Theodosius of Bithynia

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Theodosius of Bithynia (Greek: Θεοδόσιος; c. 160 BC – c. 100 BC) was a Greek astronomer and mathematician who wrote the Sphaerics, a book on the geometry of the sphere.


Born in Tripolis, in Bithynia, Theodosius is cited by Vitruvius as having invented a sundial suitable for any place on Earth.[1] His Sphaerics provided the mathematics for spherical astronomy, and may have been based on a work by Eudoxus of Cnidus. Francesco Maurolico translated his works 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, and On Days and Nights, a study of the apparent motion of the Sun.



  • Ivor Bulmer-Thomas, "Theodosius of Bithynia," Dictionary of Scientific Biography 13:319–320.
  • also on line [1] "Theodosius of Bithynia." Complete Dictionary of Scientific Biography. 2008. 25 Mar. 2015 .
  •  Chisholm, Hugh, ed. (1911). [ "Theodosius of Tripolis" ] Check |ws link in chapter= value (help). Encyclopædia Britannica. 26 (11th ed.). Cambridge University Press.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>