nm
Thank you for walking me through that and I think I even follow it … mostly. Well, okay, somewhat. 
I’ve read this entire thread with great interest, as well as the original OPERA paper. I don’t pretend to understand all (or for that matter, much) of it. However, seeing the scientific process work itself out is awesome to me. The OPERA scientists did as diligent a job as they could and put forth their findings for all to review and criticize. Other scientists have offered counter explanations for the OPERA results. The OPERA scientists reran their experiment in a modified form to remove another source of systematic uncertainty. And the work to replicate their results go on. Ain’t this grand? Wouldn’t it be equally grand if the OPERA results are indeed confirmed? That would force refinements to existing theory, and who knows, that could lead to breakthroughs in answering the big open questions in physics. Exciting times for sure!
Now if they could only set up an apparatus where if neutrinos from the future are detected, the accellerator won’t make them…
Two contradictory updates…
That “rejection” link is something that folks have been talking about since immediately after the experiment. Basically, all it is is saying that they can’t be superluminal, because the laws of physics say that superluminal particles would lose all of their energy. Personally, I think it’s a rather silly argument, since so far as we can tell, the laws of physics also say that superluminal particles can’t exist in the first place. Either way, if the experimental results hold up under extensive further tests, what it means is that our current understanding of the laws of physics are flawed. And if the laws saying that superluminal particles can’t exist at all are flawed, who’s to say that the laws saying that those nonexistent particles would lose all their energy might not also be flawed?
I noticed earlier on in this thread the speculation that the “speed of light” is maybe just a bit higher than we thought it was, eg its the speed of neutrinos and the speed of photons in a vacuum is slightly lower for some reason. (Vacuum polarization?) Is there another mathematical way of determining the speed of light from first principles or has it only ever been measured experimentally?
Or another way to put it, would the finding that our measurement of c (from photons) was a little lower than the absolute speed limit overthrow lots of other areas of physics?
Given that Einstein’s theories were published over 100 years ago, I’m guessing it had to be mathematics first and experimentation later.
I am not a physicist, but I was under the impression that special relativity and general relativity establish relationships between energy, mass and the speed of light, but do they actually define numerically a value for the speed of light? AFAIK, that’s always been measured experimentally and then plugged into Einstein’s equations.
The speed of light was first measured quite a while before Einstein.
“After Maxwell published his theory of electromagnetism it became possible to calculate the speed of light indirectly from the magnetic permeability and electric permitivity of free space. This was first done by Weber and Kohlrausch in 1857. In 1907 Rosa and Dorsey obtained 299,788 km/s in this way. It was the most accurate value at that time.”
A blog post, a few days ahead of the 25th anniversary* of Supernova 1987a, has a link to a [del]brand new[/del] 14 year old paper (PDF), analyzing some neutrino detections almost five hours earlier than the ones typically associated with the Supernova, and showing that they are consistent with superluminal neutrinos for at least one of the mass eigenstates.
- Feb. 23. Only two shopping days left!
The relevant part about the earlier detections:
Obviously the speed won’t match the OPERA speed, but it’s intriguing, and I thought others would want to read it.
ETA: I’d be interested in whether developments since the paper was written, e.g. better knowledge of neutrino mass differences, affect the results.
Also, what’s the current status of the faster-than-light neutrino results from last year? My most recent result from a google search is over a month old. It lists some reasons to be skeptical, but maintains an inconclusive note: http://arstechnica.com/science/news/2012/01/if-them-neutrinos-are-faster-than-light-physicists-have-a-lot-of-work-to-do.ars
Here’s something more recent, from just today: http://www.foxnews.com/scitech/2012/02/20/answer-to-shocking-faster-than-light-particles-expected-soon/
It just says that some experiments designed to confirm or disconfirm the results will come out this Spring.
Huh, I hadn’t realized that the MINOS experiment was proceeding so quickly. That’s great.
What annoys me about this whole thing is that the GPS technology used to measure the distances involved is based on Einsteins relativity work. So isn’t it the case that any experiment that might test relativity but also uses GPS must necessarily be flawed?
The GPS system is extremely well tested, via means which don’t as directly depend on relativity (in fact, GPS is the best experiment we have, for some aspects of the theory). And ultimately, any experiment to test some theory must involve predictions of that theory: At worst, if you invalidate the theory, you just can’t tell which aspect of it you’re invalidating.
Then there’s the problem that everything is all interconnected: Question too far, and you end up just wondering whether you might be a brain in a jar.
In Frylock’s link in Post 412, in the section Other sources of error a little over halfway down:
The key is that the lab recently decided to delay the upcoming year-long accelerator shutdown, which allows MINOS to collect a small amount of data with new timing equipment, which in turn lets one better calibrate older data. (The shutdown was actually delayed for unrelated reasons; the benefit to the MINOS time-of-flight measurement is a side bonus.) This year’s result won’t have the ultimate MINOS sensitivity, but it will be a significant improvement over the earlier MINOS result and will hopefully have enough precision to say something strong about the OPERA claim. The full MINOS precision will still come after the accelerator complex starts back up next year and MINOS takes additional data.
And just in time for another hypothesisto explain the FTL result:
From what I gather from the above discussion, the atomic clocks in question were only used on a second experiment undertaken to confirm the first experiment hadn’t been distorted by the use of GPS satellites?
Atomic clocks were used in all of the experiments. The difference between the two experiments was just in how the clocks at the different locations were synchronized with each other.