Zhu Zaiyu

Zhu Zaiyu (1536 to 1611) was a Chinese scholar, mathematician and music theorist, and a prince of the Ming dynasty. Born in Qinyang in Henan Province into an aristocratic family, he was a sixth-generation descendant of the Hongxi Emperor. He inherited the title Prince of Zheng in 1593 but quickly resigned it to his cousin, and in 1606, the year he delivered a set of ten musicological treatises to the court, he was granted a new princely title by order of the emperor. In 1584 he described equal temperament by accurate mathematical calculation, and three of his music theory works are associated with that idea. He also wrote treatises on astronomy, physics, mathematics and calendrics, calculated the magnetic declination of Peking and the mass density of mercury, and accurately described the length of the tropical year to correct the Ming calendar. His work on equal temperament won no official recognition in his lifetime or under the Qing, because the Ming and Qing courts favoured classical scholarship over ideas based on empirical observation.