Developing the theory of general relativity based on this postulate took Einstein another eight years. This curvature produces the effects that we call gravity. The speed of light in a vacuum is a universal constant. From these postulates, one finds that time flows at different rates for observers moving at different velocities. This remarkable prediction, and many other predictions of special relativity, are confirmed by numerous experiments.
Observers moving at different velocities see a different division between space and time.
If relative velocities are much smaller than c, the effects of relativity are very small.