An ansible is a category of fictional devices or technology capable of near-instantaneous or faster-than-light 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. A related term is ultrawave.
Faster-than-light travel and communication are the conjectural propagation of matter or information faster than the speed of light. The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light, and that nothing may travel faster.
The fictional technology in Star Trek has borrowed many ideas from the scientific world. Episodes often contain technologies named after or inspired by real-world scientific concepts, such as tachyon beams, baryon sweeps, quantum slipstream drives, and photon torpedoes. Some of the technologies created for the Star Trek universe were done so out of financial necessity. For instance, the transporter was created because the limited budget of Star Trek: The Original Series (TOS) in the 1960s did not allow expensive shots of spaceships landing on planets.
Quantum entanglement is the phenomenon of a group of particles being generated, interacting, or sharing spatial proximity in such a way that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics: entanglement is a primary feature of quantum mechanics not present in classical mechanics.
A tachyon or tachyonic particle is a hypothetical particle that always travels faster than light. Physicists believe that faster-than-light particles cannot exist because they are inconsistent with the known laws of physics. If such particles did exist they could be used to send signals faster than light and into the past. According to the theory of relativity this would violate causality, leading to logical paradoxes such as the grandfather paradox. Tachyons would exhibit the unusual property of increasing in speed as their energy decreases, and would require infinite energy to slow to the speed of light. No verifiable experimental evidence for the existence of such particles has been found.
The Hainish Cycle consists of a number of science fiction novels and stories by Ursula K. Le Guin. It is set in a future history in which civilizations of human beings on planets orbiting a number of nearby stars, including Terra ("Earth"), are contacting each other for the first time and establishing diplomatic relations, and setting up a confederacy under the guidance of the oldest of the human worlds, peaceful Hain. In this history, human beings did not evolve on Earth but were the result of interstellar colonies planted by Hain long ago, which was followed by a long period when interstellar travel ceased. Some of the races have new genetic traits, a result of ancient Hainish experiments in genetic engineering, including people who can dream while awake, and a world of hermaphroditic people who only come into active sexuality once a month, not knowing which sex will manifest in them. In keeping with Le Guin's style, she uses varied social and environmental settings to explore the anthropological and sociological outcomes of human evolution in those diverse environments.
The Alcubierre drive is a speculative warp drive idea according to which a spacecraft could achieve apparent faster-than-light travel by contracting space in front of it and expanding space behind it, under the assumption that a configurable energy-density field lower than that of vacuum could be created. Proposed by theoretical physicist Miguel Alcubierre in 1994, the Alcubierre drive is based on a solution of Einstein's field equations. Since those solutions are metric tensors, the Alcubierre drive is also referred to as Alcubierre metric.
A warp drive or a drive enabling space warp is a fictional superluminal spacecraft propulsion system in many science fiction works, most notably Star Trek, and a subject of ongoing physics research. The general concept of "warp drive" was introduced by John W. Campbell in his 1957 novel Islands of Space and was popularized by the Star Trek series. Its closest real-life equivalent is the Alcubierre drive, a theoretical solution of the field equations of general relativity.
There are several proposed types of exotic matter:
In physics, the principle of locality states that an object is influenced directly only by its immediate surroundings. A theory that includes the principle of locality is said to be a "local theory". This is an alternative to the concept of instantaneous, or "non-local" action at a distance. Locality evolved out of the field theories of classical physics. The idea is that for a cause at one point to have an effect at another point, something in the space between those points must mediate the action. To exert an influence, something, such as a wave or particle, must travel through the space between the two points, carrying the influence.
In quantum information science, the Bell's states or EPR pairs are specific quantum states of two qubits that represent the simplest examples of quantum entanglement. The Bell's states are a form of entangled and normalized basis vectors. This normalization implies that the overall probability of the particle being in one of the mentioned states is 1: . Entanglement is a basis-independent result of superposition. Due to this superposition, measurement of the qubit will "collapse" it into one of its basis states with a given probability. Because of the entanglement, measurement of one qubit will "collapse" the other qubit to a state whose measurement will yield one of two possible values, where the value depends on which Bell's state the two qubits are in initially. Bell's states can be generalized to certain quantum states of multi-qubit systems, such as the GHZ state for three or more subsystems.
A Krasnikov tube is a speculative mechanism for space travel involving the warping of spacetime into permanent superluminal tunnels. The resulting structure is analogous to a wormhole or an immobile Alcubierre drive with the endpoints displaced in time as well as space. The idea was proposed by Sergey Krasnikov in 1995.
