The Back Plate Inscription and eclipse scheme of the Antikythera Mechanism revisited

Abstract

This paper presents a new edition of the Back Plate Inscription (BPI) of the Antikythera Mechanism, a series of descriptions of circumstances associated with eclipses indicated cyclically by the inscriptions of the Mechanism’s Saros Dial Scale. Our edition features several significant new readings as well as the confirmation of a disputed reading pertaining to one of the index letters by which the BPI’s paragraphs are linked to the specific eclipse glyphs of the Saros Dial. On the basis of the new text, we deduce a revision of the established models for determining which lunar months of the Saros cycle had solar and lunar eclipse possibilities (EPs) and for assigning the solar EPs to paragraphs of the BPI. We further confirm that the entire extant part of the BPI comprises consecutive paragraphs concerning the solar EPs, all inscribed along the right side of the Mechanism’s Back Plate, and we revisit the questions of what the BPI’s predictions mean and how they relate to the model for the solar EPs.