The Origin of »System B« of Babylonian Astronomy

Abstract

Our understanding of the Babylonian mathematical astronomy of the Seleucid-Parthian period progressed in several rather distinct steps. In its first phase, forever associated with the names of Epping, Kugler, and Schaumberger, the main efforts were concentrated on clarifying the astronomical meaning of the computational devices and the terminology, a truly pioneering work of decipherment and interpretation. Building upon these results my own efforts were directed toward a uniform mathematical classification of the textual material and its systematic arrangement in a corpus, at least so far as the strictly mathematical-astronomical texts were concerned. During the last decade these studies have entered a new phase which one may perhaps characterize as the “historical” phase in which one endeavors to penetrate into the Babylonian way of constructing a methodology, the results of which are now comparatively clear before us. Perhaps the most important result in this line of research is the demonstration by A. Aaboe¹ that the computational rules for ephemerides of the “System A” type can be derived from very simple assumptions concerning the distribution of the events under consideration on the ecliptic. It is the purpose of this paper to show that exactly the same methodological idea leads also to the rules of “System B”. In the past I repeatedly had occasion to point out that the commonly accepted evolutionary sequence from A to B is by no means securely established. Obviously the existence of a common methodological basis makes a chronological distinction between the two systems still more difficult.