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An ansible is a hypothetical machine capable of instantaneous or superluminal communication. Ansibles occur as plot device
Plot device
A plot device is an object or character in a story whose sole purpose is to advance the plot of the story, or alternatively to overcome some difficulty in the plot....

s in science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...



The word ansible was coined by Ursula K. Le Guin
Ursula K. Le Guin
Ursula Kroeber Le Guin is an American author. She has written novels, poetry, children's books, essays, and short stories, notably in fantasy and science fiction...

 in her 1966 novel, Rocannon's World
Rocannon's World
Rocannon's World is Ursula K. Le Guin's first novel. It was published in 1966 as an Ace Double, along with Avram Davidson's The Kar-Chee Reign, following the tête-bêche format. Though it is one of Le Guin's many works set in the universe of the technological Hainish Cycle, the story itself has many...

. Le Guin states that she derived the name from "answerable," as the device would allow its users to receive answers to their messages in a reasonable amount of time, even over interstellar distances. Her award-winning 1974 novel
A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....

 The Dispossessed
The Dispossessed
The Dispossessed: An Ambiguous Utopia is a 1974 utopian science fiction novel by Ursula K. Le Guin, set in the same fictional universe as that of The Left Hand of Darkness . The book won the Nebula Award for Best Novel in 1974, both the Hugo and Locus Awards in 1975, and received a nomination for...

, a book in the Hainish Cycle, tells of the invention of the ansible.


The name of the device has since been borrowed by authors such as Orson Scott Card
Orson Scott Card
Orson Scott Card is an American author, critic, public speaker, essayist, columnist, and political activist. He writes in several genres, but is primarily known for his science fiction. His novel Ender's Game and its sequel Speaker for the Dead both won Hugo and Nebula Awards, making Card the...

Vernor Vinge
Vernor Vinge
Vernor Steffen Vinge is a retired San Diego State University Professor of Mathematics, computer scientist, and science fiction author. He is best known for his Hugo Award-winning novels and novellas A Fire Upon the Deep , A Deepness in the Sky , Rainbows End , Fast Times at Fairmont High ...

, Elizabeth Moon
Elizabeth Moon
Elizabeth Moon is an American science fiction and fantasy author. Her novel The Speed of Dark won the 2003 Nebula Award.-Biography:...

, Jason Jones
Jason Jones (programmer)
Jason Jones is a game developer and programmer who co-founded video game studio Bungie with Alex Seropian in 1991. Jones began programming on Apple computers in high school, assembling a multiplayer game called Minotaur: The Labyrinths of Crete...

, L.A. Graf, and Dan Simmons
Dan Simmons
Dan Simmons is an American author most widely known for his Hugo Award-winning science fiction series, known as the Hyperion Cantos, and for his Locus-winning Ilium/Olympos cycle....

. Similar devices are present in the works of numerous others, such as Frank Herbert
Frank Herbert
Franklin Patrick Herbert, Jr. was a critically acclaimed and commercially successful American science fiction author. Although a short story author, he is best known for his novels, most notably Dune and its five sequels...

 and Philip Pullman
Philip Pullman
Philip Pullman CBE, FRSL is an English writer from Norwich. He is the best-selling author of several books, most notably his trilogy of fantasy novels, His Dark Materials, and his fictionalised biography of Jesus, The Good Man Jesus and the Scoundrel Christ...

, who called his a lodestone resonator.

Anne McCaffery's Crystal Singer
Crystal Singer
The Crystal Singer , or Crystal Singer is a science fiction, young-adult novel by Anne McCaffrey. It is a fix-up of four stories published 1974 and 1975 and is the first book set in her "Crystal universe"...

 series posited an instantaneous communication device powered by rare 'Black Crystal' from the planet Ballybran. Black Crystals cut from the same mineral deposit could be "tuned" to sympathetically vibrate with each other instantly, even when separated by interstellar distances, allowing instantaneous telephone-like voice and data communication. Similarly, in Gregory Keyes
Gregory Keyes
Gregory Keyes is an American writer of science fiction and fantasy who has written both original and media-related novels under both the names "J. Gregory Keyes" and "Greg Keyes". He is famous for his quartet The Age of Unreason, a steampunk/alchemical story starring Benjamin Franklin and Isaac...

