Galileo was born during the renaissance in Pisa, Italy on February 15, 1564. He was raised by his mom, Giulia Ammanati, and his dad, Vincenzo Galilei. His family had enough money for school, but they were not rich. When he was about seven years old, his family moved to Florence where he started his education. In 1581, his father sent him to the University of Pisa because he thought his son should be a doctor. For four years, he studied medicine and the different theories of the scientist Aristotle. He was not interested in medicine, but soon he became interested in math. In 1585, he convinced his father to let him leave the school without a degree.
Galileo was a math tutor for the next four years in Florence. He spent a lot of the four years studying the scientific thoughts and philosophies of Aristotle. He also invented an instrument that could find the gravity of objects. This instrument was called a hydrostatic balance. It worked by weighing objects in water to find their gravity.
Galileo returned to Pisa in 1589 and became a professor in math. He taught courses in astronomy at the University of Pisa, based on Ptolemy's theory that the sun and all of the planets move around the earth. Teaching these courses, he became more understanding in the workings of astronomy. .
In 1592, the University of Padua gave him a professorship of math. He stayed at that school for eighteen years. He learned and believed Nicholas Copernicus's theory that all of the planets move around the sun. He also made a mechanical tool called a sector. This tool explained the tides based on Copernican theory of motion of earth. He also found that the Milky Way was made up of many stars, and told people that machines cannot create power, they can only change it.