The equation developed by Albert Einstein, which is usually given as E = mc², showing that, when the energy of a body changes by an amount E (no matter what form the energy takes), the mass (m) of the body will change by an amount equal to E/c². The factor c squared, the speed of light in a vacuum (3 x 10 to the eighth power), may be regarded as the conversion factor relating units of mass and energy. The equation predicted the possibility of releasing enormous amounts of energy by the conversion of mass to energy. It is also called the Einstein equation.