THE NEW COSMOLOGY 



1564. The day of his birth is doubly memorable, 

 since on the same day the greatest Italian of the 

 preceding epoch, Michael Angelo, breathed his last. 

 Persons fond of symbolism have found in the coinci- 

 dence a forecast of the transit from the artistic to the 

 scientific epoch of the later Renaissance. Galileo came 

 of an impoverished noble family. He was educated 

 for the profession of medicine, but did not progress far 

 before his natural proclivities directed him towards 

 the physical sciences. Meeting with opposition in 

 Pisa, he early accepted a call to the chair of natural 

 philosophy in the University of Padua, and later in 

 life he made his home at Florence. The mechanical 

 and physical discoveries of Galileo will claim our 

 attention in another chapter. Our present concern is 

 with his contribution to the Copernican theory. 



Galileo himself records in a letter to Kepler that he 



became a convert to this theory at an early day. He 



was not enabled, however, to make any marked 



contribution to the subject, beyond the influence of 



his general teachings, until about the year 1610. The 



brilliant contributions which he made were due largely 



to a single discovery namely, that of the telescope. 



Hitherto the astronomical observations had been made 



with the unaided eye. Glass lenses had been known 



since the thirteenth century, but, until now, no one 



had thought of their possible use as aids to distant 



vision. The question of priority of discovery has 



never been settled. It is admitted, however, that the 



chief honors belong to the opticians of the Netherlands. 



As early as the year 1590 the Dutch optician 



Zacharias Jensen placed a concave and a convex 



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