Einstein's equation

Without Einstein's equation research about the splitting of the atomic nucleus could not have evolved the way it did. Although there was a notion that mass contained an inherent energy the exact relationship between the two was not clear.

In 1905 Einstein proved that energy and matter are linked in the most famous relationship in physics: E=mc². (The energy content of a body is equal to the mass of the body times the speed of light squared). This equation predicted an evolution of energy roughly a million times more efficient than that obtained by ordinary physiochemical means.

This allowed a precise calculation of how much energy was - let's say - contained in a square inch of iron, or plutonium.

Furthermore, the mystery of why a star, or the sun, could burn brightly for billions of years could be explained by estimating the mass of the sun and then calculating the potential energy that could be released, namely the mass of the sun (or more precisely certain elements of the sun) multiplied by the square of the speed of light.