三年级英语作文一次有趣的科学实验

　　【一】
　　In ancient times, many people believed the earth was a flat disc. Well over 2,000 years ago; the ancient Greek philosophers were able to put forward two good arguments proving that it was not. Direct observations of heavenly bodies were the basis of both these arguments. First, the Greeks knew that during eclipses of the moon the earth was between the sun and the moon, and they saw that during these eclipses, the earth's shadow on the moon was always round, they realized that this could be true only if the earth was spherical, If the earth was a flat disc, then its shadow during eclipses would not be a perfect circle; it would be stretched out into a long ellipse. The second argument was based on what the Greeks saw during their travels. They noticed that the North Star, or Polaris, appeared lower in the sky when they traveled south, in the more northerly regions, the North Star appeared to them to be much higher in the sky. By the way, it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth, a figure recorded in ancient documents says 400.000 stadium, that's the plural of the world stadium. Today, it's not known exactly what length one stadium represents, but let's say it was about 200 meters, the length of many athletic stadiums. This would make the Greeks estimate about twice the figure accepted today, a very good estimate for those writing so long before even the first telescope was invented.
　　【二】
　　上科学课之前，老师让我们带熟鸡蛋、太空泥。我一直在纳闷，这些到底是干什么用的呢?今天谜底终于解开了。
　　上课了，老师让我们两人一组，每组准备一盆水，然后老师说：‘咱们要把浮在水上的东西沉下去，那沉下去的东西浮上来。“我首先把鸡蛋放入水中，发现鸡蛋是沉下去的.，怎么样才能把鸡蛋浮上来呢?我的问题又来了，不一会，我把鸡蛋用手浮到水面上，一松手，鸡蛋就沉下去了。我不放弃，又想把太空泥裹在鸡蛋上会怎么样呢?我二话不说，立刻把太空泥裹在鸡蛋上，放入水中，鸡蛋就浮上来了，我的脸上露出了微笑，心里想吃了蜜一样甜。接着，我又把太空泥放入水中，太空泥是浮起来的，我想把一点重物加在太空泥里，会怎么样呢?我开始跃跃欲试，我一边做，一边嘴里说：”先加一点重物，再放入水中。“不一会儿，太空泥就沉下去了，我的实验又获得了成功。我高兴极了，科学实验真的太有趣了。