ARISTARCHUS OF SAMOS, Greek astronomer, flourished about 270 B.C. He is famous for having been the first to maintain that the earth revolves round the sun. On this ground Cleanthes the Stoic declared that he ought to be indicted for impiety. His only extant work is a short treatise On the Sizes and Distances of the Sun and Moon; here he obtains, by elegant and rigorous geometry, certain results as regards sizes and distances which are only vitiated by the incorrectness of the assumptions, due to the imperfect state of knowledge at the time. The heliocentric hypoth esis does not appear in the treatise, but a quotation in the Are narius of Archimedes from another work of Aristarchus proves that he anticipated the great discovery of Copernicus. Moreover, Copernicus himself was clearly aware of the achievement of Aris tarchus, for he mentioned it in a passage which he afterwards suppressed (see De revolutionibus caelestibus, ed. Thorun., 1873, P. 34 note). Aristarchus added i s 2 3 of a day to Callippus' esti mate of 3651 days for the length of the solar year. He is also said to have invented a hemispherical sun-dial (scaphe).
The Greek text of the extant treatise was first edited by Wallis (1688) ; for a new Greek text with English translation and notes see T. L. Heath, Aristarchus of Samos (1913) .