The ‘Great Debate’: What Really Happened

Discussions include: Struve Otto , “A Historic Debate about the Universe”, Sky and telescope, xix (1959–60), 398–401; Hetherington Norriss S. , “The Shapley-Curtis Debate”, Astronomical Society of the Pacific Leaflet no. 490 (April 1970); Struve Otto and Zebergs Velta , Astronomy of the twentieth century (New York, 1962), chaps 19 and 20, passim; and “The Great Debate”, chap. 6 of Shapley Harlow , Through rugged ways to the stars (New York, 1969). A new treatment will shortly be published in Berendzen Richard E. , Man discovers the galaxies (New York, 1976).

Shapley H. and Curtis H. D. , “The Scale of the Universe”, Bulletin of the National Research Council, ii, Part 3 (May 1921).

As shown by the official programme of the Academy meeting.

The meeting took place on 19 December. There is no reference in the minutes to Hale's suggestion.

Hale W. E. had used his wealth to support his son's projects, notably by providing the disc for the 60in. telescope eventually erected at Mount Wilson.

Archives of the National Academy of Sciences.

As shown by the letters from Curtis to his children, 8 February and 9 March 1919 (Michigan Historical Collections, University of Michigan). The script of Curtis's lecture is in the archives of Lick Observatory.

Hale microfilm.

Not surprisingly, in 1968 Dr Abbot did not recall the reason for the choice of Campbell, but remarked that Campbell was of course “a more important astronomer than Curtis” (personal communication). Mr Robert Smith points out that Campbell had supported the island universe theory in “The Nebulae”, Science, xlv (1917), 513–48.

Letter of Hale to Curtis, 24 February 1920 (Hale microfilm).

Letter of Abbot to Hale, 20 January 1920 (Hale microfilm).

Hale microfilm. Hale cabled at once to Shapley and Curtis, offering each an honorarium of $150.

Letter of 7 February 1919 (Hale microfilm): In America you have Russell and Shapley. Shapley is a brilliant man and personally I, who know him mainly only through his scientific work, would think him the best fitted for the position. Meanwhile I do not know him sufficiently to know how he would do as an organiser at the head of such a large and complicated Institution as the Harvard Observatory.

Shapley , Through rugged ways to the stars, 82.

Shapley to Russell , 12 February 1919; to Hale, 13 February 1919 (Shapley Archives, Harvard University).

Russell to Shapley , 19 February 1919 (Shapley Archives, Harvard University).

Russell to Hale , 19 February 1919 (Russell Archives, Princeton University).

Hale to Shapley , 27 February 1919 (Hale microfilm).

Shapley to Russell , 27 February 1919; to Hale, 7 March 1919 (Shapley Archives, Harvard University).

Hale microfilm.

Shapley to Russell , 6 January 1920 (Russell Archives, Princeton University).

Russell to Hale , 13 June 1920 (Hale microfilm).

Invitation dated 10 November 1920 (Shapley Archives, Harvard University).

Shapley to Hale , “Sunday”, i.e. 22 February 1920 (Hale microfilm).

Shapley to Hale, 19 February 1920 (Hale microfilm). On the 24th Hale wrote to Shapley, Curtis and Abbot approving the concept of a ‘discussion’.

Curtis to Shapley, 26 February 1920 (Shapley Archives, Harvard University).

Hale to Curtis, 3 March 1920 (Shapley Archives, Harvard University).

Curtis to E. E. Barnard, 28 January 1920 (Archives of Yerkes Observatory). Curtis reports that “most of us here find it impossible to subscribe to some of the recent theories on these points”.

Ibid. On 23 February Curtis requested from Barnard the return of this paper as a matter of urgency.

Curtis to Hale , 9 March 1920 (Hale microfilm).

Abbot to Hale , 18 March 1920 (Hale microfilm).

Shapley to Abbot , 12 March 1920 (Shapley Archives, Harvard University).

Curtis to Shapley , 14 March 1920. Since Shapley maintained to the end of his life that Curtis did not address himself to the subject of the title ( Shapley , Through rugged ways to the stars, 79), it is worth recording the synopsis Curtis proposed to Hale ( Curtis to Hale , 20 February 1920, Shapley Archives, Harvard University) and which Hale welcomed: “Dr Shapley will discuss recently secured evidence pointing to dimensions of our galaxy about ten times greater than held in the older theories of the Milky Way, i.e., a diameter of about 300,000 light-years, with the spiral nebulae regarded as a galactic phenomenon. Dr Curtis will defend the older view that our Milky Way is approximately of the dimensions suggested by Newcomb, i.e., about 30,000 light-years in diameter, with the spiral nebulae regarded as very probably individual galaxies, or ‘island universes’”.

Shapley to Curtis , 18 March 1920 (Shapley Archives, Harvard University).

Curtis to Shapley , 14 March 1920 (Shapley Archives, Harvard University).

Shapley to Russell , 31 March 1920 (Shapley Archives, Harvard University).

Shapley to Curtis , 27 July 1920 (Shapley Archives, Harvard University).

Shapley Archives, Harvard University.

Curtis to Shapley , 2 August 1920 (Shapley Archives, Harvard University).

Shapley to Curtis , 9 June 1920; Curtis to Shapley, 13 June 1920 (Shapley Archives, Harvard University).

Shapley , Through rugged ways to the stars, 79–80. In private conversation Shapley was much more emphatic as to his disappointing performance.

Michigan Historical Collections, University of Michigan.

Russell to Hale , 13 June 1920 (Hale microfilm).

Writing to Shapley on 10 July 1922, Curtis spoke of “our memorable set-to” (Archives of Allegheny Observatory). C. D. Shane of the University of California (Berkeley) wrote to Curtis on 3 December 1923 about “the famous debate”, and Curtis in reply on the 10th again referred to “our memorable set-to” (Michigan University Archives). Campbell, writing on “Do we live in a spiral nebula?” in Popular astronomy for 1926, speaks of the “memorable discussion” of 1920 (p. 175).

Robert G. Aitken later wrote of Curtis that “For a time only his colleagues at Mount Hamilton, and a few other astronomers agreed with him in his views” (National Academy of Sciences Biographical Memoirs, xxii (1943), 280), and this may be true, although Aitken had forgotten that he himself had been “on the fence” (cf. ref. 46 below).

Aitken to Barnard , 27 April 1920 (Archives of Yerkes Observatory); emphasis in original.

“… some fur ought to fly, on both sides”, Curtis to Hussey W. J. , formerly of Lick Observatory, 15 April 1920 (Michigan Historical Collections, University of Michigan).

“He sure is a talker…. I never saw any man better qualified to teach the unwashed astronomy then he”, “Benny” writing to Shapley of a talk by Russell to the general public at Mount Wilson, 30 June 1921 (Shapley Archives, Harvard University).

This rough typescript, now in Box 1 of the Shapley Archives at Harvard University, contains pencil amendments in longhand, and occasionally in shorthand. Those in longhand have been incorporated in this printed text. Of the typescript, the first one-third is too elementary to justify reprinting; likewise, the final three pages dealt with Shapley's intensifier, and, however significant this might have been as an instrumental advance in the study of faint stars, it was not directly relevant to the theoretical discussion and is omitted here as it was in the printed version of the proceedings (ref. 2).

The slides survive at Allegheny Observatory. Of the nine, eight are represented in modified form in the printed version of the proceedings, as indicated, and the slides have accordingly been arranged in a probable order. The title of slide H suggests that Curtis may have used other slides no longer extant, but surely very few additional slides could have been fitted into a 40-minute talk.