Assertion: rainbow | /r/MadeOf | a phenomenon of sunlight
Facets:
Source sentences:
text: In Song Dynasty China (960–1279), a polymath scholar-official named Shen Kuo (1031–1095) hypothesised—as a certain Sun Sikong (1015–1076) did before him—that rainbows were formed by a phenomenon of sunlight encountering droplets of rain in the air.