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STERN (Stern), Otto

( German-American physicist, Nobel Prize in Physics, 1943)

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Biography STERN (Stern), Otto
February 17, 1888, Mr.. - August 17, 1969
German-American physicist Otto Stern was born in Sora (now Zory, Poland) and was the eldest of five children of Oscar and Eugene Stern Stern (nee Rosenthal). Parents W. came from wealthy families, formed the state of affairs and milling grain trade. When he was four years old, the family moved to Breslau (Wroclaw). There, in Breslau, Otto graduated from public elementary and secondary school. Boy learns easily, eagerly acquiring knowledge, parents are encouraging him to read. After school, Sh, being financially independent because of his parents, spent several years studying the natural sciences under the guidance of teachers from Freiburg, Munich and other universities. Doctorate in physical chemistry Z. protected in 1912. at the University of Breslau.
Even in the years of study III. establish contacts with some leading physicists and chemists of the time. Lectures Arnold Sommerfeld sharpen his interest in theoretical physics, and a lecture by Otto Lummer and Ernst Pringsheim - Experimental physics. However, reading the work of Ludwig Boltzmann, . Rudolf Clausius and Walter Nernst on the molecular theory, . statistical mechanics and thermodynamics makes it such a strong impression, . that he chooses for his research area of Physical Chemistry, . the more so loved Professor of Physics and Department of Chemistry University of Breslau, . Otto Sakura and other, . conducted active research in that area.,
. Using bond Sakura with Fritz Haber, a friend of Albert Einstein, W
. in 1912. seek the concurrence of becoming the leader of his graduate work at the University of Prague. From Einstein he learns many new things about the latest developments in physics, and together they write an article. When Einstein for the next year moved to Zurich, W. follows him. Working with Einstein, he became assistant professor (part-time lecturer) of the Federal School in Zurich. Since the beginning of World War III. call in the Wehrmacht and sent to Poland as part of the meteorological team, engaged in monitoring the weather. Burdensome duties allow him to continue theoretical studies, in particular the work undertaken jointly with the Nernst. He applies the quantum theory and statistical mechanics to problems of thermodynamics and even publish an article. Later during the war, W. and several other scientists were transferred to the Nernst's laboratory in Berlin University, where he performed various studies commissioned by the Ministry of War. Berlin W. working with Max Born, James Franck, Max Volmer and other. Influenced by discussions with skilled experimenters Frank Vollmer interests and W. moved from the theoretical studies with the scope of the experiment.
After the war, Born became director of the Institute for Theoretical Physics, University of Frankfurt and invites W. the position of his assistant. SH. published together with Born's theoretical work on the surface energy of solids, but soon it captures the problem of experimental verification of the theory of molecular motion, developed in the middle of the XIX century. The famous Scottish physicist James Clerk Maxwell, on the basis of theoretical considerations, showed that the gas molecules are in constant random motion, and brought the form for the distribution of their velocities. Results Maxwell received universal recognition, but have not been directly confirmed experimentally. SH. decides to use the method of molecular beams, invented by French physicist Louis dune in 1911
Designed W. experimental setup consisted of a small furnace, . vaporizing the silver atoms of the metal sample (silver vapor molecules contain only one atom), . slit, . through which the atoms, . moving in the direction of the cut, . fell into the vacuum chamber, . and one more crack, . farther from the furnace outlet in alignment with the first slit and allowing more stop down the flow of atoms, . cut out from the thin beam,
. Located in the alignment of two slits, separated by some distance, W. thus created the conditions under which the atoms have passed through both slits have the same velocity direction, and the rarefied gas in a vacuum chamber reduces the likelihood of collisions, and thus the deviation of atoms and scattering beam. The velocities of the atoms passing through a second slot, and the number of atoms that had a particular speed, measured in different ways. One of the methods, although not the most accurate, was to put on the path of the beam gears. When rotating the wheels of the atoms, which managed to slip between the teeth of the first wheel, could pass between the teeth of the second wheel only if the gap between the teeth turned out to line their flight. Knowing the width of the gap, speed and distance between the wheels, W. could calculate the velocity of atoms that pass between them. Measurements completed in 1920,. (and refined in subsequent years), confirmed the theoretical predictions.
. The method of Stern was a powerful tool for monitoring invisible particles with a relatively crude laboratory instruments, but required a skilful mastery of the experimenter
