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what particles are allowed to go light speed

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Propagation of information or matter faster than the speed of light

Faster-than-lite (also FTL, superluminal or supercausal) travel and communication are the conjectural propagation of affair or data faster than the speed of low-cal ( c ). The special theory of relativity implies that only particles with nil rest mass (i.e., photons) may travel at the speed of low-cal, and that nothing may travel faster.

Particles whose speed exceeds that of calorie-free (tachyons) have been hypothesized, simply their existence would violate causality and would imply fourth dimension travel. The scientific consensus is that they do not exist. "Apparent" or "effective" FTL,[1] [2] [3] [4] on the other mitt, depends on the hypothesis that unusually distorted regions of spacetime might permit matter to attain distant locations in less fourth dimension than low-cal could in normal ("undistorted") spacetime.

As of the 21st century, according to electric current scientific theories, matter is required to travel at slower-than-light (also STL or subluminal) speed with respect to the locally distorted spacetime region. Apparent FTL is not excluded by general relativity; still, whatsoever credible FTL physical plausibility is currently speculative. Examples of credible FTL proposals are the Alcubierre drive, Krasnikov tubes, traversable wormholes, and quantum tunneling.[5] [6]

Superluminal travel of non-data [edit]

In the context of this article, FTL is the transmission of information or matter faster than c, a constant equal to the speed of low-cal in vacuum, which is 299,792,458 m/south (by definition of the metre[vii]) or near 186,282.397 miles per second. This is not quite the same equally traveling faster than lite, since:

  • Some processes propagate faster than c, simply cannot carry information (see examples in the sections immediately following).
  • In some materials where low-cal travels at speed c/n (where n is the refractive index) other particles can travel faster than c/due north (but still slower than c), leading to Cherenkov radiation (see stage velocity below).

Neither of these phenomena violates special relativity or creates bug with causality, and thus neither qualifies as FTL as described here.

In the following examples, certain influences may appear to travel faster than lite, but they do not convey energy or information faster than low-cal, so they practise not violate special relativity.

Daily heaven move [edit]

For an earth-spring observer, objects in the sky complete ane revolution around the Earth in 1 day. Proxima Centauri, the nearest star exterior the Solar System, is most four light-years away.[8] In this frame of reference, in which Proxima Centauri is perceived to exist moving in a circular trajectory with a radius of four low-cal years, information technology could exist described as having a speed many times greater than c every bit the rim speed of an object moving in a circle is a product of the radius and angular speed.[viii] It is also possible on a geostatic view, for objects such as comets to vary their speed from subluminal to superluminal and vice versa simply considering the distance from the Earth varies. Comets may have orbits which have them out to more than than 1000 AU.[9] The circumference of a circumvolve 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.

Lite spots and shadows [edit]

If a light amplification by stimulated emission of radiation beam is swept across a distant object, the spot of laser light can easily be made to move beyond the object at a speed greater than c.[10] Similarly, a shadow projected onto a distant object tin exist made to move across the object faster than c.[10] In neither case does the light travel from the source to the object faster than c, nor does whatsoever information travel faster than light.[ten] [eleven] [12]

Closing speeds [edit]

The rate at which two objects in movement in a single frame of reference get closer together is called the mutual or closing speed. This may approach twice the speed of light, as in the case of two particles travelling at close to the speed of low-cal in reverse directions with respect to the reference frame.

Imagine two fast-moving particles approaching each other from opposite sides of a particle accelerator of the collider blazon. The endmost speed would exist the charge per unit at which the distance between the two particles is decreasing. From the point of view of an observer standing at residue relative to the accelerator, this charge per unit will be slightly less than twice the speed of light.

Special relativity does not prohibit this. It tells us that it is wrong to use Galilean relativity to compute the velocity of one of the particles, as would exist measured past an observer traveling aslope the other particle. That is, special relativity gives the correct velocity-improver formula for calculating such relative velocity.

