Albert Einstein: Equivalence of Mass and Energy

Albert Einstein

These pages explore Albert Einstein's life, work and philosophy. Albert Einstein was above all a  great physicist and mathematician. Because the ideas involved in his professional work were generally obscure especially in the first part of the 20th century, the public was not aware that many other physicists had been working on the same problems, nor were they in a position to understand the unique contribution of Albert Einstein in each case, which is never quite as it is explained in popular science books. 

Albert Einstein's work, like all scientific work, reflected advances of others and ideas that were in the air. He did not give proper references in many cases because he worked in a patent office, and had no access to proper libraries at the time he derived these theories. However, he was aware of the physical principles involved. This circumstance, together with the great publicity that was suddenly accorded to Physics beginning in 1920, to has given rise, among those who understand only popular science accounts, to three different types of misconceptions. First, many attribute to Albert Einstein ideas that really belonged to others, but were popularized when his own work became known. Second, others, having discovered this fact, insist that Einstein was a plagiarist. Third, many attribute to Einstein's scientific theories various philosophical, ethical or moral concepts, which they do not predict or relate to in any way, as Einstein would be the first to acknowledge, and in fact pointed out. 

Concepts and predictions that preceded Albert Einstein and accusations of plagiarism

These include the notion of relativity, first used by Galileo and, in the 19th century by Poincaré, thought experiments about synchronization of clocks, which Poincaré had also used, changes in mass and in size of objects at different velocities, which arise from the equations of Poincaré and Lorentz, and the equivalence of mass and energy, derived in 1902 by Poincaré, and by the Italian Olinto De Pretto, and in the speculations of the 19th century eccentric S. Toliver Preston. The recognition afforded to Einstein was not based on these particular conclusions, but on the ways in which he derived them and the elimination of the need to postulate a " luminiferous Aether," a construct on which all previous derivations depended. Preston, in particular, had expatiated on the properties of this Aether, which he decided was filled with a gas of particles moving at the speed of light, and for which he thought he could even derive the gas pressure.

Einstein did not invent the idea that heavy bodies bend light, either. It is a consequence of Newtonian physics. However, Einstein's General Theory of Relativity predicted twice the value of deflect that Newton's theory did.

A theory is not worth much if some of the different predictions of that theory are not true. Newton's greatness was not that he observed that bodies fall or that bullets move, but rather in developing a theory and a mathematical methodology for describing all these phenomena. Einstein's greatness, like that of most scientists including Newton, lies in producing theories that tied together the observed phenomena and predictions of others. Poincaré, Lorentz, de Pretto, Newton and even  Preston each had different pieces of the puzzle. Einstein put the puzzle together. Those who accuse Einstein of plagiarism must consider that his work was reviewed by his peers and accepted for publication. Notably, Max Planck was on the review board of the Annalen der Physik that published his papers, and was a big enthusiast of Einstein's theory of special relativity. As for Lorentz and Poincaré, had they thought that Einstein plagiarized their work, they would surely have protested! On the contrary, Lorentz was one of those who recommended Einstein for a Nobel prize.

The popular misconception about the paper before us, is that Einstein formulated the equation E= mc², demonstrating that mass could be turned into a large quantity of energy, and thereby created the basis of nuclear energy and the atomic bomb. Einstein's equation, given in this paper, is equivalent to   E= mc². This particular expression however, was apparently not used until the 1920s. Einstein himself did not believe that this relation could be used for practical purposes, though he did suggest using radium salts to test his theory. Becquerel had already found that radioactive elements lose weight when they decay, and in fact, nuclear physics proceeded for the most part in parallel to relativity theory and the equivalence of mass and energy played only a small part.

The scientific importance of Einstein's derivation of the equivalence of mass and energy was, apparently:

• The equivalence relation was derived from the  special theory of relativity and did not rely on the "luminiferous Aether."
• The equivalence was meant as a real world prediction, and not as a hypothetical case, as in the earlier paper of Poincaré.