周髀算經

Step into an ancient conversation about the origins of mathematics, astronomy, and measurement. Through exchanges between Zhou Gong, Shang Gao, Rong Fang, and Chen Zi, the work asks how people can determine the dimensions of the heavens and the earth when neither can be reached directly. Its answers begin with the square, the circle, the carpenter’s square, and the celebrated three-four-five triangle.

The discussion then develops into a detailed system of practical observation and cosmic calculation. Readers encounter methods for using shadows, measuring height and distance, estimating the sun’s size and path, determining solstices and equinoxes, and mapping the movements of the sun, moon, and stars. Alongside its numerical procedures, the text presents an early vision of a round heaven above a square earth, linking geometry to the ordering of nature and the calendar. Best heard as a meeting of philosophical dialogue, field experiment, and mathematical proof, it offers a remarkable glimpse into ancient Chinese scientific thought.