Evening Star Newspaper, April 27, 1930, Page 95

THE SUNDAY STAR, WASHINGTON, D. C, APRIL 27, Chasing Sun’s Eclipse in Airplanes 1930. 15 Photos of the sun in eclipse, taken May 9, 1929, from planes which soared 5,000 feet above the Philippine Islands. Photographing the Half-Mile-Wide Moon’s Shadow as It Sweeps Across the Earth at a Speed of Thirty-Three Miles a Minute Is a New Experiment Flying Astron- omers Will Attempt April 28. BY JAMES STOKLEY. F you happen to be some 40 miles north of San Francisco on the morn- ing of Monday, April 28, you may see several Army airplanes circling 1ound, expectantly waiting for seme- thing to happen. But probably you will not be paying much attention to the airplanes, for som-°thing else will be happening in the sky. Perhaps you have a smoked glass or a bit of exposed photographic film through which you can safely look at the sun. Instead of appearing like a round, bright disc, as usual, it seems to have a piece bitten out of the western side. The airplanes continue their waiting; the bite in the sun grows bigger. Finally the sun has almost completely vanished, its light is strangely reduced and of an unnatural yellow color. The airplanes now seem ready for action. They fly off to the northeast and soon have vanished from sight. But the sun now seems to be in a serious way. Only a thin crescent remains, ‘Then this disappears. The sun has turned into a jet-black disc; around it is a glowing ring and outside this are wings of pearly whiteness. But no sooner have you had time to exclaim in wonder at the spectacle than it disappears. Had you taken a glance to the east you would have seen two bright planets, Venus and Mer- cury. On the western side of the dark disc a thin sliver of brilliant sunlight returns. This sliver enlarges into a crescent and the entire sun gradually reappears. SUCB, in brief, are some of the things that may be seen by an observer of the next total eclipse of the sun, visible April 28 along a nar- row strip crossing California, Nevada, Oregon, Idaho and part of Montana. Astronomers scate tered along this path will make the best of the second or so of totality, recording it photo- graphically for future study by still and movie cameras and spectroscopes. The Army Air Service has given the use of several airplanes, in which Hamilton M. Jeffers, from the Lick Observatory, and other astronomers will try to make the best of a high altitude and a ravidly moving observatory. Not for years has such an eclipse as this occurred. It is of the peculiar type known as a central eclipse and ordinarily would not attract astronomers to observe it. So short is it at best that many of the ordinary eclipse observations will be impossible. But this one is considerate enough to occur in a very con- venient place. Astronomers frequently chase an eclipse half way around the world. Last May several American parties journeyed to Sumatra and the Philippines for one, Already the Naval Observatory is planning for & trip this Fall to a remote isle in the South Pacific for the same purpose. Many an eclipse expedition has been made by the Lick Ob- servatory, on Mount Hamilton, near San Jose, Calif.. to distant lands. Will be observer from aloft. Hamilton M. Jeffers will fly for the Lick Observa- sory during the coming eclipse. Mounted like a machine gun. A close-up view of the huge astronomical camera with which Army photographers will “shoot the sun.” globe of the sun is hidden; the pearly corona, and perhaps some high, scarlet “prominences,” shine above the black disc of the moon. Then, and then only, can many important astronomi- cal observations be made. The sun is about 865,000 miles in diameter and the moon only 2,200 miles, so its shadow is quite different from those generally cast by terrestrial lights. When you stand in a dark room with a candle in your hand, your shadow cast on the wall behind is much larger than you. The farther you go from the wall the larger becomes the shadow. This is because the source of the light is much smaller than your body. The sun, however, is much larger than the moon and so the shadow is smaller than the moon itself. The farther from the moon the smaller is the shadow, until finally it ends in a point. The shadow from its tip to the moon is about 240,000 miles long, and it happens that this is also the approximate distance between the moon and the earth. Both the length of the shadow and the distance between earth and moon vary somewhat, so sometimes when the earth, sun and moon are in line the shadow reaches all the way, while at other times the tip misses the .earth. When it reaches all the way the result is a total eclipse. When the shadow does not reach, a person in the path sees the moon smaller than the sun, so that a ring of sun surrounds the black moon. This is called an annular eclipse. The eclipse this month is both annular and total. This seems a paradox, but is not, because the eclipse