Meghnad Saha was born 125 years ago in an obscure village in East Bengal, now Bangladesh, in a family where his father was an indigent shopkeeper. The country was under British rule, and society was sharply divided by a rigid caste structure, destructive poverty and extreme superstition. Young Meghnad had to fight against inconceivable odds to free himself from these disadvantages, but rose to the highest level of scientific endeavour by dint of hard work and a gift to “record fearlessly which I have carried out…by my own hand.” Above all, he was armed with an indomitable passion for his country.
Bengal was basking at that time in the glorious social movement of Renaissance, with success in all kinds of intellectual pursuits; literature, art, science and history. Meghnad Saha was impressed and inspired by the vibrant spirit of the contemporary ambience. He joined Presidency College and became a member of an enlightened group, with Satyendra Nath Bose and Prasanta Chandra Mahalanobis.
Acharya Jagadish Chandra Bose was their teacher and Acharya P.C. Roy was about to bring in the spirit of entrepreneurship, the first time in India by an Indian. There was an element of enormous expectation, with the dream that they would show the world that they were as good as anyone, despite colonisation and the absence of any worthwhile facilities.
At 24, Meghnad was appointed lecturer at Calcutta University in 1917. Sir Ashutosh Mukherjee, then Vice-Chancellor, was picking up the best available to teach science, breaking rules effortlessly. Physical sciences were going through a revolution, especially in Europe; the traditional foundation of Galileo and Newton had been shaken by Albert Einstein with his special theory of relativity leading to a radically different understanding of space and time, which became an intrinsic part of our understanding of nature, unlike the Newtonian concept of them being there but with no real role. The traditional notion that energy carried by electromagnetic waves in a cavity followed Maxwell’s equation and thus could take any value in the continuum, failed to account for the observed characteristic of blackbody radiation.
Max Planck for the first time introduced the radical idea of energy quantisation and explained black-body radiation. The classical view was also breaking apart in the microscopic scale, and Niels Bohr in 1913 went ahead and introduced the rather ad hoc quantisation hypothesis.
The youthful Meghnad embraced the turmoil at the heart of contemporary physics with enthusiasm. The first problem he dealt with was with the question of radiation pressure on matter. With S. Chakravarti, he published in the Journal of the Asiatic Society (New Series 14 (1918) 425) the paper “On the Pressure of Light”, believing strongly in Hamilton’s proposition that “theory and experimental investigation are the two eyes of physics and research works flourish best where workers see with both eyes.”
With eyes firmly on the measurement of radiation pressure, he and Chakravarti set up a tungsten filament lamp with vanes made out of reflecting films covered by glass plates and proceeded to measure the pressure. The experiment yielded only qualitative results but the exercise gave Saha the confidence to press forward. He quickly moved to “On Radiation Pressure and the Quantum Theory ~ A Preliminary Note” (Astrophysical Journal 50 (1919) 220) that confronted the question of radiation exerting pressure on atoms and molecules, asserting that selective radiation pressure should present the problem of the equilibrium of solar atmosphere in a new light.
In general terms, before arriving at his famous Ionisation Equation, he took note of (a) the quantum model of Bohr and the consequent spectroscopy of atoms; (b) thermodynamics and more important chemical rate processes; (c) the techniques of equilibrium and non-equilibrium statistical mechanics, ~ in short, a comprehensive and elegant consequence of interdisciplinary research, long before interdisciplinary research became fashionable, even as a buzz word. Thus Saha was well equipped, in the understanding of the relevant branches of physics which culminated in the ionisation formula which bears his name.
The reaction to Saha’s ionization equation was electric in India and abroad. His friend Satyendra Nath Bose remarked, “Do you know what Meghnad did? Sitting at home, he measured the temperature of stars. The pearls were in a sense already there but it required a Meghnad to recognise them and to string them together into a necklace of unsurpassable beauty” ~ the pearls being the disciplines of an interdisciplinary adventure.
