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Imagine we were highly intelligent but blind bats, with fantastic sonar that lets us 'see' sound. To us, nothing could travel faster than the speed of sound, because we would only see a sonic boom as a all enveloping 'flash'. Even a rifle bullet impact would appear as a nearby flash, followed by a sound 'light' heading back to the shooter from the point of impact at sub mach 1.... So - our bats would build an understanding of a (very limited) universe based on nothing travelling faster than 760mph.

Following this logic, is our construct of the universe limited by the fact the stiffest medium we use to measure with is electromagnetic, so we have relativity that includes the speed limit c. as 186000 mps?

Could superluminal objects or particles be present in our universe, but we perceive them as travelling in the opposite direction at just sub-light speed - like the rifle bullets? Example - could neutrinos fit the bill?

Nick
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There is actually nothing special about light in special relativity. The parameter $c$ that enters formulas for length contraction, time dilation, mass-energy equivalence, etc, is called the speed of light for historical reasons. With the benefit of hindsight, some names that might be better are "the speed of massless particles," or "the maximal speed of causal propagation."

Anyway, special relativistic effects such as length contraction, time dilation, and mass-energy equivalence have all been measured, and to match observations the parameter $c$ that appears in the formulas for these effects needs to be $2.998... \times 10^{8}\ {\rm m\ s^{-1}}$. A consequence of special relativity -- assuming the Universe is causal (meaning that effects never proceed causes) -- is that nothing can travel faster than $c$. So, our conviction that $c$ is a universal speed limit does not come from properties of some particular time of message carrier, but from the evidence that special relativity is a good description of our Universe.

It is of course possible that special relativity is not exactly true in our Universe, in which case there would be room for particles to travel faster than $c$. But, there have been many searches for such effects, and no one has ever found any evidence that special relativity is incorrect. So, to date, special relativity is the best scientific explanation we have of experimental data in the regime where it applies, and it implies that nothing can go faster than $c$.

Andrew
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Suppose a series of bullets, all traveling at different supersonic speeds, hit a bunch of different bats. Is the bat detective bureau (using its sonar, its sense of touch, etc) not going to notice that these bats all sustain different amounts of damage, and that the amount of damage is greater than you'd expect from a bullet traveling at the speed of sound?

WillO
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Neutrinos are not superluminal.

If there were some superluminal field excitations we would need some way to detect those quanta that were traveling faster than c. This would imply something other than the electromagnetic interaction to do the detection work because electromagnetism is propagated at exactly c.

The list of fields known to exist doesn't contain any superluminals.

niels nielsen
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