Niels Bohr is a Danish physicist and public figure, one of the founders of modern physics. He was the founder and head of the Copenhagen Institute for Theoretical Physics, the founder of the world scientific school, and also a foreign member of the USSR Academy of Sciences. This article will review the life story of Niels Bohr and his main achievements.
Merit
Danish Physicist Bohr Niels founded the theory of the atom, which is based on the planetary model of the atom, quantum concepts and postulates proposed by him personally. In addition, Bohr is remembered for his important work on the theory of the atomic nucleus, nuclear reactions and metals. He was one of the participants in the creation of quantum mechanics. In addition to developments in the field of physics, Bohr owns a number of works on philosophy and natural science. The scientist actively fought against the atomic threat. In 1922 he was awarded the Nobel Prize.
Childhood
The future scientist Niels Bohr was born in Copenhagen on October 7, 1885. His father, Christian, was a professor of physiology at a local university, and his mother, Ellen, came from a we althy Jewish family. Niels had a younger brother, Harald. Parents tried to make their sons' childhood happy and eventful. positivethe influence of the family, and in particular the mother, played a major role in the development of their spiritual qualities.
Education
Bohr received his primary education at the Gammelholm School. During his school years, he was fond of football, and later - skiing and sailing. At twenty-three, Bohr graduated from the University of Copenhagen, where he was considered an extraordinarily gifted research physicist. For his graduation project on the determination of the surface tension of water using the vibrations of a water jet, Niels was awarded a gold medal from the Royal Danish Academy of Sciences. Having received his education, the aspiring physicist Bor Niels remained to work at the university. There he carried out a number of important studies. One of them was devoted to the classical electronic theory of metals and formed the basis of Bohr's doctoral dissertation.
Thinking outside the box
One day, the president of the Royal Academy, Ernest Rutherford, was asked for help by a colleague from the University of Copenhagen. The latter intended to give his student the lowest grade, when he thought he deserved an "excellent" grade. Both parties to the dispute agreed to rely on the opinion of a third party, a certain arbitrator, who became Rutherford. According to the exam question, the student had to explain how a barometer can be used to determine the height of a building.
The student answered that for this you need to tie a barometer to a long rope, climb with it to the roof of the building, lower it to the ground and measure the length of the rope that has gone down. On the one hand, the answer wasabsolutely true and complete, but on the other hand, it had little in common with physics. Then Rutherford suggested that the student try again to answer. He gave him six minutes, and warned that the answer should illustrate an understanding of physical laws. Five minutes later, after hearing from the student that he was choosing the best of several solutions, Rutherford asked him to answer ahead of schedule. This time, the student proposed to go up to the roof with a barometer, throw it down, measure the time of the fall and, using a special formula, find out the height. This answer satisfied the teacher, but he and Rutherford could not deny themselves the pleasure of listening to the rest of the student's versions.
The next method was based on measuring the height of the barometer's shadow and the height of the building's shadow, and then solving the proportion. Rutherford liked this option, and he enthusiastically asked the student to highlight the remaining methods. Then the student offered him the simplest option. You just had to put the barometer against the wall of the building and make marks, and then count the number of marks and multiply them by the length of the barometer. The student believed that such an obvious answer should definitely not be overlooked.
In order not to be considered a joker in the eyes of scientists, the student suggested the most sophisticated option. Having tied a string to the barometer, he said, you need to swing it at the base of the building and on its roof, measuring the magnitude of gravity. From the difference between the received data, if desired, you can find out the height. In addition, by swinging a pendulum on a string from the roof of a building, one can determine the height from the period of precession.
At last, a studentoffered to find the manager of the building and, in exchange for a wonderful barometer, find out the height from him. Rutherford asked if the student really did not know the generally accepted solution to the problem. He did not hide what he knew, but admitted that he was fed up with the imposition of his way of thinking by teachers on students, in school and college, and their rejection of non-standard solutions. As you probably guessed, that student was Niels Bohr.
Moving to England
After working at the university for three years, Bohr moved to England. The first year he worked in Cambridge with Joseph Thomson, then moved to Ernest Rutherford in Manchester. Rutherford's laboratory at that time was considered the most outstanding. Recently, experiments were carried out in it that gave rise to the discovery of the planetary model of the atom. More precisely, the model was then still in its infancy.
Experiments on the passage of alpha particles through the foil allowed Rutherford to realize that in the center of the atom there is a small charged nucleus, which accounts for hardly the entire mass of the atom, and light electrons are located around it. Since the atom is electrically neutral, the sum of the charges of the electrons must be equal to the modulus of the charge of the nucleus. The conclusion that the charge of the nucleus is a multiple of the charge of the electron was central to this study, but so far remained unclear. Instead, isotopes have been identified – substances that have the same chemical properties but different atomic masses.
Atomic number of elements. Law of Displacement
Working in Rutherford's laboratory, Bohr realized that chemical properties depend on the numberelectrons in an atom, that is, from its charge, not mass, which explains the existence of isotopes. This was Bohr's first major achievement in this laboratory. Since the alpha particle attaches itself to a helium nucleus with a charge of +2, during alpha decay (the particle flies out of the nucleus), the “child” element in the periodic table should be placed two cells to the left than the “mother”, and during beta decay (the electron flies out from the nucleus) - one cell to the right. This is how the “law of radioactive displacements” was formed. Further, the Danish physicist made a number of more important discoveries that concerned the very model of the atom.
