SCRIBNER'S FICTION NUMBER John James Boyd J. Edward [August] His serial, To LET, reaches a climax in this number. This novel is the last of "The Forsyte Saga." NANCY is a new kind of dog story, one of real vivacity and fascination. Every one who loves a dog will love this story. ARGIVE HELEN AND THE LITTLE MAID OF TYRE is an up-todate version in modern colloquial style of the classic legend. MASTERSON ANd_the_Spirit WORLD is a tale of the amusing family who ran "The Parthenon Freeze" and "Au Bonheur des Coeds." W. E. Hill, the famous cartoonist, illustrates the story. The author of "Cynthia and the Crooked Streets," tells in this number a striking flying adventure in the life of a meek professor in a boys' school in England. It is entitled THE WINGED INTErlude. THE SOUND OF A VOICE is an unusual story by a new writer. It is a romantic love story, vivid in its characters and dramatic in its conclusion... OUT OF THE HURRICANE is a sea story full of action and told with love of the sea, and from full knowledge of the management of boats. Other Features in This Number R FARM, by William Henry Shelton, cribes sympathetically the life on an farm in Western New York nearly hty years ago. It furnishes a conial subject for illustration by A. B. Tost. route. The trip was taken by two young women. Sara Teasdale, one of the leading lyric poets in this country, contributes four LOVE SONGS. Frank Linderman, author of "Indian Why Stories," contributes a group of Montana poems. They are appropriately accompanied with four full-page paintings by C. M. Russell, a Montana artist of distinction. Mary Raymond Shipman Andrews leads the number with an outdoor poem, PAX VOBISCUM. The Field of Art, with reproductions of drawings from an old sketch-book of Barye's, The Point of View, and "The Financial Situation," with a pertinent discussion of present-day conditions, by Alexander Dana Noyes, complete the number. THIS IS THE THIRTY-THIRD ANNUAL FICTION NUMBER OF SCRIBNER'S MAGAZINE SCRIBNERS MAGAZINE VOL. LXX JULY, 1921 NO. 1 GIANT STARS BY GEORGE ELLERY HALE Director of the Mount Wilson Observatory of the Carnegie Institution of Washington ILLUSTRATIONS FROM PHOTOGRAPHS TAKEN AT THE MOUNT WILSON OBSERVATORY UR ancestral sun, as pictured by Laplace, originally extended in a state of luminous vapor beyond the boundaries of the solar system. Rotating upon its axis, it slowly contracted through loss of heat by radiation, leaving behind it portions of its mass, which condensed to form the planets. Still gaseous, though now denser than water, it continues to pour out the heat on which our existence depends as it shrinks imperceptibly toward its ultimate condition of a cold and darkened globe. volume is more than a million times that of the earth. But what of the stars, proved by the spectroscope to be self-luminous, intensely hot, and formed of the same chemical elements that constitute the sun and the earth? Are they comparable in size with the sun? Do they occur in all stages of development, from infancy to old age? And if such stages can be detected, do they afford indications of the gradual diminution in volume which Laplace imagined the sun to experience? Prior to the application of the powerful new engine of research described in Laplace's hypothesis has been sub- this article we have had no means of jected in recent years to much criticism, measuring the diameters of the stars. and there is good reason to doubt whether We have measured their distances and his description of the mode of evolution their motions, determined their chemical of our solar system is correct in every composition, and obtained undeniable particular. All critics agree, however, evidence of progressive development, but that the sun was once enormously larger even in the most powerful telescopes their than it now is, and that the planets orig- images are so minute that they appear as inally formed part of its distended mass. points rather than as disks. In fact, the Even in its present diminished state, larger the telescope and the more perfect the sun is huge beyond easy conception. the atmospheric conditions at the obOur own earth, though so minute a frag- server's command, the smaller do these ment of the primeval sun, is nevertheless images appear. On the photographic so large that some parts of its surface have plate, it is true, the stars are recorded as not yet been explored. Seen beside the measurable disks, but these are due to sun, by an observer on one of the planets, the spreading of the light from their the earth would appear as an insignificant bright point-like images, and their diamspeck, which could be swallowed with eters increase as the exposure time is proease by the whirling vortex of a sun-spot. longed. From the images of the brighter If the sun were hollow, with the earth at stars rays of light project in straight lines, its centre, the moon, though 240,000 miles but these also are instrumental phenomfrom us, would have room and to spare ena, due to diffraction of light by the steel in which to describe its orbit, for the sun bars that support the small mirror in the is 866,000 miles in diameter, so that its tube of reflecting telescopes. In a word, Copyrighted in 1921 in United States, Canada, and Great Britain, by Charles Scribner's Sons. Printed in New York. All rights reserved. 4 the stars are so remote that the largest How, then, may we hope to measure The instrument in question, known as the interferometer, had previously yielded a remarkable series of results when applied in its various forms to the solution of fundamental problems. To mention only a few of those that have helped to establish Michelson's fame, we may recall that our exact knowledge of the length of the international metre at Sèvres, the world's standard of measurement, was obtained by him with an interferometer in terms of the invariable length of light-waves. A different form of interferometer has more recently enabled him to measure the minute tides within the solid body of the earth-not the great tides of the ocean, but the slight deformations of the earth's body, which is as rigid as steel, that are caused by the varying attractions of the sun and moon. Finally, to mention only one more case, it was the Michelson-Morley experiment, made years ago with still another form of interferometer, that yielded the basic idea from which the theory of relativity was developed by Lorentz and Einstein. The history of the method of measuring star diameters is a very curious one, showing how the most promising opportunities for scientific progress may lie un used for decades. The fundamental principle of the device was first suggested by the great French physicist Fizeau in 1868. In 1874 the theory was developed by the served interference fringes given by a French astronomer Stéphan, who oblarge number of stars, and rightly concluded that their angular diameters must be much smaller than 0.158 seconds of arc, the smallest measurable with his instrument. In 1890 Michelson, unaware of the earlier work, published in the Philosophical Magazine a complete description of an interferometer capable of determining with surprising accuracy the distance between the components of double stars so close together that no telescope can separate them. He also showed how the same principle could be applied to the measurement of star diameters if a sufficiently large interferometer could be built for this purpose, and developed the theory much more completely than Stéphan had done. A year later he measured the diameters of Jupiter's sateltory. But nearly thirty years elapsed lites by this means at the Lick Observabefore the next step was taken. Two causes have doubtless contributed to this delay. Both theory and experiment have demonstrated the extreme sensitiveness of the "interference fringes," on the observation of which the method depends, and it was generally supposed by astronomers that disturbances in the earth's atmosphere would prevent them from being clearly seen with large telescopes. Furthermore, a very large interferometer, too large to be carried by any existing telescope, was required for the star-diameter work, though close double stars could have been easily studied by this device with several of the large telescopes of the early nineties. But whatever the reasons, a powerful method of research lay unused. inch telescope of the Mount Wilson ObThe approaching completion of the 100servatory* led me to suggest to Professor Michelson, before the United States entered the war, that the method be thoroughly tested under the favorable fornia. He was at that time at work on atmospheric conditions of Southern Calito determine whether atmospheric disa special form of interferometer, designed * See SCRIBNER'S MAGAZINE for October, 1920. |