Pyotr Nikolaevich Lebedev (1866-1912) - Russian experimental physicist, who was the first to experimentally confirm the presence of light pressure, the creator of the first Russian school of physicists. Professor at Moscow University (1900-11), resigned in protest against the harassment of students. First received (1895) and investigated millimeter electromagnetic waves. He discovered and measured the pressure of light on solids (1900) and gases (1908), quantitatively confirming the electromagnetic theory of light. Lebedev's name is borne by the Physical Institute of the Russian Academy of Sciences.

Years of study

Pyotr Lebedev was born February 24 (March 8), 1866, Moscow in a merchant family. Petya became interested in physics in his youth, but since access to the university was closed for him, as a graduate of a real school, he entered the Moscow Higher Technical School. Subsequently, Lebedev said that familiarity with technology turned out to be very useful to him in the design of experimental installations.

In 1887, without graduating from the Technical School, Lebedev went to Germany, to the laboratory of the famous German physicist August Kundt, for whom he worked first in Strasbourg (1887-88), and then in Berlin (1889-90). In 1891, having written his dissertation "On the measurement of the dielectric constants of vapors and on the theory of dielectrics Mossoti - Clausius", he passed the exam for the first degree.

Return to Russia

Upon his return to Russia in 1891, Pyotr Lebedev received an assistant position in the laboratory of Professor Alexander Grigoryevich Stoletov at Moscow University. The cycle of works performed by Kundt was included in the master's thesis presented by Lebedev in 1899 "On the ponderomotive action of waves on resonators", which was so highly appreciated that Lebedev was immediately awarded the degree of Doctor of Physics.

In 1900, P. Lebedev was approved as a professor at Moscow University, where he organized a laboratory. Not without some opposition from certain colleagues, Lebedev began to actively carry out experimental work. By this time, he had already gained fame and experience as one of the first researchers who relied on the theory of James Clerk Maxwell. Back in 1895, Lebedev created the finest installation for generating and receiving electromagnetic radiation with a wavelength of 6 and 4 mm, studied the reflection, refraction, polarization, interference of these waves, and other phenomena.

light pressure

In 1900, Petr Lebedev, with the help of virtuoso, albeit performed by modest means, experiments confirmed Maxwell's theoretical prediction about the pressure of light on solids, and in 1908 on gases. This was an important milestone in the science of electromagnetic phenomena. The well-known English physicist William Thomson owns the words: “All my life I fought with Maxwell, did not recognize his light pressure, and now ... Lebedev made me give up before his experiments.”

Pyotr Nikolaevich Lebedev also studied the action of electromagnetic waves on resonators and, in connection with these studies, put forward profound considerations concerning intermolecular interactions, dealt with acoustics, in particular, hydroacoustics. The study of the pressure of light on gases prompted Lebedev to become interested in the origin of comet tails.

The first scientific physics school in Russia

Not limited to research activities, Petr Lebedev devoted much effort to the creation of a scientific physical school, which, in essence, was the first in Russia. By 1905, his laboratory already included about twenty young scientists who were destined to play a prominent role in the development of physics in Russia. Lebedev's assistant and closest assistant was Pyotr Petrovich Lazarev, who, after the death of his teacher, became the head of the laboratory, and in 1916 - the director of the first Scientific Research Institute of Physics in Moscow, from which Sergey Ivanovich Vavilov, Grigory Alexandrovich Gamburtsev, Alexander Lvovich Mints, Pyotr Alexandrovich Rebinder left , Vasily Vladimirovich Shuleikin, Eduard Vladimirovich Shpolsky and others. The Physical Institute of the Russian Academy of Sciences in Moscow is named after P. N. Lebedev.

The latest experiments of Pyotr Lebedev

Lebedev's experiments required the use of carefully thought-out, sometimes quite complex "mechanics". This sometimes gave rise to ridiculous reproaches that Lebedev "reduced science to the level of technology." However, P. Lebedev himself considered the issue of the connection between science and technology to be very important.

The last cycle of Lebedev's studies is still underestimated. These studies were aimed at testing the hypothesis of the English physicist Sutherland regarding the redistribution of charges in conductors under the influence of gravity. In celestial bodies, planets and stars, according to Sutherland, electrons are “squeezed out” from the inner regions (where pressures are high) to the surface, due to which the inner regions are positively charged, and the surface of the bodies is negatively charged. The rotation of bodies, together with the charges redistributed in them, should generate magnetic fields. Thus, a physical explanation was proposed for the origin of the magnetic fields of the Sun, the Earth, and other celestial bodies.

Sutherland's hypothesis did not have a reliable theoretical justification at that time, and therefore the experiment conceived by Peter Lebedev to test it acquired particular importance. Realizing that centrifugal forces, like gravitational ones, should cause a redistribution of charges, Lebedev put forward a simple but very ingenious idea: if Sutherland's hypothesis is correct, then a magnetic field should arise during the rapid rotation of electrically neutral bodies. It is precisely this "magnetization by rotation" that experiment was supposed to reveal.

