who discovered that light is faster than sound
Abū Rayhān al - Bīrūnī
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to propose that light must have a finite speed, and that the speed of light is variable, decreasing in denser bodies. He argued that light is substantial matter, the propagation of which requires time, even if this is hidden from our senses. Also in the 11th century, Abū Rayhān al-Bīrūnī agreed that light has a finite speed, and observed that the speed of light is much faster than the speed of sound. In the 13th century, Roger Bacon argued that the speed of light in air was not infinite, using philosophical arguments backed by the writing of Alhazen and Aristotle.
Speed of light
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great influence on the later developments of optics. Avicenna (980-1037) agreed with Alhazen that the speed of light is finite, as he "observed that if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite." Abū Rayhān al-Bīrūnī (973-1048) also agreed that light has a finite speed, and stated that the speed of light is much faster than the speed of sound. Abu 'Abd Allah Muhammad ibn Ma'udh, who lived in Al-Andalus during the second half of the 11th century, wrote a work on optics
History of optics
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to propose that light must have a finite speed, and that the speed of light is variable, decreasing in denser bodies. He argued that light is substantial matter, the propagation of which requires time, even if this is hidden from our senses. Also in the 11th century, Abū Rayhān al-Bīrūnī agreed that light has a finite speed, and observed that the speed of light is much faster than the speed of sound. In the 13th century, Roger Bacon argued that the speed of light in air was not infinite, using philosophical arguments backed by the writing of Alhazen and Aristotle.
Speed of light
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an explanation for them." Faster-than-light neutrino anomaly In 2011, the OPERA experiment mistakenly observed neutrinos appearing to travel faster than light. Even before the mistake was discovered, the result was considered anomalous because speeds higher than that of light in a vacuum are generally thought to violate special relativity, a cornerstone of the modern understanding of physics for over a century. OPERA scientists announced the results of the experiment in with the stated intent of promoting further inquiry and debate. Later the team reported two flaws in their equipment set-up that had caused errors far outside their original confidence interval:
Faster-than-light neutrino anomaly
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Faster-than-light neutrino anomaly In 2011, the OPERA experiment mistakenly observed neutrinos appearing to travel faster than light. Even before the mistake was discovered, the result was considered anomalous because speeds higher than that of light in a vacuum are generally thought to violate special relativity, a cornerstone of the modern understanding of physics for over a century. OPERA scientists announced the results of the experiment in with the stated intent of promoting further inquiry and debate. Later the team reported two flaws in their equipment set-up that had caused errors far outside their original confidence interval: a fiber optic cable
Faster-than-light neutrino anomaly
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to the material density. Given that all other things being equal (ceteris paribus), sound will travel slower in spongy materials, and faster in stiffer ones. Effects like dispersion and reflection can also be understood using this model. For instance, sound will travel 1.59 times faster in nickel than in bronze, due to the greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen (protium) gas than in heavy hydrogen (deuterium) gas, since deuterium has similar properties but twice the density. At the same time, "compression-type" sound will travel faster in solids
Speed of sound
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book "Opticks", Isaac Newton reported Rømer's calculations of the finite speed of light and gave a value of "seven or eight minutes" for the time taken for light to travel from the Sun to the Earth (the modern value is 8 minutes 19 seconds). Newton queried whether Rømer's eclipse shadows were coloured; hearing that they were not, he concluded the different colours travelled at the same speed. In 1729, James Bradley discovered stellar aberration. From this effect he determined that light must travel 10,210 times faster than the Earth in its orbit (the modern figure is 10,066 times faster) or,
Speed of light
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atop other gameplay mechanics to create a highly-replayable experience. The game's soundtrack was nominated for IGN's Best Overall Music and Best PC Sound of 2012. It was recognized as being among Kotaku's Best Video Game Music of 2012, one of the Top Ten Video Game Soundtracks of 2012 on The Game Scouts, and one of "Complex" magazine's 25 Best Video Game Soundtracks on Bandcamp. FTL: Faster Than Light FTL: Faster Than Light is a space-based top-down real-time strategy roguelike game created by indie developer Subset Games, which was released for Microsoft Windows, OS X and Linux in September 2012. In
FTL: Faster Than Light
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preserved, one of the consequences of special relativity is that no information signal or material object can travel faster than light in vacuum. This is not to say that "all" faster than light speeds are impossible. Various trivial situations can be described where some "things" move faster than light. For example, the location where the beam of a search light hits the bottom of a cloud can move faster than light when the search light is turned rapidly. In 1850, Hippolyte Fizeau and Léon Foucault independently established that light travels more slowly in water than in air, thus validating a
Special relativity
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Faster-than-light communication Superluminal communication is a hypothetical process in which information is sent at faster-than-light (FTL) speeds. The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment. Under present knowledge superluminal communication is impossible because, in a Lorentz-invariant theory, it could be used to transmit information into the past. This contradicts causality and leads to logical paradoxes. A number of theories and phenomena related to superluminal communication have been proposed or studied, including tachyons, quantum nonlocality, and wormholes. Tachyonic particles are hypothetical particles that travel faster than light.
