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Koch, Niels Fabian Helge von. Biography Scientific discoveries of Niels Bohr

Bohr Niels Hendrik David (October 7 1885 , Copenhagen - November 18 1962 , Copenhagen), Danish scientist, one of the founders of modern physics. Author of fundamental works on quantum mechanics, the theory of the atom, the atomic nucleus, and nuclear reactions.

Childhood and youth

Niels Bohr was born into the family of Christian Bohr, a professor of physiology at the University of Copenhagen, and Ellen Bohr, who came from a wealthy and influential Jewish family. The parents of Nils and his younger, beloved brother Harald (a future major mathematician) managed to make their sons' childhood happy and meaningful. The beneficial influence of the family, especially the mother, played a decisive role in the formation of their spiritual qualities.

Nils received his primary education at Gammelholm Grammar School, which he graduated from 1903 . During his school years he was an avid football player; later he became interested in skiing and sailing. At the age of twenty-three he graduated from the University of Copenhagen, where he acquired a reputation as an unusually gifted research physicist. His graduation project on determining the surface tension of water from the vibrations of a water jet was awarded a gold medal by the Royal Danish Academy of Sciences. IN 1908-11 Bohr continued to work at the university, where he carried out a number of important studies, in particular on the classical electronic theory of metals, which formed the basis of his doctoral dissertation.

Work in England

Three years after graduating from university, Bohr came to work in England. After a year in Cambridge with J. J. Thomson, Bohr moved to Manchester to work with Rutherford, whose laboratory at that time occupied a leading position. Here, by the time of Bohr's appearance, experiments were taking place that led Rutherford to the planetary model of the atom. More precisely, the model was still in its infancy. Experiments on the passage of alpha particles through pieces of foil led Rutherford to the belief that at the center of the atom there is a small charged nucleus in which almost the entire mass of the atom is concentrated, and much lighter electrons are located around the nucleus. Since the atom as a whole is electrically neutral, the total charge of all electrons must be equal in magnitude to the charge of the nucleus, but differ in sign from it. The conclusion that the charge of the nucleus must be a multiple of the charge of the electron was important, but there was still a lot of uncertainty. Thus, “isotopes” were discovered - substances with the same chemical properties, but with different atomic weights.

The problem of the atomic number of elements. Displacement law

Bohr's first important achievement in Rutherford's laboratory was his understanding that chemical properties are determined by the number of electrons in an atom, and therefore by the charge of the nucleus, and not by its mass, and this explains the existence of isotopes. Since an alpha particle is a helium nucleus with a charge of +2, then during alpha decay, when this particle flies out of the nucleus, the “daughter” element should be located in the periodic table two cells to the left of the “parent”, and during beta decay, when an electron flies out of the nucleus, one cell to the right. This is how the “law of radioactive displacements” was discovered. But this discovery was followed by others, much more important. They concerned the atomic model itself.

Rutherford-Bohr model

This model is often called "planetary" - in it, just as the planets revolve around the Sun, electrons move around the nucleus. But such an atom cannot be stable: under the influence of the Coulomb attraction of the nucleus, each electron moves with acceleration, and an accelerating charge, according to the laws of classical electrodynamics, must emit electromagnetic waves, losing energy. Quantitative calculations show that such “radiation instability” of the atom is catastrophic: in about a hundred-millionth of a second, all electrons would have to lose energy and fall onto the nucleus. But in reality nothing like this happens, and many atoms are quite stable. A problem arose that might seem insoluble. And it really could not be resolved without the involvement of radical new ideas. It was these ideas that were put forward by Bohr.

He postulated that (contrary to the laws of mechanics and electrodynamics) there are orbits in atoms in which electrons do not emit when moving. According to Bohr, an orbit is stable if the angular momentum of the electron located on it is a multiple of h/2p, where h is Planck’s constant. Radiation occurs only when an electron moves from one stable orbit to another, and all the energy released in this case is carried away by one radiation quantum. The energy of such a quantum, equal to the product of frequency n by h, in accordance with the law of conservation of energy, is equal to the difference between the initial and final energies of the electron (“Frequency Rule”). Thus, Bohr proposed to combine Rutherford's model ideas with the idea of quanta, first expressed by Planck in 1900 . Such a connection was fundamentally contrary to all the provisions and traditions of classical theory. But, at the same time, this classical theory was not completely rejected: the electron was considered as a material point moving according to the laws of classical mechanics, but of all the orbits, only those that met the “quantization conditions” were declared “allowed.”

The electron energies in such orbits are inversely proportional to the squares of integers - orbit numbers. Using the “frequency rule,” Bohr came to the conclusion that radiation frequencies must be proportional to the difference between the inverse squares of integers. This pattern had indeed already been established by spectroscopists, but until then it had not found its explanation.

