An example of how an object could appear to be invisible through the use of mirrors

Invisibility is the state of an object which cannot be 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. Image File history File links Download high resolution version (704x617, 61 KB) Summary GNU image from german wikipedia [1] about invisibility Licensing File links The following pages link to this file: Invisibility ... Image File history File links Download high resolution version (704x617, 61 KB) Summary GNU image from german wikipedia [1] about invisibility Licensing File links The following pages link to this file: Invisibility ... This article or section does not cite its references or sources. ... haha For other meanings see Fantasy (disambiguation) Fantasy is a genre of art that uses magic and other supernatural forms as a primary element of plot, theme, or setting. ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... Magic/magick and sorcery are the influencing of events, objects, people and physical phenomena by mystical or paranormal means. ... By the mid 20th century humans had achieved a level of technological mastery sufficient to leave the surface of the planet for the first time and explore space. ... The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density. ...

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 fictional) is an object which does not reflect 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). The visible spectrum is the portion of the optical spectrum (light or electromagnetic spectrum) that is visible to the human eye. ... Closeup of a blue-green human eye. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

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. Closeup of a blue-green human eye. ...

Invisibility by environment

An object may be classified as "invisible" if it cannot be seen due to environmental factors other than the fact that it doesn't reflect light. An object that might normally be seeable may be classified as invisible if it is: Devils Punchbowl Waterfall, New Zealand. ...

• Behind an object.
• The same colour or pattern as the background. (Camouflage)
• Patterned so that its outline is hard to determine.
• In an environment which is too dark or too bright.
• Not in a particular observer's line-of-sight. (Especially when driving)
• Transparent. (air and many other gases)

Anolis caroliensis showing blending camouflage and counter-shading. ... Driving is the controlled operation of a vehicle, which is usually a motor vehicle such as a truck, bus, or car. ... AIR is a three-letter abbreviation with multiple meanings, as described below: The Annals of Improbable Research, a monthly magazine devoted to scientific humour All India Radio - Indias Government Radio service AIR, a popular electronica band from France. ... A gas is one of the five main phases of matter (after solid and liquid, and followed by plasma and Bose-Einstein Condensate) and, that subsequently appear as a solid material is subjected to increasingly higher temperatures. ...

Invisibility in physics

Theoretical and practical physics offer several causes of invisibility. An object may be invisible if it is: The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density. ...

• So massive that its escape velocity exceeds the speed of light (e.g. a black hole)
• Emitting or reflecting light outside the wavelength range of visible light. (Radiation is generally invisible by this means.) Unfortunately, this would result in any obscured human being becoming not invisible and transparent, but completely opaque and resembling a human-shaped black hole.
• So tiny that it cannot be detected by an observer.
• A recent breakthrough (2006) at Imperial College London has shown that invisibility is possible by using specifically patterened crystals made up of nanoscale boxes that hold electrons. When light hits these crystals, it becomes entangled within the boxes, causing the object to become transparent.^[1]

Unsolved problems in physics: What causes anything to have mass? Mass is a property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... Space Shuttle Atlantis launches on mission STS-71 In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. In metric units, c is exactly 299,792,458 metres per second (1,079,252,848. ... A black hole is an object predicted by general relativity[1] with a gravitational field so strong that nothing can escape it — even the light. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength [citation needed]. The elementary particle that defines light is the photon. ... The wavelength is the distance between repeating units of a wave pattern. ... The visible spectrum is the portion of the optical spectrum (light or electromagnetic spectrum) that is visible to the human eye. ... Radiation in Physics is the process of emitting energy in the form of waves or particles. ...

