To medieval societies the rhythms of life were as predictable as the movement of the planets and could be forecast by making astrological and astronomical projections. Islamic scholars of the Middle Ages took a particular interest in the structure of the cosmos and the accurate measurement of time. Their tools were the celestial globe, the armillary sphere, and the astrolabe. Muslim astronomers made observations with these instruments to gain an understanding of the universe and to evaluate cosmological theories such as the Ptolemaic model, which held that the earth was the center of the universe. This theory had wide acceptance but was not entirely compatible with trajectories of the planets and the sun observed by leading scientists. Less critical stargazers attributed inconsistencies to observer error or misinterpretation, and their faith in the concept of destiny remained unshaken, even when their predictions failed to come true. Quirks of fate did raise interesting questions about the way life’s narrative unfolds, and the ironic implications of a belief in destiny were a recurrent theme in medieval literature.