In many parts of science, observations are not allowed to deviate even the tiniest amounts from norms. This rule becomes an inviolable law when the matter in question is the speed of light. Nothing in the world is supposed to travel faster than light. But some neutrinos set off from Geneva and reached a lab beneath the mountains in Italy 60 nanoseconds (billionth of a second) faster than light would have, travelling a distance of 730 km. Researchers at CERN made the dramatic announcement yesterday.
The news turned the world of physics upside down. To be precise, it would turn the world of physics upside down if the measurements prove correct. Apart from many consequences to the currently-tested laws of physics, it could lead to time travel.
But its too soon to get so excited. Neutrinos are among the strangest particles known to us. They whizz through the earth as if travelling through empty space, and change from one flavour to the other in mid flight for no apparent reason. As you read this sentence, a few trillion neutrinos would have zipped through you. They are hard to detect. The neutrinos in question were detected by 150,000 layers of photographic film, interspersed with heavy lead plates. Neutrinos continue to puzzle scientists in new ways every once in a while, but this time they gave scientists a major shock. They jolted a fundamental law.
Einstein had proposed in 1905, while formulating the theory of relativity, a fundamental limitation to the speed of light. This limitation has been tested in a large number of ways since then. The universe would indeed be a stranger place than we assume, if any particle could travel faster than light. In some ways, effect will come before cause. In fact, there is so much at stake in this piece of news that many scientists simply chose to ignore it. Extraordinary claims require extraordinary evidence. In statistics, there are ways of calibrating the strength of evidence.
They call it — somewhat arbitrarily — the sigma scale. Anything that is above 5 sigma is considered strong enough to be worthy of serious investigation. The evidence from the experiment that tested the speed of neutrino was Six Sigma. The chance that the event was a fluke is one in 506,797,346. Even then physicists are muted in their reaction and nobody is celebrating. At least a few think that it was not even worthy of an announcement, before several months or years of discussion.
There is little chance that the result will be true and the neutrinos have actually travelled faster than light. In fact, these particles have been arriving on the earth from several places in the universe, and have never been observed to have arrived before light did. But the current experiment — called OPERA — may not be without its benefits. It could turn out to be an error, or churn out some new physics. Let us wait.