Galilee was born in Pisa on February 15th, 1564. He later moved with his family to Florence where he began his education at a monastery. He went to the University of Pisa in 1581 where he studies medicine and the philosophy of Aristotle. There he discovered he had a talent for mathematics. In 1585 he left the university, moved back to Florence, and became a math tutor. Around the same time that he began to question Aristotelian philosophy, he was recognized for the first time because of his new hydrostatic balance (an instrument which weighs objects in water in order to find its specific gravity). He later became a professor which required him to teach the Ptolemaic theory of astronomy. In turn, he also came to side with Copernicusís heliocentric theory.
After building his own telescope and realizing that not only were Ptolemy and Aristotle wrong in that the Earth was the center of the universe, they were also wrong when they said the moon was flat. At this time he also noticed that Jupiter had four moons which he named them the "Medician Planets" (hoping to find the favor of the Medicis, the ruling family of Florence).
Throughout his career, Galilee continued making more observations which helped support Copernicusís theory. As these observations continued, the Aristotelian Theory of Motion made even less sense and Galileo set out to develop a new theory.
His greatest achievements include discovering important new facts about astronomy with the help of the refracting telescope while improving it, discovering the laws of falling bodies and the law of pendulum, and designing a variety of scientific instruments.
In 1613 Galileo wrote a letter trying to show that the Copernican theory was consistent with both Catholic doctrine and proper biblical interpretation. A copy of this was sent by some of his enemies that he earned with his quick wit to the inquisitors of Rome. In 1616 he was then summoned to Rome and was cleared of charges of heresy he was ordered not to continue to defend the Copernican theory.
In 1632 he published the Dialogue Concerning the Two Chief World Systems in which he showed that the Copernican system was logically better and was once again summoned to Rome. He was forced to take back his statements and was sentenced to life imprisonment. Due to his old age and poor health he served this sentenced under house arrest in his villa in Florence. In this time he finished his second masterpiece Discourse on Two New Sciences in which he provided both an original study of the tensile strength of materials and a mathematical proof of his new theory of motion. He died in 1642, after nine years of house arrest.