Based on the principle of constant speed of light and the principle of minimum energy, this paper innovatively proposes the principle of relative variation of light speed and constructs a theoretical system of vacuum dynamics. By revealing the spontaneous force dynamic mechanism induced by the light speed gradient, this theory provides an innovative dynamic interpretation framework for gravitational interaction and dark energy phenomena, making up for the deficiency of general relativity in the discussion of dynamic mechanisms. The core research results are as follows: 1. Spacetime-light speed covariance principle: Reveals the physical law that the rate of spacetime variation must be consistent with the rate of relative variation of light speed. 2. Dynamic mechanism of vacuum light speed gradient: It is proposed that the light speed gradient can cause spontaneous motion of objects, and the acceleration is the negative gradient of the square of the light speed, with the expression: ： . 3. Equivalence of gravitational acceleration: The gravitational acceleration derived from the vacuum dynamics theory is completely equivalent to that of general relativity. This supplements the dynamic mechanism for the geometric interpretation of "spacetime curvature is gravity". 4. Model of light speed gradient distribution in the universe: A gradient distribution model of light speed in the universe (higher in the inner region and lower in the outer region) is proposed. The essence of cosmic expansion is the spontaneous movement of celestial bodies toward regions with low light speed (i.e., low energy), and dark energy is essentially the internal energy released and converted into kinetic energy by celestial bodies in this process. This study also lays a theoretical foundation for the unification of gravitational field and electromagnetic field as well as the research on propellantless vacuum engines, and is of great significance for improving the basic theory of physics.
Li et al. (Mon,) studied this question.