Li Fan (Han dynasty)

Li Fan (Chinese: 李梵; pinyin: Lǐ Fàn) was a Chinese astronomer during the Han dynasty (202 BC – 220 AD).

He noticed that the Moon does not move uniformly through its phases by using background stars as reference.^{[citation needed]} In 85 Li Fan and Bian Xin (Chinese: 編訢) were tasked by Emperor Zhang to resolve inaccuracies in the Taichu calendar.^[1][2] He is also known to have worked with inflow clepsydras as opposed to earlier, typically less accurate outflow clepsydras.^[3]

The measurements of synodic periods of the planets given in the following table are attributed to him.^[4]

Comparison of Li Fan's values for the synodic periods of the planets^[4]

Planet	True value (days)	Li Fan's value (days)
Mercury	115.877	115.881
Venus	583.921	584.024
Mars	779.936	779.532
Jupiter	398.884	398.846
Saturn	378.092	378.059

Li Fan crater on Mars (picture by Viking 1)

An impact crater that is located at the Phaethontis quadrangle, Mars, 47.2°S Latitude and 153.2°W Longitude was named in his honor. The diameter of the impact crater is approximately 104.8 km.

References

1. Crespigny, Rafe de (2007). A Biographical Dictionary of Later Han to the Three Kingdoms (23–220 AD). Leiden: Brill. p. 410. ISBN 9789047411840.
2. Cullen, Christopher (2017). The Foundations of Celestial Reckoning: Three Ancient Chinese Astronomical Systems. Routledge. pp. 139, 377. ISBN 9781138101173.
3. Needham, Joseph (1959). Science and Civilisation in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth. Cambridge University Press. p. 320. ISBN 9780521058018.
4. Needham, Joseph (1959). Science and Civilisation in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth. Cambridge University Press. p. 401. ISBN 9780521058018.