UMOV, NIKOLAI ALEXEEVICH

(b. Simbirsk [now Ul’ianovsk], Russia, 4 February 1846; d. Moscow, Russia, 28 January 1915)

physics.

Umov’s father, Alexei Pavlovich Umov, was a physician who achieved a reputation as an entomologist; his mother, whose maiden name was Susokolova, was a housewife. The family moved in 1858 to Moscow, where in 1863 Nikolai graduated from the gymnasium with a gold medal and then entered the division of mathematics of the Faculty of Physics and Mathematics at Moscow University. He graduated in 1867 and remained at the university to prepare for an academic career; at the same time he taught physics in a secondary school.

Umov passed his M.Sc. examinations in 1870, and the following year was appointed docent at Novorossiia University in Odessa. In 1872 he defended his M.Sc. thesis, and two years later his doctoral dissertation. From 1875 to 1893 Umov was a professor at Novorossiia University. During that time he came into close contact with two outstanding Russian scholars—I. I. Mechnikov and I. M. Sechenov—whom he greatly admired.

In 1893 Umov moved to Moscow as professor of physics at Moscow University. He succeeded A. G. Stoletov as department head in 1896. In 1911 he was among a group (including P. N. Lebedev) who left the university to protest the reactionary policy of the Ministry of Education. Umov then concentrated his efforts at the Moscow Society of Natural Philosophy (of which he was president from 1897 to 1914) and on publishing the journal Vremennik.

Umov began his career as a theoretician, but he also did much experimental work (especially during the second Moscow period of his life). In his M.Sc. thesis he investigated thermomechanical phenomena in elastic bodies. He solved the general problem of distribution of the elastic stresses within a solid body placed in a nonuniform temperature field; the problem generalized that formulated by William Thomson (1857). Umov’s dissertation was devoted to the problems of energy transfer in bodies. In it he put forward the idea of localization of energy and of its density, and introduced the concept of energy flux (Umov’s vector). The theory was constructed in close analogy to the theory of heat conduction. In recognition of Umov’s contribution to the problem of energy propagation (independently developed in 1884 by J. H. Poynting for the transfer of electromagnetic energy), the corresponding vector has been named the Umov-Poynting vector.

Umov’s most fundamental experiments are associated with the optics of turbid media and with the problem of polarization and depolarization of light falling on various surfaces. In the course of the necessary research, Umov developed a spectral apparatus that has become widely used not only in the laboratory but also in industry (analysis of dyestuffs in textile production).

Early in his Moscow professorship, Umov lectured at the Faculty of Medicine of the university on the mechanics of bones and on physiological optics and acoustics. He was a sharp critic of vitalism.

Being a progressive physicist, Umov reacted positively to the theories of relativity and the quantum. He developed transformation formulas that included! Lorentz’s as a special case (the same way was chosen by Max von Laue in 1911). Umov also wrote some interesting papers on the quantum theory of radiation, one of which contains a formula identical to the uncertainty relation for time and energy.

Umov married Elena Leonardovna Novitskaya in 1872; they had a daughter.

Umov was involved in the work of the Pedagogical Society and the Kh. S. Ledentsov Society for Advancement of Experimental Science and Applications. The fairly large means of the latter were directed on Umov’s initiative, to support the work of P. N. Lebedev and I. P. Pavlov, and to establish the society’s library.

Umov was a brilliant lecturer. His university and popular lectures were illustrated by carefully prepared demonstrations.

During his free time (of which he had little) Umov drew and also painted landscapes.

BIBLIOGRAPHY

I. Original Works. Teoria termomekhankheskikh iavienii v tverdikh uprugikh telakh (Theory of thermomechanical phenomena in solid elastic bodies; Moscow, 1871); “Abteilung der Bewegungsgleichungen der Energie in kontinuierlichen Körpem”, in Zeitschrift für Mathemuiik und Physik, 19 (1874), 418-431; “Difluzia vodnogo zastvoza povazennoi soli” (Diffusion of water solution of a salt), in Zapiski Novorossiiskogo Obshchestva estestvoispitatelei, 14 , no. 1 (1889), 1-67; “Interprétation géométrique des integrates de Fresnel”, in Séances de la Société physique de Paris, 14 , no. 1 (1896), 322; “Ueber eine Methode objektiver Darstellung der Eigenschaften des polarisierten Lichtes”, in Annalen der Physik, 4th ser,. 2 (1900), 72-77; “Die Konstruktion des geometrischen Bildes des Gauss’schen Potentials, als Methode zur Erforschung der Gesetze des Erdmagnetismus”, in Terrestrial Magnetism and Atmospheric Electricity, 9 (1904), 105-112; “Etnheitliche Abteilung der Transformationen, die mit dem Relativitätsprinzip verträglich sind”, in Physikalisclw Zeitschrift, 11 (1910), 905-908; “Die Bedingungen der Invarianz der Wellengleichung”, ibid., 13 (1912), 292-293; “Eine spektropolariskoptsche Methode zur Erforschung der Lichtabsorplion und der Natur der Farbstoffe”. ibid., 962-971; “Ein moglicher Sinn der Quantentheorie”, ibid., 15 (1914), 380-382; and “Avtobiograficheskii ocherk” (Autobiographical sketch), in N. A. Umov, Izbrannie sochineniia (Collected works; Moscow, 1950), 9-28. Umov’s papers and letters are in the U.S.S.R. Academy of Sciences Archive, Leningrad.

II. Secondary Literature. D. D. Gulo, Nikolai Alekseevich Umov (Moscow, 1971); P. P. Lazarev, N. A. Umov, in Ocherki istorii russkoi nauki (Moscow and Leningrad, 1950); and E. V. Shpolskii, “Nikolai Alekseevich Umov,” in Uspekhi fizicheskikh nauk, 31 , no. 1 (1947), 129.