Based on the principle of constant speed of light and the principle of minimum energy, this paper innovatively proposes the principle of relative change of light speed and constructs the theoretical system of vacuum dynamics. By revealing the spontaneous force dynamic mechanism caused 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 in the discussion of the dynamic mechanism in general relativity. The core research results are as follows: - Space-time-light speed covariance principle: It reveals the unified physical law that the ratio of space-time change to the relative change of light speed must be consistent.- Dynamic mechanism of vacuum light speed gradient: It is proposed that the light speed gradient can make objects produce spontaneous motion, and its acceleration is the negative gradient of the square of light speed: gₘ = -∇c².- The gravitational acceleration derived from the vacuum dynamics theory is completely equivalent to that of general relativity. Thus, it supplements the dynamic mechanism for the geometric interpretation of "space-time curvature is gravity".- A gradient distribution model of light speed in the universe is proposed, where the light speed is higher in the inner part and lower in the outer part: the essence of the cosmic expansion is the spontaneous movement of celestial bodies to the region with lower light speed (i.e., lower energy), and dark energy is essentially the internal energy released and converted into kinetic energy by celestial bodies in the process of cosmic expansion.
Li et al. (Mon,) studied this question.