Page:Popular Science Monthly Volume 51.djvu/376

364 ; but the greatest difficulty comes when we consider the effect of the rings.

At first thought it might seem that the rings would have little to do with the climate of the planet, and in fact such is the case during the summer of either hemisphere; but winter tells a different tale, as we shall see. Since the rings lie exactly in the plane of the planet's equator, they will be presented edgewise to the sun at the equinoxes, when the sun is "vertical over the equator." At this time their shadow, part of which must fall on the planet, will lie directly on the equator, and presumably be about as wide as the general thickness of the ring system, which is estimated to be not more than one hundred miles.

As the sun travels northward from the equinox, it is apparent that the shadow will fall farther and farther south of the equator until it has covered the whole southern hemisphere, save a portion of the torrid zone where the light comes through the space between the rings and the planet. After the summer solstice the effects are reversed: the shadow retreats toward the equator, and after the succeeding equinox the southern hemisphere will have its summer undisturbed, and the northern hemisphere in turn will have its long winter made still more dreary by this remarkable daily eclipse of the sun. It thus appears that only in a relatively narrow belt lying on either side of the equator would be likely to occur climatic conditions approaching those with which we are familiar.

One often sees in articles on astronomy some reference to the grandeur of the Saturnian heavens at night, where, in addition to the starry host familiar to us all, would be the wonderful ring spanning the sky as an arch of golden light, and eight moons in their various phases. In a measure this is true, but it depends upon circumstances. During the summer half of the year in either hemisphere the illuminated side of the rings is, of course, visible perhaps—even faintly so in the daytime, as is the case with our moon; but when the twilight falls and the golden arch shines forth in all its beauty against the darkness of the sky, it must certainly be a sight which for grandeur surpasses any celestial phenomenon known to us, save possibly a total eclipse of the sun.

As soon as the sun has set, however, the shadow of the planet, where it falls upon the rings, rises in the east and mars the beauty of the arch as it travels across it during the short night and disappears in the west at sunrise. At the summer solstice, though, the sun rises high enough in the heavens, or, more correctly, the planet's axis is inclined far enough toward the sun to bring the outer ring clear of the shadow, which then appears somewhat conical in shape and reaches across the inner bright ring nearly to the outer one.