A Non-Aristotelian Interpretation of Orbs in the Post-Classical Islamic Age: Shams al-Dın al-Samarqandı in Science of the Cosmos and the Soul

Abstract

The history of Islamic astronomy falls under the influence of Aristotelian cosmology, in which orbs have a principal role in holding and moving the planets. Based on the prevalent accepted Aristotelian idea, these orbs are spherical shells that rotate around their center and are made of a particular substance called aether. No lightness or heaviness, rarefaction or condensation, and generation or corruption exist in the aether-filled heavens. Subsequently, any tearing or mending of these orbs is impossible. This assumption leads to a basic rule: the planets do not move in an orb but by an orb. During the medieval Islamic age, new models emerged for solving some of the anomalies in Ptolemaic astronomy; however, the assumption above was rarely disputed. This paper will introduce an unordinary case based on the book Science of the Cosmos and the Soul by Shams al-Dīn al-Samarqandī in which, besides the standard Ptolemaic system, some alternative models were briefly presented: in these new models, the tearing or mending of these orbs is possible. Considering that this assumption conflicts with Aristotelian physics, these models can be regarded as non-Aristotelian.

Keywords

• shams al-dīn al-samarqandī
• science of the cosmos and the soul
• post-classical islamic astronomy
• non-aristotelian physics
• planetary models
• ptolemaic astronomy