NIELS BOHR: BIOGRAPHY AND CONTRIBUTIONS - SCIENCE - 2025

Niels Bohr (1885-1962) was a Danish physicist who was awarded the Nobel Prize in Physics in 1922 for his research related to the structure of atoms and their radiation levels. Raised and educated in European lands, in the most prestigious English universities, Bohr was also a renowned researcher and curious about philosophy.

He worked alongside other renowned scientists and Nobel Laureates, such as JJ Thompson and Ernest Rutherford, who encouraged him to continue his research in the atomic area.

Bohr's interest in atomic structure led him to move between universities to find one that would give him the space to develop his research on his own terms.

Niels Bohr started from the discoveries made by Rutherford and continued to develop them until he could put his own imprint on them.

Bohr came to have a family of more than six children, was the tutor of other scientific eminent such as Werner Heisenberg and president of the Royal Danish Academy of Sciences, as well as a member of other scientific academies around the world.

Biography

Niels Bohr was born on October 7, 1885 in Copenhagen, the capital city of Denmark. Niels's father was named Christian and he was a professor of physiology at the University of Copenhagen.

For her part, Niels' mother was Ellen Adler, whose family was economically privileged, having influence in the Danish banking environment. Niels' family situation allowed him to have access to an education considered privileged at the time.

Studies

Niels Bohr became interested in physics, and he studied it at the University of Copenhagen, from which he obtained a master's degree in physics in 1911. Later he traveled to England, where he studied at the Cavendish Laboratory of the University of Cambridge.

The main motivation for studying there was to receive the tutelage of Joseph John Thomson, a chemist of English origin who received the Nobel Prize in 1906 for the discovery of the electron, specifically for the studies he did on how electricity moves through gases.

Bohr's intention was to translate his doctoral thesis into English, which was precisely related to the study of electrons. However, Thomson showed no real interest in Bohr, which is why the latter decided to leave there and set his course for the University of Manchester.

Relationship with Ernest Rutherford

While at the University of Manchester, Niels Bohr had the opportunity to share with the British physicist and chemist Ernest Rutherford. He had also been Thomson's assistant and later won the Nobel Prize. Bohr learned a lot from Rutherford, especially in the field of radioactivity and models of the atom.

With the passage of time, the collaboration between the two scientists grew and their friendship grew. One of the events in which both scientists interacted in the experimental field was related to the model of the atom proposed by Rutherford.

This model was true in the conceptual field, but it was not possible to conceive it by framing it in the laws of classical physics. Given this, Bohr dared to say that the reason for this was that the dynamics of the atoms were not subject to the laws of classical physics.

Nordic Institute for Theoretical Physics

Niels Bohr was considered a shy and introverted man, yet a series of essays that he published in 1913 earned him wide recognition in the scientific field, making him a recognized public figure. These essays were related to his conception of the structure of the atom.

In 1916 Bohr traveled to Copenhagen and there, in his hometown, he began to teach theoretical physics at the University of Copenhagen, where he studied.

Being in that position and thanks to the fame that had previously acquired, Bohr obtained the sufficient money that was necessary to create in 1920 the Nordic Institute of Theoretical Physics.

The Danish physicist directed this institute from 1921 to 1962, the year in which he died. Later, the institute changed its name and was called the Niels Bohr Institute, in honor of its founder.

Very soon, this institute became a reference in terms of the most important discoveries that were being made at the time related to the atom and its conformation.

In a short time the Nordic Institute for Theoretical Physics was on a par with other universities with more tradition in the area, such as the German universities of Göttingen and Munich.

Copenhagen School

The 1920s were very important to Niels Bohr, since during those years he issued two of the fundamental principles of his theories: the principle of correspondence, issued in 1923, and the principle of complementarity, added in 1928.

The aforementioned principles were the basis on which the Copenhagen School of quantum mechanics, also called the Copenhagen Interpretation, began to form.

This school found opponents in great scientists such as Albert Einstein himself, who, after opposition to various approaches, ended up recognizing Niels Bohr as one of the best scientific researchers of the time.

On the other hand, in 1922 he received the Nobel Prize in Physics for his experiments related to atomic restructuring, and that same year his only son, Aage Niels Bohr, was born, who eventually studied at the institute that Niels presided over. Later he became its director and, in addition, in 1975 he received the Nobel Prize in Physics.

During the 1930s Bohr settled in the United States and focused on publicizing the field of nuclear fission. It was in this context that Bohr determined the fissionable characteristic of plutonium.

At the end of that decade, in 1939, Bohr returned to Copenhagen and received the appointment of president of the Royal Danish Academy of Sciences.

Second World War

In 1940 Niels Bohr was in Copenhagen and, as a consequence of World War II, three years later he was forced to flee to Sweden together with his family, because Bohr had Jewish origins.

From Sweden, Bohr traveled to the United States. There he settled and joined the collaborative team for the Manhattan Project, which produced the first atomic bomb. This project was carried out in a laboratory located in Los Alamos, New Mexico, and during his participation in said project Bohr changed his name to Nicholas Baker.

Homecoming and death

At the end of the Second World War, Bohr returned to Copenhagen, where he again became director of the Nordic Institute for Theoretical Physics and always advocated the application of atomic energy with useful objectives, always seeking efficiency in different processes.

