. 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. og, the Sun) ; when farthestoff, in aphelion (dnb, from, and 77/Uoc, the Sun). 176. The eccentricity of the ellipse described by theEarth is only ^ so that when the orbit is represented on asmall scale, as in Fig. 40, no deviation from a circle is per-ceptible. The Earth is 3,000,000 miles nearer the Sun inperihelion (at P, Fig. 40) than in aphelion (at A). The Earth is in perihelion at present a
. 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. og, the Sun) ; when farthestoff, in aphelion (dnb, from, and 77/Uoc, the Sun). 176. The eccentricity of the ellipse described by theEarth is only ^ so that when the orbit is represented on asmall scale, as in Fig. 40, no deviation from a circle is per-ceptible. The Earth is 3,000,000 miles nearer the Sun inperihelion (at P, Fig. 40) than in aphelion (at A). The Earth is in perihelion at present about January1st, the time of the southern summer, and in aphelionabout July 1st, the period of the northern summer. This and night? What other motion has the Earth? 174. What is the shape of allthe planetary orbits ? How may ellipses differ? What kind of ellipses are theplanetary orbits ? 175. How is the Sun situated, as regards these ellipses ?When is a planet said to be in perihelion, and when in aphelion? 176. What isthe difference in the Earths distance from the Sun at these two points? Atwhat time of the year is the Earth in perihelion, and at what in aphelion? PERIHELION AND APHELION. 91. greater near-ness to theSun intensifiesthe heat of thesouthern sum-mer, and ac-counts for thefact that thetemperature ofthis season ishigher in Aus-tralia andSouthern Afri-ca than in cor-responding lat-itudes north Fig. 40.—The Eakths Okbit. S, the Sun; P, the Earthof the eaua- in perihelion; J., the Earth in aphelion. tor. About 3,600 years before the creation of Adam, theEarth was nearest to the Sun during the summer of thenorthern hemisphere, and farthest off in the northern win-ter; which must have made the northern summer muchhotter than it now is (according to Sir John Herschel, 23°),and the northern winter as much colder. 177. Velocity of the Earths Motions,—Let us now in-quire with what velocity the two motions of the Earth areperformed. As regards the diurnal motion, or rot
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectastronomy, bookyear18
