Aristarchus of Samos, fl. c.310 B.C.-c.230 B.C., Greek astronomer and mathematician of the Alexandrian school. He is said to have been the first to propose a heliocentric or sun-centered theory of the universe. Of his writings only a treatise, The Sizes and Distances of the Sun and Moon, remains. The procedures he followed in this treatise were highly original; his calculation of the moon's distance was incorrect, but he derived a more correct value for the solar year. The treatise does not mention his conclusion that the earth moves around the sun and that the sun is at rest, but statements by Archimedes and Copernicus indicate that he held this theory. Other conclusions in which he seems to have anticipated later scientists are that the sun is larger than the earth, that the earth rotates upon its axis causing day and night, and that its axis is inclined to the plane of the ecliptic, causing the change of seasons.

(born circa 310 BC—died circa 230 BC) Greek astronomer. His advanced ideas on the movement of the Earth (which he asserted revolved around the Sun) are known from Archimedes and Plutarch. His only surviving work is the short treatise “On the Sizes and Distances of the Sun and Moon”; though the values he obtained are inaccurate, he showed that the Sun and stars are at immense distances. A peak in the centre of a lunar crater named for him is the brightest formation on the Moon.

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