Kapitsa (or Kapitza), Petr Leonidovich

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(b. Kronstadt, Russia, 8 July 1894; d. Moscow, U.S.S.R, 8 April 1984),

physics of low temperatures, solid-state physics, engineering.

Kapitsa contributed to the development of low-temperature physics. His 1930s studies on liquid helium earned a Nobel Prize (1978). An enigmatic figure, he served as a symbol of science in the Soviet Union during the Stalin era and beyond. He had an international reputation, living much of his early career in England, yet was not permitted in 1934 to return to his laboratory in Cambridge where he had worked with Ernest Rutherford for a dozen years, and nearly abandoned his career. He rose to the top of the physics establishment, yet fell under house arrest in Moscow in the late 1940s. He protected such leading Soviet physicists as Vladimir Fock and Lev Landau from almost certain death during the Great Terror in the 1930s, risking his own career to do so, and became a central figure of the conservative scientific establishment in the 1960s. Over the years, Kapitsa wrote dozens of letters to Joseph Stalin, Vyacheslav Molotov, and other Soviet leaders, and to his wife when separated from her. These letters, many of which have now been published in Russian and English, provide an excellent insight into the career and mindset of Kapitsa. In many ways, Kapitsa’s career serves as a microcosm of Soviet physics, where gifted scientists had to maneuver through a number of pitfalls, political perils, international isolation, and a low level of industrial support for research.

Early Years . Kapitsa was born to a well-to-do family. His father was a military engineer, his mother a specialist in children’s literature and folklore. He studied in a classical gymnasium without great success, then a Realschule from which he graduated with honors, and entered St. Petersburg Polytechnical Institute in 1912. The war found him in Scotland, and when he returned to Russia he served as an ambulance driver. Before the war’s end he returned to the institute, where he met Abram Ioffe. Ioffe, a specialist in x-ray crystallography and physics of the solid state, was a leading organizer of the nascent discipline of physics in the czarist empire. He had recently established a seminar in which a number of future luminaries of Soviet physics including future Nobel laureate Nikolai Semenov and the theoretician Yakov Frenkel, and others participated.

Just after the Russian Revolution, Kapitsa joined Ioffe’s newly founded Leningrad Physical Technical Institute, located across the street from the Polytechnical Institute. The Ioffe institute became known as the “cradle” of Soviet physics. A number of physicists who later established their own research centers and leading schools of research, won state prizes, and several who became Nobel laureates began their careers at Ioffe’s institute. Revolution and civil war put heavy burdens on Petrograd, science, and especially on the middle and upper classes. The city lost hundreds of thousands of people to death, disease, and emigration. Kapitsa, his father, wife, and two children struggled to survive. Food and fuel were in short supply, starvation and epidemics broke out, and Kapitsa lost his father, wife, and children. In spite of broad social and personal turmoil, Kapitsa managed to conduct a few original investigations during this time on angular momentum associated with magnetization and x-ray crystallography, a technique in which a pattern produced using diffusion of x-rays through a crystal is recorded to reveal the crystal’s structure.

Ioffe was both an institute builder and an ambassador of science who helped reestablish contacts with western scientists after World War I and the revolution. He journeyed abroad several times with scarce hard currency

acquired from the Bolshevik government in order to obtain various apparatuses and reagents and renew subscriptions to foreign journals. Ioffe invited Kapitsa on a trip in 1921, in part to help Kapitsa recover from his great personal losses. During the first stages of the trip, while Ioffe was in Berlin, he secured a visa for Kapitsa to travel to England, other nations having refused to grant a visa to someone from the young revolutionary Soviet regime. There were few places where someone of Kapitsa’s interests in the physics of crystals and of low temperatures might study abroad: Leiden, Netherlands (where the theoretician Paul Ehrenfest, a longtime acquaintance who had studied in St. Petersburg, had settled), Berlin, and Cambridge, England.

