BOR Niels (Bohr)( Danish physicist, Nobel Prize in Physics, 1922)
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Biography BOR Niels (Bohr)
October 7, 1885, Mr.. - November 8, 1962
Danish physicist Niels Henrik David Bohr was born in Copenhagen and was the second of three children, Christian Bohr and Ellen (nee Adler) Bor. His father was a renowned professor of physiology at the University of Copenhagen; his mother came from a Jewish family, well known in the banking, political and intellectual circles. Their house was the center of a very lively discussions on topical scientific and philosophical questions, and throughout his life B. pondered the philosophical conclusions from his work. He studied at Gammelholmskoy grammar school in Copenhagen and graduated from it in 1903. B. and his brother Harald, who became a renowned mathematician, in his school years have been an avid soccer players and later Niels fond skiing and sailing
When B. was a student of physicist, University of Copenhagen, where he became a bachelor in 1907, it recognized the extraordinary abilities of the researcher. His thesis project, in which he determined the surface tension of water to the vibration of the water jet, brought him the gold medal of the Royal Danish Academy of Sciences. Master's degree he received the University of Copenhagen in 1909. His doctoral thesis on the theory of electrons in metals was considered a masterful theoretical study. Among other things, it unmasked the inability of classical electrodynamics to explain the magnetic phenomena in metals. This study helped to understand Bohr in the early stages of his career, that the classical theory can not fully describe the behavior of electrons.
After receiving his doctorate in 1911, B. went to Cambridge University in England, to work with J. J. Thomson, who discovered the electron in 1897. However, by the time Thompson began studying other topics already, and he showed little interest in the thesis B. and conclusions contained therein. But B. Meanwhile, interest in the work of Ernest Rutherford at Manchester University. Rutherford and his colleagues studied the issues of radioactive elements and the structure of the atom. B. moved to Manchester for a few months in early 1912. and energetically plunged into these studies. He brought a lot of consequences from the nuclear model of the atom proposed by Rutherford, who has not received more widespread acceptance. In discussions with Rutherford and other scientists B. working out the ideas that led him to create his own model of atomic structure.
In the summer of 1912. B. returned to Copenhagen and became an assistant professor at the University of Copenhagen. In the same year he married Margrethe Norlund. They had six sons, one of whom, Oge Bor, also became a renowned physicist.
During the next two years B. continued to work on problems arising in connection with the nuclear model of the atom. Rutherford suggested in 1911 that the atom consists of a positively charged nucleus, around which revolve in their orbits negatively charged electrons. This model is based on representations, an experienced support in solid state physics, but led to one intractable paradox. According to classical electrodynamics, orbiting electron should continuously lose energy, giving it in the form of light or other forms of electromagnetic radiation. As its energy is lost, the electron must spiral closer to the nucleus and ultimately fall on him, which would lead to the destruction of the atom. In fact, the atoms are very stable, and, therefore, there a gap in the classical theory. Boron has a particular interest in this apparent paradox of classical physics, because all too reminiscent of the difficulties he has faced while working on his thesis. A possible solution to this paradox, as he thought, might lie in quantum theory.
In 1900, Mr.. Max Planck has suggested that electromagnetic radiation emitted by hot matter, is not a continuous stream, and well-defined discrete portions of energy. Calling in 1905. these units quanta, Albert Einstein extended this theory to electron emission arising in the absorption of light by certain metals (the photoelectric effect). Using the new quantum theory to the problem of atomic structure, B. suggested that the electrons have certain allowed stable orbits, where they do not radiate energy. Only when the electron passes from one orbit to another, it acquires or loses energy, and the amount by which changes the energy exactly equal to the energy difference between the two orbits. Idea, . that the particles can have only certain orbits, . was revolutionary, . because, . according to classical theory, . their orbits can be located at any distance from the nucleus, . just as the planet could, in principle, turn on any orbit around the Sun.,
. Although Bohr's model seemed a little strange and mystical, it is possible to solve the problem, long puzzling physicists
. In particular, she gave the key to the separation of spectra of elements. When light from the luminous element (eg, . hot gas, . consisting of atoms of hydrogen) passes through a prism, . He does not give a continuous spectrum includes all colors, . a sequence of discrete bright lines, . separated by a broad dark areas,
. According to the theory of BA, each bright colored line (ie. each individual wavelength) corresponds to the light emitted by electrons when they move from one allowed orbit to another orbit with lower energy. B. derived a formula for the frequencies of lines in the spectrum of hydrogen, which contained the Planck constant. Frequency multiplied by Planck's constant, equal to the energy difference between initial and final orbits, between which the electrons make a transition. B. The theory, published in 1913, brought him fame, his model of the atom has become known as the Bohr atom.
. Immediately assess the importance of BI, Rutherford suggested that he bet a lecturer at Manchester University - a post that Bohr held from 1914 to 1916
. In 1916. he was appointed professor, created for him at Copenhagen University, where he continued to work on the structure of the atom. In 1920, Mr.. He founded the Institute for Theoretical Physics in Copenhagen, except during the Second World War, when B. was not in Denmark, he led that institution until his death. Under his leadership the institute played a leading role in the development of quantum mechanics (the mathematical description of the wave and corpuscular aspect of matter and energy). During the 20-ies. Bohr model of the atom has been replaced by more sophisticated quantum-mechanical model, based mainly on studies of his students and colleagues. Nevertheless, Bohr's atom has played a significant role as a bridge between the world of atomic structure and the world of quantum theory.
