26 CLASSICS OF MODERN SCIENCE 

 movement, so much the more rapid will the movement become, because 

 of the ever increasing circle which must be traversed in 24 hours ; and 

 conversely if the movement grows the immensity of the heavens 

 grows. So the velocity would increase the size and the size would 

 increase the velocity unendingly. According to the physical law that 

 the endless cannot wear away nor in any way move, the heavens must 

 necessarily stand still. 



But it is said that beyond the sky no body, no place, no vacant space, 

 in fact nothing at all exists ; then it is strange that some thing should 

 be enclosed by nothing. But if the heaven is endless and is bounded 

 only by the inner hollow, perhaps this establishes all the more clearly 

 the fact that there is nothing outside the heavens, because everything 

 is within it, but the heaven must then remain unmoved. The highest 

 proof on which one supports the finite character of the universe is its 

 movement. But whether the universe is endless or limited we will 

 leave to the physiologues ; this remains sure for us that the earth en- 

 closed between the poles, is bounded by a spherical surface. Why 

 therefore should we not take the position of ascribing to a movement 

 conformable to its nature and corresponding to its form, rather than 

 suppose that the whole universe whose limits are not and cannot be 

 known moves ? and why will we not recognize that the appearance of 

 a daily revolution belongs to the heavens, but the actuality to the earth ; 

 and that the relation is similar to that of which one says : "We run 

 out of the harbor, the lands and cities retreat from us." Because if a 

 ship sails along quietly, everything outside of it appears to those on 

 board as if it moved with the motion of the boat, and the boatman 

 thinks that the boat with all on board is standing still, this same thing 

 may hold without doubt of the motion of the earth, and it may seem 

 as if the whole universe revolved. What shall we say, however, of 

 the clouds and other things floating, falling or raising in the air — 

 except that not only does the earth move with the watery elements 

 belonging with it, but also a large part of the atmosphere, and what- 

 ever else is in any way connected with the earth; whether it is be- 

 cause the air immediately touching the earth has the same nature as 

 the earth, or that the motion has become imparted to the atmosphere. 

 A like astonishment must be felt if that highest region of the air be 

 supposed to follow the heavenly motion, as shown by those suddenly, 

 appearing stars which the Greeks call comets or bearded stars, which 



