How Strange Twinned Rainbows Form
A twinned primary rainbow produced through computer simulation. The rainbow is split because of the interaction of light with two types of water drops: some smaller, spherical ones, and some larger water drops that become nonspherical. The different shapes cause light to leave the water drops in two different directions, which causes the rainbow to split into two arcs, a study presented in August 2012 found. CREDIT: UCSD / Jacobs School of Engineering.
Double rainbows had their fifteen minutes of fame on the Internet. Now get ready for their even more mysterious cousins: twinned rainbows. New research has suggested an explanation for these exotic shows of color.
Rainbows are known to form when sunlight interacts with tiny water drops in the atmosphere. As sunlight gets both reflected and refracted within the drops, it gets separated into its basic color components. Still, all the secrets of the more complex behavior of rainbows have long remained a puzzle.
The most common rainbow has a single arc. The less common double rainbow, which consists of two separate, concentric arcs, has inspired Internet memes. Triple and quadruple rainbows have even been spotted. Even rarer, however, is the twinned rainbow, where two arcs split from a single base rainbow.