The work took place in very difficult conditions. In 1911, in protest against the reactionary actions of the Minister of Public Education, Lev Aristidovich Kasso, Lebedev, together with other progressive teachers, decided to leave Moscow University. As a result, a very delicate experiment, which he conducted in the basement of the Faculty of Physics, was crumpled. The desired effect was not found. The reason for the failure was not the lack of effect, but the insufficient sensitivity of the installation: the estimates for magnetic fields, which Lebedev was guided by and which were based on the work of Sutherland, turned out to be significantly overestimated. Lebedev created a new physics laboratory at Shanyavsky University with private funds, but did not have time to continue his research.

Lebedev suffered from heart disease and once, while still relatively young, experienced clinical death: his heart suddenly stopped while he was rowing a boat, but then they managed to bring him back to life.

Lebedev Petr Nikolaevich

L Ebedev, Petr Nikolaevich - famous physicist (1866 - 1912). Born February 24, 1866 in Moscow, in a merchant family. He received his initial education at the Petropavlovsk German School and at a private real school; three years was a student of the Imperial Technical School. Feeling a vocation for pure science, Lebedev left the school in 1887, where he perfectly studied turning and locksmith crafts and acquired a skill in designing complex instruments, which turned out to be very useful for his future activities. Lebedev received his higher education from Kundt at the Strasbourg Institute of Physics, then from him in Berlin, where he also attended Helmholtz's theoretical physics lectures. Returning to Strasbourg, Lebedev prepared there, under the guidance of F. Kohlrausch, his doctoral work: "On the measurement of the dielectric constants of vapors and on the theory of dielectrics by Mossotti-Clausius" (1891). At the same time, Lebedev undertook the study of the theories of cometary tails and then already came to the idea of ​​the pressure of radiant energy and the possibility of its experimental proof. In 1891, Lebedev received a position as an assistant at the Moscow Institute and began an experimental study of the ponderomotive action of different waves on resonators. For this work, the summary results of which were published in 1892, Lebedev received a doctorate from Moscow University without a master's examination and without submitting a dissertation for a master's degree, a year later - a professorship at Moscow University. Performing the work "On the double refraction of rays of electric force" (1895), he discovered the shortest electromagnetic waves that have been obtained so far. Lebedev's brilliant experimental talent was fully reflected in his further work, when he set about realizing the main task of his life - the proof of light pressure. In 1900, Lebedev published the first report on the positive results of his experiments on the pressure of light on solids, in 1901 - the classic "Experimental study of light pressure." Only in 1910, after countless experiments, after more than 20 final instruments had been built and studied by him, Lebedev proved the pressure of light on gases (Journal of the Russian Physico-Chemical Society, 1910). In 1911, Lebedev, along with other professors, left Moscow University and had to transfer his activities to a small laboratory, arranged with private funds in a rented room. In recent years, Lebedev worked a lot on the question of the motion of the earth in the ether, tried to find out the causes of terrestrial magnetism and expressed extremely bold original ideas on this issue. His experiments gave negative results ("Magnetometric study of rotating bodies. First communication", "Journal of the Russian Physico-Chemical Society", 1911), but further work was interrupted by death. Lebedev died on March 1, 1912 from heart disease. - In addition to purely scientific work, Lebedev did a lot of popularizing the latest acquisitions of physics in speeches and articles. A very great merit of Lebedev is the creation of a whole school of young Russian physicists who worked in his laboratory under his talented and skillful guidance. He was the founder and chairman of the Moscow Physical Society, which now bears his name. In 1913, this society published Lebedev's "Collected Works" (M., with his biography and a complete list of works). Two of Lebedev's works on light pressure were published in 1913 by P. Lazarev, in "Ostwald's Klassiker der exakten Wissenschaften". Detailed biographies are written

Lebedev Petr Nikolaevich Lebedev Pyotr Nikolaevich

(1866-1912), physicist, founder of the first Russian scientific school of physicists. Professor at Moscow University (1900-11), resigned in protest against the harassment of students. First received (1895) and investigated millimeter electromagnetic waves. He discovered and measured the pressure of light on solids (1899) and gases (1907), quantitatively confirming the electromagnetic theory of light. Lebedev's name is borne by the Physical Institute of the Russian Academy of Sciences.