Bohr explained not only the spectrum of the simplest atom - hydrogen, but also helium, including ionized helium, showed how to take into account the influence of nuclear motion, predicted the structure of filling electron shells, which made it possible to understand the physical nature of the periodicity of the chemical properties of elements - the periodic table of Mendeleev. For these works Bohr 1922 was awarded the Nobel Prize.

Bohr Institute in Copenhagen

After finishing his work with Rutherford, Bohr returned to Denmark, where he 1916 was invited as a professor at the University of Copenhagen. A year later he was elected a member of the Royal Danish Society (in 1939 he became its president).

IN 1920 Bohr creates the Institute of Theoretical Physics and becomes its director. In recognition of his services, the city provides Bor with the historic "Brewer's House" for the institute. This institute was destined to play an outstanding role in the development of quantum physics. Undoubtedly, the exceptional personal qualities of its director were of decisive importance here. He was constantly surrounded by collaborators and students (in reality there was no line between the first and second), who came to Bor from everywhere. F. Bloch, O. Bohr, W. Weiskopf, H. Casimir, O. Klein, H. Kramers, L. D. Landau, K. Meller, U. Nishika, A. Pais, L. belonged to his large international school. Rosenfeld, J. Wheeler and many others. "The Brewer's House" became a center of attraction for all theorists. W. Heisenberg came to Bohr more than once, just at the time when the “uncertainty principle” was being created, and E. Schrödinger had painful discussions with Bohr there, trying to defend the pure wave point of view. It was at the Bohr Institute that what determined the qualitatively new face of physics of the 20th century was formed.

The Rutherford-Bohr model was obviously inconsistent. It combined both the provisions of classical theory and what clearly contradicted them. To eliminate these contradictions, a radical revision of many of the basic provisions of the theory was required. Here, Bohr’s direct merits, and the role of his scientific authority, and simply his personal influence, were very great. It was Bohr who realized that to create a physical picture of the processes of the microworld, a different approach is needed than for the “world of big things” and he was one of the main creators of this approach. He introduced the concept of the uncontrolled influence of measurement procedures, of “additional” quantities - such that the more accurately one of them is determined, the greater the uncertainty of the other. The name of Bohr is associated with the probabilistic (so-called Copenhagen) interpretation of quantum theory and the consideration of many of its “paradoxes”. Of considerable importance here were discussions between Bohr and Einstein, who never came to terms with the probabilistic interpretation of quantum mechanics. To understand the laws of the microworld and their relationship with the laws of classical (i.e., non-quantum) physics, the principle of correspondence formulated by Bohr is of no small importance.

Nuclear topics

Bohr, starting from Rutherford with nuclear physics, constantly paid great attention to nuclear topics. IN 1936 he proposed the theory of a compound nucleus, and soon the droplet model, which played a significant role in the study of the problem of nuclear fission. Bohr predicted the spontaneous fission of uranium nuclei.

After the actual capture of Denmark by the Nazis, Bohr secretly left his homeland and was taken first to England (he almost died on the plane), and then to America, where he and his son Aage worked for the Manhattan Project in Los Alamos. In the post-war years, he paid great attention to the problem of nuclear arms control, the peaceful use of the atom, even addressed messages to the UN, and participated in the creation of the European Center for Nuclear Research. Judging by the fact that he did not refuse to discuss some aspects of the “atomic project” with the Soviet physicist, he found monopoly ownership of atomic weapons dangerous.

Bohr paid much attention to issues related to physics, including biology. He was invariably occupied with philosophical problems of natural science.

Bohr's moral and scientific authority was exceptionally high. Any, even fleeting, communication with him made an indelible impression. He spoke and wrote in such a way that it was clear: he was intensely looking for words that would express feelings and thoughts with the utmost precision and truth. V. L. Ginzburg was deeply right when he called Bohr uniquely delicate and wise.

Bohr was an honorary member of more than 20 academies of sciences in various countries and a laureate of many national and international prizes.

Their home was the center of very lively discussions on pressing scientific and philosophical issues, and throughout his life B. reflected on the philosophical implications of his work. He studied at the Gammelholm Grammar School in Copenhagen and graduated in 1903. B. and his brother Harald, who became a famous mathematician, were avid football players during their school years; Nils later became interested in skiing and sailing.

When B. was a physics student at the University of Copenhagen, where he became a bachelor in 1907, he was recognized as an unusually capable researcher. His thesis 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. 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 research helped Bohr realize early in his scientific career that classical theory could not fully describe the behavior of electrons.

