grand unified theories
Grand unified theories (GUTs), or GUT for short, is also called the principle of all things. Since there are only four interaction forces between microscopic particles, there are gravitation, electromagnetic force, strong interaction force, and weak interaction force. In theory, all phenomena in the universe can be explained by these four forces. By further studying the connection and unification of the four acting forces, finding a theory or model that can unify the four interaction forces is called the grand unified theory.