India

Ptolemy was the last major figure in the Greek astronomical tradition. Commentaries were written on his works by Pappus of Alexandria in the 3rd century CE and by Theon of Alexandria and his daughter, Hypatia, in the 4th, but creative work was no longer being done. Babylonian astronomy traveled eastward into Persia and India, where it was adapted in original ways and combined with native Indian methods. Greek geometrical planetary theories, from the time between Hipparchus and Ptolemy, also made their way into India. This material is of great complexity and variety and is difficult to sort out. For example, Babylonian arithmetical procedures used for computing lunar and solar phenomena turn up in conjunction with a length for the solar year due to Hipparchus. Nevertheless, the Indian material, besides its own intrinsic interest, provides information about Greek astronomy during a vital period about which the Classical texts say little.