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.
你也知道 行星撞地球可不是件小事,当我上二年级时 McGonigal女士告诉我们说,恐龙 古代的恐龙之所以灭绝,是因为他们的大脑太小，就像我的老上司一样
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.
俄罗斯车里雅宾斯克上空的爆炸,看到了吗，如果你是个小行星 以10km/s 或20km/s 的速度前进，你碰上地球的大气，大气就像水泥一样，你躲不过去，所以小行星只能在半空中爆炸.因此这些小行星得严肃对待，它们绝大多数都很小.
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.
但它们会放射出红外线辐射，所以你要怎么做？你是一个卫星，是个调查用的航天器，你跑到太阳后面在金星轨道附近四处张望，试图找到所有的这些行星，你找到了一个 肿么办 画着圈圈四处尖叫，不不不 我们得让它走偏一点 一点就行 只要一点点。
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.
行星可能以10km/s 的速度运行，我们要让它的速度改变2mm/s, 10千米就是10*1000米，也就是10,000米。一毫米是千分之一米，那么你在取出这一千分之一，所占比例就是1000*10,000 也就是一百万,你想改变总速度的一百万分之一.
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.
似乎不多 但如果你是那个撞向地球的万吨/十万吨的小行星。想要让速度改变一百万分之一的确需要很大的力。好的，那么怎么办？最简单的方法是弄一个火箭 要大大的一个。 飞到那里一头装进去，只不过这是在外太空 所以效果是这样的（静音）。
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？
好的 这会将它的速度改变一点点 现在各位看官注意，如果撞的不是岩石呢？如果那只是被原初引力聚焦在一起的一堆松垮岩石呢？如果你击中它们 它们就会分散开来 给你下场石头雨。好悲催的样子 那么怎么办呢？
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
我们让一艘硕大的宇宙飞船飞过去 让它靠近行星，靠近它 之后你（小行星）的和我（宇宙飞船）的相互引力会将行星拉近一点点 就那么一点点 或者到这边来 这么拉,这也可能有用 不过现在有个问题。
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.
我们需要大量的燃料 得准备数天 数星期 数月甚至数年的，如果它停止工作了 你没法跑到那修理它，好 那这么办 激光小密蜂怎么样？一群太阳能激光器射向行星的表面，就这么嗞嗞嗞地照上几天 几周 几个月甚至几年。一部分行星 一部分岩石会蒸发。
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,
从物体上抛出的东西和火箭燃料一样 都有动量，就像你站在滑板上用保龄球玩接球游戏一样，就像你做的那样，之后 这会致使小行星改变运行速度。
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.
另外你送去了一群这样的激光航天器，如果一个停止工作了 你还可以使用另一个，或者你可以让它们从不同角度切入，如果小行星的形状不规则（像这样）,你可以把表面烤到光滑，当出现一个坑或者有照射不足的地方时 你把激光关掉，你等着行星转一圈之后再把激光打开。
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.
你们看到了吗 事情不太可能发生并不意味着它不重要,你知道 即使它几千年才会发生一次，如果在我们观察时这事发生了 我会和孩子一样说“擦”,好的 我们不想让这事发生 我们要躲着它。
Asteroids are serious business,but they're exciting.（spaceship noise）Except we are in space so its (silence)
(航天器噪声）除了我们在太空时 它此时（无声）行星需要被认真对待 但是它们让我们兴奋，