雙語科技百科(天文) 第17期:《大衍曆》
Da Yan Calendar
D a Yan Cdlenddr was drafted by Zhang Sui ( 683一727，also named Seng Yixing)in 727，and was later sorted out by Zhang Shuo(667一730) and Chen Xuanjing.
《大衍曆》，公元727年唐朝天文學家張遂(683一727，又名僧一行)修訂，後經張說(667一730)和陳玄景整理成文。The calendar consists of seven parts that elaborate on a variety of computa-Lion. There are another 12 articles dealing with some theoretical issues，mainly the articles Zhang Sui wrote in the calendar.
《大衍曆》分七章，詳細介紹了各種計算方法。此外，張遂還在《大衍曆》中寫了12篇相關理論問題的文章。
At the beginning of calendar making，in order to measure the position of stars in their orbits and get the law of movement, Zhang，in cooperation with his colleagues，made the bronze armillary sphere and ecliptic sphere，with which they gath-erect lots of astronomic data through practical ob-nervation，and carried out effective astronomic re-search. For instance，they remeasured the post-tion of over 150 stars and the degree between the 28 constellations and the celestial North Pole，hence concluding the stars were always in mo-tion. Based on this fad，Zhang inferred other stars on the celestial bodies were also movable，over-throwing the conclusion reached by his ey(1656一1742)，a British astronomer also Put foward a similar view-Point，but was over a thousand years later.
在《大衍曆》修訂初期，爲了測量日、月、星辰在其軌道上的位置和掌握其運動規律，張遂等人制造了觀測天象的“渾天銅儀”和“黃道遊儀”。藉助天文儀，通過實際觀測，他們蒐集了許多天文數據，有效地進行了對天文學的研究。例如，通過重新測定150多顆恆星的位置，多次測定二十八星宿距天體北極的度數，發現恆星是運動的。根據這個事實，張遂推斷出天體上的恆星肯定也是移動的，於是推翻了前人的恆星不運動的結論。英國天文學家哈雷(1656 } 1742)也提出了恆星自己移動的觀點，但比張遂的發現晚1000多年。In revising the calendar, Zhang attached huge importance to practice. Togeth-er with Nan Gongshuo，he used a post to measure the shadow cast by the sun，and calculated the relations between the sun’s positions and the solar terms. Be-sides，Zhang also designed an astronomic instrument called Fujuyi for measuring the altitude of the North Pole in different places throughout the country.
在曆法修訂過程中，張遂非常重視實踐。張遂和南宮說等人一起，用標竿測量日影，推算出太陽位置與節氣的關係。張遂設計製造了“復矩儀”，用於測量全國各地北極的高度。Between 724一725，Zhang led a large-scale project to identify the astro-geo-detic measurement of 13 places and，based on the results，concluded that the length of a degree of the meridian line was 351.27 li(131.3 kilometers)by the Tang measurement. This was the first measurement of the meridian ever done in the world.
公元724-725年，張遂組織了全國13個點的天文大地測量。從測量數據中，張遂得出了北極高度相差一度，南北距離就相差351裏80步(合現代131. 3千米)的結論。這個數據就是地球子午線一度的弧長。唐朝測出子午線的長度，在當時的世界上還是第一次。Beginning in 725，Zhang set out to revise the calendar, and finished the draft namely the Da Yan Calendar,before his death in 727. The new calendar was im-plemented in 728.
公元725年，張遂開始編訂曆法，至逝世前完成《大衍曆》草稿。公元728年《大衍曆》頒行。An innovative calendar in Chinese history，Da Yan Calendar inherited the strong points of calendars of the previous dynasties，while making improvement on the shortcomings and defects，making a significant breakthrough in the calendar-making field. The calendar provided a deep insight into the asymmetrical move-ment of the sun and the moon. The most prominent point about it lies in the correct calculation with a new formula of the speed of the sun’s movement along the eclip-tic.
《大衍曆》是一部具有創新精神的歷法，它繼承了前朝曆法的優點和長處，對不足之處和缺點作了修正，因此，在曆法制定領域取得了重要突破。《大衍曆》對太陽和月亮的不均勻運動有很深見解，最突出的表現在，它運用新的公式比較正確地計算出太陽在黃道上運行的速度。Well organized and logically deducted，Da Yan Calendar was more precise than its predecessors，and it served as a benchmark for calendar makers for many dynasties afterwards.
《大衍曆》結構合理、邏輯嚴密，比以往各朝代曆法更精確，成爲後世曆法編制的經典模式。Da Yan Calendar was a leading calendar in the world at that time. In 717，Ja-pan sent Kibi Makibi to China to study astronomy，and when he went back to Ja-pan in 735，he brought with himself manuscripts of Da Yan Calendar，and the cal-endar was spread to Japan and used there for over a hundred years.
《大衍曆》是當時世界上先進的歷法。公元717年，日本派吉備真備來中國學習天文學，735年，吉備真備回國時帶走了《大衍曆》。於是《大衍曆》便在日本廣泛流傳起來，作爲曆法使用了100多年。