Information technology is instructive to compute the relative velocity of particles moving at v and −v in accelerator frame, which corresponds to the closing speed of 2v >c. Expressing the speeds in units of c, β =5/c:

β rel = β + β one + β 2 = ii β 1 + β two ≤ one. {\displaystyle \beta _{\text{rel}}={\frac {\beta +\beta }{1+\beta ^{2}}}={\frac {2\beta }{1+\beta ^{2}}}\leq i.}

Proper speeds [edit]

If a spaceship travels to a planet one calorie-free-year (as measured in the Earth'southward rest frame) away from Earth at high speed, the time taken to attain that planet could exist less than one yr as measured by the traveller's clock (although it will e'er be more than 1 year as measured by a clock on Globe). The value obtained by dividing the distance traveled, as determined in the Globe's frame, by the time taken, measured past the traveller's clock, is known as a proper speed or a proper velocity. At that place is no limit on the value of a proper speed as a proper speed does not represent a speed measured in a unmarried inertial frame. A light signal that left the Earth at the same time equally the traveller would always get to the destination before the traveller.

Possible distance abroad from Globe [edit]

Since 1 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 twenty and 60. A traveler would so never be able to reach more than the very few star systems which exist inside the limit of xx–40 calorie-free-years from the Earth. This is a mistaken determination: because of time dilation, the traveler can travel thousands of light-years during their forty active years. If the spaceship accelerates at a constant 1 grand (in its ain changing frame of reference), it volition, after 354 days, attain speeds a piffling nether the speed of calorie-free (for an observer on Earth), and time dilation will increase the traveler's lifespan to thousands of Earth years, seen from the reference system of the Solar System ⁠— but the traveler's subjective lifespan volition not thereby modify. If they were then to return to Earth, the traveler would arrive on Globe thousands of years into the hereafter. Their travel speed would not have been observed from Globe as being supraluminal ⁠— neither for that thing would it appear to be so from the traveler's perspective– but the traveler would instead have experienced a length contraction of the universe in their direction of travel. Subsequently the traveler reverses course, the World will seem to experience much more time passing than the traveler does. So while the traveler'due south (ordinary) coordinate speed cannot exceed c, their proper speed, or distance traveled from the World's signal of reference divided by proper time, can be much greater than c. This is seen in statistical studies of muons traveling much farther than c times their one-half-life (at balance), if traveling close to c.[13]

Phase velocities above c [edit]

The phase velocity of an electromagnetic wave, when traveling through a medium, can routinely exceed c, the vacuum velocity of light. For example, this occurs in about glasses at 10-ray frequencies.[14] However, the phase velocity of a wave corresponds to the propagation speed of a theoretical single-frequency (purely monochromatic) component of the wave at that frequency. Such a wave component must exist infinite in extent and of constant aamplitude (otherwise it is not truly monochromatic), and and then cannot convey any information.[15] Thus a phase velocity above c does not imply the propagation of signals with a velocity higher up c.[16]

Group velocities above c [edit]

The group velocity of a wave may also exceed c in some circumstances.[17] [eighteen] In such cases, which typically at the same time involve rapid attenuation of the intensity, the maximum of the envelope of a pulse may travel with a velocity above c. However, fifty-fifty this state of affairs does not imply the propagation of signals with a velocity in a higher place c,[nineteen] even though i may be tempted to acquaintance pulse maxima with signals. The latter association has been shown to be misleading, because the information on the inflow of a pulse can be obtained before the pulse maximum arrives. For example, if some mechanism allows the full transmission of the leading office of a pulse while strongly attenuating the pulse maximum and everything behind (distortion), the pulse maximum is effectively shifted forrad in time, while the data on the pulse does not come faster than c without this upshot.[20] Still, group velocity can exceed c in some parts of a Gaussian beam in vacuum (without attenuation). The diffraction causes the top of the pulse to propagate faster, while overall power does not.[21]

Universal expansion [edit]

