Yi Xing (683-727), a monk of theTang Dynasty, led a large-scale project to identify the locations of the major stars, and, based on the results, concluded that the length of a degree of the meridian line was 351.27 li by Tang measurement, which meant 123.7 km. This was the first measurement of the meridian ever done in the world.
Around the year 723, Yi Xing and his colleagues constructed an armillary sphere which could move in synchronization with the movements of the heavenly bodies at night. It was installed in anobservatoryestablished in Chang'an (Xi'an), the capital of the Tang Dynasty.
Astronomical studies made impressive headway during the Song Dynasty (960-1279). During this period, five large-scale observations of the sky were undertaken, resulting in star maps. The stone planisphere kept inSuzhoutoday was first drawn during the reign of Emperor Yuanfeng (1078-85) and then committed to stone in 1247 by Wang Zhiyuan of theSouthern Song Dynasty. On the map are 1,434 stars, the ecliptic, the equator, the Milky Way and the twenty-eight constellations. The lower part of the planisphere is occupied by explanations totaling 209 characters, which constitute a concise introduction to the astronomical knowledge man had grasped by that time. This is China's earliest and most complete star map still extant.
Shen Kuo was a noted scientist of theNorthern Song Dynasty. He left behind a great store of notes and research findings in the fields of geography, geology, astronomy and mathematics. His work Dream Stream Essays contains early discussions of thecompassand movable typeprinting. This book is of great value for the study of the history of science.
Guo Shoujing (1231-1316), a noted scientist of theYuan Dynasty, made major improvements to the sundial. First he created a tower sundial, raising its height from the original 2.66 meters to 13.33 meters, which drastically increased its accuracy. Based on his research, the calendar was revised. His calendar had 365.2425 days in a year, which was only 26 seconds different from the time it takes the earth to go around the sun. His achievement was 300 years earlier than the finalization of the modern calendar.
Guo Shoujing made great contributions in the areas of astronomy, the calendar and water conservation. He made or improved 13 kinds of astronomical instruments. In 1296, he improved the armillary sphere into an astronomical observation apparatus, in which he discarded the ecliptic ring, and combined the azimuth, equatorial torquetum and sundial into one, which not only simplified the structure but also made the armillary sphere more accurate. It overcame the shortages of the armillary sphere in having too many rings, being difficult to operate and having limited measuring capacity. The equator device in Guo's new instrument was an important invention in astronomical apparatus making and very similar to that in modern astronomical telescopes. Occupying an important position in the world's history of astronomy, Guo's torquetum was 300 years earlier than a similar instrument produced by Danish astronomers.
Author: Jessie
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