[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?

[hugh3]

At this point I'm 99.9% certain that we're looking at some kind of experimental error, but being unfamiliar with the details I'm not about to start speculating on particular things that might be wrong. Any possible error that I could think of would probably, if presented to the experimentalists, result in a rolling of eyes and a "Don't you think we already checked that?"

To put it in terms that people here can understand, suppose you're three days into tracking down some incredibly obscure bug and your mother asks "Did you try turning it off and turning it on again?"

[thumper]

The crazy thing is that when people say that to me, I kinda roll my eyes but try it so that I'm not dismissive... and sometimes it works!

[libria]

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.

[sprovoost]

According Arethuza's comment below, at least one of the labs is 1400 meters below ground. Also you need to calculate the straight-line distance between the two points, not the distance over the surface. Although for calculating the difference that's probably a good enough approximation. So if both stations are 1400 deep and your calculation is correct, the difference should be 14x21=300 meters. Which is a lot more than the 15m effect they found, which suggests they thought about this.

[lutorm]

They claim the geodesic measurements are done to within 0.6m, and the majority of that uncertainty is introduced by the need to triangulate down the tunnel to the experiment.