Law of Falling Bodies (ca. 1609–ca. 1632): There is a popular legend in science that Galileo derived his theories on the nature of gravity and falling bodies by dropping weighted objects from the top of the Tower of Pisa in Italy. While scientific historians have discredited the occurrence of this event, it does provide an indication of the direction that science was taking during the early 17th century. Since the time of the ancient Greeks scientists have attempted to explain the forces that control a falling object. As was typical of the times, the Greek philosopher Aristotle derived an explanation that was based solely on the power of observation, and not substantiated by experimental evidence. To Aristotle, the acceleration of an object after it was dropped was a function of the weight of the object, with heavier objects accelerating more quickly in comparison to lighter objects dropped from the same height. However, he did recognize that the density of the medium had an influence on the acceleration of an object. He considered this to be an inverse relationship. Thus, as the density of the medium through which the object was passing decreased, the speed increased. Unfortunately, Aristotle used this logic to support his idea that vacuums could not exist in nature, as by his definition an object in a vacuum would have infinite speed (see VACUUM PUMP). Although there were opponents of Aristotle’s view, for example the Greek philosopher John Philoponus (ca. 6th century), who provided experimental evidence against Aristotle’s ideas, his reputation and vastness of work in science and philosophy perpetuated his ideas until the time of the Renaissance.
In the opening years of the 17th century a number of physical forces, from planetary motion to magnetism (see KEPLER’S THEORY OF