Audio Guide：

13th-century Chinese astronomer Guo Shoujing revised and simplified the armillary sphere from the Tung and Song Dynasty. The ecliptic armillary sphere was the first modern coordinate system for used for the observation of the ecliptic. A sundial is a device used to tell time of the day by measuring the shadow cast by the Sun. You can learn more about the simplified armillary sphere, the ecliptic armillary sphere, and the sundial with the holograms on display.