Invisibility by technology

Technology can be used theoretically or practically to render real-world objects invisible:

• On Thursday October 19, 2006 a team effort of researchers from Britain and the U.S announced the development of a cloak of invisibility though it is only the first stages.[1]
• Making use of real-time image displayed on a wearable display, scientists are able to create a see-through effect, if not invisibility. This is known as optical camouflage and has been used in many science fiction works.
• Invisibility (lower visibility) for radar is called stealth technology.
• In some science fiction stories, a hypothetical "cloaking device" is used to make objects invisible.
• In filmmaking, people, objects, or backgrounds can be made to look invisible on camera through a process known as chroma keying.
• Theoretically, it is possible to make an object invisible, if the object has the same refractive index as the surrounding medium. (e.g. air)
• Although it has been shown that making opaque objects perfectly invisible ("non-scattering scatterers") is impossible,^[2][3] 2006 theoretical work predicts that the imperfections need not be serious, and metamaterials may make real-life "cloaking devices" practical.^[4][5] The technique is suspected to be applied to radio waves within five years, and eventually visible light is a possibility. The theory that light waves can be acted upon the same way as radio waves is now a popular idea among scientists and can be compared to a stone in a river, in where the water passes around it, but leaving no trace of a stone being in the water slightly down-stream. Comparing light waves to the water and whatever object that is being "cloaked" as the stone and the desire is to have light waves pass around that object, leaving no visible aspects of it, possibly not even a shadow.^[6]

A cloak of invisibility is a theme that has occured in fiction, and more recently, reality. ... Optical camouflage is a kind of active camouflage in which one wears a fabric which has an image of the scene directly behind the wearer projected onto it, so that the wearer appears invisible. ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... This long range RADAR antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. RADAR is a system that uses radio waves to detect, determine the direction and distance and/or speed... F-117 Stealth Fighter Stealth technology covers a range of techniques used with aircraft, ships and missiles, in order to make them less visible (ideally invisible) to radar and other detection methods. ... A Klingon Bird of Prey from Star Trek VI: The Undiscovered Country fires while using a cloaking device but is eventually destroyed by the USS Enterprise. ... It has been suggested that film production be merged into this article or section. ... This page is a candidate for speedy deletion, because: it is patent nonsense. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... Free space is the most simple and elementary electromagnetic medium. ... AIR is a three-letter abbreviation with multiple meanings, as described below: The Annals of Improbable Research, a monthly magazine devoted to scientific humour All India Radio - Indias Government Radio service AIR, a popular electronica band from France. ... In electromagnetism (covering areas like optics and photonics), a meta material (or metamaterial) is an object that gains its (electromagnetic) material properties from its structure rather than inheriting them directly from the materials it is composed of. ... Rough plot of Earths atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves. ...

Invisibility by magic

Invisibility, usually by magic, is a popular theme in fantasy, mythology and Ceremonial magic. It is often used as a gameplay device in role-playing and strategy games. Typically, people or objects can be rendered completely invisible by several means: Magic/magick and sorcery are the influencing of events, objects, people and physical phenomena by mystical or paranormal means. ... In literature, a theme is a broads idea in a story, or a message conveyed by a work. ... haha For other meanings see Fantasy (disambiguation) Fantasy is a genre of art that uses magic and other supernatural forms as a primary element of plot, theme, or setting. ... // The word mythology (Greek: μυθολογία, from μυθος mythos, a story or legend, and λογος logos, an account or speech) literally means the (oral) retelling of myths – stories that a particular culture believes to be true and that use supernatural events or characters to explain the nature of the universe and humanity. ... To meet Wikipedias quality standards, this article may require cleanup. ... Gameplay includes all player experiences during the interaction with game systems, especially formal games. ... A role-playing game (RPG, often roleplaying game) is a type of game in which the participants assume the roles of characters and collaboratively create stories. ... It has been suggested that Game of strategy be merged into this article or section. ...

• Magical objects such as rings, cloaks and amulets can be worn to grant the wearer permanent invisibility.
• Magical potions can be consumed to grant temporary invisibility.
• Magic spells can be cast on people or objects, usually giving temporary invisibility.
• Some mystical creatures can make themselves invisible at will, such as Chinese dragons in some tales, which can shrink so small that humans cannot see.
• An invisibility ritual is described in the manuscripts of the Hermetic Order of the Golden Dawn and appears on the Book The Golden Dawn by Israel Regardie.

