Luó Yǎgǔ 羅雅谷 / Giacomo Rho, S.J.
Italian Jesuit. Born Milan, 28 January 1593; died Beijing, 27 April 1638. The Chinese name Luó Yǎgǔ renders the personal name “Iacobus / Giacomo” (Yǎgǔ) with the Luó surname (a free choice approximating “Rho”).
Joined the Society of Jesus 1614; sent to Asia 1617, reaching Macao 1618. Spent his early China-mission years in southern stations (Hángzhōu under Yáng Tíngyún’s protection during the 1616 persecution; later Shānxī and Shǎnxī); summoned to Beijing 1631 by Xú Guāngqǐ 徐光啟 (徐光啟) to join the calendar-reform project after the death of Johann Schreck-Terrentius 鄧玉函 (鄧玉函) the previous year.
Strong mathematical-and-astronomical training; brought significant contributions to the Chóngzhēn lìshū project (KR3f0013 Xīnfǎ suànshū), especially in trigonometry, the eclipse-computation tables, and the mathematical exposition of the Tycho-Brahe geo-heliocentric system that supplied the project’s underlying astronomical model. Among the works credited to his authorship within the Lìshū compilation: the Cèliàng quányì 測量全義 (Complete Meaning of Measurement) — the first systematic Chinese exposition of European trigonometry, plane and spherical, in 10 juàn; the Bǐlìguī jiě 比例規解 (Explanation of the Sector — the proportional compass instrument); the Chóurén zhuàn 籌人傳 (Biographies of the Calculators — appended biographical material); and substantial portions of the eclipse-prediction sections.
Rho’s death in April 1638 — at the relatively young age of 45, four years before the fall of the Míng — left the work’s final completion to Adam Schall von Bell 湯若望 (湯若望), who would also bring the project across the Míng-Qīng dynastic transition into the institutionalized Qīng court astronomy. Rho is the second Western Jesuit named in the Chóngzhēn lìshū preface and the Sìkù tíyào of KR3f0013.