Page:The New International Encyclopædia 1st ed. v. 20.djvu/923

* ZODIAC. 785 ZOE. ziiiliac, relating to animals, from l<fidLov, zodion, diminutive of fijiof, zOun, animal, from f^r, zCn, to live; so ealled because the constellations were figured as animals). The name given by the an- cients to an imaginary band extending round the celestial sphere, having as its middle line the ecliptic or api)arent path of the sun. It was fixed at about 10° in width so as to include the orbits of the sun and of the five planets (Mer- cury, Venus. Alais, Jupiter, and Saturn) which ■were then Unown ; and as, of these planets. Mer- cury has by far the greatist inclination of orbit to the ecliptic, and the value of that element in his case is only 7°, the width given to the zodiac was amply sudicient for the required purpose. But when the career of the planetary discovery commenced in the beginning of the nineteenth centurj', the first three which were discovered (Ceres, Pallas, and Juno) at once destroyed the idea which had been long seated in men's minds, that no planets existed beyond the limits of the zodiac, by exhibiting orbits inclined to the ecliptic at no less angles than 11°, 35°, and 13°; and a large number since observed have been found to wander beyond the zodiac, from which circumstance they have, along with the three above mentioned, been denominated ultra-zodi- acal planets. The stars in the zodiac were grouped into twelve constellations, to each of which 30°, or y'jth of the whole circle, was assigned, though it often did not fill up that space, but was only situated in it; and this equable division into signs was of great advantage in defining the posi- tions of the sun and planets at any epoch. The constellations, with the appropriate sym- bols of the corresponding signs, are as follows: Aries {Ram] ^ Taurus (Bull) Yj' Gemini (Ttrins) H Cancer ( Oral] ) 05 Leo (Lion) Q Virgo {Virgin) tijj Libra {Balance) =3= Scorpio ( Hcorpion ) 1J|^ S;igittarius {Archer) y([ Capricornus (Goat) jf Aquarius (Water-hearer) as Pisces (Fishes') )-( As one half of the ecliptic is to the north and the other to the south of the celestial equator, the line of intersection of their planes is a diam- eter of each, and the tw-o points in which this line meets the celestial sphere are known as the equinoctial (q.v. ) points. The comparative im- mobility, with respect to the ecliptic, of these points, suggested at once the employment of one or other of them as a point from which to reckon celestial measurements of stars' positions, and accordingly that point at which the sun crosses the equinoctial from south to north was fixed upon, and called the first point (or commence- ment ) of Aries ( q.v. ). After the sun had ad- vanced eastward through this sign — i.e. 30° along the ecliptic — he entered the sign of Taurus, contin ng his course onward through the others in the order in which they are given above, again crossing the equinoctial southward at the point where he emerged from Virgo and entered Libra. This was the case with the sun during the time of Hipparehus (q.v.), hut though the equinoctial points move very slowly, yet they do so with great uniformity, and the westerly motion of .50" annually which they describe along the ecliptic has at the present time separated the sign Aries from the constellation Aries, and caused the former to correspond almost to the constellation Pisces. This gradual retrogression of the signs through the constellations of the zodiac will continue till they accomplish, in al)out 25,S00 years, a conijilete circuit; after which period the sign and constellation of Aries will again coincide, as they did in the time of lli]iparclius. Neither the zodiac nor its constel- lations are of much use now in astronomy, ex- cept as, like the other constellations, aifording an easy though somewhat fantastic nomenclature for the stars, and a ruU: liiit sometimes conve- nient mode of reference to their jiositions. The zodiac is probably lial)yh)nian in origin. The figures seem to have been based on the re- semblance of the lines connecting the stars in the zodiacal constellations to certain pictorial outlines which form the substratum of the As- sy ro-Habylonian cuneiform alphabets (see CuNEl- I'OKM lNSCRii'TioN.s), while animal figures and outlines were chosen for animistic reasons. The greater number of the modern zodiacal constel- lations are identical with the Babylonian, al- though two or three seem to be of Occidental origin. The signs of the zodiac were carried from Babylonia to Greece, whence they spread throughout the ancient civilized world, and found their way back, along with much other astro- nomical science, to India and the Far East. Consult for the origin of the zodiac: Epping and Strassmaicr, Asdronomisches aus Babi/lon (Frei- burg, 1889) ; Jensen, Kosmologie der Bahylonier (Strassburg, 1800) ; .Lastrow, Religion of Baby- lonia and Assyria (Boston, 1898). ZODIACAL LIGHT. A faint luminosity extending outward from both sides of the sun along tlu' ecliptic. It is visible only after sunset or before sunrise. It is easily seen to reach 90° or 100° from the sun : and in favorable circum- stances of observation in the tropics, it has been recorded as encircling the sky completely. Where this latter observation has been made, a particu- larly bright spot has been noticed in the zodiacal light, located directly opposite the sun's position below the horizon. This bright spot is called by the German name Gegenschein, or 'opposing light,' from its being opposite the sun. No thoroughly satisfactory explanation has yet been found for this rather puzzling phe- nomenon. Some think it merely a very extended outer envelope of the sun. inclosing the corona (see Sun) and extending very far beyond it into space. A more plausible theory supposes the whole thing to be caused by a ring of .small particles revolving about the sun nearly in the ecliptic plane. Such a ring would have an ana- logue in Saturn's ring, and in the zone of plane- toids (q.v.). And solar light reflected from the countless particles of the ring would give the faint luminosity both of the zodiacal light and the Clcgenschein. But the whole theory of this phenomenon is still in debatable groimd, and invites further attention from astronomers. ZO'E (Lat.. from Gk. Zwii) (c.978-1050). A Byzantine empress, the last of the IMaeedonian dynasty. She was the daughter of Constantine VTTL. by wdiom .she was married to the patrician Romanus Argyrus. The latter came to the throne in 1028. but was assassinated by Zoe and her favorite chamberlain, Michael the Paphlagonian (1034). The Empress thereupon married her accomplice, who reigned as Michael IV. until 1041. After his death the Emnress elevated to the throne his nephew, Michael V.,