c.85 - c.165
Ptolemy was one of the greatest astronomer and geographer of ancient
times. He made his astronomical observations in Alexandria, Egypt.
He established a system of mathematical astronomy which was used
until the 16th century.
Ptolemy placed the earth at the center of the universe, around it went the moon, sun, and planets at various speeds. His theories are preserved in a 13-volume work known as the 'Almagest'.
In addition Ptolemy wrote on geometry, a five-book treatise on optical phenomena, a three-book treatise on music, and eight books of geographical text and maps. In it he underestimated the size of the ocean, a mistake that later encouraged Columbus to undertake his famous voyage.
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