The Myth And Science Of Rainbows

It hit me that there are at least two rainbows in Poul Anderson's Time Patrol series. Does anyone know of a third? Let's look back at the two that we know.

"'I will come to you on the rainbow,' Niaerdh plighted.

"So it was. So it is."

-Poul Anderson, "Star of the Sea" IN Anderson, Time Patrol (Riverdale, NY, December 2010), pp. 467-640 AT I, p. 469.

The goddess Niaerdh addresses the god Frae to whom she has become betrothed. Rather than retelling a familiar myth, Anderson here imaginatively reproduces an earlier stage of Northern European mythology. Myths explain the origins of natural phenomena like the rainbow and also the seasons:

"'Each autumn I will leave you and go back to my sea. But in spring I will come again. This shall be the year and every year henceforward.'" (ibid.)

Niaerdh coming on the rainbow would have made a colourful cover illustration if "Star of the Sea" had ever been published as a single volume.

For the second rainbow, see Words From A Danellian. In this passage, the Danellian, although not interested in the rainbow as such, uses the idea of diffraction to compare imperceptible alterations in the time stream to reinforcing and cancelling light waves. Is our temporal experience comparable to a vast rainbow? This suggests an even more intriguing cover illustration.