FTL Neutrinos Explained... Maybe

Having Read Both Papers by eldavojohn · 2011-10-15 11:13 · Score: 2, Interesting

(Although I am not a physicist) I understand that this is talking about the concept of "time" from a frame of reference between the GPS satellites and the ground stations. However, the original paper's implementation did not measure time with GPS satellites (that would be silly). Instead, it used the satellites to obtain very precise distances and when they did this, they accounted for relativity. The time recording devices were atomic clocks at the locations of the facilities on the surface of the Earth. As the second article notes, they just said they did this and you assume they did it correctly. However, if they miscalculated relativity between the satellites and ground stations, it's going to be in the form of the distance being incorrectly measured -- not the actual time itself. And that distance (which would be slightly shorter than they calculated) should then result in an explanation of the nanosecond difference.

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Re:Having Read Both Papers by SoapBox17 · 2011-10-15 11:24 · Score: 2

GPS already normally accounts for relativity.... nothing new there. Base on the original paper I think it's highly unlikely they mismeasured the distances. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html
Re:Having Read Both Papers by Dan+East · 2011-10-15 11:24 · Score: 2

I don't understand this as well. Either this is simply a preexisting inaccuracy in all GPS readings due to relativity that has never been taken into consideration (highly unlikely), or there's something else going on that I don't grasp. I don't see how the neutrino motion relative to the motion of the satellites is a factor here, as no direct measurement between the two is being made in that way.
One of the things the GPS system helped prove was that relativity is real and must be accounted for in systems of that sort, otherwise accuracy will suffer. So I find it very unlikely that something that fundamental was overlooked in the GPS measurements generically.

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Re:Having Read Both Papers by MichaelSmith · 2011-10-15 11:48 · Score: 3, Funny

Maybe its because GPS understands relativity well enough to get planes to the correct runway, and cruise missiles to their target, but the people who designed it didn't anticipate measuring the speed of neutrinos.

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Re:Having Read Both Papers by flosofl · 2011-10-15 11:56 · Score: 1

I think the fact that most of us are not qualified to understand the raw data let alone the analysis, lends to believe this summary (and associated article) are vastly oversimplified.

That it's taken a relatively decent amount of time for this to come out leads me to believe that the answer is non obvious and non trivial to obtain.

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Re:Having Read Both Papers by thygate · 2011-10-15 12:32 · Score: 1

er, shut up Neil you ugly poo-faced git!
Re:Having Read Both Papers by shentino · 2011-10-15 13:09 · Score: 1

A network where big fat milliseconds are eaten up merely by the speed of light delaying things imply an uber extreme tolerance requirement.
I'd double check and see simply if error bounds are tight enough.
Re:Having Read Both Papers by ETEQ · 2011-10-15 13:13 · Score: 5, Interesting

(I *am* a physicist) Actually, the original paper *did* measure time with GPS - more to the point, they use GPS to establish a common frame between the two locations. Look at Figure 5 of the OPERA paper (http://arxiv.org/pdf/1109.4897v1).
Having said that, as other replies have noted, this kind of correction is well-understood, so while it isn't explicitly laid out as far as I can tell, it's unlikely the OPERA group screwed this up. What may well be true, though, is that there may be systemic offsets either in the GPS timing system, the implementation at Gran Sasso (they actually have a big waveguide that they run from the Earth's surface all the way to the GPS reveivers they have by their detector deep underground), or any of the myriad corrections that were needed to determine the time-of-flight baseline (although as far as I can tell they worked very hard to get this measurement right...).
It's also rather suggestive that the author of this paper has no particle physics (or even physics) credentials. So he/she probably doesn't know the OPERA collaboration's processes very well (admittedly, these details should be in the paper, but the tradition of the community is to not do that sort of detail in announcement papers like this...)
Re:Having Read Both Papers by digitig · 2011-10-15 13:25 · Score: 1

Uum, isn't the resolution that GPS can give you ridiculously low for doing physics experiments, even with access to the military-quality signal?
The civilian specification is that absolute time accuracy is +/- 100ns (95% if I recall correctly) although the system routinely achieves +/- 10ns accuracy (not least because the 100ns specification was set when only L1 was available to civilians so GPS on its own couldn't be corrected for ionospheric effects). What's more, for these experiments it's not the absolute time that matters, it's drift over a very short time that matters. In other words, standard GPS is more than good enough for the CERN experiment (and working in a known fixed location it's fairly straightforward to improve on it still further).

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Re:Having Read Both Papers by cloricus · 2011-10-15 13:36 · Score: 1

The summary uses the word 'infamous' to describe the original announcement. In my mind it could only be considered infamous if they made a simple and blatant error. As it looks to a layman they have made an error but in finding the error physics will gain some interesting knowledge it didn't have before. If the latter is true then I'd imagine this would be remembered for all the right reasons not all the wrong ones.
Would this be the case or is the physics world full of jerks?

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Re:Having Read Both Papers by Vellmont · 2011-10-15 13:39 · Score: 2

The paper doesn't claim that the distances were measured incorrectly, it claims the timing was inaccurate do to special relativity (not general relativity which another poster in this thread was confused by.
In essence, the paper makes the claim that the experiment is using GPS as a reference clock, and the reference clock (the satellite) is in motion differently, relative to the neutrino source, and detector.

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Re:Having Read Both Papers by tftp · 2011-10-15 13:42 · Score: 5, Interesting

60 ns translates into 18 meters at the speed of light. If the error was that large any car GPS device would be showing you as driving on some other street.
I was working with some high precision GPS receivers, and they can place you on the map with accuracy of a couple of centimeters. The shape of the Earth is also pretty well understood now.
One unfortunate possibility would be that the clocks are wrong. They had to move them between sites, since they weren't willing or able to synchronize them over the radio where they are (the varying propagation paths would be hard to deal with.) A more pleasing (to me) outcome would be that FTL is real.
Re:Having Read Both Papers by Man+On+Pink+Corner · 2011-10-15 14:03 · Score: 1

Not only that, but my understanding is that GPS timing was used only for time-transfer purposes, to calibrate the local cesium standards were used for the actual measurements.
The bug in the measurement, if there is one, cannot possibly be related to the use of GPS for timing.
Re:Having Read Both Papers by CharlyFoxtrot · 2011-10-15 14:08 · Score: 1

No no no, in-famous is when you're MORE than famous. This announcement is not just famous, it's IN-famous.

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Re:Having Read Both Papers by Rich0 · 2011-10-15 14:31 · Score: 1

60 ns translates into 18 meters at the speed of light. If the error was that large any car GPS device would be showing you as driving on some other street.
Not if the map is also off by 18 meters. How do they put the roads on the map in the first place? Most likely, by GPS, or whatever GPS was calibrated against when it was implemented.
I'm not qualified to judge if the paper is right, but it is very easy to get into circular reasoning when it comes to standards - deriving true standards to that level of precision is hard so lots of stuff gets derived and if anywhere on the chain something goes wrong you can get lots of results that agree and yet are all wrong. Systematic error, and all that.
Re:Having Read Both Papers by tftp · 2011-10-15 14:50 · Score: 3, Interesting

Not if the map is also off by 18 meters. How do they put the roads on the map in the first place? Most likely, by GPS, or whatever GPS was calibrated against when it was implemented.
The current datum for GPS is WGS84. Locations of many places on Earth were carefully measured for centuries, using astronomy and trigonometry. I don't know if they are accurate enough to calibrate the GPS.
A systematic, uniform error, like a translation of the entire datum, would have no effect on the OPERA experiment - however you slide or rotate the outer shell of a sphere it doesn't change the distance between two points. It would require a systematic but non-uniform error to cause this effect. I guess it is possible, since there is no explanation so far of the OPERA results. Such an error has to be location-specific and it should be invisible to the WAAS.
Re:Having Read Both Papers by mark_elf · 2011-10-15 14:58 · Score: 1

CERN has its own very accurate time product. There is a team at JPL that uses it and others to determine earth orientation. Altogether it might be the most accurate time product in the world. It's definitely more accurate than GPS and definitely available to scientists at CERN. If they were using GPS for this they are a bunch of mooks even if GPS was "good enough".
Re:Having Read Both Papers by Lexx+Greatrex · 2011-10-15 15:45 · Score: 1

This reminds me of Michelson–Morley's null result and how it took decades before Fitzgerald and Lorentz's postulations were "ratified"
by special relativity. Many people speculated that this was measurement error but I believe the problem was actually measurement
accuracy. I would go so far as to say that as we conduct experiments with ever increasing accuracy we are in effect reversing the emergent
nature of the Universe-- like looking deeper into a Mandelbrot where what is perceived at one scale is nondifferentiable at another.
Re:Having Read Both Papers by Parlyne · 2011-10-15 17:01 · Score: 1

That would be a fair point, except that the issue here isn't how well you can measure a time interval at one location. The issue is how well you can synchronize two clocks which are situated 730 km apart. GPS is actually a pretty good way of doing this because both labs can receive signals sent from some subset of the GPS satellites at any given time, giving a common reference. The actual time measurements are performed with atomic clocks at each end.
Re:Having Read Both Papers by GryMor · 2011-10-15 17:48 · Score: 2

Physics (and velocities) don't work like that, you can't simply sum them.
If, in a third reference frame, 2 objects are observed to be approaching each other at .75 c, co moving observers in the frame of either object would calculate their respective closing velocity as .96 c
The velocity addition formula is:
s = (v + u)/(1+(v*u/c^2))

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Re:Having Read Both Papers by julesh · 2011-10-15 19:28 · Score: 3, Interesting

The word "infamous" is often used by scientists to describe problems that a large number of people have attempted to solve and have failed. I suspect that this is the sense the submitter was using it in.
Re:Having Read Both Papers by Frnknstn · 2011-10-15 19:37 · Score: 1

Not that I am saying this was the cause for the discrepancy, but a uniform error COULD cause distance measurement errors, because your assumption is incorrect: the earth is very much not a sphere.