After receiving his doctorate in 1911, B. went to the University of Cambridge, England, to work with J.J. Thomson, who discovered the electron in 1897. However, by that time Thomson had already begun to study other topics, and he showed little interest in B.’s dissertation and the conclusions contained therein. But B., meanwhile, became interested in the work of Ernest Rutherford at the University of Manchester. Rutherford and his colleagues studied issues of radioactivity of elements and the structure of the atom. B. moved to Manchester for several months at the beginning of 1912 and energetically plunged into these studies. He drew many consequences from the nuclear model of the atom proposed by Rutherford, which has not yet received wide recognition. In discussions with Rutherford and other scientists, B. worked out ideas that led him to the creation of his own model of the structure of the atom.

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 Margret Norlund. They had six sons, one of whom, Oge Bohr, also became a famous physicist.

Over the next two years, B. continued to work on problems arising in connection with the nuclear model of the atom. Rutherford proposed in 1911 that the atom consists of a positively charged nucleus around which negatively charged electrons orbit. This model was based on ideas that were experimentally confirmed in solid state physics, but it led to one intractable paradox. According to classical electrodynamics, an orbiting electron must constantly lose energy, giving it back in the form of light or another form of electromagnetic radiation. As its energy is lost, the electron must spiral toward the nucleus and eventually fall onto it, which would destroy the atom. In fact, atoms are very stable, and therefore 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 during his dissertation work. A possible solution to this paradox, he believed, could lie in quantum theory.

In 1900, Max Planck proposed that electromagnetic radiation emitted by hot matter does not come in a continuous stream, but in well-defined discrete portions of energy. Having called these units quanta in 1905, Albert Einstein extended this theory to electron emission that occurs when light is absorbed by certain metals (photoelectric effect). Applying the new quantum theory to the problem of atomic structure, B. suggested that electrons have certain allowed stable orbits in which they do not emit 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 classical theory, their orbits could be located at any distance from the nucleus, just as planets could, in principle, revolve in any orbit around the Sun.

Although Bohr's model seemed strange and a little mystical, it solved problems that had long puzzled physicists. In particular, it provided the key to separating the spectra of elements. When light from a luminous element (such as a heated gas of hydrogen atoms) passes through a prism, it produces not a continuous, all-color spectrum, but a sequence of discrete bright lines separated by wider dark regions. According to B.'s theory, each bright colored line (that is, each individual wavelength) corresponds to the light emitted by electrons as they move from one allowed orbit to another lower-energy orbit. B. derived a formula for the frequencies of lines 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. B.'s theory, published in 1913, brought him fame; his model of the atom became known as the Bohr atom.

Immediately appreciating the importance of B.'s work, Rutherford offered him a lecturer position at the University of Manchester - a post that Bohr held from 1914 to 1916. In 1916, he took up the post of professor 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 of Theoretical Physics in Copenhagen; With the exception of the period of the Second World War, when B. was not in Denmark, he led 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 particle aspects of matter and energy). During the 20s. Bohr's model of the atom was replaced by a more complex quantum mechanical model, based mainly on the research of his students and colleagues. Nevertheless, Bohr's atom played an essential role as a bridge between the world of atomic structure and the world of quantum theory.

Best of the day

B. was awarded the Nobel Prize in Physics in 1922 “for his services to the study of the structure of atoms and the radiation emitted by them.” At the presentation of the laureate, Svante Arrhenius, a member of the Royal Swedish Academy of Sciences, noted that B.’s discoveries “led him to theoretical ideas that differ significantly from those that underlay the classical postulates of James Clerk Maxwell.” Arrhenius added that the principles laid down by B. “promise abundant fruits in future research.”

B. wrote many works devoted to problems of epistemology (cognition) arising in modern physics. In the 20s he made a decisive contribution to what was later called the Copenhagen interpretation of quantum mechanics. Based on Werner Heisenberg's uncertainty principle, the Copenhagen interpretation assumes that the rigid laws of cause and effect that we are familiar with in the everyday, macroscopic world do not apply to intra-atomic phenomena, which can only be interpreted in probabilistic terms. For example, it is not even possible in principle to predict in advance the trajectory of an electron; instead, one can specify the probability of each of the possible trajectories.

B. 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 a quantum mechanical description of the macroscopic world must correspond to its description within classical mechanics. The principle of complementarity states that the wave and particle nature of matter and radiation are mutually exclusive properties, although both of these concepts 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 obviously contradictory interpretations, we are forced to do without visual models - this 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 with concepts that are formal in the sense that they lack the visual picture so familiar to us."

