FTL neutrinos (or not)
October 3, 2011 By Steve Nerlich, Universe Today
Location of the Grand Sasso OPERA neutrino experiment in Italy - which receives a beam of neutrinos from CERN - and at faster than the speed of light, if you can believe it. Credit: CERN
The recent news from the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) neutrino experiment, that neutrinos have been clocked travelling faster than light, made the headlines over the last week – and rightly so. There are some very robust infrastructure and measurement devices involved that give the data a certain gravitas.
The researchers had appropriate cause to put their findings up for public scrutiny and peer review – and to their credit have produced a detailed paper on the subject, beyond just the media releases we have seen. Nonetheless, it has been reported that some senior members of the OPERA research team declined to be associated with this paper, considering that it was all a bit preliminary.
After all, the reported results indicate that the neutrinos crossed a distance of 730 kilometres in 60 nanoseconds less time than light would have taken. But given that light would have taken 2.4 million nanoseconds to cross the same distance – there is a lot hanging on such a proportionally tiny difference.
It would have been a different story if the neutrinos had been clocked at 1.5x or 2x light speed, but this is more like 1.0025x light speed. And it would have been no surprise to anyone to have found the neutrinos travelling at 99.99% of light speed, given their association with the Large Hadron Collider. So, confirming that they really are exceeding light speed, but only by a tiny amount, requires supreme confidence in the measuring systems used. And there are reasons to doubt that there are grounds for such confidence.
The distance component of the speed calculation had an error of less than 20 cm out of the 730 kilometres path, or 0.00003% if you like, over the data collection period. That’s not much error, but then the degree to which the neutrinos are claimed to have moved faster than light isn’t that much either.
But the travel time component of the speed calculation is the real question mark here. The release time of neutrinos from the source could only be inferred as arising from a 10.5 microsecond burst of protons from the CERN Super Proton Synchrotron (SPS) – fired at a graphite target, which then releases neutrinos towards OPERA.
The researchers substantially restrained the potential error (i.e. 10.5 microseconds) by comparing the time distributions of SPS proton release and neutrino detection at OPERA over repeated trials, to give a probability density function of the time of emission of the neutrinos. But this is really just a long-winded way of saying they could only estimate the likely travel time, more or less. And the dependence on GPS satellite links to time stamp the release and detection steps represents a further source of potential measurement error.
Some of the complex infrastructure required to infer the travel time of neutrinos across the OPERA experiment. Credit Adam et al.
It’s also important to note that this was not a race. The 730 kilometre straight-line pathway to OPERA is through the Earth’s crust – which is virtually transparent to neutrinos, but opaque to light. The travel time of light is hence inferred from measuring the path distance. So it was never the case that the neutrinos were seen to beat a light beam across the path distance.The real problem with the OPERA experiment is that the calculated bettering of light speed is a very tiny margin that has been measured over a relatively short path distance. If the experiment could be repeated by firing at a neutrino detector on the Moon say, that longer path distance would deliver more robust and more convincing data – since, if the OPERA effect is real, the neutrinos should very obviously reach the Moon quicker than a light beam could.
Until then, it all seems a bit premature to start throwing out the physics textbooks.
More information: Adam et al Measurement of the neutrino velocity with the OPERA detector in the CNGS beam.
A contrary view – including reports than not all the Gran Sasso team are on board with the FTL neutrino idea.
Source: Universe Today
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As stated in the article this was not a race between a neutrino beam and a beam of light, gravity would not have slowed the light because there was no light to slow. The experiment measured a beam of neutrinos travelling faster than the speed of light in a vacuum which is a well measured and documented speed. They neither performed nor needed to perform any experiments to determine the speed of light in a vacuum as scientists have been doing that for about a century now and have all come up with the same result. Since gravity is not constant at all places on earth if it did effect the speed of light then the speed of light would vary from place on the planet, which it doesn't.
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I was trying to think of any conceptual errors that could be taking place here, and I really don't see any.
Either it's an error in instrumentation, or the neutrinos really did move faster than light.
Reference frames and gravitational time dilaton from passing in a chord at a different layer in the earth's gravity well do not seem to offer an explanation consistent with the notion that "c" is the limit in Relativity.
Either the experiment is somehow in a measurement error, or it proves Special Relativity and General Relativity are not entirely correct.
Relativity does not even offer a mathematical construct to describe super-luminal velocities, because you end up with a pure, non-complex imaginary number for velocities exceeding "c". I.e. multiples of sqrt(-1)...
Perhaps it could be patched by assigning "c" as the limit of neutrino velocity, rather than limit of "light" velocity...
Oct 03, 2011
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This is problematic, because if the neutrino had no "real" component of time or space(length contraction,) then it could not be observed in the first place.
So then is "c" now going to be defined as the limit of neutrino speed?
Again, when "c" equals "velocity of light in a vaccuum", superluminal object has no "real" component of space-time motion, so how would you explain detecting it's motion?
Or is relativity disproven (i.e. "very close, but no cigar",) just like Newton's laws of gravity?
If "Imaginary" space-time really exists, then maybe warp travel is possible after all...
Oct 03, 2011
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I think you are missing the point actually. C is a mathematically derived value based on Einstein's Theory of Relativity. This is a fixed number which has been calculated using equations. Over many years and many different experiemnts this value has been experimentally confirmed within a variety of different environments. In fact, light never slows down, it simply appears to slow in the presence of a gravitational field due to the curvature of spacetime. Put simply, space is curved and light has to travel a greater distance, but at the same speed.
So what these scientists are saying is that the Neutrino's appear to have travelled faster than the mathematically derived (and universally accepted to date) value of C.
Oct 04, 2011
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The point here is, the exactly 3D space is perfectly flat and empty. If it contains something - I mean anything observable - it cannot be 3D anymore. This is simply crucial point and no way is over it.
So, if we have space full of tiny density fluctuations (which manifest itself like the CMBR noise), than it's legitimate to consider it as an extradimensions of the 3D space and to ask, whether all particles (including the particles of light) are traveling through it in the same way. The question is not, if neutrinos could do it - but WHY they should move differently from normal waves of light. This is where the hypothesis ends and actual theory begins.