section_path: Scholarly achievements/Meteorology
section_name: Meteorology
paragraph_text: Meteorology
  
  Early speculation and hypothesis pertaining to what is now known as meteorology had a long tradition in China before Shen Kuo. For example, the Han dynasty scholar Wang Chong (27–97) accurately described the process of the water cycle. However, Shen made some observations that were not found elsewhere in Chinese literature. For instance, Shen was the first in East Asia to describe tornadoes, which were thought to exist only in the Western hemisphere until their observation in China during the first decade of the 20th century.
  
  Shen gave reasoning (earlier proposed by Sun Sikong, 1015–1076) that rainbows were formed by the shadow of the sun in rain, occurring when the sun would shine upon it. Paul Dong writes that Shen's explanation of the rainbow as a phenomenon of atmospheric refraction "is basically in accord with modern scientific principles." In Europe, Roger Bacon (1214–1294) was the first to suggest that the colors of the rainbow were caused by the reflection and refraction of sunlight through rain drops.
  
  Shen hypothesized that rays of sunlight refract before reaching the surface of the earth, hence people on earth observing the sun are not viewing it in its exact position, in other words, the altitude of the apparent sun is higher than the actual altitude of the sun. Dong writes that "at the time, this discovery was remarkably original." Ibn al-Haytham, in his Book of Optics (1021), also discussed atmospheric refraction in regard to twilight.