Rutherford’s Cavendish Laboratory . Kapitsa was intrigued by the possibility of visiting Rutherford’s Cavendish Laboratory in Cambridge. His first meetings with the formal Rutherford were difficult, but they became close over the years. According to an apocryphal story, Rutherford initially turned down Kapitsa’s request to work with him, saying his laboratory was already too crowded with thirty scientists. Kapitsa then asked what accuracy Rutherford aimed at in his experiments. The startled Rutherford replied within 2 or 3 percent. Kapitsa responded that adding one more researcher to the laboratory would not be noticed since he would fall within experimental error. Kapitsa stayed in Cambridge from July 1921 until 1934; during this time he traveled widely in Europe and was a part of the international physics community.

From the start, Kapitsa impressed Rutherford with his ability to select research problems and his experimental acumen. Kapitsa’s first research concerned “The Loss of Energy of an Alpha-Ray Beam in Its Passage through Matter,” which involved the study of the velocities of alpha particles by measuring the curvature of their tracks in a magnetic field. The findings were published in the Proceedings of the Royal Society. Existing magnets were unable to produce large enough fields to curve the tracks. Kapitsa’s idea was to use fields that were much larger but lasted a very short time. Kapitsa frequently used impulsive magnetic fields in the study of the solid state and low temperature and employed specially designed cloud chambers to track the particles. Kapitsa became more and more adept at producing higher magnetic fields with his impulsive field technique. The idea was to design a large dynamo that could generate very high power for a short time through a coil and thus produce a very powerful field. Toward this end, Kapitsa had to design a switch that opened and closed synchronously with the dynamo cycle, while the coil had to be strong enough to withstand very powerful fields.

Kapitsa and Rutherford had a formal relationship built on mutual respect and eventually deep friendship. Kapitsa may have been one of the few people who could joke around Rutherford, although initially Rutherford’s insistence on doing things only his way, and Kapitsa’s independence, left them acting coldly toward one another. Kapitsa awarded Rutherford the nickname “Crocodile.” Contemporary observers and Kapitsa’s own letters suggest a variety of reasons why Rutherford earned the name, but it was most likely owing to the initial fear that young scientists had for the imposing Rutherford. Eventually, however, Crocodile became a term of endearment. The Mond Laboratory, established with a grant in 1930 to house Kapitsa’s high-field and cryogenic equipment, carries a crocodile etched on its outside wall.

In January 1923 Cambridge admitted Kapitsa as a PhD student. He earned the degree in summer 1923 (in part based on the already completed research) and was also admitted as a Fellow at Trinity College. He later became assistant director of Magnetic Research at Cavendish and then was elected a Fellow of the Royal Society in 1929. In Cambridge, perhaps missing the engagement of Ioffe’s Polytechnical seminar, Kapitsa organized the Kapitsa Club, which ran for over forty years. At the weekly seminar participants discussed papers in an informal setting. One could attend and remain a member of the club only by giving a talk from time to time. The minutes and guest book of the club are a fascinating source of the history of twentieth-century physics. Dozens of leading scientists presented at the club on central issues of modern physics, including Paul Dirac, John Chadwick, and Landau. When Kapitsa was forced to remain in the U.S.S.R. in 1934, his British colleagues continued the meetings in his honor, although with some interruptions. When, in May 1966, Kapitsa was permitted to visit Cambridge again, the Kapitsa Club met one last time with Dirac and Kapitsa speaking. Kapitsa’s Moscow seminar continued the tradition for Soviet physicists.

Kapitsa was an excellent experimentalist, a skilled engineer, and a handy inventor who produced most of the apparatus needed for his research. Unlike in the U.S.S.R., the Cavendish laboratory had the material that Kapitsa needed. He demonstrated his organizational and engineering skills when in 1925 he earned a large, British government grant (with Rutherford’s support) to build a dynamo for the production of high magnetic fields. He studied how the electrical resistance of metals increases with magnetic field, a phenomenon known as Kapitsa’s law of magnetoresistance, magnetization of various substances, and magnetostriction. He turned to the construction of a device to liquefy helium to pursue this study, and had great plans to expand his research program and facilities.

