The Corrected and Improved Copernican Theory of the World
After students of optics had invented the telescope in this century, the truths of the old Pythagorean and Copernican theories became much clearer than before. For once again they served as a firm foundation for these investigations and opened a wide field for discovery and speculation. At this time, Galileo Galilei, a professor at the University of Pisa and the astute mathematician of the Grand Duke of Tuscany, discovered in the year 1610, with his famous telescope, the four moons around Jupiter, which were called the satellites of Jupiter or the Medici stars after the city of the Medici where they were first discovered. Simon Marius, the first of the Germans to observe them, called them the Brandenburg stars (because the margraves of Brandenburg were his lords and he received their patronage).