1288-1344

French-Jewish Mathematician and Astronomer

One of the few Jewish scholars of any discipline who came to prominence in Christian Europe, Levi ben Gershom dealt with problems in arithmetical operations and trigonometry. As an astronomer, he observed several eclipses and developed Jacob's staff, a mechanism for measuring the angular distance between heavenly bodies.

Known variously as Gersonides, Leo de Bagnolas, Leo Hebraeus, and Ralbag, Levi ben Gershom was born in the French town of Bagnols in 1288. He first came to prominence in 1321, with the publication of Sefer ha Mispar, or Book of Numbers. Among the subjects involving arithmetical operations discussed in the book was that of root extractions.

In 1342, Levi produced a work translated as On Sines, Chords, and Arcs. An investigation of trigonometry, On Sines presented five sine tables and examined the sine theorem for plane triangles. It is evident that Levi, while...