A 15th century portrait of Ptolomy, here depicted as a king owing to confusion with the Ptolomaic kings of Egypt. Claudius Ptolemy (90-168 AD), was a Greek-Roman citizen of Egypt (Claudius is a Roman name and Ptolemaeus is a Greek name). He was a mathemat

- Image ID: G15C9C
A 15th century portrait of Ptolomy, here depicted as a king owing to confusion with the Ptolomaic kings of Egypt. Claudius Ptolemy (90-168 AD), was a Greek-Roman citizen of Egypt (Claudius is a Roman name and Ptolemaeus is a Greek name). He was a mathemat
Science History Images / Alamy Stock Photo
Image ID: G15C9C
A 15th century portrait of Ptolomy, here depicted as a king owing to confusion with the Ptolomaic kings of Egypt. Claudius Ptolemy (90-168 AD), was a Greek-Roman citizen of Egypt (Claudius is a Roman name and Ptolemaeus is a Greek name). He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. Ptolemy was the author of several scientific treatises. His astronomical treatise, the Almagest, is the only surviving comprehensive ancient treatise on astronomy. Ptolemy's other main work is his Geographia, a compilation of what was known about the world's geography in the Roman Empire during his time. His astrological treatise, a work in four parts, is known by the Greek term Tetrabiblos, or the Latin equivalent Quadripartitum: Four Books in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. It was used and consulted for over 1000 years. Ptolemy also wrote an influential work, Harmonics, on music theory and the mathematics of music. Few details of Ptolemy's private life are known for certain.