雙語科技百科(天文) 第18期 《授時歷》
Shoushi Calendar
Shoushi Calendar，the most outstanding calendar in ancient China，was compiled by Guo Shoujing，a prominent scientist in the Yuan Dynasty，and his colleagues. Enforced in 1281,throughout the Ming Dynasty and the begin-nin4 of the Qinq Dynasty，the calendar was used for over 360 years.
《授時歷》是中國古代最優秀的歷法。由元代著名科學家郭守敬等人編制，從1281年開始實行，歷經整個明代，一直到清初，共用了360多年。The reason why the calendar was used for such a long time has much to do with its accuracy in calculation. In the first place，it employed astronomical docu-ments of the highest accuracy in its time. For instance，it set the tropical year at 365.2425 days，which was the exactly the same as that in the currently used Gre-gorian Calendar, 301 years preceding the latter though. Secondly, based on earlier scholars finding that the length of the tropical year was gradually shortening，the Shoushi Calendar held that the tropical year shortened by 0. 0001 day every 100 years，which was more accurate as compared with earlier researches.
《授時歷》之所以沿用這麼長時間，和它的計算精度非常高有很大關係。首先，它使用了當時最爲精確的天文資料。例如，它確定了迴歸年的長度爲365.2425日，與現今通行的公曆值完全一致，但是它比格里高利曆早了301年。其次，它吸收了前人研究發現的迴歸年的長度在逐漸變小的觀點，規定100年中迴歸年的長度減小0. 0001日。與前人研究相比，這個數值要精確一些。
In addition，instead of the mathematical method of recording astronomical documents via complicated fractions，the calendar employed decimal fractions，which largely reduced calculation workload and guaranteed accuracy. It also made innovations in terms of calculation methods;for instance，the use of mathematical approaches like cubic interpolation，polynomial equations to the 4th order and spherical trigonometry.
另外，《授時歷》廢除了用複雜分數表示天文資料的辦法，使用小數制，不僅大大減少了計算量，也保證了計算精度。《授時歷》在計算方法上也有創新，例如三次插內插法、四次多項式方程、球面三角法等數學方法的使用。Soon after its compilation，the Shoushi Calendar was Spread to and adopted by Japan and Korea. In recent years，astronomers from Japan，European and North American countries are again showing interests in ahe Shoushi Calendar，and some broad and in-depth researches have been made. As an advanced and accurate calendar in the history of China，the Shoushi Calendar also occupies a distinct posi-tion in the history of world astronomy.
《授時歷》編制不久即傳播到日本、朝鮮，並被採用。近年來日本和歐美等國的天文學家對《授時歷》產生了新的興趣，進行了廣泛而深入的研究。作爲中國歷史上一部先進的、精確的歷法，《授時歷》在世界天文學史上也佔有突出的位置。
