This week the scientists at CERN, the European Organization of Nuclear Research, announced that they had found neutrinos traveling faster than the speed of light. Since this flies in the face of much of what we know about Einstein’s theory of special relativity, it begs a number of questions. First, what are neutrinos? Second, what does this mean for physics and our scientific theories, and third and perhaps most importantly, what does this say about science and the way that it deals with our constantly evolving understanding of the universe?
First things first. Neutrinos are tiny, almost massless subatomic particles similar to electrons but without an electrical charge. Their existence was first proposed in 1930 by Wolfgang Pauli to explain where some of the energy and momentum went when protons decayed. Since his hypothetical particles didn’t have an electrical charge he called them neutrons, meaning “neutral ones”. A problem ensued in 1932 when James Chadwickdiscovered a much more massive neutral particle in the nuclei of atoms and called them neutrons.
In 1934 the Italian physicist Enrico Fermi solved the problem by dubbing Pauli’s particles neutrinos, Italian for “little neutral ones”. It wasn’t until 1956 that neutrinos were actually detected by a team led by Clyde Cowan and Frederick Reines, for which they won a Nobel prize.
Neutrinos, because they lack an electrical charge and have very small mass, don’t interact much with other particles. That means they can go zipping through space or even entire planets without slowing down. They are produced in nuclear reactions like those in the sun or in nuclear reactors. To give some idea of how common they are look at the tip of your little finger. That’s approximately a cubic centimeter. Every second of every minute of every day approximately 65 billion (6.5 x 1010) neutrinos from our sun pass through that cubic centimeter on the tip of your finger and every other cubic centimeter on Earth.
The scientists at CERN weren’t trying to see if neutrinos could go faster than light. They were looking at other aspects of their behavior, and to do that they produced a beam of neutrinos at the Super Proton Synchrotron near Geneva Switzerland and fired them at a set of detectors in Gran Sasso, Itally, 730 kilometers, a little over 450 miles, away. The reason the detectors had to be so far away is that the synchrotron produces lots of different types of particles, not just neutrinos. The idea is that nothing other than a neutrino could make it through that much rock and dirt without being blocked, deflected or annihilated.
It worked. The detectors in Gran Sasso picked up the Geneva neutrinos just as predicted, well almost as predicted. They actually got there a bit early. Specifically, they made the trip 60 nanoseconds faster than they should have if they were traveling at the speed of light. While 60 billionths of a second might not sound that significant, in particle physics it is very significant. According to Einstein’s theory of special relativity, nothing should be able to go faster than light, not even a little bit, not even 60 nanoseconds.
If this result is correct it throws the theory of special relativity and the 106 years of physics based upon it into question. It throws a wrench into our entire understanding of causality, the idea that a cause is followed by an effect, not the other way around. Subir Sakar, head of particle theory at Oxford University put it this way in the Guardian, “Cause cannot come after effect and that is absolutely fundamental to our construction of the physical universe. If we do not have causality, we are buggered.”
So, what do we do?
Exactly what scientists all over the world are already doing. First they check to see if there was some sort of problem with their instruments. There wasn’t. Next they check their calculations. Ordinarily physicists consider something statistically significant if it meets what’s called the 5-sigma threshold. That’s statistician short-hand for five standard deviations, or in other words one chance in 1,744,278 that it’s a fluke. In this case, with so much at stake, they actually found that their results were the equivalent of 6-sigma, one chance in 506,797,346 that something was wrong.
Next they try to duplicate their results and ask other scientists at labs all over the world to do the same. Other labs are going to be seeing if they can get the same results, if they can detect these faster-than-light neutrinos. Coincidently, one of the those labs is the Fermi National Laboratory in this country, named after the scientists who gave neutrinos their name.
If those other scientists fail to duplicate the CERN results then Einstein’s theory is safe for now. At this point that’s where the smart money seems to be. On the other hand, if they can duplicate the results and do find that neutrinos are capable of breaking the universe’s speed limit then we have some major rethinking to do. In either case though, it’s important to remember that scientists are doing exactly what they are supposed to do, remaining skeptical, neither accepting nor dismissing evidence that contradicts current theories, and double checking their math. That’s the way that science works.