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Fast-than-Light Travel is an interesting and controversial subject. According to special relativity, anything that can travel faster than light will move backwards in time. At the same time, special relativity says that this will require infinite energy.
Light Travels At What Speed
Faster-than-light communication and travel (also superluminal or FTL) refers to the propagation of information or matter faster than the speed of light. In the theory of special relativity, particles (which have mass) with subluminal speed require infinite energy to accelerate to the speed of light, although special relativity does not prevent the existence of particles that travel faster than the speed of light at all times.
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On the other hand, what some physicists call “apparent” or “effective” FTL is the hypothesis that an unusually distorted region of space-time can allow matter to reach places far faster than it would take light on a “normal” path. (although it still flows subluminally through the warped area).
FTL seems to be excluded by general relativity. Examples of visible FTL proposals are the Alcubierre drive and a walkable wormhole, although the physical feasibility of this solution is uncertain.
Key features of the faster-than-light travel app for time control and time travel are presented in the image below. This is followed by a more detailed description of the effect below.
Outside of mainstream physics, others have speculated about the mechanism that can allow FTL travel to be achieved, often relying on new physics conjectures of their own invention, but their ideas have not gained significant acceptance in the physical research community. Fictional depictions of superluminal travel and the mechanisms for achieving it are also staples of the science fiction genre.
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In the context of this article, FTL transmits information or matter faster than c, a constant equal to the speed of light in a vacuum, 299, 792, 458 meters per second, or about 186, 282 miles per second. This is not the same as traveling faster than light, since:
Light travels at a speed of c/n if it is not in a vacuum, but it travels through a medium with a refractive index = n (causing refraction), and in some materials other particles can travel faster than c/n (but always slower than c), leading to Cherenkov radiation.
None of these phenomena violates special relativity or creates problems of causality, and thus does not qualify as FTL as described here.
Faster than light communication is, from Einstein’s theory of relativity, equal to time travel. According to Einstein’s theory of special relativity, what we measure as the speed of light in a vacuum is actually a basic physical constant c. This means that all observers, regardless of their relative velocity, will always measure a zero-mass particle as a photon traveling at c in a vacuum. This result means that the measurements of time and speed in different frames are not related only by a constant change, but are related by the Poincaré transformation. This transformation has important implications:
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The relativistic momentum of massive particles increases with speed in such a way that at the speed of light an object will have infinite momentum.
To accelerate an object of non-zero rest mass to c will require infinite time with any finite acceleration, or infinite acceleration for a finite amount of time.
However, such acceleration requires infinite energy. Going through the speed of light in a homogeneous space will therefore require more than infinite energy, which is not generally considered a wise assumption.
Some observers with relative sub-light motions disagree as to which of the two events separated by a spatial interval is the first. In other words, any journey that is faster than light will be seen as a journey back in time in some other, equally valid reference frame, or must consider a speculative hypothesis about the possibility of Lorentz violation on the currently unobserved scale (eg Planck). scale). So any theory that allows for “true” FTL must also deal with time travel and all its associated paradoxes, or else assume that Lorentz invariance is a symmetry of the statistical properties of thermodynamics (hence the symmetry is broken on currently unobservable scales).
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While Special and General Relativity does not allow superluminal speed in place, non-local means may be possible, which means that it flows with space instead of moving through space.
There is a way that does not violate relativity. Slip String Drive by Andrew L. Bender. Bender proposed to travel by completely isolating a region of space-time from the rest of our universe using Einstein’s gravitational waves. These space-time compression waves are produced by the ship, which emits them from its body in all directions until it is completely isolated from the rest of our universe. Then, by releasing a gravitational wave behind the ship, it stretches its isolated bubble into an egg shape, causing space-time to contract irregularly in the bubble, propelling the craft forward at speeds beyond those limited by relativity. Time flows normally in the isolated region, eliminating the possibility of paradoxes or time travel.
This option is especially popular in science fiction. However, strong empirical and theoretical evidence supports Einstein’s theory of special relativity as the correct description of high-speed motion, which generalizes the more familiar Galilean relativity, which is actually an approach to conventional speeds (less than c). Similarly, general relativity is an experimentally supported and verified theory of gravity, except in the very high energy density regime at short distances, where a quantum theory of gravity is needed. Special relativity, however, is easily incorporated into quantum field theory. Therefore, even in the broad context of general relativity and quantum mechanics, conventional acceleration from subluminal to superluminal speed is not possible.
Einstein’s equation of special relativity postulates that the speed of light in a vacuum is invariant in an inertial frame. That is, it will be the same from any reference frame moving at a constant speed. The equation does not specify a specific value for the speed of light, which is an experimentally determined quantity for a fixed unit of length. Since 1983, the unit of length (meter) has been defined with the speed of light.
Light Travels With A Speed Of 2xx 10^(8)ms^( 1) In Crown Glass Of Refractive Index 1.5. What Is The Speed Of Light In Dense Flint Glass Of Refractive Index 1.8 ?
Experimental determinations are made in vacuum. However, the vacuum we know is not the only possible vacuum that can exist. vacuum has energy associated with it, called vacuum energy. This vacuum energy may be converted in some cases. When the vacuum energy is lowered, the light itself is expected to go faster than the standard value of “c”. This is known as the Scharnhorst effect. Such a vacuum can be produced by placing two perfectly smooth metal plates together at a distance of close atomic diameter. This is called a Casimir vacuum. Calculations show that light will be faster in a vacuum for example by a small amount: a photon traveling between two plates of 1 micrometer will increase the speed of the photon by about one part in 1036 only. Therefore, there has been no experiment. prediction verification. A recent analysis has argued that the Scharnhorst effect cannot be used to send information backward in time with a single set of dishes since the remaining frame of the dish defines the “preferred frame” for FTL signaling. However, with several pairs of plates moving towards each other, the authors state that they do not have an argument that can “guarantee the total absence of causality violations”, and propose Hawking’s speculative timeline protection conjecture that suggests that virtual particle feedback loops create. . “an irrepressible singularity in the renormalized quantum stress energy” at the limit of a potential time machine, thus requiring a theory of quantum gravity to analyze it. Other authors argue that Scharnhorst’s original analysis seemed to show the possibility of a signal faster than c involved approximations that may be wrong, so it is not clear whether this effect can actually increase the speed of the signal.
Physicists Günter Nimtz and Alfons Stahlhofen, from the University of Koblenz, claim to have broken relativity by experimentally sending photons faster than the speed of light. They said they conducted an experiment in which microwave photons – relatively low-energy packets of light – traveled “instantaneous” between a pair of prisms that had been moved up to 3 ft, using a phenomenon known as quantum tunneling. Nimtz told New Scientist magazine: “At the moment, this is the only violation of special relativity that I know of.” However, other physicists say that this phenomenon does not allow information to be transmitted faster than light. Aephraim Steinberg, an expert in quantum optics at the University of Toronto, Canada, uses the analogy of a train that travels from Chicago to New York, but leaves a carriage at each station along the way, so the train moves forward at each stage; In this way, the speed of the center of the train exceeds the speed of the individual cars.
Another approach is to accept special relativity, but postulate that mechanisms allowed by general relativity (eg wormholes) allow travel between two points without
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