In case you missed the news, a team of physicists reported in September that the tiny subatomic particles known as neutrinos could violate the cosmic speed limit set by Einstein’s special theory of relativity. The researchers, working on an experiment called OPERA, beamed neutrinos through the earth’s crust, from CERN, the laboratory for particle physics near Geneva, to Gran Sasso National Laboratory in L’Aquila, Italy, an underground physics lab. According to the scientists’ estimates, the neutrinos arrived at their destination around 60 nanoseconds quicker than the speed of light.
Experts urged caution, especially because an earlier measurement of neutrino velocity had indicated, to high precision and accuracy, that neutrinos do respect the cosmic speed limit. In a terse paper posted online on September 29, Andrew Cohen and Sheldon Glashow of Boston University calculated that any neutrinos traveling faster than light would lose energy after emitting, and leaving behind, a trail of slower particles that would be absorbed by the earth’s crust. This trace would be analogous to a sonic boom left behind by a supersonic fighter jet.
Yet the neutrinos detected at Gran Sasso were just as energetic as when they left Switzerland, Cohen and Glashow point out, casting doubt on the veracity of the speed measurements. “When all particles have the same maximal attainable velocity, it is not possible for one particle to lose energy by emitting another,” Cohen explains. “But if the maximal velocities of the particles involved are not all the same,” then it can happen.
An effect of this type is well known in cases where electrons have the higher speed limit (light speed), and light itself has the lower one because it is slowed down by traveling in a medium, such as water or air. Electrons, then, can move in the medium at a speed higher than the maximum speed of photons in the same medium and can lose energy by emitting photons. This transfer of energy between particles with different speed limits is called Cherenkov radiation, and it makes the reactor pools of nuclear power stations glow with a bluish light.
In the neutrinos’ case, Cohen and Glashow calculate that the wake would mostly consist of electrons paired with their antimatter twins, positrons. Crucially, the rate of production of these electron-positron pairs is such that a typical superluminal neutrino emitted at CERN would lose most of its energy before reaching Gran Sasso. Then again, perhaps they were not superluminal to begin with.
“I think this seals the case,” says Lawrence M. Krauss, a theoretical physicist at Arizona State University. “It is a very good paper.” So was Albert Einstein right after all? Einstein’s relativity superseded Isaac Newton’s physics, and physicists will no doubt keep trying to find glitches in Einstein’s theories, too. “We never stop testing our ideas,” Cohen says. “Even those that have been established well.”
This article was originally published with the title Why Neutrinos Might Wimp Out.
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24 Comments
Add CommentThe paper quotes Lawrence M. Krauss, theoretical physicist: "I think this seals the case.”
Reply | Report Abuse | Link to thisWhile a conflicting theory may bring the experimental results into question, only the identification and experimental verification of the erroneous measurement methodology would definitively prove the results invalid. Please see: "Faster-Than-Light Result to Be Scrutinized", http://news.sciencemag.org/scienceinsider/2011/10/faster-than-light-result-to-be.html
With respect to the particle in CERN, the > c particle. It happened to be a calculation error, where the speed of the GPS satellites, as well as their distance to the earth was not, or inverse corrected in the speed calculation. Meaning that the particle did NOT go faster than the speed of light! For more information about the speed of this particle see http://arxiv.org/PS_cache/arxiv/pdf/1110/1110.2685v3.pdf . As a matter a fact, you (Scientific American) have take notice about this because. http://blogs.scientificamerican.com/guest-blog/2011/11/03/im-shocked-shocked-to-find-there-are-neutrinos-going-on-here/ .
Reply | Report Abuse | Link to thisSo please, get your facts straight, before 'scientists' start dismissing valid theories!
Cheers
BTW, the example of electrons traveling faster than light in water by losing energy emitting photons is not directly applicable here: both electrons and photons propagating through water interact with (being absorbed and reemitted) water molecules (electrons) while detected neutrinos even traveling through the dense Earth can not have interacted with any other matter.