' series The Age of Unreason
The Age of Unreason
The Age of Unreason is a series of four novels written by Gregory Keyes:* Newton's Cannon , ISBN 1-56865-829-X* A Calculus of Angels , ISBN 0-7394-0260-9* Empire of Unreason , ISBN 0-345-40609-5...

, "aetherschriebers" use two halves of a single "chime" to communicate, aided by scientific alchemy. The series is set on an alternate 18th-century Earth. While the speed of communication is important, so is the fact that the messages cannot be overheard except by listeners with a piece of the original crystal.

Stephen R. Donaldson
Stephen R. Donaldson
Stephen Reeder Donaldson is an American fantasy, science fiction and mystery novelist, most famous for his Thomas Covenant series...

, in his Gap Series, proposed a similar system, Symbiotic Crystalline Resonance Transmission, clearly ansible-type technology, but was very difficult to produce and limited to text messages.

Some hard science fiction
Hard science fiction
Hard science fiction is a category of science fiction characterized by an emphasis on scientific or technical detail, or on scientific accuracy, or on both. The term was first used in print in 1957 by P. Schuyler Miller in a review of John W. Campbell, Jr.'s Islands of Space in Astounding Science...

 stories use small (possibly nano-sized) paired wormholes dedicated to communication by means of a laser which traverses the wormhole.

Charles Stross
Charles Stross
Charles David George "Charlie" Stross is a British writer of science fiction, Lovecraftian horror and fantasy. He was born in Leeds.Stross specialises in hard science fiction and space opera...

's books Singularity Sky
Singularity Sky
- External links :* at * * at Worlds Without End...

 and Iron Sunrise
Iron Sunrise
Iron Sunrise is a 2004 hard science fiction novel by author Charles Stross, which follows the events in Singularity Sky. The book was nominated for both the Hugo and Locus Awards in 2005....

 make use of "causal channels" which use entangled particles for instantaneous two-way communication. The technique has drawbacks in that the entangled particles are expendable and the use of faster-than-light travel destroys the entanglement, so that one end of the channel must be transported below light speed. This makes them expensive and limits their usefulness somewhat.

In Richard K. Morgan's Takeshi Kovacs
Takeshi Kovacs
Takeshi Lev Kovacs is the protagonist of the books Altered Carbon, Broken Angels, and Woken Furies by Richard K. Morgan, which take place several centuries in the future....

 novels human colonies on distant planets maintain contact with earth and each other via hyperspatial needlecast, a technology which moves information "...so close to instantaneously that scientists are still arguing about the terminology...".

One ansible-like device which predates Le Guin's is the Dirac communicator in James Blish
James Blish
James Benjamin Blish was an American author of fantasy and science fiction. Blish also wrote literary criticism of science fiction using the pen-name William Atheling, Jr.-Biography:...

's 1954 short story "Beep". As the title implies, any active device received the sum of all transmitted messages in universal space-time, in a single pulse, so that demultiplexing yielded information about the past, present, and future.

Isaac Asimov
Isaac Asimov
Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...

 solved the same communication problem with the hyper-wave relay in the Foundation series
The Foundation Series
The Foundation Series is a science fiction series by Isaac Asimov. There are seven volumes in the Foundation Series proper, which in its in-universe chronological order are: Prelude to Foundation, Forward the Foundation, Foundation, Foundation and Empire, Second Foundation, Foundation's Edge, and...


Le Guin's ansible was said to communicate "instantaneously", but other authors have adopted the name for devices only capable of finite-speed communication, although still faster than light.

The subspace radio, best known today from Star Trek
Star Trek
Star Trek is an American science fiction entertainment franchise created by Gene Roddenberry. The core of Star Trek is its six television series: The Original Series, The Animated Series, The Next Generation, Deep Space Nine, Voyager, and Enterprise...

 and named for the method used in the series for achieving faster-than-light travel, was the most commonly used name for such a faster-than-light communicator in the science fiction of the 1930s to the 1950s.

In all the Stargate
Stargate is a adventure military science fiction franchise, initially conceived by Roland Emmerich and Dean Devlin. The first film in the franchise was simply titled Stargate. It was originally released on October 28, 1994, by Metro-Goldwyn-Mayer and Carolco, and became a hit, grossing nearly...

 television series, characters are able to communicate instantaneously over long distances by transferring their consciousness into another person or being anywhere in the universe using "Ancient
Ancient (Stargate)
The Ancients are a humanoid race in the fictional Stargate universe. They are called "Ancients" in the Milky Way, but are also known as Lanteans or Ancestors in the Pegasus galaxy and as the Alterans in their home galaxy, and they sometimes call themselves Anquietas in their language...

 communication stones". It is not known how these stones operate, but the technology explained in the show usually revolves around wormhole
In physics, a wormhole is a hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime. For a simple visual explanation of a wormhole, consider spacetime visualized as a two-dimensional surface. If this surface is folded along a third dimension, it...

s for instant teleportation, faster-than-light, space-warping travel, and sometimes around quantum multiverses.

