A Double Rainbow
A case where the folklore's instinct — 'this is special, and doubled' — matches real, distinctive physics, even though the physics wasn't understood at the time the belief formed. The secondary bow really is optically different from the primary one, not simply a fainter copy of it, and its colors genuinely run in reverse order.
Likely origin
Earliest known record: Widespread oral folk tradition across multiple cultures, no single dated origin
The doubled-fortune reading of a double rainbow shows up independently across more than one folk tradition without a single traceable founding source, which is consistent with a natural human response to noticing that a rarer, visually striking version of an already-special sight deserves an even stronger reading — the real optical explanation for why the second bow looks and behaves differently came only much later, through the physics of light and water droplets.
The second bow isn't just a fainter copy
It's easy to assume a double rainbow is simply a weaker echo of the primary one, but the physics involved is genuinely distinct. The primary rainbow forms from sunlight refracting into a water droplet, reflecting once off the droplet's inner back surface, and refracting again on its way out. The secondary bow forms from light that reflects twice inside the droplet before exiting — an extra bounce that loses some brightness, which is why the second bow always appears fainter, but also changes the light's exit angle enough to reverse the order the colors appear in.
Why the colors run backward
In the primary rainbow, red sits on the outer edge and violet on the inner edge. In the secondary bow, that order flips — violet on the outside, red on the inside — a direct, visible consequence of that second internal reflection changing the angle at which each wavelength of light exits the droplet. This is a genuinely reliable, checkable optical signature, not a matter of perception or lighting conditions, and it's part of what makes a double rainbow immediately identifiable as a distinct phenomenon rather than a duplicate.
Folklore doubled the meaning before anyone understood the mechanism
Long before anyone could explain internal reflection angles, more than one tradition independently arrived at roughly the same intuitive conclusion: something this rare and visually distinctive deserves an intensified reading rather than a diminished one, treating the second bow as doubling the first bow's good fortune rather than introducing a competing or different meaning. It's a case where folk intuition and real physics happen to point the same direction — the sight genuinely is special and genuinely is optically distinct — even though the folk explanation and the scientific one arrived at that agreement independently.
The dark band between the two bows is real too
Observers of a double rainbow often notice a visibly darker band of sky between the primary and secondary bows, known to physicists as Alexander's band, caused by the geometry of light rays being redirected away from that specific region by both reflection processes at once — a genuinely observable, physically explained detail that predates most people's awareness that it even has a name.
Rare instinct matching real physics
Folklore reading a double rainbow as doubled luck, and modern optics confirming the secondary bow is a genuinely distinct physical event rather than a weaker copy, arrived at the same basic verdict — this sight really is special — from two completely different directions.
What Different Cultures Say
In Chinese folk tradition, a double rainbow is read as an especially strong sign of good fortune, doubling the single rainbow's already positive associations rather than introducing a separate meaning of its own.
British and Irish folk tradition treats a double rainbow as a rarer, more remarkable version of the same pot-of-gold and general good-luck associations attached to a single rainbow, with the second bow simply intensifying rather than changing the underlying story.
Frequently Asked Questions
Is a triple rainbow possible, and does folklore say anything about it?+
A third-order bow is physically possible but extremely rare and very faint, typically requiring specialized observation to detect at all, and it doesn't have a comparable body of folk tradition attached to it the way the more commonly witnessed double rainbow does.
Why is the space between the two rainbows darker than the sky around them?+
That darker band, called Alexander's band, results from the specific geometry of both reflection processes redirecting light away from that particular region of sky, making it a real, physically explained feature rather than an optical illusion.
Does the color-reversal in the second bow happen every time, or only sometimes?+
It's a consistent, reliable feature of how the secondary bow forms — the reversed color order isn't a rare variant, it's the expected and defining characteristic of every secondary rainbow.
Is the doubled-luck reading found outside Chinese and British/Irish tradition?+
Similar intensified-fortune readings of a double rainbow appear informally across a number of folk traditions, consistent with the sight's rarity and visual drama prompting a similar intuitive response in more than one culture independently.