Reply | Report Abuse | Link to thisNobody said they interacted with any other matter. If they exceed the speed of light PERIOD, they will emit Cerenkov radiation. ANYTHING going at a superluminal speed will do this because the emitted radiation allows the neutrinos to enter a lower energy state. Basic physics. Thus Kraus' argument is pretty airtight really. Clearly it makes sense to quantify where the error in the experiment originated, but in truth there's basically no doubt about the speed of light. Superluminal velocities are simply non-physical and can't exist. If this weren't true then conservation of angular momentum and causality itself wouldn't exist.
Reply | Report Abuse | Link to thisOn the face of it, it seems to me that the argument of Cohn & Glashow is not itself consistent with special relativity.
Reply | Report Abuse | Link to thisTo be consistent, a faster-than-light particle must at least be a tachyon. For any tachyon there is a frame of reference in which it has a maximal, i.e. infinite, velocity. In that frame its relativistic mass & energy, is zero, which is presumably the basis of Cohen's “When all particles have the same maximal attainable velocity, it is not possible for one particle to lose energy by emitting another”. But that is true only if there exists an absolute reference frame in which all tachyons radiate particles until they have zero mass and energy. Otherwise, pick any other reference frame, and these "exhausted" tachyons will have "renewed" nonzero energy and radiate additional particles. But to postulate a special reference frame violates the principle of special relativity.
So what gives? This apparent contradiction casts more doubt for me on the theory than it does on the OPERA observation. In any case, as you pointed out, observation (if confirmed) will always trump theory.
I agree, but I suggest that the emission of Cerenkov radiation has been observed only during particle/media EM interactions, as energy is absorbed and reemitted by the media material.
Reply | Report Abuse | Link to thisIf that is the case, neutrinos are effectively propagating in a vacuum, not interacting with any material media.
Disproving an unexplained phenomenon with a theory is not exactly good science.
Reply | Report Abuse | Link to thisWhether the neutrinos were traveling at superluminal speed or not needs to be worked out in laboratories, not on paper.
I wonder if you give any credence to the claim that alien-reproduction technology, built in USA, has super-luminal capability as described by Steven Greer's Disclosure Project? It's a long video so jump to about 1:37:54 here: ww.youtube.com/watch?v=PjQqv2bgmwE&feature=related
Reply | Report Abuse | Link to thisWe cannot just dismiss an experimental result on the basis of theory. It's the other way around. Theories are revised on the basis of experimental results. Newtonian mechanics was replaced by special relativity theory when the Michelson-Morley experiment showed the speed of light is constant independent of earth's relative motion.
Reply | Report Abuse | Link to thisTo physicists trying to disprove superluminal neutrinos, show the error in OPERA's experiment. Otherwise, the result stands until proven wrong.
Science is both about experiment/detection and theory or explanation. Neither stands alone. It took many other experimental results before special relativity gained ground.
Reply | Report Abuse | Link to thisCohen and Glagow explanation appears to be sound based on known physics. However if quantum entanglement ocurrs enroute or some deeper level physics are involved then the faster than light results may occur but for reasons not so far expressed by theorists. If so, this would still protect Special Relativity within its range while allowing faster than light detections due to another rule book.
It is too early to jump to conclusions but the possibilities have not been ruled out.
I am so furious on Scientific American. Why does this article-writer got a chance to write his vision on the faster-than-light-neutrino's. Is it Public Promotion from the fear to violate existing theories? I requested more than once to have my research told by Scientific American in an article. Well, I asure you there is a new vision possible on this faster-than ligt neutrino's. Look at my website (www.darkfieldnavigator.com), look at my paper[1]. It is a real fundamental theory: Neutrino's can go faster than light indeed! And beyound that: It is independent of the trajectory!! I theoretically calculated the the exact time-gain of the neutrino's compared to light in vacuum. Moreover: it is related to a new cosmological hypothesis. SA-Editorium: call me on +31 (0) 36 5499701. Or email me. I challange Scientific American: Write about my vision too! Don't exclude me from the frontier of science.
