来自《耶鲁大学开放课程：基础物理 第16集 第16集》

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  and pretty soon I'm telling the guy scanning my luggage,
  很快我会告诉那个正在扫描我行李的家伙说
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  "That's my code."
  "这就是我的密码"
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  And it's much better than any other code.
  而且它比其他任何密码都好
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  because I cannot reconstruct, say, my grandfather's name
  因为我并不能推出 比如说 我爷爷的名字
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  I may not get it right.
  我很可能得不到正确结果
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  I may not construct my house address, or my phone address.
  我也不能推出我的住址或者我的电话号码
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  This doesn't change.
  而它并不改变
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  I've been moving around all over the world,
  我曾在世界各地旅行
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  this is a very reliable number.
  这是个非常可靠的数字
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  Now, π is a good number,
  π 是一个非常好的数字
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  but rules for computing π are somewhat more difficult.
  但计算 π 的方法多少更复杂些
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  π also can be computed as an infinite series,
  π 也可以用无穷级数计算