Kitap 12
10
And he held that the motion of the planets involved in each case four spheres; and that of these the first and second are the sameNot the same, but having the same motion. as before (for the sphere of the fixed stars is that which carries round all the other spheres, and the sphere next in order, which has its motion in the circle which bisects the zodiac, is common to all the planets); the third sphere of all the planets has its poles in the circle which bisects the zodiac; and the fourth sphere moves in the circle inclined to the equator of the third. In the case of the third sphere, while the other planets have their own peculiar poles, those of Venus and Mercury are the same.
11
Callippusof Cyzicus (fl. 380 B.C.). Simplicius says (Simplicius 493.5-8) that he corrected and elaborated Eudoxus’s theory with Aristotle’s help while on a visit to him at Athens. assumed the same arrangement of the spheres as did Eudoxus (that is, with respect to the order of their intervals), but as regards their number, whereas he assigned to Jupiter and Saturn the same number of spheres as Eudoxus, he considered that two further spheres should be added both for the sun and for the moon, if the phenomena are to be accounted for, and one for each of the other planets.
