BBC: Horizon: The Truth About Meteors| 英国广播公司:地平线:陨石的真相
2013年2月的一个清晨,车载相机和手机捕捉到了一连串火石穿越俄罗斯乌拉尔山脉上空。随后一阵剧烈的爆炸造成了六个城市中超过1500名居民伤亡和许多房屋毁坏。据NASA的资料,这块陨石有一幢房子那么大,重约10000吨。这是1908年俄罗斯通古斯大爆炸以来穿越地球大气层的最大物体。本部纪录片,Iain Stewart教授将带领大家一起探讨陨石和流星的区别,它们来自何方?它们有什么危险?它们在地球的历史进程中扮演什么角色?
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原文http://www.putclub.com/html/listening/guide/2004/0509/5357.html
由anyawinysabrina在 整理的原文:
Comparing the effects of an airburst with a ground strike, it seems the Chelyabinsk got away lightly. It’s estimated that the largest piece to hit the ground weighed 500 kilos, a fraction of the asteroid’s original mass of 7,000 tonnes.
Now if a piece of rock that big had hit that area of Russia, it would have produced a huge impact crater. Then that kinetic energy is then delivered into the ground and we see things like seismic shock. So, you get … people would feel earthquakes on the ground.
So the fact that it was an airburst actually limited the consequences for the people on the ground. So, yes, still quite dramatic, still, you know, obviously, causing injuries. But it could have been a lot worse, had it survived down to ground.
Ground strikes are amongst the most destructive natural hazards we know of. When viewed from space, Earth’s encounters with giant asteroids in its deep history are revealed. And there is evidence from our planet’s past of a truly devastating meteorite strike that decisively altered the course of life on Earth.
Today millions of years after the impact, the evidence for that crater is well hidden. This is a gateway to the cenotes, the unique cave system of Mexico’s Yucatan Peninsula. |