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What next for neutrinos?

The views expressed are those of the author and are not necessarily those of Scientific American.

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To catch a neutrino (MINOS)

For a ghostly type of particle, oblivious to even the massive bulk of a star or planet, neutrinos sure can generate a fuss. In the 1960s they created a stir by seemingly appearing from nuclear processes in our Sun’s core at a third of the anticipated rate – the so-called solar neutrino “problem“. In the 1980′s they seemed like they might offer a solution to the nature of cosmic “dark matter” – except they didn’t because their speedy nature would have erased too much of the small structure in a young universe, those annoyances like galaxies. And all along we’ve not quite managed to pin down their actual stationary mass, although it must be small, probably less than a millionth of the rest mass of an electron.

If any other recognizably intelligent life exists somewhere else in this vast cosmos one can only presume that they too have spent an inordinate amount of time scratching whatever part of their anatomy they scratch when puzzled. Neutrinos are unlikely to be any more readily accessible to alien beings composed of normal matter than they are to us. Last week neutrinos created a fuss again here on planet Earth. As reported by countless tweets, posts, reports, and sound-bites the neutrino detection experiment OPERA announced their analysis suggesting that high energy (17 giga-electron-volt, GeV) muon-neutrinos might be traversing 730 kilometers through the Earth’s crust at a speed slightly greater than the free-space speed of light by approximately 0.00025% (plus or minus about 0.00006%).

Exactly how fast would we have expected a (sub-luminal) neutrino to be moving? Well, just like if I asked this question of a tennis ball or a speeding train, it depends on its energy. If, for the sake of argument, the heaviest neutrino weighs in at about 3 eV  (for comparison a normal electron has a mass of about 510,000 eV) and it’s moving ultra-relativistically so that its total energy is about 10 giga-electron volts, its speed will be less than the speed of light by a mere 0.00000000000000001 %. Theories proposing that neutrinos can take “shortcuts” through extra (large) dimensions – described as going “off-brane” – predict velocities that might differ from (and exceed) the speed of light by as much as 0.01% at similar particle energies.

If the OPERA result were correct it would point to some extraordinary things. We’ve all grown up understanding that the only sensible thing for matter to do is to never exceed (or indeed reach) the speed of light. It’s a fundamental piece of Einstein’s special theory of relativity, which is one of the best verified theories in modern physical science. I won’t go into the details here, but for matter with mass to exceed lightspeed there are a large number of headaches, not least of which are the most basic ideas of causality – at both the microscopic and macroscopic scales. So its critical to consider what’s next for neutrinos? Where do we go from here?

Two main avenues are obvious. The first is that others analyze and re-analyze the OPERA results, scrutinizing every aspect of the experiment to see if there is an explanation for their result that does not require super-luminal neutrinos – it might be mundane, it might be complex, and it could even be unexpected. The second is for someone to perform another experiment somewhere else that makes the same kind of measurement, but entirely independently.

Enter the particle hunters of Fermilab, or rather re-enter the particle hunters of Fermilab. Back in 2007 the MINOS experiment presented the intriguing results of a very similar test of the speed of high energy neutrinos. Much like OPERA, MINOS employs an artificial beam of neutrinos (at slightly lower energies of 3 giga-electron volts) that traverses a similar distance through the Earth – in this case traveling 734.2986 kilometers from just outside Chicago to a 5.4 thousand ton detector sitting 700 meters down in a former iron mine in northern Minnesota. Four years ago the MINOS collaboration published a constraint on the velocity difference between neutrinos and light of about 0.005% with an uncertainty of 0.003% at a 68% confidence level – in favor of super-luminal motion. It didn’t get the same fanfare with the public, but it definitely set tongues a-wagging in the particle physics community.

It now looks like the MINOS people are going to both go back in and re-analyze their data in an effort to reduce their level of uncertainty, and to try to perform some new experiments. This is clearly now critical, but it will take some time, at least 6 months for the analysis and perhaps a year or more to run further actual experiments. So, the good news is that the two obvious followups to the OPERA result seem to be underway, the bad news is that we are going to have to wait a little before we know the results.

In the meantime, as with the much discussed neutrino results of Supernova 1987a (if super-luminal like the OPERA claim, the neutrinos from stellar core-collapse would have preceded the light of the supernova by about 4 years, which they didn’t), we may want to cast our gaze at the natural world. If by some chance particles like neutrinos really can trip the light fantastic, are there other cosmic phenomena that would betray this behavior? We should definitely be on alert and, above all, try not to blink.


Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Rakesh1961 12:21 pm 09/30/2011

    Is there any way we can explain this and still maintain the supremacy of Special theory of Relativity?

    The problem is that we have associated every thing with the speed of light.

    Yes speed of light HAS to be constant in every frame in vacua and it is.

