[QUOTE=only_human;272549][URL="http://gizmodo.com/5843117/scientists-reconstruct-brains-visions-into-digital-video-in-historic-experiment"]Scientists Reconstruct Brains’ Visions Into Digital Video In Historic Experiment[/URL][/QUOTE]

if it can be worked to look at imagination I could see it being used to make films of crime scene investigators minds as they go over a case. Of course someone in the comments pointed out that witnesses are not always reliable.

Wolfgang Ernst Pauli
 

Thought I'd Google him, and I found these anecdotes thrilling:
[URL]http://en.wikipedia.org/wiki/Wolfgang_Pauli[/URL]

David

[QUOTE=ewmayer;272541]Hey, Scott:
But that still doesn't answer Paul's question about oscillations among the electron, muon and tau leptons themselves. Are these also subject to flavor oscillation, or not? If not, what is it which does not permit them to oscillate? (e.g. Their much-larger masses, or the fact that carry charge?)[/QUOTE]

I have to give you a very unsatisfying answer. For neutrinos, the observed fact is that the mass eigenstates are not the flavor eigenstates. That is, the observed particles don't have exact leptonic flavor, but instead are superpositions of pure-flavor wavefunctions, through a mixing matrix called (I just looked up) the Pontecorvo-Maki-Nakagawa-Sakata matrix. For the other leptons, this is just not so. Electrons, muons and taus are all exact flavor eigenstates.

Given our current level of insight into the structure of the standard model, the best we can say is that we observe that these facts are so, and so write the SM Lagrangian to capture that fact. But why the Lagrangian has this structure, for this feature, or any other (number of families, masses of particles, etc.) is not known.

Some additional insights are available to some of these questions in the various extensions of the SM, but none of them have any evidence in their favor at this point, so I personally prefer "we don't know why" as the best answer.


--Scott

[url]http://ca.news.yahoo.com/particles-seen-travel-faster-light-scientists-185504341.html[/url]

first thing I feel like pointing out is the speed of light is 299,792 km/s not 300,000 so the discrepancy is 214 km/s not the 6 claimed.

[QUOTE=science_man_88;272585][url]http://ca.news.yahoo.com/particles-seen-travel-faster-light-scientists-185504341.html[/url]

first thing I feel like pointing out is the speed of light is 299,792 km/s not 300,000 so the discrepancy is 214 km/s not the 6 claimed.[/QUOTE]

I'm guessing someone else has already done a check of:

[TEX]\frac{l}{t} = \frac{l_0\times\sqrt{1-\frac{v^2}{c^2}}}{\frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}}}= \frac{l_0}{t_0}\times {(1-\frac{v^2}{c^2})}[/TEX]

[QUOTE=science_man_88;272613]I'm guessing someone else has already done a check of:

[TEX]\frac{l}{t} = \frac{l_0\times\sqrt{1-\frac{v^2}{c^2}}}{\frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}}}= \frac{l_0}{t_0}\times {(1-\frac{v^2}{c^2})}[/TEX][/QUOTE]
The internet is a good friend of mine and I find this article assures me that considerable effort (much more than I would have thought) has been expended to make sure that the results are as accurate as they know how to make them:
[URL="http://arstechnica.com/science/news/2011/09/neutrino-results-depend-on-exquisite-measurements-of-time-space.ars"]More details on the "faster than the speed of light" neutrinos[/URL][QUOTE]As a spokesperson for the MINOS neutrino experiment told Ars yesterday, there are three potential sources of error in the timing measurements: distance errors, time-of-flight errors, and errors in the timing of neutrino production. The vast majority of both the paper and the lecture were dedicated to discussing how these errors were reduced (the actual detection of the neutrinos was only a small portion of the paper).

Neutrinos are produced using a proton beam from one of the accelerators that feeds them into the LHC. The protons hit a fixed target and produce unstable particles that decay, releasing a neutrino. The protons move close to, but not at the speed of light, as do the unstable pions; both of these effects were accounted for. The timing of the protons and structure of the two bunches of them used in these experiments is not even, either, so the researchers created a profile of the proton bunch. They also compensated for the timing of the kicker magnet that pushes the bunch out of the accelerator and added detectors that registered them passing through the hardware to get a clearer sense of their timing.

Similar work went into the detector side, where the time between an actual neutrino event and the signal propagating through the hardware and to a field programmable gate array (FPGA) where it was processed was estimated at about 50ns (the neutrinos only arrived 60ns early, so that 50ns is a substantial fraction of the total). But the error in their estimate was only ±2.3ns, as measured by shining a picosecond UV laser on the detector.

Distance travelled created its own problems. The positions of the hardware were measured via GPS, which normally doesn't provide the sort of precision needed for this work. But the labs did multiple samples of the GPS signals, threw out bad ones, compensated for the effect of the Earth's iononsphere, and more. Then, just to check their work, they had a commercial company come in and perform an independent analysis. The end result was a measurement sensitive enough to register both the steady change due to continental drift, as well as a 7cm jump triggered by an earthquake.

Then, the timing of all the events had to be synchronized. At each site, the group put a cesium-based atomic clock, and synchronized it with the GPS signal. Then, they sent a portable atomic clock between the facilities to check. They then ran photons through a fiber optic cable between them, just to make sure.

