Aristarchus of Samos, (310?–250? B.C.), a Greek astronomer, believed to have worked in Alexandria, Egypt. His most important idea was that the sun is the center of the universe and the earth revolves around it. Because the science of his day was not advanced enough to furnish evidence for this theory, it was not accepted at that time. The 16th-century Polish astronomer Nicolaus Copernicus, who showed that the sun rather than the earth is the center of the solar system, is thought to have read Aristarchus' writings on the subject.