NICOLAUS COPERNICUS 25 



earth, although it has been accepted and believed by almost all, that 

 the earth occupies the middle of the universe. But if one should sup- 

 pose that the earth is not at the center of the universe, that, however, 

 the distance between the two is not great enough to be measured on 

 the orbits of the fixed stars, but would be noticeable and perceptible on 

 the orbit of the sun or of the planets : and if one was further of the 

 opinion that the movements of the planets appeared to be irregular as 

 if they were governed by a center other than the earth, then such an 

 one could perhaps have given the true reasons for the apparently ir- 

 regular movement. For since the planets appear now nearer and now 

 farther from the earth, this shows necessarily that the center of their 

 revolutions is not the center of the earth : although it does not settle 

 whether the earth increases and decreases the distance from them or 

 they their distance from the earth. 



REFUTATION OF THE ARGUMENT OF THE ANCIENTS THAT THE 

 EARTH REMAINS STILL IN THE MIDDLE OF THE UNIVERSE, 



AS IF IT WERE ITS CENTER 



From this and similar reasons it is supposed that the earth rests 

 at the center of the universe and that there is no doubt of the fact. 

 But if one believed that the earth revolved, he would certainly be of 

 the opinion that this movement was natural and not arbitrary. For 

 whatever is in accord with nature produces results which are the oppo- 

 site of those produced by force. Things upon which force or an out- 

 side power has acted, must be injured and cannot long endure: what 

 happens by nature, however, preserves itself well and exists in the best 

 condition. So Ptolemy feared without good reason that the earth and 

 all earthly objects subject to the revolution would be destroyed by the 

 act of nature, since this latter is opposed to artificial acts, or to what 

 is produced by the human spirit. But why did not he fear the same, 

 and in a much higher degree, of the universe, whose motion must be 

 as much more rapid as the heavens are greater than the earth? Or 

 has the heaven become so immense because it has been driven outward 

 from the center by the inconceivable power of the revolution ; while if 

 it stood still, on the contrary, it would collapse and fall together ? But 

 surely if this is the case the extent of the heavens would increase infi- 

 nitely. For the more it is driven higher by the outward force of the 