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Re:Having Read Both Papers by mburns · 2011-10-15 19:55 · Score: 1

AZSquib discovered in the paper that the cesium standard was not actually used for timing, but only to periodically reset the 100 MHz Ethernet timers to cover the drift of those crystals. http://blog.vixra.org/2011/09/19/can-neutrinos-be-superluminal/#comment-11088

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Re:Having Read Both Papers by Patch86 · 2011-10-15 22:08 · Score: 1

Unless you believe that map-making started with GPS in 1994, then obviously not.
Most map making is done with aerial photographs mixed with good-old-fashioned triangulation-based surveying, which is then reconciled with GPS. The error ratios in GPS are well understood, as the system has been used to check against other methods in this way almost continuously since it came online. If GPS positioning was throwing up 18 metre errors left and right it would have been noticed many many times.
Re:Having Read Both Papers by ultranova · 2011-10-16 04:19 · Score: 1

the earth is very much not a sphere.

According to Wikipedia, the maximum distance from Earth's center is at the summit of Chimborazo, 6,384.4 kilometers from center. The lowest is the floor of the Arctic Ocean, 6,352.8 from the center. This makes for a difference of 31.6 kilometers. Dividing this difference with either of these - or any of the various mean radiuses in the linked page - gets a deviation of less than 0.5 percent from a perfect sphere.
In other words, Earth is very much a sphere.

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Re:Having Read Both Papers by tftp · 2011-10-16 06:41 · Score: 1

I might be within a millimeter on all of my measurements, but over time that error propagates, because I have no way to do triangulation on a point 100 miles away due to the curvature of the Earth.
During the triangulation you establish a network of reference points. All angles and all distances between those calculated locations should add up. If you started at A and surveyed paths to B and C, you can now start at B and independently derive the location of C. It should match the one determined earlier. If it does not then you made a mistake somewhere.
Re:Having Read Both Papers by Man+On+Pink+Corner · 2011-10-16 12:26 · Score: 1

OK, I agree, that's interesting, and disturbing as all hell.
Re:Having Read Both Papers by AK+Marc · 2011-10-16 12:27 · Score: 1

The issue is how well you can synchronize two clocks which are situated 730 km apart.
And how certain you can be that they are *exactly* 730.000 km apart, because perfect timing and an error of 18m distance will get the same result.

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Re:Having Read Both Papers by BitZtream · 2011-10-16 12:31 · Score: 1

GPS accuracy and its timing accuracy is irrelevant here.
GPS was only used as a synchronization source for their own localized clocks.
It doesn't matter what the GPS time is, only that the two clocks are properly synchronized with each other as you're measuring a time span (time to get from emitter to collector)
There error could occur if the syncronization signal was not adjusted for the satellites relativstic movement (speed relative to receiving stations) and distance to the stations.
Relativistic effects should be handled fairly automatically using the phase shift in the GPS signal itself as part of the standard GPS maths that the equipment goes through. Second you have to take into account the position of the sat relative to the ground stations, and this is the easiest place for the error to occur.
Its been said elsewhere in this thread that 60ns is 18 meters at the speed of light (I assume thats correct, too lazy to look) and that that distance would be a noticeable error they would have caught in their calculations as they know the location of the ground stations accurately, which I agree with.
What would be hard to detect and compensate for at the accuracies required is the minute errors in the flight path of the sat. Its EASY for a sat to end up off 9 meters, which would be easy to not notice if you're only using GPS for a sync signal and assuming that your satellite almanac is accurate.
I find that to be unlikely as they repeated the experiment something like 15k times if I recall correctly, which makes it unlikely the error stayed consistent across the entire test period.
It would seem that if it was a sync timing issue, we wouldn't all be reading 'FTL neutrinos explained ... Maybe', it'd be fairly easy to spot, even in something this complex, the math for the timing isn't THAT complex. I'm not saying I can do it in my head or anything, but these guys are a little more advanced than I.

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Re:Having Read Both Papers by mpoulton · 2011-10-16 20:49 · Score: 1

Ie if a obsticle traveling .75 C is headed directly towards 2 observers also traveling at .75 C towards it. Those 2 observers could be a constant distance apart, and observe the time the obsticle passed each observer, divide by distance between observers and record a speed of 1.5C.
Actually not. The observed speed would be closer to 0.96C. There is no circumstance under which an observer can measure a speed in excess of C compared to any other object. This is the essence of special relativity. Time dilation and length contraction ensure that the observed speed of any object relative to any other object never reaches C.

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Re:Having Read Both Papers by xtieburn · 2011-10-17 03:39 · Score: 1

Wow, wow, your average GPS is nowhere near 1 cm accuracy it is infact around the range that the paper suggests. (It can be much less or much more depending on conditions.)
The only way this technology gets to 1cm accuracy is through a number of techniques built on to the GPS technology. WAAS can get it way down, RTK is by far the best and probably what that receiver youve mentioned works on. However, neither of these technologies are perfect nor can we be certain what technology specifically was being used on this experiment and if we assume they are using top level stuff (Which is a pretty safe bet) I am not sure what effect the ground based improvements to distance accuracy would have on the experiment timings. (Perhaps someone can elaborate on the technology and clear this up for me.)
I do still think it would be surprising if they hadnt taken in to account relativistic effects like those mentioned in the paper but it is still an important possibility to be ruled out and contrary to what multiple /. 'experts' in GPS suggest it isnt immediately ruled out by our current use of the tech. Thats not directed specifically at this post but there are an awful lot of /. posts saying 'My tomtom works fine this guys gotta be an idiot.'
(Note, no I am not an expert either but arguing the point of being ignorant gives me the edge, and I do know enough to be quite sure the accuracy of GPS can get complicated.)
Re:Having Read Both Papers by tftp · 2011-10-17 05:30 · Score: 1

Wow, wow, your average GPS is nowhere near 1 cm accuracy
If you look at the receiver that I provided the link for you will see that it is not "your average GPS" :-)
The only way this technology gets to 1cm accuracy is through a number of techniques built on to the GPS technology.
It can do it, and indeed corrections and RTK and multiple calibrated antennas - all of that is used. I worked for a large GPS manufacturer and know this for a fact. These GPS setups are actively used in construction. Builders can live with an error of a few centimeters but they can't tolerate an error of a few meters.
Re:Having Read Both Papers by gstrickler · 2011-10-17 06:06 · Score: 1

Perhaps more important than using GPS for clock synchronization is using GPS to calculate the distance between the two points. Since the two earth stations are co-moving objects at nearly identical relativistic velocities (the motion of the milky way through space, and the motion of the solar system around the milky way dwarf any differences in velocity due to the rotation of the earth and latitude or altitude of the two locations), and the motion of the GPS satellite is also dwarfed by those factors, so time synchronization should not be sufficient to explain the measurements. However, the motion of the earth through space would effect any distance calculations based upon GPS time synchronization, and that is sufficient to explain the discrepancy in the measurements.

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Re:Having Read Both Papers by treeves · 2011-10-17 06:46 · Score: 1

It's a matter of degree. In some contexts, like the one in this story about FTL neutrinos, 0.5% is huge. In other contexts, like you're making a model of the earth for a museum display, 0.5% is negligible.

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Re:Having Read Both Papers by FredFredrickson · 2011-10-20 04:01 · Score: 1

This is all nonsense if they first measured with a photon, then even measurement discrepancies would be consistent across multiple different tests. Even if they measured photons wrong, they'd measure neutrinos to be the same amount wrong, and therefore still faster than light.

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Re:Having Read Both Papers by FredFredrickson · 2011-10-20 04:10 · Score: 1

That's what I keep asking! I think the first thing they'd do is a control experiment with photons!

