The Galileo affair Italian : il processo a Galileo Galilei began around , [ 1 ] and culminated with the trial and condemnation of Galileo Galilei by the Roman Catholic Inquisition in Galileo was prosecuted for holding as true the doctrine of heliocentrism , the astronomical model in which the Earth and planets revolve around the Sun at the centre of the universe. In , Galileo published his Sidereus Nuncius Starry Messenger , describing the observations that he had made with his new, much stronger telescope , amongst them, the Galilean moons of Jupiter.
With these observations and additional observations that followed, such as the phases of Venus , he promoted the heliocentric theory of Nicolaus Copernicus published in De revolutionibus orbium coelestium in Galileo's opinions were met with opposition within the Catholic Church, and in the Inquisition declared heliocentrism to be "formally heretical". Galileo went on to propose a theory of tides in , and of comets in ; he argued that the tides were evidence for the motion of the Earth.
In , Galileo published his Dialogue Concerning the Two Chief World Systems , which defended heliocentrism, and was immensely popular. Responding to mounting controversy over theology , astronomy and philosophy , the Roman Inquisition tried Galileo in , found him "vehemently suspect of heresy ", and sentenced him to house arrest where he remained until his death in The affair was complex since very early on Pope Urban VIII had been a patron to Galileo and had given him permission to publish on the Copernican theory as long as he treated it as a hypothesis, but after the publication in , the patronage was broken off due to numerous reasons.
Galileo began his telescopic observations in the later part of , and by March was able to publish a small book, The Starry Messenger Sidereus Nuncius , describing some of his discoveries: mountains on the Moon , lesser moons in orbit around Jupiter , and the resolution of what had been thought to be very cloudy masses in the sky nebulae into collections of stars too faint to see individually without a telescope.
Other observations followed, including the phases of Venus and the existence of sunspots. Galileo's contributions caused difficulties for theologians and natural philosophers of the time, as they contradicted scientific and philosophical ideas based on those of Aristotle and Ptolemy and closely associated with the Catholic Church. In particular, Galileo's observations of the phases of Venus, which showed it to circle the Sun, and the observation of moons orbiting Jupiter, contradicted the geocentric model of Ptolemy , which was backed and accepted by the Roman Catholic Church, [ 7 ] [ 8 ] and supported the Copernican model advanced by Galileo.
