GALILEO GALILEI, 1564 1642. 



A S a boy, Galileo, as he liked to be called, showed great promise. 

 -^- He was a keen observer and a straight thinker, as his com- 

 panions soon learned. We all know the story of how in the Cathe- 

 dral of Pisa he noticed that as the great lamp which hung from the 

 arched roof swung back and forth it always took the same length of 

 time for its journey. This gave him the discovery of the laws of the 

 pendulum. 



Later he worked out the law of falling bodies by letting two balls 

 of unequal weight fall from the top of the leaning tower of Pisa. 

 They reached the bottom at the same time, thus disproving the 

 belief of Aristotle held for over 2000 years, that heavier bodies fall 

 faster than lighter ones. He also made the first thermometer and 

 learned many new facts about light, heat, and air pressure. 



But we remember him best for his improvement of the telescope 

 and his discoveries in astronomy. He was the first to see that 

 there were moons revolving around Jupiter, to discover the rings of 

 Saturn, and to observe the rotation of the sun. The movement of 

 sun spots across the sun's disk proved to him that the sun revolved. 



Galileo weighed air and started his pupil Torricelli upon many 

 experiments involving air pressure and vacuums. It was while 

 engaged in this work that Torricelli produced the first mercury 

 barometer. 



Galileo was one of the first men to make use of the scientific 

 method and to apply the test of the experiment in order to learn 

 new facts and to prove the unchangeable relation between cause 

 and effect. 



