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BIOGRAPHIES OF GREAT SCIENTISTS
Bohr Nils Henrik David. Biography of a scientist
Directory / Biographies of great scientists
Einstein once said: “What is surprisingly attractive about Bohr as a thinking scientist is a rare fusion of courage and caution; few people had such an ability to intuitively grasp the essence of hidden things, combining this with keen criticism. He is without a doubt one of the greatest scientific minds of our age." Danish physicist Niels Henrik David Bohr was born on 7 October 1885 in Copenhagen as the second of three children of Christian Bohr and Ellen (nee Adler) Bohr. His father was a renowned professor of physiology at the University of Copenhagen; his mother came from a Jewish family well known in banking, political and intellectual circles. Their home was the center of very lively discussions on burning scientific and philosophical issues, and throughout his life Bohr pondered the philosophical implications of his work. He studied at the Gammelholm Grammar School in Copenhagen and graduated in 1903. Bohr and his brother Harald, who became a famous mathematician, were avid football players during their school days; Later, Nils was fond of skiing and sailing. In those years, Harald was much more famous than Niels, though not so much as a talented scientist, but as one of the best football players in Denmark. For a number of years he played as a halfback in the major league teams and in 1908 participated in the London Olympics, where Denmark won the silver medal. Niels was also a passionate football player, but he never rose above the reserve goalkeeper of a major league team, although he only played in this role in very rare matches. "Niels, of course, played well, but often he was late to get out of the gate," Harald joked. If at school Niels Bohr was generally considered a student of ordinary abilities, then at the University of Copenhagen his talent very soon made him talk about himself. In December 1904, Helga Lund wrote to her Norwegian friend: "By the way, about geniuses. I meet one of them every day. This is Niels Bohr, whom I have already told you about; his extraordinary abilities are becoming increasingly apparent. This is the best, most modest man in the world. He has a brother Harald , he is almost as talented and is a math student.I have never met two people so inseparable and loving each other.They are very young, one is 17, the other is 19, but I prefer to talk only to them, because they are very pleasant." Niels was indeed recognized as an unusually capable researcher. His graduation project, in which he determined the surface tension of water from the vibration of a water jet, earned him a gold medal from the Royal Danish Academy of Sciences. In 1907 he became a bachelor. He received his master's degree from the University of Copenhagen in 1909. His doctoral dissertation on the theory of electrons in metals was considered a masterful theoretical study. Among other things, it revealed the inability of classical electrodynamics to explain magnetic phenomena in metals. This study helped Bohr realize at an early stage in his scientific career that the classical theory could not fully describe the behavior of electrons. After receiving his doctorate in 1911, Bohr went to the University of Cambridge, England, to work with J. J. Thomson, who had discovered the electron in 1897. True, by that time Thomson had already begun to deal with other topics, and he showed little interest in Bohr's dissertation and the conclusions contained therein. Bohr at first suffered from a lack of knowledge of the English language and therefore, immediately upon arrival in England, he began to read David Copperfield in the original. With his usual patience, he looked up in the dictionary every word, the Danish equivalent of which he doubted, and especially for this purpose he bought himself a dictionary, which served him in all doubtful cases. Bor did not part with this red dictionary all his life later. Soon Bohr's life took a decisive turn: in October, at the annual celebratory dinner at the Cavendish Laboratory, he saw Ernest Rutherford for the first time. Although Bohr did not meet him personally at that time, Rutherford made a strong impression on him. Bohr became interested in the work of Ernest Rutherford at the University of Manchester. Rutherford and his colleagues studied the radioactivity of elements and the structure of the atom. Bohr moved to Manchester for a few months at the beginning of 1912 and plunged into these studies vigorously. He deduced many consequences from Rutherford's nuclear model of the atom, which has not yet received wide acceptance. In discussions with Rutherford and other scientists, Bohr worked out the ideas that led him to create his own model of the structure of the atom. In 1910, Niels met Margarethe Nerlund, sister of Niels Erik Nerlund, comrade Harald Bohr, and daughter of the pharmacist Alfred Nerlund from Slagels. In 1911, their engagement took place. In the summer of 1912 Bohr returned to Copenhagen and became an assistant professor at the University of Copenhagen. On August 1 of the same year, four days after Bohr returned from his first short study trip to Rutherford, he married Margaret. Their honeymoon took them to England, where, after a week's stay in Cambridge, the young couple visited Rutherford. Niels Bohr left him his work on the deceleration of alpha particles, begun shortly before returning home. The marriage of Niels Bohr to Margaret Nerlund brought them both real happiness - they meant so much to each other. Margaret Bohr became a genuine and indispensable support for her husband, not only due to the strength of her character, intelligence and knowledge of