LEBEDEV Petr Nikolaevich

LEBEDEV Petr Nikolaevich (1866-1912), Russian physicist, founder of the first Russian scientific school of physicists. Professor at Moscow University (1900-11), resigned in protest against the harassment of students. First received (1895) and investigated millimeter electromagnetic waves. He discovered and measured the pressure of light on solids (1900) and gases (1908), quantitatively confirming the electromagnetic theory of light. Lebedev's name is borne by the Physical Institute of the Russian Academy of Sciences.
* * *
LEBEDEV Petr Nikolaevich, Russian experimental physicist, the first to confirm the presence of light pressure in experiment, the creator of the first Russian school of physicists.
Years of study
Lebedev was born into a merchant family. He became interested in physics in his youth, but since access to the university was closed for him, as a graduate of a real school, he entered the Moscow Higher Technical School. Subsequently, Lebedev said that familiarity with technology turned out to be very useful to him in the design of experimental installations.
In 1887, without graduating from the Technical School, Lebedev went to Germany, to the laboratory of the famous German physicist A. Kundt (cm. KUNDT August Adolf Eduard Eberhard), for whom he worked first in Strasbourg (1887-88), and then in Berlin (1889-90). In 1891, having written his dissertation "On the measurement of the dielectric constants of vapors and on the theory of dielectrics Mossoti - Clausius", he passed the exam for the first degree.
Return to Russia
Upon his return to Russia in 1891, Lebedev received an assistant position in the laboratory of Professor A. G. Stoletov at Moscow University (cm. STOLETOV Alexander Grigorievich). The cycle of works performed by Kundt was included in the master's thesis presented by Lebedev in 1899 "On the ponderomotive action of waves on resonators", which was so highly appreciated that Lebedev was immediately awarded the degree of Doctor of Physics. In 1900 he was approved as a professor at Moscow University, where he organized a laboratory. Not without some opposition from certain colleagues, Lebedev began to actively carry out experimental work. By this time, he had already gained fame and experience as one of the first researchers who relied on the theory of J.K. Maxwell (cm. MAXWELL James Clerk). Back in 1895, Lebedev created the finest installation for generating and receiving electromagnetic radiation with a wavelength of 6 and 4 mm, studied the reflection, refraction, polarization, interference of these waves, and other phenomena.
light pressure
In 1900, Lebedev, with the help of virtuoso, although performed by modest means, experiments confirmed Maxwell's theoretical prediction about the pressure of light on solids, and in 1908 on gases. This was an important milestone in the science of electromagnetic phenomena. To the famous English physicist W. Thomson (cm. Thomson William) the words belong: "All my life I fought with Maxwell, did not recognize his light pressure, and now ... Lebedev forced me to surrender before his experiments."
Lebedev also studied the action of electromagnetic waves on resonators and, in connection with these studies, put forward profound considerations concerning intermolecular interactions, dealt with acoustics, in particular, hydroacoustics. The study of the pressure of light on gases prompted Lebedev to become interested in the origin of comet tails.
The first scientific physics school in Russia
Not limited to research activities, Lebedev devoted much effort to the creation of a scientific physical school, which, in essence, was the first in Russia. By 1905, his laboratory already included about twenty young scientists who were destined to play a prominent role in the development of physics in Russia. Lebedev's assistant and closest assistant was P.P. Lazarev (cm. LAZAREV Petr Petrovich), who, after the death of his teacher, became the head of the laboratory, and in 1916 - the director of the first Scientific Research Institute of Physics in Moscow, from which S. I. Vavilov left (cm. VAVILOV Sergey Ivanovich), G. A. Gamburtsev (cm. GAMBURTSEV Grigory Alexandrovich), A. L. Mints (cm. MINTS Alexander Lvovich), P. A. Rebinder (cm. REBINDER Petr Alexandrovich), V. V. Shuleikin (cm. Shuleykin Vasily Vladimirovich), E. V. Shpolsky (cm. SHPOLSKY Eduard Vladimirovich) other. The Physical Institute of the Russian Academy of Sciences in Moscow is named after P. N. Lebedev.
Latest experiments
Lebedev's experiments required the use of carefully thought-out, sometimes quite complex "mechanics". This sometimes gave rise to ridiculous reproaches that Lebedev "reduced science to the level of technology." However, Lebedev himself considered the issue of the connection between science and technology very important.
The last cycle of Lebedev's studies is still underestimated. These studies were aimed at testing the hypothesis of the English physicist Sutherland regarding the redistribution of charges in conductors under the influence of gravity. In celestial bodies, planets and stars, according to Sutherland, electrons are “squeezed out” from the inner regions (where pressures are high) to the surface, due to which the inner regions are positively charged, and the surface of the bodies is negatively charged. The rotation of bodies, together with the charges redistributed in them, should generate magnetic fields. Thus, a physical explanation was proposed for the origin of the magnetic fields of the Sun, the Earth, and other celestial bodies.
Sutherland's hypothesis did not have a reliable theoretical justification at that time, and therefore the experiment conceived by Lebedev to test it acquired particular importance. Realizing that centrifugal forces, like gravitational ones, should cause a redistribution of charges, Lebedev put forward a simple but very ingenious idea: if Sutherland's hypothesis is correct, then a magnetic field should arise during the rapid rotation of electrically neutral bodies. It is precisely this "magnetization by rotation" that experiment was supposed to reveal.
The work took place in very difficult conditions. In 1911, in protest against the reactionary actions of the Minister of Education L. A. Kasso (cm. KASSO Lev Aristidovich) Lebedev, along with other progressive teachers, decides to leave Moscow University. As a result, a very delicate experiment, which he conducted in the basement of the Faculty of Physics, was crumpled. The desired effect was not found. The reason for the failure was not the lack of effect, but the insufficient sensitivity of the installation: the estimates for magnetic fields, which Lebedev was guided by and which were based on the work of Sutherland, turned out to be significantly overestimated. Lebedev created a new physics laboratory at Shanyavsky University with private funds, but did not have time to continue his research. Lebedev suffered from heart disease and once, while still relatively young, experienced clinical death: his heart suddenly stopped while he was rowing a boat, but then they managed to bring him back to life. He lived only 48 years.

