 This illusion gives the pilot the impression that a stationary object is moving in front of the airplane's path; it is caused by staring at a fixed single point of light (ground light or a star) in a totally dark and featureless background.The reason why this visual illusion occurs is because of very small movements of the eyes.In conditions with poor visual cues accompanied by a single source of light, these eye movements are interpreted by the brain as movement of the object being viewed.