Sometimes called the autokinetic effect, autokinesis is a visual illusion where a light can appear to move when stared at in the dark. It occurs most often on dark nights in areas with few visual cues (such as other lights or other illuminated objects or landmarks). This can be dangerous for pilots flying at night, as they may well mistake this apparent motion for movements of their aircraft making corrections with dangerous consequences. Generally, however, it can be assumed that the existence of the autokinetic effect is the result of valuable pre-programmed mechanisms in our visual system that enable us to perceive our world.
Our continued interest in such phenomena, and the fascination they have for the viewer, reflect both the endless creativity and the appreciation for creativity that are to be found in human nature.
The phenomenon of autokinesis was first observed by Alexander von Humboldt, when he observed the apparent wandering of stars. Schweizer noticed that these apparent movements varied according to the observer, concluding that thesternschwanken were subjective. It was Aubert who coined the term "autokinesis" in 1887.
When a small, dim, and fixed light source remains within visual range for an extended period of time, this phenomenon can occur, making it appear as if the light source were moving. Air Force Research Laboratory scientists claim that, after fixating on a dim light for six to twelve seconds, the light may appear to move up to twenty degrees per second in one or more directions. This visual illusion can be of particular danger to pilots at night. In addition, it is possible that this illusion may account for some supposed UFO sightings in which witnesses may see an isolated light, such as a bright star or planet, that appears to move erratically.
Autokinetic phenomena occur when there is a lack of other visual references; stars and other lights in the sky are common sources of autokinesis. Although there is no universally accepted explanation, the most commonly investigated explanation for the apparent movement of a light involves eye movements. The effect of apparent motion is created by eye movements and the resulting signals these movements send out. With no visual references, the brain interprets these signals as movement. However, several researchers, including Richard Gregory, have shown that autokinesis occurs when no eye movements are recorded. Gregory has suggested that with lack of peripheral information correcting movements that prevent eye movements due to muscle fatigue are wrongly interpreted as movement of the light.
A stationary light stared at for six to 12 seconds in the dark will appear to move. This phenomenon can cause considerable confusion for pilots, who can mistake the apparent motion of the light for nonexistent movements of their own aircraft. Before pilots were made aware of the phenomenon, autokinesis was responsible for numerous aircraft disasters.
To prevent, or overcome this phenomenon, pilots are often advised to:
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