After announcing on September 23 last year that neutrinos travelled 60 nanoseconds faster than light, the OPERA (Oscillation project with Emulsion-tRacking Apparatus) team has recently identified certain flaws. These pertain to possible “effects” in the experiment that might have led to an incorrect measurement in the arrival time of neutrinos at the Gran Sasso National Laboratory in Italy, 730 km from CERN where the neutrinos were generated. The two possible errors, pertaining to the novel use of the global positioning system (GPS) in particle physics to synchronise the atomic clocks at CERN and Gran Sasso, could have led to an overestimation or underestimation of the neutrino speed. Of the two errors, a faulty connection between the GPS signal and the OPERA master clock is seen as the main suspect for causing a mistake in calculating the neutrinos’ arrival time. That the fault has been traced to the GPS should not come as a surprise as many scientists had as early as November suspected so. But the last word has not been said yet. The scientists would be conducting new velocity measurements in May using “short-pulsed beams,” reports Science.
This is not the first time that the OPERA team has had to repeat the experiment following its announcement. Though the team conducted the experiment for three years, measured the speed of more than 15,000 neutrinos and checked the accuracy of the data for about six months before announcing the results, it had to rerun the experiment soon after. This was to eliminate some uncertainty arising from proton pulse duration. Though the pulse duration used for generating neutrinos was reduced from 10.5 microseconds to 3 nanoseconds, the neutrinos still arrived 60 nanoseconds earlier than light. The focus then shifted to a possible error in the measurement using the GPS system. Regardless of whether a rerun of the experiment later this year proves or disproves the initial result, the entire exercise has gone a long way in showcasing the way science operates. For instance, this work has shown what is so basic to science — even the most fundamental laws of science will often be challenged by scientists using the most sophisticated instruments and experiments. While the results challenge Einstein’s theory of Special Relativity, the team has never claimed to have proved that neutrinos travel faster than light, and that the laws of physics have been upended. In fact the team wants further “scrutiny and independent tests” before its measurements could be “confirmed or refuted.” After all, independent verification and replication of the results are central to science.