IMMENSITIES OF TIME AND SPACE ' 



By A. ViuB^RT Douglas, M. B. E., M. Sc. 



Within the last twelve months three workers in the realms of 

 mathematical astronomy and cosmogony have bronght their re- 

 searches to conclusions of tremendous importance and widespread 

 interest. So closely are their problems interwoven that it may prove 

 stimulating to consider in some detail the aim of each investigation, 

 the line of argument, and the outstanding results thus far achieved. 



STAR'S MASS AND LUMINOSITY 



Last year there was given to the Royal Astronomical Society by 

 Prof. A. S. Eddington, F. R. S., a paper which has aroused great in- 

 terest among astronomers 

 the world over. For many 

 years Professor Eddington 

 has been investigating the 

 radiative properties of a 

 giant star — that is, a star 

 of gigantic size and low 

 density, so low that it could 

 be considered as obeying 

 Avhat in physics are knoAvn 

 as the " perfect gas " laws. 

 These investigations led 

 him to the conclusion that 

 the total luminosity of such a star depended chiefly upon its 

 mass and temperature, being almost uninfluenced by other fac- 

 tors. To test the validitj^ of this formula relating luminosity 

 to mass, he first evaluated the constants involved in it from the 

 knowm values of mass and luminosity of the bright star Capella. 

 He then plotted his relation as shown in the accompanying graph 

 by the curved line. Next he collected all the available data from 

 every possible source, giving both the masses and luminosities of 

 stars and these he plotted individually on his graph. Their close 



0-1- 0-6 0-8 O 0-2 0-4- 6 0-i 

 Logarithm of Afess 



10 1-2 



Fig. 1. — Diagram of hiniiuosity — mass relation. 



1 Reprinted by permission from Discovery, Vol. VI, No. 68, August, 1925. 



147 



