Galileo Galilei (1564-1642)
Born February 15 1564 in Pisa, in a declining
family of Florentine patricians.
In 1581 he was sent to study medicine
at the University of Pisa, but never showed much interest in the
subject and starting in 1583 devoted himself exclusively
to mathematics and philosophy. He left Pisa without a degree,
yet in July 1589 he was appointed to the chair of mathematics
at that same university. In 1592 he took on the prestigious
chair of mathematics at the university of Padua.
Prior to 1609, Galileo
had only shown passing interest in astronomical matters,
despites privately presenting himself as a Copernican. His research
while at Pisa and Padua
was mostly concerned with the problem of motion,
in particular motion on inclined planes, of the pendulum,
and of freely falling bodies. First little known outside of Italy,
telescopic discovery in 1609 and 1610 instantly propelled him
into international fame, and won him a position
at the Florentine Court,
as chief mathematician and philosopher
to the Grand Duke of Tucsany, Cosimo de Medici II.
Galileo's telescopic discoveries, published in his landmark
1610 book Sidereus Nuncius
shook the very foundations
of the Ptolemaic/Aristotelian cosmology. His
observations of the Moon's surface
revealed valleys and mountains, instead of the smooth perfectly
spherical surface postulated by
His observations of
multitudes of faint stars
gave some credence to Copernicus' suggestion that the universe
may be a lot larger than hitherto believed. Perhaps his
most striking discovery was that of
four moons orbiting
Jupiter, in direct contradiction with another Aristotelian
postulate, that of the Earth being the center of (circular)
motion for all heavenly bodies.
In the following two years Galileo made two new sets of observations
that would further undermine the prevailing Aristotelian/Ptolemaic
cosmology. The first was the observation of the phases of Venus,
and the second the observation of sunspots. Galileo published his
views on the latter in his
Three Letters to Mark Wesler, in
response to the three letters written earlier by
to the same Wesler. Controversy over the priority of discovery
of sunspots would later turn Scheiner and Galileo into bitter enemies.
Following the 1616 decree suspending for revision
De Revolutionibus and an injunction by Cardinal Roberto
Bellarmino not to hold or defend the Copernican doctrine,
Galileo turned to the problem of the tides, hoping in doing to
to provide a proof of the motion of the Earth.
Galileo's pro-Copernican campaign culminated with the publication
of his 1632
Dialogue concerning the two chief
The Roman ecclesiastic authorities considered the book to violate
the 1616 decree. In September 1632 Galileo was summoned to Rome
by the Inquisition and was put on trial.
On June 22 1633
Galileo was forced to kneel in front of the
Roman Inquisition and
recant his beliefs in the Copernican doctrine and the motion
of the Earth. He was then
sentenced to life imprisonment, which was almost immediately
commuted to perpetual house arrest without visitors, ostensibly for
having disobeyed a 1616 injunction by Cardinal Bellarmine
"...not to defend or teach
the Copernican doctrine...". Galileo's Dialogue
was put on the Index of Prohibited Books, as well as
Copernicus' De Revolutionibus and the books of
with planetary theory.
Galileo's sentence was upheld rather rigidly despites
numerous appeals to the Inquisition and the Pope by Galileo himself,
as well as numerous prominent scientists and statesmen in Italy and Europe.
After Galileo became blind in 1637, the enforcement of his
sentence was relaxed somewhat, and he was allowed to receive visitors
for extended periods of time.
In 1638 he completed yet another landmark work,
Discourses on Two New Sciences
provided the foundations for the modern science of mechanics.
The manuscript was smuggled out of Italy and the book
published in Holland.
Galileo died on the evening of January 8,
1642. The Roman ecclesiastic authorities vetoed the
public funeral and honor planned by the Florentine state.
His books, together with those of Copernicus and Kepler,
were removed from the Index in 1835, and only in 1992 did
the Roman catholic Church formally
admitted to having erred in dealing with Galileo.
Drake, S. 1978, Galileo at work: his scientific biography,
Chicago: The University of Chicago Press (1995 Dover reprint).
De Santillana, G. 1955, The crime of Galileo,
The University of Chicago Press
Fantoli, A. 1996, Galileo, Vatican Observatory Publications
[distributed outside of Italy by the University of Notre Dame Press].
Galileo, G. 1610, Sidereus Nuncius, trans.
A. van Helden 1989, The University of Chicago Press.
Galileo, G. 1613, Letters on Sunspots [in S. Drake (trans.) 1957,
Ideas and Opinions of Galileo], Doubleday.
Galileo, G. 1632, Dialogues concerning the two chief world systems,
trans. S. Drake, 2nd edition 1967, University of California Press
Sharratt, M. 1994, Galileo: Decisive Innovator,
Cambridge University Press