Doubting, Testing, and Confirming Galileo: A translation of Giovanni Battista Riccioli's experiments regarding the motion of a falling body, as reported in his 1651 Almagestum Novum

Abstract

The Italian astronomer Giovanni Battista Riccioli is commonly credited with performing the first precise experiments to determine the acceleration of a freely falling body. Riccioli has been discussed by historians of science, sometimes positively but often not, but translations of his work into modern languages are not readily available. Presented here is a translation of his experiments regarding the nature of the motion of a falling body. Riccioli provides a thorough description of his experiments, and his data are quite good. He appears to have a model approach to science: He attacks the question of free fall with the expectation of disproving Galileo's ideas, yet he is convinced by his data that Galileo is indeed correct, and he promptly informs a former prot\'eg\'ee of Galileo's of the results.