(b. Berlin, Germany, 16 December 1882; d. Munich, Germany, 15 November 1974)
Walther Meissner was the son of a chief engineer. Waldemar Meissner, and of his wife, Johanna Greger. He was educated in Königsberg and in Berlin-Charlottenburg, where he graduated from high school in 1901. He studied engineering at the Charlottenburg Technical University and passed the preliminary examination in mechanical engineering in 1906. Since he had attended lectures in mathematics, philosophy, and physics at the University of Berlin for several semesters, Meissner decided to study physics a short time before his final examination. He wanted to write an experimental doctoral dissertation under Paul Drude on the internal forces associated with semiconductors, a proposal that was rejected because the subject did not conform to the university’s program. Since Meissner had successfully completed the six-semester cycle of lectures and practical courses under Max Planck, he decided to study for his doctorate under him. He submitted a theoretical work on thermoelectricity, intending to use it in expanded form as his dissertation. Planck thought it contained too much criticism of other works and turned it down. But he suggested another subject, radiation pressure on moving bodies, for a dissertation on which Meissner received his doctorate in 1906.
In the following year Meissner worked with his father on engineering problems, after which, through Planck’s mediation, he entered the pyrometry laboratory of the engineering department of the Physikalisch-Technische Reichsanstalt (PTR) in 1908. There, besides taking his engineering examinations, he wrote several works, among them those on thermometry and viscosity.
In 1912, after one year of marriage, Meissner’s wife died while giving birth to a daughter. He sought consolation in research. With great ambition and hard work, that same year he succeeded in entering the electricity subdivision in the science department of the PTR, where, at the request of its president, Emil Warburg, he introduced the liquefaction of hydrogen. In the same year he put into operation a Nernst-type liquefaction apparatus manufactured by the Hoenow Company in Berlin. His first works were based on the study of the optical characteristics of liquid hydrogen and the measurements of the electrical and thermal conductivity of copper at temperatures between 20 and 375K.
In early 1915 Meissner interrupted his scientific activity to serve in World War I as a volunteer. During his service with the air force he worked on problems of measurement of distance and altitude, rose to the rank of commissioned officer, and was decorated with the Iron Cross (second class). In 1921 Meissner married Johanna Galinert: they had two sons. At the PTR he continued his low-temperature studies with the measurement of the thermal and electrical conductivity of metals such as lithium. In collaboration with the Linde Company (Munich) and with the support of the Emergency Association of German Science, he prepared the installation of helium liquefaction equipment in accordance with the Leiden method using precooled hydrogen. On 7 March 1925 Meissner succeeded in liquefying about 200 cc of helium that he had separated from a heliumneon mixture produced by Linde. Thus, besides the laboratories in Leiden (Kamerlingh Onnes, since 1908) and Toronto (John C. McLennan, since 1923), there was now a third laboratory where temperatures as low as about 1.5K were available for experiments. Meissner wanted to find out whether all metals could become superconductive simply by being at a low enough temperature and in a pure enough state. He studied monocrystalline filaments of gold, zinc, and cadmium, as well as polycrystalline iron, platinum, nickel, silver, and cadmium. Neither a high degree of purity nor the most uniform crystal structure led to superconductivity at temperatures as low as 1.3K.
According to the plans of the Ministry of the Interior and the Emergency Association of German Science, a large cryogenics institute was to be built in Germany in the mid 1920’s; the nation’s major centers for physics. Berllin and Göttingen, were being discussed as possible sites. Finally Berlin was chosen, not only because Meissner had already built a hydrogen liquefaction unit at the PTR and was just about to install a helium liquefier there, but also because of Max Planck’s influence. In 1927 the new cryogenics laboratory, which was directly under the control of the president of the PTR, was inaugurated. The possibility of numerous openings for guest researchers was welcomed by scientists at the university and in industry alike.
