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BIOGRAPHIES OF GREAT SCIENTISTS
Lebedev Petr Nikolaevich Biography of a scientist
Directory / Biographies of great scientists
Pyotr Nikolaevich Lebedev was born on February 24 (March 8), 1866 in Moscow, into a merchant family. His father worked as a trusted clerk and treated his work with real enthusiasm. In his eyes, the trading business was surrounded by a halo of significance and romance. He instilled the same attitude in his only son, and at first successfully. In the first letter, an eight-year-old boy writes to his father: "Dear dad, are you in good health and are you a good trader?" Petya learned to read and write at home. But he could not be tied to his mother's skirt for long. A ten-year-old boy must go to school. Naturally, Petya was sent to a commercial school. More precisely, in the commercial department of the Evangelical Church School of Peter and Paul. Because German accuracy seemed to Nikolai Lebedev the basis of success. Petya really mastered it for the rest of his life, and a good knowledge of the German language was very, very useful to him later. He also knew French. However, he did not study well. In one of his letters to his father, he describes his re-examination. Petya did not get close to any of his fellow students or teachers. But a characteristic touch: by the end of his studies, he was admitted to the physics room of the school to help the teacher keep the instruments in order and prepare them for demonstrations in the classroom. Peter dreamed of a university, but they were accepted there only after graduating from the gymnasium with Latin and Greek. From September 1884 to March 1887, Lebedev attended the Moscow Higher Technical School, but the activity of an engineer did not attract him. On the advice of Professor Shcheglov, he went in 1887 to Strasbourg, to one of the best physical schools in Europe, the school of August Kundt, "an artist and poet of physics," as Lebedev would later say about him. Peter treated him with great respect and heartfelt gratitude. After his death, Lebedev dedicated a warm, heartfelt obituary to Kundt, in which he described him "not only as a first-class scientist," but also as "an incomparable teacher who cared about the future of his beloved science, forming and educating its future leaders." Kundt received Lebedev very graciously and offered to take on a cycle of experimental works in a physics workshop, accompanying them with attendance at lectures. Kundt loved and trusted Russian students: many of those who later glorified Russian science studied under him. Each of them came to him with a true desire for knowledge after unsuccessful attempts to get an education in Russia. Peter felt even more comfortable when his childhood friend Sasha Eichenwald joined them. Lebedev and Eikhenwald did so much for pre-revolutionary physics that their names will forever be among the founders of Russian and Soviet science. They will carry loyalty to science, youthful ideals and friendship throughout their lives. Moreover, Lebedev married one of the seven sisters of Eichenwald. In 1891, having successfully defended his dissertation, Lebedev became a doctor of philosophy. Already at this time, the young researcher amazes his teacher with talent, abundance and courage of ideas, the desire to work on the most difficult issues, one of which was the establishment of the nature of molecular forces, the other - the pressure of light. In 1891, Lebedev returned to Moscow and, at the invitation of A. G. Stoletov, began working at Moscow University as a laboratory assistant. But Petr Nikolayevich already had a big plan for scientific work. The basic physical ideas of this plan were published by a young scientist in Moscow, in a short note "On the repulsive force of radiant bodies." It began with the words: "Maxwell showed that a light or heat beam, falling on an absorbing body, exerts pressure on it in the direction of incidence..." was dedicated to the pressure of light. It followed from Maxwell's theory that the light pressure on a body is equal to the energy density of the electromagnetic field. Experimental verification of this proposition presented great difficulty. First, the pressure is very low and an extremely delicate experiment is needed to detect it, let alone measure it. And Lebedev creates his famous installation - a system of light and thin disks on a swirling suspension. It was a torsion balance with hitherto unheard-of precision. Secondly, the radiometric effect was a serious hindrance: when light falls on a body (thin disks in Lebedev's experiments), it heats up. The temperature of the illuminated side will be greater than the temperature of the shadow side. And this will lead to the fact that gas molecules from the illuminated side of the disk will be discarded at higher speeds than from the shadow side. There is an additional recoil directed in the same direction as the light pressure, but many times greater than it. In addition, in the presence of a temperature difference, convection gas flows arise. All this had to be eliminated. Lebedev overcomes these difficulties with the unsurpassed skill of the most skilful experimenter. The platinum wings of the suspension were taken with a thickness of only 0,01-0,1 mm, which led to a rapid temperature equalization. The entire plant was placed in the highest vacuum achievable at the time. Pyotr Nikolaevich managed to do this very witty. Lebedev placed a drop of mercury in the glass container where the installation was located and heated it slightly. Mercury vapor displaced the air pumped out by the pump. And after that, the temperature in the cylinder dropped, and the pressure of the remaining mercury vapor decreased sharply. Hard work paid off. A preliminary report on the pressure of light was made by Lebedev in 1899, then he spoke about his experiments in 1900 in Paris at the World Congress of Physicists. In 1901, his work "Experimental study of light pressure" was published in the German journal "Annals of Physics". The work was highly appreciated by scientists and became a new, brilliant experimental confirmation of Maxwell's theory. V. Thomson, for example, having learned about the results of Lebedev's experiments, in a conversation with K. A. Timiryazev said: “You may know that all my life I fought with Maxwell, not recognizing his light pressure, and now your Lebedev forced surrender to his experiments." F. Pashen wrote to Lebedev: "I consider your result one of the most important achievements of physics in recent years." To the impressive words of these prominent physicists, one can add that the proof of the existence of light pressure was of great philosophical and ideological significance. After all, from the fact of the existence of pressure of electromagnetic waves, a very important conclusion followed that they have a mechanical impulse, and hence mass. So, the electromagnetic field has momentum and mass, that is, it is material, which