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'''Invisibility''' is the [[state]] of an object which cannot be [[vision|seen]]. An object in this state is said to be Invisible ([[literally]], "not visible"). The term is usually used as a fantasy/[[science fiction]] term, where objects are literally made unseeable by [[magical]] or [[technological]] means; however, its [[effects]] can also be seen in the real world, particularly in [[physics]] and perceptional [[psychology]].
Since objects can be seen by [[light]] in the visible [[spectrum]] from a source [[reflecting]] off their [[surfaces]] and hitting the viewer's eye, the most natural form of invisibility (whether real or [[fiction]]al) is an object which neither reflects nor absorbs light (that is, it allows light to pass through it). In [[nature]], this is known as [[transparency]], and is seen in many naturally occurring [[materials]] (although no naturally occurring material is 100% transparent).
Visibility also depends on the eyes of the [[observer]] and/or the instruments used. Thus an object can be classified as "invisible to" a [[person]], [[animal]], instrument, etc. In the [[research]] of sensorial [[perception]] invisibility has been shown to happen in [[cycles]].[1]
Invisibility is often considered the supreme form of [[camouflage]], as it doesn't show any kind of vital, visual, nor any of the frequencies of the electromagnetic spectrum such as radio, infrared, ultra violet, etc.
==In mythology==
People have attributed invisibility to [[things]] that are [[mythical]], things that do not exist and are of a [[religious]] or [[supernatural]] in order to explain why they are not apparent. In the [http://en.wikipedia.org/wiki/Middle_Ages Middle Ages], fern seeds were [[thought]] to be invisible since ferns don't have seeds. They were also said to grant invisibility.[1] In [http://en.wikipedia.org/wiki/History_of_astronomy#Medieval_Western_Europe medieval astronomy], the [[crystal]] [[spheres]][2] that held up the sun, moon, stars, and planets were invisible. Historically, [[creatures]] such as [http://en.wikipedia.org/wiki/Goblins goblins] and [http://en.wikipedia.org/wiki/Brownie_(elf) brownies] have also been described as invisible or able to become invisible. Currently, many [[entities]] or [[phenomena]] whose [[existence]] is disputed, such as [[ghosts]], demons, qi, and [[auras]], are also ascribed invisibility. In [[religion]], gods, goddesses, [[angels]] and demons are commonly thought to be invisible, at least part of the [[time]]. Indeed, the [[omnipresence]] attributed to the [[monotheistic]] God of Abrahamic religions would seem to require invisibility, since otherwise God would be constantly visible to all people because of inhabiting all places, however it has been theorised that a [[being]] such as God would exist in [[dimensions]] not [[Perception|perceptible]] to 3-dimensional beings. For example, a 2-dimensional being would only be able to see things in 2 dimensions, length and bredth. Anything outside of these two dimensions, i.e. height, is "invisible" to them. Additionally, [http://en.wikipedia.org/wiki/Hades Hades], the [[Greek]] god of the underworld, possessed a helmet that made the wearer invisible.
==References==
# Eugene A. Craig and M. Lichtenstein, "Visibility-Invisibility Cycles as a Function of Stimulus-Orientation," The American Journal of Psychology, 66.4 (Oct., 1953):554-563.
# Cloak of invisibility: Fact or fiction? - Innovation - MSNBC.com
[[Category: General Reference]]
'''Invisibility''' is the [[state]] of an object which cannot be [[vision|seen]]. An object in this state is said to be Invisible ([[literally]], "not visible"). The term is usually used as a fantasy/[[science fiction]] term, where objects are literally made unseeable by [[magical]] or [[technological]] means; however, its [[effects]] can also be seen in the real world, particularly in [[physics]] and perceptional [[psychology]].
Since objects can be seen by [[light]] in the visible [[spectrum]] from a source [[reflecting]] off their [[surfaces]] and hitting the viewer's eye, the most natural form of invisibility (whether real or [[fiction]]al) is an object which neither reflects nor absorbs light (that is, it allows light to pass through it). In [[nature]], this is known as [[transparency]], and is seen in many naturally occurring [[materials]] (although no naturally occurring material is 100% transparent).
Visibility also depends on the eyes of the [[observer]] and/or the instruments used. Thus an object can be classified as "invisible to" a [[person]], [[animal]], instrument, etc. In the [[research]] of sensorial [[perception]] invisibility has been shown to happen in [[cycles]].[1]
Invisibility is often considered the supreme form of [[camouflage]], as it doesn't show any kind of vital, visual, nor any of the frequencies of the electromagnetic spectrum such as radio, infrared, ultra violet, etc.
==In mythology==
People have attributed invisibility to [[things]] that are [[mythical]], things that do not exist and are of a [[religious]] or [[supernatural]] in order to explain why they are not apparent. In the [http://en.wikipedia.org/wiki/Middle_Ages Middle Ages], fern seeds were [[thought]] to be invisible since ferns don't have seeds. They were also said to grant invisibility.[1] In [http://en.wikipedia.org/wiki/History_of_astronomy#Medieval_Western_Europe medieval astronomy], the [[crystal]] [[spheres]][2] that held up the sun, moon, stars, and planets were invisible. Historically, [[creatures]] such as [http://en.wikipedia.org/wiki/Goblins goblins] and [http://en.wikipedia.org/wiki/Brownie_(elf) brownies] have also been described as invisible or able to become invisible. Currently, many [[entities]] or [[phenomena]] whose [[existence]] is disputed, such as [[ghosts]], demons, qi, and [[auras]], are also ascribed invisibility. In [[religion]], gods, goddesses, [[angels]] and demons are commonly thought to be invisible, at least part of the [[time]]. Indeed, the [[omnipresence]] attributed to the [[monotheistic]] God of Abrahamic religions would seem to require invisibility, since otherwise God would be constantly visible to all people because of inhabiting all places, however it has been theorised that a [[being]] such as God would exist in [[dimensions]] not [[Perception|perceptible]] to 3-dimensional beings. For example, a 2-dimensional being would only be able to see things in 2 dimensions, length and bredth. Anything outside of these two dimensions, i.e. height, is "invisible" to them. Additionally, [http://en.wikipedia.org/wiki/Hades Hades], the [[Greek]] god of the underworld, possessed a helmet that made the wearer invisible.
==References==
# Eugene A. Craig and M. Lichtenstein, "Visibility-Invisibility Cycles as a Function of Stimulus-Orientation," The American Journal of Psychology, 66.4 (Oct., 1953):554-563.
# Cloak of invisibility: Fact or fiction? - Innovation - MSNBC.com
[[Category: General Reference]]
