A HISTORY OF SCIENCE 



the theory. We shall gain a true gauge as to this 

 if we assume that the greater number of important 

 thinkers had accepted the heliocentric doctrine before 

 the middle of the seventeenth century, and that before 

 the close of that century the old Ptolemaic idea had 

 been quite abandoned. A wonderful revolution in 

 man's estimate of the universe had thus been effected 

 within about two centuries after the birth of Copernicus. 



