Jang Yeong-sil

Jang Yeong-sil was a Korean inventor and scientific official of the Joseon dynasty, known for developing astronomical instruments, water clocks, and other devices.

Joseon dynasty: A Korean dynasty that ruled from 1392 to 1897 and established a centralized Confucian state. Jang Yeong-sil served in its court and built instruments for its government.
Jagyeokru: An automated water clock developed in Joseon Korea that announced the hours using figures and mechanical signals. Jang is credited with helping create this landmark timekeeping device.
Water clock: A timekeeping device that measures elapsed time through the controlled flow or change of water. The Jagyeokru applied water-clock principles to produce automated time signals.
Gyeongsang Province: A historic southeastern province of Korea, one of the country’s major administrative regions. Jang is traditionally associated with this region before entering royal service.
Joseon timekeeping: The systems and devices used in Joseon Korea to measure, announce, and coordinate time. Jang’s clocks contributed to the state’s effort to make time measurable and audible.
Sejong the Great: The fourth king of Joseon, whose reign from 1418 to 1450 supported major cultural and scientific projects. His patronage enabled Jang Yeong-sil’s rise and the development of court instruments.
Angbuilgu: A concave sundial developed in Joseon Korea, marked to show the time and seasonal movement of the Sun. It represents the portable, public-facing instruments linked to Jang’s workshop.
Escapement: A mechanism that regulates a clock’s motion by releasing energy in controlled, repeated steps. Regulated motion is central to turning a water clock’s flow into periodic signals.
Ming dynasty astronomy: Astronomical scholarship and instrument-making in China under the Ming dynasty, influential across East Asia. Joseon court science developed through exchange with Chinese astronomical traditions.
Korean calendar reform: Efforts to improve Korean calendrical systems through more accurate observations and astronomical calculations. Better instruments supported the calendar work that governed ritual and administration.

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