Scientific Contribution of Guo Shoujing
3 min readGuo Shoujing（1231-1316）was a Chinese astronomer，water conservancy specialist and instrument maker during Yuan dynasty.His major contributions were in hydraulics，the study of the astronomical calendar，and astronomical instrument making.Before the age of 44，his main energy was used for the designing and implementation of water conservancy projects; from the age of 45 to 58, he shifted to astronomical calendar and instrument making; and after 59, again he committed his time and energy to hydraulics and astronomical instrument making.
Guo Shoujing presented over 20 proposals for water conservancy projects and was personally involved in such projects for hundreds of rivers and canals, big or small. In1262, he suggested six hydraulic construction projects, five of which were farmland irrigational works in north China, to build up self-flowing irrigation water channel networks.
The six involved the Dadu(present-day Beijing) canal construction project from Tongzhou (in Beijing) to Yangcun (present-day Wuqing of Hebei province),a new canal in the region. In 1264, he made field trips to the ancient canal in Xixia (present-day Ningxia Hui Autonomous Region) and Chapawulang lake (present-day Wuliangsu lake in Inner Mongolia), to allow the local people to regain the benefits from the canal and the lake through dredging and reconstruction. In 1265, he advised to the repair of Jinkou river course in east Beijing and consequently solved the problems of farmland irrigation and eastward goods transportation. In 1275, he recommended and implemented a water-way communication networking project to connect Beijing-Hangzhou Grand Canal and link up Jiangsu, Shandong, Henan, Hebei provinces with the capital city Beijing.
During 1291-1293, he designed and supervised the Tongzhou-Dadu canal construction thus completing finally Beijing-Hangzhou Grand Canal flowing through north and south China. Based on his rich experience, for the first time in the world he put forth a quantitative and metric approach to designing the width and depth of the canal in line with local hydrographical conditions such as the mountain flood flow rate. He was also the first to come up with the concept of height above sea level and reach the conclusion of Beijing’s location of lower elevation above sea level in relation to Kaifeng.
During 1276-1289, together with Wang Xun, Guo Shoujing formulated Grant-to-farmer Calendar, later he authored several astronomical calendar specific works and supervised astronomical observation. His major contributions include:① Creative making of 13 varieties of astronomical instruments such as abridged armilla, gnomon, polaris observatory device, armillary sphere, delicate device, scaphe, justification device, main drive device, shadow definer, observing table, solar and lunar eclipse observing device, star dial timer, and equatorial sundial. He also made 22 varieties of smaller, portable devices to constitute a complete observatory system, including an observatory meter and devices for suspending, seating and squaring adjustments. His creation of astronomical instruments ranked the first in his time in terms of quantity, quality and creativity.② Supervision of astronomical observation. During 1277-1280, he chaired the sundial shadow observation about 200 times in the capital city Dadu (Beijing), based on which he worked out very exact times of the winter solstice and the tropical year length of 365.242,5 days through reducing calculus, almost fully consistent with the world’ suniversal calendar nowadays. He also organized large-scale nationwide observation, selected 27 sites for observation data, which was unprecedented in the site number, distribution and accuracy.③ Development of maths of Song and Yuan dynasties. He created high-order interpolation with Wang Xun and used the three-order interpolation for calculation of the movement and location of the sun, the moon and the five major stars; with his initiation of the arc sagitta cyclotomic solution, he worked out the interior and exterior degrees of the’ yellow’ equator difference and the equator.④ Compilation of a series of works on astronomical calendar, including Deduction, Preliminary Introduction to Calendar InstrumentNotes to Three Calendars, Models of Astronomical Observation, Exploration of Ancient and Present Eclipses, Annotations to Timing, Universe Phenomena, and Revisions of the Original Assumptions.
With his fruitful accomplishments, Guo Shoujing became the greatest scientist during the 13th-14th centuries, among the most renowned of his time around the world.
