If the speed at which light waves propagate in vacuum is independent both of the motion of the wave source and of the inertial frame of reference of the observer, why isn't the direction? Shouldn't the light travel directly upward from the point of emission and not diagonally, following the rocket? I was under the impression that "time" doesn't exist... Isn't it just something we created to measure the succession of events? Past and future exist only in our minds, the only thing that actually exists is the present, the now, and that is true simultaneously anywhere in the Universe. If we decide that one second is one 86400th of Earth's rotation on its axis at current speed, isn't that measure absolute and unchangeable? How can a rocket slow it down? How does speed slow down the oscillation of the atoms, cellular reproduction and decay (and everything else)? And even if it does, does it necessarily mean that "time" has slowed down? If "time" did slow down, shouldn't everything be affected, including light? Thanks for the clarifications!