Nikolai Alexeyevich Umov (4.02.1846 28.01.1915) — Russian physicist. Born in Simbirsk (now Ulyanovsk). Graduated from Moscow University (1867) and was retained to prepare for a professorship. In 1871—93 he taught at Novorossiysk University (Odessa), where he lectured on theoretical physics (professor from 1875); in 1893 —1911 he was a professor at Moscow University (from 1896, after the death of A. G. Stoletov, he headed the department of physics). In 1911 he left the university, together with a group of leading scholars, in protest against the reactionary actions of the Minister of Education L. A. Kasso, and continued his work in the Moscow Society of Naturalists, which he had headed since 1897, and in the Ledentsov Society.
His research concerned the theory of oscillatory processes, electricity, optics, terrestrial magnetism and molecular physics. An important result of his theoretical work was the creation of a doctrine of the motion of energy, which he set out in 1874 in his doctoral dissertation “The Equation of the Motion of Energy in Bodies”. In it he was the first to introduce the concepts of the velocity and direction of motion of energy, of the energy flux, of the energy density at a given point of a medium, and of the spatial localisation of the energy flux. In 1884 J. Poynting introduced the concept of the flux of electromagnetic energy, describing the motion of electromagnetic energy by means of a vector (the Umov–Poynting vector).
In 1875 he solved the problem of the distribution of electric currents over a surface of any kind (until then the problem had been solved only for particular cases). He revealed the physical meaning of many complex formulas of Gauss in the theory of terrestrial magnetism, which made it possible to determine the secular variations of terrestrial magnetism. He predicted (1888) the complexity of atoms and their evolution. He was one of the first to understand and appreciate the significance of the theory of relativity. Besides the theoretical work, his experimental studies are also known: of the diffusion of aqueous solutions, of the polarisation of light in turbid media, and others. He was an active promoter of science and a popularizer of knowledge of the natural sciences.