Magic Tricks

The hand is quicker than the eye. Magicians must use diversions and quick hands to perform magic tricks but nature doesnít have to resort to those to fool the eye. It uses natural phenomena to make you think you see something that isnít really there. We call them mirages.

Mirages are caused by the refraction or bending of light as it passes through differing densities of layers of the atmosphere. The density differences are caused by temperature differences and the sharper the difference between two layers, the greater the refraction it causes.

As a result of this distortion, objects appear in positions different from their actual position. Alternatively, non-existent objects, such as water bodies, appear. In some mirages, distant objects appear much closer than they really are or appear inverted, higher or lower.

Some mirages like it hot, like water mirages and inferior mirages. Water mirages are the most common mirages and practically everyone has seen one. A water mirage forms on a road or desert and occurs when the pavement or soil becomes very hot. This makes the air just above the surface hot too.

Air just a few yards above the surface is cooler and therefore denser. When this occurs, blue light (from sunlight) is refracted upward toward our eyes and we perceive it as coming from the surface. It looks like water, especially when the image shimmers from small shifts in how light refracts. Water mirages appear in the distance and disappear when we approach them. The mirage-appears to move with us, always at a distance.

Inferior mirages also like it hot. These upside-down illusions are created basically the same way as water mirages. An inferior mirage is one that makes an upside-down version of an object appear directly below it. In this case, light is reflected away from an object in all directions, but the hotter layer of air close to the surface bends that light upward toward the eye.

Your eye automatically follows the light path and the object appears lower to the ground than it really is. The light from the top of the object refracts the most, which makes it seem it is lowest to the ground so the object itself appears upside down.

At the other end of the illusionary spectrum, some mirages like it cold! These mirages are created under conditions opposite to those of water mirages and inferior mirages. Superior mirages are formed in cold weather when the surface is colder (and therefore denser) than the air above. In a superior mirage, a distant object appears taller and closer than it really is. Superior mirages sometimes appear upside down as well.

They are most common in polar regions, but occur anywhere temperatures get sufficiently cold. A group of Europeans exploring eastern Canada turned back because they saw huge mountains they thought were too high to traverse. They tried to go to the mountains to get a better look at them but never seemed to get any closer. Cold, hungry, and defeated, they returned to the coast, stymied by a mirage.

Fata Morgana is a special type of superior mirage that takes the shape of spectacular castles, buildings or cliffs rising above cold land or water. They can occur in cold weather from the subtropics to the poles and require air temperatures to rise with height, alternating warming quickly and slowly in layers, above a cold surface. They are most common in the polar regions. The name is Italian for "Fairy Morgan," for King Arthurís half-sister. The Italians believed she was a magician who could create magic castles out of thin air. In the fifteenth century, poets saw a castle-like mirage near the Strait of Messina (between Italy and Sicily). For want of any explanation, they called it Fata Morgana after the woman magician they through created it.

These mirages can have some odd consequences. For example, in 1818, Sir John Ross observed and names the Crocker Mountains in the Canadian Arctic and estimated they were 50 km (30 miles) from his position in Lancaster Sound. He reported they appeared to block the way to the Northwest Passage. Later expeditions proved the mountains didnít really exist at all. Sir John probably saw a Fata Morgana mirage. No wonder the early maps were so inaccurate!

Mirages are natural wonders that fool the eye and confuse the mind, if you donít recognize what is going on when you see one. Natureís magic tricks are wonders to behold but let the beholder beware. What you see is not necessarily what you get!

Written by Melody L. Higdon, 14 WS/DOPA