Faster-than-light communication
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the fine structure constant is fixed, the observational claim is that the speed of light is time-dependent. Faster-than-light Faster-than-light (also superluminal or FTL) communication and travel are the conjectural propagation of information or matter 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. Tachyons, particles whose speed exceeds that of light, have been hypothesized, but their existence would violate causality, and the consensus of physicists is that they cannot exist. On the other hand, what some physicists refer to as "apparent" or "effective"
Faster-than-light
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Cherenkov detector A Cherenkov detector (pronunciation: /tʃɛrɛnˈkɔv/; Russian: Черенко́в) is a particle detector using the speed threshold for light production, the speed-dependent light output or the velocity-dependent light direction of Cherenkov radiation. A particle passing through a material at a velocity greater than that at which light can travel through the material emits light. This is similar to the production of a sonic boom when an airplane is traveling through the air faster than sound waves can move through the air. The direction this light is emitted is on a cone with angle θ about the direction in which the
Cherenkov detector
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to fly with test pilots as he produced a 300-page notebook that he turned over to dramatist Terence Rattigan. The subsequent screenplay concentrated on the newly discovered problems of flying at supersonic speeds and is also loosely based on the real-life story of aircraft designer Geoffrey de Havilland and the loss of his son. Geoffrey de Havilland, Jr. was the de Havilland company test pilot who died on 27 September 1946 attempting to fly faster than the speed of sound in the DH 108. John Derry, another de Havilland test pilot, has been called "Britain's first supersonic pilot," because of
The Sound Barrier
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looking for a new challenge which will change the status quo and he thinks he has found it in a far off planet. On that world researchers who have been studying the native fauna believe they have discovered a kangaroo like animal which is able to teleport. Intrigued by the revolutionary possibilities of faster than light travel, Falkner and his colleagues travel to the planet to study the animals. What they discover is that it is not the animals themselves who are teleporting. Rather they discover a race of disembodied extradimensional aliens. Some of these aliens, who possess powers of
Knight Moves (novel)
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light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves. Although Descartes was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media. Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes' theory of light is regarded as the start
Light
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Faster-than-light Faster-than-light (also superluminal or FTL) communication and travel are the conjectural propagation of information or matter 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. Tachyons, particles whose speed exceeds that of light, have been hypothesized, but their existence would violate causality, and the consensus of physicists is that they cannot exist. On the other hand, what some physicists refer to as "apparent" or "effective" FTL depends on the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant
Faster-than-light
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sound We're faster than evil, we're faster than crime We're faster than light, we're faster than time The Ring Raiders toyline consisted primarily of small (3–4 centimeters long) plastic toy planes mounted on plastic rings via a detachable display stand. The stands allowed the aircraft a small degree of mobility. Relatively few molds were produced for the toyline; most of the aircraft were repainted three or four times each. The line was rather short lived, lasting about six months. The bulk of the toy release consisted of packs of four aircraft, each squadron sporting their own distinctive color scheme. No
Ring Raiders
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for the launcher configuration. The primary use of the range facilities at Arnold Air Force Base is the measurement of released kinetic energy upon projectile impact. The muzzle velocity of an airgun, firearm, or light-gas gun is limited by, but not limited to, the speed of sound in the working fluid—the air, burning gunpowder, or a light gas. Up to the speed of sound, thermodynamics provides a simple, approximate calculation approach: the projectile is accelerated by the pressure difference between its ends, and since such a pressure wave cannot propagate any faster than the speed of sound in the medium,
Light-gas gun
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protons that have been unfolded from eleven space dimensions to two dimensions, programmed, and then refolded" and thus Sophons remain undetectable for humans. In Howard Taylor's web comic series Schlock Mercenary, superluminal communication is performed via the hypernet, a galaxy-spanning analogue to the internet. Through the hypernet, communications and data are routed through nanoscopic wormholes, using conventional electromagnetic signals. Faster-than-light communication Superluminal communication is a hypothetical process in which information is sent at faster-than-light (FTL) speeds. The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment. Under present
Faster-than-light communication
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a plane at low altitude but not seeing it. Then he heard "a loud sound followed by a bright flash of light on the horizon, then another dull sound and a less intense flash of light on the horizon" as well as smelling aviation fuel. Brun maintains that the fisherman's account of the destruction of KAL 007 was not sustainable because if the aircraft exploded while low on the horizon, the sound of the explosion could not have, as reported by the fishermen, reached his ear before the flash of the explosion reached the eye, as light travels faster than
Korean Air Lines Flight 007 alternative theories
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OPERA collaboration garnered international attention when they released a preprint reporting the Faster-than-light neutrino anomaly, wherein neutrinos were measured to be travelling, on average, at faster-than-light speed. On 24 February 2012, the team said they had discovered two problems with their previous test, muddying the validity of the previous result. The preprint has been modified to account for these facts, and indeed the measurement of the neutrino speed, there reported, agrees with the velocity of the light. CERN Neutrinos to Gran Sasso The CERN Neutrinos to Gran Sasso (CNGS) project was a physics project of the European Organization for Nuclear
CERN Neutrinos to Gran Sasso
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Another apparent contradiction lies in the fact that the group velocity in anomalously dispersive media is higher than the speed of light. This was investigated by Arnold Sommerfeld (1907, 1914) and Léon Brillouin (1914). They came to the conclusion that in such cases the signal velocity is not equal to the group velocity, but to the front velocity which is never faster than the speed of light. Similarly, it is also argued that the apparent superluminal effects discovered by Günter Nimtz can be explained by a thorough consideration of the velocities involved. Also quantum entanglement (denoted by Einstein as "spooky
Criticism of the theory of relativity
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however, the density of the center is predicted to be greater. If they exist, the eigenmode frequency for radial oscillations of a preon star will be 10 greater than that of a neutron star. As the radius will be roughly 10 smaller than the radius of a neutron star, if sound travels through preons at the same speed it does neutrons, then the frequency will be increased by 10, giving GHz frequencies. If sound travels faster in preons than it does neutrons, the frequency cannot exceed formula_6 even if the speed of light is approached. The existence of preons could
Preon star
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Tachyon A tachyon () or tachyonic particle is a hypothetical particle that always travels faster than light. Most physicists believe that faster-than-light particles cannot exist because they are not consistent with the known laws of physics. If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality. No experimental evidence for the existence of such particles has been found. The possibility of particles moving faster-than-light was first proposed by O. M. P. Bilaniuk, V. K. Deshpande, and E. C. G.
