Galileo was an Italian physicist and astronomer who initiated the scientific
revolution that flowered in the work of the English physicist Sir Isaac Newton. Born
Galileo Galilei, his main contributions were, in astronomy, the use of the telescope in
observation and the discovery of sunspots, lunar mountains and valleys, the four largest
satellites of Jupiter, and the phases of Venus. In physics, he discovered the laws of falling
bodies and the motions of projectiles. In the history of culture, Galileo stands as a symbol
of the battle against authority for freedom of inquiry.
Galileo was born near Pisa, on February 15, 1564. His father, Vincenzo Galilei,
played an important role in the musical revolution from medieval polyphony to harmonic
modulation. Galileo was taught by monks at Vallombrosa and then entered the University
of Pisa in 1581 to study medicine. He soon turned to philosophy and mathematics,
leaving the university without a degree in 1585.
For a time he tutored privately and wrote
on hydrostatics and natural motions, but he did not publish any of this. In 1589 he
became professor of mathematics at Pisa, where he is reported to have shown his students
the error of Aristotle's belief that speed of fall is proportional to weight, by dropping two
objects of different weight simultaneously from the Leaning Tower. His contract was not
renewed in 1592, probably because he contradicted Aristotelian professors. The same
year, he was appointed to the chair of mathematics at the University of Padua, where he
remained until 1610.
At Padua, Galileo invented a calculating compass for the practical
solution of mathematical problems. He turned from physics to measurements, he
discovered the law of falling bodies and of the parabolic path of projectiles, and he also
studied the motions of pendulums, and investigated mechanics and the strength...