英语听力：探索发现 2014-06-15 BBC 地平线：陨石的真相-15

 On June 30th, 1908, a huge explosion tore through the forest of Tunguska, Siberia. It was 20 years before the Russians mounted an expedition to the site. What they found astonished them. 60 million trees across an area the size of London had been leveled. Scientists thought it had been caused by a meteorite¹ strike. But then why was there no sign of any kind of impact crater²? The answer is that the devastation³ had to be caused by a meteor attack of a very particular kind.

 

Physicist⁴ Mark Boslough has been fascinated by how so much destruction can be caused without any apparent direct contact. The explosion at Tunguska was caused by an asteroid⁵ that entered the atmosphere, got close to the surface and exploded before it hit the ground. And that explosion created a blast wave with hurricane force winds that knocked trees over for thousands of square miles. Scientists call it an airburst, a massive explosion in the atmosphere rather than on the ground. As it enters the atmosphere at speeds of up to 24 kilometres per second, the air resistance decelerates the asteroid so fast (that) it breaks apart in a huge explosion. 

1 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

2 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

3 devastation   

n.毁坏；荒废；极度震惊或悲伤

参考例句：

• The bomb caused widespread devastation. 炸弹造成大面积破坏。
• There was devastation on every side. 到处都是破坏的创伤。 来自《简明英汉词典》

4 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

5 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。