The Reason for the Changes of the Fenxing in the Ancient Chinese Fenye Theory

The Fenye concept is important in ancient Chinese astronomy and astrology, and it is a correspondence between heaven and earth in the traditional Chinese culture. In the ancient Chinese astronomy, the constellations in the belt along the celestial equator (or the ecliptic) are usually divided and associated with the areas on the earth like Zhou (an ancient dominant state) and Guo (another state). The areas of the earth involved are collectively called the Fenye of the constellations. There are three types of Fenye theories. The first type are the Ganzhi theories (the Heavenly Stems and Earthly Branches), which involve three kinds of Fenye schemes, the Shigan (the ten Heavenly Stems) Fenye, the Shierzhi (the twelve Earthly Branches) Fenye, and the Shieryue (the twelve months) Fenye. The second type is Jiugong (Nine-Palace) theory, i.e. Jiugong Fenye. The third type are the Xintu theories, which have four kinds of models, the Danxing (single-star) Fenye, Wuxing (Mercury, Venus, Mars, Jupiter, and Saturn) Fenye, Shierci-Ershibaxiu Fenye, and Beidou (Big-Dipper) Fenye. The Shierci-Ershibaxiu Fenye is most important among these. In the ancient China, the belt along the celestial equator (or the ecliptic) is divided into 12 equal parts, which are called Shierci (12 sets of stars along the Jupiter pathway in the sky). The location of each part on the equator (or the ecliptic) is usually represented with its Ruxiudu in the Ershibaxiu (28 lunar mansions). A Ruxiudu is equal to the degrees from the nearest lunar mansion. The Fenxing is the association of regions in the belt to the 12 parts of the Shierci. The Shierci-Ershibaxiu Fenye is the subject of this paper. Based on the analysis and research about ancient official annals, local chronicles, and other relevant historical records, we find that (1) the earth precession is not the main reason for the changes of Fenxing, especially in the model of the Shierci-Ershibaxiu Fenye, as the agreement fraction between the changes of Fenxing and the precession values is less than 26.7% for the data in sixteen documents, and (2) the changes of the Fenxing are affected by many factors, including whether the Shierci regions are uniform, the evolution of the concept of Fenye, calendar factors, the accuracies of observations, and even the subjective attitude of authors of the ancient documents. Subjective factors are particularly obvious in the local chronicles.