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Garbage by Goaway · 2011-10-15 11:22 · Score: 5, Insightful

This is another easy-to-digest paper written by someone who doesn't have the first clue about what was actually done in the experiment, trying to explain it with undergrad physics. And the press jumps on each and every one of these, no matter how bad they are.

In this case, GPS clock synchronization to nanosecond levels is regularly done in meteorology, the relativistic effects are well known and compensated for, because it wouldn't work at all if they weren't, and the synchronization was confirmed by a non-GPS method.

Absolutely nothing to see here.

Re:Garbage by Windcatcher · 2011-10-15 11:37 · Score: 2, Interesting

I won't call it "garbage", but otherwise I was thinking along similar lines (disclaimer -- I have a Master's in Physics but I haven't bothered to do the math). 60ns is an eternity in an experimental setup, and while the two sites are at different latitudes (and a straight-line three-space trajectory sends the neutrinos along a curved path in spacetime), I can't see earth's relatively weak gravity accounting for such a discrepancy. It's a curved 4-space path, but it's not *that* curved.
Re:Garbage by History's+Coming+To · 2011-10-15 11:41 · Score: 1

Agreed. If this problem existed then the GPS and satnav industries wouldn't exist because it wouldn't work.

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Re:Garbage by thygate · 2011-10-15 12:28 · Score: 1, Offtopic

I have a mint-in-the-box signed wesley crusher action figure for sale, also getting rid of my lightsaber collection, interested ?
Re:Garbage by tftp · 2011-10-15 13:57 · Score: 2

They don't automatically work out the precise timing. So if one is using GPS for timing one can't just rely on the standard GPS software and calculations for timing.
That must be bad news for manufacturers of GPS timing receivers. As matter of fact, I was working with this very receiver, it's tiny but it tells you time with 15 ns. accuracy - it is more accurate than the error in the experiment.
But as I understand the OPERA people weren't using the GPS timing, they physically moved a synchronized clock (and compensated for the effect of moving it.)
Re:Garbage by JoshuaZ · 2011-10-15 14:14 · Score: 1

Yes, sorry imprecise on my part. I mean they don't do precise timing that is universal. They can be used as I understand for short timing in any specific location but not for timing that is by itself correct for two different locations. Is that correct? In any event, I agree with you that it seems like this shouldn't be an issue given how OPERA was doing the timing.
Re:Garbage by tftp · 2011-10-15 14:32 · Score: 1

I mean they don't do precise timing that is universal. They can be used as I understand for short timing in any specific location but not for timing that is by itself correct for two different locations. Is that correct?
I'm not quite sure how to approach this. First of all, we must ignore the large relativistic effects because then the notion of common timing becomes moot (What time is now at Proxima Centauri? Well, it depends on how fast you fly the clock there.)
Once we constrain ourselves to Earth, GPS indeed provides correct time for a specific location ... any specific location. Since there is no limit on the number of GPS receivers, you can have two receivers at two locations and they will be all providing the correct time - or, shall we say, the same local time.
Re:Garbage by Ironhandx · 2011-10-15 14:51 · Score: 1

Its complete garbage.
In order for their experiment to succeed they needed extreme target accuracy, to within 1 meter. This requires they be off by 20 metres. The fact that their experiment succeeded at all for their original purpose kills this bullshit right off.
Re:Garbage by JoshuaZ · 2011-10-15 14:58 · Score: 1

Oh ok. I see where my confusion lies. Thanks.
Re:Garbage by Goaway · 2011-10-16 00:55 · Score: 1

They were using the GPS timing, but they also later confirmed it was working as expected by using a time-transfer device.
Re:Garbage by mcswell · 2011-10-16 14:20 · Score: 1

Joke, right? Neutrinos are not something you can aim.
Re:Garbage by StikyPad · 2011-10-16 21:35 · Score: 1

I believe the word you were looking for is metrology.

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Re:Garbage by Ceyx · 2011-10-16 21:37 · Score: 1

Actually you can aim them by choosing your generation process parameters correctly.
Re:Garbage by Ironhandx · 2011-10-16 23:44 · Score: 1

In addition to the other poster mentioning that it is possible with the proper experimental procedures - it was a requirement of the experiment that they be able to aim them to some extent.
The experiment could not have taken place if you were unable to aim neutrinos in some manner.
Re:Garbage by mcswell · 2011-10-17 00:44 · Score: 1

I wasn't aware of this--can you explain, or point me to a link?
Re:Garbage by mcswell · 2011-10-17 00:53 · Score: 1

Surely the need to aim them depends on how many neutrinos you produce, compared to background levels. A circular shock wave can be detected, despite its complete lack of aim.
But I would like to hear more about how one aims neutrinos (or presumably the process that produces the neutrinos gets aimed), what its accuracy is, how wide the scatter is...
Re:Garbage by Ironhandx · 2011-10-17 05:15 · Score: 1

I believe that the one they used involves producing way more neutrinos than you need and measuring the neutrinos in one exact direction from near the source and then again once it got to the italy lab.
Not necessarily aiming per say, but a version thereof that suffices for their experiment.
Since their experiment was at least partly to measure if any neutrinos were lost enroute it required a massive amount of time/distance accuracy to execute the experiment at all.
Re:Garbage by cosmicl · 2011-10-17 08:46 · Score: 1

Actually there might be. This paper suggests that the term that OPERA *might* be missing is the v*dx/c^2 factor that comes out of the Lorentz transformation equations. Suppose you synchronize two clocks next to each other using a signal from a satellite clock moving at v. (There will be a small difference in the rate of the clocks on the ground and the satellite clock, but that is small. GPS receivers can correct for this factor.) Now suppose the two synchronized clocks on the ground are moved apart so they are separated by a distance dx and not resynchronized by the satellite clock. To an observer on the ground, they will remain synchronized. To an observer on the satellite, moving more or less in the direction defined by the two clocks, the clocks will not appear synchronized. Their difference will be v*dx/c^2 where v is the velocity of the satellite, dx is the separation, and c is the speed of light. The clock "in front" as seen by the satellite will be ahead in time of the clock behind by this amount. If you plug in the typical velocity of a GPS satellite about 4000 m/s dx of 730,000 m and c = 3x10^8 m/s, you get about 30ns. Now suppose you force both clocks to be synchronized to the satellite (which is what a GPS receiver does.) Then the clocks will not be synchronized on the ground. This is not an effect that typical GPS receiver include because it depends on knowing how far away another receiver is, and on the assumption that they are using a particular satellite clock. van Elburg than argues there should be a factor of 2 included which brings the difference to 60ns which is close to the discrepancy observed. This explanation has parallels to a famous homework problem in special relativity about train robbers in a tunnel trying to trap a fast train that (at rest) is longer than the tunnel. The key to the answer is the v*dx/c^2 factor. Whether this v*dx/c^2 factor is a problem for the OPERA experiment is unclear, but possible. The detector and neutrino detectors are using GPS clocks in common mode, meaning they use satellites that both see. The explanation assumes they are only using the GPS satellites that are traveling in an orbit that is roughly parallel to the neutrino path. GPS satellites are arranged in 6 orbits, but perhaps the are using just the orbit(s) that all happen to travel roughly parallel to the CERN/detector line. It also assumes that the particular GPS receivers used do not include this effect, or the effect was not included elsewhere in the analysis. So perhaps there is something to see here.
Re:Garbage by Goaway · 2011-10-17 13:18 · Score: 1

Except they confirmed the synchronization without using any satellites, so no.

Give the researcher some credit by werepants · 2011-10-15 11:26 · Score: 1

I think it's fair to assume that the researcher would read the original paper before publishing a reaction to it, and so we can assume that this is something they didn't already cover in their initial analysis.

Relativity is tricky business, though, so it wouldn't be hard to forget to take something into account. Mass distribution between the two sites, for instance, will cause tiny changes in spacetime, which is certainly not a trivial thing to compute. Hopefully this paper and more like it will help us figure out what is really going on, although we probably won't really be able to put the matter to rest until we get some info from the repeat experiment at Fermilab.

Re:Give the researcher some credit by Goaway · 2011-10-15 11:27 · Score: 3, Insightful

I think it's fair to assume that the researcher would read the original paper before publishing a reaction to it,
The original paper does not go into detail about the procedures, because it beyond the scope of the paper. You are supposed to go look these things up for yourself, and the person who wrote this paper very clearly didn't.
Re:Give the researcher some credit by werepants · 2011-10-15 12:49 · Score: 1

The original paper does not go into detail about the procedures, because it beyond the scope of the paper. You are supposed to go look these things up for yourself, and the person who wrote this paper very clearly didn't.
Ok, to be fair I haven't read either paper. Apparently I overestimate the judgment of people who publish physics papers (on arXiv, anyway).
Re:Give the researcher some credit by Goaway · 2011-10-15 13:35 · Score: 1

The "on arXiv" part is pretty crucial. Papers there should not be taken seriously unless there is a compelling reason to trust the author.

