Ancient astronomers originally put forth the theory that the Sun was the center of our solar system, and that the planets revolve around it. This knowledge was lost during the Dark Ages, but was re-introduced in the early 16th Century by Nicholas Copernicus. Copernicus' research and theories form the foundation for modern astronomy. Copernicus collected his data from his observatory, a small room in the spire of an East Prussian cathedral. His research methods and observations also marked the rebirth of the scientific method, and were an important step in the advance of knowledge.