Ptolemy (A.D. c. 90-168) or Claudius Ptolemy [Claudius Ptolemaeus] worked at the Library of Alexandria, Egypt [see map]. His name is a mixture of Greek and Roman ones, so it is thought his family was Greek, probably living in Egypt, that at some point had been granted Roman citizenship. Ptolemy provided the definitive work on geography (known as the Geography) until the Renaissance. He included lines of latitude and longitude. The errors in His geography led to Columbus' errors more than a millennium later. Ptolemy also wrote the Syntaxis, usually called Almagest, on astronomy, which drew on the works of earlier astronomers, including Hipparchus. Ptolemy's astronomy was geocentric, with the sun, moon, and planets going around the earth in circular orbits. Despite its inability to make accurate predictions (because of its errors), it remained the definitive work until the 15th century astronomer Copernicus. Ptolemy also wrote the Tetrabiblos (Four Books), on astrology, and the Optics.
Source: "Ptolemy" A Dictionary of Scientists. Oxford University Press, 1999.
Read more about Ptolemy and other ancient scientists in Discoveries in Science Made by Ancient Greek Scientists.