Could this be quantum weak measurement? by Dr.+Spork · 2011-10-15 11:37 · Score: 5, Funny

In case you wondered this, check out what could be the world's greatest article abstract: Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?

Seriously, it's worth clicking, and understanding the abstract doesn't require advanced physics knowledge.

Re:Could this be quantum weak measurement? by ColdWetDog · 2011-10-15 12:46 · Score: 1

Seriously, it's worth clicking, and understanding the abstract doesn't require advanced physics knowledge.
Best. Abstract. Ever.

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Re:Could this be quantum weak measurement? by ridgecritter · 2011-10-15 14:52 · Score: 1

That abstract is a hoot! Thanks for the grin.

Re:Gut feeling by bmo · 2011-10-15 11:54 · Score: 5, Insightful

>we know jack and shit

This attitude is not helpful. This is part of the reason why biblical literalists get away with what they do. They say "hurp, we don't know anything at all, so you may as well believe Genesis word-for-word."

It is anti-reason and a cop-out.

And you cap it off with a complete misunderstanding about what a theory is.

Your post is a load of manure, sir.

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BMO

Re:I hope that this is true. by bondsbw · 2011-10-15 11:55 · Score: 1

Well, if one particle goes one direction at near C, and another particle goes the opposite direction at near C, then the they are traveling apart at nearly 2C (relative to the original frame, that is). IANAP, but that's how I understand it.

That could help your lag, because you could position an intermediate server between Earth and Mars serving as the host. Then it would only be a minimum of 1 minute 33 seconds lag, perfectly acceptable for a 1993 game of Doom. :)

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Re:I hope that this is true. by geekoid · 2011-10-15 11:57 · Score: 2

Both would be going C by any point of reference.

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Re:I hope that this is true. by MichaelSmith · 2011-10-15 11:58 · Score: 1

IIRC quantum mechanics breaks causality anyway. Interactions between coupled particles have been shown to occur instantaneously, ie, faster than light.

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Re:I hope that this is true. by Goaway · 2011-10-15 11:59 · Score: 1

Nope. They are travelling apart at slightly nearer c.

Re:I hope that this is true. by MichaelSmith · 2011-10-15 11:59 · Score: 1

Say you could cool those FTL neutrinos so that traveled much faster than light. They would be a lot more use then.

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Earth's rotation by Pollardito · 2011-10-15 12:00 · Score: 1

My money is on the fact that the true path of the beam was not from one city to the other, but from the spot where one city was when it started to where the other city was when it stopped. If the path was opposite the rotation of the earth, that'd be very slightly shorter right? Earth doesn't spin fast compared to the speed of light, but this error wasn't very large either

Re:Earth's rotation by tftp · 2011-10-15 14:19 · Score: 1

Earth is not just rotating around its axis. Earth is also rotating around the Sun, and the Sun moves on its orbit within the Galaxy, etc. etc.
Earth's orbital speed is about 30 km/s. The test distance is 730 km. Neutrinos traveled the same path in 2.4 ms. Earth during this time moved by 30 km/s * 2.4 ms = 72 meters. Since the neutrino was emitted at the speed of light, even though the source was receding, it can be interpreted as if the receiver was closer to the source than anticipated.
If the Earth's vector is not lined up with the test path then the excess time will be varying from the -150 ns to +150 ns.
This wouldn't be a problem in classical mechanics because the speed of the neutrino would be less than c and both deltas would take each other out. But since I'm not a physicist I will stop right here :-)
Re:Earth's rotation by GryMor · 2011-10-15 18:00 · Score: 1

Only relative motion matters, aka, in the inertial frame of the source when the leading edge of the beam was emitted, how much has the target moved by the time the leading edge of the beam reaches the detector.
At two points opposite each other on the equator, that distance would be less than 2.3 meters, with only 730km separating the source and target, that distance is only a few centimeters (the source and target have nearly the same velocity)

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A simple test by MichaelSmith · 2011-10-15 12:01 · Score: 1

I wonder of OPERA is receiving messages from the future now, and if so, what they say?

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Re:I hope that this is true. by Goaway · 2011-10-15 12:06 · Score: 2

No information can be transmitted, so causality is not violated.

If neutrino were faster than light... by drobety · 2011-10-15 12:09 · Score: 2

If neutrinos were faster than c, the neutrinos from SN1987A would have arrived "five years sooner," while they were measured arriving "3 hours before the dying star's light caught up" as expected...

Re:If neutrino were faster than light... by MichaelSmith · 2011-10-15 12:22 · Score: 1

Damn. Good point.

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Re:If neutrino were faster than light... by MichaelSmith · 2011-10-15 12:29 · Score: 1

But then the article doesn't say if anybody was looking five years before the supernova, or if there has been any attempt to find a pulse of neutrinos that early.

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Re:If neutrino were faster than light... by Soupster · 2011-10-15 16:20 · Score: 2

If neutrinos were faster than c, the neutrinos from SN1987A would have arrived "five years sooner," while they were measured arriving "3 hours before the dying star's light caught up" as expected...
You are making the assumption that the neutrinos from SN1987A were excited to the same or higher energy level by the supernova that the LHC neutrinos were excited to. My bet is this assumption is false.
Re:If neutrino were faster than light... by Parlyne · 2011-10-15 17:46 · Score: 1

I think the actual number is more like a little under 4 years. Either way, though, two of the three detectors that detected the SN1987A burst were operating during that time period. A more important point, though, is the sheer improbability of those three experiments detecting 24 neutrinos in a span of 13 seconds. The detection at KamiokaNDE alone had a probability of occurring randomly of no greater than 0.00000057%.

The named papers wrong by physburn · 2011-10-15 12:09 · Score: 1

Sorry, but the suggesting that CERN and OPERA clocks are the GPS satellites and adjusting for there speed is just wrong. CERN and OPERA used GPS for accurate geophysics and timing measurement but have they own synchronized clocks in the earths frame. The fasting than light measurement isn't going to go away that easily.

My personnel solution is that neutrinos feel a fifth force (many at low energy), and this fifth force as left a enough binding energy for the Scarnhorst effect to increase the speed of there force carrier above the speed of light. see axitronics for details.

bogus by bcrowell · 2011-10-15 12:10 · Score: 5, Interesting

It's bogus. (Yes, I am a physicist.) OPERA used portable atomic clocks, which were moved to the the two labs and then synchronized via GPS (see this article). GPS thoroughly incorporates general relativity (which includes special relativity). It has incorporated GR ever since it was first built, because if it didn't, it wouldn't work. At all. No, not even well enough for hiking and driving. Here is a review article on relativity in GPS. GPS uses coordinates called Earth-Centered Inertial (ECI). These are coordinates (t,r,theta,phi), where the spatial coordinates are spherical coordinates that rotate along with the earth, and t is the time coordinate of a hypothetical observer in a nonrotating frame at rest relative to the center of the earth. General relativity is completely agnostic about what coordinate system you use, so this choice of a coordinate system is not a choice that has any physical significance; it's just a bookkeeping thing. Van Elburg assumes that GPS was constructed by people who didn't understand relativity, and therefore GPS times need to be corrected for relativistic effects. That's just completely wrong.

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Re:bogus by ColdWetDog · 2011-10-15 12:54 · Score: 1

Thank you. Thank you. Nice article.
Now, to try and read it without head asploding.

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Re:bogus by bcrowell · 2011-10-16 04:54 · Score: 1

Looking back at this post, I notice one thing I said that was an oversimplification. The ECI t coordinate does differ from a time coordinate synchronized in the frame of the labs, which are rotating with the earth. However, the relative velocity involved is the velocity of the earth's rotation, not the much larger orbital velocity of the satellites, which is what van Elburg assumed was relevant. The effect is vx/c^2, where x is the east-west distance between the two labs. If you work it out, it's less than one ns, which is far too small to be relevant. (I assume OPERA did understand this issue and take it into account, but even if they hadn't, it would be far too small to explain the effect.)

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Re:bogus by drcesteffen · 2011-10-16 14:38 · Score: 1

Per the referenced article at http://relativity.livingreviews.org/Articles/lrr-2003-1/ the GPS handles the relativistic effects but the European Space agency alternative to GPS "GALILEO project [25] states that relativistic corrections will be the responsibility of the users (that is, the receivers)" so some GPS analogs don't take into account the relativistic effects. Assuming they used GPS and not GALILEO, the relativistic effect seems not to be the problem. The documentation for my car/marine GPS unit says that it does not work well around tall trees or tall buildings. I would assume mountains might cause problems too. I also understand that humidity or air pressure changes can have an effect.
Re:bogus by bcrowell · 2011-10-17 12:10 · Score: 1

When you use a surveying-quality GPS in a fixed position over a long period, it is much, much more accurate than a hand-held or car-mounted GPS. It has two channels, which allows it to correct for ionospheric distortion. Echoes from cliffs and tall buildings cause intermittent errors on hand-held GPS, when the satellite geometry is unfavorable, but I don't think they're an issue here. There is a graph in the OPERA group's paper where they show the GPS detecting the 6-cm shift when an earthquake occurred in Italy.

