Mirages: The Basics

Once I grasped the concept of atmospheric refraction, I was ready to jump into the world of mirages. While I, like many people, could identify a mirage and its seeming illusory effects, I was clueless about the genesis of the phenomenon. Even the word itself struck me as somewhat exotic, a bit difficult to interpret. Mirage derives from both the Latin word mirari, meaning “to admire with wonder,” and the French word se mirer, “to be reflected.” Well, the Marfa Mystery lights have certainly been admired with wonder by many, but those amazed by the lights see them not from reflection, as might be inferred by the name mirage, but through refraction. I searched long and hard to find a definitive source that would reveal just how refraction creates a mirage, and more importantly, to learn what refractive process—or group of processes—turn headlights into Mystery Lights. I found that source in Andrew T. Young, an astronomer and expert on atmospheric-optical physics at San Diego State University. His Web site is by far the best source I’ve found for explaining all things relating to atmospheric refraction, including complex mirages. Thanks to Young’s instruction and collaboration, I realized that a number of phenomena can be at the root of the mystery of the Marfa Lights, from simple refraction to a variety of mirages, to mirage-related phenomena I never before knew existed.

When I first saw the lights, I imagined the cause to be what I thought of as the classic mirage, or the “water on the highway” mirage with which almost everyone is familiar. Called an inferior mirage, because the object seen in the mirage lies below the actual object, this can cause a mysterious effect. With an inferior mirage, light passes through the juncture of cold air above warm air and bends upward. During the day, particularly in desert regions during the summer, these mirages are common as heat from the Sun creates a very hot layer of air near the surface of the Earth. This creates a density gradient in the lowest few feet, with density increasing upward. Rays of light from the sky near the horizon are bent slightly upward, so a viewer staring at a road ahead of him sees the sky instead of blacktop. As convectional heat rising off the pavement churns the air, the temperature gradient continuously changes and the angle that light bends changes constantly, giving the appearance of shimmering water.

But what about Marfa? Could an inferior mirage add mystery to headlights of a car racing across Mitchell Flat? Yes. Even in winter? Yes again. Consider a clear January day; the blacktop of Route 67 warms as it absorbs the energy of the sun. At sunset, the surrounding dry, desert air cools quickly, but the blacktop remains warm, as does a thin layer of air above it. A car descends from the road’s high point, and the viewer sees the distant headlights as the car approaches. Then the light from the car’s headlights passes through this refractive layer and the rays angle upward, maybe to a degree “above” the viewer’s eyes, making them “disappear,” or perhaps the warm pavement continues to cause a strong level of convection, making the lights shimmer as they rise and fall. A car might come from behind the first one, and the single light the visitor sees appears to break into two, then the second car completes the pass, and the viewer imagines the alien craft re-merging along its glowing, shimmering path to voyage from Mars.

But the inferior mirage represents just the tip of the iceberg. Young explained the superior mirage, which causes an object to appear above the actual object, and warm air overlies cold (an inversion layer), then bends light down. The actual mechanisms of the superior mirage can be far more complicated than simple downward refraction; Young explained a “duct” in which refracted light rays cross one another at intervals governed by the thermal gradient of the inversion, where a viewer will see either an erect or inverted form of the miraged object. This is where the geometry of the Earth’s surface, including topographical features as well as its curvature, comes into play, as objects over the horizon—or on the other side of Route 67’s high point relative to someone standing at the Marfa Lights observation point, can be seen in the sky. A more distorted iteration of the superior mirage, the fata morgana (Italian name for Morgan le Fay, who was an Arthurian fairy who could change her shape), where the light rays from an object continue to criss-cross each other within the duct, but in ever more contorted ways with distance, could explain the wildest of the Marfa Lights. With a fata morgana (a phenomenon that Australian researchers have attributed to their homeland’s version of the Marfa Lights, the Min Min Lights), distant lights can elongate, separate, rise, fall, and otherwise resemble alien craft.

Believers Remain

There are other types of refraction forms that I think could be possible culprits in tricking would-be and willing extraterrestrial abductees to drive to Marfa to see the lights, such as the mock mirage, where a viewer sees a mirage from above an inversion layer, or the refractive (but non-mirage) effect of looming; where headlights far beyond the horizon rise into the sky; or towering, another non-mirage phenomenon, where distant car headlights “stretch” into the sky.

But as I pressed the final pieces of the puzzle together—thanks to Young—I realized that doubters and skeptics of scientific logic, and believers in the fantastics, will forever vociferously proclaim their dissent. So with the atmospheric facts behind the lights of Marfa in mind, should prospective visitors make alternate vacation plans? Perhaps to Roswell, New Mexico, instead? Definitely not. I found this part of the country to be starkly beautiful; worth a visit for its immense vistas, stark desert, and endless solitude—not to mention the wily lights, visible throughout the year. The town even holds a Marfa Lights convention each year around Labor Day, and I’m sure that everyone who goes there has his or her own ideas about the lights as well as their own reasons for venturing to Marfa (even glitterati are enamored by the lights—during the filming of the movie Giant, James Dean would watch them at night through his telescope).

Although the scientific case against extra-terrestrial happenings in Marfa, Texas, is pretty strong, it would be a kick if there really were aliens out there, and they just happened to crash-land somewhere out in Mitchell Flat because they confused car headlights with what they thought were Earth-based navigational aids.


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—Weatherwise Contributing Editor ED DARACK is a freelance writer/photographer; visit his Web site at www.darack.com.

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