Liu Xin
Liu Xin (ca. 50 BC – AD 23), later changed name to Liu Xiu , courtesy name Zijun , was a Chinese
Chinese people
The term Chinese people may refer to any of the following:*People with Han Chinese ethnicity ....

An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

, historian, and editor during the Xin Dynasty
Xin Dynasty
The Xin Dynasty was a Chinese dynasty which lasted from AD 9 to 23. It followed the Western Han Dynasty and preceded the Eastern Han Dynasty....

 (AD 9–23). He was the son of Confucian scholar Liu Xiang (77–6 BC) and an associate of other prominent thinkers such as the philosopher Huan Tan
Huan Tan
Huan Tan 桓譚 was a Chinese philosopher of the Han Dynasty and short-lived interregnum of the Xin Dynasty . Huan's mode of philosophical thought belonged to an Old Text realist tradition supported by other contemporaries such as the naturalist and mechanistic philosopher Wang Chong Huan Tan 桓譚 (c....

 (d. 28 AD). Liu created a new astronomical system, called "Triple Concordance". He published this system in the year 8 as section of his textbook. In it he provided the following periods:
  • The Moon
    The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

     phase period (synodic month): 29 43/81 days.
  • A total of 235 synodic months add up to 19 years.

Therefore his number of days in one year was 365.25016, which is 11 minutes longer than the current value.

Liu created a catalog of 1080 stars, where he used the scale of 6 magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

s. He also calculated periods for planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...


For centuries before the reign of Wang Mang
Wang Mang
Wang Mang , courtesy name Jujun , was a Han Dynasty official who seized the throne from the Liu family and founded the Xin Dynasty , ruling AD 9–23. The Han dynasty was restored after his overthrow and his rule marks the separation between the Western Han Dynasty and Eastern Han Dynasty...

 (r. 9–23) the Chinese had used the value of 3 for their calculation of pi
' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...

. Between the years 1 and 5, while working for the de facto head of state Wang Mang, Liu Xin was the first to give a more accurate calculation of pi at 3.154, although the exact method he used to reach this figure is unknown. However, the ancient record of Liu Xin's 'Jia Liang Hu' standard is still preserved in Beijing, which Joseph Needham
Joseph Needham
Noel Joseph Terence Montgomery Needham, CH, FRS, FBA , also known as Li Yuese , was a British scientist, historian and sinologist known for his scientific research and writing on the history of Chinese science. He was elected a fellow of the Royal Society in 1941, and as a fellow of the British...

 quotes below with modern references for archaic units (Wade-Giles
Wade–Giles , sometimes abbreviated Wade, is a romanization system for the Mandarin Chinese language. It developed from a system produced by Thomas Wade during the mid-19th century , and was given completed form with Herbert Giles' Chinese–English dictionary of 1892.Wade–Giles was the most...


The standardised chia liang hu (has) a square with each side 1 chhih (foot) long, and outside it a circle. The distance from each corner of the square to the circle (thiao phang) is 9 li 5 hao. The area of the circle (mu) is 162 (square) tshun (inches), the depth 1 chhih (foot), and the volume (of the whole) 1620 (cubic) tshun (inches).

Later mathematicians such as Zhang Heng
Zhang Heng
Zhang Heng was a Chinese astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar from Nanyang, Henan. He lived during the Eastern Han Dynasty of China. He was educated in the capital cities of Luoyang and Chang'an, and began his career as a...

 (78–139) and Liu Hui
Liu Hui
Liu Hui was a mathematician of the state of Cao Wei during the Three Kingdoms period of Chinese history. In 263, he edited and published a book with solutions to mathematical problems presented in the famous Chinese book of mathematic known as The Nine Chapters on the Mathematical Art .He was a...

 (fl. 3rd century) would improve Liu's calculation for pi approximate to the standard of pi used in modern times.

Although Liu Xin was originally a loyal partisan of Wang Mang, after Wang's troops suffered defeat on July 7, 23 at the Battle of Kunyang
Battle of Kunyang
The Battle of Kunyang was fought between June–July in 23AD, between the resurgent Han and Xin forces. The Han forces were led by Liu Xiu, while the far more numerous Xin were led by Wang Yi and Wang Xun...

, Liu Xin plotted with others to overthrow Wang Mang. The plot was discovered, and all the conspirators committed suicide or were executed.

A crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 on Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

was named in his honor.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.