Neutrinos Obey The Speed Limit, After All


Neutrinos have been cleared of allegations of speeding, according to an announcement issued today by CERN and the ICARUS experiment at Italy’s Gran Sasso National Laboratory. Turns out they travel exactly as fast as they should, and not a nanosecond more.

The initial announcement in September 2011 from the OPERA experiment noted a discrepancy in the measured speed of neutrinos traveling in a beam sent to the detectors at Gran Sasso from CERN in Geneva. If their measurements were correct, it would have meant that the neutrinos had arrived 60 nanoseconds faster than the speed of light allows. This, understandably, set the world of physics a bit on edge as it would effectually crumble the foundations of the Standard Model of physics.

As other facilities set out to duplicate the results, further investigations by the OPERA team indicated that the speed anomaly may have been the result of bad fiberoptic wiring between the detectors and the GPS computers, although this was never officially confirmed to be the exact cause.

Now, a a statement from CERN reports the results of the ICARUS experiment — Imaging Cosmic and Rare Underground Signals — which is stationed at the same facilities as OPERA. The ICARUS data, in measuring neutrinos from last year’s beams, show no speed anomaly — further evidence that OPERA’s measurement was very likely a result of error.

The full release states:


The ICARUS experiment at the Italian Gran Sasso laboratory has today reported a new measurement of the time of flight of neutrinos from CERN to Gran Sasso. The ICARUS measurement, using last year’s short pulsed beam from CERN, indicates that the neutrinos do not exceed the speed of light on their journey between the two laboratories. This is at odds with the initial measurement reported by OPERA last September.

What neutrinos look like to ICARUS. (LNGS)

“The evidence is beginning to point towards the OPERA result being an artefact of the measurement,” said CERN Research Director Sergio Bertolucci, “but it’s important to be rigorous, and the Gran Sasso experiments, BOREXINO, ICARUS, LVD and OPERA will be making new measurements with pulsed beams from CERN in May to give us the final verdict. In addition, cross-checks are underway at Gran Sasso to compare the timings of cosmic ray particles between the two experiments, OPERA and LVD. Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements. This is how science works.” 

The ICARUS experiment has independent timing from OPERA and measured seven neutrinos in the beam from CERN last year. These all arrived in a time consistent with the speed of light.

“The ICARUS experiment has provided an important cross check of the anomalous result reports from OPERA last year,” said Carlo Rubbia, Nobel Prize winner and spokesperson of the ICARUS experiment. “ICARUS measures the neutrino’s velocity to be no faster than the speed of light. These are difficult and sensitive measurements to make and they underline the importance of the scientific process. The ICARUS Liquid Argon Time Projection Chamber is a novel detector which allows an accurate reconstruction of the neutrino interactions comparable with the old bubble chambers with fully electronics acquisition systems. The fast associated scintillation pulse provides the precise  timing of each event, and has been exploited for the neutrino time-of-flight measurement. This technique is now recognized world wide as the most appropriate for future large volume neutrino detectors”.


An important note is that, although further research points more and more to neutrinos behaving as expected, the OPERA team had proceeded in a scientific manner right up to and including the announcement of their findings.

“Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements,” the ICARUS team reported. “This is how science works.”

See more news from CERN here.

Faster Than Light? More Like Faulty Wiring.


You can shelf your designs for a warp drive engine (for now) and put the DeLorean back in the garage; it turns out neutrinos may not have broken any cosmic speed limits after all.

Ever since the news came out on September 22 of last year that a team of researchers in Italy had clocked neutrinos traveling faster than the speed of light, the physics world has been resounding with the potential implications of such a discovery — that is, if it were true. The speed of light has been a key component of the standard model of physics for over a century, an Einstein-established limit that particles (even tricky neutrinos) weren’t supposed to be able to break, not even a little.

Now, according to a breaking news article by Edwin Cartlidge on AAAS’ ScienceInsider, the neutrinos may be cleared of any speed violations.