Tachyon
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at speeds faster than light with respect to the contents of the warp bubble; that is, a light beam within the warp bubble would still always move faster than the ship. Because objects within the bubble are not moving (locally) faster than light, the mathematical formulation of the Alcubierre metric is consistent with the conventional claims of the laws of relativity (namely, that an object with mass cannot attain or exceed the speed of light) and conventional relativistic effects such as time dilation would not apply as they would with conventional motion at near-light speeds. The Alcubierre drive, however, remains
Alcubierre drive
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phase velocity or group velocity faster than the vacuum velocity of light. However, as stated above, a superluminal phase velocity cannot be used for faster-than-light transmission of information. The Hartman effect is the tunneling effect through a barrier where the tunneling time tends to a constant for large barriers. This could, for instance, be the gap between two prisms. When the prisms are in contact, the light passes straight through, but when there is a gap, the light is refracted. There is a non-zero probability that the photon will tunnel across the gap rather than follow the refracted path. For
Faster-than-light
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Hartman effect The delay time for a quantum tunneling particle is independent of the thickness of the opaque barrier. This is called the Hartman effect, after Thomas Hartman who discovered it in 1962. In 2007, Nimtz and Stahlhofen demonstrated that quantum tunneling of "evanescent modes" across a gap might result in virtual particles traveling faster than light. The Hartman effect is the tunnelling effect through a barrier where the tunnelling time tends to a constant for large barriers. This was first described by Thomas E. Hartman in 1962. The Hartman effect was demonstrated with evanescent microwaves by Achim Enders and
Hartman effect
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time running out before his body is discovered, she signs up with the ship "Loki", a barely legitimate 'spook' that survives by gathering intelligence and selling it. "Loki" is not a typical merchanter ship; instead of a close-knit family, the crew consists of unrelated hire-ons. As a result, various competing cliques have formed aboard and Bet has to navigate her way among them. She becomes friends with Musa, a universally respected crewman who claims to have served on one of the ancient sublighters, the original nine vessels that predated faster-than-light ships. She is also strongly attracted to Ramey, an ex-merchanter
Rimrunners
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not. Basically this means that while physics should remain the same in non-accelerated experiments, light would not follow the same rules because it is travelling in the universal "aether frame". Some effect caused by this difference should be detectable. A simple example concerns the model on which aether was originally built: sound. The speed of propagation for mechanical waves, the speed of sound, is defined by the mechanical properties of the medium. Sound travels 4.3 times faster in water than in air. This explains why a person hearing an explosion underwater and quickly surfacing can hear it again as the
Luminiferous aether
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There he meets Gottwald and his wife, who are the last survivors of the people who came in the ship. Humans arose on a distant world, discovered faster-than-light space travel, carved an empire for themselves, and were then almost exterminated by the Enemy, a race of vicious monsters. So horrific are these creatures that they are part of human "racial memory", being the demons and dragons and other creatures out of nightmare. The ship is one of four sent as a last desperate measure. The human race had to start again. It needed a "transfusion" of new ideas and ways
Transfusion (short story)
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is absorbed quite quickly as well. Besides these universal qualities of water, different bodies of water may absorb light of different wavelengths because of salts and other chemicals in the water. Hearing is an important sensory system for most species of fish. Hearing threshold and the ability to localize sound sources are reduced underwater, in which the speed of sound is faster than in air. Underwater hearing is by bone conduction, and localization of sound appears to depend on differences in amplitude detected by bone conduction. Aquatic animals such as fish, however, have a more specialized hearing apparatus that is
Sensory systems in fish
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oscillating perpendicular to the propagation direction. Proponents claim this is necessary to explain polarised light, whereas opponents object to implications for the aether. Doppler doesn't choose sides, although the issue returns in § 6. § 2 Doppler observes that colour is a manifestation of the frequency of the light wave, in the eye of the beholder. He describes his principle that a frequency shift occurs when the source or the observer moves. A ship meets waves at a faster rate when sailing against the waves than when sailing along with them. The same goes for sound and light. § 3
Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels
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the other musicians, field conductors and listeners at slightly different times. If the distance between musicians is large enough, listeners may perceive waves to be . Typically, in this case, listeners perceive that one section of the band is playing their parts slightly after another section. This "delay" effect is informally referred to as "ensemble tear" or "phasing" (not to be confused with the music composition technique of the same name). Consider also that viewers perceive the movement of marchers as light waves. Since light travels faster than sound, viewers may perceive that movement is out of phase with the
Marching band
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Light echo A light echo is a physical phenomenon caused by light reflected off surfaces distant from the source, and arriving at the observer with a delay relative to this distance. The phenomenon is analogous to an echo of sound, but due to the much faster speed of light, it mostly only manifests itself over astronomical distances. For example, a light echo is produced when a sudden flash from a nova is reflected off a cosmic dust cloud, and arrives at the viewer after a longer duration than it otherwise would have taken with a direct path. Because of their
Light echo
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oscillator ticking too fast. In special relativity, it is impossible to accelerate an object the speed of light, or for a massive object to move the speed of light. However, it might be possible for an object to exist which moves faster than light. The hypothetical elementary particles with this property are called tachyonic particles. Attempts to quantize them failed to produce faster-than-light particles, and instead illustrated that their presence leads to an instability. Various theorists have suggested that the neutrino might have a tachyonic nature, while others have disputed the possibility. Mechanical equations to describe hypothetical exotic matter which
Faster-than-light
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moving faster than light to A. At A, it is received by another observer, moving so as to be in the system, who sends it back, again faster than light, arriving at B. But B is in the past relative to O. The absurdity of this process becomes obvious when both observers subsequently confirm that they received no message at all, but all messages were directed towards the other observer as can be seen graphically in the Minkowski diagram. Furthermore, if it were possible to accelerate an observer to the speed of light, their space and time axes would coincide
Minkowski diagram
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times the distance of previous experiments. Another successful experiment was conducted at the University of Bristol, which revealed that sound could be manipulated to produce possible future tractor beams, rivaling light. This could be done using a precisely timed sequence of sound waves, produced by tiny loudspeakers, creating a limited space with low pressure that can counteract gravity and levitate objects. In "Star Wars", a subspace transceiver, also known as a subspace comm, subspace radio, and hypertransceiver, was a standard device used for instantaneous, faster-than-light communications between nearby systems. Similar to its shorter-ranged cousin, the comlink, the subspace transceiver relied
