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Physicists Report Evidence of a Faster-Than-Light Particle

In what would represent the biggest physics discovery in the century thus far if confirmed, researchers announced that they have measured particles traveling faster than the speed of light, which -- at least up to now -- has been the speed limit of everything in the universe.

[Image courtesy of the OPERA Collaboration]

Researchers from the OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment presented their results on Friday at a seminar at CERN, the European Organization for Nuclear Research, following a preprint post Thursday night on the science website arXiv.

But the OPERA researchers are the first to emphasize it is too early to speculate on the possible implications. Though the OPERA collaboration has performed thorough analysis of their measurements, the researchers acknowledge the possibility of an overlooked or presently unknown error that would skew the results. They said they are presenting their results to the physics community so that others could check their results and try to duplicate their experiments.

OPERA measured the transit time of particles known as muon neutrinos traveling approximately 455 miles from the CERN accelerator in Switzerland to the Gran Sasso Laboratory in Italy. Measuring over 15,000 neutrino arrivals at Gran Sasso, they found unexpectedly that the particles arrived 60 nanoseconds (billionths of a second) faster than light would have arrived. This represents a speed 0.002 percent faster than the speed of light, which travels at about 186,000 miles per second.

"It's quite simple; it's a classical measurement," said OPERA team member Dario Autiero of the Institute of Nuclear Physics in Lyon during Friday's seminar.

To determine the velocity, the team divided the distance the neutrinos traveled by the time it took them to complete their one-way trip. The team computed an overall accuracy of their time of flight measurements to within 10 nanoseconds. They had a sophisticated timing system that received signals from GPS satellites, which in turn contain precise atomic clocks.

Particles Shake Up Physics World

Through their measurements, the OPERA team knew the accuracy of the neutrino's 455-mile travel distance to within about 8 inches. On their journey, the neutrinos travel mostly through solid rock. At Gran Sasso they encountered a detector consisting of several "bricks" of photographic film in between sheets of lead. A tiny fraction of neutrinos interacted with the target to produce photons, which are observed with sensitive photodetectors.

"No matter how good the experiment is, I'm going to be skeptical until it's confirmed by an independent experiment because it's such a revolutionary result," said V. Alan Kostelecky, a theoretical physicist at Indiana University. "Extraordinary claims require extraordinary proof. It requires cross-comparisons and cross verifications and independent experiments. I'd be delighted if [a faster-than-light particle] were found. I'd really like to know if the effect is there and I'll only be convinced if it's detected in multiple ways."

Neutrinos Add Another Layer of Mystery

Neutrinos are one of the most common particles in the universe but also one of the hardest to detect. They are invisible and they rarely interact with other matter. Predicted by the physicist Wolfgang Pauli in 1930 to explain what was carrying away "missing energy" in nuclear reactions, neutrinos were finally detected in nuclear-beam experiments in 1956 in the United States by Frederick Reines and Clyde Cowan. Three types of neutrinos -- known as electron, muon and tau -- are known to exist. They are now known to carry away up to 99 percent of the energy in an exploding star.

"Neutrino speed hasn't been well characterized," said Alan Chodos of the American Physical Society. Chodos, along with Kostelecky and Avi Hauser, then at Yale University, published a series of theoretical papers starting in 1985 hypothesizing the possibility that neutrinos could be "tachyons," or particles that travel faster than the speed of light.

An exploding star known as Supernova 1987a offered potential clues on neutrino speed. It released a burst of electron neutrinos that arrived at the Earth earlier than the light from the explosion, but Chodos said that other effects such as light being trapped inside the exploding star could have accounted for the difference. The less sociable neutrinos may have zipped through. However, subsequent analysis of that supernova found that the speed of the neutrinos was within a part per billion of light speed -- at least 50 times smaller than the effect being reported today and consistent with a speed no bigger than that of light.

More recently, the MINOS (Main Injector Neutrino Oscillation Search) experiment in the United States reported in 2007 evidence of faster-than-light travel for muon neutrinos; however the statistical quality of the data was not at the level of the OPERA results.

