A moonbow – sometimes also called white rainbow or lunar rainbow – is as the name suggest a rainbow created by the light of the Moon. Just as a regular rainbow, a moonbow is created when light (in this case – moonlight) enters tiny droplets of water. Then it is refracted at the surface of the droplet, causing the dispersion and producing a spectrum of differently colored lights.
But why a white rainbow?
As the light of the Moon is much fainter than the light of the Sun, so is the white rainbow. Moon doesn’t emit its own light, but simply reflects the sunlight. As such, it’s not able to create a fully-colored rainbow, instead of producing a white one – at least that’s how it looks for a normal person. The human eye is too weak to catch the colors, but it is possible to see them. They appear in long exposure photographs, where they look exactly as regular rainbows.
Where can I see a Moon rainbow?
Although regular rainbows are pretty common, spotting a moonbow is much harder. It can naturally occur all around the world, it’s hard to pinpoint were the next will happen. If you want to see a white rainbow, there only two places in the world where you can be almost completely sure you’ll get a chance to do so: Cumberland Falls in Kentucky, the USA and Victoria Falls on the Zambia-Zimbabwe border. In both of those places, gigantic waterfalls are creating enough mist to create a rainbow during the day. And if you’ll manage to visit it on a bright, the full moon night, you’ll see a milky-white moonbow crossing the sky.