In the new cryogenics laboratory Meissner and his colleagues studied a great number of elements for superconductivity; in 1928 they discovered the sixth superconductive element known at that time: tantalum, used in the filaments of incandescent light bulbs. It was the first superconducting element in group V of the periodic system. Further elements that Meissner discovered to be superconductive were thorium, titanium, and vanadium. Copper sulfate was also found to lose its resistance at low enough temperatures. It was the first time that a chemical compound had become superconductive: moreover, one of its components was an insulator. This result led to systematic studies on further compounds and alloys, among which carbides, especially niobium carbide, displayed superconductive properties even at about 10K—that is, at a temperature scientists had already been able to achieve using solid-state hydrogen.
Meissner conducted further experiments to shed light on the nature of superconductivity, studying currents in superconductive metals. On this subject, which to him was closely related to the magnetic behavior of superconductors, he remained in close contact with Max von Laue, who had been a the-oretical physicist at the PTR since 1925 and was available to experimenters for consultation half a day per week, In order to answer the question discussed by many physicists—whether a current in a superconductor fills the entire cross section or flows on the surface—Laue suggested that the magnetic field be studied between two superconductors placed very close to each other, both with a current running running through. In the spring of 1933, in the course of these measurements Meissner and his colleague Robert Ochsenfeld observed a new phenomenon that contributed greatly to the understanding of superconductivity. The magnitude of the magnetic field measured between conductors was a function of the direction of the current, which could be explained by the role played by the earth’s magnetic field. Therefore, Meissner and Ochsenfeld carried out the measurements of changes in the magnetic field close to the conductors when these were subject only to the earth’s field, that is, without any current running through them. Before superconductivity set in, the magnetic lines of force penetrated the crystals with almost no resistance because of their low susceptibility. From what was known about superconductivity at that time, it was expected that the distribution of the lines of force would remain unchanged if the temperature were lowered below the threshold level. However, Meissner and Ochsenfeld observed an increase in the lines of force in close proximity to the superconductors. Meissner interpreted this result as follows: the magnetic field flux was displaced from the crystals when superconductivity set in (see Figure 1). The magnetic field flux that previously flowed inside the conductors was now flowing between the crystals.
The Meissner-Ochsenfeld effect showed that, contrary to previous assumptions, the transition from the state of normal conductivity to that of superconductivity was completely reversible. As long as only ideal conductivity was considered to be the characteristic feature of superconductivity, according to Maxwell’s theory the state of a superconductive sample should depend on its prior state. When a sample was first made superconductive by cooling and then an outside magnetic field was applied, the sample should remain without a field, since ideal conductivity should prevent the entry of a field. In the reverse case, when the cooling followed the application of a magnetic field, a magnetic field should remain, as if frozen, inside the superconductor, even after the removal of the field. Meissner and Ochsenfeld proved that the sample in the latter case also lost its inner field through the displacement of the lines of force, which meant that the final state was independent of the means by which it was
attained. This finding immediately led to the development of thermodynamic theories on superconductivity and became the starting point for Fritz and Heinz London’s phenomenological theory of superconductivity.
Cryogenics was not the only field that captured Meissner’s interest. At the same time he directed the laboratory for “electrical-atomic” research, where precise measurements of the magnetic moments of, among other elements, potassium and lithium were carried out using atomic radiation. Among Meissner’s numerous scientific studies were his measurements of the susceptibilities of gases. The change in the electrical conductivity of the purest metals in magnetic fields, contact resistance, and the plasticity of metal crystals.
It seemed that with Planck’s and Laue’s support Meissner had a chance to expand his research activity. He expected to assume an honorary professorship at Berlin University, where he had qualified as a lecturer in 1930. However, Meissner perceived the new director of the PTR, Johannes Stark (a National Socialist supporter), as a threat to his work. Stark was opposed to his being concurrently active at the PTR and at the university, especially because Max von Laue, one of the few people to speak out against the National Socialist government, was teaching there. When Meissner was offered a chair at Munich’s Technical University in 1934, his conflicts with Stark were one of the major reasons why he left the unique cryogenics laboratory in Germany for a chair in engineering physics despite his interest in pure physics.