During Friday's seminar, the most frequent questions from other scientists in the audience were if the OPERA collaboration had double-checked the precise distance from CERN to Gran Sasso, and if they fully accounted for effects such as tides, and Autiero responded that they had made multiple independent measurements of the distances.

'Physics Revolution' Reports May Be Greatly Exaggerated

If confirmed, faster-than-light particles would cause at the very least a revision in modern physics, which has rested on a foundation that includes the speed of light as a sort of cosmic speed limit. Although the concept of higher speeds opens the door to a whole host of possibly complicated issues, a faster-than-light particle does not necessarily undermine everyday notions of cause and effect. For one thing, said Chodos, if it only occurs in neutrinos they would not have a noticeable effect on everyday life.

Violating causality, added Kostelecky, requires that observing a chain of events in one frame of reference would be reversed in a second frame of reference, and this would not necessarily occur if neutrinos have special interactions with the medium in which they are traveling. According to Kostelecky, a class of theories known as Standard Model Extensions allows for faster than light particles which would include new phenomena, but not require radically rewriting the laws of physics.

Ben P. Stein, editorial manager of Inside Science News Service


  1. This comment has been removed by the author.

  2. Electromagnetic waves propagate at constant velocity, but that doesn't imply that matter respect this fact.

  3. That's right, according to conventional physics, matter with mass always travels slower than light speed. Only massless particles like photons travel at light speed. That's one reason why this experiment is so surprising.

  4. The paper doesn't discuss how the motion of the Earth was accounted for. Gran Sasso moves as much as 71 meters during the 2.4 ms travel time of the neutrinos. Depending on exactly what time of day and day of year, the distance that the neutrinos must travel can be larger or shorter by this amount (or any value in between). That is over 238 ns possible change when they reported only 60 ns change.

  5. That's an interesting suggestion, Bumpelo. The researchers took data at various times of the day, month and year. They didn't see any signs of fluctuations as a result of any of those time scales. Besides eliminating the effect I think you're suggesting, the data they took allowed them to account for any effect that seasonal temperature changes, the pull of the moon, and even continental drift might have on the experiment.

  6. Nikola Tesla the "father of free energy" as also the discoverer of the neutrino reported in 1932 that neutrinos are small particles, each carrying so small a charge and they travel with great velocity, exceeding that of light.

    Experimental tests of Bell inequality have shown that microscopic causality must be violated, so there must be faster than light travel. According to Albert Einstein's theory of relativity, nothing with nonzero rest mass can go faster than light. But zero rest mass particles can go faster than the light. Neutrinos have a small nonzero rest mass. Faster than light interactions are a necessity and they provide the non local structure of the universe. In any physical theory, it is assumed that there is some kind of nonlocal structure violates causality. If neutrinos are traveling faster than light, then neutrinos must be on the otherside of the light barrier going backwards in time, where the future can interact with the past.

    There are lots of theories and research regarding this matter including Cherenkov radiation, Standard Model Extension, Heim theory, Novikov selfconsistency principle, Casimir effect, Hartman effect, Casimir vacuum & quantum tunnelling, Tachyons, etc.

    - Nalliah Thayabharan

  7. Nalliah, thanks for the comment, but a lot of what your wrote is not quite right. Neutrinos have no charge, and no particle has less charge than an electron (except quarks, but they don't exist as free particles). Neutrinos weren't discovered until 1956, although Pauli proposed them in 1930.

    There are indeed lots of theories that suggest faster-than-light particles exist. So far, none have been confirmed. If this experiment turns out to be correct, perhaps one of those theories will be applicable, or maybe theorists will have to come up with a brand new one.

  8. That is, no charged particle has less charge than an electron (in other words, charge is quantized in multiples of the charge on an electron). Lots of particles have no charge.

  9. relativistic change has not taken into account.....the revolution of earth....the rotation of earth...and other things also....moreover nuetrinos are massless...they already a special case to mass speed relation....what OPERA trying to prove then...!!!

