Subspace Ansible - Television Tropes & Idioms

alt title(s): FTL Radio

Space is big. No, really big. You might think it's a long way to the chemist, but that's peanuts compared to space. The only way to have snappy dialogue between characters in different star systems (hell, even different planets) is with faster than light radio. This Subspace Ansible (a.k.a. FTL Radio) is also necessary for spaceships using Faster Than Light Travel to have two-way conversations, since actual radio waves are light (sort of) - and are therefore slower than the ship.

There are several types of faster than light technologies in fiction; however, Subspace Ansibles need to use one that doesn't require sending the ship's engines along with the message. So, they typically use the "shortcut" method: sending ordinary radio waves through an exotic Subspace Or Hyperspace that is smaller than real space.

If the setting has both subspace and hyperspace, then typically subspace will allow nearly-instant communication, but can't be used for travel. Even in Star Trek, which uses subspace for both, real-time conversations take place between characters who are days of FTL Travel apart. This allows plots to be written as if Space Is An Ocean.

In some cases, a Subspace Ansible may exist even if Faster Than Light Travel does not. There might be some attempt to justify this, proposing that technology exists to bypass the limits of relativity for information but not matter, but often, it is simply a matter of necessity: while a single-star-system Space Opera can get by without Faster Than Light Travel, it takes several minutes for radio waves to travel the distance from Earth to Mars, the problem of communication remains pressing even if Faster Than Light Travel can be safely shelved.

Presumably, an FTL Radio is also what allows ship sensors to work faster than light, viewing objects that are light-minutes away - or even light-years! - in real-time. However, any attempts to explain it are indistinguishable from a Hand Wave. (Unless Tachyons are involved. Then it gets complicated.)

The term "ansible" for this kind of near-instantaneous subspace communication system was coined by Ursula K. Le Guin in her 1966 novel, Rocannon's World. "Ansible" is a derivation of "answerable", i.e. "messages will be answerable in realtime". (It's also an anagram of "lesbian.") Many other science-fiction writers picked up the name after Le Guin.

If Psychic Powers exist in a setting, they often work instantaneously at any distance, and function as a Subspace Ansible.

Examples:

