In the mid-16th century Polish astronomer Nicholas Copernicus touched off a revolutionary transformation of thinking about the universe. In 1543 the same man who introduced trigonometry to the world published "Concerning the Revolution of the Celestial Spheres". It was handwritten in Latin. The astronomer saw a copy of his published treatise near the moment of his death. Succinctly, Copernicus introduced the idea of Earth as a revolving planet that orbited the Sun. Before him, for more than a thousand years, celestial observers had accepted the Greek astronomer Ptolemy's theory. He held that the Earth is unmoving and entirely stationery. Ptolemy believed that the Sun and the other planets of the solar system revolved around Earth.