During this journey around the sun, the earth rotates 366¼ times on its axis, making one revolution every 23 hours, 56 minutes and 4.09 seconds. This causes each side to be alternately warmed and lighted every few hours. Cupped close to the darkened hemisphere lies a huge cone of shadow which extends out in space past the moon. When the moon rolls through this shadow it is eclipsed for it has come into our night. [Figure 157] This cone of the earth's shadow is our personal night and ours alone, and, although the stars seem enmeshed in its velvet sides, it is not the night of earth that holds the stars,--its darkness merely shuts out the glare of the sun and the stars of the universe therefore become visible. This remarkable view gave to man a science set in beauty so keen that in the world's young days it was thought that it was music too sweet to be heard by any but the gods. But now we know that all Nature is like that, and there is not a cliff, rock, shell, mountain, valley, water, land or any living thing in the botanical or zoological kingdom, no matter how common or how lowly, which does not carry, even as the stars, its quota of science and song. [Footnote 1: Le Conte.] [Footnote 2: De Greer, Bulletin of the Geological Society of America, vol. III, 1892.] [Figure 158: THE SOUTHERN PORTION OF THE MOON AT LAST QUARTER. Photograph by Mount Wilson Observatory through the 100-inch Hooker telescope.] CHAPTER XVII THE EARTH'S MOON A NEAR VIEW OF A SATELLITE _Diameter--2163 miles_ THE moon's diameter is equal to one-fourth that of the earth. As viewed from a nearby planet--neighbor Venus, the planetoids, or neighbor Mars--the moon and the earth would appear as two close stars. Both Jupiter and Saturn have moons larger than ours, but Jupiter, for instance, is over a thousand times larger than the earth, and Saturn ranks next to Jupiter. The moons of Mars are exceedingly tiny, and Mercury and Venus have none at all. Neptune has one moon, Uranus four, Jupiter nine and Saturn ten. Of all these moons, it is most natural for us to want complete information on the moon that lies nearest to us, the moon of the earth, which travels around us as we journey around the sun, at a distance of only 240,000 miles. With the aid of the greatest of telescopes, through which the accompanying photograph was taken, the moon can be brought within a clear range of 60 miles, and even closer. However, an opera-glass reduces the distance to one-half, and such a glass, or a very small telescope, is much better in every way for the amateur. With the nearest planets millions of miles in the distance and the nearest stars millions of millions of miles away, the short distance of 240,000 miles to the moon seems almost no distance at all; in fact, the moon lies so close to us that it not only rolls through the shadow of the earth, but we may also see the various features, and even the shadows of those features, upon its surface.