Submitted by Justin Woodworth, 7th grade, Cherokee Middle School

A. The waves are caused by light bending as it travels through different air layers created by the hot surface.

"When air comes into contact with a hot surface, the air absorbs some of that thermal energy, becomes warmer, and expands, " said Tim Shedd, a mechanical engineering professor at UW-Madison.

The expanding air triggers small currents, creating moving layers of warmer and cooler air. Light changes speed and bends as it crosses the boundaries between these layers, similar to what happens when it passes through a lens, Shedd says.

"When you look at objects in the distance through these moving layers of hotter and colder air, the light bouncing off those objects gets bent in different directions as it travels to your eye. This causes the objects to look wavy, " he said.

Though these effects are most commonly noticed on hot roads, roofs, or other dark surfaces that absorb a lot of heat, "you can see this effect any time hot air mixes with colder air, such as the exhaust of a car or the air above a candle flame, " adds Shedd.

-- Produced in cooperation with University Communications

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