来自《耶鲁大学开放课程：基础物理 第12集 第12集》

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  you just cannot tell.
  而你就是无法分别
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  That's the word "Relative."
  这就是 "相对论" 的世界
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  So far-- I didn't tell you -- if you have only one train,
  我要补充一点 如果你只有一辆火车
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  what I told you earlier,
  就像之前那样
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  is that uniform velocity
  就是匀速运动
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  does not leave its imprint on anything you can measure.
  不会带来任何可观测效应
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  If you look outside,
  如果你向外看
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  of course you can see the motion of the other train,
  当然你能看到另一辆车相对你运动
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  but you still cannot tell who is moving.
  但你仍然无法知道究竟是谁在动
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  You cannot distinguish between different possibilities.
  你无法区分各种可能的情况
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  So, you have every right to insist that you are not moving
  你有足够的理由说自己没有动
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  and the other train is moving the opposite way.
  而是另一辆车向着相反的方向运动