Einstein’s Theory of Relativity

March 20, 1916: Albert Einstein published his theory of relativity in a scientific journal called Annalen der Physik.

Einstein’s “Zur Elektrodynamik bewegter Körper” (“On the Electrodynamics of Moving Bodies”) was received on June 30, 1905 and published September 26th of that same year. It reconciles Maxwell’s equations for electricity and magnetism with the laws of mechanics, by introducing major changes to mechanics close to the speed of light. This later became known as Einstein’s special theory of relativity.

Consequences of this include the time-space frame of a moving body appearing to slow down and contract (in the direction of motion) when measured in the frame of the observer. This paper also argued that the idea of a luminiferous aether—one of the leading theoretical entities in physics at the time—was superfluous.

In his paper on mass-energy equivalence, Einstein produced E = mc2 from his special relativity equations.

Einstein used the formula

$E_{kin}=mc^2\left(\frac1{\sqrt{1-\frac{v^2} {c^2}}}-1\right)$

for the kinetic energy of an electron. In elaboration of this he published a paper (received September 27, November 1905), in which Einstein showed that when a material body lost energy (either radiation or heat) of amount E, its mass decreased by the amount E /c2. This led to the famous mass-energy equivalence formula: E = mc2. Einstein considered the equivalency equation to be of paramount importance because it showed that a massive particle possesses an energy, the “rest energy”, distinct from its classical kinetic and potential energies.  It was Einstein who was the first to: (a) ascribe this relation to all forms of energy, and (b) understand the connection of Mass-energy equivalence with the relativity principle.

Einstein’s 1905 work on relativity remained controversial for many years, but was accepted by leading physicists, starting with Max Planck.

There are philatelic examples of the equation E = mc² from many different countries, some of which include a portrait of Albert Einstein. Here a just a few examples:

Israel – issue of 1956:

Germany – 100th anniversary issue of 2005:

Serbia – issue of 2005:

India – issue of 2005:

France – issue of 2005:

Ireland – issue of 2005: