SPIRAL NEBULAE AND THE STRUCTURE OF SPACE ^ 



By C. WiRTz 

 University Observatory, Kiel 



1. The inquiry into the structure of space lies within the province 

 of astronomy. For this purpose observation will give us the position 

 of numerous physical points which must serve as the skeleton upon 

 which we model our conception. Observation gives us knowledge of 

 the motions of the heavenly bodies. The orbits derived from these 

 motions should serve as the basis for some conclusions as to the 

 character of the space in which these bodies are imbedded. Several 

 decades ago the distances measured by astronomy out into the world 

 of the stars were too small to be expected to show any divergencies of 

 structure from ordinary Euclidean conceptions. Within the rela- 

 tively small solar system all motions take place so accurately in 

 accordance with the laws of Newton and Euclidean geometry that 

 no modifications are necessary. 



This is remarkable and comforting. In the solar system the ap- 

 parent movements are rapid and great with reference to the lapse 

 of time during which we may make measures. Accordingly, the 

 numerous complexities of the motions have been recognized and 

 explained. On the other hand with the stars the changes of position 

 are so slow that observations for 2,000 years show no divergences of 

 their paths from straight, uniform motion. The stars of the heavens 

 behave to us as would^ our planetary system to an observer living 

 only a few seconds; that is, for such an observer the planets would 

 show no deviation from a uniform rectilinear motion. Yet we must 

 not push the analogy further for he could from such observations 

 correctly construct the plan of the solar system. 



In every way we become convinced that the dimensions of our 

 solar system with its known structure and rapid motions are too 

 restricted to help us in our problem of the structure of space. In- 



> Reprinted (by special permission of the director of Sclentia) from the Issue of Novem- 

 ber, 1925, of Scientia. International Review of scientific synthesis, edited by Eugenio 

 Rignano, published by eight publishers : Williams & Wilkins Co., Baltimore ; Williams & 

 Norgate, London ; Felix Alcau, Paris ; Nicola Zanlchelli, Bologna ; Akad, Verlagsgesell- 

 schaft m. b. II., Leipzig ; Ruiz Hermanos, Madrid ; Renascenca Tortiguesa, Porto ; The 

 Maruzen Co., Tokyo. 



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