Memories of Pyotr Nikolaevich Lebedev

N. A. Kaptsov

Pyotr Nikolaevich Lebedev—when I pronounce this dear name, my heart begins to beat more vividly, pictures of distant youth rise before my eyes, and a swarm of memories presses into my head.

The beginning of 1902. One of the rooms in the premises of the physical (Stoletov) practicum on the second floor of a small two-story house in the courtyard of the old University building, entirely filled with tables bearing the “tasks” of the practicum. Part of this room is partitioned off by a curtain of black cloth. Three o’clock in the afternoon. The last second-year students who have lingered in the practicum are getting ready to leave. A bell rings in the front hall; a neatly built, tall man in a civilian suit passes through the room and disappears behind the curtain. This is Pyotr Nikolaevich Lebedev, who has come to work in his small laboratory. The laboratory attendant Maksim comes in to him. A few minutes later one hears Pyotr Nikolaevich giving Maksim instructions for setting up some apparatus, loudly naming the division on the scale. Such is the first memory.

The second: the same room, the same time of day. Lebedev passes through. One of the students turns to him with a request to be given a topic for a so-called “essay,” obligatory under the curriculum. The answer: “I do not give topics for essays. But if you want to work in physics, then come when you have finished the general practicum.”

The third: the same student is doing, in the “chemistry room,” one of the final tasks of the practicum: determining the electrochemical equivalent of copper. Lebedev comes through from the library room, stops, and begins questioning in the most detailed way: what are you determining, what is happening in this experiment, and so on. All the questions are to the point and directed, as the youth of that time realized much later, toward discovering whether this young man is capable of making sense of questions of physics. But now the practicum has been completed. The topic for an “essay” has been received from Professor A. P. Sokolov, who is teaching the general physics course. Together with this topic, a topic for experimental

“special work.” But at the very first interview, Lebedev, who was in the room, tells Sokolov that this student had already approached him earlier and would work with him, and at once gives him the first interesting assignment: to reproduce familiar optical phenomena with the aid of waves on the surface of water.

After a month or two, having inspected the demonstration of the experiments that had been set up, Petr Nikolaevich revealed the content of the principal topic: to measure the pressure of waves propagating over the surface of water upon bodies that absorb and reflect them. He spoke vividly and engagingly about the cycle of work he had conceived on the pressure of waves of various kinds. How to arrange reflection from walls and how to create a body absorbing waves he had already indicated earlier: one had to imitate the breaking and extinction of waves on a gently sloping seashore. It is impossible, of course, to recount here all the episodes, preserved in memory, of Petr Nikolaevich’s supervision of the work. But some of them cannot go unmentioned.

In preliminary experiments it became clear that, in the very surface layer of water along which the waves ran, there existed a current in the direction of propagation of the waves. Such a current, by itself, had to exert pressure on bodies floating on the surface of the water. This additional pressure had to be allowed for; and in order to allow for it, it had to be measured at the same velocity of current, but in the absence of waves.

Petr Nikolaevich proposed placing on ball bearings a flat-bottomed round basin capable of rotating, rotating it, and measuring the deflection of a body partly immersed in the water and suspended like a pendulum. The apparatus was assembled. It had to be put into operation in the presence of Petr Nikolaevich himself. And suddenly, astonishment and disappointment: the basin began to rotate, but there was no water in it. Petr Nikolaevich at once explained that, if one had thought before beginning the experiment, one could have said in advance that this would happen: the rotating round wall and bottom would gradually, by internal friction, set the water in motion. Fortunately for the experimenter, the latter quickly hit upon the idea of placing along the diameter of the comparatively slowly rotating basin a thin partition and quickly removing it once the rotation of the basin had become established; and Petr Nikolaevich was reassured.

In 1904 the construction of the building of the Physical Institute on Mokhovaya was completed. For the work of the young physicists under his direction, Petr Nikolaevich selected a semi-basement room: the subsequently famous Lebedev basement. I distinctly remember Petr Nikolaevich—vigorous, cheerful, filled with faith in the success of his school—when he first brought six or seven of us into the new laboratory to show each person the room in which he would work.

