Von Laue
ACHIEVEMENT(S): X-ray diffraction, a process which is now used to examine the structure of crystals.
DATE/PLACE OF BIRTH: 9 October 1879, at Pfaffendorf, near Koblenz, Germany
DATE/PLACE/AGE AT DEATH: 23 April 1960, in Berlin, Germany. Aged 80
DISCIPLINE: Physicist
FIELD: Physics
LANGUAGE: German
EDUCATION: Strasbourg Gymnasium, to 1898; University of Strasbourg, 1898-99;
University of Gottingen, 1899-1901 and 1903-05; University of Berlin,
1901-03
MAJOR WORK: 'Rontgenstrahl-Interferenzen' ('X-Ray Diffraction'), 1941
LIFE AND TIMES: In 1901 Von Laue moved to the University of Berlin, where he studied under Nobel laureate Planck*. He received his Ph.D. with the highest honours in June 1903 for a dissertation on the theory of light interference among plane parallel plates.
In 1905, Laue was invited to become Planck's assistant at the Institute of Theoretical Physics in Berlin, where he remained during the next four years. While working with Planck, with whom he developed a lifelong friendship, Laue pursued Planck's idea of applying the concept of entropy (the second law of thermodynamics, which states that all closed systems become increasingly disordered) to radiation fields, and introduced the concept of entropy into optics, investigating the thermodynamic significance of the coherence of light waves.
For this latter work Laue qualified as a university lecturer in 1906, and then served for the next three years as privatdozent (unsalaried lecturer) at Berlin. During this period at Berlin, Laue became one of the earliest adherents of Einstein's* controversial special theory of relativity, and from 1907 began working on a athematical proof for relativity drawn from his work in optics.
In 1909 Laue was appointed as privatdozent at the University of Munich, where he joined the physics faculty under theoretical physicist Arnold Sommerfeld and lectured on optics and thermodynamics. While still at Munich, in 1912, Laue then made his most significant discovery, when he decided to send X-rays through crystals. Since the discovery of X-rays by Roentgen* in 1895, it had proved impossible to prove that, as was generally supposed, they were very short electromagnetic waves. Laue began discussions with a colleague regarding the behaviour of light waves in crystals, the internal physical structure of which was also in dispute, but was presumed to consisted of a three-dimensional array (lattice) of atoms in a regular, repetitive pattern.
Laue's crucial idea was to expose a pure crystal to X-rays, in the belief that (if crystals were indeed of this regular nature) the behaviour of the X-rays (if they were indeed electromagnetic waves like light) upon penetrating a crystal should be approximately the same as that of light upon striking a diffraction grating, and that the resulting diffraction of light energy through the crystal could provide a means of measuring the wavelength of X-rays - i.e. that the crystal would act like a three-dimensional diffraction grating. Laue suggested an experiment to investigate this idea.
On 21 April 1912, two of Sommerfeld's assistants, Walter Friedrich and Paul Knipping, irradiated a copper sulphate crystal with a beam of X-rays and recorded regularly ordered dark points on a photographic plate behind the crystal - producing a series of what are now known as a Laue diagrams. With great brilliance, Laue then applied his work on the mathematics of diffraction in optical gratings to the diagrams, developing equations by which the observed diagrams could be related to the actual positions of atoms within the crystal and to X-ray wavelength.
A few weeks later, another, much clearer set of photographs proved to the research group the validity of Laue's new equations, and on 4 May 1912 Laue, Friedrich and Knipping announced their success in a letter to the Bavarian Academy of Sciences. The discovery of the diffraction of X-rays by crystals opened the entirely new field of research of X-ray diffraction* - the use of X-rays to identify the structure and position of atoms in crystals, and the use of crystals of known atomic structure to determine the wavelengths of X-rays - while also simultaneously proving for the first time both that atoms are real and that X-rays are electromagnetic waves.
It also opened up the field of X-ray spectroscopy - the analysis of X-rays emitted by atoms - and laid the foundation for the methods of X-ray crystallography worked out by Bragg*, and for the eventual elucidation of the molecular structure of penicillin by Dorothy C. Hodgkin, of amino acids by John C. Kendrew and Max Perutz, and of DNA by Crick* & Watson*.
For his great discovery - which Einstein called "one of the most beautiful in physics" - Laue was awarded the 1914 Nobel Prize for physics, at the age of only 35. In the autumn of 1912, he had been appointed associate professor at the University of Zurich, and two years later he became a full professor at the University of Frankfurt. During World War I, Laue worked with Wilhelm Wien at the University of Wurzburg on the development of vacuum tubes to improve the army's telephone and wireless communication systems. In 1917 he was appointed deputy director of the new Kaiser Wilhelm Institute for Physics in Berlin, of which Einstein was director. In 1919 he then arranged an exchange of teaching posts with Born*, enabling him to return to the University of Berlin, where he was appointed director of the Institute for Theoretical Physics (once again working with Planck) and remained until 1943.
Laue was one of very few German physicists who publicly attacked the actions of the Nazi regime during the 1930s, most famously in a speech at a physics congress held at the University of Wurzburg in 1933 when he strongly opposed the dismissal of Einstein as director of the Kaiser Wilhelm Institute for Physics in Berlin, and compared the Nazi rejection of relativity (based on the ideological objection to its origination by a Jew) to the rejection by the Catholic Church of the ideas of Galileo.
Einstein was not reinstated, but Laue succeeded in blocking the appointment of Nazi apologist Johannes Stark to the Prussian Academy in late 1933, and continued throughout the war to write to Einstein at Princeton in the United States at great personal risk. However, despite some government censure, Laue was permitted to teach and conduct research at the University of Berlin throughout World War II. When Berlin was bombed in 1944, Laue moved with Kaiser Wilhelm Institute (then under the direction of Heisenberg*) to the town of Hechingen in Wurttemberg.
In 1945, although he had not worked on the German uranium project, he was arrested with many other German scientists by the Allies and taken to England, where they were questioned about Germany's wartime scientific programmes. Laue was allowed to return to Germany in 1946, and was immediately appointed director of the Max Planck (formerly Kaiser Wilhelm) Institute and professor of physics at the University of Gottingen. In these positions, and as consultant to the State Physical-Technical Institute in Berlin, Laue played a major role in rebuilding post-war German science. In 1951, aged 71, he became director of the Fritz Haber Institute for Physical Chemistry in Berlin. On his retirement in 1959, he was named director emeritus, but died the following year from injuries sustained in an automobile accident.
ASSESSMENT: X-ray diffraction is a process which is now used to examine the structure of crystals and has been widely used in research of proteins and other organic substances. Laue’s discovery also proved the wavelength of X rays, and marked the origin of X-ray spectroscopy and solid-state physics, an important field in the development of modern electronics. .
EXTRA CONNECTIONS: None
ONELINER: Max Von Laue, discoverer of X-ray diffraction
BIBLIOGRAPHY:
EB, DSB
Segre, E., From X Rays to Quarks: Modern Physicists and Their Discoveries, New York: W.H. Freeman, 1980
PARENTS: Julius Laue and Minna Zerrenner
SIBLINGS: ?
SPOUSE: Magdalena Degen, married 1910
CHILDREN: One son and one daughter