It is often said that one of the drawbacks of the standard model is that it has many free parameters. My question is two-fold: What exactly is a free parameter? My understanding is that the free parameters of a model/theory are the ones that cannot be predicted by the theory and need to be measu...

In multiple questions (e.g. A helpful proof in contracting the Christoffel symbol? or https://physics.stackexchange.com/a/101677/290999), I have now seen the following identity being used: $${\Gamma^\mu}_{\mu\lambda}=\frac{1}{2}g^{\mu\rho}(\partial_\mu g_{\lambda\rho}+\partial_\lambda g_{\mu\rho}...

Einstein successfully melded together space and time into one entity called spacetime in his General relativity theory and gave us further insight into how matter affects spacetime. John Wheeler said “Spacetime tells matter how to move and matter tells spacetime how to curve” but does this simple...

Why can a dipole not have two unequal charges separated by a distance? Is there any significance for the dipole being defined as electrically neutral?