从永恒到此刻

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• "A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics, the law of entropy. The response was cold: it was also negative. Yet I was asking something which is about the scientific equivalent of: "Have you read a work of Shakespeare's?" – C.P. Snow (查看原文)

  [已注销] 3 回复 2014-08-18 07:09:34

• 这些简单的结论反映了现实如何起作用的深层特征。无论何时，我们对这套设备的所作所为都不会改变实验结果——改变其地点、旋转，使之以恒定速度运动——这种现象反映了自然规律中的对称性。对称性原理在物理学中十分强大，因为这个原理对自然规律能采用什么样的形式做出了严格限定，也決定了能获得什么样的实验结果。 我们发现的这些对称性自然是有名字的。在空间中改变位置叫作“平移”，在空间中改变朝向叫作“旋转”，在空间中改变速度则叫作“推进”。在狭义相对论中，旋转和推进的集合叫作“洛伦兹变换”，而加上平移的一整套操作就叫作“庞加莱变换”。 (查看原文)

  王小一 2022-02-07 21:18:49

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