R. Avraham bar Ḥiyya ha-Nasi · c. 1132
Read the translation (PDF) · Editorial footnotes (PDF)
A foundational work of medieval cosmology that lays out the shape of the cosmos as the Greeks and their Arabic heirs understood it: a spherical earth at the center of nested celestial spheres, the paths of sun and moon, and the zones and geography of the inhabited world.
The book proceeds by gates, each opened by a series of petaḥim — “openings” — which give it the feel of a structured course rather than a treatise. The first gate sets out the structure of the heavens and the earth, and works through to the inhabited part of the earth: which portion of a spherical world is habitable, and how it is divided.
The second gate carries the scheme further, and the third turns to the Moon — the clarification of its motion, including the compound lunar motion that any serious account of the calendar or of eclipses depends on. The fourth gate treats eclipses of the two luminaries directly.
Its importance is as much linguistic as astronomical: this is one of the first scientific works written in Hebrew rather than Arabic, at a moment when a Jewish scholar wanting this material would ordinarily have read it in Arabic. Bar Ḥiyya had to make Hebrew carry it — the vocabulary, the geometry, the whole apparatus — and in doing so opened the tradition that the rest of this corpus’s Hebrew astronomy belongs to.
The translation is made from the richly illustrated first printed edition (Basel, 1546), which carries Latin notes by the Hebraist Sebastian Münster. That volume is bilingual — each work printed once in Hebrew, then again in Latin with the apparatus of Münster and Erasmus Oswald Schreckenfuchs — and only the Hebrew portion was translated, with Münster’s facing annotations used as a parallel witness to resolve the difficult sixteenth-century type. The edition includes its own note on how it was produced.