https://en.wikipedia.org/wiki/Noether%27s_theorem#:~:text=Noether's%20theorem%20or%20Noether's%20first,has%20a%20corresponding%20conservation%20law.&text=In%20particular%2C%20dissipative%20systems%20with,have%20a%20corresponding%20conservation%20law.
Noether's theorem or Noether's first theorem states that every
differentiablesymmetry of the
actionof a physical system with conservative forces has a corresponding conservation law.
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As an illustration, if a physical system behaves the same regardless of how it is oriented in space, its Lagrangian is symmetric under continuous rotations: from this symmetry, Noether's theorem dictates that the angular momentum of the system be conserved, as a consequence of its laws of motion. The physical system itself need not be symmetric; a jagged asteroid tumbling in space conserves angular momentum despite its asymmetry. It is the laws of its motion that are symmetric.
As another example, if a physical process exhibits the same outcomes regardless of place or time, then its Lagrangian is symmetric under continuous translations in space and time respectively: by Noether's theorem, these symmetries account for the conservation laws of linear momentum and energy within this system, respectively.
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【 在 Sunyata 的大作中提到: 】
: 就是，noether怎么推出能量守恒动量守恒的
: 主要想过两天上课的时候给学生科普一下noether的事迹。
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