Aristarchos or Aristarchus of Samos fl.270BC
Greek astronomer

He worked in Alexandria, Egypt, and is famous for his theory of the motion of the Earth, maintaining not only that the Earth revolves on its axis but that it travels in a circle around the Sun, anticipating the theory of Copernicus. He was also a practical astronomer and developed a method for determining the relative distances of the Sun and Moon. His result, though greatly in error due to the crudeness of his method, was the first attempt to make this important observation. He inferred correctly that as the Sun and Moon are almost of the same apparent size, their dimensions are in proportion to their distances.