This inclination is due to the fact that Bohr was aware of the great damage that could be caused by what he discovered, and at the same time he knew that there was a more constructive utility for this type of powerful energy. So, from the 1950s, Niels Bohr dedicated himself to giving conferences focused on the peaceful use of atomic energy.

As we mentioned earlier, Bohr did not miss the magnitude of atomic energy, so in addition to advocating for its proper use, he also stipulated that it was governments who should ensure that this energy was not used in a destructive way.

This notion was introduced in 1951, in a manifesto signed by more than a hundred renowned researchers and scientists at the time.

As a consequence of this action, and of his previous work in favor of the peaceful use of atomic energy, in 1957 the Ford Foundation awarded him the Atoms for Peace award, given to personalities who sought to promote the positive use of this type of energy.

Niels Bohr died on November 18, 1962, in his hometown of Copenhagen, at the age of 77.

Contributions and discoveries of Niels Bohr

Bohr and Albert Einstein

Model and structure of the atom

Niels Bohr's atomic model is considered one of his greatest contributions to the world of physics and science in general. He was the first to exhibit the atom as a positively charged nucleus surrounded by orbiting electrons.

Bohr managed to discover the internal working mechanism of an atom: electrons are able to orbit independently around the nucleus. The number of electrons present in the outer orbit of the nucleus determines the properties of the physical element.

To obtain this atomic model, Bohr applied Max Planck's quantum theory to the atomic model developed by Rutherford, obtaining as a result the model that earned him the Nobel Prize. Bohr presented the atomic structure as a small solar system.

Quantum concepts at the atomic level

What led Bohr's atomic model to be considered revolutionary was the method he used to achieve it: the application of quantum physics theories and their interrelationship with atomic phenomena.

With these applications, Bohr was able to determine the movements of the electrons around the atomic nucleus, as well as the changes in their properties.

In the same way, through these concepts, he was able to obtain a notion of how matter is capable of absorbing and emitting light from its most imperceptible internal structures.

Discovery of the Bohr-van Leeuwen theorem

The Bohr-van Leeuwen theorem is a theorem applied to the area of ​​mechanics. Worked first by Bohr in 1911 and later supplemented by van Leeuwen, the application of this theorem was able to differentiate the scope of classical physics from quantum physics.

The theorem states that the magnetization resulting from the application of classical mechanics and statistical mechanics will always be zero. Bohr and van Leeuwen managed to glimpse certain concepts that could only be developed through quantum physics.

Today the theorem of both scientists is applied successfully in areas such as plasma physics, electromechanics and electrical engineering.

Principle of complementarity

Within quantum mechanics, the principle of complementarity formulated by Bohr, which represents a theoretical and resulting approach at the same time, maintains that objects subjected to quantum processes have complementary attributions that cannot be observed or averaged simultaneously.

This principle of complementarity is born from another postulate developed by Bohr: the Copenhagen interpretation; fundamental to the research of quantum mechanics.

Copenhagen Interpretation

With the help of scientists Max Born and Werner Heisenberg, Niels Bohr developed this interpretation of quantum mechanics, which made it possible to elucidate some of the elements that make mechanical processes possible, as well as their differences. Formulated in 1927, it is considered a traditional interpretation.

According to the Copenhagen interpretation, physical systems do not have definite properties before they are subjected to measurements, and quantum mechanics is only capable of predicting the probabilities by which the measurements made will yield certain results.

Structure of the periodic table

From his interpretation of the atomic model, Bohr was able to structure the periodic table of elements existing at that time in more detail.

He was able to state that the chemical properties and the binding capacity of an element are closely related to its valence charge.

Bohr's work applied to the periodic table led to the development of a new field of chemistry: quantum chemistry.

Similarly, the element known as Boron (Bohrium, Bh), receives its name in homage of Niels Bohr.

Nuclear reactions

Using a proposed model, Bohr was able to propose and establish the mechanisms of nuclear reactions from a two-stage process.

By bombarding low-energy particles, a new, low-stability nucleus is formed that will eventually emit gamma rays, while its integrity decays.

This discovery by Bohr was considered key in the scientific area for a long time, until it was worked on and improved, years later, by one of his sons, Aage Bohr.

Explanation of nuclear fission

Nuclear fission is a nuclear reaction process whereby the atomic nucleus begins to divide into smaller parts.

This process is capable of producing large amounts of protons and photons, releasing energy at the same time and constantly.

Niels Bohr developed a model that made it possible to explain the nuclear fission process of some elements. This model consisted of observing a drop of liquid that would represent the structure of the nucleus.

In the same way that the integral structure of a drop can be separated into two similar parts, Bohr managed to show that the same can happen with an atomic nucleus, being capable of generating new processes of formation or deterioration at the atomic level.

References

1. Bohr, N. (1955). Man and physical science. Theoria: An International Journal for Theory, History and Foundations of Science, 3-8.
2. Lozada, RS (2008). Niels Bohr. University Act, 36-39.
3. Nobel Media AB. (2014). Niels Bohr - Facts. Retrieved from Nobelprize.org: nobelprize.org
4. Savoie, B. (2014). A rigorous proof of the Bohr-van Leeuwen theorem in the semiclassical limit. RMP, 50.
5. The Editors of Encyclopædia Britannica. (November 17, 2016). Compound-nucleus model. Retrieved from Encyclopedia Britannica: britannica.com.