Galileo Galilei was born on February 15, 1564, in Pisa, Italy. Galileo was the first of seven children of Vincenzio Galilei, a trader and Giula Ammannati, an upper-class woman who married below her class. When Galileo was a young boy, his father moved the family moved to Florence. Galileo moved into a nearby monastery with the intentions of becoming a monk, but he left the monastery when he was 15 because his father disapproved of his son becoming a monk. In November of 1581, Vincenzio Galilei had Galileo enrolled in the University of Pisa School of Medicine because he wanted his son to become a doctor to carry on the family fortune.
Vincenzio thought that Galileo should be able to provide for the family when he died, and his sister would need a dowry soon. Galileo had other plans, and in early 1583 he began spending his time with the mathematics professors instead of the medical ones. When his father learned of this, he was furious and traveled 60 miles from Florence to Pisa just to confront his son with the knowledge that he had been neglecting his studies. The grand duke’s mathematician intervened and persuaded Vincenzio to allow Galileo to study mathematics on the condition that after one year, all of Galileo’s support would be cut off and he was on his own.
In the spring of 1585, Galileo skipped his final exams and left the university without a degree. He began finding work as a math tutor. In November of 1589, Galileo found a position as a professor of mathematics at the university of Pisa, the same one he had left without a degree four years before. Galileo was a brilliant teacher, but his radical ways of thinking and open criticism of Aristotle’s teachings were not acceptable to the other professors at the university. They felt that he was too radical and that his teachings were not suitable.
In 1592, his three-year contract was not renewed. 1n 1592, he landed a job teaching mathematics at the University of Padua with the help of some aristocratic friends. After his father’s death, Galileo supported many relatives (including his brother Michelangelo and his family) and the sum of money he earned as a professor was not nearly enough. He began to tutor on the side to make extra money, including Prince Cosimo, the son of Grand Duchess Christine of Tuscany, which helped Galileo with some of his financial problems.
This was also the year that Galileo met Marina Gamba, whom he never married but had three children with. In 1604, Galileo’s belief he had found a new star – and his conclusion that the Earth was moving- began causing him problems. The Roman Catholic Church was uneasy about this declaration that they were wrong. The Church believed that all the planetary bodies were formed at the beginning of Creation, and that new stars were impossible. In 1609, Galileo heard of a spyglass that had been developed in Holland and quickly constructed one himself – the first telescope of twenty times magnification.
Galileo presented the telescope to the senate of Venice in August of 1609, who were so impressed they doubled his salary and gave him a permanent job at the University of Padua. Galileo used his new device to observe the heavens. He found that the popular belief that the moon was completely smooth was incorrect; for he could see the craters and mountains with his new device. In 1610, he observed four bodies around Jupiter which he concluded to be moons. This was incredible proof against the theory of the time that the earth was the center of the solar system because it was believed that all the planets and our moon revolved around the earth.
Since these four bodies apparently circled Jupiter, this theory was put in question. Also through his telescope, Galileo observed that the Milky Way was made up of thousands of stars and that could not be seen with the naked eye. After observing Earth’s moon and then finding the four moons of Jupiter though his new device, he began to declare that the findings of Aristotle and Ptolemy were wrong. Galileo believed that the geocentric model was incorrect. Through lectures and writings, Galileo said that Copernicus was right – that the earth moved around the sun.
Galileo’s enemies took this declaration and used it against him. They went to the Vatican in Rome and said that these ideas were heresy, because they went against the beliefs of the Church. Of course, the Church sided with Galileo’s accusers and in early 1616, Galileo traveled to Rome to defend his ideas. The Vatican warned him that formal charges were would be pressed unless he abandoned his ideas that Copernicus was correct and that the Roman Catholic Church was wrong. In March of that year, all Copernican theories were banned, but Galileo ignored the warning and continued to talk about his beliefs.
In October of 1632, Galileo was ordered to appear in front of the Inquisition, the court of the Roman Catholic Church. In April of 1633, Galileo went before the court and was ordered to drop all Copernican and heliocentric theories or else he would be torture and executed by burning at the stake for the crime of heresy. On May 10 he admitted in heresy in writing and on June 22 he publicly confessed. He was sentenced to house arrest in his home near Florence for an indefinite length of time. A few months later, Galileo’s beloved daughter, Sister Maria Celeste, died.