A NEW ASTRONOMY 219 



of mere authority, whether in science, philosophy, or theology. 

 It was a true instinct of the conservatives to recognize in him 

 the champion of a principle fatally hostile to their own. Between 

 these antagonistic principles no permanent peace was possible. 



While still a mere youth, he discovered the regularity of pendulum 

 vibrations by observing the slow swinging of the cathedral lamp 

 of Pisa (1582). Before he was 25 he published work on the 

 hydrostatic balance (1586), and on the centre of gravity of solids. 

 Only a little later he conducted at the leaning tower simple ex- 

 periments in falling bodies, which upset world-old notions on 

 this everyday matter, showing that the velocity of descent is 

 not, as was commonly supposed, proportional to weight. And 

 "yet the Aristotelians, who with their own eyes saw the unequal 

 weights strike the ground at the same instant, ascribed the effect 

 to some unknown cause, and preferred the decision of their master 

 to that of nature herself." 



He further showed that the hypothesis of uniform acceleration 

 accounted correctly for the observed relations between space, 

 time and velocity, and that the path of a projectile is a parabola. 

 In the words of a recent authority, when Galileo 



deduced by experiment, and described with mathematical pre- 

 cision, the acceleration of a falling body, he probably contributed 

 more to the physical sciences than all the philosophers who had 

 preceded him. 



Hearing of the telescope newly invented in Holland, he con- 

 structed one for himself, by means of which he discovered sun 

 spots, the mountains of the moon, the satellites of Jupiter, the 

 rings of Saturn, and the phases of Venus. The sensation created 

 by these discoveries is described in the following passages from 

 Fahie's Life of Galileo and Brewster's Martyrs of Science. 



'As the news had reached Venice that I had made such an in- 

 strument, six days ago I was summoned before their Highnesses, the 

 Signoria, and exhibited it to them, to the astonishment of the whole 

 senate. Many of the nobles and senators, although of a great age, 

 mounted more than once to the top of the highest church tower in 



