#### CLAUDIUS
PTOLEMY

One
of the most influential Greek astronomers and geographers of his time, Ptolemy
propounded the geocentric theory in a form that prevailed for 1400 years. We do
not know much about his life but most of his major works have survived. His
earliest and most important piece is the *Almagest* which gives in detail
the mathematical theory of the motions of the Sun, Moon and planets. This
thirteen-book treatise was not superseded until a century after another
mathematician, Copernicus, presented his heliocentric theory in the *De
revolutionibus *of 1543.