Although Kapitsa did not supervise many students directly, either in Cambridge or in Moscow, while working at the Mond Laboratory Kapitsa succeeded in finding short-term fellowships for such Soviet colleagues as nuclear specialists Aleksandr Leipunskii, Kirill Sinel’nikov, Soviet hydrogen bomb specialist and one of the designers of the atomic bomb Yuli Khariton, and theoretician Lev Landau. Some of the funds for the fellowships came from the Rockefeller Foundation’s International Educational Board. Kapitsa always remained convinced that science was an international endeavor.

Superfluidity and Stalinist Rigidity . In summer 1934, during his annual summer trip home to Russia, the authorities refused to permit Kapitsa to return to England, although they permitted his Russian wife, Anna Alekseevna Krylova (daughter of the engineer Aleksei Krylov), to leave the country with their two sons. (He had remarried in 1927.) Unlike George Gamow, who managed to get a visa for a foreign conference and never returned to the U.S.S.R., and Vladimir Ipatiev, a member of the nobility and leading chemist who served the Bolshevik regime for over a decade before quitting the U.S.S.R. for life in America, Kapitsa would not be permitted to escape.

The Soviet government claimed that Kapitsa was needed for its industrial programs, alternately suggested he was involved in inappropriate military work in England, and also pressured him to remain by suggesting that he was not a patriot. Some Communist Party officials may also have detested Kapitsa over his enjoyment of British academic life, its formal teas, and the bourgeois lifestyle generally, even though Kapitsa was not a natty dresser. Kapitsa relaxed by motorcycling and driving a Triumph and a Vauxhall automobile. Lev Kamenev, a Bolshevik administrator, and perhaps Ioffe and Nikolai Bukharin (who was head of the Scientific-Technical Department of the Supreme Economic Council), had already approached Kapitsa about working as a consultant at the newly established Kharkov Physical Technical Institute in Kharkov. In any event, Kapitsa would be forced to stay.

Over the next two years, Dirac, Niels Bohr, Rutherford, and several other scientists attempted to secure Kapitsa’s freedom to resume his work in Cambridge. They hesitated to do so publicly, preferring to work behind the scenes. Kapitsa’s mood deteriorated. He grew isolated from his colleagues, some of whom in fact resented his English sojourn, and he was followed by the secret police. Initially, Kapitsa refused to do research for the Soviet state, and considered leaving physics, perhaps for physiology and biophysics working with Ivan Pavlov. Ultimately, however, Kapitsa began to think of doing research again, and he seems to have convinced Soviet leaders that his studies could not resume unless he acquired the equipment he had specially designed for the Mond Laboratory.

Eventually the Soviet and British authorities, with some assistance from the physics community, agreed to transfer Kapitsa’s Mond Laboratory to Moscow for thirty thousand pounds. The equipment arrived from England in 1936 and was installed in the new institute created by and for Kapitsa, the Institute of Physical Problems. The authorities relaxed their surveillance of him and also assigned him a nice apartment, provided him with access to good stores and theater tickets, and even gave him an automobile. Kapitsa was able to produce liquid helium for experiments again early in 1937. With the opening of the institute, Kapitsa returned to full-time research on low-temperature physics, although he was often frustrated by the stark change in his situation and the heavy-handedness of the authorities. The Institute of Physical Problems was small by Soviet standards with only seven scientists in 1937, but its stellar researchers included Landau, among others. It grew to around fifty leading researchers and some two hundred personnel. Anna Kapitsa and the children came to Moscow in January 1936.

The Institute of Physical Problems itself is a lovely oasis in the center of Moscow, just 8 kilometers from the Kremlin, located behind tall, thick walls just off what is now Gagarin Square. The institute’s comfortable buildings include an auditorium, dining hall, buffet, and well-equipped library. The buildings for the various departments, laboratories, and machine and glass-blowing shops sit on quiet, tree-lined streets. Kapitsa insisted on creating space for a garden, tennis court, and small park that dropped down toward the Moscow River. The institute became known for weekly seminars, built on the model of the Kapitsa Club in Cambridge, which became a scientific and cultural institution of the physics community and drew leading scholars from around Moscow to discuss important issues.

