Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-06T13:07:14.208Z Has data issue: false hasContentIssue false
  • English
  • Français

Galileo and the Problem of Free Fall

Published online by Cambridge University Press:  05 January 2009

R. H. Naylor
R. H. Naylor
Affiliation:
Division of Philosophy, Thames Polytechnic, Wellington Street, London SE18 6PF.
Get access Rights & Permissions [Opens in a new window]

Extract

There can be little doubt that 1973 will remain notable as a year in which knowledge of Galileo's mechanics increased dramatically. Professor Stillman Drake's publication, in May, of some of Galileo's early work on the law of free fall was followed in the autumn by the publication of a number of important manuscripts clearly indicating Galileo's use of precise measurement. From a discussion of these manuscripts and Thomas Settle's performance of Galileo's inclined plane experiment, Drake implies that a clear view of Galileo's use of experiment is now emerging. Added emphasis was given to Drake's thesis that doubts concerning Galileo's use of experiment were largely unfounded, by James MacLachlan's realization of a Galilean experiment which was previously described as ‘imaginary’ by Koyré. The purpose of this paper is to suggest that, while it cannot be doubted that Galileo used experiment and precise measurement, his attitude to observation may well have been far more complex than Drake has supposed. My point of departure is James MacLachlan's remark that continuing disagreement over Galileo's use of experiment should lead to further examination of Galileo's experimental claims. I shall indicate that more than one view of Galileo's use of experiment may prove capable of explaining our present knowledge—a corollary of this being that alternative explanations may be proposed for the manuscripts recently published by Drake.

Type
Research Article
Information
The British Journal for the History of Science , Volume 7 , Issue 2 , July 1974 , pp. 105 - 134
Copyright
Copyright © British Society for the History of Science 1974

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

The reconstruction of Galileo's inclined plane experiment was only made possible by the support and assistance received from my Faculty (Social Sciences and Humanities) and the Faculties of Science and Engineering at Thames Polytechnic. For this support, I am particularly grateful to Miss V. Pitt, Mr M. Yolles, Mr I. Bittle, and Dr R. A. M. Scott. The many discussions of this and other of Galileo's experiments with Dr Scott were of considerable help in the preparation of this paper.

1 Drake, Stillman, ‘Galileo's discovery of the law of free fall’, Scientific American, ccxxviii (1973). 84–92.CrossRefGoogle Scholar

2 Drake, Stillman, ‘Galileo's experimental confirmation of horizontal inertia: unpublished manuscripts’, Isis, lxiv (1973), 291–305.CrossRefGoogle Scholar

3 Settle, Thomas, ‘An experiment in the history of science’, Science, cxxxiii (1961), 19–23.CrossRefGoogle Scholar

4 MacLachlan, James, ‘A test of an “imaginary” experiment of Galileo's’, Isis, lxiv (1973), 374–9.CrossRefGoogle Scholar

5 Koyré, Alexandre, ‘An experiment in measurement’, Proceedings of the American Philosophical Society, xcvii (1953), 224.Google Scholar

6 MacLachlan, , op. cit. (4), p. 375.Google Scholar

7 MSS. Galileiani, , Biblioteca Nazionale di Firenze, vol. lxxii, folios 114, 116vGoogle Scholar. See Drake, , op. cit. (2), pp. 297, 301.Google Scholar

8 Galileo, , Dialogue concerning the two chief world systems, trans. Drake, S. (Berkeley, 1967), pp. 144–5Google Scholar; Opere [Edizione Nazionale], ed. Favaro, A. (20 vols., Florence, 1890–1909), vii. 171.Google Scholar

9 Galileo, 1967, op. cit. (8), trans. Drake, p. 145.Google Scholar

10 Galileo, , Dialogues concerning two new sciences, trans. Crew, H. and de Salvio, A. (New York, 1963), p. 163.Google Scholar

11 Drake, , op. cit. (2), p. 300.Google Scholar

12 Drake, , op. cit. (1), pp. 84–92.Google Scholar

13 Drake, , op. cit. (2), p. 300.Google Scholar

14 Galileo, , Opere, viii. 373Google Scholar. The translation appears in Drake, Stillman, ‘Galileo's 1604 fragment on falling bodies’, The British journal for the history of science, iv (1968–1969), 342.Google Scholar

