来自《耶鲁大学开放课程：基础物理 第15集 第15集》

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  A, you'll have one part that looks like time,
  矢量 A 一个部分看起来像时间
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  and one part that looks like an ordinary vector.
  而另一部分就像一个普通矢量
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  And B, is another four-vector.
  B 是另一个四矢量
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  It's got a part that looks time
  它也有类时部分
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  and another part that looks like an ordinary vector.
  和类矢量部分
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  It's a union up of former vector with a former scalar.
  将前矢量和前标量集合起来
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  And they will transform under Lorentz transformation
  它们的洛伦兹变换规则
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  just like x0 and t.
  和 x0 和 t 一样
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  But the following quantity A dot B,
  但 A 与 B 的点积
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  which is A0·B0 minus the usual dot product of the spatial components,
  即 A0·B0 减去空间分矢量的点积
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  is invariant.
  是不变的
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  That means all people will agree on this quantity.
  这意味着所有人都会得到相同的值