Reply | Report Abuse | Link to thisKind Regards,
Dan Visser (independent cosmologist), Almere, the Netherlands.
Reference[1]: http://vixra.org/abs/1110.0030
Exactly how would you choose another reference frame in which a particle moving at infinite speed in one reference frame, did not still move at infinite speed? (The reference frames can only move at finite speed relative to each other.)
Reply | Report Abuse | Link to thisNot that it matters, as it isn't really what the sentence you quoted was about anyway.
DURGADAS DATTA published ETHER=GRAVITY=DARK ENERGY theory of gravitoethertons in his balloon inside balloon theory of matter and antimatter universe on opposite entropy path producing gravitoethertons at common boundary by annihilation of matter and antimatter and injected into our universe to produce all drama which we are noticing now. Einstein and Newton both are not fully correct and NEW REVISED SCIENCE WILL SHED LIGHTS ON QUANTUM MECHANICS. fOR FULL DETAILS PLEASE WRITE TO --durgadas.ddatta@gmail.com
Reply | Report Abuse | Link to thisUh, how is the theory about Cerenkov Radiation any more proven than the Theory of Relativity?
Reply | Report Abuse | Link to thisHas there been even a single experiment where something has been able to travel faster than light by emiting Cerenkov radiation? At least the Theory of Relativity has withstood many tests.
I hope the following is not too unclear. It is, however, nothing that any person knowledgeable about relativity should find seriously amiss.
Reply | Report Abuse | Link to thisA curious property of special relativity is known as "relativity of simultaneity". It happens that if you correctly determine, using whatever method you like, that two instantaneous events, such as light flashes, happen simultaneously at two separate locations A and B, this is true only in a frame of reference in which you are motionless. A second observer moving relative to you along a line parallel to the path joining A & B will be equally correct in determining in his frame of reference that A occurs before B, and yet another, moving in the opposite direction will determine that B occurs before A. If a tachyon travels between A and B at such a speed that its arrival and departure coincide with the two light flashes, then for you the tachyon travels instantaneously between A & B. But in the second observer's reference frame it moves from A to B at a finite but still greater than light speed, and in the third observer's reference frame, it does likewise from B to A. Each of you are correct because the definition of simultaneity depends upon the observer's frame of reference (in which he is motionless). This is bizarre but true.
It also happens that the tachyon moving at infinite speed in your reference frame cannot radiate bremsstrahlung particles because it has zero energy (technically, its 4-momentum vector has no time component). But it can for the other two observers, because it non-zero energy, and may have enough to radiate bremsstrahlung particles in their reference frames.
This is the paradox underlying my earlier post, because although observers are permitted to disagree on the order of events, they *cannot* disagree on whether or not the tachyon radiates bremsstrahlung particles.
Very interesting! But how is it then that just three days ago the OPERA at theCERN made the same experiment and confirmed the finding?
Reply | Report Abuse | Link to thisExactly. The bremsstrahlung predicted by Cohn & Glashow appears incompatible with special relativity because it needs a preferred frame of reference (no relativity of simultaneity) or results in the above paradox.
Reply | Report Abuse | Link to thisA theory needs experimental results to stand. An experimental result does not need theories to stand. Special relativity would not stand without supporting experimental results.
Reply | Report Abuse | Link to thisMichelson-Morley experiment measured the speed of light. Their result would stand whether or not they had a theory to explain the phenomenon. Unless their measurement was wrong.
New tests conducted at the Gran Sasso National Laboratory of INFN by the OPERA Collaboration, with a specially set up neutrino beam from CERN,confirm so far the previous results on the measurement of the neutrino velocity. The new tests seem to exclude part of potential systematic effects that could have affected the original measurement.
