Several years ago a woman in NY was able to capture a photograph showing that there were four rainbows in the sky. This something many have referred to as a quadruple rainbow.
However, it actually being a quadruple rainbow is ‘debatable.’ While seeing four rainbows in the sky regardless is rare and is not something we ever manage to capture photos of, this lady was able to see this interesting event both in person and on camera. Now, back when these images first surfaced online, National Geographic wrote about them noted that while the idea of a quadruple rainbow was interesting, this specific instance did not show that at all.
NG mentioned that this phenomenon we see in the photograph is actually just technically two double rainbows but regardless, two double rainbows made four in the sky so calling it a quadruple is still fine, I would assume. All of this having been said, the photograph is still stunning nonetheless.
As you can see below, it was likely a truly marvelous sight to see and is something we have not in the years following seen much about. Things like this just don’t happen often and those who are able to capture them on camera are truly talented. While it would be or could be possible for us to see four natural rainbows in the sky at once, that’s not something I have ever experienced myself and I’m sure most of you are right there with me on that.
Dr. Christopher S. Baird From Science Questions with Surprising Answers on WTAMU.edu wrote as follows on the topic:
Yes, although very rare, it is possible for a human to see four natural rainbows at once in the sky. A rainbow occurs when white sunlight scatters off of raindrops in the air. Because of the dispersive properties of water, the different colors of light in the sunlight bend (refract) different amounts when entering and leaving the raindrop. As a result, the different colors leave the raindrop at different angles, making you see the different colors at different locations in the sky. Because this scattering is a geometric effect that depends on the direction of the original incoming sunlight, the rainbow forms as a circle (or part of a circle) that is centered on the point exactly opposite of the sun. The main rainbow (called the “primary rainbow”) involves sunlight entering the raindrop, reflecting once off the inner back surface of the raindrop, and then exiting the raindrop.
Additionally, light can bounce twice off the inner surface of the raindrop before exiting. The second reflection causes these light rays to exit at an angle that is very different from that of the light rays that only reflect once. Therefore, a secondary rainbow forms that has a larger radius than the primary rainbow. The secondary rainbow is created by the same sunlight and the same refraction process as the primary rainbow, so it is also centered on the point exactly opposite the sun. Because of the additional reflection, the colors in the secondary rainbow are reversed in order compared to the primary rainbow. Since some light is lost out of the raindrop with every reflection, the secondary rainbow is much fainter than the primary rainbow. In principle, the secondary rainbow is always present. However, the secondary rainbow is often so faint that humans can’t see it. When viewing conditions are right (i.e. it is an unusually sunny day and there are an unusually high number of raindrops in the air), the secondary rainbow can be seen quite distinctly.
As you may have guessed, light can bounce three times off the inner surface of the raindrop before exiting, creating a third-order rainbow; or bounce four times, creating a fourth-order rainbow; and so on. However, the third-order and higher-order rainbows are so faint that they are almost never seen by the naked eye. By using a camera and image enhancements techniques, the third-order rainbow can indeed be imaged. This task is difficult enough that successfully capturing and analyzing the third-order rainbow earned Michael Grossman, Elmar Schmidt, and Alexander Haussmann a publication in the academic journal, Applied Optics. Considering the near impossibility of seeing third- and fourth-order rainbows, how are people able to see four rainbows in the sky at once?
The answer is that some of the sunlight can be reflected before entering the raindrops. Recall that rainbow formation is a geometric scattering effect leading the rainbow to be centered on the point opposite the sun. What would happen if there were two suns at two different locations in the sky? Then sunlight would hit the raindrops at two different angles, and two primary rainbows would result, each centered on a different point. If viewing conditions are favorable enough that the secondary rainbows are visible, then there would be four rainbows: a primary rainbow and a secondary rainbow centered on the point opposite the one sun, as well as a primary rainbow and a secondary rainbow centered on the point opposite the other sun. On planets with rain and two suns, quadruple rainbows are common. However, we don’t have two suns, so why am I mentioning this? A large, flat, shiny surface can reflect enough sunlight that the situation acts like two suns. A calm lake does exactly this. The sunlight coming directly from the sun is at an angle that is different from that of the sunlight reflecting off the surface of a lake, and they therefore form different rainbow sets centered on different points. The rainbows formed from the sunlight coming off of the lake are called “reflection rainbows”. In summary, although it is very rare, it is possible for the naked human eye to see four natural rainbows at once in the sky,
— Amanda Curtis (@amanda_curtis) April 21, 2015
Makes a lot more sense now, doesn’t it? Now, the woman who was able to capture the photograph was merely in the right place at the right time and when she posted the photograph on Twitter the internet did what the internet does, it was shared over and over again with some questioning its validity and others saying just how magical it was.
For more on this topic check out the video below. I for one would love to see something like this even if two of the four rainbows were secondary ones. They still look great.