Galileo Galilei was the first astronomer to use a telescope to study the heavens. Galileo made a number of observations that finally helped convince people that the Sun-centered solar system model (the heliocentric model), as proposed by Copernicus, was correct. These arguments can be divided into two kinds: Those that proved that the Ptolemaic model was incorrect and those that undermined the broader philosophy of Aristotelianism that included the Ptolemaic model. We'll first consider some philosophically important observations and then the ones that pro