The expansion of the universe causes distant galaxies to recede from united states faster than the speed of light, if proper distance and cosmological time are used to summate the speeds of these galaxies. However, in full general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any elementary relation to velocity calculated locally.[25] (Run into Comoving and proper distances for a word of different notions of 'velocity' in cosmology.) Rules that utilize to relative velocities in special relativity, such as the rule that relative velocities cannot increment past the speed of calorie-free, do non utilize to relative velocities in comoving coordinates, which are often described in terms of the "expansion of space" betwixt galaxies. This expansion charge per unit is thought to have been at its pinnacle during the inflationary epoch idea to have occurred in a tiny fraction of the 2nd after the Big Blindside (models advise the period would have been from around x−36 seconds after the Large Bang to around 10−33 seconds), when the universe may have rapidly expanded by a factor of around 10xx to ten30.[26]

There are many galaxies visible in telescopes with red shift numbers of ane.4 or college. All of these are currently traveling away from us at speeds greater than the speed of lite. 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 somewhen.[27] [28] [29]

Even so, considering the expansion of the universe is accelerating, it is projected that most galaxies volition eventually cross a type of cosmological effect horizon where whatsoever light they emit past that point will never be able to reach us at whatever time in the infinite hereafter,[30] because the light never reaches a point where its "peculiar velocity" towards us exceeds the expansion velocity away from us (these two notions of velocity are too discussed in Comoving and proper distances#Uses of the proper distance). The current distance to this cosmological event horizon is about 16 billion low-cal-years, significant that a signal from an event happening at present would eventually be able to reach us in the futurity if the upshot was less than sixteen billion light-years away, but the signal would never achieve us if the upshot was more than 16 billion light-years away.[28]

Astronomical observations [edit]

Apparent superluminal motion is observed in many radio galaxies, blazars, quasars, and recently also in microquasars. The effect was predicted before information technology was observed by Martin Rees[ clarification needed ] and tin can exist explained as an optical illusion caused past the object partly moving in the direction of the observer,[31] when the speed calculations presume it does not. The phenomenon does not contradict the theory of special relativity. Corrected calculations prove these objects take velocities close to the speed of light (relative to our reference frame). They are the first examples of large amounts of mass moving at close to the speed of lite.[32] Globe-spring laboratories have merely been able to advance pocket-size numbers of elementary particles to such speeds.

Quantum mechanics [edit]

Certain phenomena in quantum mechanics, such as breakthrough entanglement, might requite the superficial impression of allowing communication of information faster than light. According to the no-advice theorem these phenomena do not allow true communication; they but permit 2 observers in different locations meet the aforementioned system simultaneously, without any way of controlling what either sees. Wavefunction collapse tin be viewed as an epiphenomenon of quantum decoherence, which in plow is null more than an effect of the underlying local fourth dimension evolution of the wavefunction of a system and all of its environment. Since the underlying beliefs does not violate local causality or allow FTL communication, it follows that neither does the additional effect of wavefunction plummet, whether existent or apparent.

The doubtfulness principle implies that private photons may travel for short distances at speeds somewhat faster (or slower) than c, even in vacuum; this possibility must be taken into business relationship when enumerating Feynman diagrams for a particle interaction.[33] However, it was shown in 2011 that a single photon may non travel faster than c.[34] In quantum mechanics, virtual particles may travel faster than light, and this phenomenon is related to the fact that static field effects (which are mediated by virtual particles in breakthrough terms) may travel faster than light (see section on static fields above). However, macroscopically these fluctuations average out, then that photons practise travel in directly lines over long (i.eastward., non-quantum) distances, and they practice travel at the speed of light on boilerplate. 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 — virtually often in the context of a kind of quantum tunnelling phenomenon. Unremarkably, such reports deal with a stage velocity or group velocity faster than the vacuum velocity of light.[35] [36] However, every bit stated in a higher place, a superluminal phase velocity cannot be used for faster-than-light transmission of data.[37] [38]

Hartman effect [edit]

The Hartman effect is the tunneling result through a barrier where the tunneling time tends to a abiding for large barriers.[39] [40] This could, for example, be the gap between two prisms. When the prisms are in contact, the light passes straight through, but when there is a gap, the low-cal is refracted. There is a non-zippo probability that the photon will tunnel across the gap rather than follow the refracted path. For large gaps between the prisms the tunnelling fourth dimension approaches a constant and thus the photons appear to have crossed with a superluminal speed.[41]

However, the Hartman effect cannot actually be used to violate relativity by transmitting signals faster than c, considering the tunnelling time "should non be linked to a velocity since evanescent waves do not propagate".[42] The evanescent waves in the Hartman effect are due to virtual particles and a non-propagating static field, equally mentioned in the sections above for gravity and electromagnetism.

