<P> There were occasional speculations about heliocentrism in Europe before Copernicus . In Roman Carthage, the pagan Martianus Capella (5th century A.D.) expressed the opinion that the planets Venus and Mercury did not go about the Earth but instead circled the Sun . Capella's model was discussed in the Early Middle Ages by various anonymous 9th - century commentators and Copernicus mentions him as an influence on his own work . </P> <P> The Ptolemaic system was also received in Indian astronomy . Aryabhata (476--550), in his magnum opus Aryabhatiya (499), propounded a planetary model in which the Earth was taken to be spinning on its axis and the periods of the planets were given with respect to the Sun . He accurately calculated many astronomical constants, such as the periods of the planets, times of the solar and lunar eclipses, and the instantaneous motion of the Moon . Early followers of Aryabhata's model included Varahamihira, Brahmagupta, and Bhaskara II . </P> <P> Muslim astronomers often, but not entirely accepted the Ptolemaic system and the geocentric model . </P> <P> Beginning in the 11th century, a tradition criticizing Ptolemy developed within Islamic astronomy, beginning with Ibn al - Haytham of Basra's Al - Shukūk' alā Baṭalamiyūs ("Doubts Concerning Ptolemy"). Several Muslim scholars questioned the Earth's apparent immobility and centrality within the universe . </P>

Who discovered the sun was the center of solar system