photo #5714933

App user ‘amuell01’ spotted this colourful smile in the sky over Sulphur, Oklahoma, US. Resembling the last remnant of the Cheshire Cat from Alice’s Adventures in Wonderland, this optical effect is known as a circumzenithal arc. It is produced by the refraction of sunlight through hexagonal-plate-shaped ice crystals falling horizontally like autumn leaves. The arc appears high in the sky, way above the Sun, which here would have been down towards the horizon beyond the trees. The colours of a circumzenithal arc are purer than those of a rainbow.‘“All right,” said the Cat; and this time it vanished quite slowly, beginning with the end of the tail and ending with the grin, which remained some time after the rest of it had gone.“Well! I've often seen a cat without a grin,” thought Alice; “but a grin without a cat! It's the most curious thing I ever saw in all my life!”‘ From Alice’s Adventures in Wonderland (1865) by Lewis Carroll.