Tuesday, September 04, 2012



You're walking in the desert or driving down the road on a sunny day, and you see a puddle of water coming up. You look again and it's gone! What happened? Oops.. Its a Mirage.

Deserts breed strange visions. Mystics have seen gods, angels, and devils in whirlwinds of sand and flickers of heat lightning. Soldiers have seen great fortresses, carved by giants from civ
ilizations past, in weathered sandstone cliffs. Conquerors have seen cities of gold beckoning from the edges of salt pans and the summits of sand dunes. They are all Mirages.

The Mirages are real phenomena of atmospheric optics, caused by strong ray-bending in layers with steep thermal gradients. Because mirages are real physical phenomena, they can be photographed.

In a Mirage, there is at least one inverted image of some object. This “mirror image” is the origin of the French word Mirage. They are categorized as Inferior, Superior and Fata Morgana.

It is most common in Deserts where the Sun has warmed the sand, and this warm sand has heated up the layer of air immediately above it. Colder layers of air will lie above this hot thin layer. The change in the speed of light as it passes across the boundary between the air layers of different density causes the light to bend.

The army of Napoleon encountered mirages in Egypt in 1798.
Confronted with upside-down landscapes, blades of grass that turned into palm trees and lakes that disappeared, Napoleon's troops are said to have fallen on their knees and prayed to be saved from the impending end of the world.

The photograph below is an example for Mirages where a lake is seen at a distance which is the result of refraction of light.

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