Galileo Galilei
By Isabella Romeo
Biography
Galileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who
played a major role in the Scientific Revolution. His achievements include improvements to the
telescope and astronomical observations, and support for Copernicanism. Galileo was born in
Pisa, Italy on February 15th, 1564. Galileo was the son of Vincenzio Galilei and Giulia degli
Ammannati. He was named after his ancestor, Galileo Buonaiuti, who was a doctor of medicine.
Galileo was the first of six children, although some historians believe he was the first of seven
(“The Galileo Project”). The Galilei family belonged to the nobility, but was not extravagantly
rich. Their house was always filled with music. Galileo’s father, Vincenzio, was a music teacher.
His father even taught him to play the lute. In 1572, Galileo and his family moved to Florence.
In his new home in Florence, Galileo was taught by a private tutor. Then, when he was
nearly thirteen years old, Galileo was sent away to study at the monastery school of
Vallombrosa. He decided that he wanted to become a monk, but his father was unhappy with that
idea. Galileo was pulled from the monastery school and sent to another school. Galileo was very
clever, and not just at his school lessons. He was very good at finding out how things around him
worked. He seemed to look at the world in his own particular way. Galileo returned to Pisa in
1581 and started to study at the University of Pisa, where his father hoped he would go into the
field of medicine. Galileo wanted to make his father happy, so he learned all the old theories
about the human body and diseases. Many of these ideas were not based on science, though.
Galileo started to questions what everyone else took for granted.
While at the University of Pisa, Galileo began his study of the pendulum. According to
legend, he watched a suspended lamp swing back and forth in the cathedral of Pisa (“The Galileo
Project”). In 1602, Galileo made his most notable discovery about the pendulum. He discovered
that the period (the time in which a pendulum swings back and forth) does not depend on the arc
of the swing (the isochronisms) (“The Galileo Project”). This discovery would lead to Galileo’s
further study of the time intervals and the development of his idea for a pendulum clock.
While at the University of Pisa, Galileo learned of the Ancient Greek scientist, Aristotle.
He was very interested in Aristotle’s theory of physics, and questioned the Aristotelian approach
to physics. Aristotelians believed that heavier objects fall faster through a medium than lighter
ones (The Galileo Project). Galileo eventually disproved this idea by declaring that all objects,
regardless of their density, fall at the same rate in a vacuum. To prove his theory correct, Galileo
performed various experiments in which he dropped objects from a certain height. One of his
most famous experiments was when he conducted an experiment on top of the Leaning Tower of
Pisa. He dropped two iron balls from the top of the tower; one of heavier mass and the other was
of lighter mass. Galileo proved that objects of unequal mass fall at the same rate. This
contradicted Aristotle's theory that an object of heavier mass will fall faster than a lighter object.
Some onlookers of this experiment thought that Galileo was involved in witchcraft. After a few
more experiments, scholars and professors started to believe Galileo. Galileo documented his
discoveries in his book, De Motu, which means “on motion.” (“The Galileo Project”)
Galileo was not really interested in medicine, he enjoyed mathematics. He became
inspired by Ostilio Ricci, chief mathematicians to the Grand Duke of Tuscany. In the summer of
1583, Ricci visited the Galileo household in Florence to try to persuade Vincenzio Galilei that
Galileo had a special gift. Vincenzio Galilei insisted that Galileo should stick to medical studies,
though. Galileo left the university in 1585 without completing his degree. Galileo became a
teacher to help support his family. In 1589, he was offered a job at the University of Pisa as
Professor of Mathematics. The job was not well paid, though. In 1591, Galileo’s father died. This
was a time for Galileo to think about the future. As the eldest son, he was now responsible for
the Galilei family (Galileo: The Genius who Faced the Inquisition, p. 25).
Luckily, in 1592, Galileo found a new job that was well paid. He was appointed Professor
of Mathematics at the University of Padua. While teaching there, he frequently visited a place
called the Arsenal, where Venetian ships were docked and loaded. Galileo had always been
interested in mechanical devices. Naturally, during his visits to the Arsenal, he became
fascinated by nautical technologies, such as the sector and shipbuilding. In 1593, he was
presented with the problem involving the placement of oars in galleys. He treated the oar as a
lever and correctly made the water the fulcrum. A year later, he patented a model for a pump.
