Pyotr Leonidovich Kapitsa

Russian physicist and inventor

• Born: July 9, 1894
• Birthplace: Kronshtadt, Russian Empire (now in Russia)
• Died: April 8, 1984
• Place of death: Moscow, Soviet Union (now in Russia)

Kapitsa was both an experimental physicist and a brilliant designer of investigative and industrial equipment. As a tribute to the importance of his research at very low temperatures, he was awarded a Nobel Prize in Physics for his discovery of the superfluidity of liquid helium and for his invention of apparatuses for the liquefaction of helium and air.

Early Life

Pyotr Leonidovich Kapitsa (PYOH-tehr lyih-ehn-YEED-ehv-yihch KAHP-yeet-sah) was born into a family with a strong intellectual background. His father was a military fortifications engineer, and his mother was a well-known member of literary circles in nearby St. Petersburg who specialized in folklore and children’s literature. Following his early education in Kronshtadt, Kapitsa studied at the Petrograd Polytechnical Institute under the famous physicist Abram Joffe. In 1914, his academic life was interrupted by World War I, and he spent two years as an ambulance driver at the Polish front. He then returned to the Polytechnical Institute and was graduated in 1918 amid the chaotic conditions accompanying the Russian Revolution of the previous year.

He remained at the institute as a lecturer until 1921, but his work had lost its appeal after personal tragedy struck in 1919. Following the death of his son from scarlet fever, his father, his wife, and his newborn daughter all died during an epidemic of Spanish influenza. To help allay his grief, Kapitsa joined a Soviet-sponsored scientific trade delegation organized by Joffe. Although several countries were on the planned itinerary, England turned out to be the only country to grant Kapitsa a visa. The contingencies of international politics thus brought about a major turning point in Kapitsa’s career. He soon convinced the famous and influential English physicist Ernest Rutherford that he should be allowed to work under Rutherford’s supervision at the famous Cavendish Laboratory at Cambridge. Kapitsa remained at Cambridge for thirteen years, and it was with Rutherford’s guidance that his unique style of scientific creativity first flowered.

Several of Kapitsa’s characteristic work habits became established during these early years of research in England. First, although Rutherford was a nuclear physicist and initially set Kapitsa to work on problems in that field, Kapitsa soon became more interested in the design and operation of new apparatuses than in nuclear theory as such. Subsequent transitions in Kapitsa’s research interests can usually be traced to his desire to explore new domains with apparatuses originally designed to test established theory. For example, his interest in very high magnetic fields and very low temperatures came about in this way. Kapitsa thus sympathized with Rutherford’s rather brusque emphasis on experimental physics rather than highly formalized theory. Kapitsa also adopted Rutherford’s straightforward administrative style. Both men tried to keep administrative complications in their laboratories at a minimum. They also encouraged their students to stay in close touch with the experimental grounding of their science and to explore their intuitions by constructing and operating their own apparatuses whenever possible.

Life’s Work

The major transitions in Kapitsa’s career were brought about by political interventions. In 1934, he was detained after a visit to his mother in the Soviet Union, and he was not allowed to travel outside his native country again until 1965. The strategic and industrial demands of World War II required a move from Moscow to Kazan and an emphasis on the production of liquid oxygen. After the war, Kapitsa’s refusal to work on nuclear weapons resulted in his banishment from the Institute for Physical Problems, of which he had been director, and he was restricted to his own home, a restriction that amounted to virtual house arrest. In 1955, following Joseph Stalin’s death, Kapitsa was reinstated in the Soviet scientific establishment, and his work once again received state support. Because of Kapitsa’s experimental orientation, these fluctuations in his working conditions considerably influenced his research; his fascination with precise measurement remained his mainstay through what were often extremely trying circumstances.

Although the low-temperature research for which Kapitsa eventually won the 1978 Nobel Prize in Physics was primarily carried out in the 1930’s, shortly after his detention in the Soviet Union, his interest in this subject began during his years with Rutherford at the Cavendish Laboratory. Rutherford initially set Kapitsa to work on an important topic in nuclear physics, the curvature of the trajectory of alpha particles in strong magnetic fields. These positively charged particles are emitted by radioactive nuclei, and Kapitsa was the first to photograph their curved trajectories during the short period of time in which they pass through experimental apparatuses. Kapitsa invented new equipment to produce the strong magnetic fields required, and this project quickly shifted his attention away from nuclear physics. He began studying how very strong magnetic fields alter the electrical properties and dimensions of magnetized materials; the discovery of unexpected results at very low temperatures then instigated the research that produced his most famous discoveries.

