Laue, Max von
(b. Pfaffendorf, near Koblenz, Germany, 9 October 1879; d. Berlin, Germany, 24 April 1960),
After passing the final secondary-school examination in March 1898, Laue began studying physics at the University of Strasbourg, although he was still in military service. In the fall of 1899 he transferred to Göttingen. Under the influence of Woldemar Voigt he chose to specialize in theoretical physics. At the same time he came to prefer optical problems, a preference that was strengthened by the lectures of Otto Lummer which he heard during his three semesters at the University of Berlin. In July 1903, Laue received his doctorate under Max Planck for a dissertation on the theory of interference in plane parallel plates. He then returned for two years to Göttingen, where he passed the state examination to qualify for teaching in the Gymnasiums.
The course that Laue’s life was to take was decided in the autumn of 1905, when Planck offered him an assistantship. Laue became Planck’s leading and favorite pupil, and the two formed a lifelong friendship. Laue introduced Planck’s central concept, entropy, into optics and qualified as university lecturer in 1906 with a work on the entropy of interfering pencils of rays. In the winter semester of 1905-1906 Laue heard Planck’s lecture at the Physical Colloquium on the special theory of relativity, which Einstein had just stated. After initial reservations Laue became one of the first adherents of the new theory and, as early as July 1907, presented a proof for it that he drew, characteristically, from optics.
In 1851, after many experiments, Fizeau had discovered a formula for the velocity of light in flowing water that could not be understood in terms of classical physics. Assuming light to be a wave phenomenon in the ether, one could either suppose that the ether does not contribute to the motion of the flowing water, in which case the velocity of light should be u = c/n; or one could postulate that the ether is carried along through the motion of the water, Page 51 | Top of Articlein which case the equation ought to be u = c/n ± v. Yet, curiously, the experiments showed partial ether “drag” varying as a specific fraction of the velocity of water—v(1—1/n2)—the Fresnel drag coefficient.
Einstein’s special theory of relativity dispensed with the addition or subtraction of the velocities, hitherto assumed to be self-evident, and applied instead a special “addition theorem.” In 1907 Laue demonstrated that this theorem readily yields Fizeau’s formula with the previously enigmatic Fresnel drag coefficient: u = c/n ± v(1 – 1/n2). Laue thereby furnished Einstein’s theory with an important experimental proof, which, along with the Michelson-Morley experiment and arguments from group theory, contributed to early acceptance of the theory. Having thus proved himself an expert in relativity theory, in 1910 Laue wrote the first monograph on the subject. He expanded it in 1919 with a second volume on the general theory of relativity; the work went through several editions.
In 1909 Laue became a Privatdozent at the Institute for Theoretical Physics, directed by Arnold Sommerfeld, at the University of Munich. Here, in the spring of 1912, Laue had the crucial idea of sending X rays through crystals. At this time scientists were very far from having proved the supposition that the radiation that Roentgen had discovered in 1895 actually consisted of very short electromagnetic waves. Similarly, the physical composition of crystals was in dispute, although it was frequently stated that a regular structure of atoms was the characteristic property of crystals. Laue argued that if these suppositions are correct, then the behavior of X radiation upon penetrating a crystal should be approximately the same as that of light upon striking a diffraction grating; and interference phenomena had been studied by means of the latter arrangement since Fraunhofer. These ideas, which Laue expressed in a discussion with Peter Paul Ewald, were soon being talked about by the younger faculty members. Finally Walter Friedrich, an assistant of Sommerfeld’s, and Paul Knipping, a doctoral candidate, began experiments in this field on 21 April 1912. The irradiation of a copper sulfate crystal yielded regularly ordered dark points on a photographic plate placed behind the crystal, the first of what are today called Laue diagrams. On 4 May 1912 Laue, Friedrich, and Knipping announced their success in a letter to the Bavarian Academy of Sciences.
Laue wrote in his autobiography:
I was plunged into deep thought as I walked home along Leopoldstrasse just after Friedrich showed me this picture. Not far from my own apartment at Bismarckstrasse 22, just in front of the house at Siegfriedstasse 10, the idea for a mathematical explanation of the phenomenon came to me. Not long before I had written an article for the Enzyklopaedie der mathematischen Wissenschaften in which I had to re-formulate Schwerd’s theory of diffraction by an optical grating (1835), so that it would be valid, if iterated, also for a cross-grating. I needed only to write down the same condition a third time, corresponding to the triple periodicity of the space lattice, in order to explain the new discovery.… The decisive day, however, was the one a few weeks later when I could test the theory with the help of another, clearer photograph.
