Albert Einstein (redirected from Al Einstein)

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 (seeRELATIVITY, 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 = mc², 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 (seeGRAVITATION).

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 (seeQUANTUM 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 (seePLANCICS RADIATION LAW). This work by Einstein forms the basis of modern quantum electronics (seeQUANTUM 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 (seeBOSE-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