The Han dynasty was the second imperial dynasty of China, preceded by the Qin dynasty and succeeded by the Three Kingdoms. Spanning over four centuries, the period of the Han Dynasty is considered a golden age in Chinese history. The Han Empire was divided into areas directly controlled by the central government, known as commanderies, and a number of semi-autonomous kingdoms. The Han dynasty was an age of economic prosperity, and saw a significant growth of the money economy first established during the Zhou dynasty. The coinage issued by the central government mint in 119 BCE remained the standard coinage of China until the Tang dynasty. The emperor was at the pinnacle of Han society. He presided over the Han government, but shared power with both the nobility and appointed ministers who came largely from the scholarly gentry class. From the reign of Emperor Wu onward, the Chinese court officially sponsored Confucianism in education and court politics. Science and technology during Han saw significant advances, including papermaking, the rudder, the use of negative numbers in mathematics, the raised-relief map, the hydraulic-powered armillary sphere for astronomy, and a seismometer employing an inverted pendulum.