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Wednesday, 18 March 2015

Galileo Galilei


Galileo was born in Pisa (then part of the Duchy of Florence), Italy, on February 15, 1564. He was the first of six children of Vincenzo Galilei and Giulia Ammannati.

His real name was Galileo Galilei but like Saladin, Prince and Madonna he is generally known by his first name.

Galileo’s father Vincenzio Galilei was a professional singer and lutenist who also dabbled in cloth to make ends meet. He worked as a wool trader in order to make enough to money to attain the aristocratic lifestyle desired by his wife. Vincenzio died in 1591.

Galileo's mother was Giulia degli Ammannati. An aristocratic, shrewish demanding woman, she was dissatisfied with her middle- class financial status, and ever resentful of Vincenzo's failure to rise above his lower-class origins.

As a teenager, Galileo's favourite hobby was making mechanical toys.

Galileo was educated by monks at the Jesuit Monastery School of Vallombrasa, twenty miles east of Florence, where he received a full education in the humanities.

The scholarly bent of the community appealed to Galileo, and in his fourth year at Vallombrosa, he informed his father that he intended to become a monk. His father, who had never held the Church in great esteem, responded by withdrawing him from the monastery and formulating a new plan for his education. For a time Vincenzo taught him personally Latin, Greek, Logic and Mathmatics.

Vincenzo decided that Galileo would enrol at Pisa University, while receiving training in the wool business from a cousin, as a university education did not guarantee financial success.

A failed Medical Student at Pisa University between 1581-85, Galileo sought refuge from the monotony of the lecture theater with a barrage of questions earning himself the sobriquet "The Wrangler."

A lecture on geometry which he'd wandered into by accident kindled Galileo's interest in mathematics and he got his father's consent to switch courses. Though he continued to formally pursue a degree in medicine, Ostilio Ricci, the court mathematician educated Galileo in Geometry and Applied Mathematics in Florence. Galileo left the university in 1585 without a degree.


During his student days Galileo's observation of a swinging lamp in Pisa Cathedral led him to discover the uniformity of the pendulum. Late in his life, when totally blind, Galileo designed an escapement mechanism for a pendulum clock. Galileo's work enabled his friend, the Dutch scientist Christiaan Huygens, to construct the first pendulum clock in 1656.

Galileo tutored privately on mathematical subjects in Siena and Florence between 1585 and 1589 and wrote on hydrostatics, but he did not publish anything.

Galileo's father performed musical experiments on the relationship between the tension and pitch of strings in 1588, when his son was living at home and giving private lessons in mathematics. It is thought that 24-year-old Galileo helped in the experiments.

Galileo was offered the position of Professor of Mathematics at Pisa University in 1589. It was there that he reportedly made his famous velocity experiment, dropping objects off the leaning tower to disprove Aristotle's theory that heavier objects fall faster than lighter ones.

During his three years in Pisa, Galileo 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.

After three years at Pisa, Galileo's contract was not renewed, probably because he contradicted Aristotelian professors.

In 1592 he was appointed to the chair of mathematics at Padua University, at the time the premier University in Italy. Galileo served on its faculty teaching geometry, mechanics, and astronomy until 1610. During this time he explored science and made many landmark discoveries.

As a mere mathematics university lecturer, Galileo received 160 scudi per year, 1/30th the salary of a Professor of Medicine. His responsibilities as the head of the family (his father had died in 1591) meant that Galileo was chronically pressed for money.

As Galileo's university salary could not cover all his expenses, he therefore took in well-to-do boarding students whom he tutored privately in such subjects as fortification.

Galileo Galilei. Portrait by Leoni

Galileo also earned some extra cash by selling a proportional compass, or sector, of his own devising suitable for use by gunners and surveyors. It was made by an artisan whom he employed in his house.

Galileo built the first thermoscope in the late 1590s. A primitive gas thermometer, the thermoscope used a well known principal that air expands as it is heated . He used water in a thin glass tube with a bulb on top with markings etched on to the tube.

