Just had a massive (no pun intended) discussion about this with a few colleauges (one of which being an ex-nuclear/particle physicist) over a coffee.
Preamble: Neutrinos are notoriously difficult particles to detect. They have barely any mass, and pass through our entire planet effortlessly, without losing speed, or deviating from their course. That we can even detect them at all is still a wonder to me. Even more wonderous, is that CERN manage to accurately send a fairly concentrated beam of neutrinos in a particular direction in order to be detected by the OPERA detector at Grand-Sasso, Italy. It’s like being able to accurately tell which direction the cue ball on a snooker table will be travelling after it has bounced off every other ball on the table, but at a subatomic level where Newtonian physics does not necessarily apply.
Now: regarding the faster than light neutrinos:
The physicists are understandably sceptical about the results, due to it being inconsistent with the observed results from supernova explosions, and also due to it violating Einstein’s laws of relativity that have stood strong in the face of rapidly advancing scientific technology for over 100 years. The other issue is that if these neutrinos were to have travelled faster than the speed of light, then the energy required would be much *much* larger than the energy involved in supernova, which just isn’t possible at the LHC.
A theory, suggested half jokingly by friends and colleauges, was regarding the graph of particle mass against velocity, where as velocity tends towards c, the speed of light, the mass increases rapidly. The energy required to then continue to increase the velocity of a particle then tends to infinity. This is what we maths/physics folk call an asymptote (a point which the curve of a graph continually gets closer to, but never actually reaches, hence infinity). The suggestion was that maybe it wasn’t an asymptote, and that somewhere high up on the scale of energy, the point is reached where a particle can be made to travel at the speed of light, and we just hadn’t noticed it yet.
Whilst certainly an interesting idea, if we were to assume that Einstein’s theory of relativity is absolutely correct, it [the idea] is wrong in quite a few ways. Firstly, as previously mentioned, if the energy required is that high, then we can never have observed it, because CERN (and indeed possibly the world) does not have that kind of energy lying around. Secondly, especially if we observed the mass increasing and increasing, if we were to suddenly reach the speed of light, E=mc² dictates that all the mass in the particle suddenly disappeared. However, since physicists are also still trying to find out if the Higgs Boson exists, which is said to give mass to particles, it could well be that at this insanely high energy, the Higgs Boson is dismissed somehow and the particle loses its mass. Usually, one would say that the mass is lost because it has been converted to energy. But who knows… watch this space.
The only currently possible theoretical situation in which a particle can travel at the speed of light, is if it has no mass at all. Neutrinos were for a long time thought to have no mass, but more recent research with more and more advanced detectors has shown that neutrinos do have mass, albeit ridiculously small. They may be able to reach very close speeds to the speed of light, but should never be able to get there.
However, being good physicists, they’re not dismissing the result completely. They have released a paper (which can be found here: http://arxiv.org/abs/1109.4897) detailing the experiment, how it is set up, and the results produced. They’re also holding a seminar this afternoon to discuss the results with many other prominent theoretical physicists from around the world.
If it is shown that the results were bogus, it may be slightly embarrassing for the physicists involved in the OPERA experiment (who produce these results) who have been studying this for a while now, and have surely and steadily been improving the accuracy of their equipment and timing systems over the years. It’s the extremely costly and science revolutionising equivalent of carefully building up your Jenga tower higher and higher, and then suddenly having it crashing down.
A possibility is that maybe the OPERA detector at Grand Sasso simply got the wrong neutrinos from somewhere else. I’m sure they’ve almost certainly considered this, as they would’ve had CERN’s neutrinos arriving shortly afterwards, and they would’ve noticed that.
In light of all of this, I think the folks at OPERA did the right thing. They didn’t immediately dismiss or accept any new or existing theories, they were very careful to detail their results but still to say “We honestly don’t know”. It would be silly to try and say something for definite. If the results hold, Einstein’s 107 year old theory is broken, as is much of physics; if the results turn out bogus, OPERA need to do some serious re-thinking of their experiment.
However, we’re all just secretly hoping that a computer cocked up and failed to carry a one.
- My colleagues.
- http://indico.cern.ch/conferenceDisplay.py?confId=155620 (This contains a link to http://webcast.cern.ch/ where the event will be streamed. Note the time-zone! You don’t want to miss it!)