中英雙語話中國歷史名人 第79期:趙友欽

Zhao Youqin (1271~1335) was a Chinese astronomer, mathematician, and Daoist who calculated the value of π, constructed astronomical instruments, conducted experiments with a camera obscura, and compiled an influential astronomical compendium.

趙友欽(1271~1335 )，天文學家、數學家、道士。趙友欽算出了圓周率的值，建造了天文儀器，做了小孔成像實驗並編了一本有影響的天文學綱要。

Zhao was one of the patriarchs of the northern branch of the Quanzhen ("Complete Perfection") sect of Daoism.

趙友欽是全真教北宗掌門人之一。

His astronomical treatise Gexiang xinshu ("New Writing on the Symbol of Alteration") presents his cosmological theory featurfing a flat Earth inside a spherical Heaven, his explanation of the lunar and solar eclipses, and his experiments with a camera obscura to establish the relationship between the luminosity of an image of a source of light and the distance of the source from the pinhole.

趙友欽的天文學論文《革象新書》展示了他的宇宙理論(他認爲天圓地方)、他對日月食的解釋以及確定光源與小孔的距離與所成之像的亮度之間的關係的試驗。

The book also describes his methods of remote surveying with gnomons to measure the distance from the Earth to the Sun, the Moon, and the stars, as well as his procedure for evaluating π using inscribed regular polygons of 4, 8, …, 16,384 sides.

這本書還描述了趙友欽用日晷測量地球與太陽、月亮和星星之間的距離的方法以及使用正多邊形估算圓周率的程序。

Following Liu Hui(flourished c. 263), this is the second extant Chinese procedure for the evaluation of π.

這是劉徽之後，我國現存的第二個估算圓周率的程序。

Zhao stated that his goal was to confirm the value 355 / 113 obtained by Zu Chongzhi (429~500), yet his calculations may have allowed him to prove the validity of the better evaluation 3.1415926<π<3. 1415927, also obtained by Zu.

趙友欽說他的目標是確證祖沖之的355/113，但是他的計算卻證明祖沖之估算的另一個值3. 1415926 < π <3.1415927是正確的。

The second extant book of Zhao, Xian Fo tongyuan ("On the Common Origins of [the Teachings of] Transcendentals and Buddhas"), is devoted to the so-called "Inner Alchemy," an esoteric discipline focusing on the attainment of immortality via respiratory and meditative practices.

趙友欽現存的第二本書是《仙佛同源》。這是一本“內丹”名著。內丹是一個抽象的學科，它集中處理通過呼吸和冥想練習達到長生不老的問題。

He designed several astronomical instruments; he used one of these to measure the difference in right ascension between two celestial bodies and another one to find the angular distance from the celestial north pole to a given star.

趙友欽設計了一些天文儀器;他用其中一個儀器測量兩個天體的赤經差，用另一個儀器測北極與某顆星的角距離。