is not annular and total at the same time. Where it begins, out in the middle of the Pacific Ocean, the tip of the shadow does not touch the surface of the ocean. Out there an observer would see the ring, or annulus, of sunlight. But as the shadow moves eastward, the earth, being spherical, bulges out to meet it. The tip comes nearer and nearer to the surface and just off the coast of California touches earth. From then on the eclipse is total and es to Jand in Marin County, just north of end. From then on the annulus is seen again along a path crossing Montana, Southern Sas- katchewan, Manitoba, passing over the southern tip of Lake Winnepegosis, then Lake Winnipeg, over the northern corner of Ontario, Hudson Bay, Northern Quebec, Labrador, then out into the Atlantic Ocean, ending several hundred miles west of Ireland 5 hours, 29 minutes and Will watch from the desert. Allegheny’s Dr. H. D. Curtis chose Western Nevada. 55 seconds after it began, 10,000 miles away, and having made a speed record which even the hmmt airplanes cannot approach—33 miles a minute. BwAUSl the shadow just barely reaches the earth’s surface, it is very small at best, and the path of totality is very narrow—only about half a mile wide, instead of the width of & hundred or more miles' that astronomers fre- quently enjoy. It will also be very brief. - ‘i THE SUN -APRIL 28,1930 The moon’s shadow, drawn to a fine point, will pass along a line across Western United States as indicated en this map. ¢ With an airplane, a very slight advantage im time can be obtained for two reasons. The higher you are above the earth’s surface, the larger is the shadow. Also the airplane can fly along with the shadow, thus prolonging the time a bit. Astronomers will fiy for this eclipse, in airplanes furnished by the Army Air Service, and may succeed where the ground forces fail. Photographs of the eclipsed sun will be made from the airplane, but surprisingly enough, some of the cameras will be turned away from the sun and pointed at the ground. With these an effort will be made to photograph the moon’s shadow as it sweeps across the earth. Such photographs will make possible a very accurate determination of the position of the moon at that time and help in the solution of one of the most difficult of astronomical problems— the exact way in which the moon moves. This will not be the first time that aerial observations of an pse have been made. At the historic New England eclipse in January, 1925, naval astronomers made use of the airship Los Angeles for an observation, while still other observations were made from airplanes. Last year the Naval Observatory sent an expedition to the Philippines to observe an eclipse. Most of the photographs were made from the ground, in Iloilo, but these were supplemented by aerigl photographs. Three Navy planes took part in the experi- ment, each manned with a crew of three: Pllot, navigator and photographer. A specially rigged camera was used, 11 feet long, with which a total of 80 photographs were made at altitudes of 5,500 to 10,000 feet. A series of moving ple- ture photographs were also made, at intervals of five seconds from the beginning of the eclipse to the end. The men in the cockpit of the planes re- turned with an awesome story of the glory of the heavens. “For an hour the nose of the heavy plane pointed upward and we mounted nearer the sun,” one of the aviators said. “We cruised along, always turning back to face the sun as he glared down at us from his western position at an angle of 45 degrees. An odd light slowly enshrouded the heavens and as the sun beamed less intensely the atmosphere grew eerie and unnatural. The pilot shouted something and I knew that the eclipse was about to begin. “An extraordinary haze of violet gently hov- ered over the entire world, and as an irreg- ularly shaped dark object grew more and more apparent, the lavender coloring and heavy at- mosphere of every imaginable shade of trans- parent orchid to deep purples cloaked the skies, At the spot where the sun had recently shown so brilliantly was a burning hot yellow corona bordering the moon, which was now in the midst of the eclipse. “This intense golden halo rimmes the jet black sphere with a daszling light. It was a sight never to be forgotten. The motor had idled and we coasted toward this strange and glamorous extravagance for all the world Hke & voyage to some imaginative land. “Far below, the earth had put on a heavy purple of coloring and scattered here and there along the plains and in the hills were tiny jets of fire. The rivers and weaving streams pierced the gloom and from their lum- inous glow their courses were easily traced. Such a panorama man had never seen be- fore. It cannot be successfully described. The sun and moon seemed quite close. The whole phenomena somehow looked like a queerly ‘de- - signed lantern hanging against-a silken curtaim. - I know I held my breath.” Rae