky and

look for fast-moving objects.

Objects that are crossing the Earth's orbit, but we're missing perhaps a

hundred thousand

of these things, of these county killers, city killers and country killers.

So, what we want to do is build a spacecraft called The Sentinel,

and as we say "it's like looking for a charcoal briquette

in the dark", these things are hard to find. They are tiny compared to the vastness

of space.

But infrared light / heat bounces off them so what you will do -

you are a satellite, you are a surveying spacecraft,

you get your back to the Sun and look out

from about the orbit of Venus. And try to find

all these asteroids. And then you find one, what do you do? Do you run in circles

screaming?

"AH" No, No No, we've got to deflect it, just

a little, just a tiny amount. Asteroid might be going 10 km/s

we want to change its speed

about 2 mm/s.

So ten kilometers, that's ten times a thousand meters, that's 10,000 meters.

A millimeter that's a thousandth of

a meter so that you take the one over the thousand its a thousand times ten

thousand,

that's 10 million. You want to change its speed a 10 millionth

of its total. That's not very much,

but if you're an asteroid that comes in at

10,000 tons / 100,000 tonnes,

it does take quite a bit force to change it a 10 millionth of its speed.

Okay,

how do we do that? Well, the easiest way

is to get a rocket, just a big rocket, just go out there and

smack into it. Except as an outer space so it just goes (silence)

like that. Okay, that would change its speed a little, now notice everybody,

what if it's not just a rock? What if its a pile of rocks just

loosely held together by primordial gravity?

And so if you hit them they will just spread out and you will have a shower of

rocks.

That would be bad. So, how about this?

We will get a big space craft that is massive, a massive spacecraft will go out there

and just get nearer to the asteroid.

Just get near it, and then the mutual gravity

of the you the asteroid and me the spacecraft

will tug the asteroids just a little bit

just a tiny amounth or maybe get on the other side and tug

this way. That might work but here's the problem.

We need a huge amount of fuel, for days

and weeks and months and years.

And what if it stops working, you can't go out there and fix it. Okay,

how about this? The Laser Bees?

A swarm

of sunlight powered lasers,

that are zapping the surface of the asteroid,

for days, and weeks, and months,and years

ZAP ZAP ZAP, so some asteroids, some rock is vaporized

so the ejecta, or the stuff ejected has momentum

just like rocket fuel, just like just like standing on a skateboard and playing

catch with a bowling ball...

the way you do. And so it would then

cause the asteroid to change its speed. And so you send a swarm of these laser

spacecraft, so that

if one of them stops working you can use the other one. And you can

have them come in from all different angles. And what if the asteroid is

irregularly shaped (like this)

you could beam it when the thing is smooth

and then when there's a pit or an inefficient place to be beaming you turn

off,

you wait for the asteroid to turn, then you turn it back on. You see everybody,

just because it's unlikely, doesn't mean it's not a big deal.

You know if it only happens once every few thousand years, well if it happens

on my watch

it would as the kids say "suck". Okay, so we don't want that to happen, we want to

avoid that.

Asteroids are serious business, but they're exciting.

(Spaceship noise) Except we are in space so its (silence).

Got a burning question? Well be sure to subscribe asapscience, follow us

on Twitter and Facebook, that's what all the kids are doing.

And if it's an asteroid it may not be a burning question, it might be

an impacting question, or even

and ablating question.