英语听力：探索发现 2014-06-08 BBC 地平线：陨石的真相-12

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The likelihood is that it was thrown out of its regular orbit by either one or a combination of the known causes—collision, the Yarkovsky effect, Jupiter’s gravity. It continued its new orbit for hundreds, thousands, even millions of years before meeting its fateful end.

 

We can even begin to trace the exact path that the Chelyabinsk meteor took on its collision course with Earth. Within the 16 seconds of action are all the clues we need. Now, from just one vantage point it’s not clear exactly how far up it is or how far away it is. But that’s what we get from looking at other vantage points. So here we are, again, at a different angle. The object is coming in, almost out of the Sun, there, and by combining this video clip with the other video clips, what we can do is trigonometry. Basically, you can figure out how high up the object was and how far away it was. And if you catch the object early enough, then you actually know where it was in the atmosphere the first time you saw it. So you are kind of triangulating to get that fixed³ position and it changes over time. 

 

So you get the trajectory⁴?

 

That’s right.

 

In the first part of the trajectory, what you’ve got there is a path that is relatively⁵ unaffected by the Earth’s atmosphere. So we can use that part of the video footage to track back and figure out where this object came from in the solar system. I love watching this because I now know where it is going to come and you see it just hitting the edge of the atmosphere. It’s going to be … just … Come on, come on…

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