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General relativity has been proven many times over to be correct. In my meager understanding of things, they are all premised on the fact that the speed of light is constant to all observers. I would like a greater understanding of this phenomena. All explainations i have seen thus far (laser beam bounce etc.) triumphantly show the end result and conveniently skip over the "innards". To help me understand the inner workings of light and time (gravity's another story) i have the following question.... if jack and jill are are the only objects in existance and jack accerates away his clock slows down. The only change in forces jack experiences are his own enertial changes and the effects of jills gravity. Assuming time is a measurement if atomic activity (is this a wrong assumption?), which of these two forces is slowing his clock?