life, but, above all, due to her boundless devotion. They had six sons, one of whom, Aage Bohr, also became a famous physicist. Bor's other son, Hans, later wrote: "... It is impossible not to note the role mother played in our family. Her opinion was decisive for her father, his life was her life. In any event - small or large - she took part and, of course, was the closest adviser to her father when necessary make a decision." Over the next two years, Bohr continued to work on the problems that arose in connection with the nuclear model of the atom. Rutherford suggested that the atom consists of a positively charged nucleus around which negatively charged electrons revolve in orbits. According to classical electrodynamics, an orbiting electron must constantly lose energy. Gradually, the electron should spiral towards the nucleus and, in the end, fall on it, which would lead to the destruction of the atom. In fact, atoms are very stable, and hence there is a gap in the classical theory. Bohr was particularly interested in this apparent paradox of classical physics because it was too reminiscent of the difficulties he had encountered while working on his dissertation. A possible solution to this paradox, he believed, could lie in quantum theory. Applying the new quantum theory to the problem of the structure of the atom, Bohr suggested that electrons have some allowed stable orbits in which they do not radiate energy. Only when an electron moves from one orbit to another does it gain or lose energy, and the amount by which the energy changes is exactly equal to the energy difference between the two orbits. The idea that particles could only have certain orbits was revolutionary because, according to the classical theory, their orbits could be located at any distance from the nucleus, just as the planets could, in principle, revolve in any orbits around the Sun. Although the Bohr model seemed strange and a little mystical, it solved problems that had long puzzled physicists. In particular, it gave the key to separating the spectra of elements. When light from a luminous element (such as a heated gas composed of hydrogen atoms) passes through a prism, it does not produce a continuous spectrum that includes all colors, but a succession of discrete bright lines separated by wider dark areas. According to Bohr's theory, each bright colored line (i.e., each individual wavelength) corresponds to the light emitted by electrons as they move from one allowed orbit to another lower-energy orbit. Bohr derived a formula for the line frequencies in the spectrum of hydrogen, which contained Planck's constant. The frequency multiplied by Planck's constant is equal to the energy difference between the initial and final orbits between which the electrons make the transition. Bohr's theory, published in 1913, brought him fame; his model of the atom became known as the Bohr atom. Immediately appreciating the importance of Bohr's work, Rutherford offered him a lectureship at the University of Manchester, a post that Bohr held from 1914 to 1916. In 1916 he took over the professorship created for him at the University of Copenhagen, where he continued to work on the structure of the atom. In 1920 he founded the Institute for Theoretical Physics in Copenhagen. With the exception of the period of the Second World War, when Bohr was not in Denmark, he directed this institute until the end of his life. Under his leadership, the institute played a leading role in the development of quantum mechanics (the mathematical description of the wave and corpuscular aspects of matter and energy). During the XNUMXs, Bohr's model of the atom was replaced by a more sophisticated quantum mechanical model based mainly on the research of his students and colleagues. Nevertheless, the Bohr atom played an essential role as a bridge between the world of atomic structure and the world of quantum theory. Bohr was awarded the 1922 Nobel Prize in Physics "for his services to the study of the structure of atoms and the radiation they emit." At the presentation of the laureate, Svante Arrhenius, a member of the Royal Swedish Academy of Sciences, noted that Bohr's discoveries "led him to theoretical ideas that differ significantly from those that underlay the classical postulates of James Clerk Maxwell." Arrhenius added that Bohr's principles "promise abundant fruit in future research." In 1924 Bohr bought a manor in Lunnen. Here, on a beautiful meadow, he really liked to rest. Together with his wife and children, he cycled through the woods, swam in the sea, and played football. In the twenties, the scientist made a decisive contribution to what was later called the Copenhagen interpretation of quantum mechanics. Based on the uncertainty principle of Werner Heisenberg, the Copenhagen interpretation proceeds from the fact that the rigid laws of cause and effect, familiar to us in the everyday, macroscopic world, are not applicable to intra-atomic phenomena, which can only be interpreted in probabilistic terms. For example, it is impossible even in principle to predict in advance the trajectory of an electron; instead, one can specify the probability of each of the possible trajectories. Bohr also formulated two of the fundamental principles that determined the development of quantum mechanics: the principle of correspondence and the principle of complementarity. The correspondence principle states that the quantum mechanical description of the macroscopic world must correspond to its description within the framework of classical mechanics. The principle of complementarity states that the wave and corpuscular nature of matter and radiation are mutually exclusive properties, although both of these representations are necessary components of