Galileo was the genius of his time. He learned the ideas of Nicolaus Copernicus, his notion that the Earth traveled around the sun not that the sun rotated around the Earth. His belief of a heliocentric theory got him into a lot of trouble, such as getting put into house arrest. He had the notion of gravity, he would take cannonballs of all weights and shapes and drop them off of the tower and time their falls. He realized that they fell at the same speeds. He threw some cannonballs and saw that they hit the ground the same time that the ones dropped were hitting the ground. He also experimented with pendulums and inclined planes. His ideas were the seeds of modern science. His ideas were used in later years by Isaac Newton.
He had to appear in front of the Inquisition to answer to his “heretical” ideas. His ideas were contrary to the church at the time so he was to be tried as a heretic. Galileo pleaded guilty to the charge of a heretic and admitted that he had argued the heliocentric theory too aggressively. The pope then has him put under indefinite house arrest in his villa in Arcetri which near Florence, where he spent the remaining years of his life.