Rainbows, whether you believed them to lead to a pot of gold or believed them to be the Earth’s ring similar to that of Saturn, are nevertheless more central to the numerous cultures of human civilization than even Twitter or Disney World. Contrary to popular perceptions, a rainbow is not a physical arc that can be touched or approached, but rather an optical illusion that will always elude the observer.
Rainbows, despite being commonly seen in cultural perception, are relatively rarer than believed. In England, even in a rainy place, there may be fewer than ten bright rainbows in a year. However, in locations that receive more rain, rainbows may be more common, since rainbows are merely caused by the reflection, refraction, and dispersion of light inside water droplets into the full spectrum of light in the sky, often set against the backdrop of darker storm clouds, which in turn highlights the rain droplets directing and scattering light and so shining bright inside the rainbow arc. Rainbows are always observed opposite the sun, no exceptions.
When sunlight enters a raindrop, or any clear object with mass, part of it is reflected while another part enters and is refracted. When the light hits the back of the droplet, some of it is reflected back and splits into the color spectrum, since white is the combination of all colors. In general, the range of angles for the light to be reflected back is from 0 degrees to 42 degrees relative to the ground, with 42 being the most intense. The reason for this magic range is that 42 degrees is the turning point at which the light hits the outermost ring of the droplets and is returned at less than 42 degrees. So rainbows are more commonly observed in the morning and early evening, when the sun is low. In short, because the sun’s luminescence is finite and sun rays aren’t all parallel, the light is refracted based on wavelength, which is determined by the angle at which the light reached the rain droplets. Violet in the center occurs at shorter wavelengths due to the light hitting the rain drops at a steeper angle, while red occurs on the outside at a longer wavelength due to the light hitting the water droplets at a much shallower angle.Aristotle was the first to try and determine exactly how rainbows appeared and what purpose they served, but it doesn’t appear he came up with all that.
Role In Religion And Mythology
Since the dawn of civilization, the rainbow has been central to folklore and pressed into symbolic service. The Norse knew rainbows as Bifrost, a bridge that connected Earth to Asgard, the home of the Norse gods, and could only be accessed by gods and warriors killed in battle. In Hinduism, Indra was the god of thunder who used the rainbow to shoot arrows of lightning. It is within Irish legend that a pot of gold can be found at the base of a rainbow, with that treasure being guarded by a Leprechaun. Iris was the personified goddess of the rainbow in Ancient Greece. Decked full-out in rainbow colors, she was the messenger of the gods to humankind. She even appeared in nine of the twenty-four books of Homer’s The Iliad. In Australian Aboriginal myth, the Rainbow Serpent is the creator of the world and everything on it. It was believed that during the dry season the Rainbow Serpent would retreat into a distant waterhole before finally returning for the rain.
The Navajo basically believed they themselves were created by a “pair of rainbows crossed like rafters at the zenith of a proto-world so small that the heads and feet of the rainbows almost touched the men’s heads”. Everyone supposedly knows of the rainbow that appeared after the “Great Flood” in Judeo-Christian history. Since the flood had covered the Earth, the rainbow became a symbol of God’s promise never to unleash a flood upon all of the Earth again. In Armenia it was a belt of Tir, originally a god Sun before becoming a god of knowledge.In Chinese folktale, Hsienpo and Yingt’ai are lovers who must wait for the rainbow to appear for them to be alone. Hsienpo is the red color in the rainbow while Yingt’ai is the blue. The Karens of Burma believed the rainbow was a dangerous demon who ate children. Amazonian cultures associated the rainbow with spirits that cause harm such as skin problems. Traditionally, one closed their mouth in the presence of a rainbow in pre-Incan empire.The Bulgarians thought that if one walked beneath a rainbow, they would change genders, and a man would think like a woman, and a woman would think like a man. This last point brings us to rainbows' usage as a cultural symbol.
Use as a Cultural Symbol
Since rainbows have been a significant part of cultures all around the world historically, they’re often regarded as a sign of hope or a new era. Rainbow flags have appeared everywhere from the German Peasant’s War in the 16th Century to the gay pride of the LGBTQIA social movements. In other words, rainbows represent unity and equality universally across all cultures.
Types of Rainbows
There are many, many, many types of rainbows that exist. Here is a quick list of each type.
- Rainbow: Colorful arc that appears when it rains but the sun is shining opposite the observer.Secondary bow: This bow usually appears outside the main bow, and is fainter after the light rays have escaped two whole reflections. In other words, the rainbow itself is being reflected in raindrops. The colors always appear in the opposite direction of a rainbow.
- Supernumeraries: Closely spaced additional greenish purple arcs found inside even the violet color of the primary rainbow. These are formed by rays having different path lengths within each droplet.
- Red Bow: Simply a rainbow seen at sunrise or sunset when light has to pass through the lower atmosphere, resulting in longer wavelengths of light.
- Rainbow Wheel: A rainbow combined with crepuscular (or in this case, anticrepuscular) rays that converge on a point on the horizon.
- Dew Bow: Fairly rare, these are created by dew drops on grass or in spider webs, and generally form a full halo. Dew bows are most commonly found in the autumn.
- Spray Bow: A rainbow formed by the spray of a wave, waterfall, or geyser, and often a smaller arc than a normal bow.
- Glass Bead Bows: These appear following the resurfacing of a road, and after that road dries. Because glass is more refractive, these bows are only half the size of rainbows.
- Twinned Bows: A rare phenomenon where two rainbows seem to cross during heavy rainfall. There is no clear explanation for these yet, but the best theory seems to be that when heavy raindrops are flattened some by air resistance, they elongate, possibly producing both bows.
- Cloud Bows: Also not very common, these bows are created without any actual rain, but instead small water droplets in the form of mist or damp air.
- Moon Bow: Only visible at night, of course, and fairly rare, these bows are much fainter than their daytime counterparts, and then has to be lower than 42 degrees in the sky or else the bow won’t show at all. However, visit a waterfall at night when the full moon is out and a "moon bow" will be visible there. The moon bow pictured above was taken of the skies over the U.S. state of Utah.