Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 207
, as we go outwardsfrom the Sun, the periods of revolution are longer, for the 186 ASTRONOMY. double reason that the planet has a larger orbit to describeand moves more slowly in its orbit. The Earth moves 18£miles per second in its orbit, while Saturn moves but6 miles per second. An observer on… … Fig. 122.—The Motion of the Earth in Its Orbit—It isDirect Motion. stars (see page 158). The real motion of the Earth seenfrom the Sun is direct. We have proved on page 159 thatthe apparent motion of the Sun is always direct also. Theplane of the Earths orbit—the ecliptic—is the plane in MOTIONS OF…
Astronomy
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