Medieval cosmology was a fusion of pagan Greek ideas and Biblical descriptions of the world, especially the creation account in Genesis. Planets, Stars, and Orbs describes medieval conceptions of the cosmos as understood by scholastic theologians and natural philosophers in the universities of western Europe from the thirteenth to the seventeenth centuries. Not only are the major ideas and arguments of medieval cosmology described and analysed, but much attention is paid to the responses of scholastic natural philosophers of the sixteenth and seventeenth centuries to the challenges posed by the new science and astronomy as represented by Copernicus, Tycho Brahe, Galileo, and Kepler.