Not so fast: Oscillation Project with Emulsion-tRacking Apparatus (OPERA) experiment

The Oscillation Project with Emulsion-tRacking Apparatus (OPERA) experiment is designed to test the phenomenon of neutrino oscillations. The experiment, launched in 2006, studies the rare oscillation of muon neutrinos into tau neutrinos. The first occurrence was observed in 2010. In that experiment, a high-intensity, high-energy beam line of muon neutrinos was produced at CERN, the Geneva-based Organisation Européenne pour la Recherche Nucléaire underground Super Proton Synchrotron (SPS), a circular accelerator, which is six kilometres in circumference and sitting on the Franco-Swiss border and pointed towards Laboratori Nazionali del Gran Sasso (LNGS), also an underground laboratory, 730 kilometres away to the east in L’Aquila in central Italy. Travel time from Geneva to Gran Sasso for a neutrino beam? About three milliseconds.

We say “about” because OPERA, based on the observation of over 15,000 neutrino events measured, using advanced GPS systems and atomic clocks at Gran Sasso.

In September 2011, CERN scientists said it appears that neutrinos travel at a velocity 20 parts per million above the speed of light in vacuum, “nature’s cosmic speed limit” of the speed of light in vacuum, a physical constant value of 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time, or approximately 186,282 miles per second. Expressed another way, the neutrinos appeared to have arrived 60 nanoseconds sooner than they would have if they had been traveling at the speed of light.

Not so fast.

In February and March 2012, OPERA researchers said they were mistaken, blaming the result they reported six months later on a loose fibre optic cable connecting a GPS receiver to an electronic card in a computer. On March 16, 2012, another report announced that an independent experiment in the same laboratory, also using the CERN Neutrinos to Gran Sasso (CNGS) neutrino beam used in 2011,  but this time the Imaging Cosmic And Rare Underground Signals (ICARUS) detector, found no discernible difference between the speed of a neutrino and the speed of light.

In April 2012, OPERA spokesperson Antonio Ereditato and experimental coordinator Dario Autiero resigned. The following month, the Gran Sasso OPERA experiment measured neutrino velocity with a short-pulsed beam, and obtained agreement with the speed of light, showing also that the original OPERA result was mistaken. In July 2012, the OPERA collaboration updated their results. After the instrumental effects mentioned above were taken into account, it was shown that the speed of neutrinos is consistent with the speed of light, confirmed by a new, improved set of measurements in May 2013.

Too bad, in a way. Think about it. If the OPERA results from September 2011 had indeed been replicated it would have junked the one law of physics – E=mc2 (E standing for units of energy; m for units of mass and c2 the speed of light squared) – that even journalists can express, if not comprehend fully; namely Albert Einstein’s 1905 special theory of relativity, which he formulated while working as clerk in the Swiss Patent Office in Bern in 1905. According to special relativity, the speed of light is the maximum speed at which all energy, matter, and information in the universe can travel. Or so it appeared until Sept. 23, 2011.

“Given the potential far-reaching consequences of such a result, independent measurements are needed before the effect can either be refuted or firmly established, the CERN noted in a Sept 23, 2011 press release. “The OPERA measurement is at odds with well-established laws of nature, though science frequently progresses by overthrowing the established paradigms.” Not this time, however.

CERN research director Sergio Bertolucci added, “When an experiment finds an apparently unbelievable result and can find no artefact 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. 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. The potential impact on science is too large to draw immediate conclusions….”

Might change our view of physics? I’ll say. Just for starters, time travel would be perhaps more than just theoretically possible, although there is still the problem known as time-travel paradox. Namely, if someone travels back in time and does something to prevent their existence, then how can time travel be possible? The classic example is the time traveler who kills their grandfather before their own father is conceived. Some scientists, however, suggest that there is not one universe but many – enough so that every possible outcome of any event actually takes place.

In this multiple universe, or multiverse model, someone who went back in time to murder a grandparent can get way with it – moral dimension aside, of course – because in the universe next door the grandparents lives and their progeny continues.

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