NATURAL PHILOSOPHY — SWANN 245 



Astronomy, the most ancient of the sciences, has always occupied 

 a place in the forefront of the imagination of the scientist and the 

 layman alike. With the motions of the planets coordinated by Kep- 

 ler, and molded into a beautiful scheme of physical law by Newton 

 300 years ago, there seemed but little more that man could expect to 

 discover. The growth of the science of optics soon provided a tool 

 wherewith to explore farther, however. Laboratory studies of the 

 nature of the light emitted by incandescent solids and gases soon 

 provided a means of determining much concerning tlie heavenly 

 bodies by a study of the light which they emit. Stars which are so 

 far away that their light, traveling toward us at the rate of 186,000 

 miles per second, takes thousands of years to reach us, may move 

 with great velocity without that velocity making itself apparent by 

 direct observation. A study of their light has enabled us to deter- 

 mine their speed in very much the same way that we could determine 

 the speed of a train by noting how much the pitch of its whistle 

 is altered by the motion. 



The stars are so far away that even in our most powerful telescopes 

 they appear but as points in spite of their great size; but by drawing 

 in greater detail upon our knowledge of the way in which light comes 

 to us and of the effect of the size of the emitting body on the cliar- 

 acter of the light, Professor Michelson, at an age when most men are 

 content to rest upon their laurels, performed one of the most bril- 

 liant feats of a lifetime of masterly achievements in measuring the 

 diameter of one of these stars, a feat equivalent to measuring the 

 diameter of a penny at a distance of a thousand miles. 



Strange as it may seem that we can learn so much about the stars 

 which are so far away, the last few years have enhanced still further 

 the wonder of it all. For the knowledge which we have gained about 

 matter by experiment in the laboratory has found a most remark- 

 able field of application in enabling us to understand the condi- 

 tions which must prevail in the stars; and, these stars by their 

 peculiar characteristics of large size, high temperature, high density, 

 etc., have provided us with conditions to test out conclusions such as 

 we could never have hoped to attain in the hvboratory. A gas com- 

 pressed to a density eight thousand times that of steel is but a figment 

 of the imagination in the laboratory, yet of such stuff is the com- 

 panion of Sirius made. Temperatures of 40,000,000"^ correspond to 

 things ten thousand times as hot as any temperatures we find on 

 earth, yet nature has realized such temperatures in some of the stars. 

 And so the stars, far from being tilings through which we dare 

 hope to learn but little have, by their exceptional condition, served 

 to provide us not only with a very fascinating story of their own 



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