In the 30s B. turned to nuclear physics. Enrico Fermi and his colleagues studied the results of bombarding atomic nuclei with neutrons. B., together with a number of other scientists, proposed a droplet model of the nucleus, corresponding to many of the observed reactions. This model, which compared the behavior of an unstable heavy atomic nucleus to a fissile drop of liquid, 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 the Second World War immediately gave rise to speculation about how it could be used to release colossal energy. During a visit to Princeton in early 1939, B. determined that one of the common isotopes of uranium, uranium-235, is a fissionable material, which had a significant impact on the development of the atomic bomb.

In the first years of the war, B. continued to work in Copenhagen, under the conditions of the German occupation of Denmark, on the theoretical details of nuclear fission. However, in 1943, warned of the impending arrest, B. and his family fled to Sweden. From there, he and his son Auge flew to England in the empty bomb bay of a British military aircraft. Although B. considered the creation of an atomic bomb technically infeasible, work on creating such a bomb had already begun in the United States, and the Allies needed his help. At the end of 1943, Nils and Aage went to Los Alamos to participate in work on the Manhattan Project. The elder B. made a number of technical developments in creating the bomb and was considered an elder among the 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 persuade them to be open and frank with the Soviet Union regarding new weapons, and also pushed for the establishment of a system of arms control in the post-war period. However, his efforts were unsuccessful.

After the war, B. returned to the Institute of 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 50s. He also took part in the founding of the Nordic Institute for Theoretical Atomic Physics (Nordita) in Copenhagen, the joint scientific center of the Scandinavian states. During these years, B. continued to speak out 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. For his efforts in this direction, he received the first Atom for Peace Prize, established by the Ford Foundation in 1957.

Having reached the mandatory retirement age of 70 in 1955, B. resigned as a professor at the University of Copenhagen, 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 took great interest in the new field of molecular biology.

A tall man with a great sense of humor, B. was known for his friendliness and hospitality. “The benevolent interest in people shown by B. made personal relationships at the institute in many ways reminiscent of similar relationships in the family,” recalled John Cockroft in his biographical memoirs about B. Einstein once said: “What is surprisingly attractive about B. as a scientific thinker is this 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 century." B. died on November 18, 1962 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 from 1939 until the end of his life. In addition to the Nobel Prize, he received the highest honors from many of the world's leading scientific societies, including the Max Planck Medal of the German Physical Society (1930) and the Copley Medal of the Royal Society of London (1938). He has held honorary degrees from leading universities including Cambridge, Manchester, Oxford, Edinburgh, Sorbonne, Princeton, McGill, Harvard and Rockefeller Center.

This Danish scientist made a breakthrough in physics, becoming one of the creators of quantum theory. The famous physicist who helped create atomic weapons spent the rest of his life arguing that they were a huge responsibility and suggesting that governments of various countries abandon them.

Family and childhood

Niels Bohr was born in the capital of Denmark into the family of a very wealthy scientist and heir to a banking dynasty. His dad was a professor, taught physiology and medicine at the University of Copenhagen, and his colleagues twice nominated him for a Nobel in this field.

Since his parents often went out into the world and communicated with the true intellectuals of the city, Nils was interested in various sciences from childhood.

When he went to school, he was most interested in philosophy, physics and mathematics - all thanks to the frequent visits of his father's friends - famous scientists in these fields. In addition, he was interested in psychology. Together with his second cousin, who would eventually become a famous scientist in the field of Gestalt psychology, Edgar Rubin, Niels studied various textbooks in this direction.

But the young man lived not only for science, he was also very fond of football. He was even on the team playing at the 1908 Olympic Games - Denmark then took second place, losing to England.

Study and science

Eighteen-year-old Nils became a student at the University of Copenhagen and went to study at the Faculty of Physics and Mathematics. He also studied astronomy and chemistry.

While still a student, he made his first experiments and studied the vibrations of liquid jets in order to more accurately determine the surface of water tension.

In 1906, his achievements were highly appreciated - for the theoretical part, Niels was awarded a gold medal from the Royal Society of Denmark. Bohr spent the next three years researching his theory in practice. The results were published with reviews from then-popular scientists: Sir John William Strett and Sir William Ramsay, both of whom received the Nobel in 1904.

In 1910, Bohr became a master, and the following year he brilliantly defended his doctorate in statistical mechanics. In it, he deduced his theory - about the magnetic moment of electric charges in motion and in a stationary state. Nine years later, the same theorem was rediscovered by Johanna van Leuven, so in our time it bears the name of both scientists.

Bohr and Rutherford

In the autumn of 1911 Bohr arrived in Cambridge. He was given a scholarship of 2,500 crowns for an internship abroad. Therefore, he chooses England for his research, specifically the Cavendish Laboratory, in which the Nobel laureate in physics Sir John Thomson was the main one. But the cooperation did not work out. Thomson did not like Bohr, who openly pointed out the mistakes and errors of the venerable physicist; moreover, the Dane spoke poor English. Therefore, despite the genius of the mentor he chose, Bohr had to look for another university. And six months later he moved to Manchester, to the “father” of nuclear physics, Ernest Rutherford, also a Nobel laureate. Together they worked on models of the atom and how they change during radioactive decay. In Rutherford, Bohr found not only a mentor and colleague, but also a very close friend. When the scientist got married in 1912, he and his wife spent part of their honeymoon in Manchester, visiting Rutherford.