Technology in Star Wars
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travel faster than the speed of light, but that given other circumstances it could have been possible to do so. Using the accessibility relation we can translate this scenario as follows: At all of the worlds accessible to our own world, it is not the case that humans can travel faster than the speed of light, but at one of these accessible worlds there is "another" world accessible from "those" worlds but not accessible from our own at which humans can travel faster than the speed of light. It should also be noted that the definition of □ makes vacuously
Modal logic
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has also been shown in experiment. It should even be possible for the group velocity to become infinite or negative, with pulses travelling instantaneously or backwards in time. None of these options, however, allow information to be transmitted faster than "c". It is impossible to transmit information with a light pulse any faster than the speed of the earliest part of the pulse (the front velocity). It can be shown that this is (under certain assumptions) always equal to "c". It is possible for a particle to travel through a medium faster than the phase velocity of light in that
Speed of light
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the underlying behavior does not violate local causality or allow FTL communication, it follows that neither does the additional effect of wavefunction collapse, whether real "or" apparent. The uncertainty principle implies that individual photons may travel for short distances at speeds somewhat faster (or slower) than "c", even in a vacuum; this possibility must be taken into account when enumerating Feynman diagrams for a particle interaction. However, it was shown in 2011 that a single photon may not travel faster than "c". In quantum mechanics, virtual particles may travel faster than light, and this phenomenon is related to the fact
Faster-than-light
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than in liquids, and faster in liquids than in gases, because the solids are more difficult to compress than liquids, while liquids in turn are more difficult to compress than gases. Some textbooks mistakenly state that the speed of sound increases with density. This notion is illustrated by presenting data for three materials, such as air, water and steel, which also have vastly different compressibility, more which making up for the density differences. An illustrative example of the two effects is that sound travels only 4.3 times faster in water than air, despite enormous differences in compressibility of the two
Speed of sound
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Feynman propagators in momentum space are: For purposes of Feynman diagram calculations, it is usually convenient to write these with an additional overall factor of (conventions vary). The Feynman propagator has some properties that seem baffling at first. In particular, unlike the commutator, the propagator is "nonzero" outside of the light cone, though it falls off rapidly for spacelike intervals. Interpreted as an amplitude for particle motion, this translates to the virtual particle travelling faster than light. It is not immediately obvious how this can be reconciled with causality: can we use faster-than-light virtual particles to send faster-than-light messages? The
Propagator
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relativistic causality violation (which would be implied by transmitting information faster than light). He also argues that "Nothing was observed to be traveling faster than light. The measured delay is the lifetime of stored energy leaking out of both sides of the barrier. The equality of transmission and reflection delays is what one expects for energy leaking out of both sides of a symmetric barrier." Aephraim M. Steinberg of the University of Toronto has also stated that Nimtz has not demonstrated causality violation (which would be implied by transmitting information faster than light). Steinberg also uses a classical argument. In
Günter Nimtz
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"acoustic laser" or "sound laser". SASERs could have wide applications. Apart from facilitating the investigation of terahertz-frequency ultrasound, the SASER is also likely to find uses in optoelectronics (electronic devices that detect and control light—as a method of transmitting a signal from an end to the other of, for instance, fiber optics), as a method of signal modulation and/or transmission. Such devices could be high precision measurement instruments and they could lead to high energy focused sound. Using SASERs to manipulate electrons inside semiconductors could theoretically result in terahertz-frequency computer processors, much faster than the current chips. This concept can
Sound amplification by stimulated emission of radiation
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these are currently traveling away from us at speeds greater than the speed of light. Because the Hubble parameter is decreasing with time, there can actually be cases where a galaxy that is receding from us faster than light does manage to emit a signal which reaches us eventually. However, because the expansion of the universe is accelerating, it is projected that most galaxies will eventually cross a type of cosmological event horizon where any light they emit past that point will never be able to reach us at any time in the infinite future, because the light never reaches
Faster-than-light
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Tachyonic field A tachyonic field, or simply tachyon, is a field with an imaginary mass. Although tachyonic particles (particles that move faster than light) are a purely hypothetical concept that violate a number of essential physical principles, at least one field with imaginary mass is believed to exist. In general, tachyonic fields play an important role in physics and are discussed in popular books. 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
Tachyonic field
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faster-than-light relative speed only applies locally. Wormholes might allow effective superluminal (faster-than-light) travel by ensuring that the speed of light is not exceeded locally at any time. While traveling through a wormhole, subluminal (slower-than-light) speeds are used. If two points are connected by a wormhole whose length is shorter than the distance between them "outside" the wormhole, the time taken to traverse it could be less than the time it would take a light beam to make the journey if it took a path through the space "outside" the wormhole. However, a light beam traveling through the same wormhole would
Wormhole
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(and return to their starting location) faster than light traveling outside the wormhole. Gerald Cleaver and Richard Obousy, a professor and student of Baylor University, theorized that manipulating the extra spatial dimensions of string theory around a spaceship with an extremely large amount of energy would create a "bubble" that could cause the ship to travel faster than the speed of light. To create this bubble, the physicists believe manipulating the 10th spatial dimension would alter the dark energy in three large spatial dimensions: height, width and length. Cleaver said positive dark energy is currently responsible for speeding up the
Faster-than-light
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does not represent a speed measured in a single inertial frame. A light signal that left the Earth at the same time as the traveller would always get to the destination before the traveller. Since one might not travel faster than light, one might conclude that a human can never travel further from the Earth than 40 light-years if the traveler is active between the age of 20 and 60. A traveler would then never be able to reach more than the very few star systems which exist within the limit of 20–40 light-years from the Earth. This is a
Faster-than-light
