PDF《普特英语听力 免费学习英语》

普特英语听力 免费学习英语 更多下载 www.

putclub.com Create Create Create Create Your Your Your Your Own Own Own Own Moon Moon Moon Moon Craters! Craters! Craters! Craters! 制造属于你自己的月球陨石坑! 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 meteorites. The moon's surface is covered with literally 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 binoculars 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 soda 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 crater. Instead of just doing it at random, 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 meteorite. Higher-energy impacts make wider craters, with debris 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. Afterward, 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! 科学真正变得有趣的时刻就是当你亲自实践的时候, 那么今天, 让我们来一起制作月球陨石 坑吧! 陨石坑呈圆形, 它们是古代陨石撞击月球表面所留下的痕迹. 月球表面有着数以亿计的陨石 坑,有的陨石坑比地球上一个大城市还要大.仅用肉眼你就能看到月球表面较大的陨石坑, 如果使用望远镜的话,你可以看到更多陨石坑. 那么现在就让我们来制作自己的陨石坑. 找一个宽而平的平底锅, 类似我们平时烤饼干所用 的那种.最好到外面做这个实验,因为场面会变得十分狼藉.把面粉、小苏打或者是沙子倒 在底部,形成一个厚实平坦的表面,这看起来就像是没受到过撞击的月球. 现在,找个年轻人往这个月球表面上扔石头.当石头击中表面时,石头落下时的动能就会在 粉状的表面转化成撞击力,瞧!陨石坑就形成了.但是不要随意地从上往下扔石头,让一个 人先从两英尺的高度往下扔,然后再从四英尺的高度扔,接着是六英尺.你会发现陨石坑的 大小跟陨石的动能有关.能量越大,形成的陨石坑就越大.陨石坑中心受到撞击后会碎片四 溅,就像是射线一般.较小的陨石坑看起来很像小火山.从任何一个角度扔石头都会形成一 个椭圆形的陨石坑. 普特英语听力 免费学习英语 更多下载 www.putclub.com 以后,当月亮升起的时候,你再用望远镜看看它,就会对月球上的这些"麻子"有着更清晰的 认识.