The forces of Nature have shifted continents, sculpted towering mountains and sprawling plains -- but her architectural prowess doesn't end there, at least as it meets the eye. Earlier this month, after heavy rainfall in East China, an entire 'ghost city' appeared to rise up from the flooded Xin'an River near Huanshan, complete with buildings and trees where none had stood before. Stunned locals marveled at the sight, many believing it to be a vortex to a lost civilization. Scientists say, however, that the truth behind this incredible apparition isn't mystical at all.
The 'ghost city' that appeared so clearly, yet briefly, over the Xin'an River, scientists believe, was the result of a mirage, not unlike the illusion of water that often appears on roadways during hot weather.
Wikipedia offers a brief description of what causes mirages to form:
Cold air is denser than warm air and has therefore a greater refractive index. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient. When light rays pass from hotter to colder, they bend toward the direction of the gradient. If the air near the ground is warmer than that higher up, the light ray bends in a concave, upward trajectory.
Once the ray reaches the viewer's eye, the visual cortex interprets it as if it traces back along a perfectly straight "line of sight". This line is however at a tangent to the path the ray takes at the point it reaches the eye. The result is that an "inferior image" of the sky above appears on the ground. The viewer may incorrectly interpret this sight as water which is reflecting the sky, which is, to the brain, a more reasonable and common occurrence.
In this recent case in China, heavy rains caused warmer mist to form over the cold river water, creating conditions which allowed for the light reflected off of nearby buildings to become bent, making them appear to be where they are not.
For residents, the explanation behind the appearance a 'ghost city' may do little to dampen the actual experience of seeing it. "It's really amazing, it looks like a scene in a movie, in a fairlyland," one mirage witness said to UK news channel ITN.
Nature, for all her talents, never ceases to amaze.