“According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer,” Cartlidge reported.

The original OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment had a beam of neutrinos fired from CERN in Geneva, Switzerland, aimed at an underground detector array located 730 km away at the Gran Sasso facility, near L’Aquila, Italy. Researchers were surprised to discover the neutrinos arriving earlier than expected, by a difference of 60 nanoseconds. This would have meant the neutrinos had traveled faster than light speed to get there.

Repeated experiments at the facility revealed the same results. When the news was released, the findings seemed to be solid — from a methodological standpoint, anyway.

Shocked at their own results, the OPERA researchers were more than happy to have colleagues check their results, and welcomed other facilities to attempt the same experiment.

Repeated attempts may no longer be needed.

Once the aforementioned fiber optic cable was readjusted, it was found that the speed of data traveling through it matched the 60 nanosecond discrepancy initially attributed to the neutrinos. This could very well explain the subatomic particles’ apparent speed burst.

Case closed? Well… it is science, after all.

“New data,” Cartlidge added, “will be needed to confirm this hypothesis.”

See the original OPERA team paper here.


UPDATE 2/22/12 11:48 pm EST: According to a more recent article on Nature’s newsblog, the Science Insider report erroneously attributed the 60 nanosecond discrepancy to loose fiber optic wiring from the GPS unit, based on inside “sources”. OPERA’s statement doesn’t specify as such, “saying instead that its two possible sources of error point in opposite directions and it is still working things out.”

OPERA’s official statement released today is as follows:

“The OPERA Collaboration, by continuing its campaign of verifications on the neutrino velocity measurement, has identified two issues that could significantly affect the reported result. The first one is linked to the oscillator used to produce the events time-stamps in between the GPS synchronizations. The second point is related to the connection of the optical fiber bringing the external GPS signal to the OPERA master clock.

These two issues can modify the neutrino time of flight in opposite directions. While continuing our investigations, in order to unambiguously quantify the effect on the observed result, the Collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam will be available in 2012. An extensive report on the above mentioned verifications and results will be shortly made available to the scientific committees and agencies.” (via Nature newsblog.)

Neutrinos Still Breaking Speed Limits

Particle Collider


New test results are in from OPERA and it seems those darn neutrinos, they just can’t keep their speed down… to within the speed of light, that is!

report released in September by scientists working on the OPERA project (Oscillation Project with Emulsion-tracking Apparatus) at Italy’s Gran Sasso research lab claimed that neutrinos emitted from CERN 500 miles away in Geneva arrived at their detectors 60 nanoseconds earlier than expected, thus traveling faster than light. This caused no small amount of contention in the scientific community and made news headlines worldwide – and rightfully so, as it basically slaps one of the main tenets of modern physics across the face.

Of course the scientists at OPERA were well aware of this, and didn’t make such a proclamation lightly; over two years of repeated research was undergone to make sure that the numbers were accurate… as well as could be determined, at least. And they were more than open to having their tests replicated and the results reviewed by their peers. In all regards their methods were scientific yet skepticism was widespread… even within OPERA’s own ranks.

One of the concerns that arose regarding the discovery was in regards to the length of the neutrino beam itself, emitted from CERN and received by special detector plates at Gran Sasso. Researchers couldn’t say for sure that any neutrinos detected were closer to the beginning of the beam versus the end, a disparity (on a neutrino-sized scale anyway) of 10.5 microseconds… that’s 10.5 millionths of a second! And so in October, OPERA requested that proton pulses be resent – this time lasting only 3 nanoseconds each.

The OPERA Neutrino Detector

The results were the same. The neutrinos arrived at Gran Sasso 60 nanoseconds earlier than anticipated: faster than light.

The test was repeated – by different teams, no less – and so far 20 such events have been recorded. Each time, the same.

Faster. Than light.

What does this mean? Do we start tearing pages out of physics textbooks? Should we draw up plans for those neutrino-powered warp engines? Does Einstein’s theory of relativity become a quaint memento of what we used to believe?

