CH. XI. ASTRONOMICAL DISCOVERIES. 89 



which ordinary people could understand. The planets had 

 till now been looked upon simply as lights in the sky moving 

 round the earth ; but now it could not be doubted that 

 Jupiter at least was something more than this, for he had a 

 system like our own, with four moons, to give him light by 

 night, instead of one. Many people were terribly alarmed 

 at the fact that our little earth should not be the central 

 body in the heavens, because they had hitherto believed 

 that the sun, moon, and stars had all been created for our 

 use only, and this could scarcely be if our world was only 

 one of many bodies moving round the sun. Some astro- 

 nomers would not believe that Galileo had really seen 

 Jupiter's moons ; one was even so foolish as to refuse to 

 look through the telescope, for fear he should see them. 



Phases of Venus. Galileo, however, now felt sure 

 that his new instrument would help him to read wonderful 

 truths in the beautiful universe of God, and he threw his 

 whole heart and soul into this grand study. It was not long 

 before he discovered another proof that the planets move 

 round the sun and not round the earth. When he first saw 

 the planet Venus through the telescope she was round, but 

 happening to look at her one day, when she was almost be- 

 tween the earth and the sun, he saw her in the form of a 

 crescent like a new moon. Struck by this, he continued to 

 observe her night after night till she had made the whole 

 journey round the sun, and he proved to himself that she 

 went through the same changes as our moon, from a crescent 

 shape to a full round face. This was just what she would 

 be expected to do if she and we both travelled round the 

 sun, whereas if she trarelled round some fixed point between 

 the earth and the sun, as was supposed by the Ptolemaic 

 system, she could not exhibit these phases. Thus for the 

 second time Galileo proved that the Copernican theory was 

 the true one. 



