雙語科技百科(天文) 第11期:漏水轉渾天儀
The Water一driven Armillary Sphere
In the middle of the Eastern Han Dynasty, Zhang Heng，an outstanding astronomer, made bold innovations to the armillary sphere，and de-signed and made the first water-driven armillary sphere in the world to measure the position of celestial bodies，which was carved with known important astronomical phenomena. People could observe the movement of the sun，the moon and the stars.
漢中期，傑出的天文學家張衡對渾儀作了大膽創新，設計並製作了漏水轉渾天儀。張衡還製造出了世界上第一架測量天體位置的水運渾天儀，凡是已知的重要天文現象，都刻在這架儀器上。人們可以通過渾天儀觀測到日月星辰運行的情況。To enable the armillary sphere to rotate，Zhang employed the gear system，linking the celestial globe with the kettle clepsydra. Powered by the water leaked out of the kettle，the gear drove the celestial globe to rotate around the axis，one day per circuit, in synchronization with the celestial body(sun) this way，the celestial changes were presented observing the instrument，one could know when a star rose in the east and set in the west.
漏水轉渾天儀的主體是一個代表天球的球體模型。球裏面有一根鐵軸貫穿球心，軸的方向就是天球的方向，也是地球自轉軸的方向。軸和球有兩個交點，一個是北極(北天極)，一個是南極(南天極)。爲了讓渾天儀能自己轉動，張衡採用齒輪系統把渾象和記時用的漏壺聯繫起來，用漏壺滴出來的水的力量帶動齒輪，齒輪帶動渾象繞軸旋轉，一天一週，與天球同步轉動，這樣，就可以準確地把天象的變化表示出來。人在屋子裏看着儀器，就可以知道某星正從東方升起，某星就要從西方落下。
The world’s first water-driven astronomic instrument with explicit historical re-cords，the new armillary sphere employed an extremely complex gear system. It was a proud achievement for ancient Chinese people to work out such a complex instrument. Unfortunately，the driving system was not handed down，as made in the remote past.
漏水轉渾天儀是有明確歷史記載的世界上第一架用水力驅動的天文儀器。渾天儀應用到的齒輪機構和凸輪機構十分複雜。遠在1800多年前，中國古人就可以造出這樣複雜的儀器是很值得自豪的。可惜的是，這套複雜的傳動系統因爲年代久遠沒有能夠流傳下來。
