The idea of this article is to present some Aristotelian beliefs with respect to the heavens. According to Aristotle, this region was fully filled by a pure substance, the ether, responsible by the matter from which were comprised both the bodies belonging there as the surrounding space. For him the perfection of this region was not limited only by the purity of the substance from which it was composed, but it could also be justified by other observations. For the philosopher, the perfection of the sphere and the circular movement together with the observations were a justification for the "geometry" of this region. Thus, Aristotle develops an extremely coherent explanation about perfection in this region, which is claimed to be unique, eternal and finite. We are going to bring to the reader's knowledge these points, giving emphasis to some works of the philosopher permeated by comments from secondary sources. Finally, we present a brief summary of the first unmoved motor, which is responsible by the origin of the movement within this region. We believe that this manuscript helps the research of interested workers on the geocentric and heliocentric systems of the world.
history of science; Aristotle; geocentric system; heliocentric system