Umov, Nikolai

Born Jan. 23 (Feb. 4), 1846, in Simbirsk, now Ul’ianovsk; died Jan. 15 (28), 1915, in Moscow. Russian physicist.

The son of military physician, Umov graduated in 1867 from Moscow University, where he remained to study for a professorship. He was appointed a docent at Novorossiia University in Odessa in 1871 and a professor in 1875. In 1893 he was appointed a professor at Moscow University, where he founded an institute of physics; he left the university in 1911 in protest against the reactionary activities of the minister of education, L. A. Kasso. During his last years, Umov conducted experimental research in the laboratory of the Moscow Technical School.

Umov’s first studies (1870–72) were devoted to the theory of oscillatory processes in elastic media, a theory he expanded to include thermomechanical phenomena in such media. In 1873 and 1874 he published works on the motion of energy, in which he developed the concepts of energy density at a given point and the speed of the motion of energy and in which he introduced the concept of the flux density of energy (the Umov vector). In 1875 he proposed a general solution to the problem of the distribution of electric currents on arbitrary conducting surfaces. From 1888 to 1891, Umov conducted an experimental study of diffusion in aqueous solutions and of the effects associated with light scattering in turbid media. He also discovered the phenomenon of chromatic depolarization of light rays incident on a matte surface. From 1902 to 1904 he conducted research on the theory of terrestrial magnetism.

Umov helped promote science through his important work as a lecturer and author of scientific articles for the general public. He was a member of various scientific societies, including the Moscow Society of Naturalists, of which he was elected president in 1897.