National Geographic : 1939 May
THE MYSTERY OF AURORAS National Geographic Society and Cornell University Study Spectacular Displays in the Heavens TO learn more about the causes and nature of one of the most spectacular and baffling phenomena of the heav ens, the aurora borealis, the National Geo graphic Society and Cornell University are co-operating in conducting a systematic and comprehensive study, under the direction of Dr. Carl W. Gartlein of the Physics Department of Cornell. The study, made under a grant of funds by The Society, will extend over a three-year period. The primary station for the auroral re search is at Cornell University, Ithaca, New York. A secondary station has been established at Colgate University, Hamil ton, New York, 55 miles to the northeast. The two stations are connected by direct telephone wires to enable the separated observers to make simultaneous observa tions and photographs for use in measur ing the heights of auroral displays. A third station is being added at Hobart College, Geneva, New York, 40 miles to the northwest, to aid in making height measurements. VOLUNTEER OBSERVERS WILL REPORT Most of the formal observations and precise photography will be conducted from the stations. However, those in charge of the studies are relying for important supplemental information on interested, competent volunteer observers throughout the United States and Canada. It is sug gested that members of The Society re siding in the regions from which auroras are visible, who are interested in helping in the observations and who have a suffi cient technical knowledge, write to Dr. Gilbert Grosvenor, President of the Na tional Geographic Society, in Washington, D. C., requesting forms for reports. An aurora may be defined simply as a luminosity of the night skies, usually seen to the northward by observers in the North ern Hemisphere and to the southward by observers in the Southern Hemisphere. It may consist of ill-defined patches of light only or may be in the form of streamers, arcs, straight or wavy bands, rays fan ning out from a center, or "curtains" of light which seem to hang downward. One of the rarest forms is the corona which appears close to the zenith. In most auroral displays the light is greenish white, but in brighter displays it may be yellowish, greenish, or red. In some cases the light forms are stationary; in others they change slowly or rapidly in position, in brightness, or in color. In the studies of the aurora by the Na tional Geographic Society and Cornell Uni versity, efforts are made to assemble data about each visible aurora, showing the forms, intensities, colors, and movements. Some of these data can be recorded photographically, and numerous photo graphs are taken of each display. Measure ments are made later from the photographs to determine the intensity and height. With a special spectrograph studies are made of the color of the aurora and of the character of the gases involved. One project of special interest is the measurement of the heights of the various auroral displays, with particular reference to variations in height with latitude. The physical activity that causes auroras presumably has been occurring for hun dreds of millions of years-as long as there have been an earth with its atmosphere and magnetic field to serve as a target, and a sun to bombard it with countless billions of light waves and tiny electrified particles. FORTY DAYS OF CELESTIAL HORSEMEN The writer of a book included in some versions of the Old Testament tells of the appearance in the heavens, about 170 B.c., of strange lights, believed by commentators to have been auroral displays. The pas sage referred to, which is in Maccabees II, Chapter 5, of the Douay version of the Bible, says: Through all the city (Jerusalem), for the space of almost forty days, there were seen horsemen running in the air, in cloth of gold, armed with lances, like a band of soldiers; and troops of horsemen in array encountering and running one against another, with shaking of shields and multitude of pikes, and drawing of swords, and casting of darts, and glittering of golden ornaments and harness.