Neutrinos Travel No Faster Than Light, Says ICARUS 112
ananyo writes "Neutrinos obey nature's speed limit, according to new results from an Italian experiment. The finding, posted to the preprint server arXiv.org, contradicts a rival claim from the OPERA experiment that neutrinos could travel faster than the speed of light. ICARUS, located just a few meters from OPERA, clocked neutrinos traveling at the speed of light, and no faster, after monitoring a beam of neutrinos sent from CERN in late October and early November of last year. The neutrinos were packed into pulses just four nanoseconds long. That meant the timing could be measured far more accurately than the original OPERA measurement, which used ten microsecond pulses. The new findings are yet another blow to OPERA's results. Researchers there had announced possible timing problems with their original measurements. For many, this will pretty much be case closed."
Not surprising (Score:0, Informative)
If I remember my history correctly, they had a similar issue back in the 50-60's. In brief, some measurements they were making of neutrinos showed them traveling faster then light. Turned out to be time dilation on the part of the neutrinos that was screwing with the results.
This probably dates me, but... (Score:4, Informative)
299,792,458 m /s. It's not just a good idea. It's the law.
Re:"Another blow?" (Score:5, Informative)
which neatly summarizes the difference between how science is actually done, and how the media, including apparently /. cover science.
In real science when you do an experiment you just have results. You may not like the result, you may not want that to be the result, and you may think there is something wrong with the results. But that's what you did, that's what happened and if you can't figure out why the results are the way they are, well then you need the broader scientific community to help, and you write it all down in papers so that other people can learn from what happened to you.
Re:Didn't they already find an equipment error? (Score:5, Informative)
Neutrinos do seem to have mass, and thus do not actually travel at the speed of light. However, the mass is very small (and as far as I know still unknown), which means that since they are created with fairly large energies, they immediately start moving at extremely close to the speed of light. So close that we can't tell the difference.
Re:Didn't they already find an equipment error? (Score:5, Informative)
I'm curious that neutrinos went the speed of light at all. IIRC, don't neutrinos have mass?
Yes, but it's very small. For example, while the electron has a mass of about 0.5 MeV, the neutrino upper-bound has been pushed down from 50 eV, down to the prediction that the combined mass of all flavors of neutrinos must be under 0.3 eV.
So, it's around less than a millionth the mass of an electron. This means that it can obtain much faster speeds with the same amount of force.
Re:Didn't they already find an equipment error? (Score:5, Informative)
It was mostly about metrology: "How could we have gotten this wrong?" They never raised the idea that Relativity might be wrong. The original paper was very clear and cautious about it.
Re:Didn't they already find an equipment error? (Score:5, Informative)
Unfortunately, no. The neutrino oscillations tell us that mass must be present. That's the only way the mechanisms allow oscillations to happen at all. As long they can participate in mass interactions, they oscillate. But that's all we get out of it.
Re:Didn't they already find an equipment error? (Score:4, Informative)
You never say person A beat person B by 6 cm/s you say person A beat person B by 6 seconds.
That's because the winners of races are based on time, not instantaneous or maximum speed. Drag races always spout speed data, but the winner is the one who crosses the finish line first, not necessarily fastest.
"60 ns faster than the speed of light" is meaningless. "The neutrinos arrived 60ns sooner than they would have if they were travelling at c" isn't, as long as somewhere you could find out how far they went and then back out the speed they were going.
Re:Didn't they already find an equipment error? (Score:4, Informative)