What Travels Faster Than What?

[coldcreation]

I heard on CNN a couple of days ago that a new test confirms that neutrinos travel faster than light. So I looked it up and found this:

 

New Tests Appear To Confirm Claim That Neutrinos Traveled Faster Than Light

 

Since the release of their preliminary paper on the Internet, several different criticisms by physicists around the world have challenged the methodology that the OPERA collaborative used to find their results. These criticisms include the effect of Earth’s gravity on the measurement of the neutrino speed, and the fact that the OPERA collaborative did not appear to take into account the time dilation inherent in the use of GPS satellites. As of the time of this writing, the paper has not been made public, so I can’t say whether these were taken into consideration in calculating these new results.

 

However, according to ScienceInsider, some of OPERA’s scientists are uneasy with the way that the new tests were carried out. For example, the detection “time window” for determining the neutrino events was about five times longer than previously indicated. Additionally, some researchers are unhappy with the fact that only a small part of the analysis being submitted for peer review has been independently checked by other scientists within the collaborative.

 

At this point, we’re probably going to have to wait for both peer review of the new results and experiments by other neutrino detectors before we know for sure whether neutrinos did travel faster than light. There are still very good reasons to be skeptical of these results for the time being. However, if the results are independently confirmed, then it’s clear that we’re entering some exciting new times for physics

 

It seems to be a new test performed by the same group: OPERA.

 

Has anyone heard of any independent confirmation yet?

 

 

CC

[coldcreation]

Well, I just found another article of interest:

 

Scientists reject rivals' light-speed claims,

Icarus physicists' study upholds Einstein's theory of relativity

 

Now a second group of scientists, part of the Icarus collaboration, has re-analysed the same beam and concluded that the particles could not have travelled faster than light speed without exhibiting a fall in energy levels, which was not detected.

 

The re-analysis of the same neutrino beam by the Icarus group of physicists is the first serious study to question the "faster-than-light" findings that have astonished and confounded scientists in equal measure. Physicists involved in the Icarus collaboration have posted the new interpretation of the Opera's results on a scientific website stating that the neutrinos would have lost discernible amounts of energy had they travelled faster than the "universal constant" of light speed – about 186,282 miles per second.

 

[...]

 

Tommaso Dorigo, a high-energy physicist at Cern who was not part of the Icarus group, said that the Icarus study is "very simple yet definitive" in refuting the almost heretical notion that sub-atomic particles can travel faster than light.

 

"The Icarus result says that the difference between the speed of neutrinos and the speed of light cannot be as large as that seen by Opera, and is certainly smaller than that by three orders of magnitude and compatible with zero," Dr Dorigo said on his blog. A definitive answer to the question of whether the Opera results hold water may have to wait until next year when scientists involved in the Minos consortium will carry out similar tests with American particle accelerators in Illinois.

 

 

EDIT> Here, I think, is the original Icarus group paper: A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS

 

Abstract: [...] We find that the neutrino energy distribution of the ICARUS events in LAr agrees with the expectations for an unperturbed spectrum of the CERN neutrino beam. Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow prediction for a weak currents analog to Cherenkov radiation. [...]

 

 

CC

[JMJones0424]

I heard on CNN a couple of days ago that a new test confirms that neutrinos travel faster than light...

 

All it seems to be a new test performed by the same group: OPERA.

 

Indeed, the test was designed to rule out possible statistical errors from their data analysis by using an extremely short beam duration.

 

A pdf copy of the report can be found here:

http://arxiv.org/abs/1109.4897

[maddog]

So the latest on the experiment that had previously discovered neutrinos going FTL turns out was nothing more

than possibly faulty wiring (lose connection) and an issue with the clock circuitry.

 

I found the derived article found in Popular Mechanics (I think) that was based on the latest

from CERN that admitted that the earlier results (conclusions) may have been a premature.

 

Not that I am not for find new things to know about. I am glad that a more simpler explanation

has been found that meets with analysis. Admittedly more testing is required to even validate

these findings. Just to be sure.

 

maddog

[phision]

" nothing more

than possibly faulty wiring (lose connection) and an issue with the clock circuitry.

 

maddog

 

TBH I was more than sceptical about FTL claim! My initial thoughts were that the geodetic data contained an error, but no-one wanted to talk about that, as it is complicated and hard to understand and therefore reasonable to over look an error. If it turns out to actually be an issue with a clock then that's just unacceptable and reeks of sensationalism!

[maddog]

If it turns out to actually be an issue with a clock then that's just unacceptable and reeks of sensationalism!

phision,

 

I am in complete agreement with you that it reeks. It is something on hindsight that not enough

checking all around was going on.

 

maddog

[coldcreation]

So the latest on the experiment that had previously discovered neutrinos going FTL turns out was nothing more

than possibly faulty wiring (lose connection) and an issue with the clock circuitry.

 

Hey Maddog. Do you have a link that discusses the "faulty wiring (lose connection) and an issue with the clock circuitry"?

 

Thanks

 

CC

[pamela]

My link

 

 

Speedy neutrinos? Not so fast. The shocking result that neutrinos apparently travelled from Switzerland to Italy faster than the speed of light may have been due to a malfunctioning fibre-optic cable, says OPERA, the Italian collaboration of physicists that made the first, surprising claim.

[bravox]

A little late to the debate but I have a question: in this experiment, how did the researchers solve the problem of synchronizing clocks? I can't imagine a way to get around that difficulty.

[coldcreation]

My link

 

Thanks Pam,

 

I must have missed your post.

 

I await further testing, and until then side with Einstein's view that nothing can travel faster than c, not even neutrinos.

