According to the time dilation effect, the faster the moving speed, the slower the relative time of observing the coordinate system. Therefore, if an object can move at the speed of light, in the observer's view, time is stationary relative to the moving object.
Relativity is divided into special relativity and general relativity. The basic theories include: the constant speed of light in vacuum, the time expansion of moving objects, gravitational lens, the equivalence between acceleration and gravitational space curvature, and so on. The so-called theory of relativity actually only cancels the absolute coordinate system of Newton's motion system.