His pump was a device that raised water by using only one horse. Galileo was extremely
interested in the movement of the Earth, oceans, tides, the planets, stars, and the sun. He began to
think about the ideas of the Polish astronomer Nicolaus Copernicus. Copernicus claimed that the
Earth was not the center of the universe but rather, it traveled around the sun.
To enjoy himself, Galileo often traveled from Padua to Venice, the chief city of the
Republic of Venice. It was there that Galileo met Marina Gamba, an attractive woman fourteen
years younger than he was. By 1600, Marina was expecting a baby, and she moved from Venice
to Padua to be near Galileo. On August 13, she gave birth to a girl that they named Virginia. A
second daughter, Livia, was born in 1601. In 1606, Galileo and Marina Gamba had a son named
Vincenzio. Galileo and Marina Gamba were not of the same social class so they never married.
When Galileo left Padua in 1610 to take a position at the Court of the Medici family, Marina
Gamba married another man named Giovanni Bartoluzzi. Galileo’s two daughters, Virginia and
Livia became nuns and entered the convent of San Matteo at Arcetri.
In 1610, Galileo was appointed Chief of Mathematicians and Philosopher to the new
Grand Duke of Tuscany. He was also made Chief Mathematician to the University of Pisa. It was
an honorary role that did not involve teaching. Galileo invented many mechanical devices other
than the pump, such as the hydrostatic balance. But perhaps his most famous invention was the
telescope. Galileo made his first telescope in 1609, modeled after telescopes produced in other
parts of Europe that could magnify objects three times. He created a telescope later that same
year that could magnify objects twenty times. With this telescope, he was able to look at the
moon, discover the four satellites of Jupiter, observe a supernova, verify the phases of Venus,
and discover sunspots. His discoveries proved the Copernican system which states that the earth
and other planets revolve around the sun (“The Galileo Project”). Galileo was proud to be a
member of the Lyncean Academy, the world’s first international scientific society.
Galileo's belief in the Copernican system eventually got him into trouble with the
Catholic Church. The Inquisition was a permanent institution in the Catholic Church charged
with the eradication of heresies. A committee of consultants declared to the Inquisition that the
Copernican proposition that the Sun is the center of the universe was a heresy. Because Galileo
supported the Copernican system, he was warned by Cardinal Bellarmine, under order of Pope
Paul V, that he should not discuss or defend Copernican theories. In 1624, Galileo was assured
by Pope Urban VIII that he could write about Copernican theory as long as he treated it as a
mathematical proposition (Galileo: The Genius who Faced the Inquisition, p. 38)
Galileo’s health became increasingly poor since he had moved back to Florence. In 1619,
Marina Gamba died in Venice. Galileo then managed to get full rights under the law to his son.
The following year, Galileo’s mother, Guilia, died. Galileo continued to work, trying to steer
clear of trouble. In 1618, three comets were sighted in the night sky, and they caused much
discussion. Galileo criticized the Jesuit astronomer Orazio Grassi for his opinions on a comet’s
orbit.
In 1624, Galileo began to write a new book. It was called the Dialogue of the Two
Principal Systems of the World. Its aim was to contrast the ideas of Aristotle and Ptolemy with
those of Copernicus. Galileo had been ordered not to put Copernicus’ ideas down as facts, so
instead, his book took the form of a discussion between two people. Galileo had thought that he
was on safe ground. He even discussed his project with leading church figures. The book was
published in 1632 and became a success. The argument in the book was won by the supporter of
Copernicus. To people in the church, this was a step too far. Galileo was called to Rome in 1633
to face the Inquisition again. On June 22, dressed in a white robe, Galileo knelt before the
judges and promised to give up his beliefs of Copernicus (Galileo: The Genius who Faced the
Inquisition, p. 45). Galileo was found guilty of heresy in his book, and was sent to his home near
Florence where he was to be under house arrest for the remainder of his life.
Galileo Galilei was kept under house arrest until he died on January 8, 1642, at the age of
77. During the years before his death, he had taken on a new project. He created a new book
discussing the mathematics of structures. It was called Discourses and Mathematical
Demonstrations concerning Two New Sciences and Pertaining to Mechanics and Local Motions.
He was forbidden to publish his book in Italy, but he secretly arranged for his book to be
published at Leiden in Holland, a Protestant country beyond the reach of the Inquisition. Before
his death, Galileo had become completely blind. His eyes had been permanently damaged by
years of observing the sun. The years after Galileo’s death saw many of his theories proved.
