Tianjing huowen 天經或問

Tianjing huowen 天經或問 "Questions on the Heaven's structure" is a book on astronomy written during the high Qing period 清 (1644-1911) by You Yi 游藝, courtesy name Ziliu 子六, style Daifeng 岱峰, from Jianyang 建陽, Fujian. You was a disciple of Xiong Mingyu 熊明遇, author of the Gezhi cao 格致草 "Notes on the investigation of things", which explored the entire celestial phenomena, from celestial bodies to meteorology. However, the work did not gain widespread circulation.

You's book consists of two collections (Qianji 前集 with 4 juan; Houji 後集 in one fascicle). The first juan presents 22 charts of the starry sky. Juan 2-4 discuss 50 different special topics of astronomy, like celestial bodies, terrestrial bodies, the ecliptic and celestial equator (huang-chidao 黄赤道), the North and South Poles, the Meridian Instrument (ziwu gui 子午規), the Horizon Instrument (diping gui 地平規), the precession of the equinoxes (jingxing mingwei 經星名位), names and positions of fixed stars, regional divisions (fenye 分野, calendar systems, chronology, aurora and twilight, wind, clouds, rain, dew, frost, snow, sleet and hail.

The first volume primarily discusses the fundamental knowledge of astronomy and calendar systems. Although it lacks original inventions or groundbreaking discoveries, its arguments are clear, its insights are profound, and its language is simple and accessible, making it quite distinctive. The modern scholar Wang Zhongmin 王重民 (1903-1975) once commented: "This book is less extensive than the Gezhi cao, but it surpasses it in clarity and readability." (Postscript to Tianjing huowen). As a result, its influence far exceeded that of its predecessor Gezhi cao and was reprinted multiple times after being introduced to Japan, with prints in 1730 and c. 1750.

The second volume of the Tianjing huowen aims to supplement the areas not covered in the first volume. While it also discusses ancient calendar systems, planetary motions (chandu 躔度), precession of the equinoxes (suicha 歲差, and the Seven Luminaries (qizheng 七政), it delves more into speculative topics like the nature of qi (liqi xingming 理氣性命), the spirits of mountains and seas (shanhai shenguai 山海神怪), transformations of life and death (shengsi bianhuan 生死變幻), and various supernatural phenomena. However, many of these speculative ideas lack factual basis and are generally dismissed by scholars. The Houji collection was, therefore, not included in the imperial series Siku quanshu 四庫全書.