Shen Kuo (1031-1095) was from Qiantang (in today's Hangzhou, Zhejiang Province). He was a scientist of profound learning who possessed a wide range of knowledge. Shen Zhou, his father, was a low-ranking official below the county level, honest and upright in his ways. His mother Xu was a woman of fine cultural accomplishment. With such a family background, Shen Kuo had an admirable upbringing. Shen Kuo, steeped in astronomy and calendars, once assumed the office of Sitianjian.
Shortly after Shen took office, his superior asked him: "Is the shape of the sun and the moon round or phased like a fan?" Shen Kuo had researched the problem long before and therefore answered readily: "Both are round like a ball. How do I know this? The evidence is in the waxing and waning of the moon. The moon has no light of its own. When the sun shines upon it, it reflects the light and also gleams.
A crescent is formed because the sunlight only shines upon part of the moon, making it appear like a hook. When the moon is revolving around the earth and slowly moving farther from the sun, the sunlight reaches it at different angles, and the moon gradually appears rounder. Let us take a ball, for example. If we paint half of the ball and view it sideways, it looks like a hook; and if we look at it squarely, it looks round – from this we may determine the shape of the sun and the moon. "
As a historical figure who had lived ten centuries ago, it is truly remarkable that Shen Kuo described in such explicit terms, the shape of the sun and the moon, the source of moonlight, and the reasons for the waxing and waning of the moon.
Shen Kuo, in his twilight years, lived in seclusion. He had a garden built outside the seat of Renzhou Prefecture, naming it Meng Xi (Dream Brook). Shen lived there for eight years, not only fishing, boating, playing music and composing poems, but also spending his time reading and writing. He wrote down his experiences from his life and research in a book with academic themes, entitled Meng Xi Bi Tan (Dream Brook Sketchbook).
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