78 THE PATH OF SCIENCE 



human body, mainly in Italy. He soon found errors in 

 Galen's descriptions and corrected them. Despite bitter op- 

 position, Vesalius at last prevailed; and modern anatomy was 

 born. Even more revolutionary in its opposition to authority 

 than the work of Vesalius was that of Copernicus, which 

 affected the whole thought of man with its new picture of 

 the universe. This picture was important not only in its 

 scientific aspect but also from the philosophical point of view. 

 Before Copernicus, the earth was the center of the universe, 

 and the teleological point of view, that the earth was created 

 for man, was a basic idea of both philosophy and theology. 

 With the abandonment of the earth as the center and the 

 understanding that the sun was the center of the solar system, 

 around which the planets revolved, man lost his intrinsic 

 importance as the being around whom the whole universe 

 was designed. 



About this time, two great optical instruments were in- 

 vented, the compound microscope and the telescope. The 

 use of the telescope by Galileo led to his astronomical dis- 

 coveries. In addition, Galileo throughout his life was 

 occupied with physical investigations. His work opened 

 the way to the advancement of the science of mechanics, 

 especially because he was able to demonstrate experimentally 

 the incorrectness of a statement ascribed generally, but 

 wrongly,* to Aristotle, that bodies should fall with velocities 

 proportional to their ^veights. Galileo showed by direct ex- 

 periment that this statement is incorrect. The effect of 

 Galileo's experiment was much greater than the inere dem- 

 onstration of a new fact might be assumed to be, because it 

 tended to destroy the authority of Aristotle and to teach men 

 that the validity of a fact is to be tested by direct experiment 

 instead of by quotation of any authority, however great. 



The first astronomical observation made by Galileo in- 

 volved another disproof of an Aristotelian doctrine. In 

 1604, he observed a nova and foinid that, like the stars in 

 general, it showed no parallax. Aristotle had regarded the 

 outer zone of the stars as absolutely changeless, whereas the 



* V. Nature, 158, 1946, p. 906. 



