Education• After 4 years, he said he wanted to be a monk. But
this was not what his father had in mind so he
withdrew him from the monastery.
• In 1581, at the age of 17, he gave into his father’s
wishes and entered the University of Pisa and took
medicine just as what his father wanted him to do
• In 1585, he gave up his courses in Medicine without
completing his degree and pursued to become a
Mathematics Teacher. Then, he began teaching
Math privately in Florence
Early Life• Galileo became an accomplished lutenist himself
• Three of Galileo's five siblings survived infancy,
and the youngest Michelangelo (or Michelagnolo)
also became a noted lutenist and composer,
although he contributed to financial burdens
during Galileo's young adulthood
• Michelangelo would also occasionally have to
borrow funds from Galileo for support of his
musical endeavours and excursions
• Galileo was named after an ancestor, Galileo
• Galileo Bonaiuti was buried in the same church,
the Basilica of Santa Croce in Florence, where
about 200 years later his more famous
descendant Galileo Galilei was buried too
• The Ancient Greek scientist, Aristotle,
taught that heavier objects fall faster than
lighter ones, a belief still held in Galileo's
lifetime. But Galileo wasn't convinced.
Experimenting with balls of different sizes
and weights, he rolled them down ramps
with various inclinations. His experiments
revealed that all of the balls boasted the
same acceleration independent of their
• Galileo is often incorrectly credited with the
creation of a telescope. Instead, he significantly
improved upon them
• In 1609, he first learned of the existence of the
spyglass, which excited him. He began to
experiment with telescope-making, going so far
as to grind and polish his own lenses. His
telescope allowed him to see with a
magnification of eight or nine times. In
comparison, spyglasses of the day only provided
a magnification of three.
• It wasn't long before Galileo turned his telescope
heavenward. He was the first to see craters on
the moon, discover sunspots, and track the
phases of Venus
• And recent research seems to imply he
discovered Neptune two centuries before it was
• Of all of his telescope discoveries, he is perhaps
most known for his discovery of the four most
massive moons of Jupiter (Io, Ganymede,
Europa, Callisto), now called the Galilean
• When NASA sent a mission to Jupiter in the
1990s, it was called Galileo in honor of the
• In Galileo's lifetime, all celestial bodies were thought to orbit
the Earth. Supported by the Catholic Church, teaching
opposite of this system was declared heresy in 1615.
• Galileo, however, did not agree. His research — including his
observations of the phases of Venus and the fact that Jupiter
boasted moons that didn't orbit Earth — supported the
Copernican system, which (correctly) stated that the Earth
and other planets circle the sun.
• In 1616, he was summoned to Rome and warned not to teach
or write about this controversial theory. But in 1632, believing
that he could write on the subject if he treated it as a
mathematical proposition, he published work on the
Copernican system. He was found guilty of heresy, and was
placed under house arrest for the remaining nine years of his
• He proposed a principle of inertia, which became the
foundation of Newton's First Law of Motion. Though this
concept had been put forth by others, Galileo was the
first to formalize it mathematically.
Astronomy, the Telescope, & the Heliocentric Universe:
•In 1608, the telescope was invented in the Netherlands. Over the next
year, Galileo had heard about it and crafted his own improvements.
With the improved telescope, he was able to observe the heavens more
closely than ever before and identified three of Jupiter's moons. This,
along with observing the phases of Venus, provided support for the
Copernican heliocentric model of the universe over Ptolemy's geocentric
In addition, he made many other significant observations. He was the
first to observe sunspots, the rings of Saturn, and lunar mountains and
Galileo's First Controversy:
• Galileo's support of a heliocentric theory was seen by
the Roman Catholic Church as contradicting various
• In 1616, Galileo first defended himself against the
Church. Galileo was ordered not to "hold or defend"
the idea that the Earth moved and the Sun remained
stationary at the center. For several years, Galileo was
able to discuss heliocentric theory hypothetically
without arousing undue ire from the Church.
• In 1632, Galileo published Dialogue Concerning the Two
Chief World Systems with the permission of Pope Urban
VII, who had supported Galileo in the earlier conflict (as
Cardinal Barberini). Urban had two conditions:
-Galileo was to include arguments for both heliocentric
and geocentric viewpoints
-Urban's own views on the matter were to be included
• Unfortunately, the book turned out to be biased in favor
of heliocentrism and the Pope did not appreciate the
perceived public ridicule. Galileo was ordered to stand
trial for suspicion of heresy in 1633.
• The 1633 hearing did not go as well as the one in 1616,
and Galileo was found guilty of heresy. His sentence had
-He was required to recant his heliocentric views
-He was imprisoned (though this later got commuted
to house arrest at his estate near Florence)
-His Dialogue was banned, and all other works written
by him (or to be written by him) were forbidden, though
this latter part was not enforced.
• While under house arrest, Galileo wrote Two New
Sciences, which outlined his earlier work in kinematics
and the strength of materials. This book was praised by
both Sir Isaac Newton and Albert Einstein.
Death and Redemption
• Galileo died of natural causes in 1642, after having gone blind.
• He was reburied at Santa Croce, sacred ground, in 1737. In
1741, Pope Benedict XIV authorized publication of Galileo's
complete works. Heliocentrism was formally rescended as
heresy in 1758.
• It was not until October 31, 1992, that the Church under Pope
John Paul II expressed regret over how Galileo had been
treated, in response to a Pontifical Council for Culture study.
• Galileo Galilei is one of the most influential and famous
scientists in human history, having contributed to a wide range
of fields and establishing the mathematical and experimental
foundations of modern physics and astronomy.
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