The entire Kapitsa affair indicates one of the trademarks of science in the Stalin period: the drive to create autarky. Few foreign scientists managed to visit the U.S.S.R. until the Khrushchev period, and fewer Soviet scientists were permitted to travel abroad. Foreign journals were censored, reaching the libraries of institutes after delays of nine months and longer. Scientists were denied the right to send reprints abroad or to publish in foreign journals without getting permission from an increasingly bureaucratic administration.

In 1937 Kapitsa discovered the superfluidity of liquid helium for which he won his Nobel prize. Kapitsa built on the work of a number of specialists studying low temperatures. Heike Kamerlingh Onnes of the Netherlands sought to liquefy gases at low temperatures. He used various apparatuses to produce liquid helium in 1908 and establish its boiling point at 4.2 K. Onnes received the Nobel prize in 1913 for this and other low temperature researches. Subsequently, Onnes and others discovered that liquid helium exhibits odd behavior. By 1924 Onnes had measured liquid helium’s density, and determined that as the temperature lowers, the density goes through a sharp maximum at about 2.2 K. In 1927 Willem Keesom and Mieczyslaw Wolfke concluded that that liquid helium undergoes a phase transition at that temperature of roughly 2.2 K (now established at 2.18 K or –270.97 C). This temperature is called the lambda point because the graph of specific heat versus temperature resembles the Greek letter lambda. The two phases are called helium I and helium II. Kapitsa’s contribution was to show that helium II was a superfluid.

While investigating the thermal conductivity of liquid helium, Kapitsa measured the flow as the fluid flows through a gap between two discs into a surrounding bath. Above the lambda point, there was little flow, but below the lambda temperature, the liquid flowed with such great ease that Kapitsa drew an analogy with superconductors. It was a liquid of zero viscosity. He discovered the phenomenon in 1937 and published a paper about it in Nature in January 1938. He wrote: “The helium below the lambda point enters a special state that might be called a ‘superfluid.’”

Superfluids have the unique quality that all their atoms are in the same quantum state; they all have the same momentum, and if one moves, they all move. The best known superfluids are the two isotopes of helium,3 He and 4 He. Superfluids move without friction through the tiniest of cracks, apparently defying gravity. If placed in an open container, the superfluid will rise up the sides and flow over the top. If the container is rotated from stationary, the fluid inside will never move. If light or other energy is introduced into a container of a superfluid, and there is an aperture at the top, the fluid will shoot out of the aperture.

At the same time, Kapitsa worked closely with industrial leaders to develop and manufacture devices for the production of liquid oxygen, in part for industrial uses. Kapitsa wanted to cheapen and simplify the large-scale production of liquid oxygen. Kapitsa proposed using an expansion turbine to cool air to its liquefaction temperature. His first machine delivered roughly 30 kilograms per hour with a short startup time and lower expenditure of energy than conventional machines. He patented the design of a turbine motor that overcame instabilities of very high rotation. Liquid oxygen is a powerful oxidizing agent, which means that organic materials will burn rapidly in liquid oxygen. It has therefore found use in rocket fuel. It also has medical applications, for example, in portable oxygen tanks, as well as on jet airplanes and in submarines. His relations with industry and political leaders grew strained during these activities, even though, while in evacuation in Kazan during World War II, he managed to set up a large-scale pilot plant.

Kapitsa wrote and saved a voluminous number of letters to his mother, to his wife, and to Soviet leaders. He continued writing them during both the initial period of his detention and isolation in the U.S.S.R. and after he had returned to work at the Institute of Physical Problems. His letters to officials in the commissariats of Education and of Heavy Industry, the Supreme Economic Council, and other bureaucracies, and to such leaders as Stalin and Molotov, described at length his view of how science ought to be funded and organized and criticized the way that the Soviet government saw things. One theme concerned international isolation. Another concerned the slow progress on opening his institute. Kapitsa also intervened personally through his letters, and perhaps at risk to himself, to save two theoreticians, Fock and Landau, who had been arrested during the Great Terror. Landau, who had escaped arrest in Kharkov, Ukraine, in 1937 by taking a position at Kapitsa’s institute, was arrested in Moscow in 1938 and spent over a year in jail before being released to Kapitsa’s custody. Landau nearly died in prison; Fock’s 1937 ordeal ended after a few days.

