【英语时差8,16】地球为什么是圆的
时间：2019-01-22 作者：英语课 分类：英语时差8，16
英语课
Don: It's time once again for one of those Moments of Science that we like to call "Never Thought to Ask."Our never thought to ask question for the day is: Why is the earth round? Ya?l: Why is the earth round? I never thought to ask that.
D: Of course not!
Y: It just seems to be one of those things. The sun is round. The moon is round. The earth is round. What else would it be?
D: Why not a cube?
Y: A cube? No, that's silly.
D: Is it? Why?
Y: Because . . . because . . . (frustrated) . . . because really big things like to be round for some reason!
D: Exactly right. And that reason is gravity.
Y: Gravity?
D: Think of it this way. Suppose the earth were a cube. Then some points on its surface would be farther away from the center than others. The corners, for example, would be much farther out than the rest.
Y: I think I see where you're going. Since gravity works equally on everything, there would be a tendency to pull those uneven 1 places down. The surface would even itself out.
D: Right. And the only geometrical object in which every point on the surface is the same distance from the center is. . .?
Y: A sphere! . . . But wait a minute. I've seen pictures of asteroids 3 that have all sorts of crazy shapes. Why aren't they round?
D: Only because they aren't big enough for gravity to be a determining factor. If that asteroid 2 were to suddenly become as big as a moon, it would indeed rearrange itself gradually into a sphere.
Y: Well, I never . . . !
adj.不平坦的，不规则的，不均匀的
- The sidewalk is very uneven—be careful where you walk.这人行道凹凸不平—走路时请小心。
- The country was noted for its uneven distribution of land resources.这个国家以土地资源分布不均匀出名。
n.小行星；海盘车(动物)
- Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
- It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。