Nikolay Alekseevich Umov (russian: Никола́й Алексе́евич У́мов; January 23, 1846 – January 15, 1915) was a Russian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

known for discovering the concept of

Umov-Poynting vector In physics, the Poynting vector (or Umov–Poynting vector) represents the directional energy flux (the energy transfer per unit area per unit time) or ''power flow'' of an electromagnetic field. The SI unit of the Poynting vector is the wa ...

and

Umov effect The Umov effect, also known as Umov's law, is a relationship between the albedo of an astronomical object, and the degree of polarization of light reflecting off it. The effect was discovered by the Russian physicist Nikolay Umov in 1905, and can ...

Biography

Umov was born in 1846 in

Simbirsk Ulyanovsk, known until 1924 as Simbirsk, is a city and the administrative center of Ulyanovsk Oblast, Russia, located on the Volga River east of Moscow. Population: The city, founded as Simbirsk (), was the birthplace of Vladimir Lenin ( ...

(present-day Ulyanovsk) in the family of a military doctor. He graduated from the Physics and Mathematics department of

Moscow State University M. V. Lomonosov Moscow State University (MSU; russian: Московский государственный университет имени М. В. Ломоносова) is a public research university in Moscow, Russia and the most prestigious ...

in 1867 and became a Professor of Physics in 1875. He studied theoretical physics by reading works of Gabriel Lamé, Clebsch and

Clausius Rudolf Julius Emanuel Clausius (; 2 January 1822 – 24 August 1888) was a German physicist and mathematician and is considered one of the central founding fathers of the science of thermodynamics. By his restatement of Sadi Carnot's principl ...

, that made a significant impact on the originality of his later ideas in physics. Umov became the head of the Physics department of Moscow State University (MSU) after

Aleksandr Stoletov Alexander Grigorievich Stoletov (russian: Алекса́ндр Григо́рьевич Столе́тов; 10 August 1839 – 27 May 1896) was a Russian physicist, founder of electrical engineering, and professor in Moscow University. He was the ...

died in 1896. Together with

Pyotr Lebedev Pyotr Nikolaevich Lebedev (; 24 February 1866 – 1 March 1912) was a Russian physicist. His name was also transliterated as Peter Lebedew and Peter Lebedev. Lebedev was a creator of first scientific school in Russia. Career Lebedev made his doc ...

, Umov actively participated in founding the Physical Institute at the MSU. He organized several educational societies. He was the president of the Moscow Society of Nature Explorers for 17 years. He was among the first Russian scientists who acknowledged the importance of the

theory of relativity The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in ...

. In 1911, along with a group of leading professors, he left Moscow University in protest of reactionary actions of the government. Umov died in 1915 in Moscow.

Contribution to physics

Umov was the first who introduced in physics such basic concepts as speed and direction of movement of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of ...

, which are now associated with

, and density of energy in a given point of space. During his work in

Odessa Odesa (also spelled Odessa) is the third most populous city and municipality in Ukraine and a major seaport and transport hub located in the south-west of the country, on the northwestern shore of the Black Sea. The city is also the administrativ ...

from 1873 to 1874, Umov published first papers containing the major ideas of energy movement. In his first works of this period, Umov considered

potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potenti ...

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acce ...

of some environments "imperceptible for us". From this hypothesis, he made a conclusion: it is always possible to specify a place where the energy is in. Therefore, it is natural to raise the question about movement of energy. In his following works, Umov did not bind himself to this hypothesis about the nature of potential energy, but was guided by the principle of energy conservation only. After formulating the concept of density and movement of energy, he wrote differential equations for energy movement in the elastic media and in the fluid. The authoritative ''Encyklopädie der mathematischen Wissenschaften'' states: He was the first scientist to indicate interrelation between mass and energy proposing the formula ''E = kmc²'' with 0,5 ≤ k ≤ 1 as early as in 1873.''Умов Н. А. Избранные сочинения'' .A. Umov. Selected Works М. — Л., 1950. In 1875, Umov solved a general problem of distribution of electric currents in conducting surfaces of any kind. Between 1888 and 1891, he investigated experimentally the diffusion in water solutions, the polarization of light in opaque media, and discovered the effect of chromatic depolarization of light. In 1900, he conducted a thorough analysis of many

Gauss Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...

formulae regarding terrestrial magnetism, which allowed the definition of secular changes of the Earth's magnetic field.

References

External links

Umov's works review

{{DEFAULTSORT:Umov, Nikolay Russian physicists Russian mathematicians Moscow State University alumni 1846 births 1915 deaths Scientists from the Russian Empire