Thursday, November 3, 2011

FTL Neutrinos and the Fine Structure Constant

Hi again,

It looks like the fine structure constant ain't so constant.  The fine structure constant is a pure number of about 1/137 that was thought to be a fundamental constant.  It's the ratio between the energy needed to overcome electrostatic repulsion between two electrons a distance d apart and the energy of a photon of wavelength 2 pi d.  Chemistry is all about the energies involving electrons and light, so the fine structure constant pops up a lot in quite a few fields.  The fine structure constant depends on the charge of the electron, the speed of light in a vacuum and Plank's constant, so as long as all these are in fact constant, their ratio will be a universal.

This past Hallowe'en, however, Physical Review Letters published a highly-confirmed yet still extremely controversial paper showing that in old galaxies, the fine structure constant is higher in older galaxies.  There are only three possible causes; one of them must be true:

  1. The charge on the electron is larger in older galaxies
  2. The speed of light is smaller in older galaxies
  3. Plank's constant is smaller in older galaxies.
None of these choices are all that appetizing, but #2 is consistent with the idea of my previous post that there's a particle field we haven't found yet that's slowing down photons a bit. As a nice bonus, the order of magnitude of the change in the fine structure constant observed is pretty close to the order of magnitude of the factor of the photon slowdown seen in the OPERA experiment.

These thoughts are still just tantalizing ideas, and there probably isn't a connection.  Drop me a line if you have ideas about this!



Monday, October 31, 2011

FTL Neutrino Predictions

I thought I'd jot down my ideas about the recent OPERA superluminal neutrinos at CERN.  In case you hadn't heard, the experiment found neutrinos that (as far as they can tell) move slightly faster than the speed of light.

If correct, this is a big deal, since "faster than light" in one reference frame means "back in time" in another.  Being able to send information back in time would lead to implausible, crazy new technology.

My best guess as to what's going on is that there’s a systematic error in OPERA we haven’t found yet.
My second best guess: light actually travels a little slower than c, at least around Earth. This could be due to interaction with some unknown particle cloud that’s consistently uniform and has a refractive index of 1.0002.

No, this isn’t the aether, and this isn’t experimentally contradicted by the fact that the speed of light doesn’t change as the Earth changes velocity through this field. Just as the speed of light through a moving glass rod isn’t greater or smaller than through a still glass rod (neglecting dispersion, which comes into play as the Doppler-shifted frequency of light causes n to change slightly), moving through this weakly-interacting particle background doesn’t change the observed velocity of light, unless the medium is dispersive. A good assumption would be the medium isn't noticeably dispersive: whatever transitions the light interacts with are of such high energy that photons we generate all look about the same, and dispersion isn’t measurable.

Heck, the medium could even be dark matter. This hypothesis solves a bunch of problems, like why the neutrinos from the 1987A supernova were coincident with (and not before) the photons. Under this hypothesis, the photons traveling though deep interstellar space would not be slowed by the presumably rarefied dark matter there.

Like I said, my money’s still on the possibility that there’s a systematic experimental error at OPERA. However, I find the idea of a vacuum/dark matter refractive index a lot more palatable than particles that violate causality. I haven’t yet heard a good reason to discredit this idea, so I thought I’d post it.
Background: I have an honours physics undergrad degree, but I’m now a neuroscientist. None of my colleagues are capable of evaluating this idea; if it’s rubbish please don’t hesitate to point out why.