Göklerin Yuvarlaklığı ve Yıldızların Dairesel Devinimi Üzerine

There is no controversy among the wise that the sky is spherical in shape and rotates with all the stars in a circular motion upon two poles, which are fixed and immovable: one of these exists in the northern region, and the other in the southern. This is demonstrated by the fact that all stars, having emerged from the east, gradually ascend, maintaining a single tenor in their motions, sizes, and intervals, until they reach the peak of the sky, and from there are borne back down toward the west in the same manner and order. These motions are observed to be performed in parallel circles, without any discrepancy in speed or delay: not otherwise than if they themselves were fixed into the surface of some sphere that carries them all around together with a single motion.