How the Heavens Go Galileo Galilei

The Tale of the Tower
Legend has it that a young, ambitious, and at that moment frustrated mathematics
professor climbed to the top of the bell tower in Pisa one day, perhaps in 1591,
with a bag of ebony and lead balls. He had advertised to the university community
at Pisa that he intended to disprove by experiment a doctrine originated
by Aristotle almost two thousand years earlier: that objects fall at a rate proportional
to their weight; a ten-pound ball would fall ten times faster than a onepound
ball. With a flourish the young professor signaled to the crowd of amused
students and disapproving philosophy professors below, selected balls of the
same material but with much different weights, and dropped them. Without air
resistance (that is, in a vacuum), two balls of different weights (and made of any
material) would have reached the ground at the same time. That did not happen
in Pisa on that day in 1591, but Aristotle’s ancient principle was clearly violated
anyway, and that, the young professor told his audience, was the lesson. The
students cheered, and the philosophy professors were skeptical.
The hero of this tale was Galileo Galilei. He did not actually conduct that
“experiment” from the Tower of Pisa, but had he done so it would have been
entirely in character. Throughout his life, Galileo had little regard for authority,
and one of his perennial targets was Aristotle, the ultimate authority for university
philosophy faculties at the time. Galileo’s personal style was confrontational,
witty, ironic, and often sarcastic. His intellectual style, as the Tower
story instructs, was to build his theories with an ultimate appeal to observations.
The philosophers of Pisa were not impressed with either Galileo or his methods,
and would not have been any more sympathetic even if they had witnessed
the Tower experiment. To no one’s surprise, Galileo’s contract at the University
of Pisa was not renewed.