COSMIC PHILOSOPHY 



ber evening, your attention is arrested by a 

 bright but suddenly vanishing track of light 

 across the sky, which you recognize as the ap- 

 pearance of a " falling star." In doubt, per- 

 haps, as to the true explanation of this phenome- 

 non, you appeal to some astronomer, who tells 

 you that a zone of planetary matter encircles 

 the sun ; that the course of this zone, lying 

 near the course of the earth's orbit and not 

 being concentric with it, must intersect it at 

 sundry points ; and that when, at certain sea- 

 sons of the year, such intersection occurs, the 

 gravitative force of the earth pulls down some 

 of the fragments constituting this zone, and 

 unites them with its own mass. That is to say, 

 he ranks the phenomenon which is to be ex- 

 plained along with the more familiar phenomena 

 of heavy bodies which circulate about a vast cen- 

 tral mass, and which, by their gravitative power, 

 draw to themselves whatsoever comes within a 

 certain distance of them. And this you feel to 

 be a perfectly satisfactory explanation. Similarly, 

 when Newton explained the manner in which 

 these planets are kept revolving about the sun, 

 he had recourse to the hypotheses of gravita- 

 tion and tangential momentum. By the former 

 he classified the unknown force which keeps 

 the moon from flying away from the earth along 

 with the famihar force which causes unsupported 

 terrestrial bodies to fall toward the earth's cen- 



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