We know very little about Aristarchus’s work, besides On Sizes and his proposal of a heliocentric doctrine. . . . Although the daily rotation of the Earth is only inferred from Archimedes’s text, it is confirmed by a reference in Plutarch (De facie in orbe lunae, c. 6, 922F–923A; 1957:55) which makes it explicit. According to Plutarch, Cleanthes suggested that Greeks ought to lay an action for impiety against Aristarchus for

setting the home of the universe in motion because he thought to save [the] phenomena, by assuming that the sky remains at rest and the Earth revolves in an oblique circle while rotating, at the same time, on its own axis.

Indeed, we know that Cleanthes is the author of a book titled Against Aristarchus. Also, Aetius (II, 24.8; Diels 1879:355) tells us that Aristarchus placed the Sun in the middle of the fixed stars and set the Earth in motion around the solar circle. It is therefore indisputable that Aristarchus of Samos defended some kind of heliocentrism. However, there are no traces of heliocentrism in On Sizes, which seems to assume geocentricism.