GALILEO GALILEI 3» 



Galileo re-invented it immediately he heard of it, and himself 

 made far better telescopes than those which were soon ob- 

 tainable everywhere, even at fairs. He later on also succeeded 

 in making the transition to the microscope. 



Already in the year 1609, Galileo directed his telescope 

 first towards the moon, and recognised, in the mountains 

 casting their shadows into the valleys, the evident similarity 

 of this heavenly body with the earth. He then discovered 

 the almost incredible multitude of fixed stars which had 

 hitherto remained hidden from the naked eye, and which, 

 when seen through the telescope, thickly cover many parts 

 of the heavens; the luminous cloud of the Milky Way was 

 resolved into vast numbers of stars. The enormous extent 

 of celestial space, already recognised by Copernicus and 

 Tycho, now appears to be occupied, to an extent hitherto 

 undreamed of, by suns. But still more than by these in- 

 numerable multitudes, Galileo was struck by some stars only 

 recognisable through the telescope, which he found near the 

 planet Jupiter : the four moons of Jupiter. He saw them 

 for the first time in the night of the 17th January, 1610. 

 On the following night he recognised them correctly as moons 

 of Jupiter, since they had changed their position markedly, 

 and nevertheless had remained in one line close to the eclip- 

 tic; obviously they were revolving around Jupiter. A secret 

 of the heavens had been revealed. The earth with its moon 

 suddenly appeared quite clearly as having no other rank in 

 cosmic space than that also held by the planet Jupiter; each 

 planet had an equal claim to be regarded as a world in itself, 

 while at the same time it revolved around the sun. The 

 mode of motion ascribed by Copernicus to the earth moon, 

 its revolution around the earth combined with the latter's 

 revolution around the sun, without any means of support, 

 had now to be recognised as possible, however difficult it 

 might be to understand. For anyone who wished eould 

 look through a telescope at night and see the reality of such 



