OPERA Group Repeats Faster-Than-Light Neutrino Results 442
gbrumfiel writes "Earlier this year, the OPERA experiment made the extraordinary claim that they had seen neutrinos traveling faster than the speed of light. The experiment, located at Gran Sasso in Italy, saw neutrinos arrive 60 nanoseconds earlier than expected from their starting point at CERN in Switzerland. Others have doubted OPERA's claim, but in a new paper, the group reaffirms its commitment to the measurement. 'It's slightly better than the previous result,' OPERA's physics coordinator Dario Autiero told Nature News. Most members of the collaboration who didn't sign the original paper out of skepticism have now come on board. But scientists outside the group still aren't sure. 'Independent checks are the way to go,' says Rob Plunkett, co-spokesman of a rival experiment called MINOS."
Supernovas (Score:5, Interesting)
As others here noted last time this result came around, if neutrinos really travel that much faster than the speed of light, then we would have expected the neutrino burst from the 1987a supernova to arrive months, rather than hours, before the light came. Thus, I am skeptical.
Re:Supernovas (Score:5, Interesting)
Which would seem to imply that if there's an effect here, it should probably be related to neutrinos-through-matter vs neutrinos-through-vacuum. That skepticism is well advised, but it doesn't make it impossible.
Try, try again... (Score:3, Interesting)
That being said, if and when other (independent) groups can verify this claim, that will be an exciting day.
how does this fit? (Score:2, Interesting)
Photons have to travel at the speed of light because they have no mass. What if there were a way for neutrinos to have negative mass?
That's probably too freaky even for physics.
Is there a way to do some arm-waving about string theory that makes this all work?
Re:Supernovas (Score:5, Interesting)
And how much of a vacuum can you really get in this universe? With all the virtual particles popping in and out all the time. It seems you'd need to be as weakly interactive as a neutrino to avoid being slowed down just by spacetime and all it's particles kicking up all the time. Considering vacuum space is going to have something in it, I wouldn't be that amazed if neutrinos just travel at closer to actual C than light does.
Spacetime curvature (Score:5, Interesting)
if there's an effect here, it should probably be related to neutrinos-through-matter vs neutrinos-through-vacuum
That, or interaction with the gravitational field. Neutrinos from the supernova traveled through essentially flat spacetime, far from any masses.
General Relativity is Wrong (Score:5, Interesting)
Light refracting from dark matter hypothesis (Score:5, Interesting)
(Near re-post of http://slashdot.org/comments.pl?sid=2507746&cid=37936976 [slashdot.org])
OPERA shows light travels little bit slower than the fastest objects we've measured. A little while ago we heard that in galaxies far, far away, either the electric charge is larger, Plank's constant is smaller or the speed of light is smaller (http://slashdot.org/comments.pl?sid=2507746). If it's the speed of light that's smaller, the required slow-down is of the same order of magnitude as the factor by which photons are slower than neutrinos as observed by OPERA.
Here's my take. There's a field of undetected particles (dark matter?) that refract light a tiny bit, and this field was denser in the early universe. This field would not affect the apparent speed of light as an observer moves through it, just as (ignoring dispersion) light traveling through moving glass doesn't pick up the glass' motion vector (i.e. this wouldn't manifest itself as the Luminiferous aether, which is experimentally disproved). Light from the 1987A supernova would not be delayed too much relative to the neutrinos because most of the journey was through regions of space with low dark matter density.
There: three mysteries (dark matter, OPERA neutrinos and the fine structure "constant") all tied together with a bow on top. If you know more physics than I (honours undergrad) and you think I've missed something, please tear into this hypothesis, either here or on my blog: http://many-ideas.blogspot.com/2011/11/ftl-neutrinos-and-fine-structure.html [blogspot.com]. I look forward to hearing from you!
Best,
LeDopore
Re:how does this fit? (Score:5, Interesting)
1) Yes, it could, they've attempted to take that into account. The main error would be in the length of the neutrino pulse; a long pulse is easier to detect (I think ~2000 neutrinos, or perhaps even more) but it's hard to pin down a precise time. The repeat experiment used very short pulses, which are harder to detect (~20 neutrinos) but which yield much more precise timings.
