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Ptolemaic astronomy, a geocentric model of the universe, was criticized by Nasir al-Din al-Tusi, a 13th-century Persian astronomer. Tusi argued that the Ptolemaic system was overly complex and did not accurately predict the positions of celestial bodies. He proposed an alternative model, known as the Tusi couple, which was simpler and more accurate than the Ptolemaic system. Tusi's work laid the foundation for the development of modern astronomy.