A last theme was the government’s heavy-handed administration of science to foster more rapid assimilation of scientific achievements into the economy. Kapitsa often invoked metaphors drawn from classical music to describe the treatment of Soviet science by know-nothing administrators. He likened science to a symphony, something that could be written with inspiration, but never according to orders from above. Kapitsa characterized the efforts of industrial ministers to force the pace of science as the equivalent of playing a violin with a hammer. Soviet science was too highly bureaucratized, Kapitsa believed, to compete with Western science.

During World War II scores of institutes, factories, and other strategic facilities were broken down, put into cases and boxes, and placed on railway cars for evacuation just ahead of rapidly advancing German armies. Kapitsa’s institute was evacuated to Kazan from 1941 to 1943.

Kapitsa became closely involved with the Soviet atomic bomb project. He was critical of its administration, in particular its direction under secret police chief Lavrenty Beria, and the path chosen by the project leaders: to follow the U.S. lead rather than seek another, perhaps more original solution. He continued his extensive letter-writing campaign concerning what he perceived as organizational and directional problems, and subjected even Beria to hostile comments. His discontent with industry concerning oxygen-production equipment also flared. After these letters, Kapitsa was removed not only from any involvement in the project but also as director of his institute.

Again Kapitsa fell essentially under house arrest. He spent from 1946 until 1954 at his summer home in the Nikolina Hills, or Nikolina Gora in Russian, trying to get some research done. From time to time he gave talks in Moscow, but he mostly spent his efforts on putting together a small personal laboratory at what some called the Izba (for peasant hut, not Institute) of Physical Problems. Kapitsa worked on ball lightning and on the development of powerful high-frequency microwave generators (magnetrons). Anatolii Aleksandrov, another physicist who began his career in the Ioffe institute, who later became the president of the U.S.S.R. Academy of Sciences, was appointed director of the Institute of Physical Problems during this interregnum in Kapitsa’s career. A number of physicists criticized Aleksandrov for accepting the directorship, but not Kapitsa, and certainly there was little choice in the matter in Stalin’s Russia.

Statesman of Science . After Stalin’s death in 1953, Kapitsa resumed direction of the Institute of Physical Problems after Landau led a campaign involving the nation’s leading physicists to appeal to Georgii Malenkov, who succeeded Stalin for two years as premier, though only briefly wearing the additional mantle of party chief. (The latter role was assumed almost immediately by Nikita Khrushchev.) During this time, the weekly scientific seminar (the “Kapichnik”) grew in importance, and Kapitsa became a senior statesman of Soviet science. Even when other institutes began to outdistance Kapitsa’s in terms of equipment and research possibilities, the discussions at the Institute of Physical Problems remained a major institution of Soviet physics. During the reformist Khrushchev years (1955–1964) and the conservative Brezhnev era (1964–1983), Kapitsa contributed to the rapid growth of the scientific establishment as a member of the elite Soviet Academy of Sciences. Roughly speaking, the academy was the bastion of basic research, while universities provided young scientists to staff academy institutes, and industrial research was the province of ministerial institutes.

A bureaucratic separation between research, education, and industry plagued Soviet science. Kapitsa was one of the organizers of the prestigious new Moscow Physical Technical Institute (founded in 1946 as a department of Moscow University), which was formed to train and ensure a steady stream of promising young scientists into physics and engineering. In 1950 or 1951, Kapitsa was dismissed from teaching at the institute for his lack of loyalty to the regime.

