Water-powered Armillary Sphere and Celestial Globe Tower
The water-powered armillary (sphere) and celestial (globe) tower was designed by Su Song, a scientist who lived during the Northern Song dynasty. Su Song used the principles of the waterwheel and hydropower to create a device for marking time, similar to today’s clocks and watches. Gears are used to drive the movement of the celestial globe and armillary sphere, as well as to adjust the time. This tower consists of three levels in total. In the middle is the celestial globe. Above it is the armillary sphere, which is an astronomical observatory (that can only be viewed from the second floor). In front, on the bottom, is the pagoda-like clock consisting of five tiers. On the uppermost tier are three small doors. On the odd numbered hours, a figure dressed in red rings a bell. On the even numbered hours, a figure dressed in purple strikes a gong. In the center, a figure dressed in green strikes a drum every 15 minutes. On the second tier is a 24-hour time reporting system. Every hour, a different figure appears holding a plaque indicating the current hour. On the third tier is a device for telling the time to the quarter hour. That is, every 15 minutes a different figure appears holding a sign that indicates the current 15-minute period. The fourth and fifth tiers are for the nighttime. On the fourth tier a figure strikes a gong 38 times throughout the night, beginning at dusk and continuing until dawn. On the fifth tier, a figure appears with each strike of the gong, holding a sign showing the current nighttime interval.
The water-powered armillary (sphere) and celestial (globe) tower that is on display in the National Museum of Natural Science was reproduced from research on Su Song’s book Xin Yin Xiang Fa Yao (New Design for an Armillary Sphere and Celestial Globe). This was the first true-to-scale working model of this tower in the world. The original was designed and produced by Su Song and Han Gonglian during the Northern Song dynasty.
The term water-powered refers to the use of water to drive the astronomical observation equipment. Chinese astronomers and observers of the stars believed that “the sky constantly moves.” That is, nature is dynamic. Therefore, a stable and regular tracking device that could follow the rotation of the earth was developed that was driven by hydropower.
An armillary sphere is an instrument for observation that is based on coordinates. The ancient Chinese people followed the concept of “unity between people and the heavens.” They were nature lovers and believed that to understand nature, it was necessary to observe the skies.
Su Song designed the celestial globe before this tower. As its name suggests, it is a star chart in the shape of a sphere, simulating the constellations as they moved across the sky. Astronomers sat inside this globe to carry out astronomical observations.
The basic equipment in a modern observatory must fulfill the functions of observing and simulating the constellations and marking time. Therefore, this tower is an early predecessor to the modern observatory.
Su Song’s water-powered armillary (sphere) and celestial (globe) tower can be said to be an automated observatory. The entire structure is divided into three parts. On the top is the armillary sphere, in the middle is the celestial globe, and on the bottom are systems for marking time and providing power. Hydropower was used to drive all three of these: timing system, armillary sphere, and celestial globe, providing stable and consistent rotation.
The design of the system for marking time incorporates human figures that produce different sounds using different instruments at different time intervals. Other figures appear holding signs that display the current time interval.