South-pointing chariot
| South-pointing chariot | |||||||||||
| Traditional Chinese | 指南車 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Simplified Chinese | 指南车 | ||||||||||
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| Transcriptions | |
|---|---|
| Standard Mandarin | |
| Hanyu Pinyin | zhǐ nán chē |
| Yue: Cantonese | |
| Jyutping | zi2 naam4 gui1 |
The south-pointing chariot (or carriage) was an ancient Chinese two-wheeled vehicle that carried a movable pointer to indicate the south, no matter how the chariot turned. Usually, the pointer took the form of a doll or figure with an outstretched arm. The chariot was supposedly used as a compass for navigation, and may also have had other purposes.
There are legends of earlier south-pointing chariots, but the first reliably documented one was created by Ma Jun (c. 200–265 CE) of Cao Wei during the Three Kingdoms, about eight hundred years before the first navigational use of a magnetic compass. No ancient chariots still exist, but many extant ancient Chinese texts mention them, saying they were used intermittently until about 1300 CE. Some include information about their inner components and workings.
There were probably several types of south-pointing chariot which worked differently. In most or all of them, the rotating road wheels mechanically operated a geared mechanism to keep the pointer aimed correctly. The mechanism had no magnets and did not automatically detect which direction was south. The pointer was aimed southward by hand at the start of a journey. Subsequently, whenever the chariot turned, the mechanism rotated the pointer relative to the body of the chariot to counteract the turn and keep the pointer aiming in a constant direction, to the south. Thus the mechanism did a kind of directional dead reckoning, which is inherently prone to cumulative errors and uncertainties. Some chariots' mechanisms may have had differential gears. If so, it was probably the first use of differentials anywhere in the world.
The south-pointing chariot, a mechanical-geared wheeled vehicle used to discern the southern cardinal direction (without magnetics), was given a brief description by Ma's contemporary Fu Xuan. The contemporary 3rd century CE source of the Weilüe, written by Yuan Huan also described the south-pointing chariot of Ma Jun. The Jin Dynasty (265–420 CE) era text of the Shu Zheng Ji (Records of Military Expeditions), written by Guo Yuansheng, recorded that south-pointing chariots were often stored in the northern gatehouse of the Government Workshops (Shang Fang) of the capital city. However, the later written Song Shu (Book of Song) (6th century CE) recorded the south-pointing chariot's design and use in further detail, as well as created background legend of the device's (supposed) use long before Ma's time, in the Western Zhou Dynasty (1050–771 BCE). The book also provided description of the south-pointing chariot's re-invention and use in times after Ma Jun and the Three Kingdoms. The 6th century CE text reads as follows. (In this translation, by Needham, the south-pointing chariot is referred to as the south-pointing carriage.
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