Mysterious Colorless Rainbow Spotted Over Midwest

We typically associate rainbows with rain, sunlight, and an array of colors. So, when a Missouri woman spotted a colorless arc in in the sky on a rain-free day, she wasn’t sure what to make of it.

Tammi Elbert was driving in Missouri on Monday when she noticed the ghostly arc. An amateur photographer, she was able to snap a picture of it, which has since gone viral.

“When I first saw it, I thought it was maybe an optical illusion,” Elbert told ABC News.

It turns out what she saw was a “fogbow,” a rainbow variant that appears not in the rain, but on foggy days.

As the Weather Channel explains, rainbows appear when raindrops reflect and then refract, or bend sunlight, which allows us to perceive a spectrum of colors. In foggy conditions, the air is filled with droplets of water that are much smaller than raindrops, too small to refract the light. Instead, these droplets diffract the light, making it spread in such a way that we cannot see the colors of the spectrum, only a whitish vapor.

The best way to see a fogbow is to walk with your back to the light on a foggy day.

While arguably plainer than a rainbow, fogbows can still make for great photography. Check out this picture taken in Australia in 2010: