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danR said:Did anyone look for a signal four years earlier? Did a small, separate class of neutrino-component of the supernova emission behave differently from the rest of the pack?
See #237 for one set of arguments on this.
The discussion centers around the claim made by a CERN team regarding the measurement of neutrinos traveling faster than the speed of light. Participants explore the implications of this claim for established theories such as Special Relativity (SR) and Quantum Electrodynamics (QED), as well as the methodologies used to obtain these measurements. The conversation includes both theoretical interpretations and practical concerns regarding measurement accuracy.
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danR said:Did anyone look for a signal four years earlier? Did a small, separate class of neutrino-component of the supernova emission behave differently from the rest of the pack?
PAllen said:See #237 for one set of arguments on this.
danR said:This may be 'overly speculative', or already addressed, but assuming the result to stand, is the measured c in a real vacuum, the same as what it would be in an absolute vacuum devoid of zero-point fluctuating electromagnetic fields that would minutely reduce the propagation of light, analogously to the impedance of light through the electromagnetic fields always present in matter?
Neutrinos would not see any impedance, neither through matter nor in vacuo.
Even leaving aside zero-point fluctuations, empty space is not empty of electromagnetic noise, hence field fluctuations, from all manner of sources. If not a factor, I assume both sorts of things have been long accounted for in theoretical considerations of the value of c. Perhaps someone would know that.
Parlyne said:Short answer: Quantum field theory says "no."
Longer answer: In QFT the effect of vacuum fluctuations on the free propagation of a particle show up either as corrections to the particle's mass or as a rescaling of the field that the particle is an excitation of. The later case won't actually affect the propagation speed (for a particular energy); so, it's only necessary to look at the mass corrections. The thing is, for a gauge boson (or, for that matter, for a fermion) the mass corrections are proportional to the "bare" mass (that is, the mass that you'd see if there were no screening due to the corrections). This means, in particular, that quantum corrections cannot give mass to an otherwise massless particle. In other words, vacuum fluctuations will not affect the propagation speed of a massless particle.
Now, we can certainly consider the possibility that photons are actually massive; but, that actually leads to a different problem. Massive particles have energy-dependent speed; and, we've measured the speed of light (directly or indirectly) over more than 15 orders of magnitude in photon energy and not seen deviation. In fact, this lack of energy (or, more directly, frequency) dependence is the best reason to think that what we've measured really is the speed of light in a vacuum, since any physical medium has a frequency-dependent index of refraction, leading to frequency dependence in the speed of light through the medium.
Finally, the presence of other EM radiation is space is basically irrelevant, since light obeys the principle of superposition (well, up to highly suppressed corrections due to fermion loop diagrams).
Parlyne said:The SN1987a neutrino burst wasn't the sort of event that would have spent decades hiding in the data until someone went hunting for it. (You can see reproductions of the original data in this iop pdf about the event: iopscience.iop.org/1742-6596/120/7/.../jpconf8_120_072001.pdf[/URL].) It's hard to imagine that an earlier but related burst could have been totally overlooked, even if one of the detectors involved in 1987 wasn't online yet.[/QUOTE]
It would be overlooked until someone came up with some weird data that there might have been an appetizer 4 years previous to the main course. I'm not looking for pizza before I order it.
And until CERN, no one would have any idea when to look for a signal. There could have been all kinds of random or significant bumps or spikes from 1980, say, to 1987. Now there's a place to look for one. Finding 'one' would not prove anything, of course. I'm just wondering if any did, in fact look; because the 'prior to 1987a' argument came up within a day or two on SA comments-section. It's not a new discussion, but I haven't seen an "OK, we looked, there's nothing there."
But I'll check that URL.
Edit: link asks the file be prefixed with '%PDF-', but that's not getting me there.
danR said:It would be overlooked until someone came up with some weird data that there might have been an appetizer 4 years previous to the main course. I'm not looking for pizza before I order it.
And until CERN, no one would have any idea when to look for a signal. There could have been all kinds of random or significant bumps or spikes from 1980, say, to 1987. Now there's a place to look for one. Finding 'one' would not prove anything, of course. I'm just wondering if any did, in fact look; because the 'prior to 1987a' argument came up within a day or two on SA comments-section. It's not a new discussion, but I haven't seen an "OK, we looked, there's nothing there."
