202 THE WORLD MACHINE 



Galileo had also looked upon the face of the moon, found it 

 full of mountains and valleys and volcanoes, and not at all the 

 smooth, bare, and crystal surface that Aristotle, again, had 

 taught. He had explained the appearance of " the old moon 

 in the new moon's arms " as due to earthshine ; he made the 

 earth a planet shining like the rest. He turned upon the Milky 

 Way, and showed that its nebulous haze was in reality a crowd 

 of stars, so thickly sown and individually so faint as to give 

 the appearance of a gossamer cloud. Then he saw that Saturn 

 appeared to consist of three parts ; he had the first sight of 

 the famous rings. The old Aristotelian world was crumbling 

 in his hands. 



Then came the final blow. It followed from Coppernicus' 

 theory that Venus and Mercury, could we see them closely 

 enough, would show phases like the moon, though Coppernicus 

 himself did not make such a prediction, as is so often said in 

 the books. Galileo with his glass saw Venus grow from a 

 crescent to its full splendour and then back again. His dis- 

 covery of the satellites of Jupiter had shown that other planets 

 might have moons revolving round about them, just as has 

 the earth. The phases of Venus was almost the last stone 

 required in the Coppernican structure. Kepler is overjoyed ; 

 he longs for a telescope with which to see it all himself. 



But for the last and final proof Galileo searches long and in 

 vain. When he turns his telescope to the stars he is astonished 

 to find that they appear to grow no larger. Their distance from 

 the sun must be unthinkably immense. What is more, when 

 he tries to discover if any among them change their apparent 

 position as they should, seen from one side of the earth's orbit 

 and from the other that is to say, in the spring and in the 

 fall he can detect no motion. He cannot even find any parallax 

 for the sun. The answer that Aristarchus made to objectors 

 to his theory must remain the answer of Galileo and the Cop- 

 pernicans of that day ; but it is hard to believe. Try a moment 

 to grasp it all now. In the sky is a body so vast that it has 

 an appreciable visual diameter a huge disk, in fact and yet 

 it is so distant that from two distant points on the earth it 

 will show no parallactic shift of position, even with a telescope, 

 a,t least any such a telescope as Galileo could contrive. Yet 

 vast as is its distance from the earth, the stars themselves are 

 so remote that even this immeasurable distance becomes a point. 



