Was Galileo Really the First and Is the Leaning-Tower-of-Pisa Story True?

Equivalence-Principle Experiments in Antiquity

Marshall Claget in his book, Greek Science in Antiquity, in the chapter Greek Science in the Age of Justinian, page 173, quotes from John Philoponus' commentary on Aristotle's Physics (about A.D. 550, 880 years after Aristotle):

"...Conversely, the ratio of the weights of the bodies would have to be equal to the inverse ratio of the times required for the motions.

But this is completely erroneous, and our view may be corroborated by actual observation more effectively than by any sort of verbal argument. For if you let fall from the same height two weights of which one is many times as heavy as the other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights, but that the difference in time is a very small one."

It is reasonable to assume that many people in antiquity let two objects of different weight fall. What is unreasonable is that this had almost no effect on what people believed about the physics of falling bodies. It took someone of great statue (Galileo), a new intellectual climate, and much travail to finally get the message across.

Equivalence-Principle Experiments in Galileo's Time

Stillman Drake in his book, Galileo At Work, His Scientific Biography, on page 20, discusses an experiment by Simon Stevin who dropped two weights from a height of 30 feet and published the results in 1586, a little earlier than Galileo.

Again it is reasonable to assume that many people had done this; but because of Aristotle's great influence, the consequences of this result never entered the main stream of Philosophy until after Galileo.

Aristotle's Influence

Fritz Zwicky writing about Supernovas in the Handbuch der Physik quotes Tycho Brahe's comment about the new star (Supernova) which he saw in 1572:

"The philosophers teach us, and we know that it is true, that the Heavens are perfect and unchangeable. Yet we see this new star. What are we to make of this? The answer is that God in His infinite wisdom can make a change to the Heavens if He so pleases."

So we see why Aristotle's ideas held for 2000 years against simple experiment. In all fairness, however, it should be pointed out that it was first necessary to measure the "new" star's parallax to be sure that it was truly a star and not an atmospheric phenomenon. Tycho Brahe undertook these measurements and proved beyond doubt that the new object was a star. In addition Brahe measured the parallax of the Comet of 1577 and showed that it was located far beyond the Moon. This again was contrary to Aristotle who taught that comets were located between the Moon and the Earth, so that their appearance did not represent a change in the "perfect" heavens.

Thus Tycho Brahe's measurements and observations undermined Aristotle and created the climate in which Galileo was able to overthrow Atristotian Physics.

Did the Leaning-Tower-of-Pisa Experiment Really Happen?

Stillman Drake in Galileo At Work, His Scientific Biography, p. 19 and p. 414, also discusses the Leaning-Tower-of-Pisa experiment. His conclusion is that he actually did it, but that it was more a qualitative demonstration than a careful scientific experiment.

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