To most people it is not easy to explain why Einstein's theory eventually shook the whole scientific and intellectual world. But because of it, scientists never again regarded the world as they had before. Basically, the theory proposed, among other things, that the greatest speed possible in the universe is that of light; that mass appears to increase with speed; that the rate of a clock moving through space will decrease as its speed increases; and that energy and mass are equal and interchangeable. This latter claim, based on the formula <em>E=mc²</em> (energy equals mass times the square of the speed of light) was later proved by atomic fission, on which the atomic bomb is based. Later in life, when Einstein was asked to explain his law of relativity to a group of young students, he said: "When you sit with a nice girl for two hours, you think it's only a minute. But when you sit on a hot stove for a minute, you think it's two hours. That is relativity."