 

 

CC

[CraigD]

A little late to the debate but I have a question: in this experiment, how did the researchers solve the problem of synchronizing clocks?

They used the timing signal from GPS satellites, which have very precise clocks and very precisely know positions, permitting very precise calculation of the travel time of their radio signals.

 

The suspected error described Luca Stanco of OPERA, quoted in many news articles, is due to the need to include an additional precise signal travel time calculation to compensate for the length of a fiber optic cable used to connect GPS receivers above ground with the computer deep underground in the Gran Sasso lab where the big neutrino detectors are. Although I’ve not read a detailed explanation of the problem, I gather a defect in a connection of this cable caused an additional delay in the signal not included in the OPERA team’s calculations.

[phision]

Although I’ve not read a detailed explanation of the problem, I gather a defect in a connection of this cable caused an additional delay in the signal not included in the OPERA team’s calculations.

 

These links may not be as detailed as you would like, but do sum-up the key points of the issues.

 

http://www.nature.co...article=1.10123

 

http://www.nature.co...o-claim-1.10123

[Qfwfq]

If it turns out to actually be an issue with a clock then that's just unacceptable and reeks of sensationalism!

Easy to say that but it is worth (and very very much worth) noting that those who supported publishing the paper were wanting to give anybody at large a chance of checking all the things that OPERA had been checking again and again. BTW I think the geodetic measurement was addressed very much and I don't see who prevented you from talking about it.

 

...and until then side with Einstein's view that nothing can travel faster than c, not even neutrinos.

So do I side with that, much more than I side with the view that nothing can travel faster than light. ;)

[phision]

BTW I think the geodetic measurement was addressed very much and I don't see who prevented you from talking about it.

 

Is it not true that OPERA out-sourced the geodetic survey to Università Sapienza in Rome. Which has resulted in them being presented with a set of Cartesian co-ordinates which they've simply relayed in there publications/presentations. Nowhere have I seen reference to which ellipsoid was used for these co-ordinates or by how much it varies locally to the geoid. The baseline of 731278.0 ± 0.2 m which is derived from these co-ordinates is widely mis-quoted as being anything from 728km to 732km.

 

I have also had difficulty finding anyone who can confidently explain how they managed to centre their Cartesian co-ordinates with an accuracy of ± 0.2 m, which has to be the initial step towards a baseline measurement with this accuracy using this method.

[Qfwfq]

Is it not true that OPERA out-sourced the geodetic survey to Università Sapienza in Rome.

It depends on what you mean in saying "out-sourced", note that the credentials of three of the co-authors listed on the paper is:

Area di Geodesia e Geomatica, Dipartimento di Ingegneria Civile Edile e Ambientale dell’Università di Roma Sapienza, I-00185 Roma, Italy

Whether this implies what you make of it is debatable, it looks to me like those three (G. Colosimor, M. Crespir and A. Mazzoni) were just part of the OPERA collaboration and it seems quite plausible that determining the baseline was their part. I don't see any bearing for this to have.

 

Nowhere have I seen reference to which ellipsoid was used for these co-ordinates or by how much it varies locally to the geoid. The baseline of 731278.0 ± 0.2 m which is derived from these co-ordinates is widely mis-quoted as being anything from 728km to 732km.

 

I have also had difficulty finding anyone who can confidently explain how they managed to centre their Cartesian co-ordinates with an accuracy of ± 0.2 m, which has to be the initial step towards a baseline measurement with this accuracy using this method.

I don't know where you have looked before saying this but in section 4 of their paper (Measurement of the neutrino baseline) you find impressive details and three references. Have you checked them? Would it be enough to mention ETRF2000 which they reference?

 

I don't know if there is any mistake in their geodesy but I think they give all you need if you want to check it yourself, which is exactly what they decided to publish that paper for. Did you read it before raising these objections of yours?

 

For the sake of accuracy, here is the last paragraph of their Conclusions, just before Acknowledgements:

Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.

[CraigD]

I have also had difficulty finding anyone who can confidently explain how they managed to centre their Cartesian co-ordinates with an accuracy of ± 0.2 m, which has to be the initial step towards a baseline measurement with this accuracy using this method.

I don't know where you have looked before saying this but in section 4 of their paper (Measurement of the neutrino baseline) you find impressive details and three references. Have you checked them? Would it be enough to mention ETRF2000 which they reference?

The the arxiv paper and ETRF2000 site Qfwfq mention, and their references, are technically dense for me, and I think, for phision and many reader, so here's some simpler assistance for physion’s difficulty which, while I didn’t find it in any OPERA paper or reference, seems to fit the claimed positional accuracy:

 

I assume the locations of the GPS receivers on the surface above the underground CERN and Grand Sasso facilities are determined using differential GPS, which according to sources from surveyors with whom I’ve spoken to various articles including the linked wikipedia one, can improve GPS accuracy from about 10 m to about 0.1.

 

Differential GPS in my experience is used when high accuracy is needed for tasks like laying out property lines or navigating boats close to land or hazards. I don’t understand the details of how it can be used to determine the relative position of points hundreds of km apart, such as CERN and Grand Sasso. It seems to me they must use multiple ground-to-ground correction signals, or a ground-to-satelite-to-ground signal (GNSS augmentation).

 

Understanding the details of how even basic GPS works has long be challenging for me, so I’m usually content to know enough to know that, when basic and augmented systems are engineered by people who do understand it, it works with the claimed accuracy. Though this grates against my detail-oriented nature, such trust is, for me, a necessity, as there’s just not enough time to master all the technologies on which I rely and am interested in.