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Subrahmanyan Chandrasekhar  
 
 
 Dr Subodh Mahanti
(1910-1995)

 

Subrahmanyan Chandrasekhar, one of the greatest scientists of the 20th century became a legend in his life time. Chandrasekhar's life as Kameshwar C. Wali wrote "stands out for its singular dedication to the pursuit of science, and for practicing the precepts of science and living up to its values to the closest possible limit in one's life." His prolific contributions spanned astrophysics, physics and applied mathematics. His life is the best example of the height one can achieve provided one has the will power, skill and patience. His journey was not smooth. He had to struggle against all odds. He was a product shaped by complexities of three widely different cultures--that of India (where he was born), England and USA. He believed in common heritage of human beings. He said: "The point is the human mind works in the same way. It's reassuring that things we find pleasurable are pleasurable to other people in every part of the world. And the fact that there is a common interest emphasises that there is a common heritage." He was a great scientist, an accomplished teacher and a formidable scholar.

Subrahmanyan Chandrasekhar was born in Lahore on October 19, 1910. His father C. Subrahmanyan Iyer was in Government Service. C.V. Raman, the first Indian to get Nobel Prize in science was the younger brother of Chandrasekhar's father. Chandrasekhar grew up in Madras (now Chennai). He went to a regular school when he was eleven. He joined the Madras Presidency College in 1925 where in the first two years he studied Physics, Chemistry, English and Sanskrit. On July 31, 1930 Chardrasekhar left for England for higher studies and thus began a long and outstanding scientific career which spanned 65 years. Except for the first six years he worked at the University of Chicago.

He is best known for his celebrated discovery of Chandrasekhar Limit. He showed that there is a maximum mass which can be supported against gravity by pressure made up of electrons and atomic nuclei. The value of this limit is about 1.44 times a solar mass. This was derived by Chandrasekhar in 1930, when he was a student. The Chandrasekhar Limit plays a crucial role in understanding the stellar evolution. If the mass of a star exceeded this limit, the star would not become a white dwarf. It would continue to collapse under the extreme pressure of gravitational forces. The formulation of the Chandrasekhar Limit led to the discovery of neutron stars and black holes. It may be noted that stars are stable, that is they do not collapse because internal pressures (due to the thermal motion of the atomic nuclei and electrons and also the pressure of the radiation generated by nuclear reactions) balance gravity. However, for every star a time will come when nuclear reactions will cease and that means there will be no internal pressure to match the gravitational pull. Depending on the mass there are three possible final stages of a star - white dwarf, neutron star and black hole. Chandrasekhar was awarded (jointly with the nuclear astro_physicist W.A. Fowler) the Nobel Prize in Physics in 1983 While Chandrasekhar is best known for Chandrasekhar Limit, for him there was no limit. As mentioned earlier his work spanned physics, astrophysics and applied mathematics. In his own words: "There have been seven periods in my life. They are briefly :

1)Stellar structure, including the theory of white dwarfs (1929-39);

2) Stellar dynamics, including the theory of Brownian motions (1938-43);

3)The theory of radiative transfer, the theory of the illumination and the polarization of sunlit sky, the theories of planetary and stellar atmosphere, and the quantum theory of negative ion of hydrogen (1943-50);

4) Hydrodynamic and hydromagnetic stability (1952-61);

The equilibrium and the stability of ellipsoidal figures of equilibrium (1961-68);
The general theory of relativity and relativistic astrophysics (1962-71); and
7) The mathematical theory of black holes (1974-83)".

His research output is phenomenal and every monograph or book published by Chandrasekhar has become a classic. No serious students of the concerned fields can ignore Chandrasekhar's work. He was not motivated by a single problem but by a desire to acquire a perspective on an entire area. He was never concerned with the relative importance or unimportance of the subjects, he worked on. He was least concerned whether his work was going to bring him laurels and recognition. He said : "After the early preparatory years, my scientific work has followed a certain pattern motivated, principally, by quest after perspectives. In practice this quest has consisted in my choosing (after some trials and tribulations) a certain area which appears amenable to cultivation and compatible with my taste, abilities, and temperament. And when after some years of study, I feel that I have accumulated a sufficient body of knowledge and achieved a view of my own, I have the urge to present my point of view ab initio, in coherent account with order, form, and structure."

Once he finished a particular area he would be ready to start on a fresh one. The essence of Chandrasekhar's scientific life was `attaining a complete understanding of an area, grasping and internalising it'.

