The Bizarre Mirages That Once Scared the Bejesus Out of Sailors

 

In the case of a fata morgana mirage, light reflecting from a distant object such as a ship is bent downward as it passes through the colder, denser air near the surface of the ocean (or sometimes cold land, particularly ice). But your brain places the object where it would be if the light came to you in a straight path—higher than it actually is. This bending effect can even work with the curvature of the Earth if conditions are just right, which is why some fata morgana images can actually be refracted cities and ships from beyond the horizon.

Fata morgana's most famous offspring, though, is the legend of the Flying Dutchman, a ghost ship said to sail aimlessly around the high seas. The tale was first popularized in a story called "Vanderdecken's Message Home" from 1821, which told of a boat from Amsterdam that haunts the Cape of Good Hope, trying to hand off letters from its dead crew to the vessels of the living (uh, no thanks, the sailors would say, you can deliver your own damn mail). Warner connects this to fata morgana showing a ship from beyond the horizon: The mirage vessel could suddenly disappear with no explanation, and there you have your legend.

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http://www.wired.com/2015/01/fantastically-wrong-fata-morgana/