Experimental Research on the South-Pointing Loadstone Spoon (Sinan)1

Abstract

: In the 1940s, Wang Zhenduo 王振铎 re-created the sinan 司南 (south-pointing loadstone spoon) mentioned in ancient texts. However, subsequent researchers were unsuccessful in their attempts to replicate this design, resulting in longstanding questions over its feasibility. Loadstones with high natural remanent magnetization acquired today resemble the magnetism of those recorded in premodern Chinese documents. By simulating ancient stoneware processing techniques, a loadstone was cut and polished into a spoon shape. It was found that during the course of processing the loadstone spoon, demagnetization was negligible, while after completion, the internal magnetic field was rebalanced due to the change in shape, and the magnetic moment decreased slightly then stabilized for the long term. Experiments of this sort carried out by the author have testified to the enduring and reliable directivity of the resulting loadstone spoon. Paleo-magnetic research indicates that over the past two millennia the horizontal component of the geomagnetic field intensity in northern China underwent a clear M-shaped development. The level in the Qin and Han dynasties is approximately double that of the current day. Using a simulated ancient geomagnetic field, experiments have revealed that multiple methods, such as the “water floating method ” and “ hanging method ,” could manifest a degree of geo -directivity. The comprehensive studies carried out demonstrate that the loadstone spoon is the most optimal among these diverse means for attaining magnetic directivity from the Pre-Qin period (before 221 BCE) to the Tang dynasty (618 – 907 CE) in view of the availability of loadstone, the state of the geomagnetic field, and existing knowledge and techniques.