Galileo Galilei (1564–1642) is commonly regarded as the founder of the modern experimental method. Before him, physics was dominated by the authority of Aristotle, according to whom bodies fell with a velocity proportional to their weight. Galileo had the courage to subject this claim to the judgement of experiment, a revolutionary act for the time (Simonyi 2012, ch. 3).
Unable to measure free fall directly, as it was too fast for the timepieces of his day, he had the brilliant idea of “diluting” gravity by rolling bronze balls down inclined planes (with an inclination of to the horizontal). He measured the times with a water clock: he weighed the water that dripped from a container during each descent. With this apparatus he showed that the distance covered grows as the square of time, , and that the distances covered in successive equal time intervals follow the sequence of odd numbers — — a discovery he himself considered “marvellous”.
The legend of the Leaning Tower of Pisa
The legend of Galileo dropping two balls of different mass from the leaning tower to show that they arrive together is reported by his first biographer Vincenzio Viviani, but modern historians are sceptical: it is probably an anecdote invented to glorify the master. But the experiment is plausible and captures the essence of the Galilean method: putting ideas to the test with experiment, not with authority (Drake 2001, ch. 2; Buchwald and Fox 2014).
The most philosophically revolutionary aspect of Galileo’s work is idealisation: the notion that the “true law” of falling holds in a vacuum (without friction, without air resistance), and that reality is to be approximated to that ideal law. Jammer points out how this separation between “mathematical essence” and “real-world imperfection” underlies modern physics (Jammer 1957, ch. 5).
For the works cited, see Riferimenti bibliografici.
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Topics: Kinematics Concepts: Free fall
Related exercises: True or false on free fall · Estimating g with a marble · True or false on velocity and acceleration