astronomer. The first to argue that the Earth moves around the Sun,
he was ridiculed for his beliefs.
He was also the first astronomer to estimate (quite inaccurately) the
sizes of the Sun and Moon and their distances from the Earth.
Aristarchus was born on Samos and may have studied in Alexandria, where
he died. Aristarchus' only surviving work is Magnitudes and Distances
of the Sun and Moon. He produced methods for finding the relative distances
of the Sun and Moon that were geometrically correct but rendered useless
by inaccuracies in observation. Aristarchus' model of the universe described
the Sun and the fixed stars as stationary in the cosmos, and the planets
- including the Earth - as travelling in circular orbits around the
He stated that the apparent daily rotation of the sphere of stars is
due to the Earth's rotation on its axis as it travels along its orbit,
and that the reason no stellar parallax
(change in position of the stars)
was observed from one extreme of the orbit to the other is that even
the diameter of the Earth's orbit is insignificant in relation to the
vast dimensions of the universe.