CH. xii. THE RUDOLPH1NE TABLES. 93 



CHAPTER XII. 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED). 



Kepler the German Astronomer His discoveries in Optics His three 

 laws Comparison of the labours of Tycho, Galileo, and Kepler. 



Kepler, 1571-1630. While Galileo was occupied in 

 discovering unknown worlds with, his telescope, another 

 famous astronomer, named Johannes Kepler, was working 

 out three grand laws about the movements of the planets. 

 John Kepler was born in 1,57 1. His parents, though noble, 

 were poor, and always in difficulties, but in spite of all 

 obstacles he managed to educate himself, and even to take 

 his degree at the University of Tubingen. In 1594 he 

 was made Professor of Astronomy at Gratz, in Styria, and 

 while there he began his attempts to discover the number, 

 size, and orbits of the planets, but at first with no success. 

 In 1597, when the Catholics at Gratz rose against the 

 Protestants, Kepler, being a Protestant, was forced to leave 

 the city, and would have been in great difficulties if his 

 friend Tycho Brahe had not invited him to come to Prague 

 as his assistant in the observatory. Here Kepler worked 

 with Tycho at his astronomical tables, called the 'Rudolphine 

 Tables,' in honour of the Emperor Rudolph; and when 

 Tycho died, in 1601, he succeeded him as principal mathe- 

 matician to the Emperor. 



