Galileo Galilei was born on February 15th, 1564 in Pisa, Italy. He was the oldest son of Vincenzo Galilei, a musician who made important contributions to the theory and practice of music
In 1581, Galileo started studying at the University of Pisa. He was originally supposed to study medicine, but decidedinstead to pursue math and philosophy
Around 1589, Galileo dropped things of different weights off of the Leaning Tower, proving that that the speed of fall of a heavy object is not proportional to its weight.
In 1609, Galileo created a telescope that magnified up to 20 times what it normally did. He was able to discover that Jupiter had four moons, and that Saturn had a puzzling appearance. He also discovered many more stars then the ones that were visible to the naked eye. He wrote a book and dedicated it to Cosimo II de Medici, whom he had tutored.
A few year later, Galileo entered a debate with Cristoph Scheiner, a professor of mathematics at Ingolstadt. They argued about the nature of sunspots, with Galileo had also found.
Galileo believed in Copernicanism, or the belief that the sun is the center of our solar system and the other planets revolve around it. It became increasingly harder to spread the word about it, as he was told to not to teach, hold, or defend it. He believed this until he died on January 8th, 1642