Most of us will drop everything to go catch a glimpse of a rainbow. Not only are they beautiful, but they really don't happen too often. It takes a perfect mix of a recent rainfall, with the right amount of haze left in the sky, plus the quick appearance of strong sunshine to produce the best rainbow. And what's more, they don't stick around too long either.
But if a rainbow is worth a little party, then we've got something for you that deserves a full-on parade. It's called a fog bow, and it's pretty stunning stuff.
A great place for fog
The fog bow that you saw in the photo at the top of this post was taken by photographer Melvin Nicholson in Scotland at the Rannoch Moor. A moor is an area of uneven land that is not good for farming—it is halfway between a swamp and a grassland.
Rannoch Moor is found in the Scottish Highlands. This area is full of lakes, rivers, and rolling hills, making it the perfect spot for lots and lots of fog. And that's where this fog bow comes in. A fog bow, also called a white rainbow, is similar to a traditional rainbow. The big difference is the super tiny size of the water droplets involved. Why does that matter?
Smaller drops, less colours
What we see as white light is actually filled with many colours. Normally, these colours all stick together. But sometimes, the light moves through an object that causes some colours (which naturally move a little slower than the others) to get split apart. Take a look at this image of light moving through a prism (a triangular piece of glass).
As the single beam of white light moves through the prism, the different colours each travel at a slightly different speed. They then emerge on the other side split as a bow of colours. This is what happens in a rainbow. Except instead of travelling through a prism of glass, the light is moving through millions of drops of rain.
Okay, that makes sense. But why then is the fog bow white? Because the drops of water in fog are so small, the white light is barely broken up. So what you see looks similar to a rainbow, only without the really vivid colours. And far more rare, too.
Definitely well worth rushing outside to catch a look at!