The awarding of the Nobel Prize in physics for 1914 to Laue indicated the significance of the discovery that Albert Einstein called one of the most beautiful in physics. Subsequently it was possible to investigate X radiation itself by means of wavelength determinations as well as to study the structure of the irradiated material. In the truest sense of the word scientists began to cast light on the structure of matter.
Laue was appointed associate professor at the University of Zurich in 1912 and full professor at Frankfurt in 1914. In the latter year Laue’s father, an official in the military court system, was elevated to the hereditary nobility. Thus within a few years the unknown Privatdozent Max Laue became the worldfamous Nobel Prize winner Professor Max von Laue.
During the war Laue worked with Willy Wien in Würzburg on developing electronic amplifying tubes for improving the army’s communication techniques. In 1919 he arranged an exchange of teaching posts with Max Born: Born left Berlin to go to Frankfurt and Laue went to the University of Berlin, which he considered his true intellectual home. Here he was again able to be near Planck, his honored teacher and friend.
The new field of X-ray structural analysis that Laue established developed into an important branch of physics and chemistry. The leading researchers in the field were William Henry Bragg and William Lawrence Bragg. Laue himself, a true pupil pf Planck’s, was interested only in the “great, general principles” and did not concern himself with the study of the structure of individual substances; instead he continued to work on the fundamental theory. Following the preliminary investigations of Charles Galton Darwin and Peter Paul Ewald, Laue expanded his original geometric theory of X-ray interference into the so-called dynamical theory. Whereas the geometric theory dealt with only the interaction between the atoms of the crystal and the incident electromagnetic waves, the dynamical theory took into account the forces between the atoms as well. To be sure, the correction amounted to only a few seconds of arc, Page 52 | Top of Articlebut deviations had appeared early in the course of the very precise X-ray spectroscopic measurements.
In the following decades the theory was developed in various directions. When Laue later undertook to provide a comprehensive view of only the principles in Röntgenstrahl-Interferenzen (1941), his account ran to 350 pages. After the discovery of electron interference, Laue included this phenomenon in his theory. He did not, however, otherwise participate in the creation or development of quantum theory; and, like Planck, Einstein, de Broglie, and Schrödinger, he was skeptical of the “Copenhagen interpretation.”
In 1932 Laue received the German Physical Society’s Max Planck Medal. In his acceptance speech Laue presented an important result in the field of superconductivity: the interpretation of a seemingly paradoxical measurement made by W. J. de Haas. Subsequently Laue engaged in a fruitful joint study of this topic with Walther Meissner. Meissner conducted the relevant experiments at the Physikalisch-Technische Reichsanstalt, and Laue acted as theoretical adviser to that institution. Whereas Werner Heisenberg, Fritz London, and Heinz London worked on a quantum theory of superconductivity, Laue characteristically remained within the framework of the classical theory. He applied the purely phenomenological Maxwellian theory to the superconductor and later worked on the thermodynamics of superconductivity.
Laue held positions of exceptional trust at an early age. In 1921, proposed by Max Planck, he became a member of the Prussian Academy of Sciences. Following the establishment of the Emergency-Association of German Science (later the German Research Association), the German physicists elected Laue the representative for theoretical physics. He was chairman of the physics committee and also a member of the electrophysics committee until 1934. Through his solid judgment he directed the available financial resources to the truly important projects and thereby played a not inconsiderable role in the continuance of the “golden age of German physics” even during the economic depression of the Weimar Republic.
Laue’s scientific pride did not permit him passively to accept Einstein’s dismissal following the Nazi seizure of power. Only two colleagues in the Prussian Academy joined in his protest. As the chairman of the German Physical Society, Laue took issue with the slandering of the theory of relativity as a “world wide Jewish trick” and gave a highly regarded address at the opening of the physics congress in Würzburg on 18 September 1933. He likened Galileo, the champion of the Copernican world view, to Einstein, the founder of relativity theory, and openly expressed his hope and belief that, as the truth had once before won out against the Church’s prohibition, this time it would win out against the National Socialist proscription: “No matter how great the repression, the representative of science can stand erect in the triumphant certainty that is expressed in the simple phrase: And yet it moves,”
Although his defense of Einstein had been in vain, Laue did have one success at the end of 1933—in the Prussian Academy. Johannes Stark, Hitler’s famous follower, who had become a rabid opponent of modern physical theories, was supposed to be admitted into the Academy at the request of the new regime; and a group of academicians was prepared—reluctantly—to consent to the election. Yet in the session of 11 December 1933 the objections to this choice were set forth so emphatically by Laue, Otto Hahn, and Wilhelm Schlenk that the sponsors withdrew the proposal and Stark was not admitted. On 23 March 1934, Einstein wrote to Laue: “Dear old comrade. How each piece of news from you and about you gladdens me. In fact I have always felt, and known, that you are not only a thinker, but a fine person too.”