. He turned to his colleague in History, Walter Gerlach asked to help investigate using the same method the magnetic moments of atoms. Since the atoms contain moving electrically charged particles, and the motion of charged particles is nothing like an electric current, the atoms behave like tiny magnets (as the current in the coil creates a magnetic field in the solenoid). The magnetic moment of the intensity and direction of the magnetic field. Classical physics says that the magnetic moment can have any direction. Sommerfeld, on the basis of quantum theory, predicted that the magnetic moment can have on the external field only two directions: the same direction as the external field, or be directed in the opposite direction. In a current experiment, the Stern - Gerlach molecular beam passes between the poles of an inhomogeneous magnet, which causes deviation of the beam. Classical theory predicts that the deviation of atoms with different directions of the magnetic moment will be distributed continuously, resulting merely to expand the narrow beam. Quantum theory predicts that the atoms will be rejected only one of two ways, ie. bundle split into two. Experience Stern - Gerlach, executed in 1921, clearly confirmed the validity of quantum theory.
In 1921, Mr.. SH. appointed professor of physics at the University of Rostock, and in 1923. becomes full (real) professor at Hamburg University. In Hamburg, having at its disposal a laboratory specially designed for research using molecular beams, it uses this method to test the predictions made by Louis de Broglie in 1924. And quantum theory and experiment have shown that electromagnetic radiation, such as light, has both a particle (quanta), and the wave properties. Despite the skepticism of many physicists, de Broglie, assuming that the particles should have wave properties, was even more radically, indicating the corresponding wavelengths. In 1927, Mr.. Clinton J. Davisson and Lester Germer experimentally proved (partly by accident) the existence of de Broglie waves for the electron. For their experiment, followed by supporting his experiments JP. Thomson. A few years later, W. directs a beam of helium atoms through the gears (to measure the velocity of the particles, which determines the de Broglie wavelength) on the surface of a crystal of lithium fluoride and watching diffraction - wave phenomenon. Knowing the distance between atoms in the crystal, it determines the wavelength for particles of helium. It agrees with the formula of de Broglie. Proof of the existence of the wave properties of large particles such as atoms, is even more convincing than in the case of electrons, and the Stern experience played an important role in the further development of quantum mechanics. In subsequent years, W. with Immanuel Estermann and O.R. Frisch measure the magnetic moment of protons (hydrogen nuclei) and, to my surprise (and everyone's surprise, physicists), reveal that he twice predicted P.A.M. Dirac.
Soon after Hitler became chancellor of Germany in 1933, Estermann, and other scholars of the Jews dismissed from the University of Frankfurt on the basis of Nazi anti-Semitic laws on civil rights. Although W. was a Jew, it for some time, protects against racist laws in the office of Germany army during the First World War. But in protest, he resigned and, together with Estermann accepts an invitation from the Physics Department of Carnegie Institute of Technology. There, taking up the post of professor and researcher, he helps to create a laboratory of molecular beams. In 1939, Mr.. SH. receives American citizenship and, when the United States entering into World War II, serves as a consultant to the Ministry of Defense.
In 1943, Mr.. The Nobel Prize is not awarded, but the next year W. was awarded the Nobel Prize in Physics 1943. 'for his contribution to the development of the method of molecular beams and the discovery and measurement of the magnetic moment of the proton'. Due to wartime conditions the usual awards ceremony is not held, and the prize was handed W. during breakfast, organized by the American-Scandinavian Foundation at the hotel Wal-Dorf-Astoria in New York. Nobel lecture 'method of molecular beams' ( 'The Method of Molecular Rays'), W. read only in 1946
After retiring from the Carnegie Institute of Technology in 1946. SH. moved to Berkeley (California), where settled his two sisters. Continuing to liaise with the physical community and to monitor developments in elementary particle physics, he lived in relative isolation. Regularly causing visits to Europe, W. refuses to set foot on the ground in Germany and receive a pension from the Germanic government.
In the last years of life Sh, never marries, gets a taste for the refined table and cigars. He willingly went to the movies. Death from heart attack catches him in one of the cinemas Berkeley. According to Emilio Segre 'W. was one of the greatest physicists of the XX century. He has written relatively few articles, but what effect are those which he wrote! '.
Member of the U.S. National Academy of Sciences and the American Philosophical Society, W. was an honorary doctor of the University of California and the Swiss Federal Institute of Technology.


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STERN (Stern), Otto, photo, biography STERN (Stern), Otto  German-American physicist, Nobel Prize in Physics, 1943, photo, biography
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