141, 142] 



Kepler's First and Second Laws 



187 



Kepler stated that the earth's path also must be an oval 

 of some kind, and was evidently already convinced aided 

 by his firm belief in the harmony of Nature that all the 

 planets moved in accordance with the same laws. This view 

 is indicated in the dedication of the book to the Emperor 

 Rudolph, which gives a fanciful account of the work as a 



FIG. 61. Diagram used by Kepler to establish his laws of planetary 

 motion. From the Commentaries on Mars. 



struggle against the rebellious War-God Mars, as the result 

 of which he is finally brought captive to the feet of the 

 Emperor and undertakes to live for the future as a loyal 

 subject. As, however, he has many relations in the 

 ethereal spaces his father Jupiter, his grandfather Saturn, 

 his dear sister Venus, his faithful brother Mercury and he 

 yearns for them and they for him on account of the similarity 

 of their habits, he entreats the Emperor to send out an 



