Someone once rightly said, “Don’t believe everything you see.” Have you ever felt your eyes playing tricks on you? While travelling in your car, on a really hot day in the summer, did you suddenly think there’s water on the road? It is highly likely that you may have been tricked by an optical illusion. Let’s get to the basics first — what are optical illusions?
Optical illusions are images or pictures that we perceive differently than what they really are. You must have read in your science books that optical illusions occur when our eyes send information to our brains that tricks us into seeing or thinking something that does not match reality.
When you think that you see water on the road in front of you on an extremely hot day, the phenomenon is called a mirage. Just like a mirage, there are other very common and fascinating optical illusions found in nature. We often come across them in our everyday lives but do not understand why or how they occur. Let’s look at a few of these mind-boggling illusions found in nature.
Widely known for their saucer-like appearance, lenticular clouds are stationary clouds that usually form on the downwind side of a mountain range, provided that the temperature there is low enough. Under the right conditions, moisture in the air condenses to form these massive, striking clouds in the sky, which are often mistaken for Unidentified Flying Objects or a visual cover for UFOs. Lenticular clouds typically form where stable moist air flows over a mountain or a range of mountains. Lenticular clouds are also said to appear and disappear relatively quickly.
We already spoke about a mirage earlier. It is an illusion sometimes seen at sea, in the desert, or over a hot pavement that looks like a pool of water or a mirror in which distant objects can be seen.
A mirage is a phenomenon where you think you see water but there isn’t any. Mirages are most common in deserts. They typically occur when light passes through two layers of air with varying temperatures. The desert sun heats up the sand, which in turn heats the air just above it. The hot air bends light rays and reflects the sky. When you see this from a distance, the different air masses colliding with each other act like a mirror. The desert ahead of you might seem like a water-filled lake but it is actually a reflection of the sky above.
Sun dog, also known as mock sun or parhelion, is an atmospheric optical phenomenon appearing in the sky as luminous spots 22-degree on each side of the Sun and at the same elevation as the Sun. Typically, the edges closest to the Sun will appear reddish. The scientific name parhelion (plural: parhelia) is from the Greek parēlion, meaning “beside the sun.” It has been often said that this phenomenon is called Sun dog because the spots follow the sun like a dog follows its master. They are also referred to as phantom suns. Sun dogs are usually formed from hexagonal ice crystals in high and cold clouds or, during extremely cold weather, by ice crystals drifting in the air at low levels. These crystals then act like prisms, bending the light rays that pass through them. As the crystals sink through the air they become vertically aligned, refracting the sunlight in a horizontal manner so that Sun dogs are seen.
The Moon might appear to follow you because it is relatively distant compared to the objects around you on Earth. As you drive along, things much closer to you, like trees and houses, appear to move between you and the Moon. The short answer is that it is all down to how close the object is to your moving car. The trees, buildings and people are all relatively close to us, so as we pass by, the distance we observe them from changes continuously. The angle at which we observe them changes too. Due to the vast distance, the Moon doesn’t seem to move at all and appears to be following you. This means that the Moon appears in basically the same angular position with the same angular size thus creating the optical illusion.
Have you ever experienced an optical illusion in nature? Tell us all about it in the comments below.
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