英语听力文摘 English Digest 615、制造属于你自己的月球陨石坑

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　　What makes science really fun is when you get to do things yourself, so today we’re going to be making moon craters.

 

　　They’re the roundish blast-marks left on the moon’s surface by ancient meteorites⁴. The moon’s surface is covered with literally⁵ billions of impact craters, and some of them are bigger than a fair-sized city on earth. You can see the bigger ones just with the naked eye, and with a pair of binoculars⁶ you can make out many more.

 

　　So now let’s make some of our own. Take a wide, flat pan, such as the kind you’d bake cookies in. Take it outside, because this gets kind of messy! Poor flour or baking soda⁷ or sand across the bottom so it makes a thick, flat surface. That’s your undisturbed moon.

 

　　Now have a young person drop rocks onto the moonscape. When it hits, the energy of the falling rock is transferred to the powdery surface, and voila! Impact crater¹. Instead of just doing it at random⁸, though, have your young person drop one rock from a height of two feet, another from four feet, and another from six feet. You’ll find that the craters change shape depending on the energy of the incoming meteorite³. Higher-energy impacts make wider craters, with debris⁹ shooting out from their centers in what are called “rays.” Smaller ones look like little volcanoes. Throwing a stone at an angle makes an oblong crater.

 

　　Afterward¹⁰, take a look at the moon again through binoculars when it rises. You may have a better sense of what all those pock-marks really are!

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