As the rays graze the boundary between the layers, they are bent, creating the illusion of a second moon attached to the first. Within a matter of minutes, the two separate and the lower 'moon' slips back into the ocean. The rare, naturally occurring phenomenon, dubbed the 'Etruscan Vase' by Jules Verne after its unusual shape, was captured on film in the US earlier this month. At its heart is an abnormally-warm layer of air just above the ocean, generated by the sun-warmed afternoon sea. On the day these pictures were taken, the water was a relatively balmy 39F (4C), while the air high above it was a rather more chilly 18F (-8C).When the full moon's rays hit the boundary between the hot and the cold, their path was warped, creating a mirage of a second moon in its wake. The effect, which is similar to the mirage of a puddle of water on a road surface on a baking hot day, was captured by amateur photographer John Stetson at Casco Bay in Maine earlier this month. (Daily Mail)
