# An Analysis of the Phenomenon of Electromagnetic Energy in Albert Einsteins Papers

Albert Einsteinthe 1905 papers: In the first of three seminal papers published in 1905, Einsteinexamined the phenomenon discovered by Max Planck, according to whichelectromagnetic energy seemed to be emitted from radiating objects inquantities that were ultimately discrete. The energy of these quantities–theso-called light-quanta–was directly proportional to the frequency of theradiation. This circumstance was perplexing because classicalelectromagnetic theory, based on Maxwell’s equations and the laws ofthermodynamics, had assumed that electromagnetic energy consisted ofwaves propagating in a hypothetical, all-pervasive medium called theluminiferous ether, and that the waves could contain any amount of energyno matter how small. Einstein used Planck’s quantum hypothesis to describevisible electromagnetic radiation, or light. According to Einstein’s heuristicviewpoint, light could be imagined to consist of discrete bundles ofradiation. Einstein used this interpretation to explain the photoelectriceffect, by which certain metals emit electrons when illuminated by lightwith a given frequency. Einstein’s theory, and his subsequent elaboration ofit, formed the basis for much of quantum mechanics.

The second of Einstein’s 1905 papers proposed what is today called thespecial theory of relativity. At the time Einstein knew that, according toHendrik Antoon Lorentz’s theory of electrons, the mass of an electronincreased as the velocity of the electron approached the velocity of light.Einstein also knew that the electron theory, based on Maxwell’s equations,carried along with it the assumption of a luminiferous ether, but thatattempts to detect the physical properties of the ether had not succeeded.Einstein realized that the equations describing the motion of an electron infact could describe the nonaccelerated motion of any particle or any suitablydefined rigid body. He based his new kinematics on a reinterpretation of theclassical principle of relativity–that the laws of physics had to have thesame form in any frame of reference. As a second fundamental hypothesis,Einstein assumed that the speed of light remained constant in all frames ofreference, as required by classical Maxwellian theory. Einstein abandonedthe hypothesis of the ether, for it played no role in his kinematics or in hisreinterpretation of Lorentz’s theory of electrons. As a consequence of histheory Einstein recovered the phenomenon of time dilatation, wherein time,analogous to length and mass, is a function of the velocity of a frame ofreference ( Fitzgerald-Lorentz contraction). Later in 1905, Einsteinelaborated how, in a certain manner of speaking, mass and energy wereequivalent.

Einstein was not the first to propose all the elements that wentinto the special theory of relativity; his contribution lies in having unifiedimportant parts of classical mechanics and Maxwellian electrodynamics. The third of Einstein’s seminal papers of 1905 concerned statisticalmechanics, a field of study that had been elaborated by, among others,Ludwig Boltzmann and Josiah Willard Gibbs. Unaware of Gibbs’ contributions, Einstein extended Boltzmann’s work and calculated theaverage trajectory of a microscopic particle buffeted by random collisionswith molecules in a fluid or in a gas. Einstein observed that his calculationscould account for brownian motion, the apparently erratic movement ofpollen in fluids, which had been noted by the British botanist Robert Brown.Einstein’s paper provided convincing evidence for the physical existence ofatom-sized molecules, which had already received much theoreticaldiscussion. His results were independently discovered by the Polishphysicist Marian von Smoluchowski and later elaborated by the Frenchphysicist Jean Perrin. The General Theory of Relativity After 1905, Einstein continued working in all three of the above areas.

Hemade important contributions to the quantum theory, but increasingly hesought to extend the special theory of relativity to phenomena involvingacceleration. The key to an elaboration emerged in 1907 with the principleof equivalence, in which gravitational acceleration was held a prioriindistinguishable from acceleration caused by mechanical forces;gravitational mass was therefore identical with inertial mass. Einsteinelevated this identity, which is implicit in the work of Isaac Newton, to aguiding principle in his attempts to explain both electromagnetic andgravitational acceleration according to one set of physical laws. In 1907 heproposed that if mass were equivalent to energy, then the principle ofequivalence required that gravitational mass would interact with theapparent mass of electromagnetic radiation, which includes light. By 1911,Einstein was able to make preliminary predictions about how a ray of lightfrom a distant star, passing near the Sun, would appear to be attracted, orbent slightly, in the direction of the Sun’s mass. At the same time, lightradiated from the Sun would interact with the Sun’s mass, resulting in aslight change toward the infrared end of the Sun’s optical spectrum.

At thisjuncture Einstein also knew that any new theory of gravitation would haveto account for a small but persistent anomaly in the perihelion motion of theplanet Mercury. About 1912, Einstein began a new phase of his gravitational research, withthe help of his mathematician friend Marcel Grossmann, by phrasing hiswork in terms of the tensor calculus of Tullio Levi-Civita and GregorioRicci-Curbastro. The tensor calculus greatly facilitated calculations infour-dimensional space-time, a notion that Einstein had obtained fromHermann Minkowski’s 1907 mathematical elaboration of Einstein’s ownspecial theory of relativity. Einstein called his new work the general theoryof relativity. After a number of false starts, he published (late 1915) thedefinitive form of the general theory. In it the gravitational field equationswere covariant; that is, similar to Maxwell’s equations, the field equationstook the same form in all equivalent frames of reference. To their advantagefrom the beginning, the covariant field equations gave the observedperihelion motion of the planet Mercury. In its original form, Einstein’sgeneral relativity has been verified numerous times in the past 60 years,especially during solar-eclipse expeditions when Einstein’s light-deflectionprediction could be tested.