It is 100 years since Niels Bohr developed the model of the atom that paved the way for many other inventions such as the transistor and the Laser

Professor K. Smiles, dean of Academic Affairs at the Coimbatore Institute of Engineering and Technology, shares an anecdote about Niels Bohr, the Danish Physicist who won the Nobel Prize in Physics in 1922. When he nailed a horseshoe above the front door of his country cottage in Tisvilde, a visitor asked him: “Dr. Bohr, being a great scientist, do you really believe that a horseshoe above the entrance of your home brings luck?” “No,” answered Bohr, “I certainly do not believe in this superstition. But, do you know?” he whispered in the visitor’s ears: “they say that it does bring luck even if you don’t believe in it!”

A radical thinking

June 2013 marks the 100th year of Niels Bohr’s theory on the structure of atom — with the nucleus at the centre and electrons orbiting around it — which he compared to the planets orbiting the Sun.

Niels Bohr’s discovery came at a time when there was confusion on what’s happening inside an atom, about the protons, electrons and neutrons. It was a radical and revolutionary discovery, the first major breakthrough in man’s thinking.

It was Greek philosopher Democritus who began the search for the structure of matter more than 2400 years ago. Even then, simple experiments suggested that the atoms were made up of still smaller particles that were electrically charged. “Though in the 1900s people knew about the atoms, they didn’t know about the structure of an atom,” says Professor K. Sakthivel, Professor of Physics at Adhithya Institute of Technology. In 1904, J.J. Thomson proposed the “plum pudding model” of the atom. In this model, the electrons were simply embedded in a jelly-like structure of material that was positively charged.

Later in 1909, Thomson’s student Ernest Rutherford proposed that the electrons must be orbiting around the nucleus. According to the Bohr Model, electrons moved in a particular orbit with particular energy. “It was a starting point for quantum mechanics which finds use in concepts such as semi-conductors and super-conductivity,” says Sakthivel.

The concept of spectral lines can be explained by Bohr’s model. For example, the emissions from neon signs (it gives only particular colours and not a whole range), gas discharge lamps, fluorescent lamps, and tube lights. The gas discharge lasers were developed based on the fundamental structure of the atom.

Bohr’s model, the professors say, is a fundamental building block. It is universal in application, and forms the basis for studies in material science, engineering, and a number of inventions.

Thirty years after Bohr’s model, Einstein described it as a ‘miraculous’ achievement.

In commemoration of the 100th year, the Royal Danish Academy of Sciences in central Copenhagen organises a Science conference in its traditional meeting room at the H.C. Andersens Boulevard 35, from June 11 to 14 . It was here that Niels Bohr led the meetings (with an interruption during the Second World War), as President of the Academy from 1939 until his death in 1962