Ansible

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The term ansible is used in science fiction literature to describe a hypothetical faster-than-light communication device. It was coined by Ursula K. Le Guin in her 1966 novel, Rocannon's World. 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), though it is often theorized that it is a deliberate anagram of the word "lesbian" (which is in keeping with the libertarian tones in her writing). Her award-winning 1974 novel The Dispossessed tells of the invention of the ansible within her Ekumen milieu.

The name and basic function of the device have since been borrowed by authors such as Frank Herbert, Orson Scott Card, Elizabeth Moon, Vernor Vinge, L.A. Graf, Dan Simmons, and Philip Pullman (though his was called a "lodestone resonator"). Other science fiction stories have devices with similar effects that are not called ansibles; perhaps the best known is Star Trek's "subspace radio". One ansible-like device which predates Le Guin's usage is the "Dirac communicator" in James Blish's 1954 short story "Beep".

Le Guin's ansible communicated instantaneously, and so do most other authors'. A notable exception is the ansible in the Vinge short story "The Blabber", which merely communicates faster than light — in a universe where that is believed impossible.

There is no known way to build an ansible. While current theories of physics do not absolutely rule out the possibility, the theory of special relativity predicts that any such device would allow communication from the future to the past, which raises problems of causality. For this reason, most physicists believe that they will eventually be proven impossible. Quantum entanglement is often proposed as a mechanism for superluminal communication, but our current understanding of that phenomenon is that it cannot be used for any sort of communication, superluminal or otherwise. See time travel and faster-than-light for more discussion of these issues.

Orson Scott Card's Ender's Game series is probably the most widely read work to use an ansible ("The official name is Philotic Parallax Instantaneous Communicator," explains Col. Graff in Ender's Game, "but somebody dredged the name ansible out of an old book somewhere"). His description of ansible functions in Xenocide involve a fictional subatomic particle, the philote, and contradicts not only standard physical theory but the results of empirical particle accelerator experiments. In the "Enderverse", the two quarks inside a pi meson can be separated by an arbitrary distance while remaining connected by "philotic rays". In the real world, quark confinement prevents one from separating quarks by more than microscopic distances. Most writers deliberately avoid explaining how their ansibles work; Card elaborated only because philotics became important to later volumes of the series.

See also tachyon.

Ansible is also a science fiction fanzine published by Dave Langford, named after the faster-than-light communicator.

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