THE REVOLUTIONS BOOK I.

is assigned [to the Earth], the very same motion will appear in all things which are outside of it, but in the opposite direction, as if they were passing by. This is especially true of the daily revolution. For this daily revolution The perceived 24-hour rotation of the stars around the Earth. seems to carry along the entire universe, except for the Earth and those things around it. However, if you were to grant that the heavens have no part in this motion, but that the Earth rotates from west to east, you would find—if you considered the matter seriously—that this is indeed the case regarding the apparent rising and setting of the Sun, Moon, and stars.

And since the sky is that which contains and covers all things, the common place of the universe, it is not immediately obvious why motion should not be attributed to the thing contained rather than to the container, or to the thing located rather than to the one that provides the location. Indeed, this was the opinion of Heraclides and Ecphantus the Pythagoreans, as well as Nicetas of Syracuse (as mentioned in Cicero), who envisioned the Earth rotating in the center of the universe. They believed that the stars "set" because they were blocked by the Earth, and "rose" because the Earth moved away from them.

Once this is assumed, there follows another no less serious doubt concerning the location of the Earth, even though almost everyone has now accepted and believed that the Earth is the center of the universe. For if someone were to deny that the Earth occupies the middle or center of the universe, yet did not believe the distance was so great that it could be compared to the sphere of the fixed stars The distant stars that do not change their positions relative to one another, unlike planets., but was significant and evident relative to the orbits of the Sun and other stars; and if he thought that for this reason their motion appeared different—as if they were regulated by a center other than the center of the Earth—he might perhaps be able to provide a sound reason for their apparent diverse motion. For the fact that the wandering stars original: "errantia sidera"; refers to the planets. are seen closer to the Earth at one time and further away at another, necessarily proves that the center of the Earth is not the center of their orbits. Thus it is not even certain whether the Earth moves toward and away from them, or they move toward and away from the Earth.

It would not be so surprising if someone, in addition to that daily revolution, should imagine some other motion for the Earth. Indeed, the Pythagorean Philolaus—a mathematician of no ordinary skill—is said to have believed that the Earth rotates and even wanders through space with several motions, being "one of the stars." Those who have written the life of Plato record that Plato did not hesitate to travel to Italy specifically for the sake of visiting him.

Many, however, have believed it could be demonstrated by geometric reasoning that the Earth is in the center of the universe, and that compared to the vastness of the heavens it is like a point, occupying the place of a center, and is for that reason immobile, because when the universe moves, the center