Visitors to areas where the terrain is flat and uninterrupted have often returned with tales of seemingly-fantastic visions. Desert travelers see distant, shimmering lakes; sailors at sea see ships in the sky or objects that actually lie far beyond the horizon.
Contrary to popular belief, a mirage is not a hallucination but is a real optical phenomenon. The fact that it can be photographed proves that. In a desert mirage like the one seen here, the illusion is caused by a thin layer of hot air just above the ground. The difference in refractive index between the hot air and the denser, cooler air above it causes the boundary to act like a mirror; distant objects are reflected -- perhaps becoming inverted, displaced or distorted in the process. The sky itself is reflected, making objects appear detached, floating in mid-air or on water.
So there is no need to doubt the sanity of someone who says they have seen a mirage. Of course, if a person is delirious from dehydration, they may be convinced that what they are seeing really is water in the desert. But one characteristic of a mirage proves it's only an illusion -- one that those dying of thirst have discovered the hard way: as you move toward the mirage, it forever recedes from you.
Location: Highway 70 near Alamogordo, New Mexico
Date: October 10, 2007
Time: 2:29 p.m. MDT
Camera: Kodak Z650 Zoom Digital
Exposure: Automatic (cropped)