National Geographic : 1937 Sep
NATURE'S MOST DRAMATIC SPECTACLE BY S. A. MITCHELL Scientific Leader, National Geographic Society-U . S. Navy Eclipse Expedition, 1937 * With Illustrations from Photographs by Richard H. Stewart IKE a hungry small boy sitting down to Thanksgiving dinner, an astronomer at a total eclipse of the sun is there to get all he can while he has the chance. The boy is determined to stuff himself with as much turkey as possible while it lasts, and the astronomer is eager to gather in all the knowledge of the sun that he can during the brief few minutes of favorable condi tions created by a total eclipse. A real "eclipse feast" on June 8, 1937, was the happy lot of the National Geo graphic Society-United States Navy Expe dition to Canton Island, far out in the mid Pacific (maps, pages 364, 380). To digest this "Thanksgiving dinner of knowledge" and prepare its complete results will take many months, but I can give Na tional Geographic Society members at least a preliminary report of what we learned and why we were anxious to travel to a place 6,500 miles from home to see the sun eclipsed for only 213 seconds. A LITERAL "CHANCE OF A LIFETIME" A total eclipse of the sun takes place about once every three years in some part of the earth accessible enough for astrono mers to view it, and even then clouds or rain may blot out the sight and render a long journey and large expense futile. Why not study the sun at home, where it may be seen any day? Because some of the most important features of the sun can be observed only during an eclipse, when the moon shuts off the glare of the sun's light, or can be seen best at that time. Scientists starting out for an eclipse are truly "grasping the chance of a lifetime," because the average eclipse lasts only about three minutes. Therefore an astronomer, with the best possible luck, cannot expect more than one hour's total time for observ ing eclipses in his entire life! No wonder then that astronomers are willing to gamble on the chance of bad weather and travel half around the world, risking disappointment, as has often hap pened, or like Father Stephen Perry, leader of a British expedition to Cayenne, French Guiana, in 1889, to carry on even when taken suddenly ill, and knowing death is near. With observations successfully completed the stricken scientist called for three cheers, saying, "I can't cheer myself, but I'll wave my helmet!" Our own expedition, fortunately, was marred by neither illness nor accident, but we did defy the gods of bad luck enough to arrive at our island on May 13, and set up camp on shore with 13 scientists and officers and 13 sailor assistants! But thirteen must have been our lucky number. The skies over the island were clear and free of haze throughout the total phase of the eclipse, and our observations were made under conditions practically ideal, which rarely have been excelled in eclipse history. Astronomers do not travel to a desert island, as we did, or to some other remote part of the world, merely to be spectators at the gorgeous spectacle of an eclipse of the sun. More than one scientist has traversed vast distances to observe an eclipse, knowing all the time that he would not see it himself, because while it goes on he must remain shut up in a dark room to operate his apparatus. The scientists of our own expedition, busily working their instruments most of the time, had a chance to look at the eclipse only for a few seconds of the total duration of three and one-half minutes. Why make photographs and other ob servations of the eclipsed sun? One striking answer is the fact that, as a direct result of observing eclipses, we * Herein the National Geographic Society pre sents to members a preliminary report of the highly successful eclipse expedition jointly spon sored by their Society and the U. S . Navy. Dr. S. A . Mitchell, the scientific leader, is Director of the Leander McCormick Observatory, University of Virginia, and President of the Commission on Eclipses of the International Astronomical Union. Captain J. F . Hellweg, U. S. N., commanding the Navy detachment (page 377), is Superintendent of the U. S. Naval Observatory, Washington, D. C. "A brilliant success, far beyond our most extrava gant expectations, has attended our venture," was Dr. Mitchell's preliminary bulletin to The So ciety's headquarters. It will require many months for complete study of all the expedition's findings.