Nicolaus Copernicus (19 February 1473 – 24 May 1543) was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe. His epochal book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), published in 1543 just before he died, is often regarded as the starting point of modern astronomy and the defining epiphany that began the Scientific Revolution. His heliocentric model, with the sun at the center of the universe, demonstrated that the observed motions of celestial objects can be explained without putting the Earth at rest in the center of the universe. His work stimulated further scientific investigations, becoming a landmark in the history of modern science that is now often referred to as the Copernican Revolution. Among the great polymaths of the Renaissance, Copernicus was a mathematician, astronomer, physician, quadrilingual polyglot, classical scholar, translator, artist, Catholic cleric, jurist, governor, military leader, diplomat and economist. Among his many responsibilities, astronomy figured as little more than an avocation—yet it was in that field that he made his mark upon the world.