小行星

We've all witnessed the beauty of a shooting star,but what would happen if 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  lame ,that theory was nothing. It turns out in my lifetime pelple found this crater,off Chicxulub,Mexico，This crater 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 diamete than the earth itself so the earth was surrounded by red hot rock 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 (boorn) air burst. See it 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 evey small.

If you're under 10 meters in diameter you hit the Earth's atmosphere.you burn up all Big Blue streak,green street white streak and then humans make wishes upon you （I don't know how efficacious these wishes are but people do that）.

Alright,so,if their asteroid starts to get bigger,Starts to get into the 25 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 country killers,city killers and country killers.

So,what we want to do is build a spaceraft 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.Any try to find all these asteroids,And then you find one,what do you do?Do you run in circies screaming,"AH"No,No,No,we've got to deflect it ,just a little just a tiny amount.

Asteroid might be going 10km/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/100,000tonnes.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 its 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 sapacecraft 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 amount 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 ans 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 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,Or 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 beacuse it's unlikely doesn't mean its 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)