Aristotle's Cosmology

Aristotle believes that the heavens are made from a fifth element, sometimes called ather. This material makes up the spheres carrying the visible heavenly dies in their circular orbits around the earth. As for the four lower elements, they move not in circles, but rather in straight lines,. down, in the case of earth and water, towards the mid point of the universe... ...and up away from the mid point in the case of air and fire. These motions are natural to the four elements. So aristotle can say that the falling rock does indeed have an internal principle of motion. Due to its earthy nature, it has a tendency to move towards the centre of the universe if