Document Type

Article

Publication Date

1-1-1984

Publication Title

Revue D'histoire Des Sciences

Department

Science, Technology and Society

Abstract

Beginning with the essential planetary phenomena to be explained, we examine the functions of the equant point and the eccentric deferent circle in Ptolemy's theory. We show that the necessity of the equant point becomes evident as soon as one attempts to save the lengths of the retrograde arcs, and the distances between them, particularly in the case of Mars. Finally, we propose a hypothesis concerning the line of investigation that led Ptolemy to discover the equant.

Volume

37

Issue

34

pp.

193-213

ISSN

0151-4105

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