ORIGIN OF THE WORLD 



nebulae, we must not overlook the fact that an alter- 

 native explanation has been put forward in recent 

 years. This is Professor Svante Arrhenius' theory 

 that the universe is full of "cosmical dust," thrown 

 out under influence of the pressure of radiant energy 

 from the incandescent stars. The electrified particles 

 of world stuff driven off from the suns are supposed 

 to collide in space and build up tiny meteorites, which 

 ultimately aggregate under the influence of gravita- 

 tion. Myriads of these meteorites fall into the earth's 

 atmosphere; sundry swarms of them make up the 

 wisps of matter we call comets ; still greater swarms, 

 out in sidereal space, build up the nebulae. 



According to Arrhenius the nebulae thus construct- 

 ed are cold with the frigidity of empty space, and owe 

 their luminosity to the impact of electrified particles, 

 causing a glow like that of the rarefied matter of a 

 vacuum tube in the laboratory. 



It is quite possible that both theories of nebular 

 origins are correct. The spectroscope shows that 

 nebulae are of two quite different types. Many of the 

 filmy ones give a bright line spectrum characteristic 

 of incandescent gases; whereas the spiral nebulae re- 

 veal a mixed spectrum, partly of condensed, and 

 partly of gaseous matter, confirming thus their tele- 

 scopic appearance. 



THE ORIGIN OF WORLD-SYSTEMS 



But whatever the origin of the nebulae, there is no 

 difference of opinion as to the destiny of some at 

 least of them. The mass of meteoric matter of which N 

 they are composed will ultimately condense to form 



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