Galileo Galilei was born in Pisa on February 15, 1564. He was the oldest son of Vincenzo Galilei. His father was a musician. In the 1570's, his family moved to Florence, Italy, where he attended a monastery school. Later, he attended the University of Pisa. He planned to study medicine but then decided to pursue mathematics and philosophy, especially the philosophy of the Greek philosopher Aristotle.
He left the university before he earned a degree. For several years, he gave private lessons in mathematics. During this time, he invented a balance for weighing small quantities. He also began to study motion which he continued to do for many years.
In 1588, he did not win a position at the University of Bologna. However, later that year, he was asked to deliver a paper at the Florentine Academy on the arrangement of the world in Dante's Inferno. Because of his work on gravity, he was noticed by Guidobaldo del Monte who helped him obtain a position in mathematics at the University of Pisa.
At the Leaning Tower of Pisa, Galileo conducted the famous experiment where he dropped two objects of different weights from the top of the tower. He wanted to prove that the speed of an object is not related to its weight. This experiment refuted (termed wrong) the theories of the Greek Aristotle whom Galileo had followed before. Many scientists attacked his new theory and his move away from the theories of Aristotle, and he was dismissed from his position at the University of Pisa.
Because of his patrons, those who believed in his work, he was able to find a position at the University of Padua, where he taught from 1592-1610. Although his salary was higher in Padua, he still did not have enough money to support the family because his father had died in 1591. Therefore, he took in boarding students whom he tutored in fortifications, the building of protective works around a city.
He also designed a compass which was manufactured by someone who lived with him. The sale of this compass brought in more money. He did not marry but had three children with a Venetian woman. He continued research on motion. By 1609, he discovered the Law of Falling Bodies. He stated that all objects, no matter their weight, fall at the same rate of speed. He also discovered that when an object is thrown, its path forms a parabola. It curves upward to a high point and then curves back down.
In 1609, his scientific path turned to wanting to use lenses to make faraway objects appear closer. He showed it to the senate of Venice in 1609 an eight-powered telescope. For this work, his salary was doubled. He was given a lifetime position at the university.
Next, by using his telescope, he discovered the phases of the moon and the appearance of the moon's surface. He found four moons around Jupiter and stars that cannot be seen without a telescope. He returned to his native Pisa in 1610 when he was made the mathematician and philosopher of the Grand Duke of Tuscany.
He had already learned that Saturn had a ring and that Venus goes through phases like the moon. The information about Venus showed that it revolves around the sun. His belief that the sun is the center of the universe was upheld. He also knew that Earth is a planet. In these beliefs, he followed a scientist named Copernicus. Next, he studied what sunspots are. Because of following the theories of Copernicus, Galileo was criticized for many years by the Catholic Church. He was called to Rome in 1633 and sentenced to life in prison. He spent the remainder of his life living near Florence and died in 1642.
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