Casimir result [edit]

In physics, the Casimir–Polder force is a physical force exerted between separate objects due to resonance of vacuum energy in the intervening space between the objects. This is sometimes described in terms of virtual particles interacting with the objects, owing to the mathematical form of one possible fashion of calculating the strength of the effect. Considering the force of the forcefulness falls off quickly with distance, it is only measurable when the distance between the objects is extremely small. Because the effect is due to virtual particles mediating a static field effect, it is subject to the comments virtually static fields discussed above.

EPR paradox [edit]

The EPR paradox refers to a famous idea experiment of Albert Einstein, Boris Podolsky and Nathan Rosen that was realized experimentally for the first time by Alain Aspect in 1981 and 1982 in the Aspect experiment. In this experiment, the measurement of the state of one of the quantum systems of an entangled pair apparently instantaneously forces the other arrangement (which may be distant) to be measured in the complementary state. However, no information tin be transmitted this way; the answer to whether or not the measurement really affects the other quantum system comes down to which estimation of quantum mechanics one subscribes to.

An experiment performed in 1997 past Nicolas Gisin has demonstrated non-local quantum correlations between particles separated past over ten kilometers.[43] But as noted before, the non-local correlations seen in entanglement cannot really exist used to transmit classical information faster than light, so that relativistic causality is preserved. The situation is akin to sharing a synchronized coin flip, where the second person to flip their coin will always see the opposite of what the first person sees, but neither has any way of knowing whether they were the start or second flipper, without communicating classically. See No-communication theorem for further information. A 2008 quantum physics experiment likewise performed by Nicolas Gisin and his colleagues has determined that in any hypothetical not-local hidden-variable theory, the speed of the quantum non-local connection (what Einstein chosen "spooky action at a altitude") is at least 10,000 times the speed of light.[44]

Delayed choice quantum eraser [edit]

The delayed-choice quantum eraser is a version of the EPR paradox in which the observation (or not) of interference after the passage of a photon through a double slit experiment depends on the conditions of observation of a second photon entangled with the offset. The characteristic of this experiment is that the ascertainment of the 2d photon tin can accept place at a afterwards fourth dimension than the observation of the first photon,[45] which may give the impression that the measurement of the afterwards photons "retroactively" determines whether the earlier photons prove interference or non, although the interference pattern can but be seen past correlating the measurements of both members of every pair and then it can't exist observed until both photons take been measured, ensuring that an experimenter watching simply the photons going through the slit does non obtain information almost the other photons in an FTL or backwards-in-time manner.[46] [47]

Superluminal communication [edit]

Faster-than-low-cal communication is, co-ordinate to relativity, equivalent to time travel. What we measure as the speed of light in vacuum (or virtually vacuum) is actually the fundamental physical constant c. This means that all inertial and, for the coordinate speed of light, not-inertial observers, regardless of their relative velocity, will e'er measure out aught-mass particles such as photons traveling at c in vacuum. This result means that measurements of time and velocity in dissimilar frames are no longer related simply past constant shifts, but are instead related by Poincaré transformations. These transformations accept important implications:

  • The relativistic momentum of a massive particle would increase with speed in such a fashion that at the speed of light an object would have infinite momentum.
  • To accelerate an object of non-zero residuum mass to c would require infinite time with any finite acceleration, or infinite acceleration for a finite amount of fourth dimension.
  • Either way, such acceleration requires space energy.
  • Some observers with sub-low-cal relative motility volition disagree about which occurs outset of whatever two events that are separated past a infinite-like interval.[48] In other words, any travel that is faster-than-light volition be seen every bit traveling backwards in time in some other, as valid, frames of reference,[49] or need to assume the speculative hypothesis of possible Lorentz violations at a presently unobserved scale (for instance the Planck scale).[ commendation needed ] Therefore, whatever theory which permits "true" FTL also has to cope with time travel and all its associated paradoxes,[50] or else to assume the Lorentz invariance to be a symmetry of thermodynamical statistical nature (hence a symmetry cleaved at some before long unobserved scale).
  • In special relativity the coordinate speed of calorie-free is simply guaranteed to exist c in an inertial frame; in a non-inertial frame the coordinate speed may be different from c.[51] In general relativity no coordinate system on a large region of curved spacetime is "inertial", then information technology is permissible to utilize a global coordinate arrangement where objects travel faster than c, simply in the local neighborhood of any betoken in curved spacetime we tin can define a "local inertial frame" and the local speed of light volition exist c in this frame,[52] with massive objects moving through this local neighborhood always having a speed less than c in the local inertial frame.

