S. Chandrasekhar - As I Knew Him

A.N. Maheshwari

A tribute to Professor Subrahmanyan Chandrasekhar, Astrophysicist

Born October 19, 1910; Died August 21, 1995

My association with Professor Chandrasekhar dates back to 1964 when I reached the University of Chicago to do my Ph.D. studies in physics. I saw an Indian looking Professor dressed in a black suit wearing a Cambridge University tie. He was sitting in the first row of a physics colloquium and I could easily connect that the distinguished person was Professor Chandrasekhar, whom everybody affectionately called Chandra. He appeared to me then both very reserved and unapproachable. I changed this opinion as I began to know him more closely. My next encounter with Chandra was at a Phi-Club meeting, which were specially arranged by the Department of Physics of the University to provide to the fresh class of graduate students face-to-face interaction with the senior faculty of the University. Professor Chandrasekhar spoke on General Theory of Relativity and its relevance to Cosmology & Astrophysics. I do not think I followed the lecture, but can distinctly recall the remark made by Chandra, "Veracity of the Einstein's theory of Gravitation is as undisputable as are the findings of Justice Warren on the assassination of President John F. Kennedy". I left the meeting with more awe and a feeling of a vast distance between his intellectual abilities and what I possessed as a twenty-one year old graduate student.

I was thrilled to see the announcement that Professor Chandrasekhar would teach a course on Non-relativistic quantum mechanics. I had studied this course as a part of M. Sc. studies in physics at the University of Delhi. I signed up for that course perhaps thinking that I should be able to impress the Professor with my background and the head start I thought I had. In the first lecture when the Professor entered the class he demanded that no smoking be observed, as he was allergic to tobacco smoke. This was obeyed by the class, but Chandra's reasons were suspect as he could be seen sitting between Professor Mark Ingraham and Professor Gregor Wentzel, both of whom puffed away cigar smoke continuously and within their vicinity the pollution level could only be matched by what comes out of coal-fed boilers in Chicago City. Chandra spoke Cambridge-English without a trace of American accent and wrote on blackboard as though he was doing calligraphy. He did not like being disturbed during his lecture and looked reprovingly at students drinking coffee or eating sandwiches. The course was uneventful as it progressed but a jolt was experienced by the entire class when he announced at the end of the eleventh week that the examination would be of six hours duration with an optimum response time of about four hours. He further elaborated that there would be only one problem to be solved in closed-book/closed-notes setting and that rough-calculation sheets were to be appended to the answer-script. He also advised students to bring their pack lunch to the examination hall! The problem to be solved turned out to be on finding analytically changes in energy levels of hydrogen atom in strong electric field by setting up the Hamiltonian and writing the Schrodinger equation. Hints were given for various stages of solution that could be reached after about each successive hour of work. I vaguely recall that I could not proceed further beyond the fourth hour and closed my test after eating sandwiches, which I had specially prepared and rounded up my snack by an apple. I wrote from National Radio Astronomy Observatory, Green Bank, where I had gone to undergo summer training, with misgivings, to the Graduate Students Advisor of the Department of Physics to let me know how I had fared in Professor Chandrasekhar's course and whether the University would continue to give me financial assistance in the next academic year. I received a reassuring reply that Professor Chandrasekhar was happy with my performance and that the University would be pleased to support my further graduate studies. I have narrated this incident at length because it brings out how a teacher probed the mind of each of his students so painstakingly and without complaining of an inordinate demand on his time in spite of pressure of research and other professional commitments.

