Noether's theorem
Noether's theorem, proved in 1918, states that every continuous symmetry of a physical system corresponds to a conserved quantity. Because the laws of physics do not change from one moment to the next, energy is conserved. Because they do not change from one place to another, momentum is conserved. Because they do not change when you rotate your apparatus, angular momentum is conserved. The theorem turned conservation laws from separate empirical findings into consequences of a single structural fact about the laws themselves.
Why it matters
It links the two most useful organising ideas in physics, symmetry and conservation, and it is the reason physicists look for a symmetry whenever they find something that stays constant.
Where it comes up
Read about Noether's theorem on Wikipedia
Sources
- Noether's theorem English Wikipedia
- Symmetry and Symmetry Breaking Stanford Encyclopedia of Philosophy
- Emmy Noether Britannica
