Why does the road look wet in summer?

Ever wondered why a road looks wet while driving during Summer while actually, it is not. This can fool travelers into thinking that there is water nearby. What is the science behind this mirage?

This can be particularly dangerous for those who become stranded in the desert, as they keep going towards the mirage for water and shade.

• Where is the longest straight road in the world?

The Science of Refraction

Light moves at a slower rate through dense mediums and faster through less dense mediums. As the light travels from one medium to a certain density to another of a different density, the light is forced to change speed, which causes it to change direction. This is known as refraction.

Put a straw in half a glass of water. If you look at the straw from the top, it looks like the straw is bent or crooked. From the side, it looks like it is getting wider as it enters the water.

Why does the road look wet in summer?

Now coming back to the question why does the road look wet in summer. The light refracts not only through different mediums but also refracts when moving through layers of the same medium with different densities.

As the light from the sun travels down towards the hot roads, it moves through increasingly hot and less dense layers of air, which causes a change in speed and refracts as it moves through them. 

When the refracted light eventually reaches you, your eye and brain don’t account for the bending it did along the way from the sky. Essentially what you see is a part of the sky sitting on the road.

Even while your brain and eyes are trying to make sense of what you are viewing, the brain knows that the sky on the ground makes no sense; hence you perceive this as a mirage of water on the road.

So the reason we find the road looks wet like water in summer is the science of refraction.

Turbulence or change in wind patterns can cause this mirage to get distorted. Sand, which is found near almost all highways in Saudi Arabia, is a good conductor of heat and holds onto it for a long time. This causes the air around it to also heat up, which eventually causes these mirages of water that are a common occurrence in the desert.