96 GALILEO AND HIS JUDGES, 



thesis was of the nature of a compromise, and it has- 

 been said that Tycho was led to it by his interpreta- 

 tion of Scripture rather than of Nature ; yet he was 

 one of the best astronomers and best observers of 

 his age, and had Kepler for one of his pupils. He 

 had a reason, too, for rejecting Copernicanism which 

 in his time seemed to have considerable weight, 

 namely, the incredible distances at which the fixed 

 stars must be supposed to be placed if the theory 

 were true, since no sensible motion could be detected 

 among them apparent motion, that is such as 

 would result from the annual motion of the Earth 

 if the stars were at any distance approaching to that 

 of the planets. We know now how futile this objec- 

 tion is, but in that age there was an idea that Nature 

 could never allow of such a waste of space as is 

 implied in these vast distances. If Tycho had lived 

 longer, we may well doubt whether he would have 

 adhered to his system. Kepler saw its weakness, and 

 was the first to discover the true nature of the curves 

 which both the Earth and the planets describe in their 

 respective orbits ; and this, although he did not know 

 the first law of motion. His books, published in 

 1619 and 1622, stated not only the elliptic form of 

 the orbits, which no one previously had found out, 

 but also the important law connecting the distances 

 of the planets with their periods of revolution. 



It is necessary to bear in mind how gradually these 

 various items of knowledge dawned upon the scien- 

 tific world, and how imperfect was the state in which 



