Claudius Ptolemy
Egyptian astronomer and geographer Ptolemy, a.k.a. Claudius Ptolemaeus (c. 90 - 168), worked and studied at Alexandria between about 146 and 170CE.
His highly influential astronomical text in thirteen books (Megiste in Greek, Almagest in Arabic) used carefully selected observations to develop theories and tables describing the positions of the sun, the moon, the five planets and the fixed stars.
Ptolemy placed the earth at the centre of the universe with the other heavenly bodies revolving around it. His clear and orderly exposition of the visible universe became canonical. It dominated astronomical theory in Byzantium, the Islamic world, and medieval Europe for over a millennium.
Geographike Hyphegesis (a.k.a. Geographia or Geography) in eight books reworked now-lost works by Marinos of Tyre into a comprehensive catalogue of almost nine thousand locations in the oikoumene, with latitude and longitude for each.
He was the first to devise a projection representing a portion of the spherical earth on a plane surface and to orientate his maps with the north uppermost, the east on the right and the west to the left.
Other works dealt with optics, the musical scale, chronology and astrology.
Above: Ptolemy with an armillary sphere model (Joos van Ghent and Pedro Berruguete, 1476; original painting in the Louvre, Paris); Public domain; Wikimedia Commons.)
