# Albert Einstein

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## Einstein, Albert

(īn`stīn), 1879–1955, American theoretical physicist, known for the formulation of the relativity theory, b. Ulm, Germany. He is recognized as one of the greatest physicists of all time.### Life

Einstein lived as a boy in Munich and Milan, continued his studies at the cantonal school at Aarau, Switzerland, and was graduated (1900) from the Federal Institute of Technology, Zürich. Later he became a Swiss citizen. He was examiner (1902–9) at the patent office, Bern. During this period he obtained his doctorate (1905) at the Univ. of Zürich, evolved the special theory of relativity**relativity,**

physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.**.....** Click the link for more information. , explained the photoelectric effect**photoelectric effect,**

emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory of electromagnetic radiation to explain it helped lead to the development of**.....** Click the link for more information. , and studied the motion of atoms, on which he based his explanation of Brownian movement**Brownian movement or motion,**

zigzag, irregular motion exhibited by minute particles of matter when suspended in a fluid.**.....** Click the link for more information. . In 1909 his work had already attracted attention among scientists, and he was offered an adjunct professorship at the Univ. of Zürich. He resigned that position in 1910 to become full professor at the German Univ., Prague, and in 1912 he accepted the chair of theoretical physics at the Federal Institute of Technology, Zürich.

By 1913 Einstein had won international fame and was invited by the Prussian Academy of Sciences to come to Berlin as titular professor of physics and as director of theoretical physics at the Kaiser Wilhelm Institute. He assumed these posts in 1914 and subsequently resumed his German citizenship. For his work in theoretical physics, notably on the photoelectric effect, he received the 1921 Nobel Prize in Physics. His property was confiscated (1934) by the Nazi government because he was Jewish, and he was deprived of his German citizenship. He had previously accepted (1933) a post at the Institute for Advanced Study, Princeton, which he held until his death in 1955. An ardent pacifist, Einstein was long active in the cause of world peace; however, in 1939, at the request of a group of scientists, he wrote to President Franklin Delano Roosevelt to stress the urgency of investigating the possible use of atomic energy in bombs. In 1940 he became an American citizen.

### Major Contributions to Science

#### The Special and General Theories of Relativity

Einstein's early work on the theory of relativity (1905) dealt only with systems or observers in uniform (unaccelerated) motion with respect to one another and is referred to as the special theory of relativity; among other results, it demonstrated that two observers moving at great speed with respect to each other will disagree about measurements of length and time intervals made in each other's systems, that the speed of light is the limiting speed of all bodies having mass, and that mass and energy are equivalent. In 1911 he asserted the equivalence of gravitation**gravitation,**

the attractive force existing between any two particles of matter. **The Law of Universal Gravitation**

Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called**.....** Click the link for more information. and inertia**inertia**

, in physics, the resistance of a body to any alteration in its state of motion, i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of motion. Inertia is a property common to all matter.**.....** Click the link for more information. , and in 1916 he completed his mathematical formulation of a general theory of relativity that included gravitation as a determiner of the curvature of a space-time continuum. He then began work on his unified field theory, which attempts to explain gravitation, electromagnetism, and subatomic phenomena in one set of laws; the successful development of such a unified theory, however, eluded Einstein.

#### Photons and the Quantum Theory

In addition to the theory of relativity, Einstein is also known for his contributions to the development of the quantum theory**quantum theory,**

modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.**.....** Click the link for more information. . He postulated (1905) light quanta (photons), upon which he based his explanation of the photoelectric effect, and he developed the quantum theory of specific heat. Although he was one of the leading figures in the development of quantum theory, Einstein regarded it as only a temporarily useful structure. He reserved his main efforts for his unified field theory, feeling that when it was completed the quantization of energy and charge would be found to be a consequence of it. Einstein wished his theories to have that simplicity and beauty which he thought fitting for an interpretation of the universe and which he did not find in quantum theory.

