Claudius Ptolemy and the Almagest

Abstract

We know of many ancient astronomers. Aristarchus of Samos (310 bc–c 230 bc) was the first to argue for a heliocentric view of the Solar System putting the Sun at the center of the universe. Eratosthenes of Cyrene (c 276 bc–c 195 bc) created the technique of measuring Earth-based locations by using latitudes and longitudes and also accurately computed the circumference of Earth. The calculations of Thales of Miletus (c 624 bc–c 546 bc) allowed him to accurately predict solar eclipses. Aristyllus (c 280 bc), with the help of Timocharis (c 320 bc–c 260 bc), was the first astronomer to create sky catalogs at the astronomical observatory of the library of Alexandria. The observations of Aristyllus and Timocharis are the earliest known Greek observations and can be dated to the year 290 bc But it was Hipparchus of Nicaea that became known as the founder of astronomy.