Ptolemy - biography.

Ptolemy - biography. Astronomer and mathematician Birth AD 100? Death AD 170? Principal Alexandria, Egypt Residence Known for Proposing an Earth-centered universe consisting of concentric rotating spheres (known as the Ptolemaic system) Career Wrote the Almagest, which proposed his earth-centered astronomical system Compiled Geography, which charts the world as it was known at the time, and includes estimates of longitude and latitude and of the earth's size Studied the properties and behavior of light, and published his conclusions in Optics Published Tetrabiblos, an attempt to create a scientific basis for astrology Studied music, and compiled his observations in Harmonica Did You Know Some scholars doubt the originality of Ptolemy's ideas, believing that he simply repeated the conclusions of ancient astronomers and mathematicians, whose works he had access to in the Library of Alexandria. Ptolemy believed that the earth is a sphere. The Ptolemaic system dominated astronomical thought for well over 1,000 years. The heliocentric, or sun-centered, Copernican system replaced this theory in the 1500s. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.