“Mass and energy are both different manifestations of the same thing, a somewhat unknown conception to the average mind. Furthermore, the equation E = mc², where energy equals mass, multiplied by the square of the speed of light, showed that very small amounts of mass can be converted into a very large amount of energy and vice versa. Mass and energy were in fact equivalent, according to the formula just quoted. This was demonstrated by Cockcroft and Walton in 1932, experimentally “.
