When I was researching Fogbows for Did You Know a Ghost Rainbow Isn’t Just for Ghosts? I made several surprising discoveries about rainbows. I didn’t have room to share all my findings in that DYK, so I decided to write another one.

 

Circular and Fogbow Rainbows

There isn’t just one kind of rainbow. That was my first surprising discovery. (Fogbows, aka Ghost Rainbows, are only one kind.)

Right behind that was the fact that all rainbows are supposed to be full circles, not semi-circles or arches. Though only from high above can you usually see a Full-Circle Rainbow. (It all has to do with your perspective.)

 

Multiple Rainbows

Sometimes, more than one rainbow is seen. If it’s a Double Rainbow, there are two separate rainbows parallel to each other. In these cases, the primary rainbow is bolder and more colorful. The secondary rainbow (above the primary) is fainter.

Twinned Rainbows are similar to Double Rainbows except they aren’t two separate rainbows. They share the same base and split apart as they go up the arch. Twinned Rainbows are rarely seen. They only appear when there are two rain showers with different sizes of raindrops. The light refracts differently on the different-sized drops, splitting the rainbow into two.

A Supernumerary Rainbow refers to the faint lines of color beneath a primary rainbow’s lower violet edge. It’s formed by interference between the different colors’ wavelengths. These wavelengths are very sensitive to raindrop size and can change as you watch.

Did You Know…

• The area between a Double Rainbows’ two rainbows is called “Alexander’s band.” Alexander of Aphrodisias, a second-century philosopher, was the first person to write about this phenomenon.
• Double Rainbows occur when sunlight bends twice inside the raindrops.
• The colors of the Double Rainbow’s secondary rainbow are in reverse order from the primary. Instead of red being on the top outside (ROYGBIV), the red is on the inside closest to the ground (VIBGYOR).
• Twinned Rainbows both have the same color pattern as a primary rainbow.
• The more deep red seen at the top of a primary rainbow is a sign of heavy rain. (“Lots of red, means a wet head.”) On the other hand, a Supernumerary Bow is the opposite. It has small raindrops, and the top of the primary rainbow is more orange than true red.
• A rainbow is made up of over one million colors, but humans can’t see or understand most of them.

 

Rainbow Photo

I took this photo on Sunday, May 8, 2005. It was Mother’s Day, and my cousin and I had stopped to call our mothers at a bright red telephone box out in the middle of nowhere.

While she was on the phone, I noticed this Double Rainbow across the street. (Can you see the secondary bow in the top right corner of the photo?) I know it’s a Double Rainbow because the secondary bow’s colors are reversed. (The red is on the bottom.) I also believe it’s a Supernumerary Rainbow because there appear to be colors under the violet of the primary bow.

 

Monochrome Rainbows

A Monochrome Rainbow (aka a Red Rainbow) has a single color, usually red. It’s seen only at sunrise or sunset, when sunlight travels the furthest distance through the atmosphere. Because of this longer distance, the shorter wavelengths (yellows, greens, and blues) are “ousted”, leaving only the red.

Did You Know…

• Red light bends the least, while violet light bends the most.

 

Moonbows

Moonbows are Lunar Rainbows. They’re created the same way as regular rainbows, only the light used is moonlight rather than sunlight. Because moonlight is so much dimmer, the Moonbow is often too weak for human eyes to detect color. Even if conditions (location, light, etc.) are perfect, the Moonbow’s colors won’t be anywhere near as vivid as a rainbow. More often than not, the Moonbow will appear as a white rainbow with very little color apparent.

Did You Know…

• Moonbows are also known as Night Rainbows.
• To detect a Moonbow, the moon needs to be almost full, nearing its brightest phase.
• A Moonbow only forms when there are no clouds and the moon is low in the sky, i.e., one or two hours after sunset.
• Moonbows can be seen regularly in only three places in the U.S.—Niagara Falls, NY; Yosemite Falls, CA; and Cumberland Falls, KY.

 

The End . . . The Beginning

Rainbows are special. We love seeing them shimmering in the sky after a rain. To most of us, it’s almost a magical moment. It’s a symbol of hope, new beginnings, and a promise from God to never again destroy all life on earth with a flood.

Truthfully, you don’t need to know the science behind how or why a rainbow is formed. All you need to do is enjoy it.

Did You Know…

• The sky beneath a rainbow is brighter than that above it.
• The word rainbow comes from the Latin word Arcus Pluvius which means rainy arch.