In 1913, Bohr published an article on the “Theory of deceleration of charged particles as they pass through matter.”

After returning to Copenhagen, Bohr taught at the university and also actively worked on the quantum theory of atomic structure. In the spring of 1913, he once again went to Manchester for a consultation with Rutherford. Then his article “On the Structure of Atoms and Molecules” was published in Philosophical Magazine. It is published in parts, the theoretical part is stretched from July to December. In it, Bohr describes the quantum theory of the hydrogen-like atom.

This work was a real revolution of that time. Even years later, physicists recognized that Bohr's research was the greatest step in the study of atoms and their structure.

Your own institute and Nobel

In 1914, Rutherford invited Bohr to live in Manchester and at the same time begin teaching mathematical physics at the university. The scientist remains there for the next two academic years. At the same time, he continues his research, on the basis of which he develops his theory, even trying to transfer it to multi-electron atoms. But the idea turns out to be a dead end.

In June 1916, Bohr returned to the capital and again began lecturing at the university in his department. But Bohr did not want to work under anyone’s leadership, so he turned to the government with a request to allocate money for the construction of a separate institute for himself and his like-minded people.

Four years later, the inauguration of the Institute of Theoretical Physics took place (nowadays it bears the name of Bohr).

In 1918, his article “On the quantum theory of line spectra” was published, in which he formulated the principle of correspondence and derived the relationship between quantum theory and classical physics.

In 1922, Bohr was awarded the Nobel Prize in Physics for his study of the structure of the atom. Bohr will announce all his discoveries in this field at an open lecture to students at the end of that year in Stockholm.

Another Einstein

In 1925, the concept of “quantum mechanics” appeared. As a result of many years of experiments and refutation of several theories, Bohr formulates the principle of complementarity. It is based on the theory that a microparticle receives its dynamic characteristics depending on what objects it is in relationship with. Some scientists considered this principle so important that they even proposed naming all of quantum mechanics after it, drawing an analogy with Einstein’s theory of relativity.

In the 1930s, Bohr became extremely interested in the topic of nuclear physics. So much so that his entire institute completely changed the direction of its developments.

In 1936, he formulated the process of nuclear reaction. A few years later, he proved that the nuclei of different trace elements are divided differently, depending on which neutrons cause this process.

World War II and nuclear weapons

When Hitler came to power in Germany, many scientists fled the country. Together with his brother, Bor helped them settle in Copenhagen. The physicist himself was under threat, because his mother had Jewish roots. But he decided to stay in the city until the last and defend his institute.

In 1941, he had a meeting with Werner Heisenberg, this physicist at that time collaborated in Nazi Germany on the development of nuclear weapons. But Bohr did not agree to help.

In 1943, he and his son fled to the United States, where until the end of the war they lived under other names and developed the atomic bomb.

Already working on the project, he realized the danger of such weapons, so he wrote more than one letter to Churchill and Roosevelt so that they should be wary of atomic energy. Another side, the USSR, also became interested in Bohr’s development; he was even invited to come there to exchange experiences, which the United States regarded as an attempt at espionage.

The physicist spent recent years giving lectures and writing philosophical articles. He considered his most important discovery, the principle of complementarity, to be applied in various fields: biology, psychology and culture.

Died at the age of 77 from a heart attack. Bohr's ashes are in Copenhagen in the family grave.

Bohr very often entered into discussions with Einstein. They often ended on a high note, but both considered each other close friends.
Since 1965, the Copenhagen Institute for Theoretical Physics has been called the Niels Bohr Institute. After the death of its founder and permanent leader, the Institute was headed by Aage Bor (until 1970).
Element 105 of the periodic table (dubnium), discovered in 1970, was known as nilsbohrium until 1997. In the same year, the name bohrium was approved for the 107th element, discovered in 1981.
Asteroid 3948, discovered in 1985, is named after Bohr.
In 1998, the play “Copenhagen” by English playwright Michael Frayn, dedicated to the historical meeting of Bohr and Rutherford, was published.

