GALILEO AND HIS JUDGES. 143 



But when you dethrone an ancient theory which 

 has for centuries held an almost undisputed sway, 

 you have to reconsider your whole position, and 

 compromises such as that of Tycho are not always 

 adequate to the emergency. 



But these considerations formed only a part of 

 this complicated controversy. The anti-Copernicans 

 of the seventeenth century would not even admit 

 the revolution of the Earth on its own axis, and 

 were consequently forced to hold that the whole 

 of the heavenly bodies were carried round this our 

 globe in twenty-four hours. In ancient times, when 

 men knew little or nothing of the sizes and distances 

 of the Sun, the planets, or the stars, such a belief 

 was quite reasonable and natural ; they thought the 

 stars were set as if they were jewels in a hollow 

 sphere, which was turned round its poles each day. 

 But the astronomers of Galileo's day knew some- 

 thing far more accurate than this ; he himself, as we 

 observed in the Dialogue, greatly under-estimated 

 the distance and the size of the Sun, and had but 

 a very imperfect idea of the enormous interval that 

 separates us from the stars ; yet he evidently perceived 

 the improbability of all these vast and remote bodies 

 revolving with an almost inconceivable velocity round 

 the Earth every twenty-four hours. And what must 

 be OUT judgment on such a subject, seeing that we 

 know the Sun's mean distance to be about 92,000,000 

 miles, more than nineteen times as much as Galileo's 

 estimate ? And yet some of the planets are farther 



