CERN team claims measurement of neutrino speed >c

kmarinas86

This still doesn't prove that you cannot have an ala carte decision concerning these experiments.

To broaden my point, and to put LET itself under possible question, the discovery of FTL travel could be interpreted as:

1) A violation of causality, and thus a violation of the physics of SR (which assumes causality).
2) A Lorentz violation, and thus a violation of SR, LET, and other Lorentzian theories.

I will concede though that, yes, you could say that Lorentz transforms, and not so much the idea of spacetime, is responsible for the notion that FTL travel implies causality violation.

I still don't agree with you gvk that FTL travel somehow inherently violates causality. That is my point. There is no reason why FTL travel should imply causality violation, especially if discovery of FTL travel raises doubt about certain physical theories from which this notion arises in the first place.

In the name of Ockham's razor, I would give up "Lorentzian physics" before I give up causality.

kmarinas86

That's not true at all. See the analysis of my previous post.

Discovering FTL travel could be interpreted as a violation of causality OR a violation of Lorentzian physics. You CAN choose one OR the other, exclusively. Causality is NOT necessarily violated by FTL travel.

lmoh

I am certainly no expert on the subject, but I can never really understand the hype about time travel if there actually were FTL neutrinos. On the one hand, people are saying that relativity is false and our physics would have to be changed, but on the other hand, people are making claims about time travel which I always assumed was based on the physics we supposedly have to change. Am I making any sense here or am I missing something?

kmarinas86

You absolutely are making sense, IMHO. This is one of those things that have disturbed me quite a bit. Even Michio Kaku himself has spread these notions simultaneously.

I think the issue comes from the fact that FTL travel would violate the standard physical interpretation of the mathematics of SR, as opposed to the mathematics of SR in of itself. Thus, the "physics" of relativity would change if FTL travel was discovered, but that doesn't mean that much of the math goes away. Scientists would likely use the mathematics of Lorentz transformations (being the "convenient" mathematical tool that it is) even after discovering FTL travel, and thus, in response to such a discovery, they would grab onto the "fantastic" notion that backwards time travel is somehow validated, rather than to the idea that Lorentzian physics is violated, for the latter does not in an obvious way offer an "exciting" hope to inspire the imagination of adventurers.

Saw

I tend to agree with you. FLT is theoretically possible subject to most unlikely conditions. Causality is a logical must you cannot do without. However, probably this thread is more focused on finding the flaw in CERN experiment. The old one is contaminated with the LET issue. It may be more adequate to start a new one.

TrickyDicky

This is obvious, that even people who are supposed to have a minimumm knowledge of relativity seem often confused about it suggests to me a FAQ devoted to clarify it might help.

DaleSpam

That is close enough to agreement for me. I don't think that the "ala carte" part of the discussion is appropriate to this thread, so I will not pursue it here and will simply encourage you and gvk to do the same.

If you wish to continue that then I encourage you to start a new thread on the topic and I will participate.

nsaspook

Timing delay errors from fiber-optic cable visual.

I built a prototype device to detect bad fiber cables using time delay changes and made a few videos to check pulse delay calibration. These changes in time delays are from only moving the fiber a very small distance from the fully locked position. The display sync is locked on the send pulse on the left, the received (delayed) pulse is on the right.

http://flic.kr/p/bmmGau

Galteeth

http://news.sciencemag.org/sciencein...ne.html?ref=hp

jambaugh

That may be giving up too much. The "idea of space-time" invokes some form of relativity principle which via Lie group deformation and stability arguments leaves either SO(4) (euclidean relativity, we can rotate 360° and travel back in time) ISO(3) (Galilean relativity) or SO(3,1) (Einstein Special Relativity). The implications rule out all but SO(3,1) given a vast amount of observational data and mathematical realities. One might argue that the constant c is incorrect but too much empirically verified evidence depends on the given value.

[For reference see Segal's work on stability of Lie groups under deformation, I have no specific citation but he showed that all semi-simple Lie groups are stable under small perturbations of their algebraic structure (when constrained to still yield a Lie group)]

It all means that Minkowski space-time is on as solid a footing as Euclidean spatial geometry, and these may only be invalidated (without wholly abandoning unified space-time) in the same way, i.e. allowing for curvature in the respective spatial or space-time geometries, i.e. invoking a form of GR.

To abandon locally Lorentzian physics would require abandoning unified space-time all-together and consider some alternative theory with preferred frames and an absolute time... and of course describe a mechanism by which we seem to see Lorentzian physics e.g. Lorentz's original notion that an aether causes slowing of clocks and shrinking of objects.

In short...
is giving up on "space-time" all together. We would have to go back to the pre-Einstein aether or something similar.

This is why I'd give long odds that any claim to FTL signals is some combination of analytical or experimental error.

jambaugh

No, you can't "tweak" SR. The "mathematics of SR in and of itself" would have to be abandoned. The mathematics of deformation of the algebra dictates that any variation of the group structure (which defines the value of c) is equivalent to a rescaling of the representation (change in t and x units). This has physical implications e.g. a gravitational field as you vary the group over space-time as in GR. If SR with the current c value is wrong it must be a.) drastically wrong and b.) there must be some additional mechanism making it appear right, and so c.) there's no reason to hold onto any relativity theory or unified space-time except aesthetic preference.

GTOM

I think the question is, can something be outside the boundaries of Lorentz transformations, or not?
Otherwise, i can rather accept LET than SR, since we learned, that space actually isnt empty, it is filled with "dark energy" (aether?).

Dickfore

Yes, this press release is one day after the following news article from Science:

BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results

dated February 22, 2012

cdux

In layman's terms is the neutrino faster than light buried by the consensus?

yuiop

Think so.

Enoy

ICARUS posted yesterday a paper where they show that neutrinos from cern to ICARUS was exactly at the light speed 299792,458 km/s :-(

http://arxiv.org/abs/1203.3433

If similar experiments, at OPERA and Fermilab later this year, finds the same result, that V-C = 0, it means that neutrinos that moves through the earth can not move faster than light inside earth (mass-densities). And in my opinion this means that aether-theory actually is finally falsified in an absolute way ! The reason for why I mean this, is that if there is an aether that light spreads through, this aether should have been "more thin / thinner" inside mass densities like the earth, and then massless particles / light-photons would have spread faster through this thinner aether inside earth ! But now that (if) it is not true that speed limit is higher inside earth, this means that an aether can NOT be real !!!!

Ryan_m_b

BBC reports slow neutrinos - http://www.bbc.co.uk/news/science-environment-17364682