Titles and awards

Hughes Medal (1921)
Guthrie Medal and Prize (1922)
Nobel Prize in Physics (1922)
Matteucci Medal (1923)
Silliman Lecture (1923)
Barnard Medal (1925)
Franklin Medal (1926)
Max Planck Medal (1930)
Faraday Lecture (1930)
Copley Medal (1938)
Order of the Elephant (1947)
International Niels Bohr Gold Medal (1955) - an award was established in honor of N. Bohr and Bohr himself became its first laureate
Peaceful Atom Prize (English) (1957)
Rutherford Medal and Prize (1958)
Helmholtz Medal (1961)
Sonning Prize (1961)
Honorary academic degrees from Cambridge, Manchester, Oxford, Edinburgh, Sorbonne, Princeton, Harvard universities, McGill University, Rockefeller Center, etc.

Name: Niels Bohr

Age: 77 years old

Place of Birth: Copenhagen, Denmark

A place of death: Copenhagen, Denmark

Activity: Danish theoretical physicist

Family status: was married

Niels Bohr - biography

Hiroshima, Nagasaki, Chernobyl. In each of these tragedies, the atomic explosion claimed thousands of lives. Did the scientist guess what consequences his discoveries would lead to?

Childhood, family

Niels Bohr is a classic representative of Denmark's golden youth. He was born in 1885 in the historical center of Copenhagen, into a wealthy and educated family. His mother was the daughter of an influential banker. His father, a professor of physiology at the University of Copenhagen, was twice nominated for the Nobel Prize in Physiology or Medicine.

From a young age, he took Nils and his younger brother Harald to amazing places in the country - lighthouses, shipyards and clock towers. And every time he repeated: “There are many secrets in the world. Learn to see the invisible!”

Niels Bohr - education

His father's upbringing bore fruit: at school, Nils became the best in mathematics and physics, then easily entered a prestigious university. A lanky student with a big head amazed professors with his unconventional thinking. Where others found only one solution to a problem, Bohr found a dozen. “Why are you making life difficult for yourself? - the teachers were perplexed. “After all, there are algorithms!” “Only new paths will move science forward!” - he answered.

Even standing at the goal (Bohr played for the Danish national football team), he managed to write down formulas on scraps of paper and his bare hands.

The future scientist was not without a sense of humor. He once performed incredibly poorly at a seminar. He got out of an awkward situation in a unique way: “I heard so many bad speeches today that I decided to take revenge on everyone!”

His father did not live to see Nils defend his doctoral dissertation for a couple of months. However, the young physicist no longer needed his support. He stood on the threshold of great discoveries and great love.

Having become the best graduate of the University of Copenhagen, Bohr received a grant for an internship in Cambridge. He expected a lot from his trip to England. After all, it was there that Joseph Thomson, Nobel Prize laureate in physics, worked. However, Nils could not find a common language with him.

Why didn't the two geniuses get along? According to one version, the Dane spoke poor English; according to another, he pointed out a mistake to Thomson. Thomson was the author of a model of the atom in which the atom was represented as a ball with a positively charged substance inside, and in this substance, like raisins in a cupcake, there were negatively charged electrons. Bohr could not agree with this model and proved to Thomson that it was wrong. He harbored a grudge against both himself and the overly smart guest. The physicists parted in silence, with an unpleasant aftertaste in their souls.

Niels Bohr - biography of personal life

Returning to Copenhagen, Niels met Margaret Norlund, the daughter of a pharmacist. And 3 years later, in the summer of 1912, the lovers got married. Six sons were born to this marriage. One can only guess how the spouses understood each other. Margaret knew nothing about physics, but was ready to listen to her husband for hours. Bohr, in turn, could not think silently. Every evening, walking around the kitchen, he thought aloud about the structure of molecules and nuclei. At the same time, Margaret managed to both prepare and take notes of his speeches.

Bohr was extremely inspired by love and family well-being. In just a few years, he not only developed and refined the theory of atomic structure, but also achieved the creation of the Institute of Theoretical Physics in Copenhagen, which now bears his name. And this was during the years of the European crisis, in the midst of the First World War!

At the age of 37, Bohr received the Nobel Prize for his outstanding achievements in atomic physics. Was this award deserved and timely? Controversial issue. Firstly, Niels's work seemed incomplete, contradictory and clearly unsuitable for practical use. And secondly, they were the result of research by a dozen physicists who worked with Bohr. Among them are Lev Landau, Ernest Rutherford and others, including the son of the scientist Ore Bohr. Both then and now it remains unclear which sections of the atomic theory belonged to Bohr himself and which to his colleagues.

The most surprising thing is that the institute, like Bohr himself, rarely worked on schedule. And if insight descended on a scientist in the middle of the night, he would wake up both his wife and a good half of his colleagues. “Come to me urgently! - Nils shouted into the telephone receiver. - Let's think!” The young German Werner Heisenberg also began his scientific career in Bohr's night kitchen. After 20 years, teacher and student will meet again - in the middle of Europe, shackled by fascism.