Literature

The ansible appears in most of Le Guin's Ekumen novels. In The Dispossessed she tells, among other things, the story of its invention.
Enders Game is a major example of another writer taking the name from Le Guin. A character mentions that there is a formal name for their FTL Radio, but "somebody dredged the name ansible out of an old book." The working principle of an ansible link is something about "subatomic philotic links" that form between two subatomic particles, which can be stretched infinitely when properly separated.
- These links are also both The Power Of Friendship and what holds the universe together.
James Hogan uses a similar system (and also worked in the computer industry — for DEC during the PDP minicomputer days) in his Gentle Giants series of books where both communication and FTL travel are accomplished through rotating black holes. Toroidal black holes. A similar concept is used in his book The Genesis Machine, in which a Cold War era book about a machine that is initially used to pull information from remote places in real time without there being a device on the other end to transmit the data is turned into a superweapon to stop the Cold War in its tracks — by causing a nuclear exchange and destroying the missiles before they hit the ground.
Richard Morgan's Altered Carbon features "needlecasts", but no FTL travel. Interestingly, since Brain Uploading is routine, people may travel from planet to planet by downloading into a local body.
- The information only aspect is a power limitation not a inherent one in the functionality. The information that is transmitted is transmitted by energy, the best matter energy conversion reactors they have can hold open a needlecast portal for at best 15 to 30 seconds and transmit only blinking light. They find a stable stargate style portal created by the precursors and they actually extrapolate the energy costs and realize that a hiccup in the portals matrix would crack the planet open like an egg. Hazards of children playing with adult toys.
In Time for the Stars by Robert A Heinlein, telepathy is used for instantaneous communication. Eventually, scientists studying the process learn how how it works well enough to create Faster Than Light Travel as well.
Similarly, in E.E. "Doc" Smith's Lensman series, the titular Lens enhances the Lensmen's telepathic abilities, thus allowing instantaneous communication between them.
- There are also a variety of "waves" and "rays" that can be used for FTL communication and sensors by people who aren't Lensmen.
Likewise, in the Talents universe of Anne McCaffrey, Psychic Powers not only provide interstellar communication, but interstellar travel by psychokinetic teleportation.
In the Charles Stross novels Singularity Sky and Iron Sunrise, FTL communication is possible through the use of quantum-entangled particles, however: a) the communication is only possible between paired transceivers, and b) taking "qbits" through an FTL jump destroys the entanglement. This means that useful interstellar communicators have to be shipped the long way 'round, making them very expensive.
Notable subversion in James Blish's short story "Beep". Ansibles are common and cheap to use, if you can stand the loud and annoying beep that accompanies every one. Due to quantum effects, the titular beep contain every message that ever was or will be sent, ever, and they can be heard if slowed way, way down and appropriately filtered. The government's primary purpose is to ensure that the events described in the beep come to pass at all costs, to prevent a paradox from prematurely ending the universe.
The Fatline in Dan Simmon's Hyperion uses modulated neutrinos (or some such Phlebotinum) to send messages instantly across interstellar distances. At the end of the second book God(?) revokes their radio privileges completely, since the transmission medium (the Void Which Binds) is disrupted everytime a message is sent.
Alan Dean Foster uses the Subspace Or Hyperspace version in his Humanx Commonwealth series. "Space plus" is hyperspace and is used for Faster Than Light Travel - it can also be used for communication but at the same speed as starships. "Space minus" is subspace and can be used for near-instantaneous communication, but at a very high energy cost.
Though it never actually comes up, the Discworld series has a bit of fun with this in a footnote. It points out that a Disc philosopher decided that the fastest thing in the universe is monarchy, noting that regardless of distance, the instant a monarch dies, the heir immediately succeeds them. He further proposes subatomic particles—kingons, or perhaps queenons—but his rough-hewen plans for artificially generating them by torturing a minor noble and using them to send messages vast distances were cut short when the bar closed.
The first Stainless Steel Rat novels by Harry Harrison feature psychics used explicitly as communicators over interstellar distances. Later novels don't seem to rely that much on conversations at distance.
Heightened stellar activity can interfere with FTL communications in the Wing Commander universe, as shown in the novel Action Stations (aka "Pearl Harbor IN SPACE"), but otherwise, the only time there's significant time lag for communicating across interstellar distances is the human steps relaying transmitted messages to/from the comm system and the people ultimately at either end of the line.
The operation of these are a major plot point in Elizabeth Moon's Vattas War series.

Anime and Manga

In Macross Frontier, the Vajra are capable of interstellar communication via their Hive Mind link, which uses symbiotic, fold quartz-carrying bacteria in their entrails to link the whole species together instantaneously across the galaxy, without any sort of fold interference or delay. In fact, abusing this galactic overmind to link up the entire galaxy whether it wants to or not (humanity included) is the major goal of the Big Bad.
The ability of the Emilys from Soukou No Strain. Which led to them being cranially bisected alive by human scientist to obtain it. Being Hive Mind, they share the pain as well...

Film

According to Avatar's wiki, the Pandorapedia, the Venture Star has faster-than-light communication technology with a low-bitrate device using quantum-entangling. This is a case of All There In The Manual, as this Ansible was never shown or mentioned in the film itself. Actual faster-than-light travel is notably averted.

Comic Books

In Legion Of Superheroes comics, communications are relayed through the same Stargate system used for FTL travel, making it possible to have a real time conversation between Legion HQ on Earth and the Legion Outpost in deep space. In the post-Zero Hour, pre-Infinite Crisis Legion, when the Stargate system goes down, people can still travel in "old fashioned" warp vessels, but the only means of communication is Titanet, a relay of Saturnian telepaths.