Rabindranath Tagore went one step further; “It is expected that ninety-two elements that have been found on earth must have had their traces in the Sun too. Only thirty-six of them have been discovered. Saha solved the puzzle of the missing elements in the Sun”. (Viswaparichai, published in 1937 byTagore). People who argue that Tagore was only one of the greatest poets, with no aptitude for science, should readViswaparichai.
The Saha equation has been used successfully in two very different areas in recent times. A.P.J. Abdul Kalam and his colleagues used it for the understanding of the trajectory of the rocket, while I and Pijushpani Bhattacharya (Phys. Rev D48. 4630 (1993)) and others have used it for the understanding of the survivability of cosmological quark nuggets in the very early universe.
Meghnad Saha was not content only with his ionisation formula, but took interest in nuclear physics as well as particle physics, then just emerging in the 1930s and 1940s. When I took over as director of the Saha Institute in 1992 it was puzzling that astrophysics, introduced to the world by Meghnad Saha, was nowhere on the scene; it took ten years to convince others that a Centre for Astroparticle Physics should be established. Saha, while establishing the Institute of Nuclear Physics at Calcutta University, concentrated mostly on nuclear physics, an emerging field at that time.
Why he abandoned astrophysics, his brain child and for which he is recognized the world over, but plunged into nuclear physics, is a mystery. Saha’s commitment was so intense that he sent his student B. D. Nagchowdhury to Lawrence Laboratory at Berkeley to digest the complicated technology of the cyclotron. Unfortunately, with the Second World War, the vacuum pump, radio frequency equipment and other components arranged by Nagchowdhury were drowned in the Atlantic.
Long after Meghnad Saha’s untimely death, that dream of a cyclotron to be used by nuclear physicists at the Saha Institute was fulfilled by Raja Ramanna. A room-temperature cyclotron was built in Calcutta almost indigenously in the model of Texas A&M and installed in the area adjacent to where the Saha Institute of Nuclear Physics is situated at Salt Lake. That cyclotron, built in the late 1970s, is still operational. Saha’s dream turned to reality after almost forty years.
The scientists involved were Ajay Divatia, Santimay Chatterjee and N.K. Ganguly of the cyclotron centre with other young engineers under the leadership of Ramanna and H. J. Bhabha as Chairman, Atomic Energy Commission. Some high quality work has been done using the cyclotron but had it been operational twenty years before, it would have been more effective. Yet it was no mean feat ~ Calcutta was then in the thick of violent political agitation, and there was acute power shortage.
Meghnad Saha was drawn to politics and became a Member of Parliament as an independent backed by the Left. He was deeply involved in planning, and was in touch with Subhas Chandra Bose. Saha differed from the Indian National Congress policy towards planning and was more inclined to the liberal left than the conservative liberalism of the Congress. Having spent his early life in East Bengal, Saha was familiar with the significance of rivers for power generation and became keenly interested in scientific methods to avoid floods.
While involved in national planning he realised that there had been virtually no study on rivers in India, and that floods were caused by human interference with river flows, causing undue pressure on water bodies. Damodar Valley Corporation was his brain-child and planning for river resources was partly successful. Unfortunately, coal mine owners in Bengal feared financial loss if power was generated from rivers, and DVC could not achieve the success Saha hoped for. This is the story of many good projects in India, when project reports are prepared but never see the light of day.
Curiously enough, Saha also took a keen interest in calendar reform. It is sad that such an illustrious life came to an end at an age 63 on the steps of the Planning Commission in Delhi on 16 February 1956. In the words of parliamentarian Hirendra Nath Mukerjee, it is worth recalling an event in Parliament.
“Exasperated by a speech made by Dr Saha, Prime Minister Nehru, who normally behaved gently, burst out saying that Saha should not have been involved in worthless affairs instead of engaging in scientific activities.” Saha retorted, “Scientific persons like Meghnad Saha would be remembered long after the politicians reigning today are totally forgotten.” Such was the confidence of the angry young man, who was not so young by then.
I conclude with the words that epitomize the essence of Saha’s creativity Ad astra per asperaet per ludum. To the stars through hard work and fun!
The writer is INSA Honorary Scientist, former Homi Bhabha Professor of DAE, Variable Energy Cyclotron Centre.