Albert Einstein (1879–1955) was a renowned theoretical physicist of the 20th century, best known for his special and general theories of relativity. He also made important contributions to statistical mechanics, especially by his treatment of Brownian motion, his resolution of the paradox of specific heats, and his connection of fluctuations and dissipation. Despite his reservations about its interpretation, Einstein also made seminal contributions to quantum mechanics and, indirectly, quantum field theory, primarily through his theoretical studies of the photon.
Einstein's writings, including his scientific publications, have been digitized and released on the Internet with English translations by a consortium of the Hebrew University of Jerusalem, Princeton University Press, and the California Institute of Technology, called the Einstein Papers Project.
Einstein's scientific publications are listed below in four tables: journal articles, book chapters, books and authorized translations. Each publication is indexed in the first column by its number in Schilpp's bibliography in the book Albert Einstein: Philosopher–Scientist (pp. 694–730), which Schilpp edited, and by its article number in Einstein's Collected Papers. Complete references for these two bibliographies may be found below in the Bibliography section. The Schilpp numbers are used for cross-referencing in the Notes (the final column of each table), since they cover a greater time period of Einstein's life at present. The English translations of titles are generally taken from the published volumes of the Collected Papers. For some publications, however, such official translations are not available; unofficial translations are indicated with a § superscript. Collaborative works by Einstein are highlighted in lavender, with the co-authors provided in the final column of the table.
There were also five volumes of Einstein's Collected Papers (volumes 1, 5, 8–10) that are devoted to his correspondence, much of which is concerned with scientific questions, but were never prepared for publication.
Chronology and major themes
The following chronology of Einstein's scientific discoveries provides a context for the publications listed below, and clarifies the major themes running through his work. Einstein's scientific career can be broadly divided into two periods. During the first period (from 1901 to 1933), Einstein published mainly in German-language journals, notably the Annalen der Physik, and, after becoming a professional physicist, worked at various German-speaking institutions in Europe, including the Prussian Academy of Sciences in Berlin. Following his permanent relocation to the United States in 1933, Einstein spent most of his time at the Institute for Advanced Study in Princeton, New Jersey, where he remained till his death in 1955. During the second period, Einstein submitted his papers in English to North American journals, such as the Physical Review.
Einstein first gained fame among physicists for the papers he submitted in 1905, his annus mirabilis or miraculous year in physics. His epochal contributions during this phase of his career stemmed from a single problem, the fluctuations of a delicately suspended mirror inside a radiation cavity. It led him to examine the nature of light, the statistical mechanics of fluctuations, and the electrodynamics of moving bodies. Many of Einstein's breakthroughs were made possible in part by his willingness to cross the borderlines of the disciplines of physics. More generally, one of Einstein's key motivations during his entire career was the search for a unified foundation for physics and the resolutions of inconsistencies.
The first period (1901–1933) From 1901 to 1904, Einstein submitted his first scientific papers, dealing with problems in thermodynamics and statistical mechanics. His first few papers convinced him of the limitations of a purely thermodynamic approach, whereupon he turned to statistical mechanics as a path towards a deeper understanding of thermodynamics, and established for himself a number of key results such as the canonical distribution, the equipartition of energy, and the statistical interpretations of entropy and temperature. He was only somewhat cognizant of the Lectures on Gas Theory by Ludwig Boltzmann and completely unaware of the Elementary Principles in Statistical Mechanics by Josiah Willard Gibbs. In 1905, Einstein proposed that the existence of light quanta—dubbed photons by chemist Gilbert Lewis in 1926—could explain the photoelectric effect.Pais, pp. 364–388, 402–422. He treated electromagnetic radiation as a gas and applied thermodynamic reasoning in his "heuristic" treatment, arguing that the energy of a photon is given by Planck's relation, , where is a new constant of nature (the Planck constant), and (nu) is the frequency of the photon. Whereas Max Planck had introduced the quantum hypothesis as merely a mathematical trick to obtain the correct description of blackbody radiation (Planck's law), Einstein considered it to be an aspect of physical reality. Robert Millikan set out to disprove the existence of quanta by experiment, but, to his surprise, found himself vindicating Einstein's explanation of the photoelectric effect using the quantum hypothesis, earning them both Nobel Prizes in Physics. In one of his 1905 calculations, Einstein also used, but did not