"You could fry an egg on the pavement!" We all know the difference between stepping barefoot onto pavement instead of grass. But many don't realize this temperature difference is the same reason we sometimes see elusive pools of water on the roadway. Many a dehydrated desert traveler has imagined things, but mirages are very real! Unlike early travelers, we may enjoy watching them appear and disappear. But what causes them?
Actually, light is distorted when it passes through different
densities. You may have seen rainbows in oily water—or found that water hides a
fish's true position. But that light is passing through more than just air. We
don't often realize that air, itself, can have different densities! Remember that
hot pavement? Its heat changes the density of the air just above it, and that change is
enough to create a mirage. With the change in density, the light that hits this hot air
bends upward toward the viewer. The light is really from the sky, but now it appears to
be on the road, looking like a refreshing pool of water.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Scott Cutler, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP
Public Radio at the University of Texas at El Paso.
The Mirage Observer. Particularly for the younger set.
Museum of Unnatural History.
[Note that the second illustration calls it reflection rather than the [correct]
refraction indicated in the text.]