Chinese astronomer and court official who built an extremely sophisticated astronomical clock. A diplomatic envoy from the Sung dynasty court to that of a "barbarian" emperor occupying northern China, Su-sung was embarrassed in 1077 to discover that his hosts' calendar was more accurate than that of his own emperor. He subsequently requested and received permission from the Sung emperor to build what he called a "heavenly clockwork." His astronomical clock, powered by a water wheel, was completed in around 1090. It stood the equivalent of five stories in height and included an armillary sphere and several carved figures used to indicate the time. With the change of emperors following the death of his patron, however, the clock was allowed to fall into disrepair.