Kaku Shukei

An astronomer, ritual implement maker, and hydraulic expert active during the Yuan dynasty in China. Born in Xingtai, Shunde (now Xingtai County, Hebei Province), he was taught hydraulic engineering, astronomy, and mathematics by his grandfather Guo Rong (date of birth and death unknown). He became a student of Liu Bingzhong (1216-1274), a strategist for Kublai Khan, the founder of the Mongol Empire (the country's name was established in 1271), and a close friend of Guo Rong, and became acquainted with Zhang Wenqian (c. 1216-c. 1283) and Wang Xun (1235-1281). He served Emperor Sejo from 1262, and made great contributions to flood control projects, including investigating the source of the Yellow River and conducting the first measurements of the altitude above sea level along the section between Dadu (now Beijing) and Kaifeng.

In 1276, after the Yuan Dynasty overthrew the Song Dynasty, a calendar reform project began under the supervision of Zhang Wenqian, and Wang Xun was recommended to join. In the newly established Taishiyuan, Wang Xun was appointed as Grand Historian and Guo Shoujing was appointed as the Tongzhi Grand Historian. They were responsible for the development and production of observational instruments such as the Jianyi and Gaobiao, as well as for determining the date and time of the winter solstice, measuring the latitude of various regions, and observing the positions of the stars. The new calendar was compiled in 1280 and named the Shushi Calendar, and was distributed the following year in 1281, but Wang Xun died in 1282 with the calendar tables still incomplete, so Wang Xun took over as Grand Historian and completed the draft. The Shushi Calendar was based on Wang Xun's ingenious calculation methods and Guo Shoujing's precise observations, and is considered to be the most excellent calendar ever made in China. His style was based on the traditions of Chinese calendar science and was not directly influenced by Islamic astronomy, which had already been introduced to China at the time, but the influence can be seen in the observation instruments he created.

In his later years, he took on the role of Metropolitan Water Superintendent and once again became involved in water conservancy projects, completing the Grand Canal (Baifuyan and Tonghui River) that passed through Dadu in 1293.

[Kazuhiko Miyajima]

"The Chinese Astronomical Calendar System" by Kiyoshi Yabuuchi (1969, expanded and revised edition, 1990, Heibonsha) " "The Way of the Calendar System: Science and the State in Medieval China" by Keiji Yamada (1980, Misuzu Shobo)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

中国、元代に活躍した天文学者、儀器製作者、水利家。順徳邢台(けいだい)（現、河北(かほく／ホーペイ)省邢台県）に生まれ、祖父の郭栄（生没年不詳）から水利技術、天文学、数学の手ほどきを受け、蒙古(もうこ)帝国（1271年より国号を元とする）の世祖フビライ・ハンの謀臣で郭栄と親しかった劉秉中(りゅうへいちゅう)（1216―1274）の門下に入って、張文謙（1216ごろ～1283ごろ）や王恂(おうじゅん)（1235―1281）らと知り合った。1262年より世祖に仕え、治水事業に携わって功績をあげ、黄河の源流の調査や、大都（現、北京(ペキン)）―開封(かいほう)間に沿った海抜高度の初の測定も行った。

　1276年、元が宋(そう)を滅ぼすと、張文謙の統轄の下で改暦事業が始まり、王恂の推挙でこれに加わった。新設の太史院では王恂が太史令、郭守敬は同知太史院事となって事にあたり、簡儀、高表などの観測器の開発・製作と、冬至の日時の確定、各地の緯度の測定、星の位置観測などの実際観測を担当した。新暦は1280年に編纂(へんさん)が終わり授時暦(じゅじれき)と命名され、翌1281年から頒行されたが、なお暦表などが未完成のまま1282年に王恂が死去したため、太史令を継いで定稿を完成した。授時暦は王恂による創意ある計算法と郭守敬による精密な観測に基づいており、中国でつくられたもっとも優秀な暦とされる。その形式は中国暦学の伝統のうえにたつもので、当時すでに中国に伝わっていたイスラム天文学の直接の影響はないが、彼の製作した観測器にはその影響がみられる。

　晩年は都水監を兼任してふたたび水利事業にも携わり、1293年には大都を通る大運河（白浮堰(はくふえん)と通恵河）を完成させた。

［宮島一彦］

『藪内清著『中国の天文暦法』（1969／増補改訂版・1990・平凡社）』▽『山田慶児著『授時暦の道　中国中世の科学と国家』（1980・みすず書房）』

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