20 GREAT MEN OF SCIENCE 



no trace of spherical bowls of crystal, by which the planetary 

 motions were still regarded as being guided. Nevertheless, 

 Tycho still found it difficult to assume that the earth moved; 

 he saw too many objections to this idea. It is unjust to 

 interpret this as weakness, in the case of a man whose life 

 work gave us the means of completely meeting all possible 

 objections to this theory. What was missing was 'dynamics,' 

 the knowledge of the laws of motion of matter and the forces 

 acting upon them, which apply equally to the stone when 

 thrown upon the earth, to the whole earth, and to all the 

 other heavenly bodies. The road to this end was a long one; 

 and was only completely traversed by Newton. 



Tycho had reddish hair and was a great friend of animals.^ 



SIMON STEVIN 

 1^48-1620 



This scientist, who is all too little known, was according to 

 Leonardo the first to continue consciously Archimedes' 

 studies in mechanics. He also quite expressly based his 

 work upon this master of antiquity. Copernicus and Tycho 

 attempted to discover the actual motions of the heavenly 

 bodies which are presented to us for observation, but are 

 entirely beyond our interference, and to understand the world 

 on this basis; Stevin again turned to earthly machines; 

 inclined planes, levers, pulleys, first engaged his attention, 



1 As a result of a duel, Tycho at the age of twenty lost part of his nose. 

 The missing piece was replaced by some kind of metal contrivance made 

 of gold and silver. As Dreyer says: 'The various portraits which we 

 possess of Tycho show distinctly that there was something strange about 

 the appearance of his nose, but we cannot say with certainty whether it 

 was the tip or the bridge that was injured, though it seems to be the 

 latter.' The astronomer J. L. E. Dreyer gave us an excellent life en- 

 titled Tycho Brahe, a Picture of Scientific life and work in the sixteenth 

 century (Edinburgh, 1890). 



