Searching for a higher salary, Galileo traveled to Venice where he became head of the mathematics department of the University of Padua, earning three times more money than previously. It was at this university that he would become a devote Copernican and begin his work with telescopes. By the end of 1609 he had made incredible discoveries: he was able to observe Jupiter's moons and saw the Milky Way was made up of stars. These discoveries lead him to publish the Starry Messenger the following year. Starry Messenger and his work with telescopes brought him to celebrity status. .
While working on calculations for his astronomical observations, Galileo came upon a serious problem: all of his calculations assumed a geocentric universe. Because of this, some of his calculations did not work. After adjusting his numbers to a heliocentric universe, all of the calculations worked. This prompted Galileo to become certain that the earth was in fact moving around the sun. He did not make any public assertions yet and largely kept his opinions to himself. .
A former student of Galileo's, Antonio Castelli was a devout Copernican and pulled Galileo into the controversy between which model of the universe of correct. At this time, many scientists accepted Copernicus's universe as a good mathematical model for predicting movement of heavenly bodies. The consensus however was that Earth was actually at the center of the universe. Even before Galileo made public statements for a heliocentric universe, it was already a discussed and controversial topic. .
The controversy stems from a biblical passage in the Old Testament. The passage speaks about Joshua, a follower of God being able to stop the sun in the sky. Many people in Galileo's time interpreted this as evidence that the sun was going around the Earth. The passage reads:.
"On the day The Lord gave the Amorites over to Israel Joshua said to The Lord in the presence of Israel: "O sun, stand still over Gibeon, O moon, over the Valley of Aijalon.
