Researchers catch 'faster-than-light' particles

Scientists at Cern and across Europe have reported the apparent discovery of particles travelling faster than the speed of light.

An experiment at Cern in Switzerland appears to have identified neutrinos travelling faster than the speed of light. Photo credit: Cern

In a paper published on Thursday, the researchers described their experiment, which seems to show that a beam of neutrinos travelling through the Earth arrived at a detector some 60 nanoseconds faster than light would take to travel the same distance.

If confirmed, this would require a fundamental rethink of Einsteinian theory, which has underpinned both classical and quantum physics for a century. However, the researchers emphasise that they are not making this claim, rather that they are calling for critical analysis of their experiment and independent replication of the results.

"Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly," the researchers said in the conclusion of the paper.

The experiment has run for three years and made around 16,000 measurements. It times neutrinos — nearly massless particles — generated at Cern near Geneva, as they travel 730 kilometres through the Earth to a 1,300-tonne particle detector called the Oscillation Project with Emulsion-tRacking Apparatus (Opera). The Opera detector is housed in the underground Gran Sasso National Laboratory in Italy.

According to standard physics, the journey should take 2.43 milliseconds. On average, the experiment found, they arrived around 60 nanoseconds earlier than expected, with an uncertainty in the measurement of around 10 nanoseconds. The result, given the number of detected neutrinos and the declared accuracy, is good enough to qualify as a statistically validated discovery.

The potentially great impact of the result motivates the continuation of our studies.

– Cern paper

However, as the scientists point out, the result depends on a number of very precise timing and measurement challenges. An error of 20 metres in the determined distance between the particle generator and the detector would account for the anomaly. In addition, the timing depends on GPS and intricate modelling of the exact moment of neutrino generation, both of which require sophisticated techniques to minimise error.

Other experiments have shown neutrinos travelling at the speed of light, as expected. In particular, a supernova observed exploding 160,000 light years away in 1987 produced a massive pulse of neutrinos that arrived on Earth in exact accordance with standard theory.

If they had been travelling at the speed observed by the Opera experiment, they would have arrived four years ahead of the light from the supernova. The neutrinos generated at Cern are at a different energy to those produced by the exploding star, however, and may behave differently.