A Survey of the Arguments for the Immobility and Centricity of the Earth in the Hayʾa Books

The arguments for the immobility and centricity of the Earth in the Islamic astronomical literature are mostly found in the Hayʾa books. The reason is that these books treat of mathematical cosmology on the basis of solid spheres and the Earth''s position with respect to them. These arguments، which are rooted in Ptolemy''s Almagest، are based on observation and some pre-suppositions. In this article، we examine these arguments one by one and try to find their pre-supposition by way of their analysis. This analysis reaveals two major pre-suppositions: 1) for the motion to continue، the cause of the motion has to accompany the moving object; 2) the speed of a falling object is related to its wright.