Rutherford-Bohr model
This model is also called planetary, because in it the electrons revolve around the nucleus, just like the planets around the Sun. This model had a number of problems. The fact is that the atom in it was catastrophically unstable, and lost energy in a hundred millionth of a second. In reality, this did not happen. The problem that arose seemed insoluble and required a radically new approach. This is where the Danish physicist Bor Niels proved himself.
Bohr suggested that, contrary to the laws of electrodynamics and mechanics, there are orbits in atoms, moving along which electrons do not radiate. An orbit is stable if the angular momentum of an electron located on it is equal to half of Planck's constant. Radiation occurs, but only at the moment of transition of an electron from one orbit to another. All the energy that is released in this case is carried away by the radiation quantum. Such a quantum has an energy equal to the product of the rotational speed and Planck's constant, or the difference between the initial andthe final energy of the electron. Thus, Bohr combined Rutherford's work and the idea of quanta, which was proposed by Max Planck in 1900. Such a union contradicted all the provisions of the traditional theory, and at the same time, did not completely reject it. The electron was considered as a material point that moves according to the classical laws of mechanics, but only those orbits that fulfill the "quantization conditions" are "allowed". In such orbits, the energies of an electron are inversely proportional to the squares of the orbit numbers.
Derivation from the "frequency rule"
Based on the "rule of frequencies", Bohr concluded that the frequencies of the radiation are proportional to the difference between the inverse squares of integers. Previously, this regularity was established by spectroscopists, but did not find a theoretical explanation. Niels Bohr's theory made it possible to explain the spectrum of not only hydrogen (the simplest of atoms), but also helium, including ionized one. The scientist illustrated the influence of the movement of the nucleus and predicted how the electron shells are filled, which made it possible to reveal the physical nature of the periodicity of the elements in the Mendeleev system. For these developments, Bohr was awarded the Nobel Prize in 1922.
Bohr Institute
After completion of Rutherford's work, the already recognized physicist Bohr Niels returned to his homeland, where he was invited in 1916 as a professor at the University of Copenhagen. Two years later, he became a member of the Royal Danish Society (in 1939, the scientist headed it).
In 1920, Bohr founded the Institute for Theoreticalphysics and became its leader. The authorities of Copenhagen, in recognition of the merits of the physicist, provided him with the building of the historical "Brewer's House" for the institute. The Institute met all expectations, playing an outstanding role in the development of quantum physics. It is worth noting that Bohr's personal qualities played a decisive role in this. He surrounded himself with talented employees and students, the boundaries between which were often imperceptible. Bohr's Institute was international, people tried to fall into it from everywhere. Among the famous people of the Bohr school are: F. Bloch, W. Weisskopf, H. Casimir, O. Bora, L. Landau, J. Wheeler and many others.
The German scientist Werne Heisenberg visited Bohr more than once. At the time when the "uncertainty principle" was being created, Erwin Schrodinger, who was a supporter of the purely wave point of view, discussed with Bohr. The foundation of a qualitatively new physics of the twentieth century was formed in the former Brewer's House, one of the key figures in which was Niels Bohr.
The model of the atom proposed by the Danish scientist and his mentor Rutherford was inconsistent. It united the postulates of classical theory and hypotheses that clearly contradicted it. In order to eliminate these contradictions, it was necessary to radically revise the basic provisions of the theory. Bohr's direct merits, his authority in scientific circles, and simply personal influence played an important role in this direction. The work of Niels Bohr showed that to obtain a physical picture of the microworld, the approach that is successfully used for the "world of big things" is not suitable, and it becameone of the founders of this approach. The scientist introduced such concepts as "uncontrolled impact of measuring procedures" and "additional quantities".
Copenhagen quantum theory
The probabilistic (aka Copenhagen) interpretation of quantum theory, as well as the study of its many "paradoxes", is associated with the name of the Danish scientist. An important role here was played by Bohr's discussion with Albert Einstein, who did not like Bohr's quantum physics in a probabilistic interpretation. The "correspondence principle", formulated by the Danish scientist, played an important role in understanding the patterns of the microcosm and their interaction with classical (non-quantum) physics.
Nuclear theme
Beginning to study nuclear physics under Rutherford, Bohr paid much attention to nuclear topics. In 1936, he proposed the theory of the compound nucleus, which soon gave rise to the drop model, which played a significant role in the study of nuclear fission. In particular, Bohr predicted the spontaneous fission of uranium nuclei.
When the Nazis captured Denmark, the scientist was secretly taken to England, and then to America, where, together with his son Oge, he worked on the Manhattan Project in Los Alamos. In the postwar years, Bohr devoted much of his time to the control of nuclear weapons and the peaceful use of atoms. He took part in the creation of the center for nuclear research in Europe and even turned his ideas to the UN. Based on the fact that Bohr did not refuse to discuss certain aspects of the "nuclear project" with Soviet physicists, he considered it dangerousmonopoly possession of nuclear weapons.
Other fields of knowledge
In addition, Niels Bohr, whose biography is coming to an end, was also interested in issues related to physics, in particular biology. He was also interested in the philosophy of natural science.
An outstanding Danish scientist died of a heart attack on October 18, 1962 in Copenhagen.
Conclusion
Niels Bohr, whose discoveries certainly changed physics, enjoyed great scientific and moral authority. Communication with him, even fleeting, made an indelible impression on the interlocutors. Bohr's speech and writing showed that he carefully chose his words in order to illustrate his thoughts as accurately as possible. Russian physicist Vitaly Ginzburg called Bohr incredibly delicate and wise.
