Jang Yeong-sil was a prominent Korean scientist and inventor during the Joseon Dynasty. Born in 1390, he is best known for his contributions to astronomy and engineering. Jang developed various scientific instruments, including the rain gauge and water clock, which significantly advanced the understanding of time and weather in Korea. His work in astronomy led to the creation of the first accurate celestial globe in Korea. Jang Yeong-sil's innovations not only improved agricultural practices but also enhanced the accuracy of timekeeping and navigation, making him a key figure in the scientific history of Korea.