Responsum: On the Astrolabe

The last and perhaps the greatest of the Babylonian geonim, Hayya (or Hay) bar Sherira was educated in the academy of Pumbedita, in Baghdad, at the feet of his father, the influential Sherira Ga’on. Uniquely among the geonim, Hayya was promoted to be co-head of the academy together with his father, and the two often wrote responsa jointly. During his leadership, the academy was facing financial difficulties, and so Hayya engaged in a tireless campaign to maintain connections with the Jewish diaspora, composing letters and legal works for Jews worldwide and fundraising. Hayya was generally less receptive to Arabic culture than some other geonim, but his writings integrated Islamic theological terminology and evinced similar concerns. He composed several legal monographs in Judeo-Arabic that were of lasting influence, and his Judeo-Arabic dictionary was an early foray into that genre. Recent discoveries in the Cairo Geniza have suggested that Hayya was a more impressive poet than previously thought.