Niels Bohr

The Incredible Life And Work Of Niels Bohr, One Of The Pioneers Of Quantum Theory.

Yesterday, the 2020 Nobel Prize in physics was announced and the perplexing black holes emerged as proud recipients of it. But, do you remember who bagged this noble honor back in 1922? Well, 98 years ago, Niels Bohr became its competent beneficiary for his elegant services in the investigation of the structure of atoms and of the radiation emanating from them. So today, on Bohr’s 135th birth anniversary,  let’s go on a ride to revisit his legacy!

Niels Bohr  (Image: Wikipedia)
Niels Bohr

Early life and Education :

Born on 7 October 1885, to a well-educated family in Copenhagen, Denmark, Niels Bohr was the second of three children of Christian Bohr and Ellen Bohr. Christian Bohr always believed his son to be someone very special. Neils Bohr’s father was appointed as a professor of physiology at the University of Copenhagen,  so Niels got exposed to an atmosphere of scientific and critical thinking in his childhood itself.

When Bohr was seven, he received his education at Gammelholm Latin School. During his last two years at school, Niels specialized in mathematics and physics. And it is often quoted that at a certain point in time,  Niels became so exceptional in these subjects that his mathematics teacher became somewhat frightened of his exceptional pupil. In physics too,  Bohr studied texts ahead of the class finding errors in them. In 1903,
owing to his intellectual capabilities, Bohr enrolled as an undergraduate at Copenhagen University where his major was physics with mathematics and astronomy being his minors.

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At his university, Neils Bohr could not carry out physics experiments since there was no physics laboratory. However,  his research temperament motivated him to carry out his experiments in his father’s physiology laboratory. Doing so, he uniquely investigated a method for measuring the surface tension of liquids and this analysis eventually won him the Gold Medal for 1906 from the Royal Danish Academy of Sciences. 

Bohr received his Master’s degree from the University of Copenhagen in 1909,  followed by a doctorate in 1911 with a dissertation on the electron theory of metals. Bohr dedicated his doctorate thesis to the memory of his beloved father who had actually enlightened the path of discoveries for him.

Why Niels Bohr is known as the father of Quantum theory?

In September 1911, Bohr got an opportunity to travel to England. It was the time when most of the theoretical work on the structure of atoms and molecules was being done. There, he met Rutherford, who eventually became Bohr’s role model both for his personal and scientific qualities. Shortly before Niels Bohr and Ernest Rutherford met, Rutherford had published a major work showing that the bulk of the mass of an atom resided in the nucleus.

Bohr received an invitation from Rutherford to conduct post-doctoral work at Victoria University of Manchester. Eventually using quantum ideas due to Planck and Einstein, Bohr modified Rutherford’s model of the atom into what came to be known as the Rutherford-Bohr model. Bohr conjectured that an atom could exist only in a discrete set of stable energy states. Bohr introduced the idea that an electron could drop from a higher-energy orbit to a lower one,  and in doing so, it emits a quantum of discrete energy. This concept was successful in explaining the hydrogen spectrum and also became a basis for what is now known as the old quantum theory.

Also watch: The genius of S.N. Bose

The Incredible Life And Work Of Niels Bohr, One Of The Pioneers Of Quantum Theory. 2
Bohr’s atomic model of a nitrogen atom. (Image: Encyclopædia Britannica, Inc)

Although Bohr’s model of the atom has now been superseded with the more advanced and precise models, it is still one of the best-known models of the atom, and often appears in high school physics and chemistry texts. Bohr often talked of atomic stability and electrodynamic theory giving an account of the origins of quantum theory. Not only this, but Niels Bohr also put forward his principle of complementarity which gave a physical interpretation of Heisenberg’s uncertainty relations. Bohr proposed the complementarity of certain entities as a fundamentally new interpretation of the foundations of quantum theory. 

Although Einstein expressed grave doubts about Bohr’s interpretation and Bohr, Einstein and Ehrenfest spent several hours in deep discussion, but it was Niels’s view that eventually prevailed in those discussions. Niels Bohr believed that his idea of complementarity could play an important role in fields other than quantum physics, so he worked on these ideas throughout the rest of his life.

Other Notable Contributions And Achievements:

Apart from contributing to quantum theory, Bohr is also acknowledged for his theoretical description of the periodic table of elements around 1920, his theory of the atomic nucleus being a compound structure in 1936, and his understanding of uranium fission in terms of the isotope 235 in 1939. Throughout his scientific career,  Bohr held several teaching and honorary positions.

In 1917, Niels Bohr got elected to the Royal Danish Academy of Sciences. There, he planned to have an Institute of Theoretical Physics in Copenhagen (now known as The Niels Bohr Institute). This dream got accomplished in 1921. Bohr became its first director and held this position for the rest of his life. For his scientific contributions,  Bohr was honored with numerous awards and honors,  with the 1922 Nobel Prize in Physics being one of them.

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In 2010, on the eve of the 125th birth anniversary of Niels Bohr, the Niels Bohr Institute established the Niels Bohr Institute Medal of Honour, an annual award for “a particularly outstanding researcher who is working in the spirit of Niels Bohr: International cooperation and the exchange of knowledge”.

Niels Bohr was married to Margrethe Nørlund, and the marriage proved out to be a happy one. Throughout his life, Margrethe remained his most-trusted adviser. Neils and Margrethe had six sons, the fourth of whom, Aage N. Bohr, shared a third of the 1975 Nobel Prize for Physics in recognition of the collective model of the atomic nucleus proposed in early 1950,  thus following his father’s footsteps.

Bohr’s insight into the prevailing model of the atom has laid the groundwork for much of the technological advancements including laser beams and quantum computing. Undoubtedly,  Niels Bohr is one such mind whose revolutionary theories have helped in shaping the research community worldwide. And it wouldn’t be over-exaggerating if I say that only a few scientists have made as much impact on the modern world as Niels Bohr!

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