### Writings

Einstein's writings include *Relativity: The Special and the General Theory* (1918; tr. 1920, reissued 1947) and excerpts (most of them translated) from letters, articles, and addresses collected in *About Zionism* (1930), *The World as I See It* (1934), *Out of My Later Years* (1950), *Ideas and Opinions* (1954), and *Einstein on Peace* (ed. by Otto Nathan and Heinz Norden, 1960). Einstein's manuscripts and correspondence are presently at the Institute for Advanced Study, Princeton. The first volume of an edition of his collected works, under the editorship of John Stachel et al., appeared in 1987.

### Bibliography

See the Born-Einstein letters, ed. by M. Born (tr. 1971); biographies by R. W. Clark (1971, repr. 1991), B. Hoffmann (with H. Dukas, 1972, repr. 1989), J. Bernstein (1973, repr. 1997), A. Pais (1982), M. White and J. Gribbin (1995), D. Brian (1997), A. Folsing (1998), W. Isaacson (2007), and J. Neffe (2007); studies by P. A. Schilpp, ed. (1949, repr. 1973), M. Born (rev. ed. 1962), C. Lanczos (1965), A. J. Friedman and C. Donley (1989), D. Howard and J. Stachel (1989), A. Pais (1994), D. Overbye (2000), Z. Rosenkranz (2011), and P. Halpern (2015).

## Einstein, Albert

Born Mar. 14, 1879, in Ulm, Germany; died Apr. 18,1955, in Princeton, N.J., USA. Physicist; creator of the theory of relativity (*see*RELATIVITY, THEORY OF) and one of the creators of quantum theory and statistical mechanics.

Beginning at the age of 14, Einstein lived with his family in Switzerland. After graduating from the Zürich Polytechnic in 1900, he taught, first in Winterthur and then in Schaffhasen. In 1902 he was appointed examiner of patents in the federal patent office in Bern, where he worked until 1909. During these years, Einstein created the special theory of relativity and conducted studies in statistical mechanics, Brownian motion, theory of radiation, and other fields. His work gained renown, and in 1909, Einstein was appointed a professor at the University of Zürich. In 1911–12 he was a professor at the German University in Prague. In 1912, Einstein returned to Zürich, where he was appointed to a chair at the Zürich Polytechnic. In 1913 he was elected a member of the Prussian and Bavarian academies of sciences. In 1914 he moved to Berlin, where he was director of the physics institute and a professor at the University of Berlin. While in Berlin, Einstein completed the formulation of the general theory of relativity and further developed the quantum theory of radiation. For his works in theoretical physics and for the discovery of the laws of the photoelectric effect he was awarded a Nobel Prize in 1921.

In 1933, Einstein was forced to leave Germany, and subsequently he renounced his German citizenship in protest against fascism and left the academy. He then came to the USA, to Princeton, N.J., where he joined the faculty of the Institute for Advanced Study. Here he sought to work out the unified field theory and worked on problems in cosmology.

** Theory of relativity**. Einstein’s principal scientific achievement was the theory of relativity, which essentially is a general theory of space, time, and gravitation. The concepts of space and time that prevailed before Einstein had been formulated by I. Newton in the late 17th century and were not in apparent contradiction with facts until advances in physics led to the development of electrodynamics and in general to the study of motion at speeds close to the speed of light. The equations of electrodynamics (Maxwell’s equations) proved to be incompatible with the equations of Newtonian classical mechanics. The contradictions were further exacerbated after the Michelson experiment, the results of which could not be explained within the framework of classical physics.

The special theory of relativity, whose subject is the description of physical phenomena (including the propagation of light) in inertial frames of reference, was published by Einstein in 1905 in near-final form. One of its basic assumptions—the total equivalence of all inertial frames of reference—renders the concepts of absolute space and time of Newtonian physics meaningless. Only those conclusions that are not dependent on the rate of motion of the inertial frame of reference retain physical meaning. On the basis of these concepts, Einstein derived new laws of motion that reduce, in the case of small velocities, to Newton’s laws, and proposed a theory of optical phenomena in moving bodies. Turning to the ether hypothesis, he arrived at the conclusion that the description of an electromagnetic field requires no medium whatever and that theory turns out to be noncontradictory if, in addition to the principle of relativity, it is postulated that the speed of light is independent of the frame of reference. The detailed analysis of the concept of simultaneity and the processes of measurement of time and length intervals (which had also been conducted to some extent by H. Poincaré) demonstrated the physical need for the postulate formulated.