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Books

• Benign diseases of the uterus , Lebedev Vladimir Alexandrovich , Strizhakov Alexander Nikolaevich , Davydov Alexander Ilgizirovich , Pashkov Vladimir Mikhailovich , In this edition, revised and supplemented, a number of aspects related to the diagnosis and treatment of patients with uterine myoma, adenomyosis are revised. The long-term results of organ-preserving ... Category: Textbooks for universities Series: Library of a medical specialist Publisher: GEOTAR-Media, Manufacturer:

Pyotr Nikolaevich Lebedev (1866-1912)

Pyotr Nikolaevich Lebedev entered the history of world science as the most skillful experimenter-physicist, who first discovered and measured the pressure of light. P. N. Lebedev, along with M. V. Lomonosov, is one of the remarkable figures in the history of Russian physics. He was the first organizer of collective scientific work in the field of physics and large research laboratories, which have become a model for scientific institutions today.

Pyotr Nikolaevich Lebedev was born on March 8, 1866 in Moscow, into a cultural merchant family. After studying at a real school, P. N. Lebedev entered the Moscow Technical School. However, he was attracted by difficult fundamental questions that went far beyond the curriculum of the courses he was studying. The archives of the Academy of Sciences of the USSR contain large notebooks of the young man Lebedev, revealing his extraordinary inventive wit, knowledge and, at the same time, special seriousness and concentration. Without graduating from the Technical School, P. N. Lebedev went abroad in 1887, to the University of Strasbourg, to study physics.

Here he worked for the famous experimental physicist August Kundt. Subsequently, P. N. Lebedev wrote a wonderful obituary to the memory of Kundt, containing his detailed and touching description. “Possessing a remarkable physical instinct,” writes Lebedev, “physikalische Nase,” as he himself called his talent, Kundt guessed the connection between separate, heterogeneous phenomena, and also grasped the essence of a mathematically developed theory with amazing clarity and always knew how to pose such a question point-blank, which, being the most daring consequence of the theory, would be accessible to direct experimental research. This characterization of Kundt can be fully applied to PN Lebedev himself.

Kundt did not stay long in Strasbourg. In 1888 he received a chair in Berlin, and P. N. Lebedev followed him. Here, in addition to classes with Kundt, PN Lebedev listened to Helmholtz's theoretical lectures.

Studying in childhood in a real school, P. N. Lebedev did not study Latin. Therefore, he was unable to pass the doctoral examination in Berlin, where knowledge of ancient languages ​​was essential. I had to return to Strasbourg - Latin was not required there. In Strasbourg, P. N. Lebedev quickly completed an experimental dissertation, passed the exams and received a Ph.D. P. N. Lebedev's dissertation was entitled "On the measurement of the dielectric constants of vapors and on the theory of Mossotti-Clausius dielectrics." This excellent work, presented in 1891, was at one time done to test the consequences of the phenomenological theory of dielectrics, but it has retained its interest even now in connection with the more specific structural and molecular concepts of our time.

From the surviving letters of P. N. Lebedev, relating to this period of life, it is clear that he then wrote a lot and thought about even more, in addition to his doctoral work. By 1890, he was engaged in the theory of comet tails. These studies became the beginning of the main work of his life - research on light pressure.

Even Seneca knew that comet tails deviate from the Sun. Kepler, Newton and others suggested that the mechanical pressure of light could be the cause of this deflection. In the XVIII century. they tried to discover it experimentally and, indeed, found it. It turned out, however, that the observed phenomena are caused by secondary thermal processes and have nothing in common with light pressure.

