In 1543, Polish astronomer Nicolaus Copernicus published "On the Revolutions of the Celestial Spheres," in which he challenged the view that the sun revolved around the Earth, arguing instead that the Earth revolved around the sun. With his new model of the solar system, he began a wide-ranging debate among scientists, theologians, and others. His alternative to the earlier Ptolemaic model, which placed the Earth at the center of the universe, led to a revolution in thinking, and ultimately to a new worldview.