Take just one look at this photo and you might find yourself rubbing your eyes before looking again. The breathtaking scene was captured by photographer Melvin Nicholson during a hike around Rannoch Moor in the Scottish Highlands and later posted to his Instagram account.
The colorless, wraith-like rainbow you're seeing is not photoshopped; it's a real phenomenon sometimes called a "ghost rainbow," "white rainbow," or "fog bow." Like with rainbows, fog bows are caused by the refraction of sunlight through water droplets in the air, only with fog bows the droplets are tiny by comparison to raindrops.
Droplets in fog are so small (typically smaller than 0.0020 inches) that the colors are far weaker, often with nothing more than a red outer edge and bluish inner edge. Fog bows are so faint that they look like a hollowed out rainbow, the ghost of a once vibrant arc. Hanging over a snowy landscape, however, they appear hauntingly apt.
"As soon as I saw this wonderful isolated windswept tree, I knew that it had to be framed by the fog bow," wrote Nicholson, to his Flickr page. "Freshly fallen snow set the scene all around. It was just beyond magical and one of those days that you'll remember for a long time to come."
Fog bows are far rarer to witness than rainbows, but they're not entirely recherché either. They are often called by different names depending on the context. For instance, fog bows seen while looking down on clouds from an aircraft are referred to as "cloud bows." Meanwhile, when sailors encounter fog bows through eerie ocean mist, they're often called "sea dogs." Perhaps the most evocative version of all, a lunar fog bow, occurs when light from the moon refracts through a spectral evening haze.
If you like Nicholson's capture of the ghost rainbow, you're sure to have your breath taken away by the rest of his work as well. You can find more of his photography at www.melvinnicholson.co.uk.