GALILEO AND THE NEW PHYSICS 



yet he was permitted in the main to carry on his 

 experimental observations unrestrained. These ex- 

 periments gave him a place of unquestioned authority 

 among his contemporaries, and they have transmitted 

 his name to posterity as that of one of the greatest 

 of experimenters and the virtual founder of modern 

 mechanical science. The experiments in question 

 range over a wide field; but for the most part they 

 have to do with moving bodies and with questions 

 of force, or, as we should now say, of energy. The 

 experiment at the leaning tower showed that the 

 velocity of falling bodies is independent of the weight 

 of the bodies, provided the weight is sufficient to 

 overcome the resistance of the atmosphere. Later 

 experiments with falling bodies led to the discovery 

 of laws regarding the accelerated velocity of fall. 

 Such velocities were found to bear a simple relation to 

 the period of time from the beginning of the fall. 

 Other experiments, in which balls were allowed to 

 roll down inclined planes, corroborated the observation 

 that the pull of gravitation gave a velocity propor- 

 tionate to the length of fall, whether such fall were 

 direct or in a slanting direction. 



These studies were associated with observations on 

 projectiles, regarding which Galileo was the first to 

 entertain correct notions. According to the current 

 idea, a projectile fired, for example, from a cannon, 

 moved in a straight horizontal line until the pro- 

 pulsive force was exhausted, and then fell to the 

 ground in a perpendicular line. Galileo taught that 

 the projectile begins to fall at once on leaving the 

 mouth of the cannon and traverses a parabolic course. 



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