Reflections on the antikythera mechanism inscriptions

Abstract

A close look at the fragmentary inscriptions of the Antikythera Mechanism published by Freeth et al. [Freeth, T., Bitsakis, Y., Moussas, X., Seiradakis, J.H., Tselikas, A., Magkou, E., Zafeiropoulou, M., Hadland, R., Bate, D., Ramsey, A., Allen, M., Crawley, A., Hockley, P., Malzbender, T., Gelb, D., Ambrisco, W., Edmunds, M.G. Decoding the Antikythera mechanism: investigation of an ancient astronomical calculator. Nature 444 (7119), 587–591, 2006] reveals some elements, which could help to decode its function and use. The Back Door Inscription seems to give a detailed description of some external parts of the instrument and the related instructions for their use. We especially refer to the term «ecliptic» as compared to that in Ars Eudoxi and other papyri and inscriptions. The Back Plate Inscription seems to give instructions for the proper orientation and use of the instrument. The Front Door Inscription refers to the stationary points of planetary motion, but only two planetary names have been read, that of Venus and Mercury, as far as we know. After a study of the works of Alexandrian scholars Ptolemy, Theon, Paulus and Heliodorus regarding the stationary points of planetary motion, we arrive at the following conclusion: it seems very likely that the Antikythera Mechanism has been constructed apart from other uses (a) for the observation of the Sun, the Moon and the stars; (b) to simulate the longitudinal motion of the Sun, the Moon and the planets, and (c) in the case of Mercury and Venus the instrument could also show their stationary points and the retrograde arc between them; here we present additional arguments to support the view that this is also true for the three outer planets. As far as the technical knowledge underlying the construction of Mechanism’s gear trains is concerned, the last (eighth) book of Pappus’s Collection, includes the basic notions and theorems for such constructions, known from the earlier works of Archimedes.