David Gans · c. 1613
Read the translation (PDF) · Editorial footnotes (PDF)
A Hebrew textbook of astronomy that presents the Ptolemaic model of the heavens for a Hebrew-reading audience, weaving the cutting-edge European science of its day together with the medieval Jewish cosmological tradition — its author having personally visited the Danish astronomer Tycho Brahe.
The work is organized into twelve sections (she’arim) and 305 numbered paragraphs (simanim), a structure that lets it be used as a reference as much as read straight through; the printed volume supplies its own index to the paragraphs.
The early sections build the sphere from the ground up. Gans fixes the celestial pole by way of the Great and Little Bear, argues that the heavens are spherical and that no other shape will serve, notes that the circle encloses more than any other figure, and divides the ecliptic into its 360 parts. He then turns to the globe as an instrument — its diameter and poles, and the circles drawn upon it: the equator, the tropics, the northern and southern circles, the meridian and the horizon, with the distances between them worked out and methods given for constructing them. What follows is the working apparatus of positional astronomy, presented in Hebrew for readers who had no access to it in Latin.
Gans is the point of contact between two worlds that are usually described as separate. He was a Prague scholar at home in rabbinic literature who also went to Benátky to visit Tycho Brahe, and Nechmad ve-Na’im is what that contact produced: a serious astronomical textbook that assumes both the medieval Jewish cosmological tradition and the observational astronomy of its own moment, and treats neither as an intrusion on the other.
The book was not printed in the author’s lifetime. It first appeared at Jessnitz in 1743, more than a century after it was written, and never again — the volume opens with an apologia by the rabbi who brought it to press. That printing carries a Latin preface by the Leipzig Hebraist Johann Christian Hebenstreit, a sign of how far outside its own community the work was expected to travel.