Bohr's discoveries

Since 1936, Bohr studied the processes of nuclear fission more and more deeply, and in 1938 he created the first charged particle accelerator in Europe - the cyclotron. After the occupation of Denmark by the Nazis, the scientist chose to stay in Copenhagen, despite his half-Jewish origin: he wanted to protect the institute from the encroachments of the occupation authorities.

Did he understand the danger of his discoveries? Or did he sincerely believe that they would benefit humanity? Bohr was brought out of his ideal-romantic “hibernation” by the same Werner Heisenberg. In October 1941, the already eminent German physicist and head of the Nazi atomic project specially arrived in Copenhagen to meet with his former teacher.

The meeting was short-lived and probably the most mysterious in the entire history of World War II. According to Bohr, Heisenberg suggested that he create an atomic bomb for Hitler. According to Heisenberg himself, he wanted to assure the teacher that conscientious Germans would definitely not agree to create a bomb, and their work on the atomic project was pursuing exclusively peaceful goals.

Much is unclear in this story. Why, for example, did the Nazis, knowing about Bohr's Jewish roots, simply not arrest him? After all, they sent his 84-year-old aunt, the famous Danish teacher Hannah Adler, to a concentration camp. And for what reason did the Americans decide to evacuate Bohr only after his meeting with Heisenberg? Finally, why did the scientist himself, once in the USA, begin to create nuclear weapons with such enthusiasm?..

Be that as it may, already at the beginning of 1944, Bohr lost his last illusions regarding the peaceful use of the atom. Realizing his personal guilt in the approaching tragedy, he tried to prevent it: in May he met with Churchill, in July he sent a memorandum to Roosevelt, and in the fall he turned to Stalin through Pyotr Kapitsa. And in response - silence. It meant only one thing: if necessary, the allies would use nuclear weapons. Pandora's box has opened.

On July 16, 1945, the Americans detonated the first atomic bomb in New Mexico, and on August 6 and 9 they dropped charges on Hiroshima and Nagasaki. Bohr responded to the incident with a long article in Time, accusing the United States of unjustified cruelty. But did this calm his conscience? Another unanswered question...

The horrors of World War II changed Bohr greatly. He became interested in biology, psychology, philosophy of natural science, and even the peculiarities of language in science and life. Despite all the “iron curtains,” he came to Moscow many times to give lectures on humanism. In a world full of imperfections, he desperately sought harmony.

In 1950, the scientist wrote an open letter to the UN, in which he called on the superpowers not to repeat the US nuclear crimes. And 7 years later, he was the first in history to be awarded the “For Peaceful Atom” Prize.

He died in his native Copenhagen in 1962 - in his sleep, due to cardiac arrest. It was warm November outside the window, and the grandchildren were playing in the next room.

“We must remember that each of us is part of nature,” Niels Bohr wrote shortly before his death. “Living in harmony with it is our great duty and main goal.” A wonderful message for future generations.

