A HISTORY OF SCIENCE 



There seems, however, to be no direct evidence for 

 this opinion. It has been thought significant that 

 Copernicus addressed his work to the pope. It is, 

 of course, quite conceivable that the aged astronomer 

 might wish by this means to demonstrate that he 

 wrote in no spirit of hostility to the church. His 

 address to the pope might have been considered as a 

 desirable shield precisely because the author recog- 

 nized that his work must needs meet with ecclesias- 

 tical criticism. Be that as it may, Copernicus was 

 removed by death from the danger of attack, and it 

 remained for his disciples of a later generation to run 

 the gauntlet of criticism and suffer the charges of 

 heresy. 



The work of Copernicus, published thus in the year 

 1543 at Nuremberg, bears the title De Orbium Cosles- 

 tium Revolutionibus . 



It is not necessary to go into details as tojthe cos- 

 mological system which Copernicus advocated, since it 

 is familiar to every r oneT"'In a word, he supposed the 

 sun to be the centre of all the planetary motions, the 

 earth taking its place among the other planets, the list 

 of which, as known at that time, comprised-Mercury, 

 Venus, the Earth, Mars, Jupiter, and Saturn. The 

 fixed stars were alleged to be stationary, and it was 

 necessary to suppose that they are almost infinitely 

 distant, inasmuch as they showed to the observers of 

 that time no parallax; that is to say, they preserved 

 the same apparent position when viewed from the op- 

 posite points of the earth's orbit. 



But let us allow Copernicus to speak for himself re- 

 garding his system, His exposition is full of interest. 



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