    But is it possible that the ‘c’ is constant because of some other phenomena or property of the so called SPACETIME, and that property in turn determines speed of clock or other phenomenas.

    You may say , what diffrence does it make?

    But it does , a great deal. You can interpret everythig in a complete new frame of things.

    According to me Nutrinos will travel at ‘c’ in vacua but faster than ‘c’ in material media.

    Do not see red, It may still validate S T R.

    Link to this
  2. 2. priddseren 1:13 pm 09/30/2011

    It is likely the speed of nutrinos was simply an error in measurment.

    However, assuming it is not an error, it could be that the speed of light is not the fastest speed in the universe. Light also behaves differently because unlike everything else, relativity does not apply. You can’t add the speed of a car to the light from its headlight as you could throwing an object forward from the car. So the speed of light may only apply to light.

    We also know space itself, expands faster than light, so that makes one object that can break the limit.

    Nutrinos can’t yet be measured for Mass. Perhaps those particles do not have mass as it is understood for other particles, which is why it is not measureable by us, we are using the wrong definition. We can’t measure actual gravity either. We only measure the effects of gravity making it a second force/particle/unknown we do not actually understand well precisely because we dont measure it any better than we measure a nutrino.

    Certainly interesting and personally I hope the speed issue is proven true, it will make for a very interesting few years of discussion as this is researched for answers.

    Link to this
  3. 3. Luis Gonzalez-Mestres 5:18 am 10/1/2011

    I was very much interested in this neutrino result by OPERA, as I have been suggesting since 1995 the possible existence of particles with positive mass and energy able to travel faster than light and directly violating Lorentz symmetry ( see and for a recent review, ). A mixing with superbradyons was a possible hypothesis to explain the OPERA result ( ).

    But unfortunately, it does not seem that the critical speed anomaly attributed by OPERA to the muon neutrino can be made compatible with well-established experimental facts in Astrophysics and Particle Physics.

    The point is the following. To be able to produce such a neutrino at high energy, pions and kaons must have the same critical speed anomaly, which is in this way transmitted to all hadrons including the proton. But this leads to a series of unwanted properties for high-energy particles and high-energy cosmic rays.

    See for more details my paper “Astrophysical consequences of the OPERA superluminal neutrino”, .

    Luis Gonzalez-Mestres, CNRS (France)

    Link to this
  4. 4. Wilhelmus de Wilde 10:33 am 10/1/2011

    A neutrino is nor a photon nor a tachyon, perhaps in his voyage to the “measuring” point in between is was something else…

    always keep on thinking FREE


    Link to this
  5. 5. okburt75 12:59 pm 10/1/2011

    The speed of light is determined on Earth in a vacuum manufactured in a laboratory. It is questionable that such a vacuum is identical to that of space – for that matter, space is not a perfect vacuum, it contains, among other items, particles (mass). Neutrinos are said to pass, unhindered, through mass, whereas the speed of light is dependant upon the medium it is traveling through. Consequently, if the above is correct, neutrinos would win any race with light in space, except in a perfect vacuum, if such exists, when it would be a tie.

    Link to this
  6. 6. Leonardo Rubino 1:12 pm 10/1/2011


    I do not agree with the superluminal neutrinos news. The difference they found with respect to the speed of light is very small, so some errors in the calulations must have been made. Neutrino is not faster than light.
    The Special Theory of Relativity (STR) of Einstein, through the principle of the speed limit, makes the magnetic force come from the electric one and the magnetic force is an electric force, as physicists know; an easy demonstration of that can be found in chapter 3 of my file at the following link (also English inside):

    If you get rid of the speed limit principle, the magnetic field cannot exist anymore.

    Moreover, as c=1/square root of(epsilon x µ), if you change c with a c’>c, then you have to accept a µ’<µ, so you have to accept different intensities of magnetic fields from a given electric current, so you have to get rid of the electromagnetism, but it's describing so well the currents, the fields, the real world etc. Therefore, there's a mistake in the computation of the speed of neutrinos, in the calculations on the run lenght, in the interaction time calculations, during the generation and also the detection of those evanescent particles!

    (another interesting file, on this subject):


    Leonardo Rubino.

    Link to this
  7. 7. ImageIs 2:55 pm 10/11/2011

    The OPERA results are not necessarily in contradiction with the supernova 1987 results. Not if the OPERA neutrinos move only at c and the difference between the measurements and c is attributable to the speed of the Earth relative to space (admitting that space be discrete rather than continuous).

    A theory linked from an article found at suggests exactly that.

