M N Saha in Historical Perspective

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This unusual collection of readings on the life and work of Meghnad Saha (1893-1956), the outstanding Indian astrophysicist best known for his seminal theories of thermal ionization and selective radiation pressure, brings together a selection of memorial pieces, rarely accessible early responses to his work by major contemporaries like Jeans, Erdington, Russell, Mitchell, and Harlow Shapley, a more recent scholarly documentation of his work and its repercussions, and evaluations by younger Indian Scientists. They add up to offer an image of Saha as man, scientist and politician-and humanist-against the setting of the complex historic experience of colonial India moving towards independence and development. Saha’s role in the process comes in for critical assessment, as the rich global implications mingle with the more immediately national. Aimed at both the specialist reader and the more general one, the book should serve as a fairly comprehensive account of the achievements of Saha, and what they mean to science today.

Jyotirmoy Gupta, veteran journalist and science correspondent, has recently edited (jointly with Santimay Chatterjee) M.N. Saha in Parliament for the Asiatic Society, Calcutta.

The recent surge of popular interest in the fundamental sciences, particularly in fundamental physics, has been one of the more unusual and significant developments of our time. People have been wondering as to why physics, with its abstruse, almost impenetrable formulae and esoteric technical jargon, should suddenly draw such attention in the western world. Several scholars in the West would credit it to the immense power of physics to explain aspects of the mysterious universe considered inexplicable for too long. Among the natural sciences, physics alone can claim to be an all-encompassing discipline, with the whole universe for its subject. It is only through physics, or rather 'the new physics' that all aspects of the cosmos, ranging from the elementary particles within the atoms to the largest astronomical structures, can be perceived within a single conceptual framework.

In other words, modern physics has disclosed the existence of a whole new world of which man had no inkling before - the. world of quanta, elementary and 'strange particles', electronic clouds, atomic nuclei, electromagnetic waves, and the relativity laws of superhuman speeds and dimensions - that has emerged as the real world, and the world we knew earlier is now but a flickering shadow.

One wonders if the popular interest in fundamental physics is already a sign at last of a trend that should eventually bridge the gulf between the two polar groups- the scientists and the humanists. The global trend has affected India too, where there has been a steady growth in science publishing in the Indian languages, and media exposure of scientific ideas and information at several levels.

The schism in the intellectual community between scientists and humanists has been a subject of serious concern in this century. The man who first underscored the polarization of these two groups of enlightened human beings, and read it as the phenomenon of the 'Two Cultures' in his Rede Lecture at Cambridge in 1959 was Charles Percy Snow, better known to his readers as C P Snow, the British novelist and physicist. But the divide and tension can be traced back to the ancient Egyptians and Greeks. The conflict has been steadily heated for the past four or five centuries, with Copernicus, Galileo, Kepler and Newton and their successors serving to fire it up. Science historian I Bernard Cohen pointed out that authors in the eras dominated by the stalwarts 'apparently made science understandable to the reading public.' In this connection, he could cite the instances of authors like Fontanelle, Voltaire, Euler, and others. 'These writers were perhaps successful because then only well-educated people could read them and moreover science was not complex.'

But the 'cultural divide' became wider in the last century as a consequence of the theories of Charles Darwin and Thomas Huxley and the later discoveries in the new physics of quantum mechanics and relativity. From the Victorian days onwards, Henry Adams, Alfred Whitehead, George Sarton, James Jeans, AS Eddington, C P Snow and several other thinkers have almost interminably warned their readers against the dangers of a fractured culture. Before C P Snow in the 1959 Rede Lecture referred pointedly to the serious danger inherent in the widening gap between the two cultures, George Sarton, the celebrated science historian, had also made the same point in 1930. 'The most ominous conflict of our time,' Sarton observed, 'is the difference of opinion, or outlook, between men of letters, historians, philosophers, the so-called humanists on the one side and scientists on the other.' Whatever both Sarton and Snow said in this regard, they said from their personal experiences and no one could deny the strength of their evidence. This relationship of conflict between the two cultures is, according to both of them, 'fatal to both science and society.' C P Snow felt further that with their preoccupation with the study of the mystery of the universe and their endeavour to control the forces of nature, the scientists are likely to take a more rational view-of men and things. Although Snow maintained that there were two cultures that had drifted apart, his several critics felt that there was a much closer affinity between the arts and science than he claimed. 'It might not be long before only a single culture remains; or that there is a third culture- man in society.'

The gulf ominously widening between the scientists and humanists in India shows signs of healing with the growing public interest in the fundamental sciences. There is little scope here to document in detail the growth of such interest in India.

Against this background, it is certainly worthwhile to project in a proper perspective the scientific contributions of Meghnad Saha, on the occasion of his birth centenary this year, for the benefit of readers at home anti abroad. Saha's scientific contributions, particularly in astrophysics, led to a new era in astronomy, and he has been de- scribed as the father of modern astrophysics.

The first astrophysical work of any importance in India is credited to the French astronomer, Jansen, who in 1868, observed a total solar eclipse of the sun passing over Guntur (now in Andhra Pradesh) and applied the spectroscope to the Sun during the moments of totality; and found a line close to and on the violet side of the yellow line of sodium. This line was also observed independently by Norman Lockyer who christened it 'helium'. It is now a matter of common knowledge that helium was discovered thirty years later (1898) by Ramsay in the Norwegian' mineral Clevite (cf. The Progress of Science in India during the past Twenty-Five Years, published by the Indian Science Congress Association in 1938).

The total solar eclipse of 1868 which passed over Buxer and what was then the Western Presidency was observed by Lockyer, Evershed and Naegamvela. Photographs of the flash spectra were obtained by all the three observers. Evershed, who succeeded to the Directorship of the Kodai- kanal Laboratory in 1911, instituted a programme for the photography of prominences and systematic investigation of the spectra of sunspots and their penumbra. These observations led to his discovery of radial motion in sun- spots; and simultaneously with Alfred Fowler, G E Hale, SA Mitchell and W S Adams, he drew the inference that the spectra of spots were similar to those of the k-class of stars. C Nagaraja Aiyar in 1907 at Kodaikanal obtained a. reversal of the D-Iine of helium in the penumbra of spots. Evershed proved that all spark lines are weakened in the spot, a fact which was later explained with the help of Meghnad Saha's theory of thermal ionization formulated in the 1920s. The tradition so happily created by Evershed at Kodaikanal was continued by his successors, T Royds and A L Narayan.

Saha appeared on the Indian science scene In 1917 with his first paper - 'On Maxwell's Stresses' (Phil. Mag. Sr. VI, 3,256,1917). This was the first paper from India in modern theoretical physics in this century. But his researches in astrophysics date from 1919; and within a span of two years his works would lead to a new era in modern astrophysics. The stimulus for his researches in astrophysics came from a study of Miss Agnes Clerke's popular books on astronomy.