They wuark alike, they tuark alike,posted by Herodios at 11:44 AM on September 22, 2011 [14 favorites]
Sometimes they even quark alike --
You could lose you mind,
Nutrinooooos
Are two of a kiiiiind!
Doesn't the speed of light vary with the density of the medium?Sort of, but not really, and not in the sense that would allow you to draw a conclusion like:
Is it possible they've discovered that space is slightly denser, rather than the neutrinos being slightly faster?Really (or, as I understand it (or, as I understand we understood it until today)), light only travels in a vacuum. At the lowest level, there's no such thing as the speed of light in anything other than a vacuum. Rather, in some medium (let's say air), most of the actual space between particles is vacuum. Light travels in that vacuum, between particles, at the (only) speed of light. But it might hit a particle, get absorbed by that particle, and then get emitted by that particle. That absorption and re-emission takes time, so on average, the light took longer to travel the same distance that it would have had the particle not been there. Hence the rough idea of light moving slower in a medium than in a vacuum.
Light travels in that vacuum, between particles, at the (only) speed of light. But it might hit a particle, get absorbed by that particle, and then get emitted by that particle. That absorption and re-emission takes time, so on average, the light took longer to travel the same distance that it would have had the particle not been there. Hence the rough idea of light moving slower in a medium than in a vacuum. Disclaimer: IANAP."I think I read something recently (might have been that "10 mindblowing things about the universe" video, actually, so "watched" would be correct in that case).
Can you use this to convey information? If not then it doesn't matter.Of course you could. Trivial one-bit example: Replace the traditional "white smoke indicates a new Pope has been elected" with "a beam of neutrinos indicates a new Pope has been elected".
Imagine this is the discovery that finally makes Time Travel a reality.Dude, if time travel is ever going to happen, it already has.
Particle Chameleon Caught in the act of Changingposted by Herodios at 5:30 AM on September 23, 2011
Geneva 31 May 2010.
Researchers . . . announced the first direct observation of a tau particle in a muon neutrino beam. This is a significant result, providing the final missing piece of a puzzle that has been challenging science since the 1960s, and giving tantalizing hints of new physics to come.
Several experiments since have observed the disappearance of muon-neutrinos, confirming the oscillation hypothesis, but until now no observations of the appearance of a tau-neutrino in a pure muon-neutrino beam have been observed: this is the first time that the neutrino chameleon has been caught in the act of changing from muon-type to tau-type.
We are confident that this first event will be followed by others that will fully demonstrate the appearance of neutrino oscillation”.
[. . . ]
“This is an important step for neutrino physics,” said CERN Director General Rolf Heuer. . . We’re all looking forward to unveiling the new physics this result presages.”
[According to the Standard Model], neutrinos have no mass. [But f]or neutrinos to be able to oscillate, they must have mass. Something must be missing from the Standard Model.
One possibility is the existence of other, so-far unobserved types of neutrinos that could shed light on Dark Matter, which is believed to make up about a quarter of the Universe’s mass.
The team measured the travel times of neutrino bunches some 16,000 times, and have reached a level of statistical significance that in scientific circles would count as a formal discovery.I'm not betting against Einstein on any odds; just point out we don't have to (and really can't) conclude anything definite just yet.
Recall that OPERA was conceived to observe tau neutrino appearance, not to measure the neutrino speed, and indeed there are certain aspects of the experimental set-up that call for caution. The most worrying is the fact that OPERA has no way to know the precise production time of a neutrino it detects, as it could be produced anytime during a 10 microsecond long proton pulse that creates the neutrinos at CERN. To go around this problem they need a statistical approach. Namely, they measure the time delay of the neutrino arrival in Gran Sasso with respect to the start of the proton pulse at CERN. Then they fit the time distribution to the templates based on the measured shape of the proton pulse, assuming various hypotheses about the neutrino travel time. In this manner they find that the best fit is for the travel time is 60 nanoseconds smaller than what one would expect if the neutrinos traveled at the speed of light. However, one could easily imagine that the systematic errors of this procedure have been underestimated, for example, the shape of the rise and the fall-off of the proton pulse have been inaccurately measured.http://resonaances.blogspot.com/
(though it's 1/sqrt(1-v^2/c^2), so the actual dependence is 1+v/c for small v)physicsmatt, I agree with everything else you wrote, but you'll be deprived of the impossibly useful binomial expansion as long as you make this error. The approximation is (1-x)^n = 1-nx; there's never any √x.
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posted by nathancaswell at 11:02 AM on September 22, 2011 [17 favorites]