Reconstruction Designs of the Lunar Subsystem

Abstract

The lunar subsystem is a special and complicated mechanism in the surviving evidence. Various reconstruction designs were presented in the past years. The decoding of this subsystem started from the discovery of a pin-in-slot joint by Wright (Antiquarian Horology 27:270–279, 2003, Bull Sci Instrum Soc 85:2–7, 2005, Antiquarian Horology 29:51–63, 2005) who claimed and restored the mechanism of the lunar anomaly motion in the Antikythera device. In 2006, Freeth et al. presented a hypothetical gear, which connects the lunar subsystem and the calendrical subsystem. Due to this hypothetical gear, the design concept that there were two input sources to drive the lunar subsystem was presented in their reconstruction design (Freeth et al. in Nature 444:587–891, 2006, Nature 454:614–617, 2008; Freeth in Sci Am 301:79–83, 2009). Thus, the output lunar motion satisfies completely the Hipparchus’ lunar theory. At present, the reconstruction design by Freeth et al. is the most popular design even though an obvious pentagon pattern detected in the surviving fragment of the lunar subsystem still goes without a proper explanation. This chapter focuses on decoding this unexplained feature of the lunar subsystem.