Justifications [edit]

Casimir vacuum and quantum tunnelling [edit]

Special relativity postulates that the speed of low-cal in vacuum is invariant in inertial frames. That is, it will be the aforementioned from whatsoever frame of reference moving at a constant speed. The equations practice not specify whatsoever particular value for the speed of calorie-free, which is an experimentally adamant quantity for a stock-still unit of length. Since 1983, the SI unit of measurement of length (the meter) has been defined using the speed of light.

The experimental determination has been fabricated in vacuum. However, the vacuum we know is non the only possible vacuum which can exist. The vacuum has energy associated with it, called only the vacuum energy, which could perhaps be altered in certain cases.[53] When vacuum energy is lowered, light itself has been predicted to go faster than the standard value c. This is known every bit the Scharnhorst upshot. Such a vacuum tin be produced by bringing two perfectly polish metal plates together at about diminutive bore spacing. Information technology is called a Casimir vacuum. Calculations imply that light will go faster in such a vacuum past a minuscule amount: a photon traveling betwixt two plates that are 1 micrometer apart would increment the photon'south speed by simply nearly one office in x36.[54] Accordingly, there has equally yet been no experimental verification of the prediction. A contempo analysis[55] argued that the Scharnhorst consequence cannot be used to send information backwards in time with a unmarried gear up of plates since the plates' rest frame would define a "preferred frame" for FTL signalling. Yet, with multiple pairs of plates in motion relative to one another the authors noted that they had no arguments that could "guarantee the full absence of causality violations", and invoked Hawking'southward speculative chronology protection conjecture which suggests that feedback loops of virtual particles would create "uncontrollable singularities in the renormalized quantum stress-energy" on the purlieus of any potential time machine, and thus would require a theory of breakthrough gravity to fully analyze. Other authors argue that Scharnhorst'due south original analysis, which seemed to testify the possibility of faster-than-c signals, involved approximations which may be incorrect, so that it is non articulate whether this issue could really increase signal speed at all.[56]

The physicists Günter Nimtz and Alfons Stahlhofen, of the Academy of Cologne, claim to take violated relativity experimentally by transmitting photons faster than the speed of light.[41] They say they have conducted an experiment in which microwave photons — relatively low-energy packets of light — travelled "instantaneously" between a pair of prisms that had been moved upwards to three ft (i chiliad) apart. Their experiment involved an optical phenomenon known as "evanescent modes", and they claim that since evanescent modes accept an imaginary wave number, they represent a "mathematical analogy" to breakthrough tunnelling.[41] Nimtz has also claimed that "evanescent modes are not fully describable by the Maxwell equations and quantum mechanics take to be taken into consideration."[57] Other scientists such as Herbert G. Winful and Robert Helling take argued that in fact there is nothing quantum-mechanical about Nimtz'due south experiments, and that the results can be fully predicted by the equations of classical electromagnetism (Maxwell's equations).[58] [59]

Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of." Notwithstanding, other physicists say that this phenomenon does not allow information to exist transmitted faster than calorie-free. Aephraim Steinberg, a quantum optics proficient at the University of Toronto, Canada, uses the analogy of a railroad train traveling from Chicago to New York, but dropping off train cars from the tail at each station forth the manner, so that the center of the always-shrinking main train moves forward at each stop; in this way, the speed of the eye of the train exceeds the speed of whatever of the private cars.[lx]

