As an influential astronomer, philosopher, and mathematician, Galileo Galilei, also known as Galileo, made many advances in many different areas, but especially in astronomy. Galileo was a professor and the chair of mathematics at Pisa University and later did the same thing at the University of Padua.  He conducted many experiments and trials that furthered knowledge that had to do with mathematics and physics when he was in that position. Galileo also challenged ancient views proposed by famous philosophers and intellectuals such as Aristotle. His fellow professors and peers did not agree with his views, and it made him less popular among them.      Galileo is one of history’s most famous and influential astronomers. He made developments and discoveries that would shape astronomy and set precedents for future astronomers. One of his biggest accomplishments was mapping the phases of the moon, and discovering that the moon’s surface is not smooth, but full of craters and mountains. Galileo also was intrigued by the telescope of that time period, and advanced it so much, that he could see stars that you couldn’t see with the naked eye. He later wrote a book called “sidereus nuncius” which described in detail what he saw. He discovered that venus goes through phases, just like the moon, and was the first to record the appearance of Saturn in detail. At this point, Galileo was a renowned astronomer, and his opinion was respected. Galileo publically converted to Copernicanism, the theory that the sun is the center of the universe and that the earth is a planet that orbits the sun. This was a huge turning point in the scientific revolution.     Conclusion- Galileo Galilei was a pioneer in the field of astronomy. He fought for what he believed was accurate, and did not let the opinion of his peers and colleagues affect his opinion. He made advancements concerning the Sun, stars, Jupiter, the moon, Venus, Saturn, and Mercury. He discovered sunspots, believed that the sun was the center of gravity, and advanced the technology of the telescope. He taught his views to students of all ages, up until the day he died. Galileo’s beliefs impacted the scientific revolution, and also impacted the beliefs of his colleagues. He knew how to defend his opinion, and because of that, he is considered one of the most influential astronomers of all time.      In 1642, Galileo passed away, but his ideas and discoveries are still used and considered today in regards to modern astronomy. Knowledge about the universe would not be as extensive as it is today had it not been for Galileo. He took what little technology he had when he was researching and went a long way with it. Galileo is still respected today as an astronomer, as well as his work. His ideas are renowned and were far ahead of his time. He caused a turning part in the scientific revolution, and went from being looked down upon due to his opinions to being highly respected.