# Tag Info

## New answers tagged faster-than-light

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the would-be superluminal neutrino speed [...] The relevant comparison is between the arrival of neutrinos at a suitable detector, e.g. regarding neutrinos which had been travelling from CERN to LNGS; and the (first possible) detection of the corresponding "signal front", e.g. regarding signals due to any one neutrino bunch having been released at ...

1

The common answer is that nothing can be faster then light. If you look deep enough you will find out that the interaction between the rocket (or whatever else) and the force that is pulling or phushing it is always based on electromagnetism. Go from fuel to gas to molecules and you came at the end to the interaction between the electrons. And sometimes with ...

1

Why are the particles allowed to exceed the speed of light for other media when they are not allowed to in a vacuum? Light is represented by electromagnetic radiation which in its simpler form is mathematically described by a sine or cosine wave, classically. The classical light is built up by photons which are the quantum of electromagnetic radiation ...

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Why are the particles allowed to exceed the speed of light for other media when they are not allowed to in a vacuum? No particle can have relative speed greater than c, period. This is 'built-in' to the geometry of spacetime. But, a particle can travel faster, relative to some medium, than electromagnetic waves propagate in the same medium. Do you ...

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Cherenkov radiation is generated by charged particles which are faster than the local speed of light in an optical medium, which is always lower than the speed of light in vacuum. So if the local speed of light in an optical medium is given by c_medium = c_vacuum/n, where n is the refractive index, a particle with c>v>c_medium can generate Cherenkov ...

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How do we know that space expanded faster than a speed of light in inflation? Let us start from the beginning, on the reason that the Big Bang theory was proposed as a model for the universe. The reason was the observations that all clusters of galaxies were receding from each other. This is what happens from an explosion at the center, in three ...

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Inflation does not violate any local speed of light physics and there is no global prohibition in general relativity against spacetime points that are moving away from each other faster than the speed of light. Such spacetime points are simply not causally connected, i.e. there is no physical way to communicate between them (since light signals from one can ...

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There's nothing physically problematic with speeds, per se, that are faster than the speed of light. For example, if you quickly rotate an Earth-bound laser such that its beam crosses over the moon, the speed of the center of the beam as it travels across the moon's surface can easily be faster than $c$. There's no problem with a speed greater than $c$ in ...

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It is not possible, even in principle, to unambiguously detect a change in the speed of light over time, and this was true even before the SI units were redefined so as to give $c$ a defined value. The trouble here is that $c$ has units, and if a fundamental unitful number seems to change over time, there is always an ambiguity in whether the number is ...

3

Actually given that the first postulate says that all physical laws are the same in all inertial frames, you could replace the second postulate by the postulate: "Maxwell's equations are the physical laws for electromagnetism". From Maxwell's laws you can derive that the speed of light in vacuum has a specific, constant value, in SI units ...

2

Maxwell's theory had predicted that the speed of light varies with the speed of the observer. Initially (prior to Fitzgerald and Lorentz advancing the ad hoc length contraction hypothesis) the Michelson-Morley experiment was compatible with the assumption that the speed of light varies with the speed of the light source (as predicted by Newton's emission ...

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Einstein did not prove this postulate ; he simply asked "what if it is true?". He had very good reasons for asking that question. His efforts to answer the question challenged a whole raft of "beliefs" about time and space, none of which were based on proof either ; they were (up until then) assumed true by so-called "common sense" alone. He made ...

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The way I think of it, as a non physicist who quite likely has a few things wrong, is as follows: time actually passes slower for Alfred, and thus there is no difference in the speed of light. If you say, "Why does time pass slower for Alfred and not Bernard, after all, motion is relative, right!?" Well, this stumped me for a long time as a non-physicist, ...

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The answer is simple: Maxwell's equations. Maxwell published his electromagnetic theory in the 1860s. This generated a huge schism in physics. Maxwell's electromagnetism was in direct conflict with Newtonian mechanics. There is no allowance in Maxwell's electrodynamics for the speed of the emitter or the speed of the receiver. The speed of light is constant ...

0

Your solution to distant instant communication is indeed appealling, but it has its shortcomings. The pole vibrates and thus produces sound waves within the pole;sound ofcourse traverses at a much lesser velocity compared to light,thus what ever force is exerted by person A,it will produce sound waves which will reach B in ages(considering the ...

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