Ptolemaic Orbs in Twelfth-Century England: A Study and Edition of the Anonymous Liber de motibus planetarum

Abstract

This article offers the first study and critical edition of the Liber de motibus planetarum (Lmp), a neglected Latin text on planetary theory that appears anonymously and without any clear indication of date or place of origin in nine manuscripts of the thirteenth to fifteenth centuries. An analysis of its sources and parallels to other Latin treatises and translations from Arabic indicates that the Lmp originated in England in the third quarter of the twelfth century. A plausible terminus post quem is provided by the appearance of similar passages in the anonymous treatise Ptolomeus et multi sapientum (1145), which can be linked to Abraham Ibn Ezra and his astronomical tables for the meridian of Pisa. The Lmp would appear to be historically significant for its relatively detailed textual and diagrammatic presentations of Ptolemy’s planetary models as composed of multipart physical orbs. While it is generally accepted that physicalized or ‘orbed’ versions of these models entered Latin astronomy through the influence of Ibn al-Haytham’s Maqāla fī hayʾat al-ʿālam (On the Configuration of the World), the early history of this idea in a Latin context has not been studied to any deeper extent. In this regard, the Lmp offers clear evidence that Ptolemaic orbs and diagrams representing them already were a part of Latin astronomy three centuries before Peuerbach’s Theoricae novae planetarum (1454).