There were too many reasons competing in any experiment with light pressure; on the other hand, there were no ideas about the theoretical value of the possible pressure of light. At the end of the XVIII century. the physicist and astronomer Haratsaker pointed out, for example, that, according to travelers, the pressure of the sun's rays slows down the movement of the Danube. For the first time, Maxwell, on the basis of his electromagnetic theory of light, calculated the theoretical value of light pressure, which, for the case of light falling on a completely absorbing surface, is equal to the division of the light energy coming per second by the speed of light. For sunlight falling on the earth's surface, this pressure is approximately equal to five hundred millionths of a gram per square centimeter. Later it turned out that any wave theory of light leads to the same value for light pressure as Maxwell's theory, while the corpuscular concept gives a value twice as large. Thus, the problem of light pressure has been at least three centuries old; such physicists and astronomers as Kepler, Newton, Euler, Fresnel, Maxwell, Boltzmann were engaged in it. It was of fundamental importance for science, and yet until the end of the 19th century. remained unresolved.

PN Lebedev undertook this most difficult task. In 1891, his note "On the repulsive force of radiating bodies" appeared. In it, based on known data on solar radiation, P. N. Lebedev proves that in the case of very small particles, the repulsive force of light pressure must exceed Newtonian attraction, and thus the deflection of cometary tails can indeed be explained by light pressure. At the end of his note, P. N. Lebedev notes that his calculations are not quantitatively applicable to molecules, but qualitatively they do not lose their strength.

P. N. Lebedev was right when, excited by his thoughts, he wrote in a private letter: "I seem to have made a very important discovery in the theory of the motion of the stars, especially comets." In modern astrophysics, the enormous role of light pressure as a cosmic factor, along with Newtonian attraction, becomes obvious. For the first time, a physically justified indication of this was made by P. N. Lebedev.

Having set as his task the clarification of the question of the mechanical forces arising between the radiating and absorbing molecule, P. N. Lebedev returned, full of plans, to Moscow in 1891.

He received a position as an assistant at the Moscow University at the department of Professor A. G. Stoletov and, in very difficult conditions, arranged his laboratory, remaining cheerful and full of creative energy.

Three years later, in 1894, the first part of his great work appeared, which later served as a doctoral dissertation "Experimental study of the ponderomotive action of waves on resonators". In view of the exceptional qualities of his work, P. N. Lebedev was awarded the degree of doctor without preliminary defense of his master's thesis and the corresponding examinations, a very rare case in the practice of universities. The first part of this work is devoted to the experimental study of the interactions of electromagnetic resonators, the second - to hydrodynamic resonators (oscillating balls in a liquid), the third - to acoustic ones. Experience (in agreement with theory) showed the identity of these different cases. From the experimental side, the work was a model of thoroughness, wit and, if I may say so, the jewelry skill of P. N. Lebedev. "The main interest in studying the ponderomotive action of undulating motion," the author wrote, "lies in the fundamental possibility of extending the found laws to the region of light and thermal emission of individual molecules of bodies and precalculating the resulting intermolecular forces and their magnitude."

The work was completed in 1897. Wave pressure was studied on models. This was the second stage of the main case of P. N. Lebedev. The third, most important stage lay ahead - an attempt to overcome the difficulties encountered over the centuries by many unsuccessful predecessors of P. N. Lebedev, and to detect and measure the pressure of light in the laboratory.

In 1900, this stage also ends with complete success. The light pressure has been found. P. N. Lebedev succeeded in separating from it the interfering, so-called radiometric, forces and convection flows and measuring it. In appearance, the device of P. N. Lebedev was simple. Light from a voltaic arc fell on a light winglet suspended on a thin thread in a glass container from which air was pumped out, and the light pressure could be judged from the twisting of the thread. In fact, this simplicity concealed innumerable difficulties that had been overcome. The wing actually consisted of two pairs of thin platinum circles. One of the circles of each pair was shiny on both sides, the other two had one side covered with platinum black. At the same time, both pairs of circles differed in thickness. In order to exclude gas convection (movement) that occurs when the temperatures of the winglet and the glass container differ (the temperature difference arose when light was absorbed by the winglet), the light was directed first to one side of the winglet, then to the other. Since the convection is the same in both cases, the difference in deviations obtained does not depend on the convection. First of all, the radiometric forces were weakened as much as possible (by increasing the volume of the balloon and decreasing the pressure). In addition, the radiometric effect could be taken into account by comparing the result of light falling on a thick and thin blackened circle. P. N. Lebedev rightly and proudly could finish his message with a short phrase: "Thus, the existence of Maxwell-Bartoli pressure forces has been experimentally established for light rays."

The experiments of P. N. Lebedev brought him worldwide fame and forever inscribed his name in the history of experimental physics. In Russia, he received a prize from the Academy of Sciences for these experiments and was then elected a corresponding member of the Academy. About the impression that the experiments of P. N. Lebedev made on the scientific world, say, for example, the words of the famous English physicist Lord Kelvin, said to the famous Russian scientist K. A. Timiryazev: "You may know that I fought all my life with Maxwell, not recognizing his light pressure, and now your Lebedev made me give up before his experiments.

