Life

Liu Hong was from Mengyin County, Taishan Commandery, which is present-day Mengyin County, Shandong, and was a descendant of Liu Yu, the Prince of Lu, a son of Emperor Jing ( 157–141 BCE). He developed an interest in astronomy at an early age. He was made an officer at the Imperial Astronomy around 160 CE which led to him writing the lost works Qi Yao Shu (七曜術; The Art of the Seven Planets) and Ba Yuan Shu (八元術; The Art of Eight Elements).

After the death of his father, Liu Hong retired for a short time but returned to his work, collaborating with Cai Yong on the Qian Xiang Li (乾象曆; Qian Xiang Calendar), this was considered so advanced for its time that it was adopted by the Han government immediately. The calendar predicted the movement of the moon, the first time such considerations had been made in ancient China. This system marked the first appearance of the argument of periapsis, a means to calculate syzygy (the calculation between three celestial bodies), and a means of charting the moon through the seasons. His means of establishing the accuracy of the calendar was by the detection of eclipses.

This system replaced one which had been used by the Han dynasty since 85 CE, and following the end of the Han dynasty and beginning of the Three Kingdoms period, it was adopted by the Eastern Wu state (229–280 CE) until China was re-unified under the Jin dynasty in 280 CE. In 179 CE, he was asked by the Imperial Secretariat to consider proposals made by a private scholar called Wang Han regarding lunar calendars, but did not support those proposals. A year later, the Minister of Ceremonies assigned him to review alternative means of calculating eclipses

Throughout his service under the Han government, Liu Hong held various positions, including: Internuncio (謁者), gucheng menhou, Commandant of the East District of Kuaiji, Administrator of Shanyang (山陽太守), and Chancellor of Qucheng (曲城相).

生平

東漢初原魯王劉興的後裔宗室，歷任校尉、郎中、常山長史、郎中、謁者、穀城門候、會稽東部都尉、山陽太守、曲城侯相。

著作

《乾象暦》原有五卷（《隋書·經籍志》，不過作者誤作成其三傳子弟、孫吳重臣闞澤），唐時僅剩三卷，後亡佚。