In physics, the no-communication theorem or no-signaling principle is a no-go theorem from quantum information theory which states that, during measurement of an entangled quantum state, it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer. The theorem is important because, in quantum mechanics, quantum entanglement is an effect by which certain widely separated events can be correlated in ways that, at first glance, suggest the possibility of communication faster-than-light. The no-communication theorem gives conditions under which such transfer of information between two observers is impossible. These results can be applied to understand the so-called paradoxes in quantum mechanics, such as the EPR paradox, or violations of local realism obtained in tests of Bell's theorem. In these experiments, the no-communication theorem shows that failure of local realism does not lead to what could be referred to as "spooky communication at a distance".
The Quincunx of Time is a short science fiction novel by American writer James Blish. It is an extended version of a short story entitled "Beep", published by Galaxy Science Fiction magazine in 1954. The novel form was first published in 1973.
The hypothetical particles tachyons, defined through being faster than light, have inspired many occurrences in fiction. In general, tachyons are a standby mechanism upon which many science fiction authors rely to establish faster-than-light communication, with or without reference to causality issues, as well as a means to achieve faster-than-light travel. Science writer Sidney Perkowitz commented "that the very word "tachyon," because of its unusual Greek-origin spelling and engagingly catchy hard "ch" sound, lends a certain "science-ness" or "science coolness to fiction." Starting in the 1970s, tachyons were used in science-fiction to present a seemingly-plausible explanation for time travel and communication through time. Peter Nicholls, in The Encyclopedia of Science Fiction, describes Gregory Benford's Timescape (1980) as the first work to use tachyons to this effect "with some care", where scientists send a message to the past trying to change history. Glen Cook's 1985 novel A Matter of Time features a much less stringently described "tachyon generator" to "transmit [both to the past and] to the far future". Uses of the concept for space travel appeared in association with "the Asgard, the benevolent alien race in the Stargate SG-1 television series (1997–2007)", and in the 2001 film K-Pax, which coined the term "tachyonic speeds" for "multiples of light speed". An "unabashed" use appeared already in 1969, where "Bob Shaw's The Palace of Eternity features such delights as a million-ton tachyonic spaceship travelling at 30,000 times the speed of light." In the Star Trek franchise, in addition to facilitating faster-than-light travel, tachyons have been mentioned "for varied purposes, including cloaking a spacecraft, detection" of such cloaking and overcoming defensive shields, which has been regarded as "technobabble" by Mashable contributor Keith Wagstaff: dialogue that implies a scientific explanation, using a term with a real scientific concept behind it, "but really doesn't mean much."
In quantum physics, coincidence counting is used in experiments testing particle non-locality and quantum entanglement. In these experiments two or more particles are created from the same initial packet of energy, inexorably linking/entangling their physical properties. Separate particle detectors measure the quantum states of each particle and send the resulting signal to a coincidence counter. In any experiment studying entanglement, the entangled particles are vastly outnumbered by non-entangled particles which are also detected; patternless noise that drowns out the entangled signal. In a two detector system, a coincidence counter alleviates this problem by only recording detection signals that strike both detectors simultaneously. This ensures that the data represents only entangled particles.
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 presented a thought experiment of how faster-than-light signals can lead to a paradox of causality, which was described by Einstein and Arnold Sommerfeld in 1910 as a means "to telegraph into the past". The same thought experiment was described by Richard Chace Tolman in 1917; thus, it is also known as Tolman's paradox.
In physics, a tachyonic field, or simply tachyon, is a quantum field with an imaginary mass. Although tachyonic particles are a purely hypothetical concept that violate a number of essential physical principles, at least one field with imaginary mass, the Higgs field, is believed to exist. Under no circumstances do any excitations of tachyonic fields ever propagate faster than light—the presence or absence of a tachyonic (imaginary) mass has no effect on the maximum velocity of signals, and so unlike faster-than-light particles there is no violation of causality. Tachyonic fields play an important role in physics and are discussed in popular books.
ER = EPR is a conjecture in physics stating that two entangled particles are connected by a wormhole and is thought by some to be a basis for unifying general relativity and quantum mechanics into a theory of everything.
Relativistic quantum cryptography is a sub-field of quantum cryptography, in which in addition to exploiting the principles of quantum physics, the no-superluminal signalling principle of relativity theory stating that information cannot travel faster than light is exploited too. Technically speaking, relativistic quantum cryptography is a sub-field of relativistic cryptography, in which cryptographic protocols exploit the no-superluminal signalling principle, independently of whether quantum properties are used or not. However, in practice, the term relativistic quantum cryptography is used for relativistic cryptography too.
