Guo Shoujing

Guo Shoujing , courtesy name Ruosi , was a astronomer, engineer, and mathematician born in and lived during the Yuan Dynasty . The later Johann Adam Schall von Bell was so impressed with the preserved astronomical instruments of Guo that he called him "the Tycho Brahe of China."

Early life

Guo's father died while he was a child, so he was brought up by his grandfather Guo Yong, who was famed as an expert in a wide range of topics from classical studies to mathematics and hydraulics.

By the age of 15 or 16, he obtained a blueprint for a water clock, and soon realized its principles of operation.

Contributions

He worked on improving the Chinese gnomon and worked at Kublai Khan's Gaocheng Astronomical Observatory. He set 27 observation centers in different parts of China. There he formulated the in 1281 and calculated the year to be 365.2425 days, only 26 seconds off the real time; this is the same as the Gregorian calendar, but 301 years earlier. It would be used for the next 363 years, the longest a calendar would be used in Chinese history. building upon the knowledge of Shen Kuo's . It is debated amongst scholars whether or not his work in trigonometry was based entirely on the work of Shen, or whether it was partially influenced by Islamic mathematics which was largely accepted at Kublai's court. An important work in trigonometry in China would not be printed again until the collaborative efforts of Xu Guangqi and his Italian Jesuit associate Matteo Ricci in 1607, during the late Ming Dynasty.

He devised a number of astronomical instruments, and conducted large-scale geodetic surveys and celestial observations. Although he did a great deal on the modern calendar, he suggested pi 3, unlike Zu Chongzhi's 3.14159265 and Zhang Heng's 3.142.

In engineering he is best known for constructing the artificial Kunming Lake in Beijing as a and part of a new waterway for grain transport.

Asteroid 2012 Guo Shou-Jing is named after him.