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Superluminal Neutrinos, Take Two
Coisiche writes "To address the many responses to their original findings, the OPERA team who reported the detection of faster-than-light neutrinos is starting a new and improved version of their experiment. 'The neutrinos that emerge at Gran Sasso start off as a beam of proton particles at CERN. Through a series of complex interactions, neutrino particles are generated from this beam and stream through the Earth's crust to Italy. Originally, CERN fired the protons in a long pulse lasting 10 microseconds (10 millionths of a second). ... [In the new experiment], protons are sent in a series of short bursts — lasting just one or two nanoseconds, thousands of times shorter — with a large gap (roughly 500 nanoseconds) in between each burst. This system, says Dr Bertolucci, is more efficient: "For every neutrino event at Gran Sasso, you can connect it unambiguously with the batch of protons at CERN," he explained.'"
I've heard, they ran into further delays, because the experiment was stolen. Luckily the cameras got a good shot of the thief. It is princess Leia of Alderan
They already did this next week, didn't they?
. . . oh, wait.
I knew browsers were getting fast, but faster than light?
... is a neutrino.
Oblig and not even so related xkcd: http://xkcd.com/282/
This new experiment seems much more suited to examining the speed of neutrinos. Can't wait to hear the results.
I've always found particle physics fascinating, though I won't claim to understand any of it.
I'm disappointed that people are so vehemently against nuclear reactors these days that Germany is shutting some of them down.
And, of course, we're not in a hurry to use nuclear weapons either.
Radiation therapy has been a good application, but I would like to believe it will eventually be replaced by something less aggressive and more specific. Super-heavy atoms are really cool, but they're always so unstable we can barely measure them.
What other practical applications can we hope to achieve?
Will fusion be cleaner than fission and more publicly acceptable?
Inquiring minds want to know.
Actually, this might be slightly less off-topic than it would be normally... At the time I'm reading this, Slashdot's little quote of the day at the bottom of the page is actually about apartments:
Yes, I've now got this nice little apartment in New York, one of those L-shaped ones. Unfortunately, it's a lower case l. -- Rita Rudner
Good to see the scientists are being so disCERNing.
"That's the way to do it" - Punch
This is helpful but not that helpful. There are at this point a variety of potential explanations for what went wrong in the OPERA experiment. These include mismeasuring the tunnel length, issues with the clock calibration, and issues with the statistical analysis among other issues. It is important to note that while the OPERA group is double checking most of these issues, this experiment only really helps deal with a single problem, the statistical analysis of the neutrinos. If they are associated to individual bursts, the statistical test will be much simpler. So even if this still gets the same result, this won't be that strong evidence that there's something real going on here.
A better replication attempt is that which is being done by MINOS http://en.wikipedia.org/wiki/MINOS, the equivalent experiment at Fermilab in the US. One reason that OPERA was paying careful attention to the arrival times (when their main interest was actually in measuring neutrino oscillation) was that MINOS had earlier reported data that tentatively suggested that some neutrinos might be going too fast. Now that OPERA has done their work, MINOS is working on doing a more detailed analysis that should be out by around February.
Overall, I still think that there's a mistake here, but it is interesting to see how long this is taking to find where the mistake was. The apparent initial sprint by physicists to find the error is turning into a marathon. The data though still needs to be somehow reconciled with the fact that neutrinos from SN 1987a (a supernova that occurred close to Earth and whose light and neutrinos reached Earth in 1987 ahref=http://en.wikipedia.org/wiki/SN_1987Arel=url2html-7691http://en.wikipedia.org/wiki/SN_1987A> had the neutrinos arrive when conventional theory predicted them, that is a few hours before the light. This isn't due to neutrinos traveling faster than the speed of light, but due to the fact that neutrinos are produced at the way beginning of a supernova in the core and then fly out with a headstart because they can easily avoid most of the matter in the star but the light takes time to get through the star. But, if the neutrinos traveled faster than light to the extent OPERA data suggests then SN 1987A neutrinos should have arrived years earlier.
There are some other possibilities that would reconcile the two claims. For example, it is possible that neutrinos actually travel faster in a denser medium. This would be really weird. It is also possible that the reactions we think produce neutrinos actually produce a very short lived tachyon which itself decays into a neutrino. This starts running afoul of Occam's razor, but would explain why one would see too much velocity in the OPERA setting but not from the supernova. This hypothesis is actually also pretty easily testable: one needs to use a shorter distance for one's neutrino detectors and see if the apparent velocity goes up.
Overall, I still suspect that this is a fluke or error of some kind. But I really hope it isn't. This could be the Michelson–Morley experiment of our error, the first anomaly which leads to a glimpse of some fantastically deeper understanding of the universe. But I really wouldn't bet on it.
when you can just go back in time and recheck your results?
...they're now gonna find the discrepancy with predicted time of arrival is even larger ;-)
why aren't the results available before the experiment??
This is actually an elaborate analogy about the neutrino experiment. Had no idea such concentrated genius could be contained within such a short post. God, I have to go back to school so I can aspire to approach such brilliance.
If the pulses are 500 nanoseconds apart, then about 4800 pulses would have been sent before the first one is received, and the pulses would be 150 metres apart.
Though, if they were insterested only in what deviation from the expected delay or frequency there is, and not the total travel time, then it'd make sense.
No-one would want to be using the 2MHz band nearby.
What bothers me about this, is that there is a certain likelihood, that the reason why the story was released so early, was not so much that the researchers hoped to get more people to review their findings, as that they might have hoped to get the necessary funding and/or intstrument time for this experiment faster (or even get it at all).