But I'll check that URL.
Edit: link asks the file be prefixed with '%PDF-', but that's not getting me there.
danR said:It would be overlooked until someone came up with some weird data that there might have been an appetizer 4 years previous to the main course. I'm not looking for pizza before I order it.
And until CERN, no one would have any idea when to look for a signal. There could have been all kinds of random or significant bumps or spikes from 1980, say, to 1987. Now there's a place to look for one. Finding 'one' would not prove anything, of course. I'm just wondering if any did, in fact look; because the 'prior to 1987a' argument came up within a day or two on SA comments-section. It's not a new discussion, but I haven't seen an "OK, we looked, there's nothing there."
But I'll check that URL.
Edit: link asks the file be prefixed with '%PDF-', but that's not getting me there.
On what do you base large quantities?Parlyne said:The point I was trying to make is that the signal identified as being from SN1987a was so huge that no one would have missed it once they were looking at the data. Had anything comparable shown up several years earlier, it similarly would not have been missed.
Parlyne said:The point I was trying to make is that the signal identified as being from SN1987a was so huge that no one would have missed it once they were looking at the data. Had anything comparable shown up several years earlier, it similarly would not have been missed.
Passionflower said:On what do you base large quantities?
For all intents and purposes the hypothetical ftl neutrinos might come at very low rates.
danR said:Perhaps I misunderstand those discussions, or some of them were culled out in the thread housecleaning.
#237 seemed to discuss a separate high-energy event. I'm wondering if (for some delete-worthing speculative reasoning) SN1987a spat out 2 different type/energy neutrino components, from, perhaps, two different production mechanisms in the same detonation, either simultaneously, or closely sequential (<2 minute, say).
Obviously the posited 'superluminal' neutrino packet will have no accompanying light signal. That would come substantially at the same time as the main, and recorded, light/neutrino group.
We can't ask someone to look for something when EM has not heralded it, of course. Does someone keep records of neutrino events and spikes? Is there a spike buried in the historical data somewhere around 4 years before SN1987a? Without knowing, the CERN question is not answered by the supernova.
Otherwise it's rather like the drunk looking for his keys only under the proverbial lamppost.
"Is that where you lost them?"
"No, but the light is better here."
PAllen said:The issue is you got a strong neutrino burst observed at time t0 (coincidentally with light from the SN). If these neutrinos arrive 3-4 years before light from the event producing them, the the event should be seen 3-4 years later optically. This would not have been missed because people were on the look (and always are) optically. So, to believe an alternative explanation than the normal one for SN, you must believe in both remarkable coincidence (very rare neutrino event timed to arrive same time as light from SN) + ineptitude of astronomers (to not see later light from this event).
This argument is based on a key assumption stated therein (#237). You can reject it if you want:
Any event producing intense neutrino burst will also produce intense EM radiation.
From what I've seen, the theorists playing with "what if it's true", do not reject this assumption. Instead they reconcile the SN either with an energy threshold effect (the SN neutrinos were order 1000x less energetic than the OPERA ones), or a matter based effect (neutrinos travel faster in matter), or a 'jump start' effect, where neutrinos only travel fast for a brief time after emission (which may be combined with an energy threshold as well).
kikokoko said:about supernova SN1987A:
according to FTL data from CERN, SN1987A neutrinos
should arrive about 4 years before light
1987-4 = 1983
Of the three neutrino observatories that saw neutrinos from SN1987a,
IMB and Baksan detectors were active since 1982
So, if neutrinos had arrived in 1983,
they would certainly have been detected,
since the burst of the supernova was very evident.
All historical data were scrutinised, and nothing appears in publication
lalbatros said:A simple analysis gives no chance at all for the OPERA result to be relevant.
You can find it in this arXiv paper:
http://arxiv.org/PS_cache/arxiv/pdf/1110/1110.5275v1.pdf
Have a look at fig 4 from this paper:
[PLAIN]http://img543.imageshack.us/img543/3149/operadelays.jpg
Can you guess which of the red or blue curves isthe OPERA best fit?
If you can't make your choice, then this probably indicates the OPERA result is irrelevant.
tmfs10 said:Hmm...are those graphs for one beam or for all the beams that were collected for the final result?