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Re:bogus by cneily · 2011-10-24 12:05 · Score: 1

Well I am (or was) a GPS expert, having participated in the development of the first receiver software. Bcrowell is correct in every detail. As he says the corrections are completely deterministic; the satellite clocks are controlled to run at the rate they would if stationary on the equi-potential geoid, a time-varying correction since the satellite orbits decay away from circular after a while. The special and general effects are comparable in magnitude and first order in the system operation (if not compensated). It was overkill, but I had the honor of coding the platform-dependent relativistic corrections (e.g., a supersonic maneuvering F4): one line of FORTRAN (yes, we had fire in my village in those days). To establish a common time reference at different locations there are various other error sources, measurable (iono delay), or model-based (tropo delay), cables, etc., but I assume these have long since been wrung out. As Newton said "I frame no hypothesis...", but I doubt if the problem is GPS-related. It's too simple.

Highly Doubtful by Roger+W+Moore · 2011-10-15 12:32 · Score: 5, Interesting

Maybe its because GPS understands relativity well enough to get planes to the correct runway...

GPS understands relativity well enough to require General Relativistic corrections. This paper suggests that the GPS clock is inaccurate and suffers a lag based on location which, since GPS requires accurate timing to pinpoint your location a 64ns time difference would put you 20m off your correct location. In addition the author uses a very simplistic model of GPS clock and satellite for getting the clock. I would also have assumed that the GPS clock is based on multiple satellites since it has to know your location to calculate the propagation delay and it does this by comparing one satellite clock to another.

However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct. In fact I'd need to hear from a GPS expert that his simplistic model is reasonable because I don't believe that it is (but then I'm not a GPS expert!).

Re:Highly Doubtful by digitig · 2011-10-15 13:05 · Score: 4, Informative

Maybe its because GPS understands relativity well enough to get planes to the correct runway...
GPS understands relativity well enough to require General Relativistic corrections. This paper suggests that the GPS clock is inaccurate and suffers a lag based on location which, since GPS requires accurate timing to pinpoint your location a 64ns time difference would put you 20m off your correct location. In addition the author uses a very simplistic model of GPS clock and satellite for getting the clock. I would also have assumed that the GPS clock is based on multiple satellites since it has to know your location to calculate the propagation delay and it does this by comparing one satellite clock to another. However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct. In fact I'd need to hear from a GPS expert that his simplistic model is reasonable because I don't believe that it is (but then I'm not a GPS expert!).
I'm not an expert either although I have worked on GPS aircraft navigation and augmentation systems. You are right that the GPS clock is based on multiple satellites. A GPS fix needs a minimum of four satellites, and the receiver triangulates position in 4-dimensions: the three spatial dimensions and time (four unknowns, four data points). What's more, those 4 will not be in the same plane (the satellites themselves form 6 orbital planes), so the bit in the article about "The orbits of these satellites are at 20.2 106 m from the earth’s surface in a fixed planes inclined 55 from the equator with an orbital period of 11 h 58 min [3]. This implies that they fly predominantly West to East when they are in view of CERN and Gran Sasso, which is roughly parallel to the line CERN-Gran Sasso" looks to me like a fundamental misunderstanding of the satellite orbits. The satellites on which a time fix is based will not all be travelling in the same direction. It is possible to use other position information as data points, and so reduce the number of satellites needed for a fix, but I'm not sure why anybody would do that when they can improve accuracy by using all visible satellites (and anyway, even if they did use a single satellite plus accurately known spatial position, the author of the paper still wouldn't know which orbital plane the satellite used was, and so wouldn't know the direction of movement).

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Re:Highly Doubtful by khallow · 2011-10-15 15:55 · Score: 1

However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...
Not every language spells photon as such. For example, Dutch, the language of the author, spells it as foton. So yes, photon is spelled "foton", just not in English.

As to the paper, the sort of error that supposedly happened with GPS, strikes me as the sort of error that would not be corrected by the system since it's not relevant to GPS's primary task, positioning to within tens of meters. It's particularly suspicious given that it is of the right size to explain the anomaly.
Re:Highly Doubtful by Q-Hack! · 2011-10-15 17:47 · Score: 1

As to the paper, the sort of error that supposedly happened with GPS, strikes me as the sort of error that would not be corrected by the system since it's not relevant to GPS's primary task, positioning to within tens of meters. It's particularly suspicious given that it is of the right size to explain the anomaly.
Not sure why you think that GPS's primary task is positioning to within tens of meters. For military and scientific research, GPS is capable of getting down to within +/- 6 inches. The article doesn't state, but I would assume they are using the far more accurate Differential GPS often referred to as DGPS.
The only time GPS was accurate to within tens of meters, was when they had the SA turned on to limit enemy use of the system. That was abandoned years ago.

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Re:Highly Doubtful by khallow · 2011-10-15 18:43 · Score: 1

Not sure why you think that GPS's primary task is positioning to within tens of meters. For military and scientific research, GPS is capable of getting down to within +/- 6 inches. The article doesn't state, but I would assume they are using the far more accurate Differential GPS often referred to as DGPS.
DGPS includes one or more local reference points and hence, isn't strictly a function of GPS. I did forget that military and certain other uses do get more accurate placement, but they don't get the accuracy of DGPS.
Re:Highly Doubtful by snowgirl · 2011-10-15 22:06 · Score: 1

However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct. In fact I'd need to hear from a GPS expert that his simplistic model is reasonable because I don't believe that it is (but then I'm not a GPS expert!).
The author is Dutch. In Dutch, it is spelled foton. You can't blame everyone for speaking English as a second language.

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Re:Highly Doubtful by Roger+W+Moore · 2011-10-16 07:17 · Score: 1

You can't blame everyone for speaking English as a second language.
No, but clearly he has either never written a paper about photons before otherwise he would know the correct spelling because the journal would catch it. This strongly suggests that he is outside his area of expertise.
Re:Highly Doubtful by tehcyder · 2011-10-16 23:49 · Score: 1

Not every language spells photon as such. For example, Dutch, the language of the author, spells it as foton [google.com]. So yes, photon is spelled "foton", just not in English.
If you write a paper in English, you use English spellings, not Dutch, Cantonese or Klingon.

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Re:Highly Doubtful by tehcyder · 2011-10-16 23:55 · Score: 1

The author is Dutch. In Dutch, it is spelled foton [wikipedia.org]. You can't blame everyone for speaking English as a second language.
Oh come on, if I wrote something in French or German (neither of which I am fluent in) and made a spelling or grammar mistake, I wouldn't use "but it's not my first language" as an excuse.

There's a difference between casual internet forum postings and actual published works.

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Re:Highly Doubtful by tehcyder · 2011-10-16 23:59 · Score: 1

However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct.
Careful with those ad-hominen arguments there, Chief, they tend to suck the credibility right out of your own arguments. There are plenty of brilliant people in the world who, for whatever reason, can't spell their way out of a wet paper bag, but in their field of expertise they have no equal.
If you can't spell, you get someone to proof read and correct it for you. In fact, even if you can spell you should get someone to proof read and correct items for publication.

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Re:Highly Doubtful by khallow · 2011-10-17 02:37 · Score: 1

If you write a paper in English, you use English spellings, not Dutch, Cantonese or Klingon.
And yet, that's completely irrelevant. Keep in mind that the original poster claimed that misspelling "photon" meant the guy didn't know what he was talking about. I merely noted that he's a foreign language speaker. So we have the possibility of a competent foreign language speaker who just hasn't mastered English.
Re:Highly Doubtful by snowgirl · 2011-10-17 13:50 · Score: 1

The author is Dutch. In Dutch, it is spelled foton [wikipedia.org]. You can't blame everyone for speaking English as a second language.
Oh come on, if I wrote something in French or German (neither of which I am fluent in) and made a spelling or grammar mistake, I wouldn't use "but it's not my first language" as an excuse.
There's a difference between casual internet forum postings and actual published works.
Right, but if you made an almost guaranteed grammatical error, you would pass it off as "not my first language". Or rather, "not one of my native languages". And yeah, I know: "if I were making a professional publication, then I would have it proofread by someone who does speak the language natively!" Yeah, and proofreaders never make mistakes, right?

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Re:Highly Doubtful by Roger+W+Moore · 2011-10-18 17:12 · Score: 1

...misspelling "photon" meant the guy didn't know what he was talking about.
I did because it shows that he has not written a scientific paper with the word 'photon' in it NOT just because be mis-spelled it.

So we have the possibility of a competent foreign language speaker who just hasn't mastered English.
...and physics. Someone who does not know how to spell photon correctly is exceedingly unlikely to have written (m)any physics papers. This is not some esoteric bit of vocabulary: in physics it is an incredibly common word. So this is likely his first, or close to his first, paper on physics and frankly the author makes such glaringly wrong assumptions about GPS that, even without the spelling problems, it is clear he is well out of his depth.

