A pupil of Strato of Lampsaco, he lived presumably somewhere between 310 and 230 B.C. In the only work of his which has come down to us, the De magnitudinibus et distantiis solis et lunae, he attempted to measure the size of the sun and moon and their respective distances from the earth. His calculations were not exact but were utilized by astronomers over the centuries, up to modern times. From what Archimedes (287-212 B.C.) says in his Arenarius, Aristarchus championed a heliocentric theory: the earth rotated upon itself in the course of each day and in the course of each year revolved around a motionless sun, together with the fixed stars, in the center of the universe. To those who objected that with an earthly rotation the fixed stars would have to appear in different positions during the course of a year, he answered by conjecturing a distance between them and the earth infinitely greater than the radius of its orbit around the sun.

But it seems that the objections against Aristarchus were not limited to scientific grounds. We read in Plutarch's De facie in orbe lunae (ca. 46-127 B.C.) that the stoic Cleanthes pressed the Greeks to try Aristarchus for irreverance in disturbing the earth's tranquillity. And perhaps it is owing to religious prejudice that, after the demise of Seleucus of Seleucia (2nd cent. B.C.) in Mesopotamia, none of the ancient astronomers followed up on Aristarchus' carefully-argued heliocentrism.