Live Action TV

Star Trek, as mentioned.
- However, when the plot required it in the Original Series, they'd make mention that their messages would take several days to reach a Star Base.
- They touched briefly on the logistics of subspace radio in the TNG episode "Aquiel," where the plot took place in what amounted to a repeater station.
- Communicating over long distances is important for the crew of the USS Voyager, as they're stuck on the other side of the galaxy (and presumed dead), so even subspace communication won't work. After several failed attempts, they eventually succeed via Lost Technology and Applied Phlebotinum.
Babylon 5's tachyon relays are a complicated bit of Applied Phlebotinum to justify this. It's established in-story that they're expensive and limited in bandwidth, with the result that most civilians have to rely on (hyperspace) snail-mail.
The Stargate Verse uses stuff like this on occasion, and it is explicitly stated that radio waves can travel both ways through wormholes, which work only one way for matter streams.
- Besides simply sending radio signals through stargates, plain old FTL radio is used, the range of which can be determined by one episode which involves relaying an important message to Atlantis by sending someone with a subspace radio to the outer edge of the Milky Way in order to contact the Daedalus, halfway between galaxies.
Used with subtlety on Firefly. The orbit-to-land transmissions lack any delay at all, which is impossible if they were ordinary radiowaves. The Movie has several conversations between Mal in deep space, and somebody else on a far away planet.
- The RPG actually does mention that communications in the Verse are hindered by a delay, which might be anything from 0.1 seconds to 10 hours depending on the distance.
Used without any justification Defying Gravity. It's far more jarring than in Firefly, because it only seems to be set about fifty years in the future and the rest of the space programs looks fairly similar to the way it is now.

Tabletop Games

In a typical Warhammer 40000 take on an otherwise innocuous trope, FTL communications within the Imperium are the responsibility of Astropaths, psykers who send telepathic messages to other planets... through hell...
- And frequently, the messages either arrive too late or not at all or are completely incomprehensible due to the receiving psyker not being able to work it out via space tarot cards or throwing chicken bones or... Well, there's one example of an Imperium ship going to its death responding to a distress call sent by its future self.
Eclipse Phase's Quantum Entangled Communicators provide instant communication regardless of distance, but like those in the Charles Stross example rely on pre-linked, finite "qbit reservoirs".
GURPS: Ultratech has two versions. The first uses quantum entanglement (so it's impossible to intercept) the second is generic FTL Radio.

Video Games

It is never explained how exactly communication works in the Descent: Freespace games. Seemingly, instant interstellar communications do occur in that universe, which means FTL communications. Command can also communicate with you as your ship is traveling in subspace, though the messages break up and distort like a bad telephone connection.
Mass Effect allows faster-than-light travel by giving physical objects zero or negative mass or through the use of large and fairly rare mass relays that create long tunnels of space where everything has zero or negative mass. Communications often take place through large numbers of comm buoys deployed throughout explored space, which transmit messages via photons passed through miniaturized corridors of mass-free space. Time lag in real-time communications occurs if transmitter bandwidth is overloaded, though high-level government operatives and military personnel get access to high-end, high-speed channels that allow near-instantaneous communications. Long-range interstellar calls are implied to be highly expensive, judging by one overheard conversation on Noveria.
The plot of Commander Keen 4 starts with Billy Blaze building a FTL radio and accidentallly picking up a transmission from a group of aliens planning on destroying the galaxy.
Eve Online uses pairs of particles which are synchronized with each other: Manipulating one affects the other as well, no matter the distance between the two particles. This was used to create a galaxy-wide network (not unlike the Internet) where latency due to physical distance is not an issue. Carrying one half of a particle pair on a spaceship allows one to "phone home" from any part of the galaxy.
- This is based (albeit loosely) on current research; it is supposed that, after splitting an atom in a certain way, changing the direction of one half's electron spin will also cause the other half's electrons to reverse the direction of their orbit, regardless of distance between the two. The reasons for this are not really understood.

