Whose equation is E equals mc squared?

The famous equation E equals mc squared was derived by Albert Einstein in 1905, as part of his special theory of relativity. It expresses that mass and energy are two forms of the same thing: a small amount of mass can be converted into an enormous amount of energy, because the speed of light squared is such a huge number. This principle explains how the Sun and stars generate energy by converting mass in nuclear fusion, and it underlies both nuclear power and nuclear weapons. The year 1905 was so productive for Einstein — with papers on relativity, the photoelectric effect and Brownian motion — that it is called his miracle year.