Loose cable may explain speed of light mystery

Researchers at Cern have discovered that a loose cable may have been the real reason for an apparent measurement of neutrinos exceeding the speed of light. However, another possible fault could mean the recorded speed was actually understated.

As you can’t have failed to miss, staff on the Opera (Oscillation Project with Emulsion-Racking Apparatus) experiment were originally working on measurements of how neutrinos (tiny particles) changed while in transit. During their study, it appeared that the neutrinos were arriving at their destination around 60 billionths of a second faster than light would travel.

While open-minded scientists aren’t ruling out the possibility that this is indeed the case, and thus physics needs something of a rethink, most of the initial attention was on trying to figure out what flaws could have produced an incorrect reading.

One early offering was that the researchers had used clocks linked to GPS satellites to measure the start and finish time, but had failed to take account of the fact that the earth rotated during the transit and thus the relative positions of the satellite and measurement locations changed.

The Opera team has also been looking for possible shortcomings before carrying out a repeat experiment, likely some time this year. While they’ve found two possible distortions, they would have opposing effect.

Problem one is a connection fault in a fiber optic cable running between the GPS receiver and the main computer used in the experiment. If that fault did have an effect, it would have meant the recorded speed was overstated. Staff have already tried tightening the cable and then retiming data transfer times. The difference this makes appears to neatly fit the 60 nanosecond disparity in the original experiment.

Problem two is a possible fault in the oscillator that was used in the experiment to keep time in the gaps between the GPS equipment synchronizing. Intriguingly, if that fault had an effect, it would have been to falsely increase the recorded time of the journey. That would, in turn, have made the calculated speed lower than it was in reality.