This paper first reveals the absurdity of relative theory and quantum theory, confirming the fatal error of Maxwell's equation, it creatively combines thermodynamics, fluid dynamics and electromagnetism to derive the field equation, which perfectly reveals the essence of electromagnetic and superconductivity. In addition, it creatively put forward the Attraction-Dominated principle, through which it perfectly explains the existence of gravity, the formation of matter and the forms of things. In the final analysis, all forces need the medium to transfer, there is no force beyond the medium. The different movement modes of the medium create a variety of forces, such as macroscopic force, microscopic force, mechanical force, electromagnetic force, heat, gravity, etc. By studying the behavior of the medium, we can find the answer and unify these forces, that is, everything is of the same origin