Astronomy for the use of schools and academies (1882) (14577493878)

Identifier: astronomyforuseo00gill (find matches)
Title: Astronomy for the use of schools and academies
Year: 1882 (1880s)
Authors: Gillet, J. A. (Joseph Anthony), 1837-1908 Rolfe, W. J. (William James), 1827-1910
Subjects: Astronomy
Publisher: New York : Potter, Ainsworth, & Co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress



Text Appearing Before Image:
Fig. 49- The ancients assumed that the planets moved in exactcircles, and, in fact, that all motion in the heavens wascircular, the circle being the simplest and most perfectcurve. To account for the loops described by the planets,they imagined that each planet revolved in a circle around acentre, which, in turn, revolved in a circle around the earth.The circle described by this centre around the earth theycalled the cycle, and the circle described by the planetaround this centre they called the epicycle. ASTRONOMY. 43 38. The Eccentric. — The ancients assumed that theplanets moved at a uniform rate in describing the epicycle,and also the centre in describing the cycle. They had,however, discovered that the planets advance eastward morerapidly in some parts of their orbits than in others. To
Text Appearing After Image:
Fig. 5°- account for this they assumed that the cycles described bythe centre, around which the planets revolved, were eccen-tric ; that is to say. that the earth was not at the centreof the cycle, but some distance away from it. as shownin Fig. 51. E is the position of the earth, and C is the 44 ASTRONOMY,