From Slave to Prolific Scientific Inventor - Jang Yeong-sil

Jang Yeong-sil (?-?), who lived at the beginning of the Joseon dynasty during the first half of the 15th century, is admired as one of the greatest scientific minds of Korean history, having created numerous inventions relating to astronomy, time-telling, and more.

Jang’s father came from a noble family of ethnic Chinese descent and had served as a high official in the Goryeo government. However, as his mother was a government-owned female entertainer (gwangi, ginyeo), Jang’s social status was that of a government-owned slave (gwanno) – part of the lowest class in Joseon society. Despite this, word of his skillful and clever workmanship spread, and both Kings Taejong (r. 1400-1418) and Sejong (r. 1418-1450) cherished and looked after Jang. Acknowledging Jang’s skilled abilities, extraordinary intelligence, and faithful service, Sejong sent Jang to China to research astronomical devices – an extremely rare privilege for a slave. King Sejong was eager to support a promising individual like Jang, despite his birth, because he sought to improve the lives of the citizens via advances in agricultural knowledge and technology, which demanded progress in scientific research and invention. After Jang returned from China, his status was elevated to that of a (commoner (yangin) and he was appointed by the king to work in the palace in 1422-3.

In the following years, Jang devised a number of scientific technologies. These included astronomical instruments such as a celestial globe (honcheonui), a water clock (jagyeokru), over six types of sundials (ilgu), a rain gauge (cheugugi), a water gauge (supyo), and various technologies relating to weaponry. These technologies were often ordered to be produced by the king, who had heard of their existence in other countries. Jang referenced Chinese and Arabian texts to create his inventions, but as these instructions were incomplete, a significant amount of design had to be done by Jang and his colleagues. His inventions were installed within Gyeongbokgung Palace for use by royal astronomers to track celestial movements and the seasons, but also on the streets to inform people of the time.

In 1442, a sedan chair which was designed by Jang broke while the king was being carried inside. Jang was deemed responsible, and, though the king opposed it, was expelled from the palace. Nothing is recorded of his life thereafter.

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  Illustration of Jang Yeong-sil

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  Sundial exhibited in Deoksugung Palace (Jung-gu, Seoul)

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  Water clock exhibited in Deoksugung Palace (Jung-gu, Seoul)

[A digital clock in Joseon Borugak Jagyeongnu (K-HERITAGE)]

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