FREE ESSAY ON GALILEO GALILEI

GALILEO GALILEI

Galileo Galilei's father, Vincenzo Galilei (c.1520 - 1591), who described himself as a
nobleman of Florence, was a professional musician. He carried out experiments on strings
to support his musical theories. Galileo studied medicine at the university of Pisa, but
his real interests were always in mathematics and natural philosophy. He is chiefly
remembered for his work on free fall, his use of the telescope and his employment of
experimentation. 
After a spell teaching mathematics, first privately in Florence and then at the
university of Pisa, in 1592 Galileo was appointed professor of mathematics at the
university of Padua (the university of the Republic of Venice). There his duties were
mainly to teach Euclid's geometry and standard (geocentric) astronomy to medical
students, who would need to know some astronomy in order to make use of astrology in
their medical practice. However, Galileo apparently discussed more unconventional forms
of astronomy and natural philosophy in a public lecture he gave in connection with the
appearance of a New Star (now known as 'Kepler's supernova') in 1604. In a personal
letter written to Kepler (1571 - 1630) in 1598, Galileo had stated that he was a
Copernican (believer in the theories of Copernicus). No public sign of this belief was to
appear until many years later. 
In the summer of 1609, Galileo heard about a spyglass that a Dutchman had shown in
Venice. From these reports, and using his own technical skills as a mathematician and as
a workman, Galileo made a series of telescopes whose optical performance was much better
than that of the Dutch instrument. The astronomical discoveries he made with his
telescopes were described in a short book called Message from the stars (Sidereus
Nuncius) published in Venice in May 1610. It caused a sensation. Galileo claimed to have
seen mountains on the Moon, to have proved the Milky Way was made up of tiny stars, and
to have seen four small bodies orbiting Jupiter. These last, with an eye on getting a job
in Florence, he promptly named 'the Medicean stars'. 
It worked. Soon afterwards, Galileo became 'Mathematician and [Natural] Philosopher' to
the Grand Duke of Tuscany. In Florence he continued his work on motion and on mechanics,
and began to get involved in disputes about Copernicanism. In 1613 he discovered that,
when seen in the telescope, the planet Venus showed phases like those of the Moon, and
therefore must orbit the Sun not the Earth. This did not enable one to decide between the
Copernican system, in which everything goes round the Sun, and the Tychonic (Tycho Brahe)
one in which everything but the Earth (and Moon) goes round the Sun which in turn goes
round the Earth. Most astronomers of the time in fact favoured the Tychonic system.
However, Galileo showed a marked tendency to use all his discoveries as evidence for
Copernicanism, and to do so with great verbal as well as mathematical skill. He seems to
have made a lot of enemies by making his opponents look fools. Moreover, not all of them
actually were fools. 
There eventually followed some expression of interest by the Inquisition. Prima facie,
Copernicanism was in contradiction with Scripture, and in 1616 Galileo was given some
kind of secret, but official, warning that he was not to defend Copernicanism. Just what
was said on this occasion was to become a subject for dispute when Galileo was accused of
departing from this undertaking in his Dialogue concerning the two greatest world
systems, published in Florence in 1632. Galileo, who was not in the best of health, was
summoned to Rome, found to be vehemently suspected of heresy, and eventually condemned to
house arrest, for life, at his villa at Arcetri (above Florence). He was also forbidden
to publish. By the standards of the time he had got off rather lightly. 
Galileo's sight was failing, but he had devoted pupils and amanuenses, and he found it
possible to write up his studies on motion and the strength of materials. The book,
Discourses on two new sciences, was smuggled out of Italy and published in Leiden (in the
Netherlands) in 1638. 
Galileo wrote most of his later works in the vernacular, probably to distance himself
from the conventional learning of university teachers. However, his books were translated
into Latin for the international market, and they proved to be immensely influential.