Whatever he did he did not only with a seemingly unmatched meticulousness but also with elegance. Lymnan Spitzer said: "It's a rewarding aesthetic experience to listen to Chandra's lecture and study the development of theoretical structures at his hands. The pleasure sentences and divide them into paragraphs. Do they make them short or long? For example, the idea of just using one sentence for a paragraph, or of a concluding sentence without subject or object. Just a few words .... `so it is' .... or some small phrase like that. I deliberately follow such devices ....."

Being so deeply involved in science, he had other interests as well. From the beginning he had developed interest in literature. He said: "My interest in literature began in a serious way in Cambridge around 1932. I used to devote most of the two to three weeks between terms to the study of literature. The real discovery for me at that time was the Russian authors. I read systematically, in Constance Garnett's translation, all the novels of Turgenev, Dostoevski's Crime and Punishment, Brothers Karamazov and Possessed. Chekov, I read of course all his stories and plays. Not all the Tolstoy's, but Anna Karenina certainly. Among the English writers I started reading Virgina Woolf, T.S. Eliot, Thomas Hardy, John Galsworthy, and Bernard Shaw. Henric Ibsen was also one of my favourite authors...."

Chandrasekhar had the rare ability to inspire enthusiasm for hard work in others. More than 50 students did PhD work under his guidance. His relations with his students reminds us of guru-sishya tradition of earlier times. While he evoked respect from his students, he also encouraged them to put their viewpoints without any fear. He said: "My students, students with whom I have worked closely, are respectful in a way, that is reminiscent of earlier times that we read of in books. At the same time they are not at all intimidated by what I say. They will react either positively or negatively, discuss and argue. If a person agrees with everything you say, then there is no point in the discussion."

Throughout his professional life he continued interacting with young people. Once he said: "I can easily imagine not having lost anything if I hadn't worked with Fermi or Von Neumann; but I cannot say the same thing with respect to my students".

He was the managing editor of the Astrophysical Journal from 1952 to 1971. He converted essentially a private journal of the University of Chicago into a national journal of the American Astronomical Society. For the first twelve years the Journal was managed by Chandrasekhar and a part-time secretary. "Between us we took care of all the routine work. We took care of scientific correspondence. We prepared the budget, advertisements, and page charges. We made at the reprint orders and sent out the bills." When Chandrasekhar became the Editor, the Journal had six issues in a year totalling 950 pages but towards the end of Chandrasekhar's editorship, the journal became twenty four issues totalling over 12,000 pages a year. Under his leadership the journal became financially independent of the University of Chicago. He left behind a reserve fund of US $ 500,000 for the journal.

Chandrasekhar mostly lived and worked abroad. In 1953 he became a US citizen. However, he was deeply concerned with India's well-being. He had strong association with many scientific institutions and young scientists in India. In his childhood, he was inspired by Ramanujan's example - an example of total dedication to science. His interest in Ramanujan was life long. He played an instrumental role in establishing the Ramanujan Institute of Mathematics in Madras in the late 1940s and when the Institute was facing financial crisis he took up the matter with Nehru. He also managed to get increased pension for Ramanujan's widow who was living in abject poverty. He was also responsible for the busts of Ramanujan cast by Richard Askey.

What was the motivation for Chandrasekhar in pursuing science? As one of his students Yavuz Nutku said : "Forever learning, Chandra couldn't care one bit about the establishment. Everything he did was out of being curious in a productive way. He did it for one reason and one reason only -- it would give him serenity and inner peace."

For those who are pursuing science or are planning to do we would like to end by quoting Chandrasekhar. "The pursuit of science has often been compared to the scaling of mountains, high and not so high. But who amongst us can hope, even in imagina_tion, to scale the Everest and reach its summit when the sky is blue and the air is still : and in the stillness of the air survey the entire Himalaya range in the dazzling white of snow stretching to infinity. None of us can hope for a comparable vision of nature and of the universe around us. But there is nothing mean or lowly in standing in the valley below and awaiting the sun to rise over the Kunchenjunga."

Chandrasekhar died on August 21, 1995.

Suggested reading:

1. Subrahmanyan Chandrasekhar, Kameshwar C. Wali, Current Science pp. 477-479, 1998;

2. Chandrasekhar and His Limit by G. Venkataraman, Universities Press, 1992;

3. Truth and Beauty : Aesthetics and Motivation in science by S. Chandrasekhar, University of Chicago Press, 1987;

4. Chandra : A Biography of S. Chandrasekhar by Kameshwar C. Wali, Penguin Books, 1990;

5. Eddington : The Most Distinguished Astrophysicist of His Time by S. Chandrasekhar, Cambridge University Press, 1983;

6. Resonance (a journal of science education published by the Indian Academy of Science, Bangalore) April 1997 Issue.