英语听力：探索发现 2014-07-20 BBC 地平线：陨石的真相-30

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Because of that then, this thing and objects like this, if they come in at that particular direction, they’re always going to take us by surprise at the moment without current survey system. But even if we can spot an asteroid² heading towards us and in good time to prepare, what if anything can we do? 

 

There’re different options for deflecting⁴ asteroids⁵ and it is a bit sci-fi at the moment.

 

The idea of shooting it out of the sky with a nuclear weapon would really be a dreadful idea. I mean, it would just shower us with radioactive debris⁶, and it would just, you know, do more harm than good. What would be much better would be to simply push it, nudge it slightly off its course, so that it wasn’t then going to collide. So how do you gently nudge an asteroid? 

 

There’re lots of different techniques to push it. So, the one I love is called a mass driver. There’s an object, a machine which sits on the asteroid, sits there and throws off rocks. So it is accelerating rocks that way and that makes the asteroid gradually move in the opposite direction. You can paint one side of the asteroid white. That reflects the Sun and there’s this weird⁷ effect that makes the asteroid gradually drift across. 

 

We can launch a mission now which essentially⁸ can impact an asteroid and then deflect³ it, a bit like a billiard shot or a snooker shot. We just hit the asteroid extremely fast with a spacecraft. And that small impact really is sufficient to just alter its course so that it misses the Earth. 

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