However, P. N. Lebedev did not consider the task finished. For cosmic phenomena, it is not the pressure on solid bodies that is of primary importance, but the pressure on rarefied gases consisting of isolated molecules. Meanwhile, in relation to the structure of molecules and their optical properties in the first decade of our century, there were still many ambiguities. It was not clear how one could go from pressure on individual molecules to pressure on the body as a whole. The theoretical state of the matter at that time, in short, was such that experimental intervention was required.

The experimental problem facing P. N. Lebedev was this time even more difficult than the previous one, and attempts to solve it lasted ten years. But this time, too, the experimental art of P. N. Lebedev overcame all difficulties. In P. N. Lebedev's miniature device, the gas, under the pressure of the absorbed light, received a rotational movement, which was transmitted to a small piston, the deviation of which could be measured by the displacement of the mirror "bunny". The most important difficulty of the experiment - the elimination of the inevitable gas convection in the device - was overcome by P. N. Lebedev by the ingenious method of mixing hydrogen into the gas under study. Unlike other gases, hydrogen is a good conductor of heat, quickly equalizing temperature inhomogeneities in the vessel. This move turned out to be decisive. The new experiments of P. N. Lebedev, published in 1910, were greeted with enthusiasm by the world physical community. The British Royal Institute elected P. N. Lebedev its honorary member. The brilliant experimental physicist V. Vin, in a letter to the Russian physicist V. A. Mikhelson, wrote that P. N. Lebedev mastered "the art of experimentation to such an extent as hardly anyone else in our time."

This was the end of the amazing series of works by PN Lebedev on light pressure. She was interrupted by his untimely death. The answer to the question of light pressure, however, has not yet been completed. Special cases of pressure of elliptically polarized light remained experimentally unexplored, and most importantly, it was not yet possible to experimentally discover the nature of light pressure on an individual particle of matter. This was done much later by A. Compton, who observed the elementary effect of light pressure and the scattering of X-rays and gamma rays by electrons in a cloud chamber. Elementary light pressure turned out to be quantum, having a discontinuous character. The light pressure, measured by P. N. Lebedev, was the average statistical value of pressures in a variety of elementary processes. P. N. Lebedev did not have to take part in the disclosure of the statistical nature of the phenomenon, the masterful study of which he devoted his life to.

The number of other works by P. N. Lebedev is small. But each of them is important and has retained its significance even now. In the first years in Moscow, he again carried out a study “On the double refraction of rays of electric force”, amazing in terms of mastery of experience, experimenting with electromagnetic waves 6 millimeters long, a miniature “nicol” and a “quarter-wave plate” from crystalline sulfur. In 1902 he published a short, but very important article for physical measurements and technology, "Thermoelements in vacuum as a device for measuring radiant energy." The principle of a thermoelement in a vacuum, put forward by P. N. Lebedev, is now widely used, in particular, in military technology. In connection with one of the hypotheses about the nature of terrestrial magnetism, P. N. Lebedev modified Gilbert's experiment, which was aimed at an attempt to excite an electric current in a conductor as it moved through the ether. Proceeding from the assumption about the motion of the Earth in a motionless ether, P. N. Lebedev decided to take advantage of this motion; he set up the experiment, as usual, with the utmost care, but got a negative result. True, this experiment did not so much disprove the Rowland-Gilbert hypothesis as the assumption of a motionless ether.

The last, dying, experimental work of P. N. Lebedev also concerned the nature of terrestrial magnetism. He wanted to test Sutherland's hypothesis, in which the magnetic effect of the rotating Earth was explained by the displacement of opposite charges in a neutral atom, by experiment with a rotating model of the Earth. This difficult experience also gave a negative result.

While working at Moscow University, P. N. Lebedev paid the main attention to the research work of his students and employees. True, he read lectures, like other professors, even published a brief summary of these lectures, but in essence he was little interested in teaching work. His first lecture to beginning students always contained mainly an appeal to them to become researchers without fear of difficulties. For the first time in Russia, he ventured to organize a physical laboratory with a relatively very large number of employees. In 1901, only three people worked for him, in 1910 the number of employees reached 28. If we take into account that all the topics of the work were given and carefully thought out (up to the drawings of instruments) by P. N. Lebedev himself, that there were no laboratory assistants , mechanics and glassblowers were themselves working, that the laboratory's facilities and equipment were extremely limited, that it was placed in a poorly comfortable basement, it will become clear that the enormous effort and energy required from P.N. Lebedev to manage this laboratory. Meanwhile, year after year, more and more often came out a number of good and excellent works, many of which felt the masterful hand of the teacher. P. N. Lebedev became the pioneer of a remarkable and completely new thing for Russia - a great collective research work. Subsequently, in 1911, in a newspaper article "Russian Society and Russian National Laboratories", published in Russkiye Vedomosti, P. N. Lebedev set out his point of view and arguments in some detail, speaking about the benefits and necessity of creating large research laboratories. This was the first declaration of the system of organization of science, fully realized only in the USSR.

