CHAPTER VIII ASTRONOMY THE sky lies very close about us when we are children; our horizon is indeed very limited. By traveling over the earth's surface we can extend our horizon laterally, but only by the study of astronomy can we see beyond the blue dome of our prison-house to the innumerable heavenly bodies that occupy the realms of space. Astronomy is the oldest of the natural sciences. Such simple phenomena as the rising and setting of the sun, the variation in the shape of the moon, the wandering of the planets among the stars, and the changes of the seasons must have caused the wisest men of old to wonder and ponder; while a total eclipse or a meteoric shower was enough to frighten the bravest of them almost out of their senses. The ancients believed that all human affairs were controlled by the stars, and astrologers scanned the heavens continually for signs and prophecies of coming events; so that the science of astronomy was really advanced to a considerable extent by astrology. About 600 B. C., Thales discovered the equinoxes and solstices; while Anaximander, another wise man of Greece, invented the sun-dial and worked out the reason for the phases of the moon. A little later, Pythagoras asserted that the earth is not fixed, but moves in the heavens, and that the evening and morning star are the same planet, then called Phosphorus instead of Venus. Anaxagorus noticed the mountains and valleys in the moon and thought it was inhabited. He discovered that an eclipse of the sun was caused by the moon coming between the earth and the sun; and he also learned that the planets, of which he knew five, moved through the heavens, while the stars seemed to be fixed. Eudoxus, born about 400 B. C., made a map of all the stars then known; while Democritus, famous for his theory of creation by means of "dancing atoms,' guessed that the Milky Way was composed of millions of stars so small that the eye could not distinguish them. [If those old philosophers had only possessed a pair of opera glasses!] Shortly after this, Aristotle gathered together the facts that were known about astronomy and was able to assert that the earth was not flat, but round. Passing over the Dark Ages, and Copernicus, and Tycho Brahe, we arrive at the beginning of the seventeenth century, when Galileo, with the aid of a crude telescope, dissolved the Milky Way into stars, discovered four moons about Jupiter, saw the phases of Venus, first observed spots on the sun, and startled the world by stating and proving that the earth moves around the sun. And the wonder of all this is that it happened so recently! Galileo's house is still standing in the southern part of Florence, on the slope of the hill where he used his telescope to such good advantage. Kepler's laws; Newton's great theory of gravitation explaining the movements of the heavenly bodies; the discovery of Uranus and the study of nebulae by William Herschel; and a closer investigation of comets and meteors by various observers gradually led up to the era in which we live, when keen-sighted men, with powerful telescopes never dreamed of before, are continually wresting new secrets from the starry depths of space and revealing wonderful truths that far surpass the wildest fancies of the greatest astrologers. THE MOON The moon looks large and is large, for a moon, and it has figured very extensively in the affairs of men; although its influence, if we except the tides, has been mostly sentimental and fanciful. The distance of the moon from the earth is roughly 240,000 miles, or about one-four-hundredth part that of the sun; and its diameter is a little over 2,000 miles, which is over one-fourth the diameter, and one fiftieth the size, of the earth. Compare these figures with the size and distance of the tiny moons of Mars! Although large, the earth is so much larger that its attraction prevents the side of the moon next to it from moving away from it, so that we never see but one side of the moon; the same that Galileo saw with his telescope. With modern telescopes, it has been possible to study the surface of the moon so closely that it is better known than many parts of the earth. Careful maps have been made showing the ten mountain ranges, the numerous volcanic craters, the great plains, or "seas," and the "rills," "clefts," and "rays." If lakes, forests, or cities existed, they could easily be seen, although one could hardly expect to distinguish an individual building. The moon is "dead" and has long been so: there is no air, no water, no clouds, no storms, no twilight, nothing to blanket the surface during the long night lasting two weeks, when the temperature must fall to 200° below zero, and nothing to shield it from the glaring sun during the cloudless day a fortnight in length. The air and water have been absorbed by the lunar rocks on cooling; and the black shadows of the ancient volcanic craters sweep across the plains without even a suggestion of refractive atmosphere. One is forcibly reminded of the passage in Keats' "Hyperion," beginning: 'Deep in the shady sadness of a vale Far sunken from the healthy breath of morn, Robs not one light seed from the feathered grass, THE PLANET MARS Owing to its fiery-red color and variable size, Mars was one of the first planets noticed by the ancients. When nearest the earth, it rivals Jupiter; and when farthest away, it is less conspicuous than the north |