For centuries, sailors on the high seas supposedly saw everything from ghost ships, sea monsters, mermaids, and even sirens: dangerous femmes fatales who lured sailors to their death.

Some of these tall tales can be explained by the physics of light, temperature, and the way our brains process vision. "Fata Morgana" is a rare and complex form of mirage seen on land and at sea.

Unlike the more familiar water-in-the-desert "inferior mirage," a "Fata Morgana" is a form of "superior mirage." It can make objects like ships and even cities appear to be floating in the air.

According to a recent wired.com article, the optical illusion is created when cold denser air at the surface bends light reflected from a distant object downward -- but our brains still see the object as if its reflected light came in a straight path.

So the object appears higher than it actually is, often floating in mid-air. The legend of the flying dutchmancould have begun when sailors witnessed a "Fata Morgana."