I do agree though that the statistical analysis is the most likely place for an error followed by the GPS clock synchronization.
The next few weeks should happily settle the former.
PAllen said:... or a 'jump start' effect, where neutrinos only travel fast for a brief time after emission (which may be combined with an energy threshold as well).
AncientCoder said:Programming/systems background(40+ years) so this is way outside of my field, although extremely interesting!
Since the OPERA experiment is designed to test/capture the rare
http://public.web.cern.ch/press/pressreleases/Releases2011/PR19.11E.html" , has any thought been given to the ideal that during the transformation that for a brief moment some kind of field/particle/effect/tachyon/tunneling event might have occurred that would have allowed the particle to "temporarily" seem(?) to go faster than expected?
If one travels a highway with an apparent speed, did they travel the entire highway at that speed, or did they exceed the speed limit for a certain portion, or maybe even take a shortcut?
Testing over a different distance would help clear that up, and parsing the distance might even allow the actual transformation to be captured!
ZapperZ said:...
I realize that it is often very hard to contain oneself when something this "big" is reported. But really, this is the time where we should reign in our guesses and possibilities, and let them work this out first. We could easily be discussing a non-existent issue here.
Zz.
PhysOrg.net 10/28/11 - http://www.physorg.com/news239009787.html
Scientists who threw down the gauntlet to physics by reporting particles that broke the Universe's speed limit said on Friday they were revisiting their contested experiment...
Kasavenas said CERN was making available a special form of proton beam until November 6.
The idea is to assess a modified measurement technique.
If this works, the technique will be used in a bigger, "highly important" experiment that will be carried out in April, he said.
"The idea with the new beam is to have protons that are generated in packets lasting one or two nanoseconds with a gap between each packet of 500 nanoseconds," he said.
"We will be able to measure the neutrinos one by one, but to do this we need a beam that is a hundred times less intense than the previous one."
lalbatros said:My understanding is that the Physics Forum mission is pedagogical and oriented to students.
How can it be a pedagogical aim to ask people to be patient and stop thinking, switch in the wait and see mode?
The OPERA paper contains a lot of issues that can be discussed usefully by undergraduated students, like the likelyhood analysis. I have no doubt that many young students could be helpful and make very interresting analysis of such topics. I am sure that the OPERA team could learn from them. I am sure that some people posting here here could write some enlightening paper. Such paper could solve an issue in the OPERA paper or could illustrate some concept on the basis of the OPERA experiment.
Restraining the discussion to a unique melting pot thread was an anti-pedagogical decision.
It discouraged in-depth discussions.
No doubt Feynman would have suggested the exact opposite approach.
Feynmann would have encouraged discussion and critical thinking, without restrain.
But I must concede that he would have already debunked the OPERA claim by now.
ZapperZ said:The OPERA paper has a lot of details that are missing.
Zz.
One of the main points seems to be that neutrinos are produced from higher or lower energy values.according to FTL data from CERN, SN1987A neutrinos
should arrive about 4 years before light
PatrickPowers said:One of the big problems is that FTL neutrinos should produce Cherenkov radiation that would reduce their energy. It didn't.
But that makes we wonder. Just what is the speed of light in solid rock anyway? You would think it would be less than c, but evidently not.
This also interesting me. Is it possible to explain shortly. OK, an article is written on this topic.lalbatros said:In addition to that, since neutrinos are not charged and interact very weakly, I do not see why they should emit Cherenkov radiations if they were FTL.
Once more, I do not see how such a conclusion could be based on current theories that exclude any FTL transmission.
I admit I must be lacking some background on this topic.
lalbatros said:It makes no sense to argue against an experimental FTL result by using current physics which denies FTL. The only way to disproof the FTL OPERA result is experimental.
I have no doubt that the analysis of the OPERA measurements is flawed.
My opinion is based on the same arguments of those OPERA team members that considered it too early to publish this result.
The current high-resolution measurements that are going on now might settle the question.
In addition to that, since neutrinos are not charged and interact very weakly, I do not see why they should emit Cherenkov radiations if they were FTL.
Once more, I do not see how such a conclusion could be based on current theories that exclude any FTL transmission.
I admit I must be lacking some background on this topic.