The period 1920-1930 may truly be hailed as the golden era of physics in India, for during that decade were made four important discoveries namely, the Saha ionisation formula, Bose statistics, the Raman effect and the Chandrashekar limit. This review is about the first of the four discoveries and the man who made it.
Meghnad Saha (October 6, 1893 – February 16, 1956) was an Indian astrophysicist from Bengal. He was nominated for the Nobel Prize in Physics(1935-36), was a fellow of London's Royal Society, founded the Saha Institute of Nuclear Physics (West Bengal, India) and was Member of Parliament from 1951 to 1956. His initial work was in Thermodynamics, though he later changed his field to Astrophysics.
Meghnad Saha was born on the 6th of October, 1893, the fifth child of Jagannath Saha and Bhubaneswari Debi. Jagannath Saha was a shopkeeper in a village named Shaoratoli near Dhaka in Bangladesh. The Sahas were not rich and barely managed to make ends meet. Young Meghnad was admitted to the primary school of the village where he did so well that his teachers wanted him to attend an English-medium school. The nearest such school was in another village about 10km away.
He was lucky in that one Mr.Anantha Kumar Das, a medical practioner, took interest in Meghnad and offered him free boarding and lodging. Later in life, Saha never failed(whenever the occasion arose) to express his gratitude to Anantha Kumar Das for the timely help at a crucial stage, but for which his education may have been terminated.
In 1905, Meghnad went to Dacca and joined the Government Collegiate School and received a free studentship and also a stipend. This was the period the British partioned Bengal, much against the will of the people. Naturally there were protests everywhere and when Fuller came on a visit to Dacca, a boycott was organised. Along with other students Meghnad also joined in the agitation and as a result was suspended from the school and his scholarship was terminated. He got admitted to Kishorilal Jubilee School, where again he received a free studentship and a stipend.
In 1911 Saha came to Calcutta and joined the Presidency College to study for the B.Sc. degree in Applied Mathematics. Once again he was dependant on a stipend plus free studentship. Noted scientist S.N. Bose was his classmate and Mahalanobis was one year senior. The great freedom fighter Subhas Chandra Bose was Saha's junior by one year. His teachers included Sir J.C. Bose and P.C. Ray. After B.Sc. came M.Sc. and once again S.N. Bose was his classmate. Both in B.Sc. and M.Sc., Bose secured the first rank while Saha stood second.
During 1913 through 1915, while studying in Presidency College, Meghnad got involved with Anushilan Samiti to take part in the freedom fighting movement. Bagha Jatin, so called because he had killed a tiger(bagha) single handedly with a dagger, while gun running in the jungles of Sunderbans, was a famous freedom fighter. Jatin used to visit Saha's hostel for building a student organization. Although Meghnad was emotionally sympathetic to the cause of freedom, he did not become involved with revolutionary activities. His goal was to get a job, earn money and support his family.
After college he tried to appear for the Financial Civil Service(FCS) examination and enter the FCS but was denied permission as he was suspected of contacts with revolutionaries, besides having participated in the boycott as a school student. Not being able to join Government service was a big blow to Saha but as it turned out, it was a great boon for science. Meanwhile a living had to be eked out and Saha did this by going up and down Calcutta on a bicycle giving private tuition.
It was around this time that Sir Ashutosh Mukherjee became the Vice Chancellor of Calcutta University and offered lecturerships to both Saha and Bose in the Department of Mathematics but because they could not get along with Dr. Ganesh Prasad, the professor, he transferred them to the Physics Department where Raman had been appointed Palit Professor.
There was pressure from students for including new sections in higher studies curriculum in science subjects. Most of the new developments in Physics were taking place in European countries like Germany. Meghnad's duty was to teach Quantum Mechanics. The knowledge of German picked up earlier came in handy and within a few days of starting to teach, Saha and Bose translated papers on relativity published in German by Einstein and Minkowski into English versions. Later on this was published as a book from Calcutta University.
In 1919 American Astrophysical Journal published - "On Selective Radiation Pressure And its Application" - a research paper by Meghnad. Slowly his expertise became astrophysics. And "Saha Ions Theory" was published. By 1920, Meghnad Saha established himself as one of the leading scientists in physics and was awarded the D.Sc. degree by Calcutta University in 1918. In between Saha got married and then went to Europe and stayed for two years. He spent time in research at Imperial College, London and at a research laboratory in Germany.
In 1927, Meghnad was elected as a fellow of London's Royal Society. He wanted to set up a modern research laboratory in Calcutta University, but was not very successful in this venture. He moved to Allahabad University and in 1932 Uttar Pradesh Academy of Science was established which turned out such students as D.S. Kothari and R.C. Majumdar, who went on to establish the Physics Department in Delhi University. He returned to Science College, Calcutta in 1938 for the last and final time. During this time Saha got attracted to Nuclear Physics and was nominated for the Nobel Prize in Physics for his work in this field (1935-36).
In 1947, he established the Institute of Nuclear Physics which later was named after him as Saha Institute of Nuclear Physics. He took the first steps to include Nuclear Physics in the curriculum of higher studies of science. For the sake of development of science he joined politics and in 1951 was elected as a Member of the Parliament.
He invented an instrument to measure the weight and pressure of solar rays. He produced the famous equation which he called 'equation of the reaction - isobar for ionization' which later became known as Saha's "Thermo-Ionization Equation", or the Saha Equation. According to the Scientific American, this equation became the foundation for the field of astrophysics.
Meghnad Saha's basic work was on the thermal ionisation of elements and it led him to formulate what is known as the Saha equation (When an element is heated to a very high temperature, the electrons in its atom get enough energy to break free from the atom. This process is known as thermal ionisation). Saha's equation is one of the basic tools for interpretation of the spectra of stars in astrophysics. By studying the spectra of various stars, one can find their temperature and from that, using Saha's equation, determine the ionisation state of the various elements in the star.
He was also associated with building several scientific institutions like the Physics Department in Allahabad University and the Institute of Nuclear Physics in Calcutta. He founded the journal "Science and Culture" and was the editor till his death.
Saha was the leading spirit in organizing scientific societies like the 'National Academy of Science' (1930), the 'Indian Physical Society' (1934), 'Indian Institute of Science' (1935) and the 'Indian Association for the Cultivation of Science' (1944). The lasting memorial to him is the Saha Institute of Nuclear Physics founded in 1943 in Kolkata.
As a Member of Parliament of independent India, he was also the chief architect of river planning. He prepared the original plan for the Damodar Valley Project which had a history of seasonal flooding and was in the seismic zone. Saha proposed to build a series of dams instead of a single dam. The Damodar Valley Project continues to function till date and is a testimony to Dr. Saha’s engineering acumen. This great and versatile scientist died in 1956.