Where magical invisibility is concerned, the issue may arise of whether the clothing and items carried by the invisible wearer/carrier are also rendered invisible. In general, they are, but in some instances, clothing remains visible and must be removed for the full invisibility effect. A finger ring is a metal band worn as an ornament around a finger; it is the most common current meaning of the word ring. ... A cloak is a type of loose garment that is worn over indoor clothing and serves the same purpose as an overcoat – it protects the wearer from the cold, rain or wind for example, or it may form part of a fashionable outfit or uniform. ... An amulet from the Black Pullet grimoire An amulet (from Latin amuletum, meaning A means of protection) or a talisman (from Arabic tilasm, ultimately from Greek telesma or from the Greek word talein wich means to initiate into the mysteries. ... A potion (from Latin potio, potionis, meaning beverage, potion, poison) is a drinkable medicine or poison. ... A legendary creature is a mythical or fantastic creature (often known as fabulous creatures in historical literature). ... Chinese dragons The Chinese dragon or Lóng in Mandarin Chinese (Traditional Chinese: 龍; Simplified Chinese: 龙; pinyin: Lóng; Cantonese Yale: Lùhng; Japanese: ryū or tatsu 竜; Korean: ryong 룡; Thai: mungkorn มังกรจีน; Vietnamese: rồng) is a mythical Chinese creature that also appears in other East Asian cultures, and is also sometimes... Samuel Liddell MacGregor Mathers, in Egyptian costume, performs a ritual of Isis (not a Rite of the Golden Dawn). ... Israel Regardie (Francis Israel Regudy) was born on November 17, 1907 in London, England to poor Jewish immigrant parents. ... Magic/magick and sorcery are the influencing of events, objects, people and physical phenomena by mystical or paranormal means. ... It has been suggested that folding clothes be merged into this article or section. ...

Simultaneous invisibility and color

Since something that is invisible has no color associated with it, it is somewhat paradoxical to imagine an object that is both invisible and coloured. This idea is most famous in the parody goddess, the Invisible Pink Unicorn. Color is an important part of the visual arts. ... Robert Boyles self-flowing flask fills itself in this diagram, but perpetual motion machines cannot exist. ... In contemporary usage, a parody is a work that imitates another work in order to ridicule, ironically comment on, or poke affectionate fun at the work itself, the subject of the work, the author or fictional voice of the parody, or another subject. ... Ceres, the Roman goddess of agriculture. ... A popular depiction of the Invisible Pink Unicorn, in the style of a heraldic animal rampant, though the nearest heraldic color to pink is purpure (purple). ...

Sight while invisible

According to the laws of physics as presently understood, an invisible person would necessarily be blind, no matter how their invisibility were achieved. In order to see light, it must be absorbed by the retina, but in order for a person to be invisible, the body must not absorb any light. In fact, according to the no cloning theorem of quantum mechanics, they could not even make a copy of the photons so they could see one copy and allow the other copy to pass through or around them. Human eye cross-sectional view. ... The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state. ...

This physical barrier appears to offset the advantage of any perfect invisibility method, unless one's intent was simply to hide and be still, letting the danger pass. On the other hand, a practical invisibility method need not allow light of all frequencies to pass all the time, so there may be ways around this limitation.

Alternatively, many works of fiction portray invisibility as a magic achievement, and since paranormal magic may be interpreted as breaking the laws of physics, it could theoretically allow sight. Invisibility is often utilized in science fiction and fantasy works which people go into with a healthy suspension of disbelief, anyway. Magic/magick and sorcery are the influencing of events, objects, people and physical phenomena by mystical or paranormal means. ... Suspension of disbelief refers to the willingness of a reader or viewer to accept the premises of a work of fiction, even if they are fantastic or impossible. ...

One of the few fictional examples of a double-blind cloak comes from the Thrawn Trilogy of Star Wars novels. Grand Admiral Thrawn's cloaking devices make the ships wielding them invisible, but also prevent those inside the ship from seeing out. Thus, most of the time, ships using this type of cloak remain stationary, dropping the cloak just before battle. (See the beginning of Specter of the Past for an example of this tactic.) Additionally, in the Halo series, the active camouflage power-up renders the wearer only partially invisible — the visible silhouette of the wearer is probably there so that the wearer's retinas can absorb what little light they need to see (though it probably also exists for game balance issues). The Thrawn trilogy (also known as The Three Book Cycle and The Heir To The Empire Trilogy) are the three novels, Heir to the Empire, Dark Force Rising and The Last Command, written by Timothy Zahn and set in the Star Wars galaxy about five years after Return of the... Grand Admiral Thrawn is a fictional character from the Star Wars galaxy. ... The Hand of Thrawn Duology is a pair of novels, Specter of the Past and Vision of the Future, written by Timothy Zahn and set in the Star Wars galaxy. ...

