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.)

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.