Hardly. Or, at least, not anytime soon.

OPERA’s latest tests have managed to allay one uncertainty regarding the results, but plenty more remain. One in particular is the use of GPS to align the clocks at the beginning and end of the neutrino beam. Since the same clock alignment system was used in all the experiments, it stands that there may be some as-of-yet unknown factor concerning the GPS – especially since it hasn’t been extensively used in the field of high-energy particle physics.

In addition, some scientists would like to see more results using other parts of the neutrino detector array.

Of course, like any good science, replication of results is a key factor for peer acceptance. And thus Fermilab in Batavia, Illinois will attempt to perform the same experiment with its MINOS (Main Injector Neutrino Oscillation Search) facility, using a precision matching OPERA’s.

MINOS hopes to have its independent results as early as next year.

No tearing up any textbooks just yet…


Read more in the news article by Eugenie Samuel Reich. The new result was released on the arXiv preprint server on November 17. (The original September 2011 OPERA team paper can be found here.)

Special Relativity May Answer Faster-than-Light Neutrino Mystery


Oh, yeah. Moving faster than the speed of light has been the hot topic in the news and OPERA has been the key player. In case you didn’t know, the experiment unleashed some particles at CERN, close to Geneva. It wasn’t the production that caused the buzz, it was the revelation they arrived at the Gran Sasso Laboratory in Italy around 60 nanoseconds sooner than they should have. Sooner than the speed of light allows!

Since the announcement, the physics world has been on fire, producing more than 80 papers – each with their own opinion. While some tried to explain the effect, others discredited it. The overpowering concensus was the OPERA team simply must have forgotten one critical element. On October 14, 2011, Ronald van Elburg at the University of Groningen in the Netherlands put forth his own statement – one that provides a persuasive point that he may have found the error in the calculations.

To get a clearer picture, the distance the neutrinos traveled is straightforward. They began in CERN and were measured via global positioning systems. However, the Gran Sasso Laboratory is located beneath the Earth under a kilometre-high mountain. Regardless, the OPERA team took this into account and provided an accurate distance measurement of 730 km to within tolerances of 20 cm. The neutrino flight time is then measured by using clocks at the opposing ends, with the team knowing exactly when the particles left and when they landed.

But were the clocks perfectly synchronized?

Keeping time is again the domain of the GPS satellites which each broadcasting a highly accurate time signal from orbit some 20,000km overhead. But is it possible the team overlooked the amount of time it took for the satellite signals to return to Earth? In his statement, van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

Sure, radio waves travel at the speed of light, so what difference does the satellite position make? The truth is, it doesn’t.. but the time of flight does. Here we have a scenario where one clock is on the ground while the other is orbiting. If they are moving relative to one another, this calculation needs to be included in the findings. The orbiting probes are positioned from West to East in a plane inclined at 55 degrees to the equator… almost directly in line with the neutrino flight path. This means the clock on the GPS is seeing the neutrino source and detector as changing.

“From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter,” says van Elburg.

According to the news source, he means shorter than the distance measured in the reference frame on the ground and the OPERA team overlooks this because it thinks of the clocks as on the ground not in orbit. Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

Is this the final answer for traveling faster than the speed of light? No. It’s just another possible answer to explain a new riddle… and a confirmation of a new revelation.

Original Story Source: Technology Review News Release. For Further Reading: Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?.

Faster Than The Speed Of Light… OPERA Update


A few days ago, the physics world was turned upside down at the announcement of “faster than the speed of light”. The mighty neutrino has struck again by breaking the cosmic speed limit and traveling at a velocity 20 parts per million above light speed. To absolutely verify this occurrence, collaboration is needed from different sources and we’re here to give you the latest update.

“This result comes as a complete surprise,” said OPERA spokesperson, Antonio Ereditato of the University of Bern. “After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement. While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation.”

Since the OPERA measurements go against everything we think we know, it’s more important than ever to verify its findings through independent research.

