Abstract

This article analyzes the method of orienting a gnomon developed by the eleventh century Chinese scientist Shen Kuo and described in his Ying Biao Yi. I argue that Shen Kuo’s criticism of the traditional orientation method was built on his belief that the earth is flat. The method Shen Kuo presented aims first to find the center of the earth, and only then to orient the gnomon to the cardinal directions. In addition, Shen Kuo developed two new techniques for improving observation with a gnomon: the first method sets the gnomon in a closed chamber with only a small slit for the entrance of the noon sunlight, thereby reducing ambient light and making it easier to see the gnomon’s shadow. Shen’s other innovation is to use a second gnomon together with the first. This can greatly weaken the shadow’s penumbra.