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be altered in certain cases. When vacuum energy is lowered, light itself has been predicted to go faster than the standard value "c". This is known as the Scharnhorst effect. Such a vacuum can be produced by bringing two perfectly smooth metal plates together at near atomic diameter spacing. It is called a Casimir vacuum. Calculations imply that light will go faster in such a vacuum by a minuscule amount: a photon traveling between two plates that are 1 micrometer apart would increase the photon's speed by only about one part in 10. Accordingly, there has as yet been no
Faster-than-light
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Yukawa coupling to give them mass, as well. Mathematically, the Higgs field has imaginary mass and is therefore a tachyonic field. While tachyons (particles that move faster than light) are a purely hypothetical concept, fields with imaginary mass have come to play an important role in modern physics. Under no circumstances do any excitations ever propagate faster than light in such theories — the presence or absence of a tachyonic mass has no effect whatsoever on the maximum velocity of signals (there is no violation of causality). Instead of faster-than-light particles, the imaginary mass creates an instability: Any configuration in
Higgs boson
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to expand in such a way that they have a "recession velocity" which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light-years from us today have a recession velocity which is faster than light. Miguel Alcubierre theorized that it would be possible to create a warp drive, in which a ship would be enclosed in a "warp bubble" where the space at the front of the bubble is rapidly contracting and the space at the back is rapidly expanding, with the result that the bubble can
Faster-than-light
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Meteorites entering the Earth's atmosphere usually, if not always, descend faster than sound. The tip of the propeller on many early aircraft may reach supersonic speeds, producing a noticeable buzz that differentiates such aircraft. This is undesirable, as the transonic air movement creates disruptive shock waves and turbulence. It is due to these effects that propellers are known to suffer from dramatically decreased performance as they approach the speed of sound. It is easy to demonstrate that the power needed to improve performance is so great that the weight of the required engine grows faster than the power output of
Sound barrier
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reach a distant destination much faster than a light beam moving outside the bubble, but without objects inside the bubble locally traveling faster than light. However, several objections raised against the Alcubierre drive appear to rule out the possibility of actually using it in any practical fashion. Another possibility predicted by general relativity is the traversable wormhole, which could create a shortcut between arbitrarily distant points in space. As with the Alcubierre drive, travelers moving through the wormhole would not "locally" move faster than light travelling through the wormhole alongside them, but they would be able to reach their destination
Faster-than-light
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time machine, and thus would require a theory of quantum gravity to fully analyze. Other authors argue that Scharnhorst's original analysis, which seemed to show the possibility of faster-than-"c" signals, involved approximations which may be incorrect, so that it is not clear whether this effect could actually increase signal speed at all. The physicists Günter Nimtz and Alfons Stahlhofen, of the University of Cologne, claim to have violated relativity experimentally by transmitting photons faster than the speed of light. They say they have conducted an experiment in which microwave photons — relatively low-energy packets of light — travelled "instantaneously" between
Faster-than-light
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can see polarized light. Amongst jawless fish, the lamprey has well-developed eyes, while the hagfish has only primitive eyespots. Fish vision shows adaptation to their visual environment, for example deep sea fishes have eyes suited to the dark environment. Hearing is an important sensory system for most species of fish. Hearing threshold and the ability to localize sound sources are reduced underwater, in which the speed of sound is faster than in air. Underwater hearing is by bone conduction, and localization of sound appears to depend on differences in amplitude detected by bone conduction. Aquatic animals such as fish, however,
Fish physiology
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tests were necessary to definitely confirm or refute the results. In a analysis of their data, scientists of the OPERA collaboration reported evidence that neutrinos they produced at CERN in Geneva and recorded at the OPERA detector at Gran Sasso, Italy, had traveled faster than light. The neutrinos were calculated to have arrived approximately 60.7 nanoseconds (60.7 billionths of a second) sooner than light would have if traversing the same distance in a vacuum. After six months of cross checking, on , the researchers announced that neutrinos had been observed traveling at faster-than-light speed. Similar results were obtained using higher-energy
Faster-than-light neutrino anomaly
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be treated as flat and unchanging, it does not apply to situations where spacetime curvature or evolution in time become important. These situations are described by general relativity, which allows the separation between two distant objects to increase faster than the speed of light, although the definition of "separation" is different from that used in an inertial frame. This can be seen when observing distant galaxies more than the Hubble radius away from us (approximately 4.5 gigaparsecs or 14.7 billion light-years); these galaxies have a recession speed that is faster than the speed of light. Light that is emitted today
Expansion of the universe
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definition of the meter) or about 186,282.397 miles per second. This is not quite the same as traveling faster than light, since: Neither of these phenomena violates special relativity or creates problems with causality, and thus neither qualifies as "FTL" as described here. In the following examples, certain influences may appear to travel faster than light, but they do not convey energy or information faster than light, so they do not violate special relativity. For an earth-bound observer, objects in the sky complete one revolution around the Earth in one day. Proxima Centauri, the nearest star outside the solar system,
Faster-than-light
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therefore increase in speed as it travels, as described above. If the tachyon interacts with any other particles, it can also radiate Cherenkov energy into those particles. Neutrinos interact with the other particles of the Standard Model, and Andrew Cohen and Sheldon Glashow recently used this to argue that the faster-than-light neutrino anomaly cannot be explained by making neutrinos propagate faster than light, and must instead be due to an error in the experiment. Causality is a fundamental principle of physics. If tachyons can transmit information faster than light, then according to relativity they violate causality, leading to logical paradoxes
Tachyon
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siren is noise pollution reduction, since the siren will be heard only by those who need to hear it. Directional siren Directional siren refers to a siren with a bandwidth broader than 500 Hz-1.8 kHz that enables listeners to more quickly locate the source of the sound. Generally, sound localization accuracy is within 5 degrees, but enabling improved accuracy, for example in an ambulance siren, can lead to faster identification and response, thus enabling an ambulance to reach its destination faster and increase the chance of saving lives. Other benefits of directional sirens are reducing the potential health threat to
Directional siren
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that static field effects (which are mediated by virtual particles in quantum terms) may travel faster than light (see section on static fields above). However, macroscopically these fluctuations average out, so that photons do travel in straight lines over long (i.e., non-quantum) distances, and they do travel at the speed of light on average. Therefore, this does not imply the possibility of superluminal information transmission. There have been various reports in the popular press of experiments on faster-than-light transmission in optics — most often in the context of a kind of quantum tunnelling phenomenon. Usually, such reports deal with a