“When an experiment finds an apparently unbelievable result and can find no artifact of the measurement to account for it, it’s normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it’s good scientific practice,” said CERN Research Director Sergio Bertolucci. “If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements.”

To get the job done, the OPERA Collaboration joined forces with CERN metrology experts and other facilities to establish absolute calibrations. There cannot be any error margin in parameters between the source and detector distances – and the neutrino’s flight time. In this circumstance, the measurements of the initial source of the neutrino beam and OPERA has an uncertainty value of 20 cm over the 730 km. The neutrino flight time has an accuracy of less than 10 nanoseconds, and was confirmed through the use of highly regarded GPS equipment and an atomic clock. Every care was given to ensure precision.

“We have established synchronization between CERN and Gran Sasso that gives us nanosecond accuracy, and we’ve measured the distance between the two sites to 20 centimetres,” said Dario Autiero, the CNRS researcher who will give this afternoon’s seminar. “Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we’re looking forward to comparing them with those from other experiments.”

“The potential impact on science is too large to draw immediate conclusions or attempt physics interpretations. My first reaction is that the neutrino is still surprising us with its mysteries.” said Ereditato. “Today’s seminar is intended to invite scrutiny from the broader particle physics community.”

Original Story Source: CERN Press Release. For Further Reading: Measurement of the neutrino velocity with the OPERA detector in the CNGS beam.

Read our previous article on this paper.

Breaking the Speed of Light

Particle Collider


It’s been a tenet of the standard model of physics for over a century. The speed of light is a unwavering and unbreakable barrier, at least by any form of matter and energy we know of. Nothing in our Universe can travel faster than 299,792 km/s (186,282 miles per second), not even – as the term implies – light itself. It’s the universal constant, the “c” in Einstein’s E = mc2, a cosmic speed limit that can’t be broken.

That is, until now.

An international team of scientists at the Gran Sasso research facility outside of Rome announced today that they have clocked neutrinos traveling faster than the speed of light. The neutrinos, subatomic particles with very little mass, were contained within beams emitted from CERN 730 km (500 miles) away in Switzerland. Over a period of three years, 15,000 neutrino beams were fired from CERN at special detectors located deep underground at Gran Sasso. Where light would have made the trip in 2.4 thousandths of a second, the neutrinos made it there 60 nanoseconds faster – that’s 60 billionths of a second – a tiny difference to us but a huge difference to particle physicists!

The implications of such a discovery are staggering, as it would effectively undermine Einstein’s theory of relativity and force a rewrite of the Standard Model of physics.

The OPERA Neutrino Detector. Credit: LGNS.

“We are shocked,” said project spokesman and University of Bern physicist Antonio Ereditato.

“We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing. We now want colleagues to check them independently.”

Neutrinos are created naturally from the decay of radioactive materials and from reactions that occur inside stars. Neutrinos are constantly zipping through space and can pass through solid material easily with little discernible effect… as you’ve been reading this billions of neutrinos have already passed through you!

The experiment, called OPERA (Oscillation Project with Emulsion-tRacking Apparatus) is located in Italy’s Gran Sasso facility 1,400 meters (4,593 feet) underground and uses a complex array of electronics and photographic plates to detect the particle beams. Its subterranean location helps prevent experiment contamination from other sources of radiation, such as cosmic rays. Over 750 scientists from 22 countries around the world work there.

Ereditato is confident in the results as they have been consistently measured in over 16,000 events over the past two years. Still, other experiments are being planned elsewhere in an attempt to confirm these remarkable findings. If they are confirmed, we may be looking at a literal breakdown of the modern rules of physics as we know them!

“We have high confidence in our results,” said Ereditato. “We have checked and rechecked for anything that could have distorted our measurements but we found nothing. We now want colleagues to check them independently.”

A preprint of the OPERA results will be posted on the physics website

Read more on the Nature article here and on

UPDATE: The OPERA team paper can be found here.