Staircase viewed top-down to reveal Fibonacci spiral.

物理学为何是美?

纽约剑桥—十九世纪物理学家赫兹曾经描述道,他觉得构成电磁学基础的麦克斯韦方程组“拥有独立存在和自己的智能,它们甚至比其他发现者……都跟聪明,我们从它们身上得到的比我们最初投入它们身上的更多。”此后不久,爱因斯坦将玻尔的原子模型称为“思想界最高的音乐形式。”更晚近一些,已故诺贝尔物理学奖获得者费曼这样描述他所发现的物理学新定律:“你可以从它的美和简单中认识真理。”类似的感觉在现代物理学家中间无处不在。

想当然永远无法创造出能用的iPhone、冥王星照片和原子弹。被总结为一小撮数学上精确的定律的物理学毫无争议是有效的。但许多“有效”的东西并没有激起类似于对自然基本定律的崇拜的情感。

物理学定律的美首先植根于它们的对称性(symmetry)——这里意味着不变之变的可能性——一个精确的,但几乎是神秘的概念。正如圆可以绕其圆心旋转任意角度,让圆上所有的点改变位置而不改变圆本身的形状,对称定律适用于变化的情况而不必作出变化或失去有效性。比如,狭义相对论认为,当我们从匀速运动的平台看世界时,物理学基本定律不会发生改变。类似地,所谓的时间平移对称性描述了物理学定律在时间上的一致性:就算天荒地老,定律依然不变。

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