Although the theory of relativity and quantum mechanics explain certain phenomena of the universe relatively perfectly in their respective scopes, they are contradictory, cannot be correct, and neither can fundamentally explain the universe.
String theory, superstring theory and M theory are the new directions of current research.
String theory has the potential to become a grand unified theory of the universe capable of describing the fundamental interactions of all particles and, including gravity.
A basic idea of string theory is that the basic units of nature are not point-like particles such as electrons, photons, neutrinos, and quarks, but tiny, linear "strings" (the most basic unit of all matter is a small piece of "energy strings" that occupy two-dimensional space-time, and the only difference from particle types is the frequency difference in the vibrations of the strings).
Different vibrations and movements of the strings produce a variety of different elementary particles, and energy and matter can be transformed.
String theory mainly attempts to fuse and solve the contradictory problems of the two main physical theories, quantum mechanics and general relativity, thus becoming a grand unified theory of explaining the universe.
1. String theory: "String theory" now refers to Bose string theory that contains a 26-degree space.
2. Superstring theory: "Bose string theory" is called superstring theory after adding supersymmetry.
3.M Theory: In the 1990s, Edward Wiighton proposed an M theory with an 11-degree space, and proved that different versions of superstring theory at that time were actually the result of different limit setting conditions of M theory, and M theory was born. It combines five superstring theories with supergravity theories in eleven dimensions.
With the continuous revolution and development of M Theory, it is expected to become the great unified theory of the universe.