The Material Intricacies of Coulomb’s 1785 Electric Torsion Balance Experiment

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Shech, Elay; Hatleback, Eric
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Contemporary scholars are engaged in a debate over whether Charles Augustin Coulomb’s results that he presented in his 1785 and 1787 memoirs to the Paris Academy of Sciences were attained experimentally or theoretically. In this paper, we study Coulomb’s famous 1785 electric torsion balance experiment through analysis of relevant texts and, more importantly, through a replication that is more faithful to Coulomb’s original design than previous attempts. We show that, despite recent claims, (1) it has so far proved impossible to obtain the same results reported by Coulomb in his paper of 1785, (2) Coulomb’s published results are most likely atypical, and (3) electric torsion balance experiments degenerate quickly when parameters are altered by small amounts. Acknowledgements: We wish to thank Jed Buchwald for generously making available the glass pieces of a torsion balance identical to that used by Alberto Martinez. Special thanks also to Paolo Palmieri for his important roles in replicating the electric torsion balance, discussing results and recording trials, as well as for the invaluable comments given on earlier drafts of this paper. A part of this paper was presented at the 2008 History of Science Society Annual Meeting in Pittsburgh, PA. We thank the participants of that meeting, especially Alberto A. Martinez, for helpful discussion and comments. Thank you also to Peter Heering for recent discussion and feedback. This research was supported by the Wesley C. Salmon fund, History and Philosophy of Science department, University of Pittsburgh.