Niels Bohr is a Danish physicist and public figure, one of the founders of physics in its modern form. He was the founder and leader of the Copenhagen Institute of Theoretical Physics, the creator of the world scientific school, and also a foreign member of the USSR Academy of Sciences. This article will examine the life story of Niels Bohr and his main achievements.
Merits
Danish physicist Bohr Niels founded the theory of the atom, which is based on the planetary model of the atom, quantum representations and the postulates he personally proposed. In addition, Bohr was 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, Bor also has a number of works on philosophy and natural science. The scientist was actively fighting the atomic threat. In 1922 he was awarded the Nobel Prize.
Childhood
The future scientist Niels Bohr was born in the city of Copenhagen on October 7, 1885. His father Christian was a professor of physiology at a local university, and Ellen's mother came from a wealthy Jewish family. Niels had a younger brother, Harald. Parents tried to make their sons childhood happy and eventful. The positive influence of the family, and in particular the mother, played a crucial role in the formation of their spiritual qualities.
Education
Bohr received his primary education at the Hammelholm School. In his school years, he was fond of football, and later - skiing and sailing. At twenty-three, Bohr graduated from the University of Copenhagen, in which he was considered an unusually gifted research physicist. Nils was awarded a gold medal from the Danish Royal Academy of Sciences for his graduation project on determining the surface tension of water using the vibrations of a water stream. After graduating, the beginning physicist, Bohr Niels, remained 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
Once, a colleague from the University of Copenhagen turned to the president of the Royal Academy, Ernest Rutherford. The latter intended to give his student the lowest rating, while he considered that he deserved an excellent rating. 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 to use the barometer to determine the height of the building.
The student replied that for this you need to tie the 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 went down. On the one hand, the answer was absolutely correct and complete, but on the other, it had little in common with physics. Then Rutherford invited the student to try again to answer. He gave him six minutes, and warned that the answer should illustrate an understanding of physical laws. Five minutes later, having heard from the student that he was choosing the best of several solutions, Rutherford asked him to respond ahead of schedule. This time, the student offered to climb the roof with a barometer, drop it down, measure the time of fall and, using a special formula, find out the height. The teacher satisfied this answer, but he and Rutherford could not deny themselves the pleasure of listening to the rest of the student.
The next method was based on measuring the height of the shadow of the barometer and the height of the shadow of the building, with the subsequent solution of the proportion. Rutherford liked this option, and he enthusiastically asked the student to cover the remaining methods. Then the student offered him the simplest option. You just had to put the barometer on 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 known as a prankster in the eyes of scientists, the student proposed the most sophisticated option. Having tied a string to the barometer, he said, one needs to swing it at the base of the building and on its roof, measuring the magnitude of gravity. From the difference between the data obtained, if desired, you can find the height. In addition, swinging the pendulum on a cord from the roof of the building, you can determine the height by the period of the precession.
Finally, the student suggested finding the manager of the building and, in exchange for a wonderful barometer, find out his height. Rutherford asked if the student really did not know the generally accepted solution to the problem. He did not hide his knowledge, but admitted that he was fed up with the teachers imposing their way of thinking on their wards, at school and college, and rejecting non-standard solutions. As you probably guessed, this student was Niels Bohr.
Relocation 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 have been taking place in it, giving rise to the discovery of a planetary model of the atom. More precisely, the model then was still in its infancy.
The experiments on the passage of alpha particles through the foil allowed Rutherford to realize that in the center of the atom is a small charged nucleus, which accounts for almost 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 nuclear charge is a multiple of the electron charge was central to this study, but so far has remained unclear. But wasotopes were discovered - substances that have the same chemical properties, but different atomic masses.
Atomic number of elements. Law of bias
While working in Rutherford's laboratory, Bohr realized that the chemical properties depend on the number of electrons in an atom, that is, on its charge, and not mass, which explains the existence of isotopes. This was Bohr's first major achievement in this laboratory. Since the alpha particle constitutes a helium nucleus with a charge of +2, in alpha decay (the particle escapes from the nucleus) the “daughter” element in the periodic table should be placed two cells to the left of the “parent” cell, and in beta decay (the electron will fly out from the core) - to the right of one cell. Thus was formed the "law of radioactive displacement." Further, the Danish physicist made a number of more important discoveries that related to the atom model itself.
