Ansible

An ansible is a hypothetical machine capable of instantaneous or superluminal communication. Ansibles occur as plot devices in science fiction literature.

Origin

The word ansible was coined by Ursula K. Le Guin in her 1966 novel Rocannon's World.^[1] 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.^[2] Her award-winning 1974 novel The Dispossessed,^[3] a book in the Hainish Cycle, tells of the invention of the ansible.

Usage

The name of the device has since been borrowed by authors such as Orson Scott Card,^[4] Vernor Vinge,^[5] Elizabeth Moon,^[6] Jason Jones,^[7] L.A. Graf,^[8] and Dan Simmons.^[9] Similar devices are present in the works of numerous others, such as Frank Herbert^[10] and Philip Pullman, who called his a lodestone resonator.^[11]

Anne McCaffrey's Crystal Singer 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' series The Age of Unreason, "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, 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 stories use small (possibly nano-sized) paired wormholes dedicated to communication by means of a laser which traverses the wormhole.^{[citation needed]} In Robert L. Forward's novel Timemaster, the wormhole is a living organism resembling a fourth-dimensional sea anemone, "stretched" to cover the distance between a spaceship and a satellite on the home planet.

Charles Stross's books Singularity Sky and Iron Sunrise 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 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'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 solved the same communication problem with the hyper-wave relay in the Foundation series.

Le Guin's ansible was said to communicate "instantaneously",^[3] 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 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.^{[citation needed]}

In all the Stargate 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 communication stones". It is not known how these stones operate, but the technology explained in the show usually revolves around wormholes 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, 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 ansible "doesn't involve radio waves, or any form of energy. The principle it works on, the constant of simultaneity, 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 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.

In Card's work

Orson Scott Card's Ender's Game series uses the ansible as a plot device. "The official name is Philotic Parallax Instantaneous Communicator," explains Colonel Graff in Ender's Game, "but somebody dredged the name ansible out of an old book somewhere."^[4]

Card's description of the ansible's functions in Xenocide involve a fictional subatomic particle, the philote. In the "Enderverse", the two quarks inside a pi meson can be separated by an arbitrary distance while remaining connected by "philotic rays". This concept is similar to quantum teleportation due to entanglement, 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 gravitational time dilation is consistent with standard theory. In the novels, the passenger of a starship experiences time compression, resulting in slowed speech when communicating over the ansible. This is due to the fact that time passes at different rates in regions of different gravitational potential. General relativity states gravity and acceleration to be indistinguishable from one another. As the starship attains relativistic speeds its gravitational potential increases, and the speed at which it travels through time decreases. This concept is the same as that which was used by Einstein as a solution to the Twin paradox. Since the starship is moving more slowly through time, but still able to communicate instantaneously, communications appear to slow when received from the ship. This is not due to the messages being dilated during transmission, but simply due to the fact that the user on the starship interfaces with the communication device at a slower rate when compared to the stationary user.

The ansible is also feature of the video game Advent Rising, for which Card helped write the story.

In Moon's Work

There is a brief reference to the ansible in Winning Colors^[6]. The ansible itself is a major plot element, nearly a MacGuffin in Moon's Vatta's War series. Much of the story line revolves around various parties attacking or repairing ansibles, and around the internal politics of ISC (InterStellar Communications), which holds a monopoly on the ansible technology.^[12]

In reality

There is no currently known way to build an ansible. The theory of special relativity predicts that any such device would allow communication from the future to the past, which raises problems of causality, unless the device used general relativistic curved spacetimes as an integral part.

Quantum nonlocality is often proposed as a mechanism for superluminal communication.^[11] 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.^[13] 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.

See time travel and faster-than-light for more discussion of these issues.

See also

Novels portal

• Faster-than-light
• Interstellar communication
• No-cloning theorem
• Tachyon
• Tachyonic antitelephone

Footnotes

References

• Bernardo, Susan M.; Murphy, Graham J. (2006). Ursula K. Le Guin: A Critical Companion (1st ed.). Westport, CT: Greenwood Press. ISBN 0-313-33225-8. 
• Bloom, Harold, ed. (1986). Ursula K. Le Guin (1st ed.). New York, NY: Chelsea House. ISBN 0-87754-659-2. 

External links

• Ansible from the Oxford English Dictionary
• Science Fiction Citations project
• Ansible at Technovelgy
• Ansible Home Page (fanzine)
• "Ansible Music (Music)