When Friedrich Schmidt-Ott, the elected president of the German Research Association, was dismissed by the Nazis and replaced by Johannes Stark, Laue was once again the spokesman for the physicists. He wrote to Schmidt-Ott on 27 June 1934: “I heard of your withdrawal from the presidency … with deep regret. The overwhelming majority of German physicists, especially the members of the physics committee, share this regret … Under the present circumstances, moreover, I fear that the change in the presidency is the prelude to difficult times for German science, and physics will no doubt have to suffer the first and hardest blow.”
In the Research Association, Laue’s judgment was no longer asked for; he also lost his position as adviser to the Physikalisch-Technische Reichsanstalt. He continued, however, as professor at the University of Berlin and as deputy director of the Kaiser Wilhelm Institute for Physics. Following his early retirement from teaching in 1943, Laue moved to Württemberg-Hohenzollern; at this time the Kaiser Wilhelm Institute, busy with military research and now under the direction of Werner Heisenberg, was relocated in Hechingen. Although Laue did not participate in the uranium project for the production of atomic energy, he was interned after the war with the atomic physicists by the Allies.
From the beginning Laue stood at the forefront of the rebuilding of German science. In the fall of 1946, working in Göttingen, he created with former colleagues Page 53 | Top of Articleleagues the German Physical Society in the British Zone and in 1950 took part in refounding the League of German Physical Societies, today known as the German Physical Society. Laue played an important part in the reestablishment of the Physikalisch-Tech-nische Bundesanstalt in Brunswick (the successor to the Physikalisch-Technische Reichsanstalt in Berlin) and in the German Research Association, where he was reelected to the physics committee until 1955. At first Laue was active primarily in his former post of deputy director of the Kaiser Wilhelm Institute for Physics at Göttingen. In April 1951, at the age of seventy-one, he took over the directorship of the former Kaiser Wilhelm Institute for Chemistry and Electrochemistry in Berlin-Dahlem. Active up to the end, Laue died in his eighty-first year following an automobile accident. He was mourned by colleagues throughout the world.
1. ORIGINAL WORKS. Laue’s writings were collected in Gesammelte Schriften und Vortrāge, 3 vols. (Brunswick, 1961), with his autobiography in vol. III. His works include Die Relativitätstheorie, 2 vols. (Brunswick, 1911-1919); Korpuskular- und Wellentheorie (Leipzig 1933); Röntgenstrahl-Interferenzen (Leipzig, 1941); Materiewellen und ihre Interferenzen (Leipzig, 1941); Geschichte der Physik (Bonn, 1946); and Theorie der Supraleitung (Berlin, 1947).
II. SECONDARY LITERATURE. See the following, listed chronologically: R. Brill, O. Hahn, et al., “Feierstunde zu Ehren von Max von Laue an seinem 80. Geburstag,” in Mitteilungen aus der Max Planck-Gesellschaft, 6 (1959), 323-366; Peter Paul Ewald, “Max von Laue,” in Biographical Memoirs of Fellows of the Royal Society, 6 (1960), 135-156, with bibliography; James Franck, “Max von Laue (1879-1960),” in Yearbook. American Philosophical Society (1960), 155-159; Walther Meissner, “Max von Laue als Wissenschaftler und Mensch,” in Sitzungsberichte der Bayerischen Akademie der Wissenschaften zu München (1960), 101-121; Max Päsler, “Leben und wissenschaftliches Werk Laues,” in Physikalische Blätter, 16 (1960), 552-567; Peter Paul Ewald, Fifty Years of X-Ray Diffraction (Utrecht, 1962), passim; Friedrich Herneck, “Max von Laue,” in Bahnbrecher des Atomzeitalters (Berlin, 1965), pp. 273-326; Paul Forman, “The Discovery of the Diffraction of X-Rays by Crystals,” in Archive for History of Exact Sciences, 6 (1969), 38-71; and Armin Hermann, “Forschungsförderung der Deutschen Forschungsgemeinschaft und die Physik der letzten 50 Jahre,” in Mitteilungen der Deutschen Forschungsgemeinschaft, 4 (1970), 21-34, also in Physik in unserer Zeit, 2 (1971), 17-23.
Copies of unpublished letters, almost all of them written to Laue, are available at the Deutsches Museum, Munich (Handschriftenabteilung) and at Stuttgart University, in the Department of the History of Science and Technology.