Greek astronomer Aristarchus of Samos was born 310 BC, and died 230 BC He is most famous for devloping a heliocentric model of the solar system.

Short Biography of Aristarchus

Aristarchus of Samos developed his heliocentric model iof the solar system 1700 years before Copernicus. 

Aristarchus was a student at the  Lyceum in Alexandria under Strato, who had headed Aristotle's Lyceum in Athens. The main influence on Aristarchus in  geometery was Euclid. The main successor to Aristarchus in geometry was Archimedes.

Aristarchus was the first person known to believe that the following axioms were true:

1. The rotation of the stars is due to the Earth rotating on its axis. 
2. The earth follows a circular orbit around the Sun. 
3. The Sun is fixed at the centre of the universe, and the stars are fixed in the heavens. 
4. The stars are a vast distance away, otherwise stellar parallax would be easily observed.
5. The Sun is one of the fixed stars.
6. The moon rotates around the Earth.

Some of these axioms are flawed, but axiom 1 is correct and an amazing insight for the time. Axiom 2 is almost correct, but we now know the Earth's orbit is closer to an ellipse than a circle. Axiom 3 is false. The Sun is not fixed at the centre of the Universe--it is just an average star on the outskirts of an average galaxy and nowhere near the centre of anything but the solar-system. Also,  the stars are not fixed in any kind of heaven. Axioms 4, 5 and 6 are correct.

The only treatise of Aristrachus that has survived is On the Sizes and Distances of the Sun and Moon. In this, Aristarchus used Anaxagoras' idea that the Moon reflected sunlight to calculate the distance to the Sun. But he was more of a mathematician than an observational astronomer and did not make the effort to determine when, precisely, the moon was at half phase or determine a good value for the diameter of the moon. So although his mathematical procedure was correct, his figure for the distance to the Sun was an order of magnitude too small. Eratosthenes produced values that were within 2% of today's values.   

Aristarchus' ideas on the movements of the Earth have come down to us from Archimedes and Plutarch.

This biography of Aristarchus  has focussed on his philosophical and scientific views, for a broader and more detailed account you should refer to Encyclopedia Britannica. For an excellent, popular work placing Aristarchus in the history of cosmology try Big Bang by Simon Singh.