Oxyrhynchus’ astronomical papyri (1)

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The astronomical papyri from the ancient town of Oxyrhynchus in Middle Egypt date mostly from the first to fifth centuries CE. The general picture of Greek astronomy in this period has been characterised by the “kinematic”, geometrical planetary models, developed by Apollonius, Hipparchus and other early Greek astronomers and which were brought into their final form by Ptolemy in the Almagest (ca. 140 CE). By means of these models, planetary positions at any given point in time can be calculated by adding complicated trigonometric adjustments to linear functions of time. The Greek models have been assumed to have superseded the Babylonian arithmetical schemes, in which the periodic planetary phenomena are predicted on the basis of linear zigzag functions or piecewise constant “step functions”. The astronomical papyri from Oxyrhyncus modificate this one-sided picture: a large variety of Babylonian methods were still in use by practising astrologers of the late Roman period, simultaneously with Ptolemy’s geometrical methods.

The types of astronomical texts found in the Oxyrhyncus papyri are partially very similar to those extant in cuneiform. Most of the texts were used for the actual calculation of solar, lunar and planetary positions and for the production of horoscopes. They contrast with the generally accepted idea that Greek astronomy was more of a theoretical than of a practical nature. The astronomical papyri from Oxyrhyncus show the coexistence of Babylonian arithmetical schemes and Greek kinematic models during the Roman period. For various types of Babylonian tables that are extant in cuneiform for only some of the planets, the Oxyrhyncus Greek papyri provide the first evidence of their existence for all planets. Some papyri seamlessly extend Babylonian tables over much longer periods of time. In various cases the papyri provide completely new parameters for Babylonian schemes and Ptolemaic models. A larger group of fragments that originally constituted a single library discarded in the early fourth century shows that both Babylonian and Ptolemaic methods might be represented in a single collection and even allows the hypothesis that the Ptolemaic methods gradually replaced the Babylonian ones by the middle of the third century CE.

Bibliography

Amar Annus

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