Faster than the speed of…wait…what?
The leading theories disclaiming the OPERA team’s faster than light neutrinos.
In the past few weeks the Physics community has been in an uproar over the announcement that the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) team had discovered that Neutrinos could travel faster than the speed of light. A plethora of papers have been written to explain away these findings, and most of them attribute it to an error in measurement.
There are however two theories that seem to be gaining popularity amongst all the ideas flying around. The first one has to do with Gravity, and how it effects clocks. Carlo R. Contaldi, in his paper “The Opera neutrino velocity results and the synchronisation of clocks”1 poses the question as to whether or not the OPERA team has properly taken into account the differences in clocks between one site and the other. There is a small difference that is due to gravity. According to Contaldi, “One-way speed measurements such as these inevitably require a convention for the synchronisation of clocks in non-inertial frames since the Earth is rotating.”
Basically what this article is saying, is they use once clock to record the start time, and another clock to record the end time, while the two clocks themselves have not been properly synchronized with each other. Because the Earth is rotating, it means that the two clocks are in a state of constant acceleration. This means that the reference frame is non-inertial. According to the Theory of Relativity which this experiment has threatened, only observers in an inertial (IE non-accelerating) frame are equivalent.
The OPERA team attempted to solve this issue by using a single GPS clock to time stamp both clocks at either end, and then used a second atomic clock transported from one site to the other to calibrate the difference in time signals. The problem with this as stated by Contaldi is that in essence, a single GPS satellite is only accurate within 100 ns on average. The traveling clock which they use to attempt to get a more accurate reading is traveling in an accelerating frame, which like the baseline clocks themselves, is due to the rotation of the Earth. The details of the issues with this can be read in the original article, but in summery the three relativistic time distortions are due to moving the clock through a non-uniform gravitational potential, a Doppler like effect due to the velocity of the traveling clock with respect to the rotating Earth, and lastly the Sagnac2 effect also due to the rotation of the Earth.
These are some pretty hefty claims, and it will be interesting to see if the OPERA team responds to them. The other big article that has some pretty legitimate claims is one that does not point to any error, but rather the lack of specific findings that should be seen if the neutrinos truly were traveling faster than light. Specifically the paper3 by Andrew G. Cohen, and Sheldon L. Glashow says that if the neutrinos were indeed traveling at that speed that they would undergo severe energy loss, “..causing the beam to be depleted of higher energy neutrinos”.
These two papers are just a small fraction of the responses that continue to come in about the neutrino results. There will be a lot of information and data that will need to be gone through before OPERA can confirm their results. If they do it will be a shattering blow to modern physics.
Chris Birkinbine is a Senior Physics Student at University of Idaho in Moscow, Idaho. His Applied Physics curriculum combines Physics, Electrical and Mechancial Engineering, and Material Science, as well as a personal interest in Information Technology. You can follow Chris Birkinbine at his personal site www.cbirkinbine.net , or his twitter feed cbirkinbine you can email him at [email protected]