- moon illusion
- Also known as Moon-size illusion and horizon illusion. All three terms refer to the Moon's apparently increased size when it approaches the horizon, in comparison with its perceived size when it is in the zenith. The ratio of this apparent increase in size lies around 2, although larger ratios (referred to as 'super illusion') have also been documented. This *size illusion is not restricted to the Moon. As it is also known to occur in relation to the Sun and other heavenly bodies, the generic term for this type of *illusion is * celestial illusion. It has been suggested that the apparent increase in the size of celestial bodies approaching the horizon was known as far back as prehistoric times, and that it was registered in written form as early as the seventh century BC by the Assyrians. In his book Meteorology, the Greek philosopher Aristotle (384-322 BC) speaks of "the sun and stars which at their rising and setting appear larger than at the meridian." Since Aristotle, this phenomenon has been described and analysed by numerous authors. Until the 19th century, the * Sun illusion would seem to have attracted more interest than the Moon illusion. However, today the Moon illusion is generally considered the archetypal representative of the group of celestial illusions. Throughout history, perhaps a 100 different explanations for the mediation of celestial illusions have been put forward. Starting with Aristotle, they have long been attributed to atmospheric mechanisms (referred to as the optical or atmospheric refraction hypothesis). As a corollary, celestial illusions were for a long time designated as *physical illusions (i.e. illusions stemming from physical rather than physiological or psychological mechanisms). Another classical explanation, called the size contrast hypothesis, involves the relative proportions of distant objects (such as mountains or buildings) and celestial bodies perceived in their proximity. To this day, the mediation of the Moon illusion has not been fully explained. It has been suggested that size contrast may account for some 40% of the illusion, and that oculomotor commands, angle of regard, and body posture may attribute another 10%. An additional proportion of unknown size is attributed to conflicting spatial representations in different visual pathways (i.e. the * corollary discharge hypothesis). A competing theory suggests that the Moon's * magnification at the horizon may be largely due to * oculomotor macropsia, a macropsia illusion occurring when objects at a distance of 1 m or more are observed while the eyes remain in their resting focus (i.e. dark focus) position, meaning that they are focused at a distance of about 1 m. In short, it is still uncertain whether the Moon illusion should be regarded as a * physiological illusion, a * cognitive illusion, or possibly a combination of the two.ReferencesAristotle (1984). Meteorology.In:The complete works of Aristotle. The revised Oxford translation. Volume 1. Edited by Barnes, J. Princeton, NJ: Princeton University Press.McCready, D. (1985). On size, distance and visual angle perception. Perception & Psychophysics, 37, 323-334.Ross, H., Plug, C. (2002). The mystery of the moon illusion. Exploring size perception. Oxford: Oxford University Press.
Dictionary of Hallucinations. J.D. Blom. 2010.
Look at other dictionaries:
Moon illusion — The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. This optical illusion also occurs with the sun and star constellations. It has been known since ancient times, and … Wikipedia
moon illusion — noun The optical illusion whereby the moon looks larger when it is low in the sky than otherwise … Wiktionary
Moon rabbit — The image of a rabbit delineated on moon s surface Chinese name Traditional Chinese … Wikipedia
illusion — illusioned, adj. /i looh zheuhn/, n. 1. something that deceives by producing a false or misleading impression of reality. 2. the state or condition of being deceived; misapprehension. 3. an instance of being deceived. 4. Psychol. a perception, as … Universalium
Moon — This article is about Earth s Moon. For moons in general, see Natural satellite. For other uses, see Moon (disambiguation) … Wikipedia
Moon in fiction — This article is about the Moon as the subject of and inspiration for creative works. For the Moon in mythology and religion, see Moon (mythology). The moon on the coat of arms of Grabow, Germany. The Moon has been the subject of many works of art … Wikipedia
illusion — Formerly known as illusio, fallacia, and idolum. The term illusion comes from the Latin verb illudere, which means to mock, to delude, to tempt. It is unknown when and by whom the term was introduced, but it has been in use since ancient times … Dictionary of Hallucinations
Moon landing conspiracy theories — Astronauts Buzz Aldrin and Neil Armstrong in NASA s training mockup … Wikipedia
Moon Society — The Moon Society logo The Moon Society is a space advocacy organization, founded in 2000, and dedicated to promoting large scale human exploration, research, and settlement of the Moon. The objectives of the Society are: The creation of a… … Wikipedia
Moon rock — Olivine basalt collected by Apollo 15. Moon rock describes rock that formed on the Earth s moon. The term is also loosely applied to other lunar materials collected during the course of human exploration of the Moon. The rocks collect … Wikipedia