Faster-than-light
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Fallen Dragon Fallen Dragon is a science fiction novel by British writer Peter F. Hamilton. It was first published in 2001 by Macmillan. It follows the adventures of the mercenary Lawrence Newton as he attempts to capture what he believes is a fabulous treasure, only to find something of much greater importance. "Fallen Dragon" takes place during the 25th century. In the preceding centuries, a means of Faster-than-light (FTL) space travel was discovered, allowing a speed of one-half of a light-year per day. This led to a series of colonisation efforts in a globe about 70 light years around Earth,
Fallen Dragon
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to have a period that is decreasing at a rate faster than that observed in other binary systems, indicating the first identification of a candidate precursor for a red nova. When discovered, it had a light curve period of 0.458 days and was estimated to merge sometime in early 2022. Currently this is the only identified candidate, but it is likely that more will be found in the near future. The GAIA and LSST missions are expected to find millions more eclipsing binary system, potentially increasing the eclipsing binary database by two orders of magnitude. Recent estimates suggest that there
V1309 Scorpii
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wave can break the light barrier under certain conditions. General relativity was developed after special relativity to include concepts like gravity. It maintains the principle that no object can accelerate to the speed of light in the reference frame of any coincident observer. However, it permits distortions in spacetime that allow an object to move faster than light from the point of view of a distant observer. One such distortion is the Alcubierre drive, which can be thought of as producing a ripple in spacetime that carries an object along with it. Another possible system is the wormhole, which connects
Faster-than-light
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of time and velocity in different frames are no longer related simply by constant shifts, but are instead related by Poincaré transformations. These transformations have important implications: The speed of light is related to the vacuum permittivity "ε" and the vacuum permeability "μ". Therefore, not only the phase velocity, group velocity and energy flow velocity of electromagnetic waves but also the velocity of a photon can be faster than "c" in a special material has the constant permittivity or permeability whose value is less than that in vacuum. Special relativity postulate that the speed of light in vacuum is invariant
Faster-than-light
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in the material, creating a standing wave. Diffraction from the standing wave does not shift the frequency of the diffracted light. Acousto-optic modulators are much faster than typical mechanical devices such as tiltable mirrors. The time it takes an AOM to shift the exiting beam in is roughly limited to the transit time of the sound wave across the beam (typically 5 to 100 ns). This is fast enough to create active modelocking in an ultrafast laser. When faster control is necessary electro-optic modulators are used. However, these require very high voltages (e.g. 1...10 kV), whereas AOMs offer more deflection
Acousto-optic modulator
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Alcubierre drive The Alcubierre drive or Alcubierre warp drive (or Alcubierre metric, referring to metric tensor) is a speculative idea based on a solution of Einstein's field equations in general relativity as proposed by Mexican theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve apparent faster-than-light travel if a configurable energy-density field lower than that of vacuum (that is, negative mass) could be created. Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects
Alcubierre drive
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and satellites (often working with NASA or JPL scientists) – for who is out there to photograph them? They paint in oils, acrylics, gouache and markers, use pens, pastels or coloured pencils, or the latest digital technology. But these artists have an advantage over mere technology, for they can travel where machines cannot; and this includes into the past, the future and faster than light. A major activity of the IAAA is space art workshops, in most cases at remote locations with geology common to what has been discovered on other worlds. Iceland, Death Valley, Hawaii, The Colorado Plateau including
International Association of Astronomical Artists
198116
to fission propelled space-vehicles, avoiding the limitations of the Rocket equation. Scientists and authors have postulated a number of ways by which it might be possible to surpass the speed of light, but even the most serious-minded of these are highly speculative. It is also debatable whether faster-than-light travel is physically possible, in part because of causality concerns: travel faster than light may, under certain conditions, permit travel backwards in time within the context of special relativity. Proposed mechanisms for faster-than-light travel within the theory of general relativity require the existence of exotic matter and it is not known if
Interstellar travel
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songs like "Welcome To C.I.A.", "Bourbon and Soda", "Faster Than The Speed of Light", "Your Life Is My Death", "Hong Kong Falls". Ács spent about 10 years with the band and later determined the sound of the band with his unique bass playing style. On 29 November 2013, Amber Smith released their EP entitled "Another Way". The EP contains the title track and Merciful Sea written by Poniklo and Zubkov. The album was recorded at Supersize Studio and Echo Studio in Budapest and it was mixed by György Ligeti and mastered at Abnormal Studios in Pesterzsébet. Csaba Neményi, who played
Amber Smith (band)
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breach. In 1994, physicist Miguel Alcubierre formulated a theoretical solution, called the Alcubierre drive, for faster-than-light travel which models the warp drive concept. Calculations found that such a model would require prohibitive amounts of negative energy or mass. In 2018, the U.S. Defense Intelligence Agency made public a 2010 report that surveyed multiple different approaches to faster-than-light travel. One physicist who reviewed the report explained, that, while the theories were legitimate, they did not represent "something that's going to connect with engineering anytime soon, probably anytime ever." In 2012, NASA researcher Harold White hypothesized that by changing the shape of
Warp drive
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in a peer-reviewed journal to have observed single photons' precursors, saying that they travel no faster than "c" in a vacuum. His experiment involved slow light as well as passing light through a vacuum. He generated two single photons, passing one through rubidium atoms that had been cooled with a laser (thus slowing the light) and passing one through a vacuum. Both times, apparently, the precursors preceded the photons' main bodies, and the precursor traveled at "c" in a vacuum. According to Du, this implies that there is no possibility of light traveling faster than "c" and, thus, no possibility
Time travel
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of Sea-Tac Airport. The decision to stop this "starter" line a mile short of the airport would later be criticized by light rails opponents, but the explanation provided by Sound Transit was that it was that the designs were not completed for a planned remodel of Sea-Tac and that they only had $12 million to extend the line when the projected cost to do so was between $350 million and $500 million. An audit by Deloitte & Touche discovered that while Sound Transit was much better than before, it still ran a risk of cost overruns by not having better
History of Link light rail
15454
falls faster than a lighter object is incorrect. A contrary opinion is given by Carlo Rovelli, who argues that Aristotle's physics of motion is correct within its domain of validity, that of objects in the Earth's gravitational field immersed in a fluid such as air. In this system, heavy bodies in steady fall indeed travel faster than light ones (whether friction is ignored, or not), and they do fall more slowly in a denser medium. Newton's "forced" motion corresponds to Aristotle's "violent" motion with its external agent, but Aristotle's assumption that the agent's effect stops immediately it stops acting (e.g.,
