Can neutrinos travel Faster Than Light

There seems to be a flurry of activity in this area. Here in Italy, they are measuring the speed of particles sent from Switzerland.

So what’s the deal here? Does this defy conventional understandings of the physics? Or is this just something that could never be measured before?

I get that the details aren’t clear yet, I’m just wondering if we expect to find FTL neutrinos, or if these results are confirmed, that physics has been turned on it’s head again.

I do not know of any expectation that neutrinos would be seen travel faster than c, so yes, that would be a pretty strong contradiction of established physics.

I’d put a moderate wager on the results not being confirmed, though.

I understand ‘electricity’ in the cord powering your computer travels much more slowly than most people would think, but if you pushed the electrons at one end of the cord you’d see an almost immediate effect at the other end (apart from the effect of your computer malfunctioning).

The text says neutrinos are so numerous that ‘many billions pass through your eye every second’ so wouldn’t this make for studying them individually quite tricky? It would certainly be a good reason for my occasional brain clouds. I’m thinking there could be some margin for error in tracking the speed of a neutrino. A distance of 700-odd kilometers doesn’t sound enough. How about an exploding star that’s many light years away?

These are man-made neutrinos with a known timing structure. In particular, the neutrinos are produced in very narrow bursts. You look at how long it takes for the burst to appear in your detector relative to when it was produced.

This was done with the neutrinos detected from supernova 1987a. Those neutrinos were measured at a speed consistent with c, and very inconsistent with the deviation reported here. However, if you are willing to allow faster-than-light travel, you should be willing to allow an energy dependence to the phenomenon, and the neutrinos from a supernova are about a hundred times lower in energy than the ones in this experiment.

A more general comment: the press release came out annoyingly far in advance of any technical information. There is no paper available yet (although I’m told it is imminent), and the seminar reporting the result at CERN isn’t until tomorrow.

The only extraterrestrial neutrino sources which have ever been detected are the Sun and Supernova 1987a. The neutrinos from 1987a arrived at darned near the same time as the light, though this is complicated by the fact that they weren’t produced at quite exactly the same time (a supernova is a process that takes tens of seconds for the really interesting parts). If you account for that, the best fit to the data seems to be neutrinos moving just slightly slower than c, consistent with them having a mass of a few eV.

Incidentally, if you take the neutrino flux from 1987a, the interaction cross-section, and the total mass of all human eyeballs, it’s likely that one or two people in the world actually saw a momentary flash from one of the neutrinos interacting with their eye.

If true, it would turn modern physics on its ear. AFAIK, there is no theory contemplated that would have FTL neutrinos.

I don’t think it will be confirmed in separate independent experiments though. I trust that they went many times over the data and the calculations, but there must be some problem with the design of the experiment.

Neutrinos are massless particles, aren’t they? So the problem of mass increasing as an object approaches lightspeed doesn’t arise?

Massed but very low mass. Depending on the type of neutrino, only a few keV or MeV, as I recall.

To clarify: “darned near the same time” here means “several hours before”. After backing those hours out of the result through whatever understanding of supernovae one can muster, the conclusion is that the travel time is consistent with c to within 95% C.L. (although the best fit point indeed happens to fall on the slower side of c).

A few eV at most. For want of slightly more lay-audience units: at least a billion times lighter than a proton, give or take.

Not even. Very probably less than 1 eV, but the value given for the upper bound varies—it’s either 0.62 eV (a figure called “robust”), 0.48 eV, or 0.2–0.4 eV, according to Goobar, Hannestad, Mortsell, Tu (2006).

What I find interesting is, there are a whole bunch of completely different experiments that measure the mass of the neutrino, and all of them have found only upper bounds, not lower bounds, but all of the upper bounds are in the same general vicinity. My suspicion is that the bounds are all fairly close to the true mass, and the experiments are all seeing weak evidence for a lower bound, too, but that nobody’s confident enough in their lower bound to publish it.

I’m fully expecting it to be some error.

But if it isn’t, is there any way for the characteristic speed c of relativity to be a little higher, with photons actually travelling slower than c, rather than at exactly c? So that it’s not the neutrinos traveling too fast, it’s photons traveling too slow?

As I write that, it doesn’t seem very likely, but it does make me wonder, how accurately is c measurable without using photon (or neutrino) speed?

I was wondering about the same thing.

It is possible that photons might have a very small but nonzero mass, in which case they would travel slightly slower than c (how much slower would depend on the energy of the photon). I think the bounds on photon mass are tight enough, though, to rule that out as an explanation for this experiment.

Assuming it’s for real, are there any practical applications? Is where you can download the paper.
I was actually going to post this here myself…

OK, for those familiar with neutrino oscillation, any chance they tunnel while oscillating?
Such as in a way to either tunnel OR lose mass during the change?

Some articles mention the possibility that neutrinos will travel faster through a medium than vacuum. Whether or not the neutrinos travel faster than the speed of light when the neutrinos are in a vacuum is what would or would not change our understanding of physics, according to these articles. I am not a rocket scientist. “Explanations” in layman’s terms in a news articles are always suspect to me

How do they measure the distance between the emitter and detector so accurately ?

One commentators take.

My biggest questions are: how soon can we expect practical applications for this; would it be possible to use neutrinos to send information in the same way we use light; and will this faster-than-light speed create time paradoxes?

I really don’t see the problem myself. If there is inherent latency sending information using light (through fiber optics), wouldn’t harnessing neutrinos in the same way just reduce that latency? Obviously these neutrinos aren’t sent backwards in time, otherwise how could they be detected at all?