6 - Astronomy among Jews in the Middle Ages

Summary

In the Middle Ages Jews were deeply involved in the practice of astronomy and they depended on the Greco-Arabic tradition largely based on Ptolemy's Almagest composed in the second century c.e. During the first phase, from about 750 to 1100, contributions by Jews, whether in Hebrew or Arabic, were relatively minor compared with those of their Muslim contemporaries. However, in the second phase, beginning in Spain in the twelfth century, some significant works were translated from Arabic into Hebrew and others were summarized. In addition to the dominant Ptolemaic tradition, Jews had access to an astronomical tradition exemplified in Arabic by the tables of al-Khwārizmī (d. ca. 840) that ultimately derived from Hindu sources. Translations from Arabic into Hebrew continued in the thirteenth and fourteenth centuries and, by the end of the thirteenth century, enough material was available in Hebrew for Jews who did not know Arabic to compose original treatises that were more advanced than an introductory work. In addition to those writing in Arabic and in Hebrew, there was an important group under the patronage of Alfonso X, King of Castile (reigned 1252–84), that produced treatises in Castilian. The fourteenth century marks the third phase in which Jews made their most original contributions to astronomy, and this phase continued in the fifteenth century when Jews still excelled in this discipline by the standards of the day. In geographical terms, interest in astronomy can be found in nearly all Jewish communities, but the works produced in Spain and southern France were the most important.

The evidence for Jewish involvement in astronomy is largely based on literary sources preserved in manuscripts, but there are some artifacts (notably astrolabes) and documents preserved in the Cairo Geniza that are now dispersed in various libraries. Other evidence comes from such community decisions as the ban on philosophy decreed in 1305 in Barcelona from which the study of astronomy was specifically excluded. The ban (or ḥerem) reads in part as follows:

From this day on and for the next 50 years, no member of our community shall study the “Greek” works on science or metaphysics, either in the original [i.e., in Arabic] or in translation, before he will have reached the age of 25.…We have exempted from our decree the study of medicine, although it is a natural science, for the Torah has given the physician permission to practice the art of healing.