Saying that rainbows are beautiful natural phenomena is an understatement. No matter how many times we’ve seen them, they still never fail to amaze us every time they appear. Rainbows are something special, not just because of sentimental reasons. They are optical illusions similar to a mirage – when the light rays bend, they create an effect that we can see but cannot touch or approach.
What makes rainbows even more special is that everyone sees them differently. Actually, no two people see the exact same rainbow. Since it all depends on how the light rays are being bent and reflected back to the observer, you can see the rainbow but others cannot see it, or others see it more differently elsewhere.
We have seen the familiar arc rainbow, which doesn’t appear quite often. Rainbows are usually the result of a sun shower – a meteorological phenomenon where rains or showers occur as the sun peeks through the clouds. So, yes, the saying “there’s a rainbow after the rain” isn’t just a dramatic expression. And no, there isn’t obviously a pot of gold at the end of the rainbow.
Rainbows appear as long as there’s the combination of sufficient light and falling water, specifically water mists, droplets, or sprays. You can see rainbows from waterfalls, sea spray, or even sprinkles coming out of your garden hose (yes, you can create your own rainbow!).
Apart from the familiar single-band arc rainbow, rainbows also appear in other unique forms, which we can see only at least once in our lifetime. And all of them are gorgeous and truly breathtaking. Rainbows are another beautiful reminder that Mother Nature never ceases to surprise and amaze us all.
Consider yourself lucky if you have seen any of these rarer types of rainbows listed below.
The most common type of rainbow, a primary rainbow, is caused by sunlight reflecting off of raindrops in the air. The light is then refracted, or bent, as it passes through the raindrops. The primary rainbow appears in the sky when the sun is at an angle of 42 degrees above the horizon.
Meanwhile, a secondary rainbow is caused by sunlight reflecting off of raindrops in the air and then passing through those same raindrops a second time. The light is then refracted, or bent, as it passes through the raindrops a second time.
Multiple rainbows or double rainbows
Multiple rainbows are one of the rarest types of rainbows. They occur when two or more rainbows appear at the same place at the same time. In this unique phenomenon, there’s the primary rainbow and the secondary rainbow(s). The primary rainbow is usually bolder and more colorful than the other rainbows surrounding it, although they are still visible.
Multiple rainbows occur due to the double reflection of sunlight within raindrops and are between 130 degrees and 127 degrees wide.
Double rainbows (also called twin rainbows) are similar to multiple rainbows, except for one big difference. Multiple rainbows run parallel to each other but form on different, separate bases. On the other hand, double rainbows have the same base but are separated farther along the arch.
Interestingly, there’s an unlit space between multiple rainbows, which is commonly referred to as “Alexander’s band” or “Alexander’s dark band.” It is named after Alexander of Aphrodisias, who first witnessed this phenomenon in 200 A.D.
Full circle rainbows
Rainbows are technically circular, but we mostly see them in arches for a couple of reasons. One, obstructions in the landscape block our view of the full-circle rainbow. Two, the sun’s angle, in comparison to the horizon and the point from which we see the rainbow, makes it impossible for us to see the rainbow in a full circle. So, the rainbow appears in arches when viewed from the ground.
But if you’re riding an airplane or at a high altitude, there’s a chance that you’ll see the rainbow in a full circle instead of the familiar arch.
Usually, the rainbows we see have a band of what is known as the “ROYGBIV” color sequence – red, orange, yellow, green, blue, indigo, and violet. But there are rare instances that a rainbow appears in one color only instead of the full spectrum of colors. In most cases, monochrome rainbows are red.
Monochrome rainbows typically appear during sunrise or sunset, where the sun’s light rays have to travel the furthest distance through the atmosphere, and that distance is what makes these rainbows red. All other wavelengths of light are shorter, so they scatter, leaving only red behind.
Supernumerary rainbows are also a rare sight to behold. According to the National Aeronautics and Space Administration (NASA), supernumerary rainbows only form when falling water droplets are all almost identical in size (usually, one millimeter in width, or less). Then, the sunlight will not only reflect inside those water droplets, but interfere with them, creating a wave phenomenon similar to ripples on a pond when you throw a stone at it.
Supernumerary rainbows have another unusual feature: they display pastel colors instead of the ROYGBIV spectrum of a typical rainbow.
We usually think of rainbows as a result of reflection and deflection of sunlight on water droplets. But rainbows can also appear under the moonlight, but they happen only rarely.
Lunar rainbows (also called moon rainbows or moonbows) have pretty much the same appearance as rainbows formed under the sunlight. Since the moonlight is not as bright as the sunlight, the colors may not be visible to the naked eye. But when the rainbow makes a rare appearance in the star-studded sky, it makes the whole scenery look quite romantic.
If you love everything about the moon, we’re pretty sure you will be fascinated by more interesting moon facts.
Fogbows, also known as “ghost rainbows,” are also very rare to spot. All rainbows have two primary elements: light and water droplets. For a fogbow to form, the sunlight must be at a low angle to a fog or small cloud in the atmosphere, around 30 to 40 degrees high. This is why fogbows are most commonly seen during mornings and evenings, or from high altitudes that place the viewer above the fog, such as mountaintops or tops of seaside cliffs. It is also possible to catch a fogbow when you’re riding a plane hovering over fogs or clouds.
A solar rainbow is created when sunlight reflects off of raindrops in the air and then passes through those same raindrops a second time. The light is then refracted, or bent, as it passes through the raindrops a second time. Solar rainbows are very rare and only occur when there is a full sun and when the sun is at an angle of 50 degrees above the horizon.
Fire rainbows, also known as circumhorizontal arcs, are created when sunlight passes through high-level cirrus clouds that contain ice crystals. These ice crystals act like prisms and refract sunlight into all of the colors of the visible spectrum, creating a bright, multicolored arc in the sky. Fire rainbows are relatively rare and can only be seen in certain parts of the world during specific times of year.
Glacial rainbows are created when sunlight reflects off of tiny ice crystals that are suspended in glacial meltwater. Glacial rainbows typically appear very faint and often look like white arcs in the sky. They can sometimes be seen in areas with glaciers or during springtime melting periods.