But if physics is the same for everybody, then the speed of light (hereafter “C”) must be the same for everybody. A good way to explore the connection is a “light clock”. A light clock is a pair of mirrors, a fixed distance apart, that bounce a photon back and forth and *clicks* at every bounce. The lower the slower: Less commonly known, is that the lower you are in a gravity well, the slower time passes. So the acceleration that pushes you down in a rocket does all the same things that the acceleration due to gravity does.