Little is known about Ptolemy's life and education, other that he lived and worked in Alexandria, one of the primary centers of Greek culture in late antiquity, and that he has no genealogical relationship whatsoever to the Pharaoh dynasty bearing the same name (as believed by many in medieval times). He wrote on many topics, including geography, astrology, musical theory, optics, physics, and of course astronomy. He died most probably between 141 and 151 AD.
His landmark astronomical work is his Mathematical compilation, (or Syntaxis, as Prolemy himself referred to it) better known under the name Amalgest, given to it by its later Arabic translators and commentators. By making extensive use of the geometrical constructions known as epicycles and equants, Ptolemy constructed a mathematical model of planetary motion that did far better at predicting planetary positions than anything else produced in antiquity. It is the fusion of Ptolemy's model with the cosmology and physics of Aristotle that was to be adopted in the late antiquity and medieval Western world, and literally define mankind's view of the universe for over a millennium.
Ptolemy was also an accomplished geographer. His maps of Asia and Africa are said to have inspired Christopher Columbus, many centuries later, in his westward expedition to India across the Atlantic.
Toomer, G.J. 1984 (ed. and trans.), Ptolemy's Amalgest, Springer,Porter, R. (ed.) 1994, The biographical dictionary of scientists, Oxford University Press.
-Written and last revised 29 December 1997 by paulchar@ucar.edu.
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