As early as 1913, Heike Kamerlingh Onnes had discovered that when helium gas becomes a liquid at the very low temperature of 4.2 Kelvins, it becomes a superconductor and presents no resistance to the flow of an electric current. This discovery suggested the exciting possibility that technology could eventually utilize powerful electric currents without the usual limitations caused by resistive heating effects. Furthermore, these currents could be used to create powerful magnetic fields with innumerable applications in transportation and industry. Kapitsa’s contributions to low-temperature physics thus should be understood as part of one of the most important scientific investigations of the twentieth century, an investigation that appealed to Kapitsa’s practical interest in engineering problems.

This is particularly true, for example, of Kapitsa’s work on the liquefaction of gases such as hydrogen, helium, atmospheric air, and oxygen. Readily available supplies of low-temperature liquids are essential to the study of the properties of other materials at these temperatures. While still at the Cavendish, Kapitsa and John Cockcroft improved on existing methods for the liquefaction of hydrogen. In 1933, with Rutherford’s support, Kapitsa became an internationally acknowledged leader in low-temperature physics as director of the new Royal Society Mond Laboratory. He soon perfected a new method for the liquefaction of helium that later became the basis for the commercially successful Collins liquefier.

Kapitsa’s detention in the Soviet Union in 1934 was a serious disruption of his research for several years. He had remarried in England, and the stability he had achieved within the social and scientific world of Cambridge made it difficult for him to relocate his family in Moscow. Furthermore, his fierce sense of independence made him bridle at the thought of perhaps having to produce science according to a preset agenda. The blow was softened somewhat when, with the help of Rutherford and other friends, Kapitsa’s equipment was sold to the Soviet Union and shipped to the new Institute for Physical Problems, which he had been appointed to direct.

By 1938, he had accomplished one of his most important investigations, the demonstration of the superfluidity of liquid helium II. Helium II is a phase of helium that exists only below the extremely low temperature of 2.2 Kelvins. Kapitsa designed ingenious experimental apparatuses to demonstrate that the reason helium II is such a good conductor of heat is its vanishingly low viscosity, a property for which he coined the term “super-fluid.” He also encouraged his associate at the institute, Lev Davidovich Landau, to develop what became a widely accepted quantum-mechanical explanation for this phenomenon. This research in low-temperature physics was Kapitsa’s most creative and influential work, and it was cited as the reason for his Nobel Prize in Physics in 1978.

During World War II, Kapitsa made important contributions to the industrial base for the Soviet war effort. He invented a new turboexpansion machine for the liquefaction of air. Because oxygen is the first component of air to pass into the liquid phase as the air is cooled, Kapitsa’s invention was of great value for the production of pure oxygen.

Following the end of the war in 1945, Kapitsa fell out of favor with Stalin by refusing to contribute to nuclear-weapons projects. He was dismissed from the institute he had organized and directed and was restricted to his own home until 1954. During this period, he continued to do research on a smaller scale and made important contributions to the design of microwave generators. After returning to the Soviet scientific establishment in 1955, he became increasingly interested in plasma physics, the study of matter at very high temperatures, comparable to those in the interior of stars. Inspired by his study of ball lightning and bolstered by his production of energy discharges in helium using his own power generators, Kapitsa began investigating a new method of producing nuclear energy through controlled thermonuclear fusion of deuterium atoms. Although he remained enthusiastic about the potential of his technique until his death in 1984, there was little favorable response on the part of other nuclear physicists. Fusion research during the 1980’s continued to be dominated by methods that required high-temperature plasmas to be confined by strong magnetic fields. The general consensus was that this was one case where Kapitsa’s unique combination of theoretical and practical intuitions led him astray.

Significance

Kapitsa’s most important scientific accomplishments were in the domain of low-temperature physics. His rare combination of theoretical insight and engineering skills resulted in his ingenious design of precise measuring apparatuses and industrial equipment of great practical value. He is thus an important member of the large group of twentieth century physicists responsible for the gradual realization of the technological potential of low-temperature materials.