Once in Munich, Meissner immediately started making plans to build a new cryogenics laboratory. In collaboration with the Linde Company, he developed a helium liquefier that worked without precooled hydrogen, in accordance with a method of Peter Kapitza’s. But it was not completed until 1941, during the war. In 1943 Meissner moved his institute to Herrsching on the Ammersee, southwest of Munich, in order to escape bomb attacks.
After World War II, Meissner worked hard for scientific recovery. Since he had not been a National Socialist supporter, he was offered numerous positions in science administration. He was concurrently the director of both institutes for experimental physics at the Technical University as well as dean of the Faculty of Sciences, director of the government’s testing bureau, president of the Bavarian Academy of Sciences (1946–1950) (of which he had been a member since 1938).president of the Bavarian Physical Society, and member of the board of directors of the Deutsches Museum. Within the Bavarian Academy of Sciences he established the Commission for Cryogenics Research. After becoming professor emeritus in 1952, Meissner continued to do cryogenics research. His guidance resulted not only in studies on curves of hysteresis in superconductors and the transition of the superconducting into the normal state, on the electrostatic effects in superconductors, and on the design of new helium liquefiers, but also on the critical Reynolds number for flow in pipes, the discovery of the paramagnetic effect, and the development of highly sensitive galvanometers. At a session of the Bavarian Academy of Sciences in 1962. Meissner, by then almost eighty years old, reported on studies conducted by two students, R. Doll and M. Näbauer, who had proven that the magnetic flux in a super-conductive ring is quantized.
Meissner was coeditor of Zeitschrift für angewandte Physik, Kältetechnik, and Technische Physik in Einzeldarstellungen. Beside numberous scientific honors, he received the German Federal Republic’s Distinguished Service Cross.
I. Original Works. Meissner’s scientific work has been recorded in over 200 publications. No comprehensive edition of his works exists, but some are listed in Poggendorff, V, 830-831. A list of his works between 1907 and 1952 was published by G. U. Schubert (see below). His writings include “Erzeugung tiefer Temperaturen und Gasverflüssigung”, H. Geiger and K. Scheel, eds., Handbuch der Physik, XI (1926), 272-399; “Telephon und Mikrophon”, ibid., XVI (1927), 167-200; Elektronenleitung, Galvanomagnetische, thermoelektrische und verwandte Effekte, XI, pt. 2 of W. Wien and F. Harms, eds., Handbuch der Experimentalphysik (Leipzig, 1935), with M. Kohler and H. Reddemann; “Wärmeleitung in festen Körpern”, in G. Joos, ed., Naturforschung und Medizin in deutschland 1939-1946, VIII (Wiesbaden, 1947), 212-221, with G. U. Schubert; “Supraleitung”, ibid., IX (Wiesbaden, 1948), 143-162, with G. U. Schubert The first mention of the Meissner-Ochsenfeld effect is in “Ein neuer Effekt bei Eintritt der Supraleilfahigkeit”, in Die Naturwissenschaften, 21 (1933), 787-788, with R. Ochsenfeld. There is a detailed discussion in “Über die Änderung der Stromverteilung und der magnetischen. In duktion beim Eintritt der Supraleitfähigkeit”, in Physikalische Zeitchrift, 37 (1936), 499-470, with F. Heidenreich.
Most of Meissner’s extensive scientific correspondence is at the Deutsche Museum. A small portion of it is in various archives, as indicated in Thomas S. Kuhn et al. Sources for History of Quantum Physics (Philadelphia, 1967).
II. Secondary Literature. No biography of Meissner exists, only some laudatory articles on his birthday and obituaries. They include F. X. Eder, “Walther Meissner zum 80. Geburtstag”, in Zeitschrift für angewandte Physik14 (1962), 697-698; H. Meier-Leibnitz, “Walther Meisssner”, in Jahrbuch der Bayerischen Akademie der Wissenschaften, 1975, 232-236; and G. U. Schubert, “Zum 70. Geburtstag von Walther Meissner”, in Allgemeim Wärmetechnik, 3 (1952), 252-254, with a bibliography of 156 works.