Meghnad Saha was born on 6th October,1983 to Jagannath Saha and Bhubaneswari Devi. With much of childhood spent in poverty and in want of basic necessities it was through the combined efforts of his elder brother and local doctor that Saha was able to complete his primary education with flying colours and secure himself a small scholarship continuing his education. With a passing grade on the Intermediate Examination of the Calcutta University in 1911, Saha joined the Presidency College at Kolkata. Among his classmates was Satyendra Nath Bose, Prasanta Chandra Mohalanobis, the founder of the Indian Statistical Institute, was his senior by a year. His tutors included Prafulla Chandra Ray in Chemistry and Jagadis Chandra Bose in Physics. Saha passed both his BSc (Applied Mathematics) and MSc (Mathematics) exams with honours in 1913 and1915, respectively. Saha stood second in order of merit in both the examinations. S.N Bose took the top spot in both situations.
Saha on the now famous 'Saha Equation': “It was while pondering over the problems of astrophysics, and teaching thermodynamics and spectroscopy to the MSc classes that the theory of thermal ionization took a definite shape in my mind in 1919. I was a regular reader of German Journals, which had just started coming after four years of first world war, and in course of these studies, I came across a paper by J.Eggert in the Physikalische zeitschrifts (p.573) Dec. 1919, “ Uber den Dissociationzustand der Fixterngase” in which he applied Nernst’s Heat Theorem to explain the high ionization in stars due to high temperatures, postulated by Eddington in course of his studies on stellar structure.
Eggert, who was a pupil of Nernst and was at the time his assistant, had given a formula for thermal ionization, but it is rather strange that he missed the significance of ionization potential of atoms. Importance of which was apparent from the theoretical work of Bohr, and practical work of Franck and Hertz which was attracting a good deal of attention in those days…Eggert used Sackur’s formula of the chemical constant for calculating that of the electron, but in trying to account for multiple ionization of iron atoms in the interior of stars on this basis, he used very artificial values of ionization potential.While reading Eggert’s paper I saw at once the importance of introducing the value of ionization potential in the formula of Eggert, for calculating accurately the ionization, single or multiple, of any particular element under any combination of temperature and pressure. I thus arrived at the formula which now goes by my name. Owing to my previous acquaintance with chromospheric and stellar problems, I could at once see its application. I prepared in the course of six months of 1919 (February to September) four papers(“Ionisation of the Solar Chromosphere” (March 04, 1920), “On the Harvard Classification of Stars” (May 1920), “On Elements in the Sun” (22 May 1920) and “On the Problems of Temperature-Radiation of Gases” (25 May 1920)) and communicated them for publication in the Philosophical Magazine from India within August to September.”
Cecilia H. Payne undertook the detailed task of checking Saha's ionization theory and its developments against observation, when she joined Harvard Observatory as a Fellow in 1923. In her own words “In my last year at Cambridge, I had come to know E. A. Milne who (with Ralph Fowler) had just published the historic paper on stellar atmospheres. They in turn had been inspired by the brilliant idea with which Meghnad Saha had applied the principles of physical chemistry to the ionization of stellar material, the idea that gave birth to modern astrophysics. Before I left Cambridge, Milne told me that if he had my opportunity, he would go after the observations that would test and verify Saha's theory. When I told Dr Shapley that this was what I should like to do, he promptly opened up to me the riches of the Harvard plate collection". She published these results in her book Stellar Atmospheres, which was submitted as her PhD thesis to Radcliffe College and published for the Harvard College Observatory in 1925. It has been called 'undoubtedly the most brilliant PhD thesis ever written in astronomy'¹º
Saha excelled at creating institutions. The Radio Physics, Electronics, and Applied Physics departments at Calcutta University were significantly influenced by Saha, who also founded the Institute of Nuclear Physics in 1950. Dr. Shyama Prasad Mookherjee, who was India's Minister of Civil Supplies at the time, lay the Institute's foundation stone. The institute was first located on the campus of Calcutta University and was formally launched by Irene Joliot-Curie on January 11, 1950.
It was Saha, who first introduced nuclear physics in the MSc physics syllabus of the Calcutta University in 1940. He also started a post-MSc course in nuclear science for the country. He initiated steps for building a cyclotron, the first of its kind in the country. His ionization equation continues to play a pivotal role in many areas of modern physics.