 A biography by Galileo 's pupil Vincenzo Viviani stated that Galileo had dropped balls of the same material , but different masses , from the Leaning Tower of Pisa to demonstrate that their time of descent was independent of their mass . This was contrary to what Aristotle had taught : that heavy objects fall faster than lighter ones , in direct proportion to weight . While this story has been retold in popular accounts , there is no account by Galileo himself of such an experiment , and it is generally accepted by historians that it was at most a thought experiment which did not actually take place . An exception is Drake , who argues that the experiment did take place , more or less as Viviani described it . The experiment described was actually performed by Simon Stevin ( commonly known as Stevinus ) and Jan Cornets de Groot , although the building used was actually the church tower in Delft in 1586 . However most of his experiments with falling bodies were carried out using inclined planes where both the issues of timing and wind resistance were much reduced . 
