No Access Submitted: 12 September 1983 Accepted: 18 April 1984 Published Online: 04 June 1998
American Journal of Physics 52, 1080 (1984); https://doi.org/10.1119/1.13764
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  • 61 Boulevard Brune, 75014 Paris, France
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  • James Evans
We examine the roles of the equant point and the eccentric deferent circle in Ptolemy’s planetary theory. The necessity of these features of the model is demonstrated empirically by a study of the retrograde arcs of Mars. Finally, these results are used, together with available historical evidence, to suggest the line of investigation that probably led Ptolemy to his discovery of the equant.
  1. © 1984 American Association of Physics Teachers.