Maxwell's equations imply that all electromagnetic fields in vacuum travel at the speed of light . Thus no electromagnetic phenomena or signals can travel faster than light. Moreover, in all quantum field theories, phenomena connecting massive particles must occur inside the light cone, meaning that no particles or signals can travel faster than light. It can therefore be surmised that is a universal "speed limit" for material particles. Or, at the very least, this can be stated as an additional postulate in the special theory of relativity. (This doesn't apply in general relativity, where one could, in concept construct spacetimes allowing particles to travel faster than light. For example, the Alcubierre drive, a speculative although valid solution of Einstein's field equations. And science fiction is replete with "warp drives," which enable rocket ships to routinely travel faster than light.)