In Le Guin's work

In The Word for World Is Forest
The Word for World is Forest
The Word for World Is Forest is a science fiction novel by Ursula K. Le Guin, published in 1976 and based on her 1972 novella which was nominated for a Nebula Award.It is part of Le Guin's Hainish Cycle.-Setting:...

, Le Guin explains that in order for communication to work with any pair of ansibles, at least one "must be on a large-mass body, the other can be anywhere in the cosmos."

In The Left Hand of Darkness
The Left Hand of Darkness
The Left Hand of Darkness is a 1969 science fiction novel by Ursula K. Le Guin. It is part of the Hainish Cycle, a series of books by Le Guin all set in the fictional Hainish universe....

, the ansible "doesn't involve radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 waves, or any form of energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

. The principle it works on, the constant of simultaneity
Simultaneity is the property of two events happening at the same time in at least one frame of reference. The word derives from the Latin simul, at the same time plus the suffix -taneous, abstracted from spontaneous .The noun simult means a supernatural coincidence, two or more divinely...

, is analogous in some ways to gravity ... One point has to be fixed, on a planet of certain mass, but the other end is portable."

Unlike McCaffrey's black crystal transceivers, Le Guin's ansibles are not mated pairs: it is possible for an ansible's coordinates to be set to any known location of a receiving ansible. Moreover, the ansibles Le Guin uses in her stories apparently have a very limited bandwidth
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...

 which only allows for at most a few hundred characters of text to be communicated in any transaction of a dialog session. Instead of a microphone and speaker, Le Guin's ansibles are attached to a keyboard and small display to perform text messaging
Text messaging
Text messaging, or texting, refers to the exchange of brief written text messages between fixed-line phone or mobile phone and fixed or portable devices over a network...


In Card's work

Orson Scott Card
Orson Scott Card
Orson Scott Card is an American author, critic, public speaker, essayist, columnist, and political activist. He writes in several genres, but is primarily known for his science fiction. His novel Ender's Game and its sequel Speaker for the Dead both won Hugo and Nebula Awards, making Card the...

's Ender's Game series
Ender's Game series
The Ender's Game series is a series of science fiction books by Orson Scott Card. The series started with the novelette "Ender's Game", which was later expanded into the novel Ender's Game. It currently consists of eleven novels and ten short stories...

 uses the ansible as a plot device. "The official name is Philotic Parallax Instantaneous Communicator," explains Colonel Graff in Ender's Game
Ender's Game
Ender's Game is a science fiction novel by American author Orson Scott Card. The book originated as the short story "Ender's Game", published in the August 1977 issue of Analog Science Fiction and Fact. Elaborating on characters and plot lines depicted in the novel, Card later wrote additional...

, "but somebody dredged the name ansible out of an old book somewhere."

Card's description of the ansible's functions in Xenocide
Xenocide is the third novel in the Ender's Game series of books by Orson Scott Card. It was nominated for both the Hugo and Locus Awards for Best Novel in 1992...

involve a fictional subatomic particle, the philote, and contradicts not only standard physical theory but also the results of empirical particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...


In the "Enderverse", the two quark
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...

s inside a pi meson
In particle physics, a pion is any of three subatomic particles: , , and . Pions are the lightest mesons and they play an important role in explaining the low-energy properties of the strong nuclear force....

 can be separated by an arbitrary distance while remaining connected by "philotic rays". This concept is similar to quantum teleportation
Quantum teleportation
Quantum teleportation, or entanglement-assisted teleportation, is a process by which a qubit can be transmitted exactly from one location to another, without the qubit being transmitted through the intervening space...

 due to entanglement
Quantum entanglement
Quantum entanglement occurs when electrons, molecules even as large as "buckyballs", photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description , which is...

, although even that does not imply a possibility of faster-than-light communication. Also, in the real world, quark confinement prevents quarks from being separated by more than microscopic distances.

