32 GREAT MEN OF SCIENCE 



motion; and not merely of one, but actually of four moons, 

 in the case of Jupiter. At the same time the most definite 

 evidence was obtained that there are heavenly bodies moving 

 in closed paths which have not the earth for their centre. 

 Surely never before, and but seldom since, has a single person 

 been privileged to experience such a wealth of completely 

 new observation and thought as Galileo must have done at 

 the time of his discoveries with the telescope and their 

 examination in detail. He himself writes to the Florentine 

 Court: 'I am filled with infinite astonishment and also in- 

 finite gratitude to God that it has pleased Him to make me 

 alone the first observer of such wonderful things, which have 

 been hidden in all past centuries.' 



These discoveries also led to the fulfilment of Galileo's 

 wish for a position in which he would not be pledged to any 

 definite lectures: it was offered to him by Prince Cosimo of 

 Medici in Florence, and he lived there from September 1610 

 onwards. His activity as a lecturer in Padua could give him 

 no more permanent satisfaction than his earlier work of the 

 kind in Pisa; at all universities of that time it was absolutely 

 necessary to teach Aristotle. Galileo appears to have de- 

 veloped a certain amount of humour in the process, but it 

 would be wrong to assume that he lectured on his own studies 

 and discoveries. This would have aroused great opposition; 

 for even Copernicus was still looked upon as someone to be 

 laughed at and hissed off the stage. The most prominent 

 professors of philosophy and physics at the Italian universi- 

 ties uttered violent protests against the Sidereus nuntius 

 ('The Sidereal Messenger') in which Galileo published in 

 print his new discoveries; they confuted what had been seen 

 through the telescope by means of logic; wild and ill-founded 

 contradictions, spread irresponsibly, formed the main ele- 

 ment. Galileo, to meet this, undertook on the one hand the 

 construction of good telescopes in large numbers, and sent 

 them to influential personalities for their use; on the other 



