After finding an old book of mine, The Ten Most Beautiful Experiments, over winter break, I wanted to follow up on my last post. I’ll say that this post is based almost entirely on that book’s chapter on Galileo, but since I don’t see it summarized in many places, I thought it was worth writing up. It is somewhat in vogue to claim that Galileo didn’t actually perform his experiments on falling bodies, and his writings just describe thought experiments. However, this actually confuses two different experiments attributed to Galileo. Most historians do believe stories of Galileo dropping weights from the Leaning Tower of Pisa are apocryphal and come from people confusing what is a thought experiment that Salviati, one of the fictional conversationalists in Two New Sciences, describes doing there, or a relatively unsourced claim by Galileo’s secretary in a biography after his death.
However, Salviati also describes an experiment that Galileo is recognized as having done: measuring the descent of balls of different weights down ramps, which also follow the same basic equation as bodies in free fall, but modified by the angle of slope. I think a few people may doubt Galileo actually completed the ramp experiment, based on criticisms by Alexandre Koyré in the 1950s that Galileo’s methods seemed too vague or imprecise to measure the acceleration. However, many researchers (like the Rice team in an above link) have found it possible to get data close to Galileo’s using the method Salviati describes. Additionally, another historian, Stillman Drake, who had access to more of Galileo’s manuscripts found what appears to be records of raw experimental data that show reasonable error. Drake also suggests that Galileo may have originally kept time through the use of musical tempo before moving on the water clock. Wikipedia (I know, but I don’t have much to go on) also suggests Drake does believe in the Leaning Tower of Pisa experiment. While he may not have done it at that tower, evidently Galileo’s accounts include a description that corresponds to an observed tic that happens if people try to freely drop objects of different sizes at the same time, which suggest he tried free fall somewhere.