Somewhere Under the Rainbow

Saccocio replies: For 20-odd years, having read Jearl Walker’s paper and a number of its references, ¹ I have attributed the rainbow’s dark zone to optical interference. A closer reading more clearly reveals that the mechanism is refractive, just as Chuck Adler and Mikolaj Sawicki point out. Both their understandings are supported by Walker; ² my earlier reading likely did not focus on that part of his discussion. Walker’s paper is highly detailed and describes what is and is not observable both in nature and in laboratory rainbow-simulation conditions. My thanks to Adler and Sawicki.