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Tuesday, October 2, 2012

Max von Laue

 

The German physicist Max von Laue (1879-1960) was the first to use x-rays to study the arrangement of atoms in crystals. His work in x-ray crystallography earned him the Nobel Prize in physics in 1914.
Max Theodor Felix von Laue was born on October 9, 1879, in Pfaffendorf, Germany. His father was a civilian official in German military administration who in 1913 was raised to the hereditary nobility (hence the von in the family name). In the early 1890s the young von Laue gained a passionate interest in physics that lasted until his death some 60 years later.
Von Laue received his scientific training at the universities of Strasbourg, Munich, and Göttingen. He was awarded a doctorate in mathematics and physics by the University of Berlin (1903) where he came under the influence of Max Planck, one of the greatest physicists of the 20th century. In the fall of 1905 Planck offered von Laue a post at the Institute for Theoretical Physics. The four years (1905-1909) during which von Laue worked closely with Planck marked the beginning of his career as a creative scientist. An early and lifelong champion of the physical ideas of Albert Einstein, von Laue began publishing papers on the theory of relativity in 1907.
In 1909 von Laue moved to the University of Munich where he was associated with yet another distinguished physicist, Arnold Sommerfield. Continuing his interest in relativity at Munich, von Laue prepared a 200-page monograph on the subject, the first such book to be published on Einstein's revolutionary theories. At Sommerfield's suggestion von Laue began writing a treatise on wave optics. This undertaking led him to the famous work on x-ray analysis of the atomic structure of crystalline material.
The precise nature of x-radiation, discovered by W. C. Roentgen in 1895, had not yet been determined when von Laue initiated his study of x-rays. If, as some argued, x-rays were not made up of particles but were a form of electromagnetic radiation similar to ordinary light, then it should be possible to repeat well-known optical experiments using x-rays instead of beams of ordinary light. For example, when ordinary light passes through a diffraction grating (a piece of glass covered with a series of fine, parallel, equidistant lines engraved upon its surface) a characteristic diffraction or interference pattern results. Because the wave-length of x-rays was assumed to be much shorter than that of light, an x-ray diffraction experiment required a grating with lines more finely ruled than was physically possible.
Von Laue's contribution was the insight that when using x-radiation the glass diffraction grating can be replaced by crystalline material. The regular spacing of the atoms in the crystal will affect x-rays penetrating it in the same way that the closely engraved lines of the grating affect light passing through. Von Laue, always the theoretician, did not actually make the necessary experiments, but those who did confirmed his predictions--x-rays diffracted by crystals yielded the expected interference patterns.
Von Laue's discovery, which Einstein hailed as one of the most beautiful in the history of physics, won him the Nobel Prize in 1914. This pioneering work in x-ray crystallography opened the way for two quite different developments in physics, both of them of immense importance. First, it confirmed the electro-magnetic nature of x-radiation and made it possible to determine the wave length of x-rays with great accuracy. Second, it gave physicists and chemists a new tool for investigating the atomic structure of matter. In the 1950s it was x-ray diffraction studies that enabled scientists to reveal the structure of the nucleic acids (DNA and RNA) and to establish the new discipline of molecular biology.
During World War I von Laue helped to improve the electronic vacuum tubes used in the German army's communication system. After the war (1919) he accepted a post at the University of Berlin. Subsequent research led von Laue to refine his study of x-ray interference and to explore the phenomenon of super-conductivity whereby certain metals lose virtually all of their resistance to the flow of an electric current at temperatures approaching absolute zero (-273.16 C).
Between the two world wars, von Laue became a leading statesman of German theoretical physics. He held high positions in academic scientific institutions and used his influence there to defend freedom of thought and expression in science. He battled particularly against Nazi attempts to suppress relativity theory as the degenerate product of an inferior Jewish scientific outlook.
After World War II von Laue labored to revive German physics and bring it back into the world scientific community. In 1951 he was made director of the prestigious Fritz Haber Institute of Physical Chemistry, a post he held until his retirement in 1958. Two years later he lost his life in an automobile accident.


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