Albert Einstein (1879-1955) developed the theories of special and general relativity. Special relativity, published in 1905, established that the laws of physics are the same in all inertial frames of reference and that the speed of light in a vacuum is constant. General relativity, published in 1915, introduced gravitation as a result of the curvature of spacetime caused by the uneven distribution of mass and energy. One of Einstein's most famous equations is E=mc2, which shows that mass and energy are equivalent and interconvertible.