# This day in Technology History

Einstein paper outlines E=mc2, November 21, 1905

Suzanne Deffree -November 21, 2014

Albert Einstein’s paper “Does the Inertia of a Body Depend Upon Its Energy Content?” was published in the journal “Annalen der Physik” on November 21, 1905.

The paper revealed the relationship between energy and mass that would eventually lead to the mass-energy equivalence formula E = mc^{2} (energy equals mass times the velocity of light squared).

Einstein was far from being the first to propose a mass-energy relationship but he was the first scientist to propose the E = mc^{2} formula and the first to interpret mass-energy equivalence as a fundamental principle that follows from the relativistic symmetries of space and time.

The paper was one of Einstein’s four Annus Mirabilis papers (from Latin annus mīrābilis, “Extraordinary Year”). The papers were all published in the Annalen der Physik scientific journal in 1905.

In addition to “Does the Inertia of a Body Depend Upon Its Energy Content?” on the relationship between energy and mass, Einstein penned:

- “On a Heuristic Viewpoint Concerning the Production and Transformation of Light,” received March 18 and published June 9, which proposed the idea of energy quanta. Einstein was awarded the 1921 Nobel Prize in Physics for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect, which this paper contributed to.

- “On the Motion of Small Particles Suspended in a Stationary Liquid, as Required by the Molecular Kinetic Theory of Heat,” received May 11 and published July 18, which delineated a stochastic model of Brownian motion.

- “On the Electrodynamics of Moving Bodies,” received on June 30 and published September 26, and which reconciled 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.