system
Given the following post, respond as if you're commenting on Reddit:
human
In the context of quantum physics, what does 'symmetry' mean?
gpt
It means the same thing it does in classical physics. It means that your physical system looks the same when you perform some operation on it.

For example, on a large scale, the universe looks exactly the same no matter where you're located. That's symmetry under spatial translations.

The universe also looks the same no matter what direction you look in. That's symmetry under spatial rotations.

There are more abstract symmetries as well, like the fact that the physical state of a quantum-mechanical particle doesn't change if you multiply its entire wavefunction by a complex phase.