Theodosius of Bithynia ( grc-gre, Θεοδόσιος; c. 169 BCc. 100 BC) was a Greek astronomer and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

who wrote the ''

Sphaerics ''Sphaerics'' ( grc, Σφαιρικά) was a set of three volumes on spherical geometry written by Theodosius of Bithynia in the 2nd century BC. These proved essential in the restoration of Euclidean geometry to Western civilization, when brought ...

'', a book on the geometry of the sphere.

Life

Born in Tripolis, in

Bithynia Bithynia (; Koine Greek: , ''Bithynía'') was an ancient region, kingdom and Roman province in the northwest of Asia Minor (present-day Turkey), adjoining the Sea of Marmara, the Bosporus, and the Black Sea. It bordered Mysia to the southwest, Pa ...

, Theodosius was mentioned by

Strabo Strabo''Strabo'' (meaning "squinty", as in strabismus) was a term employed by the Romans for anyone whose eyes were distorted or deformed. The father of Pompey was called "Pompeius Strabo". A native of Sicily so clear-sighted that he could see ...

as among the residents of Bithynia distinguished for their learning, and one whose sons were also mathematicians. He was cited by

Vitruvius Vitruvius (; c. 80–70 BC – after c. 15 BC) was a Roman architect and engineer during the 1st century BC, known for his multi-volume work entitled ''De architectura''. He originated the idea that all buildings should have three attribute ...

as having invented a

sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...

suitable for any place on Earth. His chief work, the ''Sphaerics'' ( grc-gre, σφαιρικά), provided the mathematics for

spherical astronomy Spherical astronomy, or positional astronomy, is a branch of observational astronomy used to locate astronomical objects on the celestial sphere, as seen at a particular date, time, and location on Earth. It relies on the mathematical methods of ...

, and may have been based on a work by

Eudoxus of Cnidus Eudoxus of Cnidus (; grc, Εὔδοξος ὁ Κνίδιος, ''Eúdoxos ho Knídios''; ) was an ancient Greek astronomer, mathematician, scholar, and student of Archytas and Plato. All of his original works are lost, though some fragments are ...

.Ivor Bulmer-Thomas
"Theodosius of Bithynia,"
in Dictionary of Scientific Biography, Encyclopedia.com, 2008. It is reasonably complete, and remained the main reference on the subject at least until the time of

Pappus of Alexandria Pappus of Alexandria (; grc-gre, Πάππος ὁ Ἀλεξανδρεύς; AD) was one of the last great Greek mathematicians of antiquity known for his ''Synagoge'' (Συναγωγή) or ''Collection'' (), and for Pappus's hexagon theorem i ...

(4th century AD). The work was translated into

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

in the 10th century, and then into Latin in the early 16th century, but these versions were faulty.

Francesco Maurolico Francesco Maurolico (Latin: ''Franciscus Maurolycus''; Italian: ''Francesco Maurolico''; gr, Φραγκίσκος Μαυρόλυκος, 16 September 1494 - 21/22 July 1575) was a mathematician and astronomer from Sicily. He made contributions t ...

translated the works later in the 16th century. In addition to the ''Sphaerics'', two other works by Theodosius have survived: ''On Habitations'', describing the appearances of the heavens at different

climes The climes (singular ''clime''; also ''clima'', plural ''climata'', from Greek κλίμα ''klima'', plural κλίματα ''klimata'', meaning "inclination" or "slope") in classical Greco-Roman geography and astronomy were the divisions o ...

and different times of the year, and ''On Days and Nights'', a study of the apparent motion of the Sun. Both were published in Latin in the 16th century.

Notes

References

Ivor Bulmer-Thomas Ivor Bulmer-Thomas CBE FSA (30 November 1905 – 7 October 1993), born Ivor Thomas, was a British journalist and scientific writer who served eight years as a Member of Parliament (MP). His career was much influenced by his conversion to the Chu ...

, "Theodosius of Bithynia," ''Dictionary of Scientific Biography'' 13:319–320. *also on lin

"Theodosius of Bithynia." Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com. 25 Mar. 2015 . * Ancient Greek astronomers Ancient Greek astrologers Ancient Greek geometers 2nd-century BC Greek people 2nd-century BC writers 160s BC births 100s BC deaths 2nd-century BC mathematicians {{europe-astronomer-stub