Re:I hope that this is true. by icannotthinkofaname · 2011-10-15 12:35 · Score: 1

They measured the actual difference is like 1.00001x faster, so this is of total insignificance

You're wrong. The error bars on experimental data are a statistical thing. By the very fact that their margins of error didn't allow their confidence intervals to capture the speed of light, the speeds of the neutrinos were statistically significant in their difference from (in this case, above) c for some significance level. I don't know what their level was, but it was probably .1, .05, or tighter, since these are pretty standard significance levels. That means that if all their instruments were calibrated perfectly and their calculations were all correct, there's a 90-95% chance (if the significance level is .1 or .05) that the actual speed of the neutrinos was really within the confidence interval (and so were that much faster than c).

Unless you have a different definition of significance, in which case, you should be more specific.

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Re:I hope that this is true. by bondsbw · 2011-10-15 12:36 · Score: 1

I don't think so. If a particle is traveling away from me at 185K miles per second, after 1000 seconds, it will be a distance of 185M miles. If another particle is traveling the opposite direction at the same velocity, after 1000 seconds it will be a distance of 185M miles. (All distance/time measurements in my frame.)

So in my frame, they will be 370M miles apart after 1000 seconds, and having started 0 miles apart, the delta-T is 370K mi/sec. Which is nearly 2C (372K mi/sec).

The only way to say their separation speed is less than 2C in my frame is to admit that either their distance is less than 186M miles apart after 1000 sec (in my frame), or that my measurement of time is incorrect in my own reference frame.

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Re:I hope that this is true. by Xaositecte · 2011-10-15 12:42 · Score: 2

The reason the speed of light is an unbreakable barrier is because it would take theoretically infinite energy to accelerate anything past the speed of light. It's the place in the equation where the equations break down into infinity, and we can't predict exactly what's going on.

If there's evidence that the speed of light isn't an absolute barrier, it means our current understanding of relativity is wrong.

Re:I hope that this is true. by bondsbw · 2011-10-15 12:48 · Score: 1

And to be clear, I understand the concepts of time dilation and length contraction. So I'm still acknowledging that each of those particles will, in their own frame, see the other particle leaving at a speed of less than C. They will see the distance between themselves as less than the distance I see between the two.

And this doesn't account for the time light travels back to me. That has to be accounted for and calculated as I receive the information back. It also doesn't speak for relativity of simultaneity... events from both particles that appear simultaneous with me will not appear simultaneous to each other, even accounting for the speed of information travel.

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Re:XKCD by Wolfling1 · 2011-10-15 12:51 · Score: 1

Yes. Shouldn't the explanation have come out before the findings?

Re:I hope that this is true. by Bill+Currie · 2011-10-15 12:58 · Score: 1

If there's evidence that the speed of light isn't an absolute barrier, it means our current understanding of relativity is wrong.

Not necessarily wrong, just missing some details. If our current understanding was wrong, we would have already seen all sorts of phenomena that don't fit the theory.

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Roud trip time is what counts. by Kaenneth · 2011-10-15 13:07 · Score: 1

Any possible way to setup this experiment as a round-trip, so that only one clock matters?

Re:Roud trip time is what counts. by Arrepiadd · 2011-10-17 01:08 · Score: 1

It's a late answer but I'm not here for the karma anyway... hope you get to see it.
The reason why you can't make a round trip sort of experiment is because neutrinos hardly interact with matter. They zip through the planet as if solid rock was just more vacuum. Therefore, expecting something like a mirror in the other end so that they bounce back (let's imagine we are talking about light) would be impossible, as they'd just go through said mirror. Even if you say "well, one of them will be bouncing back sooner or later" this is studied with statistically significant populations. They would need several thousand of neutrinos coming back before being able to say anything and that is not happening any time soon.
They did the experiment up to the highest standards, no one (with proper knowledge) is complaining about their setup.

Re:Whats... by shentino · 2011-10-15 13:14 · Score: 1

You aren't going to make everyone happy unless you run the government on unicorn farts instead of real money.

Someone has to foot the bill for a government that keeps it rule of law instead of rule of strongest mob with the fastest trigger fingers.

Re:I hope that this is true. by bondsbw · 2011-10-15 13:33 · Score: 1

If Alice and Bob are one light-minute apart, and they both agree to measure the state of entangled particles, and agree that Bob sends Alice his measurement immediately. Alice predicts the value Bob will send, a minute prior to receiving it, which means she knew it in the past according to the principal of causality.

Well... that's how I understand it. But this is an area that I really don't get very well... my interpretation is probably fundamentally wrong somewhere. I know that Alice couldn't send any new information. So it seems that causality wouldn't necessarily be broken, but that one could now predict certain forms of information obtained by quantum entanglement at faster-than-light speeds.

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Re:I hope that this is true. by Goaway · 2011-10-15 13:39 · Score: 2

That situation violates causality only for some definition of causality which is not useful.

What matters in causality is avoiding paradoxes. You cannot create a paradox using quantum entanglement, thus there is no problem.

The very first thing that popped in my head by modmans2ndcoming · 2011-10-15 13:40 · Score: 1

The first thing that I thought of when they announced the FTL Neutrinos was that they did not take into account the relativistic motion in their measurements.

Re:I hope that this is true. by PhunkySchtuff · 2011-10-15 13:46 · Score: 1

You don't seem to understand relativity. It's perfectly possible for the scenario you describe to happen. You shine two torches away from each other, the photons from each torch are moving at c.

Whilst the distance between them grows at a greater rate than the distance between you and either one of the photons, there's nothing special going on here. You don't see anything moving faster than c

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Best joke so far by Anonymous Coward · 2011-10-15 13:47 · Score: 4, Funny

"We don't serve faster than light neutrinos here", said the bartender. A neutrino walked into a bar.

Re:I hope that this is true. by tftp · 2011-10-15 13:52 · Score: 1

Alice predicts the value Bob will send, a minute prior to receiving it

Bob is superfluous here; he is not sending anything that Alice doesn't know. Alice can flip a coin and write the outcome down. Then she copies it on a Post-It note and sticks it to the monitor. Then she looks at it a minute later, compares with the earlier record and finds that they are identical. This only means that she sent the information into the future, which is not very unusual.

What about the Tunnel? by rudy_wayne · 2011-10-15 13:53 · Score: 1

About 3 weeks ago there was this story http://science.slashdot.org/story/11/09/25/223216/the-mythical-tunnel-between-cern-and-central-italy"> where everyone laughed at the Italian minister of Public Education and Scientific Research who issued a press release which congratulated the scientists and mentioned that Italy had funded the construction of a "tunnel between the CERN [in Geneva] and Gran Sasso [the labs in Central Italy]".

But according to this new article: "scientists created neutrinos at CERN in Geneva, and then measured how long it took them to reach a detector called OPERA, located in Italy". So what's the deal? How did those neutrinos, regardless of their speed, travel the 900 km from CERN to Italy?

Re:What about the Tunnel? by MimeticLie · 2011-10-15 14:10 · Score: 1

Are you being serious? Neutrinos travel through "solid" matter easily. There's no need for a tunnel, the particles are capable of traveling through the earth.

I could understand not knowing that the first time the story came up, but it's been awhile now. And if it was intended as a joke, it's gotten stale at this point.
Re:What about the Tunnel? by nedlohs · 2011-10-15 14:32 · Score: 3, Informative

Through the ground.
Just like you don't need to remove the air in a "tunnel" between point A and point B to send a beam of light between them, you don't need to remove the rock in a "tunnel" between point A and point B to send a beam of neutrinos between then. Of course enough air will block the light as and several hundred light years of solid rock would block the neutrinos. 900km of rock however is not going to do anything, digging a tunnel would make no difference at all.
Re:What about the Tunnel? by mestar · 2011-10-15 16:52 · Score: 1

So, what is this detector made of? How thick is it?
Re:What about the Tunnel? by FrootLoops · 2011-10-15 18:17 · Score: 1

Easy: quantum tunneling.
Re:What about the Tunnel? by julesh · 2011-10-15 19:44 · Score: 1

It's made of approximately 1,000 tonnes of lead with photodetectors dispersed through it.

Another hypothesis by Anonymous Coward · 2011-10-15 13:56 · Score: 1

I am a particle physicist. The pulse is gigantic compared to the time difference they're claiming. If there's even a tiny difference in pion production efficiency between the leading and lagging edges of each proton bunch (or, say, a difference in K-to-pi ratio), and that difference isn't properly modelled by the Monte Carlo, it will create a significant bias in the timing, which is calculated statistically. You can never know, for any neutrino, where in the bunch the progenitor proton lay, so if ones toward the front are slightly more neutrinos, it will make the group seem faster.

