Do not all charms fly
At the mere touch of cold philosophy?
There was an awful rainbow once in heaven:
We know her woof, her texture; she is given
In the dull catalogue of common things.
Philosophy will clip an Angel’s wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomèd mine—
Unweave a rainbow, as it erewhile made
The tender-person’d Lamia melt into a shade.-John Keats, Lamia (1820)
Poet John Keats (1795-1821) once famously — and infamously — joked that Isaac Newton had destroyed the poetry of the rainbow by “reducing it to the prismatic colors.” This statement has been quoted often whenever someone wants to argue that scientific knowledge dulls the beauty and poetry of nature.
Keats was being an idiot, though: a true understanding of the science behind a phenomenon only adds to its beauty. There are so many subtle aspects to even the simple optics of a rainbow that make it a fascinating and lovely subject of contemplation. Once you get past the basic science of a rainbow, you are well-prepared to study more sophisticated and unusual phenomena such as this double rainbow that my wife and I saw from our house last July.
Double rainbow. It was, in fact, all the way.
I’ve had rainbows on my mind since I was recently asked to explain some of the optics by a journalist. Surprisingly, standard optics textbooks such as Born and Wolf’s Principles of Optics and Hecht’s Optics have no discussion of the phenomenon. This is likely due to the fact that most optical scientists have no need to understand rainbows in their research, but this does not mean they are not objects worthy of study.
So let me endeavor to explain all about rainbows: how they form, how double rainbows form, when fully circular rainbows form, and anything else I can think of. This isn’t just trivia: a lack of knowledge of rainbows can lead to truly humiliating consequences.
Skulls in the Stars 
