Ptolemy
Claudius Ptolemy (; , ; ; – 160s/170s AD), better known
mononymously as
Ptolemy, was a
Greco-Roman mathematician,
astronomer,
astrologer,
geographer, and
music theorist who wrote about a dozen scientific
treatises, three of which were important to later
Byzantine,
Islamic, and
Western European science. The first was his astronomical treatise now known as the ''
Almagest'', originally entitled '
(, ', ). The second is the ''
Geography'', which is a thorough discussion on maps and the geographic knowledge of the
Greco-Roman world. The third is the astrological treatise in which he attempted to adapt
horoscopic astrology to the
Aristotelian natural philosophy of his day. This is sometimes known as the '''' (, 'On the Effects') but more commonly known as the '''' (from the
Koine Greek meaning 'four books'; ).
The
Catholic Church promoted his work, which included the only mathematically sound
geocentric model of the
Solar System, and unlike most
Greek mathematicians, Ptolemy's writings (foremost the ''Almagest'') never ceased to be copied or commented upon, both in
late antiquity and in the
Middle Ages. However, it is likely that only a few truly mastered the mathematics necessary to understand his works, as evidenced particularly by the many abridged and watered-down introductions to Ptolemy's astronomy that were popular among the Arabs and Byzantines. His work on
epicycles is now seen as a very complex theoretical model built in order to explain a false tenet based on faith.
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