Also in 1905, Einstein published a paper in which he showed that the mass of a body *m* is proportional to its energy *E*, and in the following year he derived the famous equation *E* = *mc ^{2}*, where

*c*is the speed of light in a vacuum. The work of H. Minkowski on four-dimensional space-time was of major importance in helping complete the formulation of the special theory of relativity. The special theory of relativity has become an essential tool of physical research (for example, in nuclear physics and elementary particle physics), and its conclusions have been experimentally confirmed.

The special theory of relativity did not touch upon the phenomenon of gravitation and did not even raise the question of the nature of gravitation or the question of the equations of the gravitational field and the laws governing its propagation. Einstein noted the fundamental importance of the proportionality between the gravitational and inertial masses (the equivalence principle). Attempting to correlate the principle with the invariance of the four-dimensional interval, Einstein arrived at the idea that the geometry of space-time was dependent on matter, and after extensive research he derived (1915–16) the equations of the gravitational field (Einstein’s field equations). This work laid the foundations of the general theory of relativity (*see*GRAVITATION).

Einstein attempted to apply his equation to the study of the global properties of the universe. In a 1917 paper he showed that a relation between the density of matter and the radius of curvature of space-time can be obained from the theory’s principle of homogeneity. Confining himself to a static model of the universe, however, he was forced to include in the equation a negative pressure (the cosmological constant) to balance the attractive forces. The correct approach to the problem was found by A. A. Fridman (Friedman), who conceived the idea of an expanding universe. These studies gave rise to relativistic cosmology.

In 1916, Einstein predicted the existence of gravitational waves, solving the problem of the propagation of a gravitational perturbation. He thus completed the construction of the foundations of the general theory of relativity.

The general theory of relativity explained (1915) the anomalous behavior of the orbit of the planet Mercury, which could not be explained within the framework of Newtonian mechanics. It predicted the deflection of a light ray in the sun’s gravitational field (detected 1919–22) and a shift in the spectral lines of atoms located in a gravitational field (detected 1925). The experimental proof of the existence of these phenomena were brilliant confirmations of the general theory of relativity.

The development of the general theory of relativity in the works of Einstein and his colleagues was connected with the attempt to construct a unified field theory, in which the electromagnetic field is organically linked to the space-time metric, like the gravitational field. These attempts were unsuccessful, but interest in the problem has grown because of the construction of a relativistic quantum field theory (see QUANTUM FIELD THEORY).

** Quantum theory**. Einstein was instrumental in working out the foundations of quantum theory. He introduced the concept of the discrete structure of a radiation field and on the basis of this derived the laws of the photoelectric effect and explained luminescent and photochemical regularities. Einstein’s ideas regarding the quantum structure of light (published 1905) were in apparent contradiction with the wave nature of light, a contradiction that was resolved only after the creation of quantum mechanics (

*see*QUANTUM MECHANICS).

Successfully developing quantum theory, Einstein arrived in 1916 at the division of radiation processes into spontaneous and induced processes and introduced the Einstein coefficients *A* and *B* to define the probabilities of the processes. A consequence of Einstein’s reasoning was the statistical derivation of Planck’s radiation law from the condition of equilibrium between radiators and radiation (*see*PLANCICS RADIATION LAW). This work by Einstein forms the basis of modern quantum electronics (*see*QUANTUM ELECTRONICS).

Applying the same statistical approach to the vibrations of a crystal lattice rather than the emission of light, Einstein created the theory of the specific heat of solids (1907, 1911). In 1909 he derived the formula for the energy fluctuation in a radiation field, which confirmed his quantum theory of radiation and played an important part in the rise of fluctuation theory.

** Statistical mechanics**. Einstein’s first study in statistical mechanics (statistical physics) appeared in 1902, in which Einstein, unaware of J. W. Gibbs’ research, developed his own version of statistical mechanics, defining the probability of a state as the average over time. This view of the principal assumptions of statistical mechanics led Einstein to develop the theory of Brownian motion (published 1905), which became the basis for the theory of fluctuations.