2) All observations so far are suggesting that neutrinos have a positive mass (or, to be more picky, that at least two of the neutrino species have a positive mass) of the order of a tenth of an electron volt or less. (Also, I think it would involve an imaginary mass to move faster than light, at least if you want to stick within current relativity - this result would suggest we might not want to do that, though.)
3) Yes. For instance, if we're confined to a 3-brane -- basically, a three-dimensional sheet that we and everything around us is trapped on -- and neutrinos are allowed to leak slightly from the brane then little kinks and ripples in the brane will let them take short-cuts through the other seven spatial dimensions. Gravity can do the same, but the idea is that neutrinos would be more tightly trapped to the brane, while gravitons can roam freely.
Re:Supernovas (Score:5, Interesting)
OPERA measures muon neutrinos, not electron neutrinos. It's possible that only one kind travels faster than light.
Re:Supernovas (Score:5, Interesting)
Yes... but maybe we missed them. Neutrinos are really hard to detect, let alone identify the source direction. Given a non-directional, not-very-strong pulse, possibly widely distributed in time, an unknown amount of time before the supernova, which we weren't expecting, would it really be surprising to have missed it?
Re:General Relativity is Wrong (Score:5, Interesting)
Yes, maybe. My (more or less) professional opinion is that the experiment almost certainly hasn't shown this, and instead it will either turn out to be experimental error or a *demonstration* of relativity (either special or general; both affect clock rates in ways that can be significant for this experiment), but yes, it could finally be some experimental evidence against relativity. And since you're quite right in saying that general relativity is definitely "wrong" in that it's not a fundamental theory and cannot be treated as such, this shouldn't be terrifying - just very exciting.
But I'll withhold judgment for a while - I'm very sceptical about these results.
Re:Not Unique (Score:5, Interesting)
The 60 LnS thick hadron stop, and neutrinos getting to a detector 60 nS too soon is just plain suspicious.
Re:Spacetime curvature (Score:5, Interesting)
if there's an effect here, it should probably be related to neutrinos-through-matter vs neutrinos-through-vacuum
That, or interaction with the gravitational field. Neutrinos from the supernova traveled through essentially flat spacetime, far from any masses.
Neutrinos from 1987A traveled 168,000 light-years. Is there enough mass along that path even in interstellar vacuum to be the equivalent or more of going through a section of the earth?
Re:It's getting interesting (Score:2, Interesting)
I read somewhere just yesterday that a paper is out showing that FTL neutrinos would radiate away their energy Chernikov style, so if they really were FTL the Italian team wouldn't have measured the full flux in their experiments.
Supposedly this put the nail in the coffin for the FTL explanation; the OPERA group is really going out on a limb now.
Re:Years. (Score:5, Interesting)
Beside that, are all neutrino's equal?
No, sort of. There are three known "kinds" of neutrinos: electron, muon, and tauon. And they seem to randomly change from one kind to another. This is why I don't dismiss the possibility that neutrinos might travel faster than c. If they do, it wouldn't be the first completely bizarre thing about them.
Re:Supernovas (Score:5, Interesting)
That experiment you link to doesn't even have a five-sigma degree of certainty.
OPERA is more reliable as it does have at least a five-sigma degree of certainty.
You are indeed speaking out like a religious zealot.
Re:Spacetime curvature (Score:3, Interesting)
Perhaps dark matter over the distance is affecting them?
Re:Supernovas (Score:5, Interesting)
He is simply saying that these two sets of observed data seem to conflict and he believes that the data from the 1987a supernova is more reliable.
He said, "I am not just sceptical but quite openly dismissive of any claims of superluminal neutrinos."
Which means he has closed his mind to new experiments and evidence. In a later post, he then links to a blog which talks about the Supernova experiment, but even that blog had the good sense to add this:
"*Addendum* There are of course loopholes to this argument, for instance there may be higher order quantum gravity effects which violate Lorentz invariance [3]. Either way the result will be hotly debated - is it an unknown systematic error or some exciting hint at new physics?"