Web Comics

Schlock Mercenary's main means of communication is the Hypernet, a refinement of the ansible idea as a packet-switched system that relies on tiny wormholes. It carries all communications in digital form, from real-time video to text mail, and it's explicitly said that the lag time in the sender's electronics is more significant than the infinitesimal transit time. The cartoonist knows a thing or two about packet switching; his former day job was for Cisco Systems.
The Starslip technical manual asserts that FTL communication is actually an incredibly sophisticated computer that anticipates what the other party will say. "Modern" systems are so good, it can predict and initiate a call at the same time it is placed, light-years away. FTL Travel is almost as preposterously handwaved.

Aversions With FTL Travel

Literature

In Poul Anderson's "Technic Civilization" novels and short stories, there is no "interstellar equivalent of radio" and all messages have to be carried by courier spaceships.
Ditto in The Gap series by Stephen Donaldson. Courier drones are the order of the day — although the Amnion do briefly try to use some sort of experimental "symbiotic crystalline resonance device" as an FTL Radio.
The Co Dominium universe and The Mote In God's Eye by Larry Niven and Jerry Pournelle.
The Honor Harrington series has courier ships to carry messages between star systems, but because of the delay, there's no way to control battle groups in multiple systems with military precision. Early in the series, The Kingdom figures out how to create a comm system using gravity pulses, but this only works within a system, and initially is roughly as fast (in terms of bandwidth) as Morse code. The technology undergoes multiple improvements, and in the later books is capable of carrying video.
David Feintuch's Seafort Saga: while FTL travel existed in the form of "N-Waves" propelling a ship, even human-level computer AI couldn't run a ship (robotics not being advanced in Feintuch's 'verse). Physical mail was carried by the ships traveling to extrasolar colonies, while ordinary radio was used in-system.
H. Beam Piper's Terro-Human Future History. News and communications travel with FTL starships — taking months to get to their destination, and months to get an answer back — but no FTL radio exists. This has a major impact during the System States War, in his novel The Cosmic Computer, where planning and controlling fleet and army movements has to be done for a theater of war thousands of light years across. In fact, the Terran Federation's "Manhattan Project" is to create a super-powerful computer capable of evaluating not only military but social and economic factors and effectively predict the enemy's future actions, so that the Terran generals can determine just where to send troops and ships.
- It can be said that Piper and other writers who have FTL travel but no FTL radio setups in their works often do so to justify why the protagonists must handle the issue at hand and can't just call back to base for help/relief/support from more qualified personnel.
In Peter F. Hamilton's Night's Dawn Trilogy, it is possible that certain alien races have developed FTL communications, but humans certainly have not. Information is couriered around by manned starships.
- In his Commonwealth series, constantly-maintained planetside wormholes allow very rapid transportation and communications from one end of the Commonwealth to the other. The most common method of travelling from planet to planet is by train, spaceships having been made redundant.
In Dune, the Spacing Guild is responsible for getting information from place to place. In the books by Frank Herbert's son, two Navigators manage to contact each other FTL with a device one of them cooked up, but that never caught on, mainly due to the unfortunate side effects (namely, fatal cerebral hemorrhaging after several uses).
- That never happened.
Lois McMaster Bujold's Miles Vorkosigan novels use wormholes as shortcuts through space; unfortunately, there's no way to send messages through a wormhole without recording them and putting them on a ship. High traffic routes have regular courier ships shuttling the mail back and forth through the wormholes. On low traffic routes, your mail may sit for weeks for someone to come along and carry it on. Once on the other side, a message may be beamed at the speed of light to the next wormhole (if there's a permanent station there) or it may be carried on a ship the whole way.
- The lack of FTL communication plays as a plot point a few times; in The Vor Game, Miles uses the time lag between communications to play with the head of his compulsive plotter opponent, Cavilo.
In Isaac Asimov's Nemesis, the humans left on Earth eventually discover faster-than-light travel, but point out that there is no way to send radio waves through hyperspace. This leads to difficulties communicating with the Nemesis colonists.
Averted in CJ Cherryh's Alliance Union and Chanur Saga series. Communications between star systems can only be done via FTL courier, and FTL travel is only possible between the outside edges of star systems. When a space ship arrives at the edge of a system and travels inwards it takes a long time for light-speed messages to reach the inner system (or visa-versa), with the time shortening as the ship hurtles forward at a considerable fraction of the speed of light.

