Wali replies: Michael Nauenberg contends that Chandra was aware of Wilhelm Anderson’s work related to relativistic effects on white dwarf stars and cites Chandra’s letter to his father on 30 August 1929. In it, Chandra indeed wrote,
As for my paper, as I had nearly completed, writing it out, a paper by a German—Wilhelm Anderson appeared discussing the same problem. Even mathematically his treatment was identical to mine. So the satisfaction is that I was able to do it independently. I do not intend sending it for publication.1
A careful look shows that the Anderson paper Chandra wrote about could not have been the one about relativistic corrections to electron degeneracy2 that Nauenberg refers to. In the immediately previous letter to his father in early June 1929, Chandra listed five papers, four of which he had submitted for publication. About the fifth one he wrote, “I may send a note to ‘Nature’ this week on ‘The Einstein’s method of deriving the Planck’s formula and the new statistics.’ ” It was this paper Chandra had in mind in his 30 August letter to his father, and it had nothing to do with the theory of white dwarfs.
Chandra had come across Ralph Fowler’s paper but did not work on the theory of white dwarfs until the early spring and summer of 1930. At that time he learned that he had been awarded a Government of India scholarship to go to England and opted to go to Cambridge University to work under Fowler. He had with him a paper he had completed before his departure from Madras. By combining Fowler’s ideas with Arthur Eddington’s polytropic considerations for a star, Chandra had been able to obtain a more detailed picture of a white dwarf. One conclusion in the paper, that the central density was six times the mean/average density, led him to think of the necessity of relativistic effects and led to the derivation of the critical mass limit on his voyage to England. To the best of my knowledge, Chandra was not aware of either Anderson’s or Edmund Stoner’s work before he arrived in Cambridge.
Chandra was certain about his calculation of the maximum mass. But it is not surprising that he said, “At first I didn’t understand what this limit meant and I didn’t know how it would end.” His conclusion that a star has a mass limit that can be calculated in terms of fundamental laboratory constants would cause anyone to be puzzled, especially coming as it did from one who had just completed his undergraduate degree.
Chandra was confident that his result was correct in the extreme relativistic limit (ideal white dwarf, as he says). In the following years, he did try to fit various models in the framework of Eddington’s standard model for a star and to incorporate some of Edward Arthur Milne’s ideas for collapsed configurations. Since stars much more massive than the critical mass existed in nature, it was not unreasonable to try various ideas. How is the idea that a star is a uniform, homogeneous sphere of constant density in Anderson’s and Stoner’s work any less ad hoc than what Chandra was trying to do?
Nauenberg contests Freeman Dyson’s account (PHYSICS TODAY, December 2010, page 44) and mine about reactions of Fowler and Milne to the two papers Chandra presented on his arrival in Cambridge. But he is mistaken about Milne’s 2 November letter. It was not about the publication of Chandra’s critical mass limit paper, but of a paper related to the extension of Milne’s own work. Readers can see my full account of the essential facts in my unabridged letter, online at http://www.physicstoday.org/resource/1/phtoad/v64/i7/p9_s1.
As regards Eric Blackman’s comment, appropriate references have been amply recorded in published papers. In PHYSICS TODAY (October 1982, page 33) I noted, “Von Wilhelm Anderson and Edmund Clifton Stoner had independently considered relativistic effects on electron degeneracy. Their work implied the existence of a limiting mass.” In a comprehensive review, Werner Israel, after a detailed discussion of the works of Anderson and Stoner, writes,
In the calculations of Stoner and Anderson the astrophysical aspects were handled very schematically: the star was simply idealized as a sphere of uniform density. In view of the crudeness of this approximation it must be considered fortuitous their estimates for the critical mass came so close to the correct value of 1.44 solar masses (for a helium star). The definitive value was obtained by the 19-year-old Subrahmanyan Chandrasekhar in July 1930 (without knowing at the time of Stoner’s work) during a sea voyage from India to England.3
As Blackman points out, Chandra also recorded appropriate references to the papers of Anderson and Stoner, as well as to Sterne, Frenkel, Landau and Jutner.
I leave it to Blackman to prioritize and place Chandra in his proper place.