Reply | Report Abuse | Link to this"A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny - said Fernando Ferroni, president of Italian Institute for Nuclear Physics (INFN) - The experiment OPERA, thanks to a specially adapted CERN beam, has made an important test of consistency of its result. The positive outcome of the test makes us more confident in the result, although a final word can only be said by analogous measurements performed elsewhere in the world".
"One of the eventual systematic errors is now out of the way, but the search is not over. They are more checks of systematics currently under discussion, one of them could be a synchronisation of the time reference at CERN and Gran Sasso independently from the GPS, using possibly a fiber" said Jacques Martino, Director of National Institute of Nuclear and Particle Physics of French CNRS.
This beam was characterized by a better time definition of the proton extraction time, by having about 3 nanoseconds long bunches spaced by as much as 524 nanoseconds. In this way, compared to the previous measurement, the neutrinos bunches are narrower and more spaced from each other. This permits to make a more accurate measure of their velocity at the price of a much lower beam intensity: only 20 clean events have been collected by OPERA in this phase. Additional events could be eventually collected in the next year run.
I carefully read the paper by Glashow. However I do not think "it seals the case". For more than twenty years theoreticians (Krauss and Glashow included) told us (I am an experimentalists) that we should test for physics beyond what we know (and they proposed supersymmetry, multidimensions etc). All kind of weird scenarios. Now we have one experiment with an unexpected result and they want us to throw away on a theoretical basis? Naah! More experiments, that's what we need. Minos (in the US) and T2K (in Japan) will have to say. That's the real answer folks. It is possible that OPERA has a flaw somewhere...but you are not going to convince anybody on the basis of theoretical arguments.
Reply | Report Abuse | Link to thisThanks very much for your further comments! They helped at least this reader who is not well versed in relativity!
Reply | Report Abuse | Link to thisCan you by chance comment on the applicability of a relativistic boost to the OPERA experiment, and whether gravitational and/or rotational effects might be skewing the experimental neutrino propagation timings when compared to the calculated time-of-flight for photons, determined as the speed of light in a vacuum over the estimated ~730 km traversal distance?
Reply | Report Abuse | Link to thisI've stumbled on the following references that I can't reasonably evaluate...
http://en.wikipedia.org/wiki/Neutrino#Artificial
“Some particle accelerators have been used to make neutrino beams. The technique is to smash protons into a fixed target, producing charged pions or kaons. These unstable particles are then magnetically focused into a long tunnel where they decay while in flight. Because of the relativistic boost of the decaying particle the neutrinos are produced as a beam rather than isotropically. Efforts to construct an accelerator facility where neutrinos are produced through muon decays are ongoing.[54] Such a setup is generally known as a neutrino factory.”
http://en.wikipedia.org/wiki/Lorentz_Boost
“It reflects the surprising fact that observers moving at different velocitiesmay measure different distances, elapsed times, and even different orderings of events.”
Any help would be appreciated!
To be more specific, is there any possibility that some relativistic effect (not considered by the standard geodesic procedures used to estimate the ~730 km distance traversed) have reduced the actual distance traversed by the experimental neutrinos, in relation to the calculated distance traversed by speed of light photons?
Reply | Report Abuse | Link to thisWhile it's natural for us to consider that the shortest distance between two points is, in Euclidean geometry, a straight line, I understand this might not always be a correct premise in general relativity...
Thank you very much giorgioch. I completely agree; I do not think "it seals the case". NOT PHYSICS!
Reply | Report Abuse | Link to this"More experiments, that's what we need. Minos (in the US) and T2K (in Japan) will have to say. That's the real answer folks." PHYSICS! Well said giorgioch.
Just wanted to add...Given that some people have promised to give away their children, or eat their shorts on TV if the the CERN/OPERA FTL muon-neutrino results hold up, the following request seems like a small favor to ask:
Mr. Krauss, if further experiments over the next couple of years conclusively show that the muon-neutrinos are indeed moving faster than light could you please find some other way to pay your mortgage. Thanking you in advance...