Ramona Reed age 10, Homedale, Idaho,

What makes mirage puddles on the highway?

Any mirage is a trick of air and sunbeams. Light carries pictures of the surroundings to our eyes as it passes through the air. Light beams usually travel through the air in almost straight lines. This gives us a correct image of the view. Once in a while, these sunbeams are bent, or refracted. Then the image they carry is moved, broken up or shuffled around. We see a mirage.

It may be a wavy image of something which is actually still. The tree trunks behind a campfire may seem to bob and weave. Some mirages are images carried over a great distance. You may see the image of a ship which is far out of sight over the horizon. Some mirages show things that do not really exist at all, such as those puddles on the highway,

Are these tricky mirages carried through the air by the wind? No, or we would be baffled by them in stormy weather. They tend to show up in hot, calm weather. Wind and moving air cannot bend the sunbeams. They are refracted by the density or thickness of the air.

This refraction happens when the air is arranged in layers of different densities. Usually, the densest, heaviest air is packed closest to the ground. The density tapers off and the air becomes thinner and lighter towards the sky, This forms a sort of airy pyramid heavy at the bottom and getting gradually lighter towards the top,

A glass prism is also a sort of pyramid. Beams of light are refracted on its sloping sides„ Bending at different angles, the colored rays of light are forced to fan out and show a rainbow. The pyramid of dense and  thinning air also refracts the sunbeams. It forces them to carry their images at different angles. The picture of the scenery is shuffled up and juggled out of shape.

This kind of airy pyramid bends the light rays downward and carries us the mirage of the distant ship. Sometimes dense and light air streams up waving currents.  This happens around .a campfire. The warm air expands and becomes thin air rising through the dense air around it. Light and dense currents of air joggle the image and show a mirage of dancing tree trunks.

Sometimes we get an upside down pyramid. The sun heats the ground and the ground heats a thin layer of the air above it. The denser air is now on top. This pyramid acts to refract the light rays upward. It causes us to see the mirage puddles on the highway,

What we really see on the road is an image of the sky. It looks for all the world like a puddle of rain water. It shimmers and even caries a picture of an oncoming car,  only from a distance. Like all mirages it disappears as we approach it. Those twisted sunbeams cannot fool us at short range.