Although, I chose to work in the field of theoretical high-energy physics, not of direct research interest of Professor Chandrasekhar, Chandra decided to be one of the four advisors for supervising my doctoral studies. I began to experience Chandra's warmth from smile on his face in acknowledging my greetings. Gradually I started to know the real Chandra and Mrs. Chandrasekhar. Occasionally I would join both of them at dinner table in the restaurant of the International House and listen to episodes from the life of the esteemed Professor, as narrated by his wife. She knew how uncomfortable students were in Chandra's presence and that we felt elated and inspired on being chosen to be shared stories from the life of the great man. One story on how Chandra handled his graduate students I contribute to this essay, because I was the second party in the incident. I wanted to fix up with my advisory group the date and time for holding an assessment, a requirement of the Ph.D. course. Meeting Chandra in his Office in the Laboratory for Space Research and Astrophysics was difficult as an appointment was required. But I knew Chandra's daily habits and decided to catch him during his walk to the laboratory. I accosted Chandra and asked point blank whether he would be in station on such and such date and whether he could be available for conducting my assessment. He suggested that I defer the assessment for a week. I told him, 'Chandra, do I not come under your priority and can you not spare half-an-hour for a graduate student?' Chandra's immediate response was a yes to the scheduling of my assessment on the date I had proposed but he said, 'Maheshwari, can you explain the concept of negative temperature?' Chandra continued to remind me whenever I met him since that I had pleaded to him to postpone the assessment for another month so I could prepare myself better.

In between I used to meet Chandra to discuss physics and sometimes he would walk to me at my desk with some newspaper reports on India in his hand and share his anguish. He once asked me to explain to him the concept of pseudo energy-momentum tensor for the gravitational field. I felt honoured in having been approached by the Professor but specially privileged when Professor Chandrasekhar gave me a person-to-person seminar on how he had used this concept in his research work. This aspect of his life is also important because he took pride in pointing out that he benefited in research more from his students than from his colleagues in the University. In 1969 he told me that during the course of his career in the University except for one research paper, which he had jointly written with Enrico Fermi, all his research work was either independent or was carried out with his graduate students.

He would emphasise to me the importance of diligence and observance of discipline in daily working habits. He emphasised that personal targets had to be continually advanced further so that life may remain an unending challenge without ever getting the feeling of arrived at.

He once mentioned that in having decided to live abroad he could only live the life of a scientist. From his own experience he pointed out that living the life of a scientist in a foreign country is extremely difficult and very rarely and very few persons can hope to contribute to science at levels that bring lasting recognition and scientific immortality. At the age of nineteen, Chandrasekhar had made the scientific discovery of the existence of a fundamental stellar mass from his study of the physics of white dwarf stars, the famous Chandrasekhar limit. Although Chandrasekhar had carried out his monumental work during his long sea voyage to England from India in 1930 and published it in 1931 in the Astrophysical Journal of the University of Chicago, but was awarded the Nobel Prize in physics for this work only in 1983. Chandra did not let recognitions slow down his pace of work and kept on moving his targets throughout his life; to wit physics of white dwarf, stellar structure and radiative transfer, magneto-hydrodynamics, mathematical theory of black holes, study of Newton's Principia.

He was a perfect embodiment of what he practised and his advice to his students was based on his experience. He might have influenced me in deciding to return to India after getting my Ph.D. degree. In what follows next I would describe the role he played in my later professional life.

Professor Chandrasekhar was happy to know when I informed him that I had joined the University at Simla. Once, he wrote to me that while taking a walk at Aspen in the Rocky Mountains in the U.S.A. he imagined that in Simla I would also be similarly situated in an ideal setting conducive for pursuing theoretical physics. Soon after, in early 1973, I met Chandra in New Delhi. He asked me how I was progressing with my work and if there was something he could do to help me. I told Chandra, "Nice climate and beautiful natural environment are fine but I need journals to do my scientific work, which the new University I had joined was unable to provide me." Chandra on the spot decided to gift to the Himachal Pradesh University his entire personal collection of journals. Within three months of that fateful meeting the Himachal Pradesh University received collection dating back to 1935 of the Physical Review, the Physical Review Letters and the Reviews of Modern Physics. This gift by Professor Chandrasekhar was without any expectation in return except that the journals should be made available for research consultation to all students and faculty. This act of generosity is unparalleled and brings out his genuine concern for his students and interest in their academic growth.

What has been described here is a humble tribute of an Eklavya to his Dronacharya. His other pupils will have similar stories to recount on how this great teacher influenced their life.

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