This theory has a variety of surprising consequences that seem to violate common sense, but all have been experimentally verified. Special relativity overthrows Newtonian notions of absolute space and time by stating that distance and time depend on the observer, and that time and space are perceived differently, depending on the observer. It yields the equivalence of matter and energy, as expressed in the mass-energy equivalence formula E = mc˛, where c is the speed of light in a vacuum. Special relativity agrees with Newtonian mechanics in their common realm of applicability, in experiments in which all velocities are small compared to the speed of light. (wikipedia)