Aristotle
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depth where the sound speed is at a minimum is the sound channel axis. This is a characteristic that can be found in optical guides. If a sound wave propagates away from this horizontal channel, the part of the wave furthest from the channel axis travels faster, so the wave turns back toward the channel axis. As a result, the sound waves trace a path that oscillates across the SOFAR channel axis. This principle is similar to long distance transmission of light in an optical fiber. In this channel, a sound has a range of over 2000 km. To use
RAFOS float
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Metal Fatigue (video game) Metal Fatigue (also known as Metal Conflict), is a futuristic science fiction, real-time strategy computer game developed by Zono and published by Psygnosis (in Europe) and TalonSoft (in the United States). The game was re-released in June 21, 2018 on GOG.com and Steam (software) by the Nightdive Studios who have acquired the rights to the game. During the 23rd century, man has discovered faster-than-light travel and has finally reached the stars. Galactic exploration had confirmed man's worst two fears. First, a warlike, alien race with vastly superior technology does exist. The exploration fleet reported sentient structures
Metal Fatigue (video game)
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the relativistic gravitational interaction arises as the small-amplitude collective excitation mode whereas relativistic elementary particles can be described by the particle-like modes in the limit of low momenta. The important fact is that at very high velocities the behavior of the particle-like modes becomes distinct from the relativistic one - they can reach the speed of light limit at finite energy; also, faster-than-light propagation is possible without requiring moving objects to have imaginary mass. In 2007 the MINOS collaboration reported results measuring the flight-time of 3 GeV neutrinos yielding a speed exceeding that of light by 1.8-sigma significance. However, those
Faster-than-light
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Super Comp, Super Gas, Super Stock, and Stock classes, as well as some dial-in classes), if a competitor is faster than his or her predetermined time (a "breakout"), that competitor loses. If both competitors are faster than their predetermined times, the competitor who breaks out by less time wins. Regardless, a red light foul is worse than a breakout, except in Junior Dragster where exceeding the absolute limit is a cause for disqualification. Most race events use a traditional bracket system, where the losing car and driver are eliminated from the event while the winner advances to the next round,
Drag racing
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it is possible for the group velocity (as defined above) of laser light pulses sent through lossy materials, or gainful materials, to significantly exceed the speed of light in vacuum . The peaks of wavepackets were also seen to move faster than . In all these cases, however, there is no possibility that signals could be carried faster than the speed of light in vacuum, since the high value of does not help to speed up the true motion of the sharp wavefront that would occur at the start of any real signal. Essentially the seemingly superluminal transmission is an
Group velocity
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a laser beam is swept quickly across a distant object, the spot of light can move faster than "c", although the initial movement of the spot is delayed because of the time it takes light to get to the distant object at the speed "c". However, the only physical entities that are moving are the laser and its emitted light, which travels at the speed "c" from the laser to the various positions of the spot. Similarly, a shadow projected onto a distant object can be made to move faster than "c", after a delay in time. In neither case
Speed of light
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Shengwang Du Shengwang Du is a professor in the department of physics at Hong Kong University of Science and Technology. He is noted for having led a team that performed an experiment showing individual photons cannot travel faster than the speed of light ("c") in a vacuum, thus apparently removing one approach to time travel. Du claims in a peer reviewed journal to have observed single photons' precursors, saying that they travel no faster than "c" in a vacuum. His experiment involved slow light as well as passing light through a vacuum. He generated two single photons, passing one through
Shengwang Du
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the source to the object faster than "c", nor does any information travel faster than light. An analogy can be made to pointing a water hose in one direction and then quickly moving the hose to point the stream of water in another direction. At no point does the water leaving the hose ever increase in velocity, but the endpoint of the stream can be moved faster than the water in the stream itself. Since there is no "retardation" (or aberration) of the apparent position of the source of a gravitational or electric static field when the source moves with
Faster-than-light
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results are still negative. In the 2011 Faster-than-light neutrino anomaly, the OPERA collaboration published results which appeared to show that the speed of neutrinos is slightly faster than the speed of light. However, sources of errors were found and confirmed in 2012 by the OPERA collaboration, which fully explained the initial results. In their final publication, a neutrino speed consistent with the speed of light was stated. Also subsequent experiments found agreement with the speed of light, see measurements of neutrino speed. It was also claimed that special relativity cannot handle acceleration, which would lead to contradictions in some situations.
Criticism of the theory of relativity
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Macross Within the series, the term "Macross" is used to denote the main capital ship. This theme began in the original Macross, the SDF-1 "Macross". "Overtechnology" refers to the scientific advances discovered in an alien starship ASS-1 ("Alien Star Ship - One" later renamed "Super Dimension Fortress - One Macross") that crashed on "South Ataria" island. Humans were able to reverse engineer the technology to create the mecha (variable fighters and destroids), faster-than-light space fold drive for starships and other advanced technologies that the series features. The first TV series was adapted into the first season of "Robotech" in 1985,
Macross
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pair and so it can't be observed until both photons have been measured, ensuring that an experimenter watching only the photons going through the slit does not obtain information about the other photons in an FTL or backwards-in-time manner. Faster-than-light communication is, according to relativity, equivalent to time travel. What we measure as the speed of light in a vacuum (or near vacuum) is actually the fundamental physical constant "c". This means that all inertial observers, regardless of their relative velocity, will always measure zero-mass particles such as photons traveling at "c" in a vacuum. This result means that measurements
Faster-than-light
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demonstrated non-local quantum correlations between particles separated by over 10 kilometers. But as noted earlier, the non-local correlations seen in entanglement cannot actually be used to transmit classical information faster than light, so that relativistic causality is preserved; see no-communication theorem for further information. A 2008 quantum physics experiment also performed by Nicolas Gisin and his colleagues has determined that in any hypothetical non-local hidden-variables theory the speed of the quantum non-local connection (what Einstein called "spooky action at a distance") is at least 10,000 times the speed of light. The delayed-choice quantum eraser is a version of the EPR
Faster-than-light
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the Chandra X-ray Observatory in 2011 discovered that it produces the fastest winds ever coming from an accretion disk at 20 million mph (3% of the speed of light). This is 10 times faster than the next highest measured wind speed. According to Ashley King from the University of Michigan "Contrary to the popular perception of black holes pulling in all of the material that gets close, we estimate up to 95 percent of the matter in the disk around IGR J17091 is expelled by the wind." IGR J17091 also exhibits peculiar X-ray variability patterns or "heartbeats" which are small,
