Gravity or Magnetic Monopoles? You Cannot Have Both!

In this paper, we argue that gravity breaks the symmetry between electric and magnetic equations (without sources) within the Standard Model. As a result, the motivation for introducing magnetic monopoles disappears (without affecting charge quantization): magnetic monopole probably do not exist in the presence or gravity. It is consistent with the absence of observation of magnetic monopoles and resolves the magnetic monopole cosmology problem. This result could have serious implications for supersymmetry, supergravity, GUTs and ToEs, including in particular superstrings. Some of these implications, and possible ways forward, are discussed.