Last Friday typhoon 21 passed through Kyushu, Shikoku and Kinki District, and gave much damage at many places, especially in Mie Prefecture, due to heavy rainfall. Another thing it brought was a rainbow seen here in Sakai next morning.
Leonard Mlodinow writes the following story in his book "Feynman's Rainbow" : On one of the last days in his life, Richard Feynman was gazing at a rainbow, and asked Mlodinow what he thought was the salient feature of the rainbow that had inspired Descartes' mathematical analysis of it. The latter gave elaborate guesses based on the geometrical and physical nature of the rainbow, but Feynman simply said this: It might have been that Descartes thought rainbows were beautiful.
You can learn about Descartes' analysis of the rainbow at websites [2,3].