What associations do you experience when you hearthe word "mirage"? As a rule, you seem to be a tired traveler who wanders through the hot sand and the scorching Sun in search of water. For several hours he dies of thirst, but suddenly sees an oasis on the horizon. He runs to him, she is getting closer and closer. This continues until he jumps into the air, preparing to swim in fresh water, but lands on the sand again. You might think that the traveler is hallucinating, but mirages are the most natural optical illusion. In cartoons, a mirage is often drawn as a magnificent oasis that lies in the shadow of swinging palm trees, but most likely it looks like a normal pool of water.
How are mirages formed?
To begin with, mirages have norelationship to water. In fact, the whole point is how light passes through the air. Typically, light waves from the sun pass directly through the atmosphere to your eye. But light moves at different speeds through hot and cold air. Mirages happen when the earth is very hot and the air is cool. Hot earth heats a layer of air directly above the ground. When light passes through cold air and enters a layer of hot air, it is refracted (bent).
A layer of very warm air near the Earthrefracts light from the sky almost into a U-shaped bend. Our brain thinks that light is moving in a straight line. Our brain does not perceive the image as distorted light from the sky. Instead, our brain thinks that light should come from something on earth. You can see in the image above what happens in order for a mirage to appear. The “twisted light from the sky” is refracted when it passes from colder air to hotter air and back to your eye. Our brain plays a trick on us, assuming that the refracted light follows a direct path. Because of this, we follow the light back to the source, which is apparently the earth. Combining all this together, the refracted light from the sky is interpreted as direct, allowing us to see the image of the sky on earth.
That is why many mirages appear to be blue water. We think we stumbled upon an oasis when we actually see a flickering image of a blue sky. Since our brain does not recognize the sky as being on earth, we imagine that it is shining blue water.
Where can I see the Mirage?
No need to go to the desert tosee a mirage: they are very common on roads, airport runways and even on hot sand on the beach. Mirages can be found wherever the earth can absorb a lot of heat. The most spectacular mirages occur on the wide expanses of a flat Earth, since too many hills, dips or bumps will not allow the refracted light to reach your eyes.