One of the most suggestive shows that nature, especially in certain latitudes, is able to offer, is the white rainbow. This is a very rare phenomenon and occurs only under certain conditions. It is the size of the drops that determines this spectacular event. In essence, the small particles of liquid have a smaller size than the “classic” ones that make up the normal rainbow and, therefore, are not able to break the sun’s rays, as normally happens. It is a phenomenon well known in the world of sailors among whom it is known by the name of arch of fog or marine dog.
In some cases, the white rainbow also occurs thanks to the moonlight. The latter phenomenon is very rare and above all very weak, due to the lower strength of satellite light. Precisely because of the lower brightness, it is difficult for the observer to distinguish the various colors; a factor showing the completely white lunar arc. The phenomenon is very recurrent in the vicinity of waterfalls and jets of water, in which the sprays release large quantities of suspended water droplets, dispersing the moonlight.