Winful argues that the train illustration is a variant of the "reshaping statement" for superluminal tunneling velocities, but he goes on to say that this argument is not actually supported by experiment or simulations, which really show that the transmitted pulse has the same length and shape as the incident pulse.[58] Instead, Winful argues that the group delay in tunneling is non actually the transit time for the pulse (whose spatial length must be greater than the barrier length in order for its spectrum to exist narrow plenty to let tunneling), but is instead the lifetime of the energy stored in a standing wave which forms inside the barrier. Since the stored energy in the barrier is less than the energy stored in a barrier-costless region of the aforementioned length due to destructive interference, the grouping delay for the energy to escape the bulwark region is shorter than it would be in free infinite, which according to Winful is the caption for evidently superluminal tunneling.[61] [62]

A number of authors take published papers disputing Nimtz's claim that Einstein causality is violated by his experiments, and at that place are many other papers in the literature discussing why breakthrough tunneling is not idea to violate causality.[63]

Information technology was later claimed past Eckle et al. that particle tunneling does indeed occur in aught real time.[64] Their tests involved tunneling electrons, where the group argued a relativistic prediction for tunneling time should be 500–600 attoseconds (an attosecond is i quintillionth (10−18) of a 2d). All that could be measured was 24 attoseconds, which is the limit of the test accuracy. Again, though, other physicists believe that tunneling experiments in which particles appear to spend anomalously short times within the barrier are in fact fully compatible with relativity, although there is disagreement about whether the explanation involves reshaping of the wave package or other effects.[61] [62] [65]

Surrender (accented) relativity [edit]

Because of the stiff empirical back up for special relativity, any modifications to information technology must necessarily be quite subtle and difficult to mensurate. The best-known attempt is doubly special relativity, which posits that the Planck length is as well the same in all reference frames, and is associated with the piece of work of Giovanni Amelino-Camelia and João Magueijo.[66] [67] There are speculative theories that merits inertia is produced past the combined mass of the universe (due east.one thousand., Mach's principle), which implies that the rest frame of the universe might exist preferred by conventional measurements of natural police. If confirmed, this would imply special relativity is an approximation to a more than general theory, but since the relevant comparison would (by definition) exist outside the observable universe, it is hard to imagine (much less construct) experiments to test this hypothesis. Despite this difficulty, such experiments take been proposed.[68]

Spacetime distortion [edit]

Although the theory of special relativity forbids objects to take a relative velocity greater than light speed, and full general relativity reduces to special relativity in a local sense (in small regions of spacetime where curvature is negligible), general relativity does let the space between distant objects 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 altitude of more than about fourteen billion light-years from us today have a recession velocity which is faster than lite.[69] Miguel Alcubierre theorized that information technology would exist 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 quickly contracting and the infinite at the dorsum is speedily expanding, with the issue that the chimera can accomplish a afar destination much faster than a light beam moving outside the bubble, but without objects inside the chimera locally traveling faster than lite.[70] Notwithstanding, several objections raised against the Alcubierre bulldoze 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 afar points in space. As with the Alcubierre bulldoze, travelers moving through the wormhole would not locally motility faster than low-cal travelling through the wormhole alongside them, just they would be able to accomplish their destination (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 effectually a spaceship with an extremely large amount of energy would create a "chimera" that could crusade the send to travel faster than the speed of light. To create this bubble, the physicists believe manipulating the 10th spatial dimension would alter the nighttime free energy in three large spatial dimensions: pinnacle, width and length. Cleaver said positive dark energy is currently responsible for speeding upward the expansion charge per unit of our universe as time moves on.[71]

Lorentz symmetry violation [edit]

The possibility that Lorentz symmetry may be violated has been seriously considered in the last two decades, peculiarly later on the development of a realistic effective field theory that describes this possible violation, the and so-called Standard-Model Extension.[72] [73] [74] This general framework has allowed experimental searches by ultra-loftier free energy catholic-ray experiments[75] and a wide variety of experiments in gravity, electrons, protons, neutrons, neutrinos, mesons, and photons.[76] The breaking of rotation and boost invariance causes direction dependence in the theory as well every bit anarchistic free energy dependence that introduces novel effects, including Lorentz-violating neutrino oscillations and modifications to the dispersion relations of different particle species, which naturally could make particles motion faster than light.

