A 360° fog bow, an optical phenomenon similar to a rainbow that occurs when a spectrum of light appears due to the Sun's rays shining through fog. Because of the very small size of water droplets that cause fog—smaller than 0.05 mm (0.0020 in)—fog bows have only very weak colors, with a red outer edge and bluish inner. In many cases when the droplets are very small, fog bows may appear white, in which case they are known as "white rainbows".Photo: Mila Zinkova