[thedoc]

Einstein's early "Thought Experiments" were about light and how we preceive it, in one case he was considering what light would look like if we could stop it. Later he came to the understanding that the speed of light was always the same no matter who measured it and where they were. If someone were traveling in a space ship toward a light source at half the speed of light and measured the light from that source as it passed the ship they would still measure it at the speed of light. And from this idea Einstein went on to develope his theory of Relativity, which has been verified.