In 1924, after becoming acquainted with S. Bose’s paper on the statistics of light quanta and perceiving its importance, Einstein published Bose’s paper along with his comments, in which he extended Bose’s theory to an ideal gas. Shortly after, Einstein’s work on the quantum theory of an ideal gas appeared. Bose-Einstein statistics arose in this manner (*see*BOSE-EINSTEIN STATISTICS).

** Other research**. Developing the theory of molecular mobility (1905) and investigating the reality of Ampàre currents, which give rise to magnetic moments, Einstein predicted, and with the Dutch physicist W. de Haas, experimentally detected the effects of a change in the mechanical moment of a body upon magnetization (the Einstein-de Haas effect).

** Importance of research**. Einstein’s scientific works were of major importance in the development of modern physics. The special theory of relativity and the quantum theory of radiation formed the foundation of quantum electrodynamics, quantum field theory, atomic and nuclear physics, elementary particle physics, quantum electronics, relativistic cosmology, and other branches of physics and astrophysics.

Einstein’s ideas proved to have great methodological consequence. They changed the mechanistic concepts of space and time that had prevailed in physics since Newton’s time and led to a new, materialist picture of the universe based on the profound, organic link between these concepts and matter and the motion of matter. Gravitation proved to be one manifestation of this link. Einstein’s ideas became the principal component of the modern theory of a dynamic, continuously expanding universe, which has made it possible to explain the extraordinarily broad range of phenomena observed.

Einstein’s discoveries were recognized by scientists throughout the world and earned him international prestige. Einstein was greatly disturbed by the sociopolitical events of the 1920’s to 1940’s and denounced fascism, war, and the use of nuclear weapons. He took part in the antiwar campaign in the early 1930’s. In 1940, Einstein signed a letter to the president of the United States calling attention to the danger of the appearance of nuclear weapons in fascist Germany, which was directly responsible for the emergence of nuclear research in the United States.

Einstein was a member of many scientific societies and academies throughout the world, including the Academy of Sciences of the USSR, of which he became an honorary member in 1926.

### WORKS

*Sobr. nauchnykh trudov*, vols. 1–4. Moscow, 1965–67. (Contains a bibliography.)

### REFERENCES

*Einshtein i sovremennaia fizika: Sb. pamiati A. Einshteina*. Moscow, 1956.

Seelig, C.

*Al’bert Einshtein*. Moscow, 1964. (Translated from German.)

Kuznetsov, B. G.

*Einshtein*, 3rd ed. Moscow, 1967.

IA. A. SMORODINSKII

## Einstein, Albert

(1879–1955) physicist; born in Ulm, Germany. He was an undistinguished student in Germany, but flourished at a high school near Zurich, Switzerland. He requested Swiss citizenship in 1901 and took a post with the Swiss patent office (1902–5). By the time he received his Ph.D. (1905), he had achieved world fame for his publications on Brownian movement of molecules, his photoelectric theory that light and other radiation can behave as both waves and particles, and for his revolutionary special theory of relativity, which related matter and energy in the famous equation, E = Mc^{2}. He developed his general theory of relativity (1915), which displaced Newtonian mechanics as the cornerstone of physics and introduced the concept of space-time. In 1921 he received the Nobel Prize, specifically for his ideas on photons and the photoelectric effect. He taught at several European institutions (1909–33), but after Hitler came to power, Einstein, a Jewish pacifist, emigrated in 1933 to the U.S.A. and accepted a post at the newly created Institute for Advanced Studies at Princeton, N.J. He became a U.S. citizen in 1940, and remained in Princeton after his retirement in 1945. Fear of Nazi expansion caused him to sign a letter to President Franklin Roosevelt in 1939 urging America to develop an atomic bomb. Einstein himself took no part in the bomb's construction and spent the remainder of his life promoting peace and humanitarian causes. He continued his unfulfilled search for a unified theory to combine quantum mechanics and relativity into one all-encompassing equation. A shy and gentle man, he was an accomplished violinist, and he made the world smirk when he once made an error while helping a young student with math homework.