File:Dante and the early astronomers (1913) (14780456421).jpg

Identifier: danteearlyastron00ever (find matches)
Title: Dante and the early astronomers
Year: 1913 (1910s)
Authors: Evershed, M. A. (Orr)
Subjects: Dante Alighieri, 1265-1321 Dante Alighieri, 1265-1321 Astronomy
Publisher: London : Gall & Inglis
Contributing Library: PIMS - University of Toronto
Digitizing Sponsor: University of Toronto

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Text Appearing Before Image:
Fig. 29. The Epicycle.Ptolemys method of accounting for movements such as those shown in Fig. 28,
Text Appearing After Image:
Fig. 30. Planet retrograding, and in opposition (i.e. in opposition to the sun.) PTOLEMY. 141 two motions neutralize one another, so that it appearsstationary, as Mars did on August 22, 1909. Afterthis, the motion of the epicycle more than counter-balances the motion of the deferent, and the planetseems to reverse its direction until it reaches thepoint on the epicycle marked S. After this the twomotions are once more in the same direction, so theplanet is seen to move rapidly forward, as Mars didafter October 26. In this extremely ingenious way the strangeplanetary oscillations were accounted for, withoutviolating the law of uniform circular motion, and ina more convenient and satisfactory way than by theconcentric spheres of Eudoxus or the moveable eccentricsof Apollonius. Each of the five planets was providedwith an epicycle and a deferent, and these were madeof the proper relative size and given the right speed,so that the motions should correspond with what wesee in the sky. Ptol

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