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CERN team claims measurement of neutrino speed >c 
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#199
Sep2511, 10:26 AM

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First, a lot of the issues people (especially first time posters) are bringing up are addressed in the paper. Read it. There are very few people who can tell what another group did wrong without knowing what they did.
Second, the difference between a rotating earth frame and a stationary frame is essentially irrelevant. If you draw the spacetime diagram for the setup, including the GPS satellites (one is enough if you assume it's already synchronized) you will discover what they are measuring is very close to the interval between emission and detection, which is a Lorentz invariant. There are two corrections that need to be applied  one is the fact that LGNS is moving 50mph faster than CERN because of the earth's rotation: that's a 10^{15} effect. The other is that the earth has moved between the emission and detection times by a few feet. That should be properly taken into account by the GPS receiver (and I have questioned this), and if it is, it's a 10^{6} effect on the 10^{5} effect, or 10^{11}. As I have said before, the application of using GPS to synchronize two distant stations to a nanosecond is not common, and as such I am less confident that the firmware in the unit is bugfree than had the application been more widely used. Third, the statistical techniques for determining whether Model A or Model B fit the data better (say a 0ns offset and a 60 ns offset) are almost a century old, and welldescribed in the paper, and shown clearly in Figure 8. The idea that some people here can do a better job with the statistics in their heads is ridiculous. In any event, Figure 12 makes it clear  this is not a simple statistical fluke: if you moved the data 1.2 bins to the left or right, you would see the difference. 


#200
Sep2511, 11:31 AM

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However, SR effects account for about 10^6 (relative velocities), so if what you say is correct, this means that GR effects are also of the order of 10^6 for a depth of 20 something km. Now, the chord of a 700 km arc dips about 10 km deep into the earth, so one would expect then a similar GR correction to the interval. 


#201
Sep2511, 11:43 AM

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#202
Sep2511, 11:45 AM

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#203
Sep2511, 11:57 AM

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#204
Sep2511, 11:59 AM

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#205
Sep2511, 12:21 PM

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What I wanted to say was that if you "synchronize" in a stationary reference frame Oxyzt, which means that at events "Emission" and "Reception" you measure "t" (the t of the reference frame Oxyzt), but you measure the distance between "Emission" and "Reception" in a frame Ox'y'z't' using worldlines of stationary points (that is, with 0 velocity in frame Ox'y'z't') so that it is easy to measure that distance in that frame, then you cannot combine this distance measured in Ox'y'z't' with a time measured on Oxyzt. My question was what kind of time coordinate (in what kind of frame) is used in the GPS system (no matter how they actually do it, assuming they do it right), and I thought that it was only possible in an intertial frame. However, I stand corrected, this can also be a time on a rotating geode which also contains another "universal time" as I forgot about the GR correction. But it DOES matter what reference frame one uses to define "synchronised time", because mixing a time coordinate from one frame and a distance from another is at the origin of all "paradoxes" in introductory SR, such as the polebarn paradox and the like. The point is not that I think I'm smarter than those guys, it is just that nothing of all this was mentioned in the paper. 


#206
Sep2511, 12:58 PM

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I guess this closes the discussion about a relativistic effect due to earth's gravity or rotation... 


#207
Sep2511, 01:31 PM

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All my tentative "might' and "could' words are because, they're smart guys and maybe they already did it just right, but a paper with that level of total detail in it would be unreadable! There's deep exam questions here about experimental technique, just as should be. It's a lot of work for them to answer even a few of the most carefully considered issues of the critics. This will take time. There is no way around it, and they understand that. 


#208
Sep2511, 02:43 PM

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#209
Sep2511, 03:05 PM

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#210
Sep2511, 03:11 PM

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GPS satellites are not in geosynchronous orbits.
Whatever mistake was made, if a mistake was made, was quite subtle. That group has been building up this data for a few years. They looked for obvious explanations, not so obvious explanations, asked outside groups for help, and still couldn't find anything that explained their results. I'm guessing that they did do something wrong. I'm also guessing that we at PhysicsForums will not be the ones to ferret that mistake out. 


#211
Sep2511, 03:13 PM

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#212
Sep2511, 03:29 PM

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#213
Sep2511, 03:40 PM

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Furthermore, the errors in the orbit estimations are irrelevant here. Those experimenters used common view mode, which reduces errors in both relative time and relative position by orders of magnitude. Common view mode, relative GPS, and differential GPS have been around for quite some time. The basic concept is thirty years old, but not the 10 nanosecond accuracy claimed by the experimenters. 


#214
Sep2511, 03:48 PM

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#215
Sep2511, 03:55 PM

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#216
Sep2511, 04:30 PM

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Likelihood function = probability density function. Just a different name maybe with different normalization. I apologize in advance because I don't think you're going to like this link very much. I don't. It has an approach which obscures the intuition if you not comfortable with the math. It also has links which may be useful. Keep following links, use Google search on the technical terms, and eventually you'll find something you're happy with. Try starting here: http://en.wikipedia.org/wiki/Probabi...nsity_function 


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