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 MíngQīng 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.