Thursday, January 24, 2008


Late last night I drove home on the freeway in such pouring rain that the tires kicked up a permanent spray obscuring the road, and we all seemed to be floating. It was surreal.

This morning when I left Mass the clouds overhead were heavy, but they didn't extend to cover the sun in the southern sky. So I had the odd experience of driving in full sunlight and pouring rain at the same time. Naturally there was a very bright rainbow ahead of me, and a faint secondary rainbow with colors reversed outside of that. But there was also a very faint weird-looking partial rainbow immediately inside the bright primary rainbow. I'd seen secondary rainbows before, but I'd never seen nor heard of that third rainbow. Wikipedia tells all: it was a "supernumerary rainbow", which is
an infrequent phenomenon, consisting of several faint rainbows on the inner side of the primary rainbow, and very rarely also outside the secondary rainbow. Supernumerary rainbows are slightly detached and have pastel colour bands that do not fit the usual pattern. It is not possible to explain their existence using classical geometric optics. The alternating faint rainbows are caused by interference between rays of light following slightly different paths with slightly varying lengths within the raindrops.
How cool! I'm posting the picture from Wikipedia; that's pretty much what I saw.

A Minnesotan once informed me that California does not, in fact, have Weather. He thinks our mild change of balmy seasons fails to live up to the name. Yesterday at least he was wrong. :)

1 comment:

Eanah said...

I saw just a single rainbow on the drive to work this morning, but it was really bright and I could see the whole thing, end to end. It was gorgeous. It was hard to watch where I was driving and not just gawk at this huge, bright, full rainbow. :)

Cool about the supernumerary rainbows. I didn't know they exist!