16 Facts About Guo Shoujing

Guo Shoujing, courtesy name Ruosi, was a Chinese astronomer, hydraulic engineer, mathematician, and politician of the Yuan dynasty.

In 1231, in Xingtai, Hebei province, China, Guo Shoujing was born into a poor family.

Guo Shoujing was raised primarily by his paternal grandfather, Guo Yong, who was famous throughout China for his expertise in a wide variety of topics, ranging from the study of the Five Classics to astronomy, mathematics, and hydraulics.

Guo Shoujing was a child prodigy, showing exceptional intellectual promise.

Guo Shoujing improved the design of a type of water clock called a lotus clepsydra, a water clock with a bowl shaped like a lotus flower on the top into which the water dripped.

Kublai realized the importance of hydraulic engineering, irrigation, and water transport, which he believed could help alleviate uprisings within the empire, and sent Liu Bingzhong and his student Guo Shoujing to look at these aspects in the area between Dadu and the Yellow River.

Guo Shoujing became the chief advisor of hydraulics, mathematics, and astronomy for Kublai Khan.

Guo Shoujing has been credited with inventing the gnomon, the square table, the abridged or simplified armilla, and a water powered armillary sphere called the Ling Long Yi.

The gnomon is used to measure the angle of the sun, determine the seasons, and is the basis of the sundial, but Guo Shoujing revised this device to become much more accurate and improved the ability to tell time more precisely.

In 1280, Guo Shoujing completed the calendar, calculating a year to be 365.2425 days, just 26 seconds off the year's current measurement.

In 1283, Guo Shoujing was promoted to director of the Observatory in Beijing and, in 1292, he became the head of the Water Works Bureau.

Guo Shoujing was a major influence in the development of science in China.

Guo Shoujing invented a tool which could be used as an astrological compass, helping people find north using the stars instead of magnets.

Guo Shoujing worked on spherical trigonometry, using a system of approximation to find arc lengths and angles.

Guo Shoujing stated that pi was equal to 3, leading to a complex sequence of equations which came up with an answer more accurate than the answer that would have resulted if he did the same sequence of equations, but instead having pi equal to 3.1415.

Guo Shoujing used mathematical functions in his work relating to spherical trigonometry, building upon the knowledge of Shen Kuo's earlier work in trigonometry.