Because he was so open about his ideas and theories, he was persecuted by the Catholic Church. He then told everyone that he just made it up and it wasn't real, little did he know that we would later find out that he was 100% correct.
An Interesting fact about him: Galileo was sent to a Jesuit monastery to study medicine. But after four years he announced his calling: to be a monk. His father withdrew him, but not before Galileo joined the order, making him a defrocked priest for life.