All of us have watched cartoons as students in high school, where the main character would jump in a pond of water in the middle of the desert, only to realize that it was a pile of sand.
This is what a desert mirage is; they are events of an illusion of water or water bodies in places with very high temperatures. A desert mirage is a naturally occurring optical phenomenon caused by refraction.
The word 'mirage' comes from the French word 'mirer'; is related to mirror, which comes from Latin 'mirari', meaning 'to wonder at'. It's commonly believed that this illusion of water is a classic case of hallucination. However, it's not. Hallucinations are when a person imagines something, and he only sees this figment of the imagination. An optical illusion is when something appears that it isn't there or is actually something else. This occurs because of the play of light, and we can capture it on camera. However, what the spectator deduces from this image depends on his mind. Apart from mirages, optical illusions can also be witnessed in cloud formations and water bodies.
Mirages can be classified as inferior mirages and superior mirages. Another type of desert mirage is known as 'Fata Morgana'. It's a kind of superior desert mirage comprising a series of unusually elaborate, vertically stacked images, which form one rapidly changing mirage.
Mirages have been one of those few phenomena that irk the mind of scientists and travelers alike. They are prime examples of refraction in real life and are used to explain to high school students about Snell's Law.
What is a mirage?
Imagine being in a desert, and you have been walking for hours in search of water. The scorching sun seems to burn your skin. You have been walking for miles without a drop of water in sight, and suddenly, you have an oasis or a pool of water. What a treat for your hot, burning eyes!
But as you are about to drink water from this pool, it turns out to be... sand! That's a good time for you to shout for help. It's not a puddle of water; it's a desert mirage.
Such desert mirages have been fooling wanderers for ages. Many people love such illusions, and what is best is that they find themselves open to imagination.
Normally, the light waves from the sun enter straight into your eyes through the atmosphere. However, as we know, the atmosphere is made up of air, and different layers of the atmosphere are at different temperatures. Light travels at different speeds at different temperatures. This makes the ray of light bend, a process otherwise known as refraction.
It might be interesting to know that mirages are not only formed in deserts but the mirage phenomenon is quite common in other locations. For example, have you ever noticed how on a hot May or September afternoon, if you are driving on a tar road, it looks as if there is water spilled at some distance ahead on the road? That is a case of a mirage as well.
Some other famous mirages, apart from desert mirages, are the Sundog, where you can see reflections of the sun on its opposite side, and The Broken Specter. Mountain climbers witness this mirage. They report that a ghostly human-like figure looks at them through the mountain haze. Spooky right?
Another place where you can experience mirages is on magnetic hills. On magnetic hills, if you leave your car with the ignition off, it appears to be pulled upwards instead of going down the way it naturally should. People initially assumed it was something to do with magnetism or gravity. However, that's actually not the case. The illusion has nothing to do with gravity or magnetism. Instead, it has to do with the landscapes surrounding the road. The explanation is pretty easy to provide. The surrounding hills are sloped so that it appears that the road level is up an incline. However, if you could put the surrounding visual cues out of the picture and walk on the same road, you would notice that the road ahead is sloping downward. Finding a magnetic hill is well worth it, you're sure to have the best time exploring this phenomenon! The illusion is called 'Ladakh' in India.
The Science Behind A Mirage
Grab your phone and call your friends to tell them the news about mirages. Desert mirages have absolutely nothing to do with water. It all comes down to how light travels high through the air. The sun's light rays normally pass right through the atmosphere and into your eye. On the other hand, light travels at different speeds in hot and cold air. Mirages occur when the ground is really scorching, and the air is cool, which is why a desert mirage is common. The heated ground warms a layer of air slightly above the ground. Light is refracted as it passes across a layer of cold air and into a layer of scorching air (bent). The light from the sky is refracted nearly into a U-shaped bend by a layer of very warm air near the ground. The light appears to have gone in a straight route to our brain. Our brain does not perceive the image as bent light from the high sky. Instead, our brain assumes that the light came from somewhere on the earth and tries to make images around it.
Desert mirages are mostly cases of inferior mirages. In this type of mirage, below the real object, a mirage appears. In an inferior desert mirage, the true object is the (blue) sky or any distant (therefore bluish) object in the same direction. The spectator sees a bright and blue area on the ground due to the desert mirage.
Light beams from a single distant object travel through almost identical layers of air and are refracted at about the same angle. As a result, rays arriving from the object's top will arrive lower than those coming high from the bottom. The picture is generally inverted to give the impression that the distant sky image is a marvelous reflection on a puddle of water or oil serving as a mirror.
Inferior images are not steady. The access air layers mix, generating turbulence because warmer air rises and colder air (due to its density) sinks. The picture will be altered as a result; it may jiggle or become distorted.
How are mirages formed?
Desert mirages are formed by nothing but the sheer fallacy of our brains with a little trick by the light. What is going on for a desert mirage to develop may be seen in the image above. The' bent light from the high sky' is refracted as it goes from colder to hotter air and back up to your eye. Our brains deceive us by supposing that refracted light travels in a straight line. As a result, we return to the light source, which appears to be the earth. When all of this is considered, the refracted skylight is regarded as straight, allowing us to see a picture of the sky on the ground.
This is why a lot of mirages first appear blue. Looking at the image, we thank our lucky stars and assume we've found a mirage desert oasis, but what we're seeing is a shimmering illusion of the blue sky. We imagine the picture of sparkling water because our brains don't identify the sky as being on the ground.
However, travelers today have gained far more experience with this optical illusion and thus don't get deterred by mirages. However, there are have been cases where such mirages have confused and even scared travelers out of their wits when they found stretches of water in the middle of the desert. These cases mostly used to happen in old times when people were under the influence of substance, as optical illusions are difficult to figure out with a completely agile mind; however, most cognitive abilities stop under the influence.
Types Of Mirages
Now that we have understood why mirages are formed. Next, look at what type of mirages you can find in nature. Typically, there are three types of mirages: inferior mirages, superior mirages, and heat haze. While we have already gone through the details of the former, the latter is much more stable and has multiple elements. The desert mirage image seems to be placed above the real object in a superior mirage. A superior desert mirage appears when the air below the line of sight is cooler than the air above it. Warm air over cold air creates a temperature inversion, which is the polar opposite of the regular temperature gradient in the atmosphere during the day.
The heat haze is a mirage that is witnessed on roads and is related to the same explanation as desert mirages.
Desert mirages can be fascinating any day.
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