15 Drake, , op. cit. (14), p. 349.Google Scholar

16 Galileo, , op. cit. (10), p. 171Google Scholar; Opere, viii. 213.Google Scholar

17 Settle, , op. cit. (3), p. 20Google Scholar, and Drake, , op. cit. (13), p. 349.Google Scholar

18 Galileo, , op. cit. (10), p. 171.Google Scholar

19 Drake, , op. cit. (14), p. 349Google Scholar, and op. cit. (1), p. 91.Google Scholar

20 Drake, , op. cit. (14), pp. 340–3Google Scholar, and op. cit. (1), pp. 84–92.Google Scholar

21 Galileo, , Opere, x. 97–100Google Scholar, and op. cit. (10), p. 181.Google Scholar

22 Galileo, , Dialogue, op. cit. (8), trans. Drake, p. 26.Google Scholar

23 Mersenne, M., Harmonie universelle (Paris, 1636), pp. 111–38Google Scholar. Quoted in Koyré, A., Metaphysics and measurement, trans. Maddison, R. E. W. (London, 1968), pp. 113–15.Google Scholar

24 Mersenne, 1636, op. cit. (23), p. 138.Google Scholar

25 Drake, , op. cit. (2), pp. 291–2.Google Scholar

26 Settle, , op. cit. (3), pp. 19–23.Google Scholar

27 Settle, , op. cit. (3), p. 21Google Scholar, and Drake, Stillman, ‘Free fall in Galileo's Dialogue’, Isis, lvii (1966), 269–71.CrossRefGoogle Scholar

28 Galileo, , Opere, xviii. 75–7.Google Scholar

29 Lindberg, David, ‘Galileo's experiments on falling bodies’, Isis, lvi (1965), 352–4.CrossRefGoogle Scholar

30 Galileo, , Dialogue, op. cit. (8), trans. Drake, pp. 22 and 30.Google Scholar

31 Ibid., p. 223. See also the translator's note, pp. 484–5. Galileo's copy of the first edition is owned by the Library of the Seminary in Padua. The value appears as a footnote in Opere, vii. 54.Google Scholar

32 Mersenne, 1636, op. cit. (23), p. 112.Google Scholar

33 Galileo, , On motion, trans. Drabkin, I. E. and Drake, S. (Madison, 1960), p. 69.Google Scholar

34 Galileo, , op. cit. (10), pp. 171–2.Google Scholar

35 Galileo's units cannot be identified precisely. The braccio, translated variously as cubit or yard, ranged between 20 and 25 inches. Most Northern Italian cities appear to have had a standard braccio which seems to have been essentially a measure for cloth. In my view, Koyré was over-confident in stating that Galileo's braccio was ‘doubtless’ 20 inches (or 49 cms); it was probably not very different from this figure, though a value of around 22 inches seems most likely. The uncertainty on this issue is really of marginal significance, however. Mersenne had no doubts about Galileo's braccia; it was the measurement he suspected. Settle's comments on the doubts concerning the exact value of the units cannot explain Galileo's lack of knowledge of the rate of free fall. Settle believes that Galileo's braccia was close to 22 · 7 inches; see Settle, , op. cit. (3), p. 19Google Scholar. For Drake's views on Galileo's units, see Galileo, , Dialogue, op. cit. (8), p. 471Google Scholar. See also Skinner, F. G., Weights and measures (London, 1967).Google Scholar

36 Koyré, , op. cit. (5), p. 224.Google Scholar

37 Settle, , op. cit. (3), p. 20.Google Scholar

38 Galileo, , Opere, xviii. 77.Google Scholar

39 Bernal, J. D., The extension of man. A history of physics before 1900 (London, 1972), p. 183Google Scholar. Bernal was unable to achieve success with the experiment, and he ascribed this to the fact that Galileo used better equipment. Bernal's interpretation of Galileo's description agrees well with mine; it seems clear that Bernal considered the parchment lining a refinement likely to lead to greater accuracy.

40 Drake, Stillman, Discoveries and opinions of Galileo (New York, 1957), p. 227.Google Scholar

41 Santillana, G. de, The crime of Galileo (Chicago, 1967), p. 157Google Scholar, and Broderick, J., Galileo (London, 1964), p. 117.Google Scholar

42 Galileo, , The assayer, trans. Drake, Stillman, in The controversy on the comets of 1618 (Philadelphia, 1950), p. 252.Google Scholar