How fast would you see this light traveling? Would they see the light beam moving at 1.5 times the speed of light? Albert Einstein predicted this in 1905, and it’s one of the two main postulates behind his theory of special relativity. Well, what he then showed is that if the speed of light is a universal constant, then time is relative. A Commonsense ExampleThe idea that everyone sees light traveling at the same speed seems like common sense.