Comcom Magazine

An Interview with
Prof. SUBRAHMANYAN CHANDRASEKHAR

Biography
Prof. S CHANDRASEKHAR was interviewed by Dr R. Sreedher then working in All India Radio Chennai as Science officer at Chicago in October 1985 when he was turning 75.
Here are some excerpts: (courtesy Dr Sreedher, AIR, and National Public Radio)

RS: Professor Chandrasekhar! It is extremely kind of you to have spared your valuable time for All India Radio. This interview airmed at projecting your many sided personality Can you recall your earlier days in Madras and particularly your college years at Madras?

Prof Chandrasekhar: As you I left India when I finished my college and I was not twenty at that time and consequently my recollection of India is the India of 50 years ago. The fact that I remember most of those time is that the atmosphere was one in which there was enormous pride and scope for the future. That was the period when Gandhi started his salt Satyagraha. I remember Nehru visiting Madras as the President of the Indian National Congress and all the students were excited and anxious to participate in the National movement. I remember particularly the occasion when the cripps' mission visited the college in Madras. There was a boycott which everyo9ne participated. That was the national atmosphere and I was always interested in science, the scientific atmosphere prevailed even at home, in which scientific accomplishment was considered very hight. For example, in 1921, when Ramanujam died, I was only 11 years old; but my mother drew my attention to a notice in the newspaper, informing us of the death of a great Indian mathematician. The atmosphere was one in which importance was given to science and development. When I was a student in the Presidency college, Arnold Sommerfield and Heisenberg and I had a chance to share my thoughts with them. And, it was in 1928 C.V. Raman discovered 'Raman effect'. Indeed I was interested in that, and many of his students like Dr K.S. Krishnan and others were my friends. so both on the scientific side as well as on the national side, I was brought up in an atmosphere of optimism and hope.

RS: You were talking about the first Indian science laureate Sir C.V. Raman. We hear that he is your uncle. Were you close to him?

Prof Chandrasekar: No, my relationship with him was not very close. As I told you I was hardly 20 when I left India and of course he was mostly in calcutta and I was in Madras, consequently my personal relationship with him was very slender. But I do remember the discovery of the Raman effect. It was very well known; and I was able to understand it and beside I did spend two months in Calcutta in the summber of 1928 and had a chance to associate myself particularly with his students. So I would not say, that my scientific or personal relationship with Raman was close. There was no opportunity and no occasion.

RS: We know that the Nobel was awared to you for a discovery made 50 years ago on the theory of'Maximum mass of white dwarfs". I read that this discovery happended in a ship travel between Bombay and London. Can you tell us something about how it came about?

Prof chandrasekar: I referred to the visit of Sommerfield to India. During that visiti Sommerfield mentioned the discovery of new statistics associated with the names of Fermi and Dirac. He gave me a copy of his paper, where the basic physics of his new statistical mechanics had been developed. It wwas sufficiently simple for me as I read it, and then in 1929 I came across the paper by Harvich Fowler in which he had applied this new statistics to elucidate the properties of 'white dwarfs'and in particular why they had the high mean desnisty like a million grammes per cubic centimetre. He essentially accounted for that. I knew, therefore, the application of the statistical mechanics to white dwarfs through Fowlere's method, and I had learnt about the statistical mechanics itself from Sommerfield. During my voyage to England in the summer of 1930, I asked myself the question as to how fast the electrons in the centres of white dwarfs would be moving. It is a fairly simple calculation and I could work it out because I had leant internal constitution of the stars. And when I made the calculation I found that the electrons in the centre of white dwarfs were moving with a velocity close to half the velocity of light. So the question arose that if the velocity was that high, the usual formulae which Fowler had used had to be modified to take into account this new effect. and when I took it into account and asked what other astrophysical implications were there, the answer came right out- that white dwarfs cannot exist when the mass exceeded a certain value. So it is a very simple remark and the state of science was that it was accessible to one with a limited knowledge whichi I then had at that time.

RS: We are also aware that you consider your latest findings equally or more important. It is amazing that you were able to shift your interest in record time and master these new fields. Martin Shwartz, your longtime friend, says that every field of your research needs a life time for others. Can you comment on this?

Prof Chandrasekar: First of all I don't think that it is is correct to say I consider my later work important. In fact, in the choice of my work, in the choice of the problems, 'importance' is a factor. I am concerned or at least mostly have been concerned with trying to undrstand a larger area, so that the only thing I can say is that my later work has involved as much concentration, as much effor, as my earlier work. In some ways, my lat work which occupied about 12 years - 1970-1984, was devoted to the mathematical theory of the 'Black Holes' and I consider that the effort, I put in and the problems i elucidate were more difficultu, at least more difficult for me, than any other project. So it is not correct to say that I consider them important. But they constitute an effort of the same nature as my earlier work.

Now the reason for my changing different areas is that after I work in an area for sometime, but perhaps I want to say, that the choice of my subjects for study, particularly after 1940, was based upon whether the areas was one which was amenable to the kind of study which I was capable of , the kind of exploration which I could make and if I found that after some trial that there was an area in which a large amount of work could be done in a consistent satisfactory way suitable to my taste and my temperament, then I pusue that, and normally in about 8 - 10 years I did arrive at a stage when I fel that the area is one whihc is capable of being put into satisfatory form, a form which reflects my own personal view. And, once I have taken the affort and the time to write such a book in which I summarise and indeed quite often re-do a large part of my earlier work in a coherent form which makes a pattenr and gives me a sense of architectural unity, then I feel that it no longer is useful for me to continue in that line. I don't want to exaggerate my particular value to tha particular kind of effort but that is my way of looking at it. I change from area to area and normally it has taken 8 - 10 years to arrive at such a point.

RS: What is your present field of interest?

Prof Chandrasekar: Well that is much more difficult question to answer. I, finished my book ' Mathematical Tehory of Black Holes' just about two years ago (1983) and from past experience, the kind of areas which interest me are those which take a very long time like - 10-12 years. I rather feel that it would be rather foolish of me to try to embark in a corresponding effort at my present age. I will be 75 in a few days. Consequently I do not know if I shall the time or the energy to embark on any new area. However, during the past two years, by certain accidental circumstances, I got interested in the area of the 'collision of gravitational waves'-the scattering by gravitation. This happens to be ab are, the knowledge about which I have acquired in the study of black holes can be as a result extended and worked out. That is a particular area I am now working in. But I am not really sure to what extent I want to go as extensively in this area as I have done in the past in other areas.