The Empirical Status of Symmetries in Physics

Symmetries in physics are most commonly recognized and discussed in terms of their function in the mathematical formalism of the theories. Discussion of the observation of symmetries in nature is less common. This paper analyses the observation of particular symmetries such as Lorentz and gauge symmetries, distinguishing between direct observation of the symmetry itself and indirect evidence, the latter being the observation of some consequence of the symmetry. The result of the analysis is that globa symmetries such as Lorentz symmetry are, in an important sense, directly observed, while local symmetries such as gauge symmetry are not.