Jang Yeong-sil was a slave, and his family served a high-ranking official in the field of science and technology. In 1421, he studied in China under King Sejong’s command and returned after learning various astronomical instruments. Then in 1423, he escaped from the status of slaves and served as a court engineer.

He completed the Honcheon-ui in a year and created the first water clock in Korea, the Clepsydra. In 1441, he invented the word’s first rain gauge. This enabled the flooding of streams to be known in advance. After the astronomical instrument project, he continued to work as an expert in metal smelting.

The following year, however, the king’s kiln, which he directed, was broken under his watch. As a result, he was arrested by the Uigmbu for profanity and expelled from all government posts.

L.L.F reporter Na-gyeong Kim