Quantum studies took a massive leap in the middle of the 20th century, with a host of European scientists successfully attempting to unlock the mysteries of the atom. In these endeavours, Danish physicist Niels Henrik David Bohr made foundational contributions to understanding the atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922.
Bohr was born in Copenhagen on October 7, 1885, the second of three children of Christian Bohr, a professor of physiology at the University of Copenhagen, and his wife Ellen. In 1903, Bohr enrolled as an undergraduate at the University of Copenhagen, majoring in physics, while also studying astronomy and mathematics. At the university, he came under the guidance of Prof C Christiansen, and earned his Master’s degree in Physics in 1909 and Doctorate in 1911. In 1912, he married Margrethe Nørlund. As part of his contributions, Bohr developed the ‘Bohr Model’ of the atom, in which he proposed that the electron was able to occupy only certain orbits around the atomic nucleus. This means that electrons’ energy levels are discrete and that the electrons revolve in stable orbits around the nucleus, but can jump from one energy level to another. This atomic model was the first to use quantum theory, in that the electrons were limited to specific orbits around the nucleus. Bohr used his model to explain the spectral lines of hydrogen.
He also conceived the complementarity principle, wherein items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr’s thinking in both science and philosophy. In 1920, Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute. He also predicted the properties of a new zirconium-like element, which was named ‘hafnium’, after the Latin name for Copenhagen, where it was discovered. Later, the element ‘bohrium’ was named after him. During World War II, Bohr was part of the British mission to the Manhattan Project, a classified programme to make the first atomic bombs. After the war, he called for international cooperation on nuclear energy. Besides, Bohr was a footballer, philosopher, and promoter of scientific research. He passed away on November 18, 1962, in the city of his birth.