英语听力：探索发现 2014-06-20 BBC 地平线：陨石的真相-17（在线收听） |
Really, its’ a balance between the size of the object, its speed into the atmosphere and critically the altitude at which it explodes. Too high, if it’s too small and it explodes too high, the shockwave has little effect on the ground. If it’s quite low in the atmosphere, it’s a large object, then that shockwave is completely devastating. Actually seeing it in real life really brings home to you the energy that these things carry. And even though it exploded tens of kilometers, perhaps, up in the air, so quite a long way from the ground, the force of the explosion, the shockwave was able to damage buildings over a huge area and injure people and that was quite a shocking thing to see. The destructive power of an air blast is immense, but in a way the people of Chelyabinsk are lucky because out there in the cosmos is a different kind of asteroid, one that poses an even greater threat.
I’ve seen the evidence of what one of those can do, the damage that it leaves behind, and what you realize is the Earth’s own destructive forces, you know, the great earthquakes, the volcanic eruptions, seem trivial in comparison.
This is Barringer Crater, Arizona, the 50,000-year-old remnant of a massive meteorite impact. This place really gives you a sense of the destructive power of incoming meteorites. The blast here would have vaporized a city larger than London. But the lump of rock that did it measured barely 50 metr |
| 原文地址：http://www.tingroom.com/lesson/yytltsfx/2014/273539.html |