What causes a circular rainbow?

Rainbows are a product of sunlight passing through small droplets of water suspended in the atmosphere (or even falling through it!). read more

All rainbows are circular or consist of part of a circle with the sun at the center (with the sun either in front or behind you. The rainbow when the sun is in front of you is caused by a cone of light being refracted by small water droplets that are acting like prisms. read more

In a double rainbow, the second bow is produced because droplets can have two reflections internally and get the same effect. The droplets have to be the right size to get two reflections to work. The next time you spot a rainbow, you will see it in a whole new light. For more information, check out How Rainbows Work. read more

A little searching turned up another shot of a circular rainbow from the air, though it's not quite all in the single picture. It shows good supernumerary arcs, though. read more