In 1911, in the era of the maximum flourishing of P. N. Lebedev’s activity and glory at Moscow University, as a result of the reactionary actions of the tsarist government, and in particular the then Ministry of Public Education, the most talented and liberal part of the professorship had to leave the university and seek shelter in other educational institutions or simply rely on the help of individuals. In protest against the actions of the Minister of Education L. Kasso, P. N. Lebedev also resigned, and his employees who worked in his laboratory left the university with him. A great deal was destroyed. PN Lebedev immediately received invitations from foreign scientific institutions. In particular, the director of the physicochemical laboratory of the Nobel Institute in Stockholm prof. Arrhenius wrote to him: “Naturally, it would be a great honor for the Nobel Institute if you wished to settle down and work there, and we, no doubt, would provide you with all the necessary funds so that you could continue to work ... You, of course , would receive a completely free position, as it corresponds to your rank in science. But P. N. Lebedev refused all these proposals. He stayed at home and in extremely difficult conditions, at private expense, using public assistance, organized a new physical laboratory. In Dead Lane (house number 20) in Moscow, a basement was rented, where in 1911 his laboratory was located in several rooms. Here he completed his last experimental work on the magnetometric study of rotating bodies. Private donors collected funds for the construction of a new physics institute for P. N. Lebedev according to a plan drawn up by him. This institute, however, was completed only in 1916, four years after Lebedev's death. This building currently belongs to the Academy of Sciences of the USSR; it houses the P. N. Lebedev Physical Institute for experimental work on the magnetometric study of rotating bodies. Private donors collected funds for the construction of a new physics institute for P. N. Lebedev according to a plan drawn up by him. This institute, however, was completed only in 1916, four years after Lebedev's death. This building currently belongs to the Academy of Sciences of the USSR; it houses the P. N. Lebedev Physical Institute.

March 14, 1912 P. N. Lebedev died. He died at the age of 46 and was buried at the Alekseevsky cemetery. In 1935, in connection with the liquidation of the cemetery, the ashes of P. N. Lebedev were transferred to the cemetery of the Novodevichy Convent.

The entire scientific world responded to the death of P. N. Lebedev. Many telegrams and letters were sent from eminent scientists, among whom were Roentgen, Nernst, Arrhenius, Thomson, Warburg, Rubens, Crookes, Curie, Rigi and others.

In the person of P. N. Lebedev, Russia lost not only a great scientist, but also a remarkable organizer of science, whose thoughts and undertakings could be fully realized only with Soviet Russia.

The main works of P. N. Lebedev: Collected works, ed. Physical society them. P. N. Lebedeva, M., 1913 [I. Scientific articles: On the measurement of the dielectric constants of vapors and the theory of dielectrics Mossotti-Clausius (Strasbourg dissertation), 1891; On the repulsive force of radiant bodies, 1891; On the double refraction of rays of electric force, 1895; Experimental study of the ponderomotive action of waves on resonators (doctoral dissertation), 1894-1897; Experimental study of light pressure, 1901; Thermoelements in the void, as a device for measuring radiant energy, 1902; Experimental study of light on gases, 1910; Magnetometric study of rotating bodies, 1911, etc. II. Popular articles and speeches: On the motion of stars according to spectroscopic studies, 1892; August Kundt, 1894; On x-rays discovered by Roentgen, 1896; Experimental work of A. G. Stoletov, 1898; Methods for obtaining high temperatures, 1899; Rock of electromagnetic waves in the ether, 1901; Advances in acoustics over the past 10 years; 1905; Russian society and Russian national laboratories, 1911; In memory of the first Russian scientist (M. V. Lomonosov), 1911; Pressure of light, 1912, etc.].

About P. N. Lebedev:Lazarev P.P., P. N. Lebedev (biographical sketch) in "Collected works." Edited by P. N. Lebedeva. Moscow, 1913. His own, P. N. Lebedev and Russian physics, "Temporary Society for Promoting the Progress of Experimental Sciences named after X. S. Ledentsov", c. 2; Charnovsky N. F., Characteristic features of the activities of P. N. Lebedev in the Council of the Society. X. S. Ledentsova, ibid.; Lazarev P.P., Lebedev laboratory at Shanyavsky University, ibid., 1913, c. one; Kravets T. P., P. N. Lebedev and the physical school he created, "Nature", 1913, No. 3 (there is a separate print); Zernov V.D., Pyotr Nikolaevich Lebedev, "Scientific Notes of Moscow University", c. LII, Physics, M., 1940; Kaptsov N. A., School of Petr Nikolaevich Lebedev, ibid.

