What was the change?
It was the change in which few scholars published work that challenged ideas and replaced old theories with new versions of the theories. It also made more people to think and get involved with astronomy and mathematics. So as these scholars replaced the old assumptions, historians called it the Scientific Revolution.
Who were the people associated with the change?
He became interest in an Old Greek idea about the sun being in the center of the universe. He studied it for 25 years, that he reasoned indeed, the stars, the earth, and the other planets revolving around the sun. Which it was called heliocentric. He did not published his work fast because most scholars and clergy would reject his theories, because it contradicted their religious views.
He continued Brahe's work and included certain mathematical laws. Kepler's laws showed Copernicus's basic ideas were true. It was that the planets did revolved around the sun, and not around the planet, Earth.
He made new theories about astronomy and built his own telescope. He also supported the theories of Copernicus. The church did not like Galileo and his work and the church told everybody to publicly silence and also took him to prison. He discovered that the sun had dark spots on it and that the moon had craters and mountains or hills on it.