This page is an extract of questions and answers about Measurement of the neutrino velocity with the OPERA detector in the CNGS beam. The questions and answers have been edited slightly.
Surely there is a flaw in an experiment which measures the speed of light through the earth, a material which we can not quantify internally to an exact degree, contrasting with the exact nature of the speed of light (in a vacuum!).
Neutrinos have no electrical charge and also don't interact with other matter via the "strong" or nuclear interaction. They only interact with matter via the "weak" nuclear interaction. This means that they pass through most forms of matter without interacting with it.
We observe bursts of neutrinos from supernovae many hundreds if not thousands of light years from Earth. If neutrinos were travelling even fractionally faster than light, we should see the neutrinos arrive days if not years before the visible flash.
a) We have only ever observed supernova neutrinos once, in 1987. If today's announcement is true, the neutrinos would have arrived 4 years earlier. In 1983 no neutrino observatory had been built yet, so we don't know if they were there or not.
b) Supernovas produce electron neutrinos. CNGS uses muon neutrinos. Different particles with different properties.
So we have a result which is going to lead to a paradigm shift in physics.
Or an unrepeated result caused by a systematic error in a long and complex process.
I wonder which it is.
Here is MINOS (neutrino beam in the US) with similar results from 2007, 60ns faster than light over a 700km distance, although their errors were bigger, so that it was only a 1.8 sigma result.
... I'd start by checking that the distance between the source and detector has been calculated correctly. 60 billionths of a light second is about 18m, did somebody perhaps calculate the distance as an arc length ( the 'surface of the earth' measurement) instead of a chord length (the 'direct' measurement)?
The paper states:
A common analysis in the ETRF2000 reference frame of the 3D coordinates of the OPERA origin and of the target focal point allowed the determination 10 of this distance to be (730534.61 ± 0.20) m [26].The [26] here means "reference 26", which is Determination of the CNGS global geodesy.
In this paper, everything is done in three-dimensional coordinates, so it's clearly not the case that they have used surface distance.
... that suggests there is a measuring error in the experiment - maybe it's not as far from Switzerland to Italy as they think?
According to the published paper, the distance is measured to an accuracy of 20 centimetres. But with the discrepancy in time of 60 nanoseconds, a distance discrepancy of
(speed of light) × (60ns) = 299,792,458 ms-1 × 60 × 10-9s = 17.99 metreswould be necessary to explain the error.
They probably failed to take into account that the Earth is revolving, so the distance travelled is probably significantly less than they estimated!!!!!!!!
Way too slow. In the time the neutrinos/light took to travel from the accelerator in Geneva to the detector in Italy the earth rotate less than 1 metre. Besides, the neutrinos are travelling in the rest frame of the earth and don't "see" the rotation (OK for those who know what they're talking about - yes the earth is a non-inertial frame and SR isn't quite valid. Don't complicate matters) Just as you and I don't.
How do they know they got the same neutrinos they sent? Did they colour them or otherwise mark them to know for sure? :)
It isn't possible to tag the neutrinos, so they don't actually know for sure that every neutrino is one sent from CERN. It's possible that neutrinos from elsewhere are detected at the same time. Thus the experiment is repeated over and over again, tens of thousands of times, with beams of neutrinos, so that they can reduce the likelihood of being confused with neutrinos from elsewhere.