来自《耶鲁大学开放课程：基础物理 第7集 第7集》

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  then, in the second week, the area swept out is that.
  然后 在第二周 扫过的面积是这一部分
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  So, it's the area intercepted by the two radial vectors
  这个区域是由两个径向矢量
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  and the arc along which you move.
  和你移动的弧截取的
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  And Kepler said the rate at which the area is swept out --
  开普勒说面积被扫过的速率
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  let dA/dt be a shorthand for
  用 dA/dt 来作为一个简写
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  how much area is covered in a certain time --
  描述在一定时间内被覆盖的面积
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  so you take area swept out, divide by Δt,
  这样你把扫过的面积除以 Δt
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  and he said that's a constant.
  他说这个值是常量
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  And the third result is that, let me see,
  第三定律是这样的 让我想想
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  the square of the time it takes a planet to go around the Sun,
  行星绕太阳运行一周的时间的平方
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  divided by the cube of the orbit size,
  除以轨道半长轴的立方
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  is the same for all planets.
  这个比值对于所有行星是一样的