英语听力：探索发现 2014-06-13 BBC 地平线：陨石的真相-14

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If the asteroid¹ had been in a different part of its orbit, so it didn’t hit this year but it hit next year, it would have still hit us on February 15th. But instead of coming in over Russia, it would have come in over the UK and Ireland and would have entered the Earth’s atmosphere, in fact, entered the North Atlantic Ocean. 

 

In order for the meteorite² to strike anywhere near Britain, our paths through space would have had to be fundamentally different. So we know where asteroids³ come from and the forces that shape their date with destiny. But what exactly happens next? The moment that a meteor strikes? And what determines just how devastating⁴ that strike will be?

 

When the Chelyabinsk meteor reached our atmosphere, it was travelling at more than 65,000 kilometres per hour and measured more than 15 metres across. Apart from some unconfirmed reports of craters⁵ at the bottom of Lake Chebarkul, there’s surprisingly few signs of an impact. Little of the 7,000 tonnes of space rock that entered the atmosphere have been recovered. Perhaps 300 fragments. And yet, the effects were felt over 3,000 square kilometres. 

 

The question is how can apparently⁶ so little do so much harm? There’s a clue from the last time Earth experienced a meteor strike on this scale. 

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