National Geographic : 1943 Jul
The Heavens Above On Land, Sea, and in the Air the Stars Serve Modern Man as Map, Compass, and Clock BY DONALD H. MENZEL * With 12 charts, designed by the author, showing star positions for each month, and 13 drawings of the constellations by Carlotta Gonzales Lahey SINCE Stone Age times the stars have excited man's interest and wonder. During the present war, however, with airplanes and ships navigating over vast areas of land and sea, a knowledge of the heavens is more important than ever before. Every person in the Army and Navy, or who is likely to be, should know at least a few of the stars used for reference in naviga tion-the art of locating one's position on the earth's surface. He never can tell when such knowledge may save his own life or that of a comrade. If he knows the stars, along with even the simplest principles of navigation, he can chart a course for thousands of miles if need be, and safely steer a boat or maneuver a life raft to friendly shores. The man who knows the stars is never entirely lost on land, sea, or in the air, as long as the sky is partly clear. Constellations Help Map the Stars The best way to find London on a map is first to look for England. Similarly, the best way to learn the stars is first to learn the constellations in which they belong. The stars are strewn over the sky in a more or less haphazard fashion; any pat terns one notices are the result of accident. And yet the human eye may almost auto matically recognize outlines or groups of stars that seem to be related, because of their apparent nearness to one another. These are the constellations, artificial groupings of the infinite variety of patterns of the stars. Of course, two stars that ap pear to be side by side in a constellation really may not be neighbors at all. One may be many times farther away from the earth than the other. Men began to notice the various star groups before the dawn of civilization. Later they saw in the constellations fanciful resemblances to animals or human beings, and wove legends about the imaginary figures in the sky. The star groups are named for the legendary characters they are supposed to represent, such as Hercules or Cassiopeia. These accidental star patterns serve a use- ful purpose as "guideposts" of the sky. Every airplane pilot and navigator, and every officer of a naval or merchant vessel should know the constellations as tools of his trade. They help him to find the stars he uses in navigation. For example, Polaris, the North Star, is at the end of the handle of the Little Dipper, or Little Bear (page 100), and the two stars at the front of the bowl of the Big Dipper, or Great Bear, point almost directly toward it. Navigational stars include all first-magni tude stars and enough of second magnitude to provide a series of reference points well dis tributed over the sky. The navigator meas ures the angles above the horizon of two well separated stars, nearly simultaneously. At the time of observation the stars make these angles with the earth at only one place. Ref erence tables show what that place is, and that is the navigator's latitude and longitude. There are 55 stars selected for use in naviga tion, so that at night wherever you may be on the earth's surface some navigational stars always are visible unless the sky is completely covered by clouds. War Turns Men's Eyes to the Skies War has brought about an increased inter est in the stars. Soldiers and sailors on long ocean voyages are encouraged to learn the constellations. The dim-out of coastal cities and towns has had its compensations for sky gazing amateurs who, for the first time per haps, are able to see relatively faint stars previously dimmed by brilliant city lights. Many an air-raid warden, on duty in a blackout, has noticed how bright the stars appear when man-made lights are off. Even aircraft spotters, on the watch for enemy bombers, might use the constellations in indicating the course of airplanes. If an observer reported a plane moving on a line from Aries to the Pleiades, for example, its course would be accurately fixed if those receiving the report also knew their con stellations. Since earliest times the mariner has used * The author is Professor of Astrophysics at Har vard University, and is serving at present as a Lieutenant Commander in the United States Naval Reserve.