  10. The most important point of Special Relativity is that relative motion cannot cause the speed of light to change for any observer, and that nothing can exceed the speed of light. In other words, the revolution and rotation of the earth are definitely accounted for in Special Relativity.

    Also, neutrinos have low mass, but most experiments indicate that they have at least a little mass. Otherwise, if they were massless, they would always travel exactly at the speed of light, no faster and no slower.

  11. A point about particles travelling forward or backward in time. Particles do not travel down the time direction either forward or backward. dt/dt is meaningless is it not?

    And another point - the denominator of the Lorentz Factor is 0 at the speed of light. This does not mean that mass is infinite - my maths lessons many years ago told me that dividing by 0 is not defined.

    And finally the treatment of time is very different in relativity compared with quantum mechanics.

    If CERN is right has a veil been lifted?

  12. I'm a bit confused about your point regarding the Lorentz factor. As the speed approaches that of light, the Lorentz factor increases and goes to infinity, as you say. That means the amount of energy required to accelerate the particle grows to infinity as you approach c. That in turn implies that the force required to accelerate a particle goes to infinity as you get close to c. We know the force and we know the acceleration, so you can calculate the effective mass with the simple equation F=ma. Solving for m gives you m=F/a. Because F goes to infinity and c is just a finite number, mass must go to infinity too as velocity approaches c.

  13. Ergo, you're right, if the CERN result is correct, we will look at lots of things in whole new ways. It certainly sounds like lifting a veil to me.

    There's a very good chance that they're wrong though. I'm on pins and needles waiting to hear the answer either way.

  14. Buzz - The Lorentz factor comes from treating time as part of space-time. This implies "mass" increasing so requiring huge amounts of energy to get near the speed of light. Agreed.

    Our humble neutrino succumbs to quantum mechanics where time is treated in the classical way. It does appear that sub atomic particles get their mass hoisted up and, through clocks slowing down their lives extended approaching c. But the Lorentz Factor is not defined at v=c.

    Wikipedia describes quantum tunnelling as the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. Given the uncertainty principle could it be that some neutrinos simply jump from c - ∂v to c + ∂v. They are not going back in time - they are simply beating the photons to their destination.

    To allow this we have to debunk the time travel myth. Star Trek and Dr Who are brilliant but misleading us. I am baffled at some of he world's leading physicists proclaiming it is possible. There is no way you can move around 4 d space time in any direction. Nor can you move around in the classical quantum time.

    I believe nature is not going to allow infinities to exist - they are symptoms of our mathematical models not reality. I do hope these CERN results are right!

  15. What would the effects be if the cosmic speed limit was a wee bit higher?

  16. If the speed of light were slightly higher, or even a lot higher or lower, nothing much would change except that we'd have to explain why physicists have been measuring the wrong speed all these years. In fact, there have been some (as yet unconfirmed) measurements that suggest that the speed of light may change over time (we're talking billions of years here).

    No matter what the speed of light, the important point of Special Relativity is that no normal particle may exceed, or even equal, the speed of light if it has mass. Also, all tachyons (if they exist) must always move faster than the speed of light, and may never slow down to c. In either case, if neutrinos do indeed move faster than light, physicists will have their work cut out for them trying to figure out how it could happen.

  17. With regard to Kostelecky's comment in the last paragraph above, it is perhaps worth noting that the violation of causality he is talking would be different from the causality-within-the-forward-light-cone that one normally takes in special relativity, but would still be a benign causality violation. An example would be the case where event A caused a tachyon to be emitted, which in turn caused event B to occur. Events A and B are space-like separated. Through a cut-off in the energy-momentum spectrum, such as is employed in the model described in , B can be backward in time from A in certain inertial frames, but only at space-like separation, and the much more egregious kind of violation of causality in which B is within the backward light cone emanating from A can't happen. Hence an "anti-telephone", i.e., a device which could send a message backward in time to the sender, cannot be constructed using the particles created from the vacuum in such a model. Best regards,

  18. Could you address non-locality in this neutrino/photon reference?


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