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Faster-than-light (superluminal or supercausal) travel and communication are the conjectural propagation of matter or information faster than the speed of light (c). The special theory of relativity implies that only particles with zero rest mass (i.e., photons ) may travel at the speed of light, and that nothing may travel faster.
In this theory, light is described by the fundamental excitations (or quanta) of the electromagnetic field, called photons. In QED, photons are massless particles and thus, according to special relativity, they travel at the speed of light in vacuum. [24] Extensions of QED in which the photon has a mass have been considered.
The speed of light in vacuum is defined to be exactly 299 792 458 m/s ... Newton's corpuscular theory implied that light would travel faster in a denser medium, while ...
Robert Dicke, in 1957, developed a VSL theory of gravity, a theory in which (unlike general relativity) the speed of light measured locally by a free-falling observer could vary. [7] Dicke assumed that both frequencies and wavelengths could vary, which since c = ν λ {\displaystyle c=\nu \lambda } resulted in a relative change of c .
At a sufficient distance, the speed at which the beam "moves" may exceed the speed of light. The lighthouse paradox is a thought experiment in which the speed of light is apparently exceeded. The rotating beam of light from a lighthouse is imagined to be swept from one object to shine on a second object. The farther the two objects are away ...
As Farnes' theory allows a positive mass (i.e. a ship) to reach a speed equal to the speed of light, it has been dubbed "controversial". [16] If the theory is correct, which has been highly debated in the scientific literature, it would explain dark energy, dark matter, allow closed timelike curves (see time travel ), and suggest that an ...
Einstein's special theory is not the only theory that combines a form of light speed constancy with the relativity principle. A theory along the lines of that proposed by Heinrich Hertz (in 1890) [17] allows for light to be fully dragged by all objects, giving local c-constancy for all physical observers.
with v being the neutrino speed and c the speed of light. The neutrino mass m is currently estimated as being 2 eV /c², and is possibly even lower than 0.2 eV/c². According to the latter mass value and the formula for relativistic energy, relative speed differences between light and neutrinos are smaller at high energies, and should arise as ...