File:Elements of astronomy- accompanied with numerous illustrations, a colored representation of the solar, stellar, and nebular spectra, and celestial charts of the northern and the southern hemisphere (14598202438).jpg

Identifier: elementsofastron00lock (find matches)
Title: Elements of astronomy: accompanied with numerous illustrations, a colored representation of the solar, stellar, and nebular spectra, and celestial charts of the northern and the southern hemisphere
Year: 1875 (1870s)
Authors: Lockyer, Norman, Sir, 1836-1920
Subjects: Astronomy
Publisher: New York, D. Appleton and company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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on, except at Full Moon, beingseparated from the dark one by a semi-ellipse, called, aswe have seen (Art. 228), the Terminator. CHAPTER VII.ECLIPSES. 237. In explaining the phases of the Moon, as repre-sented in Fig. 53, we supposed the motion of this luminaryto be performed in the plane of the ecliptic; but, as statedin Art. 221, this is not the case. If it were, every NewMoon would put out the Sun ; and as the Earth, likeevery body through which light cannot pass, casts ashadow, every Full Moon would be hidden in thatshadow. Such phenomena are called Eclipses, and theydo happen sometimes; let us see under what circum-stances. 238. Eclipses explained.—One-half of the Moons jour-ney is performed above the plane of the ecliptic, one-halfbelow it; hence at certain times—twice in each revolution while the Moon is waning. How is the illuminated portion separated from thedark part ? 237. If the Moons orbit lay in the plane of the ecliptic, what would be the EXPLANATION OF ECLIPSES. 125
Text Appearing After Image:
Fig. 54.—Explanation of Solab and LunarEclipses. —the Moon is in thatplane, at those partsof it called theNodes. Now, if theMoon, when in eithernode, happens to bein line with the Earthand Sun, we have aneclipse. If the Moonis new, it is directlybetween the Earthand the Sun, and theSun is eclipsed. Ifthe Moon is full, theEarth is between itand the Sun, and theMoon is eclipsed.This will be madeclear by the accom-panying diagram. In Fig. 54 wehave the Sun andthe Earth, and theMoon in two posi-tions, A represent-ing it as new, and Bas full. The levelof the page repre-sents the plane ofthe ecliptic. Wesuppose, in bothcases, that the Moonis at a node,—in theplane of the ecliptic,neither above norbelow it. 126 ECLIPSES. At A, the Moon stops the Suns light; its shadow fallson a part of the Earth, and the people, therefore, who liveon that part cannot see the Sun, because the Moon is inthe way. Hence we have what is called an eclipse of theSun. At _Z?, the Moon is in the shadow of the E

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