Galileo lived in an exciting age in which modern science, mathematics, medicine, and astronomy
were being born. He was someone who tried to separate science from tradition and superstition.
Galileo did not give up, though, and his important work and the truth came out in the end.
Summary of Primary Mathematical and Scientific Accomplishments
Over four and a half centuries ago, an Italian physicist and astronomer named Galileo set
the Scientific Revolution in motion, bringing modern science out of ancient natural philosophy.
Galileo Galilei’s had many mathematical and scientific accomplishments. Although he originally
intended to study medicine when he entered university, he changed his course of study to
philosophy and mathematics. Galileo discovered the law of falling bodies. This led to studies on
the motions of projectiles. Another result of his studies was that he realized Aristotle’s
formulation of the principle of inertia was incorrect. His study of the swing of the pendulum led
to his idea for a pendulum clock. Galileo also made his first telescope modeled after telescopes
produced in other parts of Europe. Later, he created a telescope that could magnify objects
twenty times. He used his telescope to make discoveries in outer space that supported the
Copernican system.
Some of his astronomical achievements include discovering a full set of phases of the
planet Venus. This helped prove the heliocentric concept of the solar system first developed by
Copernicus. While observing Saturn, he identified the rings as planets in their own right.
Thinking it was a triple-planetary system, he noticed that the rings would appear and disappear
depending on the time in which he was observing them. Galileo also was one of the first people
to observe sunspots. Using his telescopes, he was able to identify that the Moon had mountains
and craters, dispelling the belief that it was a perfect sphere. Galileo also found that the Milky
Way was actually close-packed stars rather than some sort of nebula. He was able to locate a
number of stars previously unseen with the naked eye. According to his notes, he observed the
planet Neptune in 1612, but did not recognize it as a planet. He thought it was simply another
dim star.
Explanation of Galileo’s Law of Parabolic Fall
The Law of Parabolic Fall states that the distance traveled by a falling object is directly
proportional to the square of the time it takes to fall.
Example: A stone falling for twice as long as another stone will travel four times the distance.
Example: A ball falling for three seconds will travel nine times the distance traveled by a ball
falling for one second.
The formula for the law of fall is:
In the time period before Galileo, scientists thought that force causes speed. Galileo
showed that force causes acceleration. Galileo reached the conclusion that objects fall on the
surface of the Earth at a constant acceleration, and that the force of gravity which causes all
objects to move downward is a constant force. In other words, constant force does not lead to
constant speed but to constant acceleration. Galileo claimed that an object in motion will
continue its motion, so long as no factor disturbs that motion. This is called the principle of
inertia.
Contrary to the claims of the natural philosophers of his period, Galileo claimed that a
body will not attain a certain speed which will remain constant but will continue accelerating
until it comes into contact with the ground. This claim is of course true so long as one ignores air
resistance, which can be very significant for certain objects and at high speeds.
An example of the Law of Parabolic Fall is:
A falling ball, in the 2nd second of its fall, will travel a distance three times as great as the
distance it traveled during the 1st second; in the 3rd second it will travel a distance five times
that of the 1st second; in the 4th second it will travel a distance seven times that of the 1st
second.
If during the 1st second, the ball traveled a distance of 10 cm, it will travel a distance of 30 cm
during the 2nd second, of 50 cm during the 3rd second, 70 cm during the 4th second, and so on.
Equation:
Most Interesting Fact
The most interesting fact that I found was about Galileo and the Inquisition. One of the
most important events in Galileo’s life was when he battled with the Catholic Church. Galileo
believed in Copernicanism, the theory that the Earth and other planets revolved around the sun.
Galileo was found guilty of heresy in court and sentenced to be under house arrest. He also had
to denounce the theory of Copernicanism in front of the Catholic Church, and was forbidden to
publish his works. What I found interesting was that in 1990, a number of influential church
figures started to make speeches about Galileo and his persecution. On February 15, Cardinal
Ratzinger questioned the politics of the Church during Galileo’s time, but did not make a formal
apology. Pope John Paul II expressed regret for the actions taken by the Church during Galileo’s
time. He did this on October 21, 1992. Lastly, Pope Benedict CVI praised Galileo for his
contributions to the fields of astronomy and physics.
I thought it was fascinating that the Catholic Church never made a formal apology. I
believe that the Church does not want to admit it was in the wrong, because that would be a sign
of weakness against science in today’s time.