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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 in vacuum (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. [25] Extensions of QED in which the photon has a mass have been considered.
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". [18] 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 ...
In theory, a large number of stages could push a vehicle arbitrarily close to the speed of light. [47] These would "burn" such light element fuels as deuterium, tritium, 3 He, 11 B, and 7 Li. Because fusion yields about 0.3–0.9% of the mass of the nuclear fuel as released energy, it is energetically more favorable than fission, which releases ...
Light waves of all frequencies travel at the same speed of light while matter wave velocity varies strongly with frequency. The relationship between frequency (proportional to energy) and wavenumber or velocity (proportional to momentum) is called a dispersion relation .
The electric and magnetic field waves in the far-field travel at the speed of light. They have a special restricted orientation and proportional magnitudes, E 0 = c 0 B 0 {\displaystyle E_{0}=c_{0}B_{0}} , which can be seen immediately from the Poynting vector .
They set a limit on the anisotropy of the speed of light resulting from the Earth's motions of Δc/c ≈ 10 −15, where Δc is the difference between the speed of light in the x- and y-directions. [33] As of 2015, optical and microwave resonator experiments have improved this limit to Δc/c ≈ 10 −18.
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.