It soon became clear that medicine was not Galileo's first
love. Rather, the young scholar became intrigued by mathematics,
and found inspiration in the form of Ostilio Ricci, a mathematician
in the court of the Tuscan Grand Duke. Ricci, impressed by Galileo's curiosity,
agreed to tutor him privately. From 1581 to 1585, Galileo continued
to formally pursue a degree in medicine, while Ricci educated him
in geometry and applied mathematics. These years were a formative
period for the young man, and in 1583 he made his first famous
discovery: that each swing of a pendulum, regardless of width,
takes an equal amount of time to swing between the extremes of
its arc. This suggested that pendulums could be used to mark small
intervals of time, and professors at the university quickly pounced
on the notion, creating a device called a "pulsilogia," to keep
track of a medical patient's heartbeat.
Galileo's discovery temporarily restored him to the good
graces of his professors, but he showed a patent lack of interest
in medicine, and skipped so many of the required lectures that
he was soon in danger of failing out of the university. Meanwhile,
the Galilei family was running short of funds, and Galileo's father
suggested that he apply for a scholarship offered by the Duke of
Tuscany. Galileo did so, but his poor record as a medical student
doomed his application, and in 1585 he was forced to leave the
University of Pisa without a degree. For the next four years,
he earned his keep in Florence by working as a private tutor in
mathematics, and continued to make experiments on his own. He
invented a device to measure the relative weights of alloys in a
metal, improving on the work of the ancient mathematician Archimedes,
and distinguished himself in a city-wide contest by most convincingly
determining the location, shape, and dimensions of Hell as portrayed
in Dante's famous Inferno. (This was no small
issue, since Florence was Dante's birthplace, and the great Italian
poet's 16th-century fans treated him as a kind of secular saint.)
During this time Galileo also earned the praise of the noted Jesuit
mathematician, Christopher Clavius, the man responsible for the
great calendar reform that the Church had put into effect in January
1582. But Galileo wanted not only praise from Clavius, but patronage:
he aspired to become a university professor, but had been meeting
with repeated failure. By 1589, he had been rejected as under-qualified
for positions all across northern Italy. Despairing, he and a
friend considered leaving for Constantinople and the Turkish East
in search of employment. But in the summer of 1589, a position
teaching mathematics opened at the University of Pisa, in the city
of his birth- -and this time, Galileo's application was accepted.
At the University, Galileo quickly developed a rivalry
with the older, more established professors, particularly a conservative
philosopher named Girolamo Borro. Philosophy, in the 16th century, incorporated
a wider range of investigations than it does today, including questions
of natural science and physics, and Borro had written extensively
on the ocean's tides, as well as the properties of motion. He
was an Aristotelian, like most scholars of his day, meaning that
he based his work on the ancient Greek philosopher Aristotle.
But Borro did not accept Aristotle's precepts on faith alone, and
advocated a science based on experimentation. Galileo much doubted
many Aristotelian claims, and resolved to test one of the more
famous ones, namely, that "the downward motion of a mass of gold
or lead, or of any other body endowed with weight, is quicker in
proportion to its size." In other words, the heavier an object,
the faster it falls. According to legend, Galileo ascended to the
top of the famous Leaning Tower of Pisa, and dropped balls of different
weights and sizes to the ground. Each pair, regardless of composition
or weight, hit the ground at the same time, laying Aristotle's
clever, but mistaken theory to rest.
If this event really took place, it would have been a
brilliant act of scientific theater. And it does seem to fit with
Galileo's character during his three years in Pisa: he was a gadfly,
a sharp-tongued teacher who earned the esteem of students but the
enmity of older professors like Borro for his theatrics and disrespect
for their authority. Possibly because of the enemies he had made,
or possibly by his own request, Galileo's contract at the university
was not renewed, and by summer 1592 he was out of a job. By now,
however, he had established a reputation as one of the bright lights
of the mathematical field, and he carried this reputation with
him out of the Duchy of Florence and into the territory governed
by that great maritime power, the Serene Republic of Venice. There
in autumn of 1592, the Venetian Senate chose him as the chair in
mathematics at the University of Padua.
