Aristarchus of Samos was an ancient Greek astronomer and mathematician who presented the first known model that placed the Sun at the center of the known universe with the Earth revolving around it. He belonged to the so-called Pythagorean school of thought, which sought to understand the universe in terms of geometrical and arithmetical relationships.

Aristarchus' only surviving text is his * Treatise on the Sizes and Distances of the Sun and Moon*. However, largely through the writings of Archimedes (287–212 BC) and Plutarch, Aristarchus is known to have the first proponent of the heliocentric hypothesis, with the Earth ascribed a movement of orbital rotation about the Sun, as well as a daily axial rotation. Aristarchus argued that the lack of observed annual parallaxin the fixed stars could be explained, within his heliocentric model, by assuming that the distance to the fixed stars is very much larger than the size of the Earth's orbit. The very same argument was to be made by Nicholas Copernicus, seventeen centuries later.

Heath, T. 1913,Aristarchus of Samos. The ancient Copernicus,Oxford: Clarendon Press [1997 reprint].Porter, R. (ed.) 1994,

The biographical dictionary of scientists,Oxford University Press