Petr Petrovich Lazarev (13.04.1878-24.04.1942) was a Soviet physicist and biophysicist and an academician (1917). He was born in Moscow. He graduated from the medical faculty of Moscow University (1901), and in 1903 he passed the examinations of the faculty of physics and mathematics as well, as an external student. He began his scientific work in 1905 in P. N. Lebedev's laboratory, soon becoming his assistant and his closest helper. From 1908 he taught at the same time at the Moscow Higher Technical School (in 1914—23 he was head of a department). In 1911, together with many progressive Russian scholars of Moscow University, he left the university in protest against the reactionary policy of L. Kasso, the minister of education, and continued his scientific work with P. N. Lebedev at the A. L. Shanyavsky People's University. After P. N. Lebedev's death (1912) he became head of his laboratory, and in 1916 director of the first Research Institute of Physics of the Society of the Moscow Scientific Institute.
After the victory of the Great October Socialist Revolution Lazarev took an active part in organising Soviet science. In 1917—22 he was director of the physical laboratory of the Russian Academy of Sciences. On his initiative the Institute of Biological Physics was set up, of which he was director in 1920 — 31 (from 1927 the Institute of Physics and Biophysics). From 1932 he was head of the biophysics laboratory of the All-Union Institute of Experimental Medicine, and from 1938 director of the Biophysical Laboratory of the USSR Academy of Sciences (in 1937-41 he was also head of a department at the Institute of Theoretical Geophysics of the USSR Academy of Sciences).
His research concerned physics, physical chemistry, geophysics, biophysics, medicine and the history of physics. He studied the laws of the chemical action of light and carried out research on the thermal conductivity of rarefied gases. Lazarev was one of the pioneers of modern biophysics (the physiology of the sense organs, the theory of nervous excitation, the paths along which excitation spreads in the central nervous system). He contributed to the ionic theory of excitation, worked out a theory of visual perception and also a theory of hearing, studied the adaptation of the sense organs and took an interest in the psychology of creative work.
He took part in the investigation of the Kursk magnetic anomaly; under his direction extensive geomagnetic surveys were carried out (in the early 1920s) which showed that an enormous iron-ore deposit lay in that region.
The author of a number of books on the history of science and of biographies of scientists. He created a school of physicists (S. I. Vavilov, G. A. Gamburtsev, A. L. Mints, A. P. Rehbinder, V. V. Shuleikin, A. S. Predvoditelev, N. K. Shchodro, P. N. Belikov, M. P. Volarovich, B. V. Derjaguin, B. V. Ilyin, T. K. Molody, S. N. Rzhevkin, N. Ya. Selyakov, E. V. Shpolsky and others). Founder and, in 1918—24, editor of the journal “Uspekhi Fizicheskikh Nauk”.