Galileo was not the person who invented the telescope, but he was the first one to use the telescope to study the heavens. He made many observations using the telescope that shocked the religious world. In this short essay, I will only focus on three observations and how an Aristotlean reacts to it. These observations played a very important role on the development of astronomy. The first object he observed was the moon. Through his observations he concluded that the moon’s surface was very irregular and imperfect. He saw that the moon’s surface had mountains and valleys. It also consists of many other irregular shapes. This was a very big contradiction to Aristotle’s th