The novels' treatment of time dilation
Time dilation
In the theory of relativity, time dilation is an observed difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from gravitational masses. An accurate clock at rest with respect to one observer may be measured to tick at...

 is also inconsistent with standard theory. In the novels, the passenger of a starship experiences time compression, resulting in slowed speech when communicating over the ansible. This contradicts the core concept of the theory of relativity
Theory of relativity
The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....

 by giving the planet a privileged frame of reference. It is no more correct to say that the planet is at rest and the ship moving than to say that the ship is at rest and the planet moving backwards. As such, we find a paradox in which the person at each end of an ansible expects the other person to be time dilated and speaking slowly. In light speed or slower communications, this paradox is avoided due to the expected message delays, as in the Twin paradox
Twin paradox
In physics, the twin paradox is a thought experiment in special relativity, in which a twin makes a journey into space in a high-speed rocket and returns home to find he has aged less than his identical twin who stayed on Earth...

. Instantaneous communications, however, does result in a paradox, as each communicator expected the other to be slowed.

The ansible is also feature of the video game Advent Rising
Advent Rising
Advent Rising is a third-person, science fiction action-adventure video game. It was developed by GlyphX Games and published by Majesco. The game was released on May 31, 2005 for Xbox and on August 9, 2005 for Microsoft Windows. The story of this game was created by Donald Mustard, and featured a...

, for which Card helped write the story.

In reality

There is no currently known way to build an ansible. The theory of special relativity
Special relativity
Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...

 predicts that any such device would allow communication from the future to the past, which raises problems of causality
Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....

, unless the device used general relativistic curved spacetimes as an integral part.

Quantum nonlocality
Quantum nonlocality
Quantum nonlocality is the phenomenon by which measurements made at a microscopic level necessarily refute one or more notions that are regarded as intuitively true in classical mechanics...

 is often proposed as a mechanism for superluminal communication. A 2008 quantum physics experiment performed in Geneva, Switzerland has determined that in any hypothetical nonlocal hidden-variables theory the speed of the quantum non-local connection would have to be at least 10,000 times the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

. Practical applications are made impossible due to the no-cloning theorem, and the fact that quantum field theories preserve causality, so that quantum correlations cannot be used to transfer information.

Nevertheless, consider the EPR
EPR paradox
The EPR paradox is a topic in quantum physics and the philosophy of science concerning the measurement and description of microscopic systems by the methods of quantum physics...

 thought experiment, and suppose quantum states could be cloned. Assume parts of a maximally entangled Bell state
Bell state
The Bell states are a concept in quantum information science and represent the simplest possible examples of entanglement. They are named after John S. Bell, as they are the subject of his famous Bell inequality. An EPR pair is a pair of qubits which jointly are in a Bell state, that is, entangled...

 are distributed to Alice and Bob. Alice could send bits to Bob in the following way: If Alice wishes to transmit a "0", she measures the spin of her electron in the z direction, collapsing Bob's state to either |z+> or |z->. To transmit "1", Alice does nothing to her electron. Bob creates many copies of his electron's state, and measures the spin of each copy in the z direction. Bob will know that Alice has transmitted a "0" if all his measurements produce the same result; otherwise, his measurements will have outcomes +1/2 and −1/2 with equal probability. This would allow Alice and Bob to communicate near instantly across space-like separations.

See time travel
Time travel
Time travel is the concept of moving between different points in time in a manner analogous to moving between different points in space. Time travel could hypothetically involve moving backward in time to a moment earlier than the starting point, or forward to the future of that point without the...

 and faster-than-light
Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....

 for more discussion of these issues.

See also

  • Faster-than-light
    Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....

  • Interstellar communication
    Interstellar communication
    Interstellar communication is the transmission of signals between planetary systems. Sending Interstellar messages is potentially much easier than interstellar travel, being possible with technologies and equipment which are currently available...

  • No-cloning theorem
  • Tachyon
    A tachyon is a hypothetical subatomic particle that always moves faster than light. In the language of special relativity, a tachyon would be a particle with space-like four-momentum and imaginary proper time. A tachyon would be constrained to the space-like portion of the energy-momentum graph...

  • Tachyonic antitelephone
    Tachyonic antitelephone
    A tachyonic antitelephone is a hypothetical device in theoretical physics that could be used to send signals into one's own past. Albert Einstein in 1907...

External links