This phenomenon occurs when the ground, reaching extreme temperatures, heats a thin layer of air near the surface, while the upper air remains cooler. Light passing through these contrasting temperature layers—cold above and hot below—refracts, bending its path. Specifically, the layer of very hot air near the ground bends the sky’s light into a U-shaped arc. However, our brain assumes light travels in a straight line, as it typically does under normal conditions.

As a result, the mind does not perceive that the image is the result of distorted sky light, but instead misinterprets it as a tangible object on the ground: water, vegetation, or other optical illusions that appear to float in the distance.

Formation of Mirage due to Total Internal Reflection.