Description: 1. CONCERNING THE ORDER OF THE SPHERES OF THE SUN AND MOON AND FIVE PLANETS Now, certainly whatever one could say in general about the fixed stars, to the extent that the appearances up until now fall under our apprehension, would be pretty much like this. But since this Composition still lacks a treatment of the five planets, we shall give an exposition of them, going as far as possible with what they have in common to avoid repetition, and then adding on the plan of each one in particular. First, then, concerning the order of their spheres, all of which have their positions about the poles of the ecliptic, we see the foremost mathematicians agree that all these spheres are nearer the earth than the sphere of the fixed stars, and farther from the earth than that of the moon; that the three of which Saturn's is the largest, Jupiter's next earthward, and Mars' below that-are all farther from the earth than the others and that of the sun. On the other hand, the spheres of Venus and Mercury are placed by the earlier mathematicians below the sun's, but by some of the later ones above the sun's because of their never having seen the sun eclipsed by them. But this judgment seems to us unsure since these planets could be below the sun and never yet have been in any of the planes through the sun and our eye but in another, and therefore not have appeared in a line with it; just as in the case of the moon's conjunctive passages there are for the most part no eclipses. Since there is no other way of getting at this because of the absence of any sensible parallax in these stars, from which appearance alone linear distances are gotten, the order of the earlier mathematicians seems the more trustworthy, using the sun as a natural dividing line between those planets which can be any angular distance from the sun and those which cannot but which always move near it. Besides, it does not place them far enough at their perigees to produce a sensible parallax. 2. ON THE AIM OF THE PLANETARY HYPOTHESES So much, then, for the orders of the spheres. Now, since our problem is to…( from page 270, first page in book)
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Binding: Softcover, Wraps
Language: English
Author: Claudius Ptolemy
Publisher: Unknown
Topic: planets
Unit Quantity: 270 pages
Subject: Science & Medicine
Original/Facsimile: Original