He interspersed his words with jokes, praising the room, which was bright and spacious, unlike the old practicum, where it had been very cramped and rather dark. “Here is a room for your work, where there is a great deal of argon,” he jokingly addressed one of his then pupils (Kotovich), and, seeing his perplexity, explained: “After all, in this large and high room there is much air; consequently, much argon as well.” From that day research work began in Lebedev’s basement.

Every day at about 11 o’clock in the morning, Petr Nikolaevich would come by cab from his apartment on Maroseika to the University on Mokhovaya, go down into the basement, begin making the rounds of the laboratory rooms, and talk with those working there. He made no distinction between a student just embarking on research work for the first time and a person who had already been engaged in it for several years. He demanded from each of his pupils a conscious account of everything that had been done since the previous conversation. Sternly, at times even very sharply, he would reprimand them for mistakes made and steps insufficiently thought through. But he did this out of affection and for the benefit of the person being taken to task, and therefore there was no possibility of taking offense at him.

Petr Nikolaevich demanded, above all, that each of us think through the plan of his work rigorously. But a plan, in Lebedev’s understanding, was not to be something rigid and fixed once and for all, but active and alive. It often happened that, in the course of the work, new and unexpected details became clear and new questions arose; Petr Nikolaevich would propose a new direction for the work, one promising new, far-reaching prospects. A multitude of fresh thoughts would at once come to his mind. He himself would become carried away by them and would draw broad horizons before the beginning researcher, infecting his interlocutor with his enthusiasm. And one felt not the slightest regret for the labor already done, which was now to a considerable extent going to waste. Listening to him at such moments, one wanted only one thing: to work, to work without fatigue, in constant communication with him.

Petr Nikolaevich was especially demanding not only when he allowed a work to be considered finished and ready for submission to print, but even when it was only a matter of a report at the weekly colloquium he directed. He demanded good execution of the work both in literary and in illustrative form. At his direction, the text of his pupils’ first articles was reworked by each of them several times. It would even happen like this: “All this is good,” he would say, looking through the third or fourth version of an article, “you have carried out my instructions, but the detailed treatment of the question that I demanded from you was needed only for you, not for the reader. Cross out this part and in general shorten the article.” Long articles

Pyotr Nikolaevich did not overlook them. He believed that, with the ever-increasing number of works being published in physics, these articles would not find readers. His instructions were never abstract. He himself would sketch out for the beginner the plan of an article, the introductory phrases to individual sections of the text, and drafts of drawings.

It is hard to say what was dearer to Pyotr Nikolaevich: his own works or the works of his students. Pyotr Nikolaevich’s cherished dream was to pass on to his students his enormous research experience and his ability to think scientifically and creatively, to train from among them scholars who would advance physics and be capable of satisfying the needs of the country’s technology and national economy. More than once he said: “Work as I am teaching you; do not think about what this is needed for now—the time will come when physicists in Russia will be needed and will find application for their abilities.”

Pyotr Nikolaevich warned against accepting on faith, as the starting point of research, what is written in thick textbooks. He did not like the latter in general, believing that much is set forth in them in simplified form, as an indisputable truth, whereas in reality a number of questions are still very far from being solved and require investigation. Therefore he always demanded that one turn to the primary sources and analyze them. Pyotr Nikolaevich placed a high value on the connection between science and technology; when a power station was opened in Moscow on Raushskaya Embankment, he took a group of his students to inspect it, and on the spot personally explained its construction and mode of operation, turning to the engineers servicing the station only for clarification of certain technical details.

Such, in the recollections of the author of this note, was Pyotr Nikolaevich Lebedev—as an unforgettable teacher and mentor. Immeasurably great was the charm of the luminous personality of this man—not only a brilliant scientist, who combined exceptional depth of scientific thought with the extraordinary skill of an experimenter, but also the head of a scientific school who ardently loved his students. He not only advanced science as no one else did, but also with all his strength drew the younger generation into his work, striving to create continuators of his cause.

The successes achieved at the present time in the Soviet Union by physics and by a number of closely related branches of technology, and the creation of the personnel necessary for this, owe much to those seeds that were sown by Pyotr Nikolaevich Lebedev—the pioneer of great collective scientific-research work in physics in our country. In the favorable conditions of the great Stalin era, these seeds have yielded abundant shoots.