1 8 OUR PHYSICAL WORLD 



these distant suns we call stars are very much larger than 

 ours. Betelgeuse in the constellation Orion (p. 33) has been 

 recently measured and found to have a diameter 300 times that 

 of our sun, yet it is so far away it is not as brilliant as Sirius, 

 which, though only thirty times as large as our sun, is but eight 

 and one-half light-years away and outshines Betelgeuse. 



There are only about twenty-five stars in the list of the old 

 first-magnitude stars, so it is not very difficult to learn to locate 

 and recognize these. They were all known to the ancients and 

 came down to us with ancient names. 



Undoubtedly the stars served early man as a means of keep- 

 ing his directions when traveling by night, as they still similarly 

 serve us. The stars, too, were supposed to mark important 

 events. Thus, Sirius, the Dog Star, when it received its name, rose 

 just before the sun, at the time of the year that was intensely hot, 

 when dogs went mad, and so it appeared as a warning of the 

 approach of the season that must have had terrors for the early 

 hunter and shepherd peoples among whom dogs were likely as 

 abundant and as ill kept as they are today in the East. 



Probably, too, important events in the history of the race 

 were connected with groups of stars, as well as with individual 

 stars, when such groups were particularly brilliant or in com- 

 manding positions at the time such events occurred, just as the 

 birth of Christ was connected with an unusual astronomical 

 phenomenon, the appearance of the "Star in the East." Many 

 of the star groups or constellations are still commemorative of 

 events that once had great historical significance, but the stories 

 have been so altered by constant repetition, as they have been 

 told and retold, that they come to us merely as legends, or myths. 

 Many of these legends have been transmitted from the earlier 

 primitive peoples through the fervid imaginations of the Greeks, 

 and so the heavens have come to be "a pictured scroll of Greek 

 mythology." One needs a large measure of this imaginative 

 power to see in the star -groups any likeness to the things the 

 ancients figured in their maps of the sky. 



