Where are the magnetic monopoles? String theory predicts that a working theory of quantum gravity has particles of all possible charges, including magnetic ones. This is what the 𝘊𝘰𝘮𝘱𝘭𝘦𝘵𝘦𝘯𝘦𝘴𝘴 𝘊𝘰𝘯𝘫𝘦𝘤𝘵𝘶𝘳𝘦 demands. We don’t know any rules that would forbid such a magnetic monopole. But where are they?