means that matter exists not only in the form of matter, but also in the form of a field! In 1900, while defending his master's thesis, Lebedev was awarded the degree of Doctor of Science, bypassing the master's degree (a rare case in the history of science). In 1901 he became a professor at Moscow University. So for ten years of work, the path from a laboratory assistant to a professor, world-famous for his scientific works, was passed. In 1902, Lebedev made a report at the congress of the German Astronomical Society, in which he again returned to the question of the cosmic role of light pressure. In a historical review of this report, Lebedev recalls the hypothesis of Kepler, who suggested that the repulsion of cometary tails by the Sun is due to the pressure of its rays on tail particles. The action of light on a molecule, Lebedev points out, depends on its selective absorption. For rays absorbed by a gas, the pressure is due to Maxwell's law; rays that are not absorbed by the gas have no effect on it. Lebedev sets the task of determining the pressure of light on gases. On his way there were difficulties not only of an experimental, but also of a theoretical nature. The difficulties of the experimental plan were that the light pressure on gases is many times less than the pressure on solids. This means that an even more subtle experiment is needed. By 1900, all the preparatory work for solving the most difficult task had been completed. Lebedev persistently continues to look for ways to solve it. And only in 1909 he makes the first report on the results obtained. In ten years of painstaking work, at least twenty instruments were built; according to Lebedev, monstrous difficulties had to be overcome, because of which he quit this work many times. The work shocked the scientific world with its skill and result. Lebedev accepts congratulations full of surprise and admiration for his art of experimentation. The Royal Institute of England elects Peter Nikolaevich as its honorary member. The results of this study were published in the Annals of Physics in 1910. In order for the gas temperature to be the same everywhere, it was necessary to ensure strict parallelism of the rays, otherwise strong convection currents would arise. It is impossible to obtain strictly parallel rays. The scientist finds an ingenious solution: he introduces a little hydrogen, which has a high thermal conductivity, into the gas under study. Therefore, the temperature differences quickly equalize. To get rid of the radiometric effect, a camera with two channels was used in the experiments. In addition to works related to light pressure, Petr Nikolayevich did a lot to study the properties of electromagnetic waves. Lebedev's article "On the double refraction of rays of electric force" appeared simultaneously in Russian and German. At the beginning of this article, Lebedev briefly outlines its purpose and content: “After Hertz gave us methods to experimentally verify the consequences of the electromagnetic theory of light and thus opened up an immeasurable area for research, there naturally arose a need to carry out his experiments on a small scale, more convenient for scientific research ... " Having improved Hertz's method, Lebedev obtained the shortest electromagnetic waves at that time with a length of 6 mm (in Hertz's experiments they were 0,5 m) and proved their birefringence in anisotropic media. It should be noted that our scientist's instruments were so small that they could be carried in a pocket. For example, Lebedev's electromagnetic wave generator consisted of two platinum cylinders, each 1,3 mm long and 0,5 mm in diameter. Lebedev's mirrors had a height of 20 mm, and an ebonite prism for studying the refraction of electromagnetic waves was 18 mm high, 12 mm wide and weighed about 2 g. Recall that the Hertz prism for the same purpose weighed 600 kg. Lebedev's miniature instruments have always aroused the admiration of experimental physicists. Lebedev was deeply interested in the problems of astrophysics, actively worked in the International Union for the Study of the Sun, wrote a number of articles on the apparent dispersion of the interstellar medium. Hale's discovery of sunspot magnetism directed his attention to the study of rotational magnetism. In the last years of his life, the problem of ultrasound attracted his attention. These questions were dealt with by his students V. Ya Altberg and N. P. Neklepaev. Lebedev himself wrote a note "The Limiting Value of Short Acoustic Waves". His students P. P. Lazarev and A. K. Timiryazev investigated the phenomenon of internal friction in rarefied gases. Lebedev generally had many students. If in the first half of the nineties their number was measured in units, then by 1905 there were more than thirty of them: P. P. Lazarev, V. K. Arkadiev, S. I. Vavilov, T. P. Kravets, A. K. Timiryazev and many others. Having learned the methods and style of work of their teacher, they continued his noble work. The successes of Russian physics owe much to Lebedev's school. To lead a scientific school, one must have not only organizational skills, but also be an exceptionally erudite and versatile scientist. Such was Lebedev. Conscious of his excellent abilities as an experimenter, Lebedev drew one conclusion from this: he must solve the most complex problems and work to the limit of his strength. He was a scientist with a high sense of civic duty to his homeland, to his students. In 1911, Lebedev, along with other professors, left Moscow University in protest against the actions of the reactionary Minister of Education Kasso. In the same year, Lebedev twice received invitations from the Nobel Institute in Stockholm, where he was offered the position of director of an excellent laboratory and a large amount of money, both for work and for personal use. The question of awarding him the Nobel Prize was even raised. However, Pyotr Nikolaevich did not accept this proposal, he remained in his homeland, with his students, creating a new laboratory at private expense. The lack of necessary conditions for work, the feelings associated with resignation, finally undermined Lebedev's health. He died on March 1 (14), 1912, at the age of only forty-six. K. A. Timiryazev responded to Lebedev’s death with pain from a huge loss and passionate indignation at the existing order, dreaming of the time when “people with a mind and heart” will finally have the opportunity to live in Russia, and not just be born in her to die with a broken heart." The great Russian physiologist Pavlov telegraphed: "With all my heart I share the grief of the loss of the irreplaceable Pyotr Nikolaevich Lebedev. When will Russia learn to take care of its outstanding sons - the true support of the Fatherland?" Lebedev entered the history of physics as a first-class experimenter who solved a number of the most difficult problems of modern physics. Author: Samin D.K.
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