IGR J17091-3624
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prohibitive cost of gallium. Larger experiments have therefore turned to a cheaper reaction mass. "Ring-imaging" Cherenkov detectors take advantage of a phenomenon called Cherenkov light. Cherenkov radiation is produced whenever charged particles such as electrons or muons are moving through a given detector medium somewhat faster than the speed of light in that medium. In a Cherenkov detector, a large volume of clear material such as water or ice is surrounded by light-sensitive photomultiplier tubes. A charged lepton produced with sufficient energy and moving through such a detector does travel somewhat faster than the speed of light in the detector
Neutrino detector
4257461
find out that it doesn't go only at the speed of light! It may surprise you that there is an amplitude for a photon to go at speeds faster or slower than the conventional speed, "c"." These virtual photons, however, do not violate causality or special relativity, as they are not directly observable and information cannot be transmitted acausally in the theory. Feynman diagrams and virtual photons are usually interpreted not as a physical picture of what is taking place, but rather as a convenient calculation tool (which, in some cases, happen to involve faster-than-light velocity vectors). In 1937, Paul
Variable speed of light
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take them out to more than 1000 AU. The circumference of a circle with a radius of 1000 AU is greater than one light day. In other words, a comet at such a distance is superluminal in a geostatic, and therefore non-inertial, frame. If a laser beam is swept across a distant object, the spot of laser light can easily be made to move across the object at a speed greater than "c". Similarly, a shadow projected onto a distant object can be made to move across the object faster than "c". In neither case does the light travel from
Faster-than-light
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still recovering from a two-century-long era of war and chaos that began with the Soviet conquest of North America in World War III and ended with the unification of the Solar System at the conclusion of a war between Mars and Venus. Twenty-two years after the discovery of a faster-than-light drive, Troas is the only Earthlike world to be discovered, and enthusiasm for interstellar travel is waning. If Troas is not opened to colonization, humanity may give up interstellar travel altogether. The effort to mount a second expedition to Troas is plagued with difficulties. The Lagrange Institute is unable to
Question and Answer (novel)
790989
energy and FTL (faster-than-light). A hypothetical particle with complex rest mass would always travel faster than the speed of light. Such particles are called tachyons. There is no confirmed existence of tachyons. If the rest mass formula_4 is complex this implies that the denominator is complex because the total energy is observable and thus must be real. Therefore, the quantity under the square root must be negative, which can only happen if "v" is greater than "c". As noted by Gregory Benford "et al.," special relativity implies that tachyons, if they existed, could be used to communicate backwards in time
Exotic matter
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passed through the gauze); indeed, in early lamps worse than candles. The problem not solved until the introduction of electric lighting around 1900 and the introduction of battery-powered helmet lamps in 1930. The poor light provided yet another reason for miners to try to circumvent the locks. Early lamps (the Davy, Geordie and Clanny) had the gauze exposed to air currents. It was quickly discovered that an air current could cause the flame to pass through the gauze. The flame playing directly on the gauze heats it faster than the heat can be conducted away, eventually igniting the gas outside
Safety lamp
13857816
also increased. The first light curves of SNe Ia obtained using CCD photometry showed that some supernovae had faster decline rates than others. Later, the low luminosity Ia SN 1991bg with a fast decline rate was discovered. All this motivated the American astronomer Mark M. Phillips to revise this relationship precisely during the course of the Calán/Tololo Supernova Survey. The correlation had been difficult to prove because Pskovskii's slope (β) parameter was difficult to measure with precision in practice, a necessary condition to prove the correlation. Rather than trying to determine the slope, Phillips used a simpler and more robust
Phillips relationship
477524
Lorentz transform of special relativity) in which an observer would see an effect precede its cause (i.e. the postulate of causality would be violated). Causal notions appear in the context of the flow of mass-energy. For example, it is commonplace to argue that causal efficacy can be propagated by waves (such as electromagnetic waves) only if they propagate no faster than light. Wave packets have group velocity and phase velocity. For waves that propagate causal efficacy, both of these must travel no faster than light. Thus light waves often propagate causal efficacy but de Broglie waves often have phase velocity
Causality
146325
power does not. The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if proper distance and cosmological time are used to calculate the speeds of these galaxies. However, in general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any simple relation to velocity calculated locally. (See comoving distance for a discussion of different notions of 'velocity' in cosmology.) Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply
Faster-than-light
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locations in less time than light could in normal or undistorted spacetime. According to the current scientific theories, matter is required to travel at slower-than-light (also subluminal or STL) speed with respect to the locally distorted spacetime region. "Apparent" FTL is not excluded by general relativity; however, any apparent FTL physical plausibility is speculative. Examples of apparent FTL proposals are the Alcubierre drive and the traversable wormhole. In the context of this article, FTL is the transmission of information or matter faster than "c", a constant equal to the speed of light in a vacuum, which is 299,792,458 m/s (by
Faster-than-light
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exist in a superposition of two quantum states. If the particles are separated and one particle's quantum state is observed, the other particle's quantum state is determined instantaneously (i.e., faster than light could travel from one particle to the other). However, it is impossible to control which quantum state the first particle will take on when it is observed, so information cannot be transmitted in this manner. Another quantum effect that predicts the occurrence of faster-than-light speeds is called the Hartman effect: under certain conditions the time needed for a virtual particle to tunnel through a barrier is constant, regardless
Speed of light
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states that, even moving at the speed of light, the ship could not arrive before then. However, it is travelling "faster" than light and is upon them in minutes. Verdeschi calls for a visual; the ship is an impressive—and familiar—design. It is a Superswift, an Earth ship designed for interstellar travel. The project was shelved by the World Space Commission as no one could devise a practical faster-than-light propulsion system—at least as of . Tracked by Alpha's laser batteries, the ship comes in for a landing. Contact is made and the visual of its captain shocks Verdeschi—it is his older
The Bringers of Wonder, Part One
2188675
This result has been interpreted to mean that dolphins sleep only one hemisphere of their brain at a time, possibly to control their voluntary respiration system or to be vigilant for predators. This is also given as explanation for the large size of their brains. Dolphin brain stem transmission time is faster than that normally found in humans, and is approximately equivalent to the speed in rats. As echo-location is the dolphin's primary senseanalogous to vision in primates – and since sound travels four and a half times faster in water than in air, scientists speculate that the faster brain
Cetacean intelligence