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Physics question regarding speed of light
Smasher
Starting to get dizzyRegistered User regular
Starting to get dizzyRegistered User regular
A few weeks ago I read an article about the recent experiment that seemed to show neutrinos going faster than the speed of light, and in the comments section someone had an interesting hypothesis. Given the relative simplicity of the hypothesis and the amount of interest the experiment generated it seems very likely that it's wrong somehow, but I can't find any holes in it. My knowledge of more advanced physics is limited, so I'm hoping people here can shed some light on it for me.
Relativity states that unimpeded light travels at a constant speed (let's call it c_limit) in all reference frames, and that nothing with mass can travel at or faster than c_limit. It's normally assumed that light in a pure vacuum is unimpeded, and thus that c_vacuum = c_limit. The hypothesis in question suggests that this is not the case because light in a vacuum is slowed by virtual particles in a manner similar to how light slows down in other media (air, glass, etc.), and thus that c_vacuum < c_limit. Meanwhile the electrically neutral neutrinos would pass through most virtual particles unimpeded, and if photons in a vacuum are sufficiently slowed by the virtual particles then c_vacuum < v_neutrinos_in_this_experiment < c_limit.
Thoughts?
Relativity states that unimpeded light travels at a constant speed (let's call it c_limit) in all reference frames, and that nothing with mass can travel at or faster than c_limit. It's normally assumed that light in a pure vacuum is unimpeded, and thus that c_vacuum = c_limit. The hypothesis in question suggests that this is not the case because light in a vacuum is slowed by virtual particles in a manner similar to how light slows down in other media (air, glass, etc.), and thus that c_vacuum < c_limit. Meanwhile the electrically neutral neutrinos would pass through most virtual particles unimpeded, and if photons in a vacuum are sufficiently slowed by the virtual particles then c_vacuum < v_neutrinos_in_this_experiment < c_limit.
Thoughts?
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I think the reason this theory getting no attention is that a similar theory (http://en.wikipedia.org/wiki/Luminiferous_aether) was around prior to Einstein's relativity which supplanted it.
I'd forgotten about that. There must be some difference though, since neutrinos go through almost everything and light doesn't.
I'm familiar with the aether theory but I don't see how it's similar to the hypothesis. Could you elaborate?
Its proposing the existence of a virtual medium to explain the properties of light? Its by no means identical but I certainly see similarities between the lines of thinking that arrive at these propositions. That's not to say of course that this means the theory's wrong, just perhaps why many physicists are reluctant to get behind it.
My problem with it is that it explains neutrino speed = constant, light speed = variable, when (to my knowledge) what we experimentally observe is that light speed= constant, neutrino speed= variable.
The reason they asked for outside help is because they weren't sure.
I think I've explained the hypothesis poorly.
I distinguish between something being conveyed by a medium, where the propagation of the effect requires the presence of the medium, and something traveling through the medium, where the effect does not require the medium in order to propagate. Sound must be conveyed by a medium (usually air, though solids or liquids work too) in order to propagate; if there's vacuum between you and the source of a sound you're not going to hear it. We know now that electromagnetic radiation (ER) does not require a medium to propagate.
Before we knew that, in the aether theory ER was thought to be conveyed by the aether, in much the same way sound is conveyed through vibrating molecules in the air (or solid/liquid). Regardless of the (in)validity of the hypothesis in question, virtual particles aren't acting as a medium through which photons travel; rather, VPs are hypothetically slowing ER down in the same way that molecules of glass slow down ER. In either case the ER isn't being conveyed by the medium (if VPs can be thought of as a medium), but rather are simply traveling through it.
The hypothesis isn't saying that c_vacuum varies, as to the best of my knowledge the density of VPs in a given volume of space is basically constant and thus has a constant effect on the speed of ER. Nor do neutrinos have a constant speed greater than c_vacuum; rather, since neutrinos have mass, their speed is dependent on the amount of kinetic energy they are given, and if you give them enough energy (as presumably happened in the experiment) you can (if the hypothesis is right) go beyond c_vacuum, but never reach or pass c_limit.
Note that the difference between c_vacuum and c_limit wouldn't have to be large; the neutrino result sets a lower bound of roughly .0025%, but it might not be much more than that. I'm unsure if any experiments sensitive enough to determine c_limit (as opposed to c_vacuum) to that degree of precision have been conducted; if they have and rule out a c_limit/c_vacuum ratio that "large" it would be good evidence against the hypothesis.
Objects with rest mass can travel with a velocity below the speed of light.
Objects with rest mass can travel with a velocity faster than the speed of light, provided they always are and always have been traveling faster than the speed of light.
It takes infinite energy to accelerate/decelerate through the speed of light.