Galileo also invented an automatic tomato picker and a pocket comb that doubled as an eating utensil.

In August 1599 Galileo was rewarded with a new, six-year contract, retroactive to December 1598, with a salary of 320 ducats doubling of his salary. This meant he was now one of the highest-paid professors at the university.

One of his students at Padua University in the early 1600s was a certain William Harvey, who was to be the first to explain how blood was moved through the body by the heart.

Galileo left Padua for good in 1610 to take up a position of Mathematician and Philosopher to Grand Duke of Tuscany at the Medici court in Florence.

Galileo advocated strongly that science should be communicated when written down in the language of the common people and not Latin. He wrote most of his later works in the vernacular to distance himself from the conventional learning of University teachers. However his books were translated into Latin for the international market.

Galileo was one of the first modern thinkers to clearly state that the laws of nature are mathematical, showing a remarkably modern appreciation for the proper relationship between mathematics, theoretical physics, and experimental physics.

He revolutionized scientific thought by encouraging an experimental scientific method rather relying on belief and superstition. Galileo perhaps more than any other single person was responsible for the birth of modern science.


While in Venice, Galileo learned in 1609 of the recent invention of the telescope which had been developed for military applications. After returning to Padua, he developed an improved version, the first one powerful enough to be used for astronomical observation. He went back to Venice and demonstrated his eight-power telescope to Venetian lawmakers on August 25, 1609.

19th-century painting depicting Galileo Galilei displaying his telescope in 1609.

Galileo's development of the telescope was criticized by the church as it was considered sacrilege to direct a look at God’s Heaven.

Galileo first used his telescope to observe Jupiter's four largest moons on January 7, 1610. His observations over the following six days caused a revolution in astronomy: a planet with smaller planets orbiting it did not conform to the principles of Aristotelian cosmology, which held that all heavenly bodies should circle the Earth.

Angling for Medici patronage, Galileo named the group of four Jupiter moons, the Medicean stars, in honor of Cosimo II de' Medici, Grand Duke of Tuscany, and Cosimo's three brothers. Galileo's toad like behavor bore fruit when within months he had been appointed Grand Ducal Mathematician in Florence with one of the top ten stipends paid to government officials - a salary of One Thousand Florentine Crowns a year. Galileo was now a courtier and lived the life of a gentleman.

Later astronomers, however, renamed the moons Galilean satellites in honor of their discoverer. These moons are now called Io, Europa, Ganymede, and Callisto.

Galileo Galilei became the first astronomer to observe the planet Neptune on December 28, 1612. It appears Galileo mistook Neptune for a fixed star when it appeared close—in conjunction—to Jupiter in the night sky.


Galileo's Dialogue On Two Chief World Systems was dedicated to his patron, Ferdinando II de' Medici, Grand Duke of Tuscany, who received the first printed copy on February 22, 1632. The book updated Copernicus' theories about the Earth going around the Sun. It was written in Italian, the language of the people rather than Latin, the language usually used for scholarly debate.

Frontispiece and title page of the Dialogue, 1632


During one of his frequent trips to Venice, Galileo met a good-looking young woman named Marina di Andrea Gamba, with whom he entered into a relationship, which lasted eighteen years.

Marina moved into Galileo's house in Padua and bore him three children out of wedlock, Virginia (1600), later Sister Maria Celeste, Livia (1601), later Sister Arcangela, and Vincenzio (1606). The domestic situation was, apparently, a happy one, except when Galileo's mother, Giulia, visited.

When Galileo left Padua for good to take up his position at the Medici court in Florence, in 1610, he took his two daughters with him but left Marina Gamba behind with Vincenzio, who was then only four-years-old. Vincenzio joined Galileo in Florence a few years later. Vincezio later became a lawyer in Florence.

In 1613 Marina Gamba married Giovanni Bartoluzzi. It appears that Galileo kept cordial relations with Gamba and Bartoluzzi.

Virginia and Livia were farmed off to a convent as soon as they were grown up. His eldest daughter took the name Sister Marie Celeste and lived in a nearby nunnery.