Anime and Manga

The time taken for messages to reach to the other recipient is practically the entire point of Voices of a Distant Star. There is FTL Travel in Hoshi no Koe.
- There's also, briefly noted, some form of subspace communication. But it's only there for irony — a newspaper shown for a moment has a report on the next generation of starships, the ones built after Mikako's fleet leaves. The new ships will have this form of FTL communication; the fleet Mikako is in, however, does not.
  - And, to make the irony even more cruel, — Noboru is a comms officer on one of these new ships.
Communication across large distances is virtually impossible in the Super Dimension Fortress Macross universe; it is actually a plot point in Macross Frontier, where even relay buoys must contend with "fold interference" that delay or disable communication entirely. However, the Protoculture and the Vajra have their ways around that (see above.)

Film

Dune.
Alien and its sequels. The Nostromo and other ships are out of contact while on the frontier, and are thus on the spot, for taking on the terrors that wait on whatever God forsaken planet the crew finds themselves on.

Live Action TV

Notable in its absence in Andromeda, where communication over interstellar distances requires a living courier.
The 2000s Battlestar Galactica apparently relies solely on FM radio (referred to in-story simply as "wireless") for ship-to-ship communication, and faster-than-light comm does not exist; ships on recon missions must be provided with rendezvous points before departure lest they never be able to find the fleet again.

Tabletop Games

Traveller, where all interstellar messages have to be delivered by courier (although those can still jump). This has a natural impact on the way the universe works.
The Battletech universe has Hyper Pulse Generators, which send messages between star systems instantaneously. It's been stated in canon that sending a message via HPG can often take anywhere from a few days to weeks, but that is mainly because the cost of transmission is so high, the operators will wait for a large number of messages to be sent at once.
- Just don't mention the TV series, which had a realtime video conference using said HP Gs.

Video Games

Halo. All messages are carried on ships that travel between planets. Described as the futurisitc Pony Express.
- This is more a UNSC problem though as the Forerunner definitely had FTL communications (it's unclear if the Covenant have this technology or not.) Some scenes also suggest that the UNSC has at least "short" range FTL sensors as for instance they seem able to detect ships incoming at FTL speed somehow. It's also notable that their never seems to be any delay in communications even over large distances inside systems.

Web Comics

In Freefall, it's specifically said that the only way to communicate between star systems is by sending messages via ship. As most interstellar travel is via sublight vessels (FTL travel being quite expensive, and possibly dangerous going by the drive's name: Dangerous And Very Expensive [or DAVE] drive), this means that a message and its response could take up to many months, as the ship carrying it travels on its normal route.

Aversions Without FTL Travel

Anime and Manga

Planetes features a phone on a lunar colony with a Windows-esque progress bar on a video screen that gives the delay between messages between the Moon and Earth (about a second and a half)
Stellvia Of The Universe has this as a plot point. Videomail between Foundations travels slower than light, so it takes hours for the messages from Shima and Rinna to reach each other.

Literature

2001: A Space Odyssey, in which an interview with astronauts on their way to Jupiter has to be edited together to remove the long delay times in the conversation.
Greg Egan's Schilds Ladder features a universe with neither ftl communication nor travel. Being written by Greg Egan, most interstellar travel is done by transmitting your mind, with only a few "anachronauts" crawling around in starships to investigate the future they find along the way; either way all travellers are doomed to miss decades of time. One planet solves the problem by putting the entire population into what amounts to slow-motion until the traveler returns.
One of the entries in the X Wing Series has the squadron tapping in on a pirate conversation. They figure out how far apart the two conversing parties are by the length of the pauses, and by doing so, pinpoint their locations.

Video Games

Usually, the Metroid games avoid this by having no form of communication through space, but in Metroid Prime: Hunters, it's stated that a signal was sent to various bounty hunters via a telepathic frequency.

Real Life