Albert Einstein (14.03.1879-18.04.1955) was an outstanding theoretical physicist and one of the founders of modern physics. He was born in Ulm (now in the Federal Republic of Germany). At the age of fourteen he moved to Switzerland, where he graduated from the Zurich Polytechnic (1900). In 1902-08 he worked as an examiner at the patent office in Bern, in 1909 — 13 he was professor at the Zurich Polytechnic (in 1911 professor at the German University in Prague), and in 1914—33 professor at the University of Berlin and director of the Institute of Physics. After the Fascists came to power he was persecuted and forced to leave Germany. In 1933 he moved to the USA, where he worked at the Institute for Advanced Study in Princeton until the end of his life. He created the special and general theories of relativity, which radically changed ideas about space, time and matter. According to V. I. Lenin, he is one of the “great transformers of natural science”.
In 1905, in the paper “On the Electrodynamics of Moving Bodies”, he worked out the foundations of special relativity, setting out new laws of motion that generalised Newton's laws and passed into them in the case of small velocities of bodies, when v << c. He based his theory on two postulates: the special principle of relativity, which is a generalisation of Galileo's mechanical principle of relativity to any physical phenomena (in all inertial frames all physical processes — mechanical, electrical, thermal, optical and others — proceed in the same way), and the principle of the constancy of the speed of light in vacuum (the speed of light in vacuum does not depend on the motion of the source of light or of the observer and is the same in all directions, that is, the same in all inertial frames, and equal to 3 * 1010 cm/s). The two postulates and the theory built on them led to the breaking of many established classical concepts (absolute space, absolute time), forced a revision of a number of the basic propositions of Newton's classical physics, and established a new view of the world, with new ideas of space and time (the relativity of length, of time and of the simultaneity of events).
This theory, however, did not entirely discard the laws established by classical mechanics, but refined them for motion at speeds comparable with the speed of light in vacuum. Proceeding from his theory, in the same year, 1905, he discovered the law of the interrelation of mass and energy. He showed that mass is a measure of the energy contained in bodies. This Einstein relation (E = mc2) underlies the calculation of the energy balance of nuclear reactions, and of all nuclear physics. All the propositions and conclusions of special relativity were brilliantly confirmed in numerous experiments, and the theory became a powerful tool in physical research, in particular in the physics of the microworld. Einstein's role in the creation of quantum theory is also considerable. Whereas M. Planck (1900) quantised only the energy of a material oscillator, Einstein introduced in 1905 the idea of a discrete, quantum structure of the light radiation itself, treating it as a stream of light quanta, or photons (the photon theory of light).
Thus the theoretical discovery of the photon, detected experimentally in 1922 by A. Compton, belongs to Einstein. Proceeding from the quantum theory of light, he explained such phenomena as the photoelectric effect (the Einstein law for the photoelectric effect), the Stokes rule for fluorescence, photoionisation and others, which the electromagnetic theory of light could not explain (Nobel Prize, 1921). In 1907 he extended the ideas of quantum theory to physical processes not directly connected with light. In particular, by considering the thermal vibrations of atoms in a solid and applying the ideas of quantum theory, he explained the decrease of the heat capacity of solids as the temperature is lowered, and so developed the first quantum theory of the heat capacity of solids (1907). In 1909 he was the first to consider wave-particle duality for radiation, and also the fluctuations of the energy of equilibrium radiation, obtaining a formula for the energy fluctuation. In 1912 he established the basic law of photochemistry: each absorbed photon causes one elementary photoreaction (the Einstein law).
In 1916 he predicted the phenomenon of induced emission and introduced the probabilities of spontaneous and stimulated emission (the Einstein coefficients). In statistical physics he developed in 1905 the molecular-statistical theory of Brownian motion, and in 1924—25 he created the quantum statistics of particles with integer spin (Bose — Einstein statistics). In 1915 he predicted, and together with W. de Haas detected experimentally, the effect of a change in the mechanical angular momentum of a body when it is magnetised (the Einstein — de Haas effect).
In 1915 he completed the creation of general relativity, or the modern relativistic theory of gravitation, which established a connection between space-time and matter. Einstein was led to it by the analysis of the well-known fact that the ratio of the inertial mass of a body to its gravitational mass is the same for all bodies (the principle of equivalence). This principle, together with the principle of relativity, formed the basis of general relativity, which explained the essence of gravitation, consisting in a change of geometrical properties, a curvature of four-dimensional space — time around bodies, which form the field (any mass affects the metric of the surrounding space). He derived the equation describing the gravitational field — the Einstein equation (in 1915 the generally covariant equations of the gravitational field were obtained also by D. Hilbert). To test his theory he proposed three effects: the bending of a light ray in the gravitational field of the Sun, the shift of the perihelion of Mercury, and the gravitational red shift. These effects, as later experiments showed, really exist and were predicted quantitatively correctly by general relativity.
In 1916 he postulated gravitational waves, and in 1918 he derived a formula for the power of gravitational radiation. General relativity gave rise to the rapid development of cosmology as a science. Proceeding from this theory, Einstein proposed in 1917 a new model of the Universe, according to which the Universe is a closed three-dimensional space (a three-dimensional sphere) of finite volume, unchanging in time. This model, however, does not correspond to reality, since the Universe is non-stationary and is expanding. This was first shown theoretically by A. A. Friedmann, and in 1929 it was confirmed by observations (the recession of galaxies).