In some models of broken Lorentz symmetry, information technology is postulated that the symmetry is still congenital into the most fundamental laws of physics, but that spontaneous symmetry breaking of Lorentz invariance[77] shortly subsequently the Big Bang could have left a "relic field" throughout the universe which causes particles to behave differently depending on their velocity relative to the field;[78] however, at that place are besides some models where Lorentz symmetry is broken in a more than fundamental way. If Lorentz symmetry can cease to exist a primal symmetry at the Planck calibration or at some other fundamental scale, it is believable that particles with a critical speed different from the speed of light be the ultimate constituents of matter.

In current models of Lorentz symmetry violation, the phenomenological parameters are expected to be energy-dependent. Therefore, as widely recognized,[79] [80] existing low-free energy bounds cannot exist applied to high-energy phenomena; however, many searches for Lorentz violation at high energies have been carried out using the Standard-Model Extension.[76] Lorentz symmetry violation is expected to become stronger as one gets closer to the primal scale.

Superfluid theories of physical vacuum [edit]

In this approach the physical vacuum is viewed as a breakthrough superfluid which is essentially non-relativistic whereas Lorentz symmetry is non an exact symmetry of nature just rather the approximate description valid merely for the modest fluctuations of the superfluid background.[81] Inside the framework of the approach a theory was proposed in which the physical vacuum is conjectured to be a quantum Bose liquid whose ground-state wavefunction is described by the logarithmic Schrödinger equation. It was shown that the relativistic gravitational interaction arises every bit the small-aamplitude collective excitation way[82] whereas relativistic simple particles can exist described by the particle-like modes in the limit of low momenta.[83] The important fact is that at very high velocities the behavior of the particle-like modes becomes singled-out from the relativistic one - they can reach the speed of light limit at finite free energy; also, faster-than-light propagation is possible without requiring moving objects to have imaginary mass.[84] [85]

FTL neutrino flight results [edit]

MINOS experiment [edit]

In 2007 the MINOS collaboration reported results measuring the flight-fourth dimension of 3 GeV neutrinos yielding a speed exceeding that of light by ane.eight-sigma significance.[86] Notwithstanding, those measurements were considered to be statistically consequent with neutrinos traveling at the speed of light.[87] After the detectors for the project were upgraded in 2012, MINOS corrected their initial result and found agreement with the speed of calorie-free. Further measurements are going to be conducted.[88]

OPERA neutrino anomaly [edit]

On September 22, 2011, a preprint[89] from the OPERA Collaboration indicated detection of 17 and 28 GeV muon neutrinos, sent 730 kilometers (454 miles) from CERN about Geneva, Switzerland to the Gran Sasso National Laboratory in Italy, traveling faster than light by a relative amount of 2.48×10−five (approximately i in 40,000), a statistic with 6.0-sigma significance.[90] On 17 Nov 2011, a second follow-up experiment past OPERA scientists confirmed their initial results.[91] [92] However, scientists were skeptical nigh the results of these experiments, the significance of which was disputed.[93] In March 2012, the ICARUS collaboration failed to reproduce the OPERA results with their equipment, detecting neutrino travel time from CERN to the Gran Sasso National Laboratory indistinguishable from the speed of light.[94] Later the OPERA team reported 2 flaws in their equipment set-up that had acquired errors far outside their original confidence interval: a cobweb optic cable fastened improperly, which acquired the patently faster-than-light measurements, and a clock oscillator ticking also fast.[95]

Tachyons [edit]

In special relativity, information technology is impossible to accelerate an object to the speed of light, or for a massive object to move at the speed of lite. However, it might be possible for an object to exist which always moves faster than light. The hypothetical simple particles with this property are called tachyons or tachyonic particles. Attempts to quantize them failed to produce faster-than-calorie-free particles, and instead illustrated that their presence leads to an instability.[96] [97]

Various theorists take suggested that the neutrino might have a tachyonic nature,[98] [99] [100] [101] while others have disputed the possibility.[102]