    Link to this
  8. 8. David Brown 6:48 am 11/28/2011

    Cohen and Glashow have persuasively argued that the OPERA neutrinos are not superluminal.
    Consider 3 possibilities for explaining the OPERA neutrino anomaly:
    (1) experimental error;
    (2) new physics extending quantum field theory;
    (3) new physics extending general relativity theory.
    Is Milgrom’s MOdified Newtonian Dynamics (MOND) correct?
    By carefully studying the paper by P. Kroupa, B. Famaey, K.S. de Boer, J. Dabringhausen, M. Pawlowski, C.M. Boily, H. Jerjen, D. Forbes, G. Hensler, M. Metz, called “Local-Group tests of dark-matter concordance cosmology. Towards a new paradigm for structure formation”,…523A..32K A&A 523, 32 (2010), one can learn that something is seriously wrong with the standard model of cosmology.
    “There is a tremendous amount of evidence for dark matter. Yet all this evidence is based on the assumption that Newton’s theory can be safely applied to the scales of galaxies.” — Stacy McGaugh “Mond over matter”, 2002
    Is the currently accepted theory of dark matter (DM) fatally flawed? Is there some new physics in gravitational theory that changes time by increasing the predicted gravitational slowing of time? Why might a GPS timing calibration problem explain the OPERA anomaly? My thinking is: GPS timing is CONSISTENTLY wrong by an extremely small fraction if and only if Fernandez-Rañada’s idea about anomalous gravitational acceleration of clocks happens to be correct if and only if the -1/2 in the standard form of Einstein’s field equations should be replaced by -1/2 + dark-matter-compensation-constant if and only if dark-matter-compensation-constant is approximately sqrt((60±10)/4) * 10^-5 . “The Pioneer anomaly as acceleration of the clocks”
    Does an understanding of dark matter require a paradigm shift? Are those who create paradigm shifts often ignored or ridiculed?
    The paradigm was: crystals are ordered and periodic — no exceptions. … For a couple of years I was alone. I was ridiculed. I was treated badly by my colleagues and my peers. … The community of nonbelievers was very large in the beginning. In fact, it included everybody. — Dan Schechtman Prof. Dan Schechtman 2011 Nobel Prize Chemistry Interview with ATS, YouTube

    Link to this
  9. 9. Aiya-Oba 2:36 pm 12/12/2011

    For complete realization of the unity (oneness) of Space, it’s new eon crucial, that Photon, in all its glory, is comprehended as natural lighthouse and herbinger of the ever-elusive neutrino – the quantum of Blackhole; the perfect fundamental equator, of the gravitation and radiation pair (self-contradiction) properties of Space-itself (Cosmos).

    Link to this
  10. 10. hab_kab 12:41 am 02/14/2012

    I am Hamid Reza karimi,my paper by title “Explaining how and why the muon neutrinos flow faster than the
    speed of light in the OPERA neutrino Experiment”was published on vixra eprint:
    This article gives answer to the four following questions about the opera experiment
    1 – Why do neutrinos flow faster than speed of light but the electron doesn’t.
    2 – Why there is no deformity in energy of the neutrinos .
    3 – Why does not cosmic neutrinos break the speed of light.
    4 – In which area The laws of relativity are true.
    Best regards,

    Link to this
  11. 11. Leonardo Rubino 3:56 pm 07/7/2012

    It’s very sad to be always doubtful and suspicious with news coming from what could be the most precious and charming thing: the world of science and of the scientific knowledge.

    Unfortunately, many facts, not negligible, really push you to suspicions and criticisms. YOU CANNOT PRETEND NOT TO NOTICE that, just yesterday, they told us two and two is nine; I’m talking about the story of superluminal neutrinos, later corrected.
    That news shouldn’t even have been proposed and all those who learnt with passion even just some rudiments of relativity and electromagnetism, should immediately keep far; on the contrary, many eminent scientists didn’t do that, but welcomed.

    Read my whole opinion, with all the mathematical and physical explanations, at the following link:

    And just to put further irons in the fire, what to say about the dying and unjustifiable dark matter?

    Finally, what to say about the recent news on the Higgs boson, now found: first of all, the scientific environment from which that news comes from is the
    same one, again. Furthermore, this kind of announcements have got a behaviour in common: they all diverge, instead of converging to a point of common deep knowledge of the Universe. In fact, such a boson just apparently brings an answer to us (on what it would do), but, at the same time, it also brings
    another half a dozen of new questions (on what it really is and on how it would do what they say it does).
    By summing it up a bit, Higgs boson would give a mass to other particles, through the friction among them and the Higgs’ field!
    It’s like if there is a guy, whose name is Anthony (and I don’t know him) and after long researches and investigations I’m told that Anthony has been
    introduced to Jennifer by Josephine, through Michael. And so, now, I still don’t know Anthony, but not only: from now on, I do not know also Jennifer, Josephine and Michael…
    In fact, the echo of the news on the Higgs’ boson has not yet faded out and there is already who has (re)started to hunt the superhiggs, in environments
    with 43 dimensions!

    Thank you for your attention.



    Leonardo Rubino.

    Link to this

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