The end result is that the OPERA team doesn't see any obvious problems in its measurements. All of the errors, when added up, shouldn't be able to account for anything close to the 60ns gap between the neutrinos' arrival and the speed of light. The difference between their speed and that of light is very statistically significant, and the neutrino data itself looks excellent. The team has recorded over 16,000 events now, and the profile of events over time very closely matches the structure of the proton bunches that created them.

But that doesn't mean that this presentation is the last word on the topic. There are a lot of potential sources of error they know about—the paper's table lists a dozen of them. Small errors in each of these could add up to something more significant than their total error. Then there are the classic unknown unknowns. The authors have tried to think of everything, but it's not clear that they can.

The audience at the seminar was already thinking of other sources. For example, GPS signals don't actually penetrate down to the where any of the hardware is, meaning that this system has to track the hardware's motion a bit indirectly. This led one audience member to suggest "if this is a true measurement, drill a bloody hole." The speaker pointed out that commercial drilling equipment isn't accurate enough to go straight from the surface to the detectors, which are kept that deep to filter out most cosmic rays —in short, the solution would create another error.

The other reason that many are voicing skepticism are past measurements of neutrino speeds obtained from supernovae. Since these are so incredibly distant, the small signal seen here would be huge—the neutrinos should arrive roughly four years ahead of the photons. Other experiments on Earth also suggested insignificant differences. One possible explanation for this is the energy of the neutrinos, since OPERA uses much higher energy than the other sources. But the paper indicates that's not likely to be the case, since the authors saw the same signal with both 10 and 40GeV neutrinos.

In the meantime, the physics community will be looking through the paper, trying to spot unaccounted for sources of error. There are two other similar neutrino detectors in use—T2K and MINOS—and they'll undoubtedly be looking into working out the timing of their hardware with the same sort of thoroughness OPERA has.

The theorists, however, will undoubtedly be having a field day. It will be a while before anyone has the chance to test these results independently, giving theorists a chance to try to reconcile fast neutrinos with the rest of physics until then.[/QUOTE]As the last paragraph suggests, I'm sure all that relativity jazz will be given a good look, even if just for grins and giggles and pats on the back at how much of it has been carefully verified so many times and so many ways. My first thought when I heard about this result was wondering if the latitude differences of source and detection locations on the rotating planet would have time dilation differences that mattered (not that I would know); among other things, they have transported an atomic clock between the two sites. I wonder what use checking photons in a fiber optic cable would be because that light couldn't possibly travel the direct path that the nutrinos took, and the speed of light in the cable wouldn't be the same as in vacuum, but I feel that they must know what they are doing.

[QUOTE=only_human;272622]I wonder what use checking photons in a fiber optic cable would be because that light couldn't possibly travel the direct path that the nutrinos took, and the speed of light in the cable wouldn't be the same as in vacuum, but I feel that they must know what they are doing.[/QUOTE]That one I can answer. It is very easy to measure the speed of light in a cable by inserting short pulses and seeing how long they take to come out the other end.

When I was a grad student, a post doc (named John Eland, he's recently retired) I was working with built a photon time of flight spectrometer. I was present in the same room and helped him with building the kit though I can't take any credit for the experiment itself. It used a kilometre or few of fibre and a nanosecond electric spark at one end. At the other end was a sensitive photomultiplier and a timer with approximately nanosecond resolution. The N[sub]2[/sub] spectrum was nicely resolved by waiting for the photons to drift through the cable. In glass, of course, red light travels markedly faster than blue so a TOF photon spectrometer works nicely. It would not work at all [i]in vacuo[/i], or so Einstein would have us believe.


Paul

[QUOTE=xilman;272640]In glass, of course, red light travels markedly faster than blue so a TOF photon spectrometer works nicely. It would not work at all [I]in vacuo[/I], or so Einstein would have us believe.


Paul[/QUOTE]

Maxwell might be a bit surprized as well.

David

[QUOTE=science_man_88;272613]I'm guessing someone else has already done a check of:

[TEX]\frac{l}{t} = \frac{l_0\times\sqrt{1-\frac{v^2}{c^2}}}{\frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}}}= \frac{l_0}{t_0}\times {(1-\frac{v^2}{c^2})}[/TEX][/QUOTE]



okay walking through this in my mind with 1=positive;0=negative;

we have [TEX]1=0\times0[/TEX] or [TEX]1=1\times1[/TEX]

the second 1 in the second equality says [TEX]1-\frac{v^2}{c^2}[/TEX] is positive this is normally v=1 but we also have another possibility not laid out for the value of v:[TEX]1-\frac{Neg}{c^2}[/TEX] gives a number greater than 1 so since [TEX]\sqrt{-1}= i [/TEX] the value of v can also be imaginary.

Why aren't there any slow nutrinos?
 

Ok, so the current conundrum aside, originally nutrinos were considered to travel at the speed of light because they were believed to have no mass. Since that isn't the current belief, what compels nutrinos to always travel everywhere in a hurry? Why aren't there any slow nutrinos?

May contain nuts...
 

AFAIK, neutrinos are not especially nutritious, but are electrically neutral.

Beta particles have a variety of energies, which led Pauli to postulate
the neutrino around 1930. Spin considerations may also have come into it.
Whether or not they have any mass can in principle be deduced from
the way the beta energy spectrum approaches zero at the point where
the neutrino takes none of the energy.

I guess there may be a few slow neutrinos, but that they are even
less detectable than energetic ones.

David