Right, I’ve always thought of time as a constant, I don’t understand how light has anything to do with it.
I travel at the speed of light / or at a relativistic speed, I come back, I haven’t aged, yet Earth has. This is what I don’t understand. A good example would be “Forever War” by Joe Haldeman. If you are familiar with sci-fi.
Ernst Mach (same Mach) critized Newton’s second law of motion as a trivial definition of time.
Einstein showed that how you experience time, as measured by events, depends on your particular frame of reference. The notion that time is some natural force flowing continually and uniformly for all observers is not supported by facts. What is truly remarkable is that time measured quantum electrodynamically by atomic clocks appears to be identical (to a least one part in 10 to the 9) with graviationally determined time as measured by the orbits of planets.
“I travel at the speed of light / or at a relativistic speed, I come back, I haven’t aged, yet Earth has. This is what I don’t understand.”
I too, have problems with that. Much because the speeds are relative. Me in a space craft is traveling at light speed relative to what? Apparently relative to the earth. So, from my point of view, I can think of myself as fixed in space, and the earth is moving away from me at relativistic speed. So observers both on the earth and on my space craft can think of themselves as stationary while the other is moving relative to their fixed position. When I land on earth, who is to say I am not the old man, and the earthlings are the young ones?