Copernicus started astronomy on its modern path by making what major change to the models of Ptolemy and Aristotle?

Nicolaus Copernicus revolutionized astronomy by proposing a heliocentric model of the universe, which placed the Sun at the center rather than the Earth. This was a significant departure from the geocentric models of Ptolemy and Aristotle, which posited that the Earth was the center of the universe and that celestial bodies, including the Sun and planets, revolved around it. Copernicus's model not only simplified the explanation of celestial movements but also laid the groundwork for the eventual acceptance of the laws of planetary motion and the development of modern astronomy.