B. was awarded in 1922. Nobel Prize in Physics "for his services to study the structure of atoms and the radiation emitted by them '. When presenting the laureate Svante Arrhenius, a member of the Royal Swedish Academy of Sciences, noted that the opening of B. 'brought him to the theoretical ideas, which differ significantly from those which underlie the classical postulates of James Clerk Maxwell'. Arrhenius added that the inherent B. principles' promise rich dividends in future studies. "
B. written many papers on the problems of epistemology (knowledge) that arise in modern physics. In the 20-ies. He made a decisive contribution to what later was called the Copenhagen interpretation of quantum mechanics. Based on the uncertainty principle of Werner Heisenberg, . Copenhagen interpretation assumes, . that the strict laws of cause and effect, . familiar to us in everyday, . macroscopic world, . applicable to the phenomena of intra -, . which can only be interpreted in probabilistic terms,
. For example, it is impossible even in principle predict the trajectory of the electron, instead you can specify the probability of each of the possible trajectories.
B. also formulated two fundamental principles that determined the development of quantum mechanics: the principle of conformity and the principle of subsidiarity. The correspondence principle asserts that a quantum-mechanical description of the macroscopic world must conform to its description in the framework of classical mechanics. The principle of subsidiarity states that the wave and particle nature of matter and radiation are mutually exclusive properties, although both these ideas are essential components of understanding the nature of. The wave or particle behavior can manifest itself in a certain type of experiment, but a mixed behavior is observed never. Adopting the coexistence of two apparently conflicting interpretations, we are forced to do without the visual models - such is the idea expressed by B. in his Nobel lecture. In dealing with the world of the atom, "he said, 'we must be modest in our demands and content concepts, which are formal in the sense that they lack so familiar to us a visual picture."
In 30-ies. B. turned to nuclear physics. Enrico Fermi and co-workers studied the results of the bombardment of atomic nuclei with neutrons. B. with several other scientists suggested that liquid-drop model, corresponding to many reactions observed. This model, where the behavior of unstable heavy atomic nuclei is compared with the dividing of the liquid drop, gave at the end of 1938. to Otto P. Frisch and Lise Meitner to develop a theoretical basis for understanding the fission. The discovery of fission on the eve of the Second World War, immediately gave rise to speculation about how it can be used to release the enormous energy. During a visit to Princeton in early 1939. B. determined that one of the common isotopes of uranium, uranium-235 is fissile material, which had a significant impact on the development of the atomic bomb.
In the early years of the war B. continued to work in Copenhagen, in Germanic occupation of Denmark, over the theoretical details of the fission. However, in 1943, warned about the impending arrest, B. family fled to Sweden. From there he and his son Aage flew to England in the empty bomb bay of the British military aircraft. Although B. considered the creation of the atomic bomb is technically feasible, the establishment of such a bomb has already begun in the United States and its allies needed assistance. At the end of 1943. Niels Aage and went to Los Alamos to take part in work on the Manhattan Project. Senior B. made a number of technical developments to create a bomb and was considered an elder among the many scientists working there, but it at the end of the war is extremely worried about the effects of the atomic bomb in the future. He met with U.S. President Franklin D. Roosevelt and British Prime Minister Winston Churchill, . trying to persuade them to be open and candid with the Soviet Union on a new weapon, . and insisted on establishing a system of arms control in the postwar period,
. However, his efforts were not successful.
After the war, B. returned to the Institute of Theoretical Physics, which has expanded under his leadership. He helped to found the CERN (European Organization for Nuclear Research) and played an active role in its research program in the 50-ies. He also participated in the basis Nordic Institute for Theoretical Atomic Physics (Nordita) in Copenhagen - Joint Research Center Nordic states. During these years, B. continued to serve in the press for the peaceful use of nuclear energy and warned of the dangers of nuclear weapons. In 1950, Mr.. He sent an open letter to the UN, repeating its call for the war years to the 'open world' and the international arms control. For his efforts in this direction, he won first prize 'for the peaceful atom', established by the Ford Foundation in 1957
Reaching the age of 70 mandatory retirement in 1955, B. resigned as professor at Copenhagen University, but remained head of the Institute of Theoretical Physics. In the last years of his life he continued to contribute to the development of quantum physics and showed great interest in the new field of molecular biology.
The man is tall, with a great sense of humor, B. was known for its friendliness and hospitality. 'Benevolent interest in people, shown by AB, has made a personal relationship at the Institute in many ways reminiscent of a similar relationship in the family' - recalled John Cockcroft in a biographical memoir of B. Einstein once said: 'What is surprising is attracted to B. as a scientist-philosopher, because this is a rare alloy of courage and prudence, very few people possess this ability intuitively grasp the essence of hidden things, combining it with a heightened criticism. He is, without doubt, is one of the greatest scientific minds of our century '. B. died November 18, 1962, Mr.. at his home in Copenhagen as a result of a heart attack.
B. was a member of more than two dozen leading scientific societies and was president of the Royal Danish Academy of Sciences in 1939. the end of life. In addition to the Nobel Prize, he received the highest awards of many leading scientific societies, including the Medal of the Max Planck Germanskogo Physical Society (1930) and the Copley Medal of Royal Society of London (1938). He had honorary degrees from leading universities, including Cambridge, Manchester, Oxford, Edinburgh, the Sorbonne, Princeton, McGill, Harvard and Rockefeller Center.