Re:Another hypothesis by Parlyne · 2011-10-15 17:54 · Score: 1

Two problems. First, how do you arrange for that difference? Second, what about the neutrinos on the leading edge?

LIGHT WILL REDEEM YOU!!! by ruberg_nadnerb · 2011-10-15 14:01 · Score: 1

I don't understand why they don't just shoot photons down the link to see if it is equivalent to the speed of light. Any uncompensated time dilation factors should immediately be recognized. Seems like the easiest route to disprove these time dilationists.

Re:LIGHT WILL REDEEM YOU!!! by nedlohs · 2011-10-15 14:33 · Score: 3, Informative

Photons don't make it though the 900km of rock.
Re:LIGHT WILL REDEEM YOU!!! by WildBlueYonder · 2011-10-17 08:31 · Score: 1

Unless those photons come from a moon-sized space station.
Re:LIGHT WILL REDEEM YOU!!! by nedlohs · 2011-10-17 13:20 · Score: 1

But then your detection and timing equipment might be hard to extract the results from.
Re:LIGHT WILL REDEEM YOU!!! by Marble1972 · 2011-10-18 01:39 · Score: 1

If I was drinking milk - It would have been out my nose ;)

Re:I hope that this is true. by CharlyFoxtrot · 2011-10-15 14:22 · Score: 1

Exactly, like Newtonian physics wasn't "wrong" at the time because it explained what people could observe but couldn't explain everything we could see once we could look further into space. Maybe this is us looking further.

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Re:I hope that this is true. by bondsbw · 2011-10-15 14:36 · Score: 1

Ok, but even if Alice and Bob found a way to transmit new information instantly, I'm still not seeing how a paradox could exist. Alice could send Bob a message, and Bob could calculate a response and send it back. Alice would receive the calculated response before light-speed would allow, but that wouldn't seem to violate causality by creating a paradox... from what I can tell, it would only violate the principle that nothing could travel faster than the speed of light. But instantaneous information transfer (FTL) is the supposition, therefore nothing has been proven.

I'm not trying to be difficult... seriously, just trying to get how some of these concepts aren't just circular definitions.

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Re:I hope that this is true. by Goaway · 2011-10-15 14:45 · Score: 1

The reason it seems unproblematic is that you think about the problem in regular Euclidean space. However, our universe is not Euclidean, it is (ignoring general relativity) Minkowski space. In Minkowski space, the ordering of events in spacetime is much harder to pin down. Sending a signal "faster than light" allows you to send signals back through time, causing paradoxes.

Try finding a good introduction to special relativity, it should have some thought experiments to further demonstrate how this works.

Re:I hope that this is true. by bondsbw · 2011-10-15 14:48 · Score: 1

I don't get the point of your post, or why you claim I don't understand relativity. I never claimed that anything would actually travel FTL, or that I have made some huge discovery.

You even confirmed what I did say, that it is possible to observe separation speeds of at-or-near 2C without violating relativity or the principle of invariant light speed. My post was a response to a post that assumed that I was talking about the speed of any single particle relative to another point in space... which isn't true, I was talking about separation speed of two particles in two different frames observed by a third frame.

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Re:Gut feeling by spottedkangaroo · 2011-10-15 14:51 · Score: 1

There are projects looking for changes in the constants, cosmologically speaking. It's not something they haven't thought about, it's just really hard to detect. Nobody knows if this is the case and it's surely not ruled out, nor assumed to be constant everywhere, but it surely seems to be everywhere local to us.

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Re:I hope that this is true. by PhunkySchtuff · 2011-10-15 14:54 · Score: 1

No worries then - what you say is completely correct then, you can observe the distance between two particles increasing at 2c. Somewhere in the conversation thread, I thought someone was saying that this would equate to a speed of 2c.

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Re:I hope that this is true. by Galactic+Dominator · 2011-10-15 14:57 · Score: 1

Yes, it can.

http://www.popsci.com/technology/article/2011-04/quantum-teleportation-breakthrough-could-lead-instantanous-computing

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Re:XKCD by hawguy · 2011-10-15 15:45 · Score: 1

Yes. Shouldn't the explanation have come out before the findings?

If they've really discovered FTL travel and can send information into the past, then the findings should have come out before the experiment.

Re:I hope that this is true. by Parlyne · 2011-10-15 17:18 · Score: 1

How do they both know a priori that the particles they're measuring are entangled? Put another way, the only information that exists in this problem is the fact that the particles are entangled and the state that one of them ends up in. For such a situation to allow superluminal communication, it would be necessary that one of these pieces of information be able to be chosen by Alice or Bob. But, the fact that they both know about the entanglement to begin with means that information is only transferred if an experimenter can pick which state her particle ends up in, which isn't possible in the sort of measurements which won't break the entanglement.

both light and the neutrinos were measured by alienzed · 2011-10-15 17:26 · Score: 1

by the same gear, so wouldn't any error affect both speeds/times?

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Re:I hope that this is true. by Rakishi · 2011-10-15 17:38 · Score: 1

The information in that experiment was still transmitted by regular light speed means. Anyone who trusts science journalists to be even close to accurate is a fool.

Re:Measure the speed of light from CERN to OPERA by Parlyne · 2011-10-15 17:51 · Score: 1

That would involve a longer path length than the neutrinos traveled. So, no go there.

Re:Do GPS measurements even matter? by Parlyne · 2011-10-15 17:56 · Score: 1

Whomever wrote that was talking out of, err, where the photons don't shine. Just like they don't shine through 730 km of solid rock. The experiment compares the measured neutrino speed with the previously known speed of light. It's not performed as a race between photons and neutrinos.

Re:I hope that this is true. by Rakishi · 2011-10-15 18:04 · Score: 1

This is information wise identical to me giving two sealed envelopes to Alice and Bob. Each contains an identical sheet of paper with either a 0 or a 1 written on it. Bob opens his envelope and sends the number to Alice. Alice then opens hers and after a minute notes it's the same as what Bob sent her.

No informational FTL just quantum weirdness.

Re:I hope that this is true. by The+Master+Control+P · 2011-10-15 18:07 · Score: 1

The situation you describe can't violate causality. In order to have become entangled, the particles must have been near to each other in the past before one of them was put on the slow boat to Bob's lab.

Re:Whats... by cheekyjohnson · 2011-10-15 18:21 · Score: 1

Stop being so greedy and entitled. Here in America (or any other country that's better than third world countries), we have it great. Therefore, you have no right to complain.

After all, things could be worse (which doesn't apply to people in, say, Africa because I said so). If things could be worse, that means your current situation is good!

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Re:I hope that this is true. by 0123456 · 2011-10-15 18:50 · Score: 1

Interactions between coupled particles have been shown to occur instantaneously, ie, faster than light.

Hint for you: Google 'transactional interpretation'.

What is this paper trying to say? by WaffleMonster · 2011-10-15 20:05 · Score: 1

I don't understand what they are getting at.

The distance from GPS to earth is different than the distance seen from earth to GPS. This is certainly correct.

The address this GPS satellites slow their clocks to emulate the passage of time on the ground to correct for existing in an accelerated frame and difference in gravity.

The author seems to be making some bizzare conclusion since the observed distances are different in each frame the flight time of photons needs further adjustment to account for the difference of observation between GPS and ground with regards to actual flight time... ah no thats what the slowing down of the GPS clocks to sync with ground are for.

Anyway even if I'm the one confused and the clocks really are off by some 64ns there are two GPS receivers at each end and they are both off by the same 64ns. They could be off by a century for all they care it would still have no effect on measurements as long as both clocks remain synchronized.

Re:I hope that this is true. by WaffleMonster · 2011-10-15 20:38 · Score: 1

Ok, but even if Alice and Bob found a way to transmit new information instantly, I'm still not seeing how a paradox could exist. Alice could send Bob a message, and Bob could calculate a response and send it back. Alice would receive the calculated response before light-speed would allow, but that wouldn't seem to violate causality by creating a paradox... from what I can tell, it would only violate the principle that nothing could travel faster than the speed of light. But instantaneous information transfer (FTL) is the supposition, therefore nothing has been proven.

Your 100% correct there is no contradiction with regards to FTL communication as an abstract idea. The devils in the details (How you actually accomplish it)

This can be done by sending your message through a region of space with negative density it will get there faster than if sent through a region of normal space... (Wormholes)

Or along the same lines you can use a warp drive to beat light.

The problem with going faster than light without playing games with space, coherence loopholes, extra dimensions..etc is if you look at the situation from different reference frames cause and effect are reversed.

From POV of photons moving at c the universe most likely appears as a point..space and time don't really exist as we see it in their frame.

There is no reason at all neutrinos can't be screwing with space in a way that would make them faster than light without opening causality worm cans.

Re:XKCD by Karellen · 2011-10-15 20:54 · Score: 1

Ha!

