What is “Symmetry” in Physics?

Question

I understand the concept of symmetry in geometry, but what do theoretical physicists mean when they speak of symmetry?

In: 15

Answer 1

There are lots of viewpoints one could take. One is that they represent invariances: it doesn’t matter when I do an experiment – I should always get the same result – because of time translational invariance. This is time translational symmetry. It doesn’t matter where I do an experiment because of space translational invariance – this is spatial symmetry.

The reason physicists like symmetry so much is that they represent conservation laws. Time translational symmetry implies conservation of energy. Space translational invariance implies conservation of momentum. And the belief is that all physical conservation laws have a corresponding symmetry.