From all of the literature that I have read, I’ve gathered that as a person travels faster, other people will perceive time more slowly. For example, if a person goes close to the speed of light and comes back to earth, everyone there will be much older than when the person left.
So lets say a person goes to the moon (or another set distance) and back at close to the speed of light. When he comes home, everyone there has aged a lot. How fast in mph was he really going? I’m confused.