学会誌 要約紹介　通巻7　2025年1巻1号

An astronomical archeology investigation of the relationship between the orientations of the main halls of Kibitsu Shrine (Bitchū), Kibitsuhiko Shrine (Bizen), and Kibitsu Shrine (Bingo) and celestial phenomena revealed that the shrines in Bizen and Bingo were designed to reflect specific points on the solar path. In contrast, the main hall of the Bitchū Kibitsu Shrine is oriented not toward the sacred rock（Iwakura） known as Hachijō-iwa, but toward the direction in which the heliacal rising of Sirius can be observed. This orientation suggests a possible transformation of the ritual system accompanying a change in political authority. These findings indicate that the architectural orientations of the three shrines were likely intended to emphasize sacredness through celestial phenomena while simultaneously expressing religious and political intentions.

Additional research of the megalithic astronomical sites of Shira-ishi-no-hana and Kasane-ishi in Matsuyama City, Ehime Prefecture, suggests that Shira-ishi-no-hana may have been larger than previously assumed, and that the builders of both sites may have possessed sophisticated mathematical and astronomical knowledge. Likely constructed during the Jomon period or at a time when the sea level was lower than at present, these sites may be of noteworthy cultural interest.

The history of calendrical systems in Japan, spanning from primitive natural calendars to the adoption of the Gregorian calendar, transcends simple chronological changes. It embodies the consolidation of political power, the assimilation and adaptation of continental influences, and the distinct path of domestic scientific progress. This study investigates these historical shifts through the lens of their social implications and technical characteristics.