The most beloved of his children, Sister Marie Celeste inherited her father's sharp mind. She remained at the nunnery until  her untimely death in 1634. This dealt a heavy blow to Galileo, and he sank into a deep depression for months afterwards.

After surviving a bout of financial trouble in early 1593, when the demands of his family and particularly his sister's dowry almost overwhelmed him, Galileo prospered, and eventually moved from a small cottage into a larger three-story house. The house's grounds included a walled garden where he often entertained students and other guests.

Galileo was fond of good food, for treats his nun daughter Sister Marie makes him marzipan shaped like little fish.

He enjoyed music from his teenage years onwards, Galileo especially  had a talent for the lute (his father's instrument).


A devout Catholic, in his teens, Galileo had considered joining the order of the monastery of Santa Maria di Vallombrasa.

In 1632 Galileo published Dialogue on Two Chief World Systems, which updated Copernicus’ theories about the Earth going around the Sun and ridiculed the position taken by the church. Galileo's position on the relationship of discovered truth in nature to revealed truth in the Bible, was in his view perfectly compatible with his Catholic faith. The devout scientist argued “ I do not feel obliged to believe that the same God who has endowed us with sense, reason and intellect has intended us to forgo their use.”

The following year, The Inquisition summoned Galileo to Rome where he was cross-examined and threatened with torture. The Roman Catholic Church argued "The doctrine that the Earth is neither the centre of the Universe, nor immovable, but moves, even with a daily rotation is absurd and both philosophically and theologically false and the least an error of faith."

Cristiano Banti's 1857 painting Galileo facing the Roman Inquisition

On June 22, 1633 the 69-year-old Galileo recanted under pressure from the Holy Office and was sentenced to house arrest for his last years. After his revocation Galileo was heard to mutter under his breath “Eppur si moove” (“But still it moves”).

Originally excommunicated, Galileo was later in his life given permission to attend church on religious holidays provided he has no contact with others.

In 1992 Pope John Paul II admitted the Roman Catholic Church had erred in condemning Galileo, thirteen years after he appointed a commission of philosophers, scientists and theologians to investigate the evidence of the Italian's controversial discoveries.


Galileo was never actually in a dungeon or tortured during the Inquisition process. He stayed mostly at the house of the Tuscan ambassador to the Vatican and for a short time in a comfortable apartment in the Inquisition building.

When the Inquisition summoned Galileo to Rome in 1633, he arrived in a litter that the Grand Duke of Tuscany (his patron) had placed at his disposal.

When Galileo was under house arrest he suffered from a painful hernia. He requested permission from the Vatican to consult physicians in Florence. The request was denied and Galileo was informed that any similar requests would result in imprisonment.

After the Inquisition process was completed later in 1633, Galileo lived out the remainder of his life in his small villa in the hilltop village of Arcetri in the hills above Florence.

While Galileo technically remained a prisoner, forbidden to stray beyond the villa's grounds, his wardens still permitted him to teach pupils, pursue his studies, and receive visitors. His visitors included two great Englishmen,  the philosopher Thomas Hobbes and the poet John Milton, who made the pilgrimage in 1638.

Galileo irreversibly damaged his retinas by looking at the sun and its sunspots for too long and by the age of 74, cataracts had robbed him completely of sight. He was attended at his Florence villa by a number of young men, who read to him, and to whom he dictated his correspondence.

In constant pain from arthritis, which had affected  him since the 1590s, when he was without company Galileo occupied himself by playing the lute.

Galileo died peacefully in his sleep at his villa in Arcetri on January 8, 1642. His grave is at the Church of Santa Croche, Florence in the family tomb. (He was denied a church burial).

Tomb of Galileo, Santa Croce, Florence. By stanthejeep, Wikipedia

In 1737 an admirer cut off three  of Galileo's fingers as keepsakes. One of them, the middle finger from Galileo's right hand, now resides at the Museo Galileo in Florence,

Sources Encyclopedia Britannica, Food For Thought by Ed Pearce

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