Wei Pu

Wei Pu (; Wade-Giles: Wei P'u) was a Chinese astronomer and politician of the Northern Song dynasty. He was born a commoner, but eventually rose to prominence as an astronomer working for the imperial court at the capital of Kaifeng. Wei became a trusted colleague of the famous Northern Song polymath statesman and scientist Shen Kuo, who served as the head official for the Bureau of Astronomy, and worked on various projects with Wei Pu.

Achievements at court When Shen Kuo became the Supervisor of the Directorate of Astronomy in 1072 AD, Wei Pu became Shen's protégé, and was eager to partake in Shen's ideal reforms to the Chinese calendar system. Shen Kuo calibrated the standard diameter of the sighting tube's width, hence allowing the observation of the pole star indefinitely (which had shifted since the time of Zu Geng in the 5th century). They established a system of observing and recording on a star map the exact coordinates of the planets, done three times a night for a total of five years. On the other hand, Wei Pu realized that the old calculation technique for the mean sun was inaccurate compared to the apparent sun, since the latter was ahead of it in the accelerated phase of motion, and behind it in the retarded phase. Hence, he incorporated solar motion into the eclipse theory. The elite, well-educated ministers and leading astronomers were also insulted by the fact that Wei Pu was born a commoner, yet held more expertise in his field than many of them. When Wei and Shen made a public demonstration using the gnomon to prove the doubtful wrong, the other ministers reluctantly agreed to correct the lunar error. This meant that only the very worst errors were corrected for planetary motion, and in his disappointment, Shen wrote, "How sad that the backbiting of that bunch of calendar-makers could have kept him from bringing his art to fruition!"