General relativity [edit]

Full 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.[ citation needed ] Even so, it permits distortions in spacetime that allow an object to motion faster than light from the point of view of a afar observer.[ citation needed ] 1 such distortion is the Alcubierre drive, which tin exist thought of every bit producing a ripple in spacetime that carries an object forth with information technology. Another possible organization is the wormhole, which connects two distant locations as though by a shortcut. Both distortions would need to create a very strong curvature in a highly localized region of space-fourth dimension and their gravity fields would exist immense. To counteract the unstable nature, and prevent the distortions from collapsing nether their own 'weight', one would demand to introduce hypothetical exotic thing or negative energy.

General relativity also recognizes that whatsoever means of faster-than-calorie-free travel could too be used for fourth dimension travel. This raises problems with causality. Many physicists believe that the above phenomena are impossible and that future theories of gravity will prohibit them. One theory states that stable wormholes are possible, just that any effort to use a network of wormholes to violate causality would effect in their decay.[ citation needed ] In string theory, Eric G. Gimon and Petr Hořava have argued[103] that in a supersymmetric five-dimensional Gödel universe, quantum corrections to general relativity finer cutting off regions of spacetime with causality-violating airtight timelike curves. In particular, in the quantum theory a smeared supertube is present that cuts the spacetime in such a style that, although in the full spacetime a closed timelike bend passed through every indicate, no complete curves exist on the interior region bounded past the tube.

In fiction and popular culture [edit]

FTL travel is a mutual trope in science fiction.[104]

See also [edit]

  • Faster-than-light neutrino anomaly
  • Intergalactic travel
  • Krasnikov tube
  • Variable speed of light
  • Wheeler–Feynman cushion theory
  • Slow light

Notes [edit]

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References [edit]

  • Falla, D. F.; Floyd, Yard. J. (2002). "Superluminal movement in astronomy". European Periodical of Physics. 23 (1): 69–81. Bibcode:2002EJPh...23...69F. doi:ten.1088/0143-0807/23/ane/310.
  • Kaku, Michio (2008). "Faster than Light". Physics of the Impossible. Allen Lane. pp. 197–215. ISBN978-0-7139-9992-1.
  • Nimtz, Günter (2008). Zero Fourth dimension Space. Wiley-VCH. ISBN978-3-527-40735-four.
  • Cramer, J. G. (2009). "Faster-than-Low-cal Implications of Quantum Entanglement and Nonlocality". In Millis, Chiliad. G.; et al. (eds.). Frontiers of Propulsion Science. American Institute of Aeronautics and Astronautics. pp. 509–529. ISBN978-1-56347-956-iv.

External links [edit]

  • Measurement of the neutrino velocity with the OPERA detector in the CNGS beam
  • Encyclopedia of light amplification by stimulated emission of radiation physics and engineering science on "superluminal manual", with more details on phase and group velocity, and on causality
  • Markus Pössel: Faster-than-light (FTL) speeds in tunneling experiments: an annotated bibliography
  • Alcubierre, Miguel; The Warp Bulldoze: Hyper-Fast Travel Within General Relativity, Classical and Quantum Gravity 11 (1994), L73–L77
  • A systemized view of superluminal wave propagation
  • Relativity and FTL Travel FAQ
  • Usenet Physics FAQ: is FTL travel or communication Possible?
  • Relativity, FTL and causality
  • Yan, Kun (2006). "The tendency analytical equations of stable nuclides and the superluminal velocity motion laws of affair in geospace". Progress in Geophysics. 21: 38. Bibcode:2006PrGeo..21...38Y.
  • Glasser, Ryan T. (2012). "Stimulated Generation of Superluminal Light Pulses via Four-Wave Mixing". Physical Review Messages. 108 (17): 173902. arXiv:1204.0810. Bibcode:2012PhRvL.108q3902G. doi:ten.1103/PhysRevLett.108.173902. PMID 22680868. S2CID 46458102.
  • Conical and paraboloidal superluminal particle accelerators
  • Relativity and FTL (=Superluminal move) Travel Homepage

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Source: https://en.wikipedia.org/wiki/Faster-than-light

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