understanding nature. Wave or particle behavior may appear in a certain type of experiment, but mixed behavior is never observed. Having accepted the coexistence of two apparently contradictory interpretations, we are forced to do without visual models - such is the thought expressed by Bohr in his Nobel lecture. In dealing with the world of the atom, he said, "we must be modest in our inquiries and content ourselves with concepts that are formal in the sense that they lack the visual picture so familiar to us." Bohr's method of work seemed unusual to many. But upon closer acquaintance, it became clear that he fully corresponded to his scientific credo. With the exception of personal letters and short notes, Bohr himself wrote only a few articles. Best of all, his thought worked when he did not write, but dictated. In addition, Bor always needed the presence of a person with whom he could discuss problems. This kind of living soundboard was a necessary prerequisite for the work, a means of testing the strength of arguments. He felt an inner need for criticism, reacting extremely sharply to any critical statement. Often in the course of the discussion he was able to formulate his idea in the best possible way. Bohr greedily caught every fair remark regarding the choice of word and willingly made changes to the text. In the thirties, Bohr turned to nuclear physics. Enrico Fermi and his collaborators studied the results of the bombardment of atomic nuclei by neutrons. Bohr, along with a number of other scientists, proposed a drop model of the nucleus, consistent with many of the observed reactions. This model, which compares the behavior of an unstable heavy atomic nucleus to a fissile liquid droplet, enabled Otto R. Frisch and Lise Meitner to develop a theoretical framework for understanding nuclear fission in late 1938. The discovery of fission on the eve of World War II immediately gave rise to speculation about how it could be used to release colossal energy. During a visit to Princeton in early 1939, Bohr determined that one of the common isotopes of uranium, uranium-235, was a fissile material, which had a significant impact on the development of the atomic bomb. In the early years of the war, Bohr continued to work in Copenhagen on the theoretical details of nuclear fission, under the conditions of the German occupation of Denmark. However, on September 29, 1943, Bohr was repeatedly informed of the German decision to arrest him along with his entire family in connection with the impending deportation of Danish Jews to Germany. Fortunately, he managed to take the necessary measures and that night, together with his wife, brother Harald and other family members, cross to Sweden. From there, he and his son Aage flew to England in the empty bomb bay of a British military aircraft. Although Bohr considered building an atomic bomb technically unfeasible, work on building such a bomb was already underway in the United States, and the Allies needed his help. In late 1943, Niels and Aage Bohr traveled to Los Alamos to work on the Manhattan Project. Senior Bor made a number of technical developments in the creation of the bomb and was considered an elder among many scientists who worked there; however, at the end of the war, he was extremely worried about the consequences of the use of the atomic bomb in the future. He met with US President Franklin D. Roosevelt and British Prime Minister Winston Churchill, trying to convince them to be open and frank with the Soviet Union about new weapons, and also pushed for the establishment of a post-war arms control system. However, his efforts were not successful. After the war, Bohr returned to the Institute for Theoretical Physics, which expanded under his leadership. He helped found CERN (European Center for Nuclear Research) and played an active role in its scientific program in the fifties. He also took part in the founding of the Nordic Institute for Theoretical Atomic Physics (Nordita) in Copenhagen, the unified scientific center of the Scandinavian countries. During these years, the scientist continued to speak in the press for the peaceful use of nuclear energy and warned about the dangers of nuclear weapons. In 1950, he sent an open letter to the UN, repeating his wartime call for an "open world" and international arms control. A tall man with a great sense of humour, Bor was known for his friendliness and hospitality. It is said that it was absolutely impossible to play chess with Bohr. Whenever the opponent made a bad move, Bohr put the pieces in their original position and let him replay. This story is apparently fictional, but it is quite in the spirit of Bohr, he loved witty stories and believed that a good story does not have to be true. In this connection, Bohr used to quote a German colleague who allegedly said: "But, my dear friend, if you're telling a really interesting story, you don't have to stick too strictly to the facts!" October 7, 1955 Niels Bohr turned 70 years old. On this occasion, a solemn meeting was held on October 14, which was attended by the king. The President thanked the King for his participation in the meeting and for his support to the Society. The King announced that he had awarded the President the Order of the Dannebrog First Class. Having reached the age of mandatory retirement, Bohr resigned as professor at the University of Copenhagen, but remained head of the Institute for 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. For his efforts in this direction, he received the first Peaceful Atom Award, established by the Ford Foundation in 1957. Bohr died on 18 November 1962 at his home in Copenhagen as a result of a heart attack. Author: Samin D.K.
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