e=mc²

The equation showed that mass and energy were related and that one could, in theory, be transformed into the other. But because the speed of light squared is such a huge number, it meant that even a small amount of mass could potentially be converted into a huge amount of energy. Ever since the discovery of radioactivity in the late 19th century, scientists had realised that the atomic nucleus could contain a large amount of energy. Einstein’s revolutionary equation showed them, for the first time, just how much there was.