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 emerging problem seemed insoluble and required a radically new approach. Here the Danish physicist Bor Niels proved himself.
Bohr suggested that, contrary to the laws of electrodynamics and mechanics, atoms have orbits in which electrons do not emit. The orbit is stable if the moment of the number of motions of the electron located on it is equal to half the Planck constant. Radiation occurs, but only at the moment of transition of an electron from one orbit to another. All the energy that is released is carried away by a quantum of radiation. Such a quantum has an energy equal to the product of the rotational speed by the Planck constant, or the difference between the initial and final electron energy. Thus, Bohr combined the findings of Rutherford and the idea of ​​quanta, which was proposed by Max Planck in 1900. Such a union was contrary to all the provisions of 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 electron energies are inversely proportional to the squares of the orbit numbers.
Conclusion from the "frequency rule"
Based on the "rule of frequencies", Bohr concluded that the radiation frequencies are proportional to the difference between the inverse squares of integers. Previously, this pattern was established by spectroscopists, but could 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. The scientist illustrated the effect of nuclear movement and predicted how the electron shells are filled, which made it possible to identify the physical nature of the periodicity of elements in the periodic system. For these developments, in 1922, Bohr was awarded the Nobel Prize.
Bora Institute
Upon completion of work at Rutherford, 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 Danish Royal Society (in 1939, the scientist headed it).
In 1920, Bohr founded the Institute of Theoretical Physics and became its leader. The authorities of Copenhagen, in recognition of the merits of the physicist, provided him with the building of the historic 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 the personal qualities of Bohr were decisive in this. He surrounded himself with talented employees and students, the boundaries between which were often invisible. The Bohr Institute was international; it sought to fall from everywhere. Among the famous immigrants of the Borovsk school one can distinguish: F. Bloch, V. Weisskopf, H. Casimir, O. Bohr, L. Landau, J. Wheeler and many others.
The German scientist Verne Heisenberg came to Bor more than once. At a time when the “principle of uncertainty” was being created, Erwin Schrodinger, who was a proponent of a pure-wave point of view, discussed with Bohr. In the former "Brewer House", the foundation was formed of a qualitatively new physics of the twentieth century, one of the key figures in which was Niels Bohr.
The atomic model proposed by the Danish scientist and his mentor Rutherford was inconsistent. She combined the postulates of classical theory and hypotheses, which clearly contradicted her. In order to eliminate these contradictions, it was necessary to radically revise the main provisions of the theory. An important role in this direction was played by the direct merits of Bohr, his authority in scientific circles, and simply personal influence. The work of Niels Bohr showed that the approach successfully applied to the “world of big things” would not be suitable for obtaining a physical picture of the microworld, and he became one of the founders of this approach. The scientist introduced such concepts as “uncontrolled impact of measuring procedures” and “additional values”.
Copenhagen quantum theory
The Danish scientist’s name is associated with a probabilistic (aka Copenhagen) interpretation of quantum theory, as well as the study of its many “paradoxes”. An important role was played here by Bohr's discussion with Albert Einstein, who did not like the quantum physics of Bohr in a probabilistic interpretation. The “correspondence principle” formulated by a Danish scientist played an important role in understanding the laws of the microworld and their interaction with classical (non-quantum) physics.
Nuclear Theme
Starting to study nuclear physics at Rutherford, Bohr paid much attention to nuclear topics. He proposed in 1936 the theory of a composite nucleus, which soon gave rise to a droplet model, which played a significant role in the study of nuclear fission. In particular, Bor belongs to the prediction of spontaneous fission of uranium nuclei.
When the Nazis captured Denmark, the scientist was secretly taken to England and then to America, where he worked with his son Oge on the Manhattan project in Los Alamos. In the postwar years, Bohr devoted much time to nuclear control and the peaceful use of atoms. He took part in the creation of a center for nuclear research in Europe and even turned to the UN with his ideas. Based on the fact that Bohr did not refuse to discuss certain aspects of the “nuclear project” with Soviet physicists, he considered monopoly possession of atomic weapons dangerous.
Other areas 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 enormous scientific and moral authority. Communication with him, even fleeting, made an indelible impression on the interlocutors. From Bohr's speech and letter, it was clear that he painstakingly selects words to illustrate his thoughts as accurately as possible. Russian physicist Vitaly Ginzburg called Bohr incredibly delicate and wise.