Controversy over heliocentrism

At the time of Galileo's conflict with the Church, the majority of educated people subscribed to the Aristotelian geocentric view that the Earth is the centre of the Universe and the orbit of all heavenly bodies, or Tycho Brahe's new system blending geocentrism with heliocentrism.[124][125] Opposition to heliocentrism and Galileo's writings on it combined religious and scientific objections. Religious opposition to heliocentrism arose from biblical passages implying the fixed nature of the Earth.[e] Scientific opposition came from Brahe, who argued that if heliocentrism were true, an annual stellar parallax should be observed, though none was at the time.[f] Aristarchus and Copernicus had correctly postulated that parallax was negligible because the stars were so distant. However, Brahe countered that since stars appear to have measurable angular size, if the stars were that distant, they would have to be far larger than the Sun or even the orbit of the Earth.[128] It would not be until much later that astronomers realized the apparent magnitudes of stars were caused by an optical phenomenon called the airy disk, and were functions of their brightness rather than true physical size (see Magnitude#History).[128]
Galileo defended heliocentrism based on his astronomical observations of 1609. In 1611, the same year Galileo’s telescopic discoveries were acknowledged by Jesuit members of the Collegio Romano, a commission of cardinals began investigating Galileo, inquiring if he had been involved in the trial of Cesare Cremonini, who had taught alongside Galileo at the University of Padua and had been charged for heresy. These inquiries marked the first time Galileo’s name was mentioned by the Roman Inquisition.[129]