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Raindrops over Joseon – Sejong’s Cheugugi

King Sejong is most famous for the creation of the Korean alphabet, Hangul, which remains in use today. His whole career as king was underpinned by the philosophy that a king must serve his people, and this philosophy gave rise to many advances in science and culture that benefited the people of Korea.

One less celebrated achievement was the development of the world’s first rain gauge, called ‘Cheugugi’ (측우기), in 1442, which has yet to be improved upon by modern science. Wait, stay awake! Let me explain why this was an important development, and why China is keen to claim the credit for its invention today.

A Cheugugi model from 1770
A Cheugugi model from 1770. Rainfall was classified according to 8 categories: minor rain (미우); delicate rain (세우); light rain (소우); moderate rain (하우); damaging rain (쇄우); running rain (취우); heavy rain (대우); and ferocious rain (폭우).

The Cheugugi enabled precise measurements of rainfall to be taken all around the country over a period of 400 years, detailing the month, location, time of day and type of rain. The Confucian values of Korea encouraged an understanding of nature, which today we would recognise in terms of concepts such as meteorology. Sejong’s scientists made similar measurements of the wind, with a specially designed anemometer. In the first half of the 15th century, no other nation was monitoring weather conditions with precision and on a nationwide basis.

This was also partly an effort by the government to take a more scientific approach to agriculture, and the benefits of this research were felt by everyone in the kingdom, through the publication of such texts as ‘A Plain Guide to Farming’ (Nongsa Chiksol) in 1429, several years before the rain gauge was completed.

No examples of the Cheugugi survive from King Sejong’s day, but one dating from the 18th century was identified in 1910 by a researcher, and owing to an inscription referring to the Ching dynasty, it was erroneously ascribed to China. Unaware that Koreans used both Korean dynasties and Chinese dynasties to refer to specific periods, scholars in both East and West today accept this view.

While the records of the development of the Cheugugi remain in the annals of Choson from the years 1441 to 1442, there is no reference to ‘Cheugugi’ in Chinese literature, nor any historical evidence of a similar instrument being used in China.

Now you can get your Starbucks.

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