Oldest Astronomical Instrument Discovered in China

A Replica of the Gnomon with Template from the Tomb of XIAHOU Zao(Image by SHI Yunli)

Chinese scientists have proposed that an object collected 35 years ago from a tomb of the Western Han Dynasty in Fuyang city and called “lacquerware of unknown names” could be a gnomon with template.

In 1977, archaeologists unearthed a great number of precious relics from the tomb of XIAHOU  Zao(?-165BCE), the 2nd Marquis of Ruyin of the Western Han dynasty. They named a piece of lacquerware “lacquerware of unknown name”, for no one has been able to identify it. Divergent views also have been held over the possible function of a pair of overlapping lacquered disks from the same tomb.

A team of Yunli Shi, a professor at the Department of the History of Science and Scientific Archaeology, University of Science and Technology of China, has now proposed that the object is a special gnomon with template, while a pair of lacquered disks is an equatorial device for the positional observation of celestial bodies. Both are the oldest astronomical measuring instruments with definite information of date that can still be seen in the world. The findings appear in the Studies in the History of Natural Sciences.

The gnomon with template is a typical instrument used by ancient Chinese astronomer in determining the advent of different seasons with the gnomon shadows cast on the template by the midday sun. It consists of a vertical pole and a level template laid in south-north direction at the foot of the pole. The gnomon with template from the tomb of XIAHOU Zao has two symmetric and foldable parts. As being fully set up in the south-north direction, the midday sun will cast the shadow of a vertical tablet in the northern half onto three fixed positions on the template respectively on the days of the Summer Solstice, the Vernal/Autumnal Equinoxes, and the Winter Solstice.

“Geographically, this type of gnomon with template can only be used on the given latitude, and the one from the tomb of Xiahou Zao fits just right with the region between the capital of the dynasty Chang’an and the fief of the Marquis of Ruyin Fuyang,” explained Prof. Shi.

The edges of the two overlapping disks are marked respectively with the complete degrees of a celestial circle, and the names and degrees of each of the 28 lunar lodges.

Previous studies have suggested that they may make either an astrological tool similar to the two cosmic disks for divination from the same tomb, or a kind of astronomical instrument, but both theories are in need of definite evidence.

Mounted on top of a lacquerware box, the disks form a complete device good for the equatorial observation fitting just right with the geographical latitude of Fuyang, a prefecture-level city in northwestern Anhui province, China.

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