Monday, October 7, 2013

Niels Bohr and the beginnings of Quantum Mechanics

Niels Bohr
(1885 - 1962)
On October 7, 1885, Danish physicist and Nobel Laureate Niels Bohr was born. Bohr made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922.

Niels Bohr grew up in a home full of academics. Only his brother became a professional football player and also Bohr played this sport passionately. After school, he enrolled at Copenhagen University majoring in physics. Other subjects Bohr's were mathematics, astronomy and even philosophy in which he mostly excelled. Royal Danish Academy of Sciences and Letters once set up a student contest for innovative methods measuring the surface tension of liquids. Bohr became a glass blower to build adequate instruments for his experiments and he won the competition. Still, he was always behind in the competition with his younger brother Harald, who earned his masters degree as well as his doctorate before Niels did.

In the 1910s, Niels Bohr traveled around to meet scientists and show them his achieved work. At Cambridge he experimented with cathode rays, but could not impress J. J. Thomson. When continuing to the Victoria University of Manchester, Bohr got to know Ernest Rutherford. Rutherford enjoyed Bohr's works and invited him for post-doctoral studies before starting a position as privatdocent at the University of Copenhagen. He managed to publish several scientific works there. Influenced from Rutherford's model of nuclear structures, Bohr combined them with the quantum theories of Max Planck. The result was the Bohr atom model, which introduced the idea of electrons travelling in orbits around the atom's nucleus. Further theories were applied here and became known as the foundations of the old quantum theory (as it is called on this day). Bohr's research results met mixed feelings. Ernest Rutherford and Albert Einstein however thought of it as a gigantic breakthrough in physics.

In 1917, the young scientist Bohr started planning an Institute of Theoretical Physics, for which he received mostly support from private and governmental organisations. In 1921, Bohr became its director and today it is known as the Niels Bohr Institute. As Bohr continued his studies on his atom model, he was awarded the Nobel Prize in physics in 1922 for his works in quantum mechanics. Heisenberg started working for Niels Bohr at the University of Copenhagen in 1926 and developed the mathematic foundations for quantum mechanics there. In the following year, Heisenberg developed his uncertainty principle, which Bohr used for improvements of his own theories and ideas. Through the years, Bohr and Albert Einstein had lively but good-natured discussions on various aspects, such as the determinism of classical physics. Einstein preferred this term over quantum mechanics and detailed philosophical discussions evolved.

At yovisto, you may enjoy an introductory lecture on Bohr's Quantum Mechanics by Saul Hernandez. 


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