The period 1920 - 1930 may truly be hailed as the 'golden era' of physics in India, for it was during that decade that four important discoveries were made in the field. These were Bose statistics, the Raman effect, the Chandrasekhar limit and the Saha ionisation formula. It is this latter discovery, and its discoverer, that are the subject of this Entry.
Meghnad Saha was an Indian astrophysicist who was nominated for the Nobel Prize in Physics in 1935 - 36. He was a fellow of London's Royal Society, founded the Saha Institute of Nuclear Physics in West Bengal, India and was Member of the Indian Parliament 1951 - 1956. His initial work was in thermodynamics, though he later changed his field to astrophysics and became famed for the Saha Equation.
The Beginnings of Greatness
Meghnad Saha was born on 6 October, 1893, the fifth child of Jagannath Saha and Bhubaneswari Debi. Jagannath Saha was a shopkeeper in the village of Seoratali, 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, particularly in mathematics and history, that his teachers wanted him to attend an English secondary school. The nearest such school was in another village about ten kilometres (seven miles) away. He was lucky in that one Dr Anantha Kumar Das took an interest in him and offered free board and lodging (providing the boy did his washing and attended to minor chores around the house), so the young Meghnad could go to school. Later in life, he took every opportunity to express his gratitude to Anantha Kumar Das for this timely help at such a crucial stage, without which his education may never have continued.
In 1905, Meghnad Saha went to Dhaka and joined the Government Collegiate School where he received a free scholarship. It was during this period that the British partitioned Bengal, much against the will of the people. Naturally, there were protests everywhere and when Fuller came on a visit to Dhaka, a boycott was organised. Along with other students, Saha joined in the agitation. As a result, he was suspended from the school and his scholarship terminated. He was later admitted to Kishorilal Jubilee School, where he again received a free scholarship.
In 1911, Saha travelled to Calcutta and joined the Presidency College to study for a BSc in Applied Mathematics. Once again, he was dependent on a free scholarship. Noted Indian scientists SN Bose and PC Mahalanobis also attended this college, along with the freedom fighter Subhas Chandra Bose1. After the BSc came the MSc, and SN Bose was Saha's classmate. In both his degrees, Bose secured the top mark, while Saha came second.
From 1913 to 1915, while studying in Presidency College, Saha grew to know Bagha Jatin. So called because he had killed a tiger (bagha) single-handedly with a dagger while gun-running in the jungles of Sunderbans, Jatin was a famous freedom fighter who used to visit Saha's hostel. Although Saha was emotionally sympathetic to the cause of freedom, he did not become involved with the revolutionary activities.
After college, Saha applied to take the Financial Civil Service (FCS) examination and enter the FCS, but was denied permission as he was suspected of contacts with revolutionaries. 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.
In 1919, the American Astrophysical Journal published On Selective Radiation Pressure And Its Application, a research paper by Saha. Slowly his expertise became astrophysics and soon Saha Ions Theory was published. By 1920, Saha had established himself as one of the leading scientists in physics and was awarded the DSc degree by Calcutta University in 1918. In between, Saha married and then went to Europe for two years. He spent time conducting research at Imperial College, London and at a laboratory in Germany.
Upon Saha's return to India, 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, they were transferred to the Physics Department (where Raman had been appointed Palit Professor).
There was pressure from Indian students to include new sections in the higher studies curriculum for science subjects. Most of the new developments in physics were taking place in European countries like Germany. Saha'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 by Einstein and Minkowski into English versions. Later on, these translations were published by Calcutta University.
In 1927, Saha was elected a Fellow of London's Royal Society. He wanted to set up a modern research laboratory in Calcutta University, but was not successful in this venture. He moved to Allahabad University and in 1932, Uttar Pradesh Academy of Science was established. The Academy turned out distinguished students such as DS Kothari and RC Majumdar, who went on to establish the Physics Department in Delhi University. It was his work in this field that later saw Saha nominated for the Nobel Prize in Physics.
Scientists are often accused of living in the 'Ivory Tower' and not troubling their mind with realities and apart from my association with political movements in my juvenile years, I had lived in my Ivory Tower up to 1930. But science and technology are as important for administration nowadays as law and order. I have gradually glided into politics because I wanted to be of some use to the country in my own humble way. - Meghnad Saha
In 1947, Saha established the Institute of Nuclear Physics, which was later renamed the Saha Institute of Nuclear Physics in his honour. He took the first steps to include Nuclear Physics in the curriculum of higher studies of science; and, for the sake of the development of science in India, he went into politics. In 1952, he was elected as a Member of Parliament for the North-West Calcutta consituency. He was an advocate for the peaceful use of nuclear energy and instrumental in the reformation of the Indian calendar.
The Work of an Empassioned Man
Meghnad Saha's basic work was on the thermal ionisation of elements. When an element is heated to a very high temperature, the electrons in its atom receive enough energy to break free. This is thermal ionisation. Saha discovered that, by studying the spectra of various stars, their temperature can be measured. This led him to a formula that he called the 'equation of the reaction-isobar for ionisation', which later became known as Saha's 'Thermo-ionisation Equation'.
The Ionisation State
The ionisation state is basically the electronic connotation of what goes on in a chemical reaction, the very basics of the chemical process by which an electron is removed from an atom, a molecule, or an ion. It is of basic importance to electrical conduction in gases and liquids; and, in the simplest case, ionisation may be thought of as a transition between an initial state consisting of a neutral atom and a final state consisting of a positive ion and a free electron. In more complicated cases, a molecule may be converted to a heavy positive ion and a heavy negative ion which are separated. Using the Saha Equation, you are able to determine the ionisation state of the various elements in a star.
A Varied Legacy
Saha went on to invent an instrument to measure the weight and pressure of solar rays, and was also associated with the building of several scientific institutions like the Physics Department in Allahabad University and the Institute of Nuclear Physics in Calcutta. He was also the leading light behind organising 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). He was also the founder and editor of the journal Science and Culture.
As a Member of Parliament, Saha was the chief architect of river planning for India during the early 1950s and prepared the original plan for the Damodar Valley Project. The valley had a history of seasonal flooding and was in a seismic zone. Saha proposed the building of a series of dams instead of a single one. The Damodar Valley Project continues to function, and is a testimony to Saha’s engineering acumen.
On 16 February, 1956, Saha died suddenly of a heart attack at the Saha Institute of Nuclear Physics. Dr Kothari recalls of him:
He was extremely simple, almost austere, in his habits and personal needs. Outwardly, he sometimes gave an impression of being remote, matter of fact, and even harsh, but once the outer shell was broken, one invariably found in him a person of extreme warmth, deep humanity, sympathy and understanding; and though almost altogether unmindful of his own personal comforts, he was extremely solicitous in the case of others. It was not in his nature to placate others. He was a man of undaunted spirit, resolute determination, untiring energy and dedication.
1 No relation to SN Bose.