英语听力：探索发现 2014-06-08 BBC 地平线：陨石的真相-12

 But there is a downside to Jupiter. It can also deflect¹ asteroids² into orbits that cross the Earth’s path. The Chelyabinsk meteor appears to be one of these typical Earth-crossing events. 

 

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…

1 deflect   

v.(使)偏斜，(使)偏离，(使)转向

参考例句：

• Never let a little problem deflect you.决不要因一点小问题就半途而废。
• They decided to deflect from the original plan.他们决定改变原计划。

2 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

3 fixed   

adj.固定的，不变的，准备好的；(计算机)固定的

参考例句：

• Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗？
• Once the aim is fixed,we should not change it arbitrarily.目标一旦确定，我们就不应该随意改变。

4 trajectory   

n.弹道，轨道

参考例句：

• It is not difficult to sketch the subsequent trajectory.很容易描绘出它们最终的轨迹。
• The path followed by a projectile is called its trajectory.抛物体所循的路径称为它的轨道。

5 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。