The Armillary Sphere
浑仪
The Armillary Sphere was an astronomic observatory instrument in ancient China. The ancient people believed the heaven was round，just like an egg，with the stars in the sky resembling the round pills beset in the shell and the earth like the yolk. People used the armillary sphere to examine the posi-tion of celestial bodies from the earth.
浑仪是中国古代的一种天文观测仪器。古人认为天是圆的，形状像蛋壳，出现在天上的星星是镶嵌在蛋壳上的弹丸，地球则是蛋黄。人们使用浑仪在这个蛋黄上测量天体的位置。
The armillary sphere’s structure was very simple at the very beginning，with three rings and a metal axis. The outermost ring-meridian ring-was fixed in the north-south direction，the middle ring-equator ring-was parallel to the earth’s e-quatorial plane，and the innermost one-Chijing ring-could revolve around the metal axis. The Chijing ring and the metal axis intersected at two points，with one pointing to the North Pole and the other to the South Pole. An observatory tube was fixed on the Chijing ring and could rotate around the center of the ring.
最初，浑仪的结构很简单，只有三个圆环和一根金属轴。最外面的那个圆环固定在正南北方向上，叫做“子午环”;中间固定着的圆环平行于地球赤道面，叫做“赤道环”；最里面的圆环可以绕金属轴旋转，叫做“赤经环”；赤经环与金属轴相交于两点，一点指向北天极，另一点指向南天极。
When used for examining the position of stars，the tube was first aimed at a certain star; then the graduation on the equator and Chijing rings was used to pin-point the star’s position in the sky.
在赤经环面上装着一根望筒，可以绕赤经环中心转动，用望筒对准某颗星星，然后，根据赤道环和赤经环上的刻度来确定该星在天空中的位置。
Later, in order to facilitate the observation of more celestial bodies，such as the sun，the planets，and the moon，more rings were added inside the armillary sphere，making it a multi-purpose astronomic instrument.
后来，古人为了便于观测太阳、行星和月球等天体，在浑仪内又添置了几个圆环，使浑仪成为多种用途的天文观测仪器。