英语听力：探索发现 2014-06-25 BBC 地平线：陨石的真相-19

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This is NASA’s Vertical² Gun Range. It was built to study how impacts affected³ the moon as the astronauts prepared to make the first lunar landing. We are armed, gated and reset⁴. Today, Professor Pete Schultz uses it to model precisely⁵ the dynamics⁶ of an asteroid⁷ impact. 

 

We know that these asteroid impacts are bad but you want to understand really how bad. 

 

Pete uses the NASA gun to fire projectiles⁸ at very high speed to simulate an asteroid hitting the Earth. 

 

So for this experiment we’re going to fire this tiny quarter-inch aluminium⁹ sphere at very high speeds up to around five kilometres per second. And then we will see what type of crater¹⁰ it produces. The target it will hit is made of sand. So we use sand because it records the shock affects very clearly. Outside of the impact chamber¹¹ are super high-speed cameras that can film at up to 1,000,000 frames per second, capturing every detail of the impact and the aftermath. Ok, lights out. Everything good?

 

Yeah.

 

Ok, we’re out of here. 

 

We have high voltage, the paddle is in, the warning lights, and rolling.

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