Kapitsa’s major achievements in the postwar years concerned the reestablishment of scientific contacts with the West, expansion of publication, and the popularization of science. In the 1950s, Kapitsa worked actively to permit Soviet scholars to travel abroad for conferences, while inviting foreign scientists to the U.S.S.R., and cooperated with such centers as Bohr’s Institute of Theoretical Physics toward this end. But only in 1965 was Kapitsa himself allowed abroad again to visit Copenhagen to receive the Niels Bohr Gold Medal, and in only 1966 did the authorities permit him to return to Cambridge to receive the Rutherford Medal. He was long-term editor of the Journal of Experimental and Theoretical Physics. Kapitsa addressed the issue of how to improve the organization of increasingly bureaucratized and moribund science in a series of papers, but little came of his ideas or those of other senior statesmen. In addition to his Nobel Prize, Kapitsa won Stalin Prizes in 1941 and 1943, Orders of Lenin in 1943 and 1944 for his oxygen work, and the title Hero of Socialist Labor, and was elected corresponding member of the Soviet Academy of Sciences in 1929 and full member in 1939.

In his Nobel Prize speech, Kapitsa chose not to address his work on the physics of low temperatures, a field he acknowledged having left thirty years earlier, but his work and that of his institute on fusion (controlled thermonuclear synthesis). Kapitsa saw nuclear power as a solution to eventual shortages of fossil fuels, and believed that wind, solar, and hydroelectric power were also possibilities. He worried about waste and proliferation problems associated with nuclear fission, and thus pursued fusion. He mentioned pioneering Soviet efforts in the tokamak design for a fusion reactor. He then described a novel approach for heating the plasma to a sufficiently high temperature in order to fuse nuclei. This was to use a high-power continuous wave (CW) microwave generator called a “Nigotron.” Kapitsa noted that the CW microwave generator was not invented with thermonuclear reactors in mind, but that, in its development, he and his colleagues discovered the hot plasma phenomenon.

Absent-minded, a joke teller, unconcerned about personal appearance, charming, and cheerful, at times moody, boastful, and self-confident, as his letters to the Kremlin leadership reveal, Kapitsa was an imposing figure. As laboratory leader, he argued that work must stop at 6 p.m., except by special permission, to allow time for reflection, and he insisted upon open disputation of results.

Kapitsa was deeply involved in important social issues for the last two decades of his life. He publicly denounced endemic anti-Semitism in the U.S.S.R.; he criticized the objectionable science and methods of Trofim Lysenko, who dominated Soviet biology after rejecting genetics; and he defended physicist and dissident Andrei Sakharov in discussions of whether to expel the latter from the Academy of Sciences. According to several sources, he pointed out at a Presidium meeting that Albert Einstein had left the Prussian Academy under duress after the rise of the Nazis. This put an end to suggestions that Sakharov be expelled. Kapitsa contributed regularly to Pugwash discussions over arms control. In March 1984, Kapitsa suffered a severe stroke, and he died on 8 April 1984.


Archival material can be found in the archives of the Institute of Physical Problems, the Ioffe Physical Technical Institute, and the Russian Academy of Sciences (personal fund of P. L. Kapitsa).


“Viscosity of Liquid Helium Below the Λ-point.” Nature 141 (1938): 74.

“Expansion Turbine Producing Low Temperatures Applied to Air Liquefaction.” Journal of Physics of the USSR 1 (1939): 7.

Collected Papers of P. L. Kapitza, 4 vols. Edited by D. ter Haar. New York: Macmillan, 1964–1986.


Badash, Lawrence. Kapitsza, Rutherford and the Kremlin. New Haven, CT: Yale University Press, 1985.

Boag, J. W., P. E. Rubinin, and D. Shoenberg, comps. and eds. Kapitza in Cambridge and Moscow. Amsterdam: North Holland, 1990.

Esakov, Vladimir Dmitrievich. Kapitsa, Kreml i nauka: v dvukh tomakh. Moscow: Nauka, 2003.

Kapitsa, E. L., and P. E. Rubinin, comps. Petr Leonidovich Kapitsa. Vospominaniia, Pis’ma, Dokumenty. Moscow: Nauka, 1994.

Rubinin, P. E. Pis’ma o Nauke. Moscow: Moskovskii Rabochii, 1989.

Paul Josephson