justify or explain, the equation , where is the momentum of the photon and is the speed of light in vacuum. In 1909, Einstein employed his expertise in statistical mechanics to argue that the photon carries momentum as well as energy and that electromagnetic radiation must have both particle-like and wave-like properties if Planck's law of blackbody radiation holds; this was a forerunner of the principle of wave–particle duality.Pais, pp. 402–415. In a 1914 paper, Einstein showed that Planck's law of black-body radiation could be obtained by treating photons as if they were gas molecules. In 1905, to avoid getting into a dispute with his supervisor, Alfred Kleiner, Einstein selected a fairly conventional problem to tackle for his doctoral dissertation, namely, the determination of molecular dimensions using classical hydrodynamics.. Such calculations had already been done using gases. But Einstein was the first to successfully solve the problem using liquids. Einstein obtained a respectable estimate for the Avogadro constant, after incorporating better experimental data. Einstein received his doctorate in January 1906 from the University of Zurich. Einstein's doctoral dissertation remains one of his most cited papers ever, with applications in various engineering disciplines, such as concrete mixing and dairy production. In 1905, in the month following his dissertation, Einstein published his theory of Brownian motion, named after botanist Robert Brown, in terms of fluctuations in the number of molecular collisions with an object.Pais, pp. 93–100. He realized that while it was impossible to measure the mean velocity of a Brownian particle, he could make progress by focusing on the displacement. He showed that the mean displacement a grain of pollen suspended in a liquid traveled from its starting point was proportional to the square root of the time elapsed and determined the Avogadro constant in a new way, whence followed the Boltzmann constant. Einstein's work showed that Brownian motion, a kind of random walk, was related to the phenomenon of diffusion. A few weeks earlier, he had derived the Einstein relation for diffusion, which was the first example of the general fluctuation–dissipation theorem and gave an estimate of Avogadro's constant.Pais, pp. 90–92. Within months, Einstein's description of Brownian motion was experimentally verified by Henry Siedentopf. The strikingly visual nature of Einstein work assured scientists of the reality of atoms, and was a victory for statistical mechanics. Jean Perrin and his collaborators used Einstein's theoretical work on Brownian motion to experimentally determine Avogadro's number with greater accuracy. In 1905, Einstein developed his special theory of relativity, which resolved the inconsistency between Galilean relativity of motion and the observed constancy of the speed of light (a paradox of 19th-century physics),Pais, pp. 111–174. which, like the existence of light quanta, was another point of contention between Newtonian mechanics and Maxwellian electrodynamics. Special relativity is now considered a foundation of modern physics. Its counterintuitive predictions that moving clocks run more slowly, that moving objects are shortened in their direction of motion, and that the order of events is not absolute have been confirmed experimentally. With special relativity, Einstein rendered the notion of the luminiferous ether obsolete, the same conclusion as the Michelson–Morley experiment of 1887. In 1905, Einstein concluded that "The mass of a body is a measure of its energy content." In modern form, the equation he wrote down was , where is the energy of an object, is the mass of that object, and is the speed of light in vacuum. He suggested that "bodies whose energy contents is variable to a high degree, e.g. salts of radium" be used to test his new equation. Einstein's mass–energy equivalence was later verified by studying mass defect in atomic nuclei. The energy released in nuclear reactions—which is essential for nuclear power and nuclear weapons—can be estimated from such mass defects. Einstein subsequently gave many other derivations of this relation, fearing that he had not been rigorous enough. In 1907 and again in 1911, Einstein developed the first quantum theory of specific heats of a solid by generalizing Planck's relation.Pais, pp. 389–401. His theory resolved a paradox of 19th-century physics that specific heats were often smaller than could be explained by the equipartition of energy. His work was also the first to show that Planck's relation, , was a fundamental law of physics, and not merely special to blackbody radiation.Pais, p. 394. Experiments carried out to verify the predictions of Einstein's model of solids led to the development of new refrigeration technologies, low-temperature physics, and the discovery of the third law of thermodynamics by Walther Nernst. Einstein's formula for specific heats worked well at higher temperatures, reproducing the rule of Dulong and Petit, but faltered at extremely low temperatures. Einstein himself realized that this was because he had assumed that all atoms on a solid vibrated at the same frequency. Peter Debye relaxed this assumption in his model, as did Max Born and Theodore von Kármán in their periodic boundary condition, and were able to produce results that agreed better with experiments at low temperatures.