Hello! Let's assume this is an equilateral triangle. And I want to create another shape from this equilateral triangle. I want to do this by dividing each side of the triangle into three equal parts... Three equal parts... This equilateral triangle may not be drawn perfectly, but I think you'll understand. And in each middle part I want to build one more equilateral triangle. So in the middle part, right here, I'm going to make another equilateral triangle... Here too... And here's another equilateral triangle. And from an equilateral triangle it turned out something like a Star of David. And I want to do this again, i.e. I will divide each side into three equal parts, and in each middle part I will draw another equilateral triangle. An equilateral triangle in each middle part... I'll do this for each side. Here and here... I think you get the idea... Here, here, here... I'm almost done with this step... This is what the figure will look like now. And I can do this again - once again divide each segment into three equal parts and in each middle part draw one equilateral triangle: here, here, here, here, and so on. I think you understand where this is going... And I could continue to do this forever. In this lesson I want to think about what will happen to this figure. What I'm drawing now, i.e. if we continue to do this indefinitely, at each step we will divide each side of the figure into three equal parts, and then add one equilateral triangle to each middle part - this figure presented here is called a Koch snowflake. Koch's snowflake... It was first described by this gentleman, a Swedish mathematician whose name was Niels Fabian Helge von Koch. And this snowflake is one of the earliest examples of fractals. Those. this is a fractal. Why is it considered a fractal? Because it looks very much like itself at any scale at which you view it. For example, if you look at it on this scale, then in this part you see a bunch of triangles, but if you enlarge, for example, this part, then you will still see something like this figure. And if you enlarge it again, you will see the same figure. Those. A fractal is a figure made up of several parts that, at any scale, look similar to the entire figure. What’s especially interesting (and why I included such a lesson in the geometry playlist) is that the perimeter of this figure is equal to infinity. Those. If you build a figure like the Koch snowflake, you will have to add another small equilateral triangle to each small triangle an infinite number of times. And to show that the perimeter of such a figure is equal to infinity, let's look at one of its sides here... Here is one of its sides. If we started with the original triangle, this is where this side would be. And suppose its length is equal to S. If we divide this side into three equal parts, then the length of this part will be equal to S/3, the length of this part will also be S/3... Actually, I’d better write below: S/3, S/ 3, S/3. Then we draw an equilateral triangle to the middle part. Like this. Those. the length of each side is now S/3. And the length of this entire new part... It can no longer be called just a line, because there is now a triangle on it... The length of this part, this side, is now equal not to S, but [(S/3)*4 ]. Previously, the length was equal to [(S/3)*3], but now we have one, two, three, four segments of length S/3. Now, after we have added one triangle to the original side, the length of our new side will be equal to 4 times S/3, i.e. (4/3)*S. So, if the original perimeter (i.e. if there was only one triangle) was P₀, then after adding one set of triangles, the perimeter of P1 would be 4/3 times the original perimeter. Because the length of each side of the figure will now be 4/3 times greater than originally. Those. the original perimeter Р₀ consisted of three sides, then each of their sides began to have a length 4/3 times greater, which means that the new perimeter Р₁ will be equal to 4/3 times Р₀. And after adding the second set of triangles, the perimeter of P₂ will be equal to 4/3 times P₁. Those. after each addition of new triangles, the perimeter of the figure becomes 4/3 times larger than the previous perimeter. And if you add new triangles an infinite number of times, then it turns out that when calculating the perimeter, you multiply some number by 4/3 an infinite number of times - therefore, you get an infinite perimeter value. This means that the perimeter with the index “infinity” P∞ (the perimeter of the figure if you add triangles to it an infinite number of times) is equal to infinity. Well, it's interesting, of course, to imagine a figure that has an infinite perimeter, but what's more interesting is that this figure actually has a finite area. When I say finite area, I mean a limited amount of space. I can draw some shape around and this Koch snowflake will never go beyond its boundaries. And to think... Well, I won't give a formal proof. Let's just think about what happens on either side of the figure. So, for the first time, at the first separation step, this triangle appears... At the second step, these two triangles appear, and also these two. And then triangles appear here, here, here, here, etc. But notice that you can keep adding more and more triangles, essentially an infinite number of them, but you will never get beyond this point here. The same restriction will be observed for this side, also for this side, and for this, for this, and also for this. Those. even if you add triangles an infinite number of times, the area of this figure, this Koch snowflake, will never be greater than the area of this bounding hexagon... Well, or greater than the area of this figure... I draw an arbitrary figure that extends beyond the hexagon. You could draw a circle that extends beyond it... So, this figure drawn in blue or this hexagon drawn in purple, of course, has a certain area. And the area of this Koch snowflake will always be limited, even if you add triangles to it an infinite number of times. So there's a lot of interesting stuff here. The first is that it is a fractal. You can increase it in size and at the same time we will see the same figure. The second is an infinite perimeter. And the third is the final area. Now you may say: “But these are too abstract things, they don’t exist in the real world!” But there's this fun fractal experiment that people talk about. This is a calculation of the perimeter of England (well, actually, this can be done for any country). The outline of England looks something like this... So the first way you could approximate the perimeter is to measure this distance, plus this distance, plus this distance, plus this distance, plus this distance and this distance . Then you might think, well, this shape has a finite perimeter. It is clear that its area is finite. But it is still clear that this is not the best way to calculate the perimeter; you can use a better method. Instead of this approximate calculation, you can draw smaller lines around the border, and this will be more accurate. Then you'll think, okay, this is a much better approximation. But, suppose, if you enlarge this figure... If you enlarge it well, then the border will look something like this. .. It will have curves like this... And, in fact, when you calculated the perimeter here, you simply calculated its height, like this. Of course, this will not be a perimeter, and you will need to divide the border into many parts, approximately like this, to get an accurate perimeter. But even in this case, we can say that this is not an entirely accurate calculation of the perimeter, because If you enlarge this part of the line, it will turn out that in the enlarged version it looks different - for example, like this. Accordingly, the division lines will look different - like this. Then you will say: “Eh, no, we need to be more precise!” And you will divide this line into parts even more. And this can be done endlessly, with millimeter precision. The real border of an island or continent (or anything else) is actually a fractal, i.e. a figure with an infinite perimeter, the calculation of which can reach, so to speak, the atomic level. But still the perimeter will not be accurate. But this is almost the same phenomenon as Koch's snowflake, and it can be interesting to think about it. That's all for today. See you in the next lesson!