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Updated: May 8, 2025
Without this provisional belief, wrong as it was, there could not have been that comparison of positions which showed that the motions are not representable by circles; and which led to the hypothesis of epicycles and eccentrics.
But astrology was not the only end to which mathematics were then turned. Claudius Ptolemy, the astronomer and geographer, was at that time the ornament of the mathematical school of Alexandria. In his writings he treats of the earth as the centre of the heavens, and the sun, moon, and planets as moving in circles and epicycles round it.
Observations, as good as could be made by simple instruments, had not only demonstrated in a general manner the progressions, retrogradations and stations of the planets, but attempts had been made to account for, or rather to represent them, by the aid of epicycles. It was thus in Alexandria, under the Ptolemies, that modern astronomy arose.
They explained the doctrine of the sphere and the apparent motions of the planets, but they had no instruments capable of measuring angular distances. The ingenious epicycles of Ptolemy prepared the way for the elliptic orbits and laws of Kepler, which in turn conducted Newton to the discovery of the law of gravitation, the grandest scientific discovery in the annals of our race.
Here you will find Aristotle, the overseer of learning, to whom belongs in his own right all the excellent knowledge that remains in this transitory world. Here Ptolemy weaves his cycles and epicycles, and here Gensachar tracks the planets' courses with his figures and charts.
That is to say, these astronomers probably did not conceive either the epicycles or the greater spheres as constituting actual solid substances. Subsequent generations, however, put this interpretation upon the theory, conceiving the various spheres as actual crystalline bodies.
We have sufficiently detailed the theory in speaking of Hipparchus. It should be explained, however, that, with both Hipparchus and Ptolemy, the theory of epicycles would appear to have been held rather as a working hypothesis than as a certainty, so far as the actuality of the minor spheres or epicycles is concerned.
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