Invisibility of nonexistent things

People have attributed invisibility to things that do not exist in order to explain why they're not apparent. In the Middle Ages, fern seeds were thought to be invisible since ferns don't have seeds. They were also said to grant invisibility.[2] In medieval astronomy, the crystal spheres[3] that held up the sun, moon, stars, and planets were invisible. Historically, creatures such as goblins and 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. The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ... Classes Marattiopsida Osmundopsida Gleicheniopsida Pteridopsida A fern, or pteridophyte, is any one of a group of about 20,000 species of plants classified in the Division Pteridophyta, formerly known as Filicophyta. ... This writeup is about biological seeds; for other meanings see Seed (disambiguation). ... A giant Hubble mosaic of the Crab Nebula. ... A goblin is an evil or mischievous creature of folklore, often described as a grotesquely disfigured, elf-like phantom. ... A signature Cox Brownie A brownie, brounie/Urisk (Lowland Scots) or ùruisg/brùnaidh (Scottish Gaelic) is a legendary kind of elf popular in folklore around Scotland and England (especially the north). ... This article is about the paranormal. ... The demon Satan In folklore, mythology, and religion, a demon is a supernatural being that is generally described as an evil spirit, but is also depicted to be good in some instances. ... QI, standing for Quite Interesting, is a comedy panel game television show hosted by Stephen Fry and shown on BBC Two and BBC Four. ... In New Age belief, Aura refers to the energy field emanating from the surface of a person or object. ...

See also

• Qualitative invisibility
• Concealment
• Cloaking device

In CAD/CAM, Qualitative Invisibility (QI) is the number of solid bodies obscuring a point in space as projected onto a plane (called [vector] hidden line removal used by the Vector_format). ... Look up hiding in Wiktionary, the free dictionary. ... A Klingon Bird of Prey from Star Trek VI: The Undiscovered Country fires while using a cloaking device but is eventually destroyed by the USS Enterprise. ...

External links

• Invisibility in the real world Interesting picture of a test tube's bottom half invisible in cooking oil.
• Info on "stealth suit"
• Some examples
• CNN article on an "actual" invisibility suit
  • Note: the picture was taken by a special camera that displays images behind the wearer of the suit. The suit itself does not render invisibility. In essence, the suit functions as a bluescreen onto which the image behind the suit can be displayed through camera.
• Plasmonic invisibility effect Plasmons are electron configurations on a metallic surface that resonate with a specific frequency or photon wavelength of light. This effect has so far been observed only in gold foil perforated with holes smaller than the photons. The oversize photons pass through the foil anyway (reportedly with amplification), so a quantum-tunneling phenomenon may be associated with the light wave trapping.
  • A monochromatic LED flashlight shined on a plasmonicly resonant surface would not allow that specific color of light to scatter back toward the light source. Plasmons act analogously to wave trap circuits familiar to builders of amateur radio equipment, except plasmons measure in Ångstrom-unit sizes.
• Theoretical method of scattering light (Nature.com subscription) that could make objects "invisible" to certain light frequencies. This is the source of the Livescience.com story on plasmons (above).
  • Unfortunately, this could not be used to hide anything but a microscopic object from visible light because the object has to be either the same size as the wavelength of light from which it is hidden, or only somewhat larger.
• Brief piece on why visible light is visible
• Says how an invisibility cloak works
• Scientists Aim to Duplicate Harry Potter's Invisibility Cloak
• Invisibility shield
• Reuters about Ulf Leonhart bending light to flow around an object, making it appear invisible
• Site about human spontaneous involuntary invisibility

An angstrom, angström, or ångström (symbol Å) is a unit of length. ...

References