But the time is now ripe, and more than a thousand years after Ptolemy, Copernicus is able to make the leap forward that generations of Indian, Arab, and Persian astronomers had not been able to make: not simply learning, applying, and adding small ameliorations to the Ptolemaic system, but thoroughly improving it—with the courage to change it in depth. Instead of describing heavenly bodies turning around Earth, Copernicus writes a sort of revised and corrected version of Ptolemy’s Almagest, in which the sun is at the center and Earth, together with the other planets, runs around it.