Kapitsa is a significant and symbolic figure for reasons other than his technical accomplishments. Few scientists have achieved his level of success under both Western and Soviet systems of government. Both in England and, to a much greater extent, in the Soviet Union, Kapitsa made an impact not only through his own research but through his direction of the research of others as well. Furthermore, in spite of the oppression he experienced under Stalin, Kapitsa retained the independence and iconoclasm that had endeared him to Rutherford. He wrote and spoke extensively about the Soviet system of education and scientific training. As might be expected from someone with Kapitsa’s broad cultural experiences, he repeatedly called attention to the dangers of an overly narrow emphasis on technical training in any one specialty. His fondness for Western art and literature was a typical example of his conviction that creative and beneficial science flourishes best under the stimulating conditions of a rich and argumentative culture. He openly expressed his scorn for political attempts to place restraints on the free exchange and debate of scientific ideas.

Finally, in addition to his resistance to Cold War barriers to scientific progress, Kapitsa represents the tension between good and evil that haunts twentieth century nuclear physics. His refusal to work on nuclear-weapons projects apparently was unflinching, and following his release to travel abroad in 1965 he became an active member of the Pugwash movement, an international group of scientists dedicated to bringing about nuclear disarmament and the peaceful application of scientific knowledge. His final work on controlled nuclear fusion as a means of relieving the increasing demands on global energy sources thus was an attempt to practice his commitment to the scientific enhancement of the human condition.

Bibliography

Badash, Lawrence. Kapitza, Rutherford, and the Kremlin. New Haven, Conn.: Yale University Press, 1985. After a brief but accurate description of the early years of Kapitsa’s career, Badash provides a detailed and well-documented description of the 1934 detention of Kapitsa in the Soviet Union and the unsuccessful diplomatic efforts by Rutherford and other scientists in response. Includes a valuable collection of Kapitsa’s letters during the transitional period between 1934 and 1936.

Dardo, Mauro. Nobel Laureates and Twentieth-Century Physics. New York: Cambridge University Press, 2004. Chronicles major developments in physics since 1901, the year the first Nobel Prize in Physics was awarded. Includes information about the work of Kapitsa and other prizewinners.

James, Ioan. Remarkable Physicists: From Galileo to Yukawa. New York: Cambridge University Press, 2004. Kapitsa is one of fifty-five physicists profiled in this book.

Kapitsa, Petr. Collected Papers of P. L. Kapitza. 3 vols. Edited by D. ter Haar. Elmsford, N.Y.: Pergamon Press, 1964-1967. The first volume of this three-volume collection includes a succinct summary of Kapitsa’s scientific accomplishments up to 1955.

Lifshitz, Eugene M. “Superfluidity.” Scientific American 198 (June, 1958): 20. Written by a brilliant student and colleague of Kapitsa, this usefully illustrated article provides a thorough firsthand account of Kapitsa’s discovery of the superfluidity of helium II and the subsequent experimental confirmations of Landau’s theoretical explanation.

Shoenberg, D. “Piotr Leonidovich Kapitza.” Biographical Memoirs of Fellows of the Royal Society 31 (1985): 327-374. Kapitsa was elected to the prestigious Royal Society of London in 1929, and this article is the official biographical sketch commissioned by the society. It is written by a knowledgeable physicist who was one of Kapitsa’s research students at Cambridge. The article thus is both scientifically accurate and based on personal knowledge of Kapitsa’s work habits. Includes a very thorough bibliography.

Spruch, Grace Marmor. “Pyotr Kapitza, Octogenarian Dissident.” Physics Today 32 (September, 1979): 34-36. Written by a professor of physics, this article provides a brief survey of Kapitsa’s career. Relying on Nikita Khrushchev’s published memoirs, Spruch provides evidence for Kapitsa’s refusal to contribute to Soviet military projects.

Trigg, George L. Landmark Experiments in Twentieth Century Physics. New York: Crane, Russak, 1975. In chapters 4 and 5, Trigg provides a fairly detailed discussion of the research into the low-temperature physics of helium during the three decades after 1908. His discussion includes extensive quotations and illustrations from the original publications, including Kapitsa’s 1938 account of his discovery of superfluidity. These chapters thus provide a useful survey of the context in which Kapitsa’s most original Nobel Prize-winning research took place.