From 1933 Einstein's work concerned questions of cosmology and the unified field theory. Attempts to construct such a theory, however, ended in failure. Einstein's work raised a number of epistemological problems, but his philosophical views are not always consistent. He was a member of many academies of sciences and scientific societies, in particular a foreign member of the USSR Academy of Sciences (1926).
In 1905, in the paper “On the Electrodynamics of Moving Bodies”, he worked out the foundations of special relativity, setting out new laws of motion that generalised Newton's laws and passed into them in the case of small velocities of bodies, when v << c. He based his theory on two postulates: the special principle of relativity, which is a generalisation of Galileo's mechanical principle of relativity to any physical phenomena (in all inertial frames all physical processes — mechanical, electrical, thermal, optical and others — proceed in the same way), and the principle of the constancy of the speed of light in vacuum (the speed of light in vacuum does not depend on the motion of the source of light or of the observer and is the same in all directions, that is, the same in all inertial frames, and equal to 3 * 1010 cm/s). The two postulates and the theory built on them led to the breaking of many established classical concepts (absolute space, absolute time), forced a revision of a number of the basic propositions of Newton's classical physics, and established a new view of the world, with new ideas of space and time (the relativity of length, of time and of the simultaneity of events).
This theory, however, did not entirely discard the laws established by classical mechanics, but refined them for motion at speeds comparable with the speed of light in vacuum. Proceeding from his theory, in the same year, 1905, he discovered the law of the interrelation of mass and energy. He showed that mass is a measure of the energy contained in bodies. This Einstein relation (E = mc2) underlies the calculation of the energy balance of nuclear reactions, and of all nuclear physics. All the propositions and conclusions of special relativity were brilliantly confirmed in numerous experiments, and the theory became a powerful tool in physical research, in particular in the physics of the microworld. Einstein's role in the creation of quantum theory is also considerable. Whereas M. Planck (1900) quantised only the energy of a material oscillator, Einstein introduced in 1905 the idea of a discrete, quantum structure of the light radiation itself, treating it as a stream of light quanta, or photons (the photon theory of light).
Thus the theoretical discovery of the photon, detected experimentally in 1922 by A. Compton, belongs to Einstein. Proceeding from the quantum theory of light, he explained such phenomena as the photoelectric effect (the Einstein law for the photoelectric effect), the Stokes rule for fluorescence, photoionisation and others, which the electromagnetic theory of light could not explain (Nobel Prize, 1921). In 1907 he extended the ideas of quantum theory to physical processes not directly connected with light. In particular, by considering the thermal vibrations of atoms in a solid and applying the ideas of quantum theory, he explained the decrease of the heat capacity of solids as the temperature is lowered, and so developed the first quantum theory of the heat capacity of solids (1907). In 1909 he was the first to consider wave-particle duality for radiation, and also the fluctuations of the energy of equilibrium radiation, obtaining a formula for the energy fluctuation. In 1912 he established the basic law of photochemistry: each absorbed photon causes one elementary photoreaction (the Einstein law).
In 1916 he predicted the phenomenon of induced emission and introduced the probabilities of spontaneous and stimulated emission (the Einstein coefficients). In statistical physics he developed in 1905 the molecular-statistical theory of Brownian motion, and in 1924—25 he created the quantum statistics of particles with integer spin (Bose — Einstein statistics). In 1915 he predicted, and together with W. de Haas detected experimentally, the effect of a change in the mechanical angular momentum of a body when it is magnetised (the Einstein — de Haas effect).
In 1915 he completed the creation of general relativity, or the modern relativistic theory of gravitation, which established a connection between space-time and matter. Einstein was led to it by the analysis of the well-known fact that the ratio of the inertial mass of a body to its gravitational mass is the same for all bodies (the principle of equivalence). This principle, together with the principle of relativity, formed the basis of general relativity, which explained the essence of gravitation, consisting in a change of geometrical properties, a curvature of four-dimensional space — time around bodies, which form the field (any mass affects the metric of the surrounding space). He derived the equation describing the gravitational field — the Einstein equation (in 1915 the generally covariant equations of the gravitational field were obtained also by D. Hilbert). To test his theory he proposed three effects: the bending of a light ray in the gravitational field of the Sun, the shift of the perihelion of Mercury, and the gravitational red shift. These effects, as later experiments showed, really exist and were predicted quantitatively correctly by general relativity.
In 1916 he postulated gravitational waves, and in 1918 he derived a formula for the power of gravitational radiation. General relativity gave rise to the rapid development of cosmology as a science. Proceeding from this theory, Einstein proposed in 1917 a new model of the Universe, according to which the Universe is a closed three-dimensional space (a three-dimensional sphere) of finite volume, unchanging in time. This model, however, does not correspond to reality, since the Universe is non-stationary and is expanding. This was first shown theoretically by A. A. Friedmann, and in 1929 it was confirmed by observations (the recession of galaxies).
From 1933 Einstein's work concerned questions of cosmology and the unified field theory. Attempts to construct such a theory, however, ended in failure. Einstein's work raised a number of epistemological problems, but his philosophical views are not always consistent. He was a member of many academies of sciences and scientific societies, in particular a foreign member of the USSR Academy of Sciences (1926).