Result: Thanks to Dan Russell’s thoughtful answer and others’ constructive comments, the puzzle statement has been reupholstered, the puzzle has been reopened, and a complete solution is imminent.
Original post
The rainbow mystery below was readily understood by three posters and two other commenters as the puzzle it was meant to be. The three posted answers presented astutely-targeted partial solutions based on clues, well before “off topic” voting began and led to closure even though this puzzle was off to a good start with no symptoms of being off topic.
Question of consistency: Is there something about this puzzle that lands it in the same bin as a mathematics “problem” vs puzzle?
Bonus question:
Should it have been presented differently?
Admittedly, less time was spent on wording than on the picture
and I would understand
downvotes and constructive comments
rather than closevotes.
$\small\dfrac{ \raise-.8ex{\scriptsize+} \raise-1ex5 \, }0 ~$ Two many rainbows? [on hold]
Wish I’d had a camera at the time, but a cartoon will have to do.
This represents a direct view of two actual incomplete rainbow arcs that stop in midair where they cross, lit only by a setting sun. How could this be? I honestly wondered if it was a dream.
What is the simplest explanation for this odd pair of rainbows?
Why is the smaller one slightly brighter?
Notes. Each main arch was accompanied by a rainbow’s usual set of concentric fainter arcs, which exhibited the same phenomenon of stopping sharply where they crossed exactly above or below the main crossing point. Only air is between the point of view and the rainbows. Safe to guess that this effect never occurred more than a century or two ago. Some details of the real-life story have been altered in order to stymie internet searches.
The following comment registered stupefyingly many upticks.
I'm voting to close this question as off-topic because this belongs on physics.stackexchange.com.
– closevoter with, ironically, no apparent affiliation to physics.stackexchange.com
At least the commenter was considerate enough to share their reasoning, but the confident tone may have misled others to take evaluation shortcuts as it might have given the impression that someone had already accurately assessed the puzzle. When this comment’s upticks correlated to closevotes, astonishment led to the impression that all closevoters combined for almost no apparent presence whatsoever at any science SE sites, finding a total of one comment and one all-but-ignored post at any such site, which was not Physics SE. Update: 4 of the upticks may have been automatically applied by the system without closevoters specifically endorsing the comment’s details.
Did any closevoter realize that essentially the same puzzle could have been stated without science, in terms of [clickable/hoverable hint /spoiler] for example? A pair of rainbows is just an especially intriguing manifestation of the solution, with natural clues that make it a better puzzle, and happens to be how the paradox presented itself in real life.
Did any closevoter genuinely imagine a complete solution that would verify that this is not a puzzle? The solution is quite simple and probably understandable by most solvers, but does hinge on a less-than-obvious aha-like detail from everyday experience.
Perhaps we could see specific reasoning posted here from those who voted to close, but please do not be tempted into defensive rationalization.
Mistaken closures based on hunches occur often enough that I openly suspect this to be merely another instance and hope that we can clarify a nebulous border between on- and off-topicality.