Pyotr Nikolaevich Lebedev was born in Moscow on February 24 (March 8), 1866. Even in his youth, he became interested in physics, so he chose the Imperial Moscow Technical School for training. Without finishing it, in 1887 Lebedev left for Germany, where he worked in the laboratory of the famous physicist August Kundt. In 1891 he wrote a dissertation and passed the exam for the first degree. Returning back to Russia, Lebedev got a job as an assistant in the physics laboratory of Professor A. G. Stoletov. The results of the work performed in Kundt's laboratory formed the basis of his master's thesis, for which he was awarded the degree of Doctor of Physics. Soon Lebedev became a professor at the Imperial Moscow University. He was not limited only to research activities, but made a lot of efforts to create a scientific school, whose students in the future achieved success in the field of physics. In 1911, Lebedev left the Imperial Moscow University, along with many progressive teachers, in protest against the reactionary actions of the Minister of Education Kasso. With private funds, Lebedev created a new physical laboratory, but he was not destined to complete the research - the scientist died on March 1 (14), 1912 due to heart disease.

One of the prominent physicists of the 19th century, William Thomson, once wrote: “All my life I fought with Maxwell, not recognizing his light pressure, and now ... Lebedev made me give up before his experiments.”

According to the theory of the British physicist Maxwell, a light beam falling on an absorbing body produces pressure on it. Today, to a person who is far from physics, this statement may seem controversial, and even to confirm the theory in practice is almost impossible in general. And in the 19th century, the proof of this statement was all the more a big technical problem, but Lebedev's talent and talent helped him successfully solve the problem. The difficulty of the experiment was that the magnitude of the pressure of light, if it existed, is very small. To discover it, it was necessary to conduct an experiment that was almost filigree in execution. To do this, Lebedev invented a system of light and thin disks on a swirling suspension. One can only wonder how the scientist managed to create a torsion balance with such high accuracy of readings. However, in addition to low pressure values, another difficulty was that other phenomena interfered with its measurement. For example, when light falls on the thin disks that Lebedev used in his experiments, they heat up. As a result of the temperature difference between the illuminated and shadow sides, convection effects occur. The scientist overcame all these difficulties, demonstrating unsurpassed skill.

At first glance, the device that the physicist designed seems very simple - the light fell on a light winglet suspended on a thin thread in a glass bottle from which air was pumped out. The twisting of the filament indicated light pressure. However, behind the external simplicity, it is easy not to notice the hard work spent on its creation. The wing consisted of two pairs of platinum circles, one of which was shiny on both sides, the other was covered with platinum black.

The thickness of the platinum wings was as thin as possible, which led to instant temperature equalization and the absence of "side" effects. In addition, to exclude the movement of gas due to the temperature difference, the light was directed alternately to both sides of the winglet. In addition, the entire installation was placed in the maximum possible vacuum for that time - Lebedev added a drop of mercury to the glass cylinder with the device and heated it, as a result, air was forced out under the influence of mercury vapor with the additional use of a pump. Then the temperature in the cylinder decreased, which led to the condensation of mercury vapor and a sharp decrease in pressure. The scientist's painstaking work was rewarded, and Lebedev reported that Maxwell's theory was confirmed by his experiments. “Thus, the existence of Maxwell-Bartoli pressure forces has been experimentally established for light rays,” Lebedev ended his report on the discovery with this phrase. It is worth adding that the proven fact was of great importance for that time. And all because the reality of the existence of pressure of electromagnetic waves suggests that they have a mechanical impulse, and hence mass. This, in turn, indicates that the electromagnetic field is material. Thus, scientists have proved that matter exists not only in the form of matter, but even in the form of a field.

The next task that the physicist set himself was to determine the pressure of light on gases. This task was even more difficult than the previous one, since the light pressure on gases is many times less than the pressure on solids. A more subtle experiment was required. It took a lot of time to prepare the experience. Due to difficulties, Lebedev abandoned this venture many times, but then was accepted again. As a result, about two dozen devices were created, ten years were spent, but when the work was completed, there was no limit to the surprise of the scientific community, and the British Royal Institute elected Petr Nikolayevich as its honorary member. The difficulties that Lebedev encountered during the experiment were the same as in experiments with solids. In order for the gas temperature to be uniform, it was necessary to ensure the strict parallelism of the rays, which is impossible in principle. However, the scientist's ingenuity knew no bounds - he came up with the idea of ​​introducing hydrogen into the gas under study, which has a high thermal conductivity, which ultimately contributed to the rapid equalization of the temperature difference. All the results of the experiments of Pyotr Lebedev and other studies coincided with the value of light pressure calculated by Maxwell, which was an additional confirmation of his electromagnetic theory of light. For unique experiments and general contribution to science, Lebedev was nominated for the Nobel Prize in 1912. Einstein was among the other candidates. However, ironically, none of the great scientists received it that year: Einstein - due to the lack of experimental and practical confirmation of his theory of relativity (he received the prize only in 1921), and Lebedev - due to the fact that the prize is not awarded posthumously.