- Albert Einstein is one of history's most famous thinkers. His theory of relativity, E=mc2, remains one of the most significant equations in the history of physics. Before the publication of the theory of relativity, entities such as time and space and mass and energy were separate. As a result, the findings demonstrated in his famous theory helped develop a completely new way of conceptualizing the space-time relationship. The equation concludes that mass (m) and kinetic energy (E) are equal, since the speed of light (c2) is constant. According to this equation, mass can be changed into energy and vice versa. When mass transforms into energy, the result is nuclear energy. Similarly, energy can be changed into mass through a process known as particle collision. In addition to his theory of relativity, Albert Einstein also contributed to the development of quantum theory through his explanation of the photoelectric effect and postulation of light quanta.