<P> A more conventional picture was that supported by Hicetas, Heraclides and Ecphantus in the fourth century BCE who assumed that the earth rotated but did not suggest that the earth revolved about the sun . In the third century BCE, Aristarchus of Samos suggested the sun's central place . </P> <P> However, Aristotle in the fourth century BCE criticized the ideas of Philolaus as being based on theory rather than observation . He established the idea of a sphere of fixed stars that rotated about the earth . This was accepted by most of those who came after, in particular Claudius Ptolemy (2nd century CE), who thought the earth would be devastated by gales if it rotated . </P> <P> In 499 CE, the Indian astronomer Aryabhata wrote that the spherical earth rotates about its axis daily, and that the apparent movement of the stars is a relative motion caused by the rotation of the Earth . He provided the following analogy: "Just as a man in a boat going in one direction sees the stationary things on the bank as moving in the opposite direction, in the same way to a man at Lanka the fixed stars appear to be going westward ." </P> <P> In the 10th century, some Muslim astronomers accepted that the Earth rotates around its axis . According to al - Biruni, Abu Sa'id al - Sijzi (d. circa 1020) invented an astrolabe called al - zūraqī based on the idea believed by some of his contemporaries "that the motion we see is due to the Earth's movement and not to that of the sky ." The prevalence of this view is further confirmed by a reference from the 13th century which states: "According to the geometers (or engineers) (muhandisīn), the earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to the motion of the earth and not the stars ." Treatises were written to discuss its possibility, either as refutations or expressing doubts about Ptolemy's arguments against it . At the Maragha and Samarkand observatories, the Earth's rotation was discussed by Tusi (b . 1201) and Qushji (b . 1403); the arguments and evidence they used resemble those used by Copernicus . </P>

Who discovered that the earth rotates on an axis