Kitap 12
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.
12
But if all the spheres in combination are to account for the phenomena, there must be for each of the other planets other spheres, one less in number than those already mentioned, which counteract these and restore to the same position the first sphere of the star which in each case is next in order below.Aristotle is trying to establish a mechanical relation between the spheres, which Eudoxus and Callipus did not attempt to do. In this way only can the combination of forces produce the motion of the planets.
13
Therefore since the forces by which the planets themselves are moved are 8 for Jupiter and Saturn, and 25 for the others, and since of these the only ones which do not need to be counteracted are those by which the lowest planetThe moon. is moved, the counteracting spheres for the first two planets will be 6, and those of the remaining four will be 16; and the total number of spheres, both those which move the planets and those which counteract these, will be 55.
14
If we do not invest the moon and the sun with the additional motions which we have mentioned,In sect. 11. there will be 47 (?)Either Aristotle has made a slip in his calculations, or we should read ἐννέα(Sosigenes) for ἑπτά; this would give 49, which appears to be the correct total. For alternative explanations of an error in calculation see Ross ad loc. spheres in all.