Mind you, running the experiment the way they now do is certainly the right thing to do if you want to measure the speed of neutrinos. The former experiment struck me as highly unreliable and not really suited to do the job - because the initial pulse was so much longer than the time delays they wanted to measure. It would be unfortunate, if this became a precedent to releasing sensationalist findings in order to get the wherewithal necessary to do experiments properly.
So, even if they're 'only' going at the speed of light, we're transmitting a signal in a straight line at the equivalent of 100Kb/s. Would it be practical to use this as a low-latency alternative to trans-oceanic fiber-optic cables?
To understand the xkcd joke I suppose you have to both be Italian and read the comic in English (i.e., nobody will understand it). Full disclosure: I'm Italian.
They changed the outcome by observing it! This is just another example of Big Physics ruining the results of science by observing the location of particles.
Gonzo Granzeau
"Nothing the god of biomechanics wouldn't let you into heaven for.." -Roy Batty
So.... are they going to take Gravity into consideration this time?
10 microseconds (10 millionths of a second)
Why on earth are you explaining this on Slashdot?
There are already some explanations, of which the following one is the most notable explanation imho (and Prof. Dr. Viatcheslav Mukhanov): http://arxiv.org/abs/1109.5685
Every time this is discussed on slashdot, we get comments from people asking if neutrinos are tachyonic, why did the supernova SN 1987a ones not arrive earlier. The answer is very simple: neutrino oscillations, where only some (probably muon type) are superluminal. http://arxiv.org/abs/1109.6055 PS I still think experimental error is the most likely explanation, but I'm tired of hearing the invalid criticism of the SN 1987a observations. Stop it, it's getting fucking annoying!
"Politicians and diapers must be changed often, and for the same reason."
Superluminal Neutrinos, Take Two, and call me yesterday morning.
Sorry
Just another "Cubible(sic) Joe" 2 17 3061
Technically you are right but Occam's Razor gets pretty dull if you have to hypothesize that one type of neutrino is superluminal and another is not. Other than mass, aren't electrons, muons, and tau particles pretty much identical? Shouldn't their associated neutrinos be, too? So you are right that SN 1987a doesn't prove that muon neutrinos aren't superluminal, but it, combined with the similarities of the leptons and their neutrinos is still a strong indicator that they aren't.
It's been known ever since Popper's time that the sort of inductive reasoning implicit in "is still a strong indicator that they aren't" is not scientifically valid: http://en.wikipedia.org/wiki/Critical_rationalism
"Politicians and diapers must be changed often, and for the same reason."
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Alternative neutrino speed theory
Can you post the calculation of the 120 MeV? Keep in mind the possibility of the beam crossing something that we haven't noticed yet, if you know what I mean. Depending on how well the new MINOS results agree with this, we shall see.
On a related topic: how to build a neutrino communications device that is fairly compact (as in, portable)?
"Politicians and diapers must be changed often, and for the same reason."
Standard particles E = mc^2 /sqrt( 1- v^2/c^2), a tachyon has v>c, and an
imaginary mass, m = sqrt(-1) * m(tachyonic), so we get:
E = m(tachyonic) c^2 / sqrt( v^2/c^2 -1 )
So, m ~ sqrt (2 (v-c)/c ) * E
E was around 20-40 GeV (Same speed was measured for all velocities, which doesn't look like a tachyon, in particular doesn't fit with the tachyon equation above).
And (v-c)/c ~ 2.5 *10^-5
That Gives m = 120 Mev, (or in the paper with error bounds, m~ (110 to 130) MeV
Given their fine control over the neutrino pulses, it sounds like the they should be able to modulate the stream---e.g., change the interval between pulses---to transmit a signal. This would give speed-of-light, noise free communication in a straight line through the earth (reducing the latency for US-australia communication by a factor of pi). It's a bit expensive for general use, but would be an amazing science-fiction level achievement.
Other than mass, aren't electrons, muons, and tau particles pretty much identical? Shouldn't their associated neutrinos be, too?
You do realize that it only takes a difference in mass for particles to be tachyonic or non-tachyonic, right? Sure, that difference is by a factor of i, but it's still just the mass.
-- Alastair
How this article has nothing to do with Opera, the browser. Despite the /. icon for this story being the trademark red O.
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
The Michelson–Morley experiment doesn't show that there is no aether , only that we are not moving relatively to it. Particles that have more mass than neutrinos have more inertia to the expansion of space. Since space is expanding uniformly in all directions (like a rising cake), no matter what direction you look, the expansion is the same, the neutrinos get pulled with less resistance through the expanding space than the rest, so they arrive faster.
Here are my thoughts and explanation of OPERA experiment.
a. The OPERA experiment shows that speed of neutrinos is greater than 299,792,458 m/s (light speed in the SI system).
b. The research A.G. Cohen and S. L.Glashow showed that neutrinos can not travel faster than light, because "most of the neutrinos would have suffered several pair emissions en route".
c. The ICARUS paper shows that speed of neutrinos is equal to speed of light.
This obvious paradox between experiment and theory can easily be resolved if the speed of light is slowly increasing and is now (or at least was during the experiment) higher than in 1970-1980 when it was measured and included into SI system. In this case the speed of neutrinos in the OPERA experiment can be higher than 299,792,458 m/s, but at the same time be less or equal to current c. The full paper can be downloaded here: http://www.smartalerter.com/Is_Speed_Of_Light_Increasing.pdf
Mark Zilberman