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Why don't the photons show the discrepancy ? by Altesse · 2011-10-15 21:02 · Score: 1

What I don't understand in almost all the refutals is that the measured speed of the photons is just ignored. I mean, IANAP, but if I measure the speed of two cars or two athletes racing, and use an incorrect way of computing the speeds, no matter what, if one of them is faster, my recorded times will show it.

If there was a blatant error of calculation, why would they see the photons behave normally ?

Re:Why don't the photons show the discrepancy ? by Paradigm_Complex · 2011-10-16 02:32 · Score: 1

I think what you're missing is the fact that experiments done to calculate the speed of photons are completely different from experiments done to calculate the speed of neutrinos. It's quite feasible for an error to crop up in one group of experiments and not in the other. Calculating the speed of photons via experimentation is *much* easier, since they're not nearly as hesitent to interact with other particles. Additionally, humanity has done way more experiments calculating the speed of light. We're getting pretty good at it. While it's certainly possible that we've got that part wrong - we were wrong when we thought Newtonian Physics explained everything - it's far, far less likely than the possibility that we just messed up something unique to this latest experiment. The question is, what part was messed up.

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"A witty saying proves nothing." - Voltaire

Bogus, please check the sources by xanojsp · 2011-10-15 21:15 · Score: 2

The authors have documented their whole procedure here: http://www.ohwr.org/projects/cngs-time-transfer/wiki The author of the bogus paper assumes the people who designed GPS and those who use it in metrology labs around the world to manufacture GPS do not know anything about relativity. He also proceeds to an analysis without checking his very basic premises first with the authors of the neutrino velocity paper, or anybody close to the actual experiment. Is it that hard to check one's assumptions first?

Re:Bogus, please check the sources by xanojsp · 2011-10-15 21:50 · Score: 1

I meant "to manufacture UTC" instead of "to manufacture GPS". Sorry.

Run the experiment backwards by Maximum+Prophet · 2011-10-16 01:28 · Score: 1

I know it's tough but to verify, they could put a long fiber optic along the route, and then measure the time of flight of light forwards and backwards.

If light, using the same measurement system takes the same amount of time West to East as East to West they know there's nothing monkeying with their measurements.

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Re:Run the experiment backwards by fluffy99 · 2011-10-16 06:43 · Score: 1

It would have to be a very carefully calibrated fiber. Photons travel slower in fibers than a vacumn, so you'd need to measure that speed very accurately.

Re:I hope that this is true. by bondsbw · 2011-10-16 02:40 · Score: 1

Yeah, I understand all of that, but (after a little more research) it doesn't make any difference when all parties are in the same inertial reference frame. It makes a difference when you add another inertial reference frame. I like the explanation at http://www.theculture.org/rich/sharpblue/archives/000089.html, which begins with the situation I proposed with Alice and Bob transmitting with an ansible (which would be equivalent to instantaneous transmission via some mechanism like quantum teleportation).

By itself, this single use of the ansible doesn’t create a causality violation. If Bob transmits a signal back towards Alice using a conventional light-speed transmitter, she receives it a later time than when she signalled to Bob. Even if Bob re-transmits with his ansible, Alice receives the reply just a little after she sent out her signal. The problems arise when we bring another inertial frame into play. Let’s suppose that we have another pair of inertial observers, Carol and Dave, who are moving with respect to Alice and Bob, and who have a pair of ansibles of their own. As Carol flies past Bob at event Q, Bob gives her the message from Alice and she transmits it to Dave as soon in the diagram . . .

Now causality is in real trouble, as we can see if we consider the pair of transmissions (from Alice to Bob, then from Carol to Dave) . . .

Notice that we’ve arranged for Dave to receive the signal from Carol as he’s flying past Alice. Notice too that he receives it before Alice has sent her first signal! This means that Alice can transmit information into her own past by way of Bob, Carol, Dave, some spaceships, and two pairs of ansibles. And that’s why faster than light travel or communication, special relativity and causality cannot coexist.

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Paper in English by Roger+W+Moore · 2011-10-16 07:13 · Score: 1

Not every language spells photon as such.

True but the paper was written in english, not dutch. I wouldn't write 'Electron' when writing german since, in that language, it is spelt 'Elektron'. While it is an understandable mistake the fact that the author does not know the correct spelling suggests that either does not normally write papers or that he does not normally write papers about photons i.e. he is out of his area of expertise.

Re:Paper in English by Wandering+Idiot · 2011-10-16 11:29 · Score: 1

While it is an understandable mistake the fact that the author does not know the correct spelling suggests that either does not normally write papers or that he does not normally write papers about photons i.e. he is out of his area of expertise.

Maybe he just doesn't normally write papers in English?
Re:Paper in English by Roger+W+Moore · 2011-10-17 04:15 · Score: 1

In which case, English being the lingua franca of science (as unfair as that may be to non-native English speakers), he clearly has not written many scientific papers before.

Re:I hope that this is true. by Old+Wolf · 2011-10-16 08:18 · Score: 1

Even if these neutrinos are proven to be FTL, it doesn't mean the barrier was broken: another explanation would be that all neutrinos are FTL. They stay on the other side of the barrier their whole life!

Re:I hope that this is true. by BitZtream · 2011-10-16 12:34 · Score: 1

Not necessarily wrong, just missing some details.

So wrong then? Yea?

If our current understanding was wrong, we would have already seen all sorts of phenomena that don't fit the theory.

We have, hence special relativity and several other theories competing to explain the weird bits.

We've got a good grasp of some parts of the general theory of everything, but we're also missing some major important bits that tie up loose ends.

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Re:I hope that this is true. by AK+Marc · 2011-10-16 12:38 · Score: 1

You misunderstand the basics. It isn't that "nothing can travel faster than light". It's that nothing can be accelerated from below the speed of light to above. The separation is indeed 2C. And if you take scissors sufficiently large and call the point of cutting the "I" (for "intersection") point, that point can travel faster than the speed of light if you close the scissors fast enough (and that fast enough will be an achievable speed). So "I" moves faster than the speed of light. No problem. But "I" doesn't have mass, so that's ok. Yes, the things in your example are separating at 2C from your frame, but that's also a useless measure. It gives you nothing, and it's as "interesting" as "I" moving faster than light. It lets you say something is FTL, but not useful in a physics sense.

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Re:I hope that this is true. by StikyPad · 2011-10-16 21:57 · Score: 1

I don't think the hypothetical scissors would work... if it did, you could modulate the opening and closing and send information faster than light. The point doesn't have mass, but the scissors do, which is where the problem lies. For the tips of the scissors to move, that force has to be transmitted along the medium, the material from which they're crafted, and for the tips to move in conjunction with the closing force, you'd need a material of infinite strength and zero elasticity. At least that's my understanding...

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Re:Gut feeling by Tim+C · 2011-10-16 22:15 · Score: 1

Einstein's "law" of relativity

It's called the Theory of Relativity, not law.

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FPGA artifacts by Dwonis · 2011-10-17 00:28 · Score: 1

The best guess I've seen so far (admittedly, it was just speculation) was that the difference might be due to variable timing delays introduced by the FPGA-based data acquisition system.

Re:FPGA artifacts by mzs · 2011-10-18 04:00 · Score: 1

That author misunderstands FPGAs. I have one here with two 16-bit 8kilasample registers. We're working on adapting it for a larger FPGA since this bitty one is getting hard to buy now. They're not like cpus, no caches and what not.In fact the OPERA team used a heat gun and saw only 2ns over an extreme range of temperatures that would not happen during the experiment.
Re:FPGA artifacts by Dwonis · 2011-10-18 11:29 · Score: 1

Huh? There's no reason why an FPGA design can't use DRAM or implement caching.

Re:What about this... by Chris+Burke · 2011-10-17 04:16 · Score: 1

Dilitihium veins, bitches!

Dilithium veins, perhaps... But it seems very implausible that bitches would exist under the mountains or be able to accelerating neutrinos.

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The enemies of Democracy are

Re:I hope that this is true. by Agent0013 · 2011-10-17 06:21 · Score: 1

The hypothetical scissors example is similar to sweeping a laser beam across the sky. A point on the beam out at the distance of Pluto's orbit would be moving faster than C. The intersection of the scissors is the same in that it isn't an actual object, but something we are creating in our minds. The scissors could be moving at 100 MPH and be almost but not exactly parallel. Then the intersection would easily move very rapidly (possible even faster than C if they were very close to parallel).

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Re:I hope that this is true. by FredFredrickson · 2011-10-20 04:19 · Score: 1

Exactly.. The idea is that, let's say an explosion happens 1 light year away. Just before the explosion, they send a FTL message to earth to warn us about it. We get the message before the event happens in our frame of reference. Thus apparently events happened out of order. But this isn't breaking causality, because there's nothing we can do with this information that would prevent the explosion from taking place. We'd just know about it sooner. It'd still take us 1 year at the speed of light to get out to the site of the explosion to stop it.

tl;dr: FTL does not necessarily break causality.

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