ARISTARCHUS OF SAMOS

(c. 310230 BC), Greek astronomer, first to maintain that the Earth rotates and revolves around the Sun. On this ground, Cleanthes the Stoic declared that he ought to be indicted for impiety. Aristarchus' advanced ideas on the movement of the Earth are known from Archimedes and Plutarch; his only extant work is a short treatise, On the Sizes and Distances of the Sun and Moon. The values he obtained, by using geometry, are inaccurate, because of faulty observations. Aristarchus found a more precise value for the length of the solar year. A lunar crater is named for him; a peak in its centre is the brightest formation on the Moon.