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CERN press release regarding neutrino experiment

press.web.cern.ch

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Re: CERN press release regarding neutrino experiment

#41

Post by Symmetry »

The path from the things people observed to "and neutrinos travel faster than light" travels down a long string of inferences. Inferences about the equipment working properly and inferences about other aspects of physical law.

Most likely this is a problem with the equipment. I'm sort of hoping that some other aspect of our knowledge of physics has been revealed to be off, though, since that is where real progress comes from.

It might even be that the most straightforward but most improbable case is right, and these neutrinos actually are traveling faster than light. That would be awesome, but also terrifying since then its only a matter of technology to get a device that would permit communication with the past.

Re: CERN press release regarding neutrino experiment

#42

Post by codehalo »

docgnome wrote: post #14
codehalo wrote: post #10

Earlier quoted context omitted.

Actually, this may be a good thing if the experiments turn out to be correct. There has been a lot of difficulty integrating gravity into the current theories to get a Grand Unified Theory/TOE. Maybe this will make physicists think about other novel ideas.

Possibly, but it's best to not get excited over results are this surprising. At least until someone else can duplicate them :-P

Indeed.

Re: CERN press release regarding neutrino experiment

#43

Post by nooneelse »

jasonkeene wrote: post #16
joeyespo wrote: post #4

From the release, there's a live webcast going on right now (16:00 CEST, Sept 23) at: http://webcast.cern.ch/

I so LOL'd when someone in the webinar pointed out that their measurement wasn't a vector so their paper should be titled neutrino speed not velocity. http://arxiv.org/abs/1109.4897

They know where the neutrinos were produced and where they were detected 730km away. That seems like enough for a pretty good guess at their direction of travel. But I guess they didn't really present that aspect of things.

Re: CERN press release regarding neutrino experiment

#44

Post by ivansavz »

I watched the news conf. this morning.

The neutrino production "curve" looks like a a square wave pulse as a function of time

____| |_____

and the detection points look like this

___________________________________| |_____

with ∆t ~= 700km/c time distance between the two pulses.

The claim is that the "most likely guess" of the received pulse shape (obtained from many measurements) is too far right to be consistent with speed of light, but the ∆t measured where?

between the onset of the pulses? between the place where the pulses go down?

What they did some mega calculation (maximum likelihood stuff), to predict the best approximation to the shape of the pulse at the receiving end -- so somehow they take on the approximation of the whole pulse (which is much wider than the claimed discrepancy).

They should downgrade the claim from: "speed of neutrinos is...." to: "speed of pulses of neutrinos ..... on average, as predicted by the maximum likely shape of the pulse", which sounds much less profound.

The conf was good though, the speaker stood up to a lot of serious scrutiny. My guess is the problem is with the ML curve shape calculation.

Re: CERN press release regarding neutrino experiment

#45

Post by cube13 »

ajross wrote: post #17
saulrh wrote: post #2

This press release is a perfect example of how to write a press release for a high-profile, possibly groundbreaking discovery. Understated, but still properly summarizes the importance of the result, and above all doesn't make any hysterical claims. Instead, it just presents the discovery, cites the paper, gives some background, grabs quotes from the scientists to show the reasoning behind their actions, and leaves i…

All true. But to be fair, you're praising the easy stuff. This is one of those one-in-a-career, truly groundbreaking results. They don't have to sell it. They just write it up in plain language and it sells itself.

Most importantly, they're not presenting the finding as fact. They're really asking for anyone that can prove them wrong, because they don't believe it, and are almost positive that there's something wrong with either their methodology or measurements.

Re: CERN press release regarding neutrino experiment

#46

Post by kmm »

ivansavz wrote: post #44

I watched the news conf. this morning. The neutrino production "curve" looks like a a square wave pulse as a function of time ____| |_____ and the detection points look like this ___________________________________| |_____ with ∆t ~= 700km/c time distance between the two pulses. The claim is that the "most likely guess" of the received pulse shape (obtained from many measurements) is too far right to be consistent wi…

I've read the article[1] and what they do is compare the proton flux as measured in Geneva with the neutrino signal measured in Gran Sasso. The proton signal is timeshifted a small amount until the curves overlap maximally.

Where the leading and trailing edge are is irrelevant here, as the complete shape of the pulses are compared.

1: http://static.arxiv.org/pdf/1109.4897.pdf

Re: CERN press release regarding neutrino experiment

#48

Post by sprovoost »

My guess is there's something wrong with the statistical modeling, but I realize that's not a very useful statement. I missed the press conference, but I did read the paper and I even understood a few things. :-) It was good to see they even thought about seismic activity (centimeters). One thing I noticed in both the article and the media is that the effect is never expressed in terms of distance (about 15 meters), but only in terms of time and speed. It surprises me that they're able to determine the point of creation and detection of neutrinos in such huge instruments, but of course they know their stuff. I did get the impression it took a lot of modelling and advanced statistics to achieve that, hence my earlier "gut feeling" that there lies the problem.

A few other possible explanation that crossed my mind and I'm sure are wrong and already thought about:

* the distance between both sides was measured very accurately, above ground. The earth is not flat, so the distance underground is shorter. I'm too tired to calculate how much shorter.

* relatistic effect of the beam going deeper underground on its way over; I read elsewhere that they already considered the effect of altitude difference between the two stations and that it was orders of magnitude smaller.

* some other mistake in distance measurement; have they tried sending other, easier to measure, signals over to figure out the distance? Or some other independent way to measure that distance?

Re: CERN press release regarding neutrino experiment

#49

Post by nirvana »

mjb wrote: post #30
nirvana wrote: post #26

Earlier quoted context omitted.

My background is in physics and one of my first programming jobs was writing code for a lab of international importance. At the time, I would engage the other members of the lab in an ongoing debate about Einstein, where I'd take the position that Einstein was wrong (About anything, or everything, whatever the handy topic was.) I was, and am, an Einsteinian skeptic. I learned a lot in that, and one thing that actuall…

You say: > I learned a lot in that, and one thing that actually surprised me is that in many cases, I was able to make a good argument that Einstein was wrong, and there was no empirical evidence to support his view on the particular point we were discussing. Then: > I'm not interested in getting into a physics debate. Its been too many years, and I've spoken vaguely because the specifics are not what I'm addressing.…

"You can't go making a claim like "there was no empirical evidence to support his view" about nearly any of Einstein's physics papers and then not want to debate it."

You're taking a statement I made about a particular view in a set of topics that were chosen for the purposes of debating where he might be wrong, and applying it to the entirety of his "papers".

"In any case, your assertion is false - there is a great deal of empirical evidence for all of Einstein's important theories."

I never asserted there was no empirical evidence for Einstein's theories.

The fact that you didn't address the point I was trying to make, and instead are giving me what seems to be an unsophisticated laymen view of "einstein couldn't have been wrong about anything!!!" is exactly why I'm not interested in debating physics here. Plus, its irrelevant to the actual topic.

Re: CERN press release regarding neutrino experiment

#50

Post by libria »

sprovoost wrote: post #48

My guess is there's something wrong with the statistical modeling, but I realize that's not a very useful statement. I missed the press conference, but I did read the paper and I even understood a few things. :-) It was good to see they even thought about seismic activity (centimeters). One thing I noticed in both the article and the media is that the effect is never expressed in terms of distance (about 15 meters),…

D of earth = 12756km, and assuming a sphere (my physics prof would be proud), I'm computing that 730km covers a ~6.6 degree arc. Also assuming a 100m underground tunnel, the distance would be 21m shorter than its above-ground measurement. Someone needs to recheck my math, though.
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