An ansible is a category of fictional device or technology capable of near-instantaneous or superluminal communication. It can send and receive messages to and from a corresponding device over any distance or obstacle whatsoever with no delay, even between star systems. As a name for such a device, the word "ansible" first appeared in a 1966 novel by Ursula K. Le Guin. Since that time, the term has been broadly used in the works of numerous science fiction authors, across a variety of settings and continuities.
Ursula K. Le Guin coined the word "ansible" in her 1966 novel Rocannon's World. The word was a contraction of "answerable", as the device would allow its users to receive answers to their messages in a reasonable amount of time, even over interstellar distances.
Although Le Guin invented the name "ansible" for this type of device, fleshed out with specific details in her fictional works, the broader concept of instantaneous or faster-than-light communication had previously existed in science fiction. For example, similar communication functions were included in a device called an interocitor in the 1952 novel This Island Earth by Raymond F. Jones, and the 1955 film based on that novel, and in the "Dirac Communicator", which first appeared in James Blish's short story "Beep" (1954), which was later expanded into the novel The Quincunx of Time (1973).
In her subsequent works, Le Guin continued to develop the concept of the ansible:
Any ansible may be used to communicate through any other, by setting its coordinates to those of the receiving ansible. They have a limited bandwidth which only allows for at most a few hundred characters of text to be communicated in any transaction of a dialog session, and are attached to a keyboard and small display to perform text messaging.
Since Le Guin's conception of the ansible, the name of the device has been borrowed by numerous authors. While Le Guin's ansible was said to communicate "instantaneously", the name has also been adopted for devices capable of communication at finite speeds that are faster than light.
Orson Scott Card, in his 1977 novelette and 1985 novel Ender's Game and its sequels, used the term "ansible" as an unofficial name for the philotic parallax instantaneous communicator, a machine capable of communicating across infinite distances with no time delay. In Ender's Game, a character stated that "somebody dredged the name ansible out of an old book somewhere."
In the universe of the Ender's Game series, the ansible's functions involved a fictional subatomic particle, the philote. 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; however, in reality, quark confinement prevents quarks from being separated by any observable distance.
Numerous other writers have included ansibles in their fictional works, using that word to refer to a faster-than-light communication device. Notable examples include:
They print Reumere's plans for the ansible. 'What is the ansible?' 'It's what he's calling an instantaneous communication device.'
What matters is we built the ansible. The official name is Philotic Parallax Instantaneous Communicator, but somebody dredged the name ansible out of an old book somewhere and it caught on.
'It's an ansible.' 'Surely they don't call it that!' 'No. But that's what it is.'
...when I was commissioned, we didn't have FTL communications except from planetary platforms. I was on Boarhound when they mounted the first shipboard ansible, and at first it was only one-way, from the planet to us.
A connection [?ansible] was left; awaiting the next quiet [?peace]; and though destroyed by the threes, it will scream over the void one time.
The two Dax symbionts can communicate with each other across space, instantaneously, because they're composed of identical quantum particles. I've become a living ansible, Benjamin.
I can see Nightenhelser madly taking notes on his recorder ansible.
We are born as memories and meat. The meat was spontaneously created in the ansible's quantum re-creation mechanism, built up from water vapor, hydrogen, carbon dioxide, and various other gases out of storage. The memory is what we carry across from one side of the ansible to the other, into the new flesh.