From The Guardian by Ian Sample
David Morris encounters rare optical illusion known as superior mirage while out on coastal stroll
There are only so many polite words that come to mind when one spots a ship apparently hovering above the ocean during a stroll along the English coastline.
David Morris, who captured the extraordinary sight on camera, declared himself “stunned” when he noticed a giant tanker floating above the water as he looked out to sea from a hamlet near Falmouth in Cornwall.
Because cold air is denser than warm air, it has a higher refractive index.
“Superior mirages occur because of the weather condition known as a temperature inversion, where cold air lies close to the sea with warmer air above it,” said David Braine, a BBC meteorologist.
Photographers around the world have captured striking images of ships, yachts and other vessels apparently hovering in mid-air thanks to superior mirages.
The latter effect is well known to sailors who can sometimes rely on refraction to spot ships that are geometrically beyond the horizon.
More familiar optical illusions are the “inferior mirages” that give rise to apparent oases in the desert and puddles on hot summer roads.
- The Guardian : Weatherwatch : castles in the air