Before Galileo, science was not considered a profession. Typically, people who did 'science' were considered natural philosophers and held positions as medical doctors, mathematicians or priests with extra time on their hands. The name philosopher was typically used because it was just as likely for someone to explain a phenomenon by what they believed happened through other philosophies or their own ideas as easily as their own observations.
Galileo was one of the first to break away from Aristotle's four terrestrial elements of earth, air, fire and water with a new basic element of corporeal matter. He was the first to express the belief that the basic laws of science could be broken down into mathematics. He was among the first to take a closer look at the skies above with a telescope.
His life is generally used as the beginning point of the history of modern science. His philosophy of observe first, explain second and observe some more would become the foundation of the modern scientific method. Find out what else occurred on this day in science history.