Do you know that classic cartoon scene, where a character who travels through the desert sees a tropical oasis with its lake and palm trees, and when it’s about to dive the whole landscape disappears? This is a mirage, and although they are not exactly like in fiction, they actually exist.

 

How does a mirage happen?

Many people believe that mirages are hallucinations caused by heat, but in reality they are a real optical phenomenon, caused by the deviation of light.

To understand this phenomenon we must first understand how our vision works. We can see because objects reflect or emit light and it is that light that comes to our eyes and is sent to the brain, which interprets the signs and shapes the objects. However, our brain understands that the rays of light propagate in a straight line, so when there is some deviation of light we can not see it bend, we only see the effects of this fold. These effects occur in several ways, for example when the sun’s rays traverse media with different densities, such as water to air, or through lenses.

In the case of mirages, the deviation of light happens because of the air temperature. Due to the intense heat, near the ground is formed a layer of warm air, which is less dense than the air from the above, cooler layer. As light rays propagate faster in hot air, a refraction occurs, which changes the direction of light and then reflects in the layers of air that are close to the ground. But our brain understands that light has traveled a rectilinear path and that we are actually seeing the ground, but in fact we are seeing the mirrored ground, that is, a mirage.

Types of mirage

Mirages do not necessarily happen in the desert. We can observe the mirages on roads, when it is so hot that we have the impression that the asphalt is wet. These are the so-called lower mirages, which take place in hot regions.

There are also the higher mirages, common in polar regions or very cold water. However, these types of mirages happen in reverse, that is, there is a layer of cooler air near the surface and, above it, a layer of warmer air. In this way, mirages are reproduced in the air.

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