(This post was written on a neutrino-computer last week, but it has taken this long for the light to catch up so you can read it…)
First, the science: neutrinos are tiny, chargeless (hence the name) particles that have an incredibly miniscule mass — so miniscule that for a long while, neutrinos were speculated to be massless. Because they have no charge and so little mass, neutrinos interact with normal matter (like atoms) only very rarely. For instance, neutrinos are made by the Sun and pass straight through the entire Earth as if it was not even there. At nighttime, to use an image commonly invoked to illustrate the point, at every instant, neutrinos are streaming from the Sun, traveling all the way through the Earth, and passing through your body by the trillions as if it was a ghost. They similarly pass right through detectors built to find them. Only rarely do they happen to impact with normal matter, and these tiny disturbances are what are looked for in neutrino experiments.
Scientists in Europe have been testing neutrinos by producing them in collisions at a CERN collider in Geneva, which are then transmitted through the Earth towards a detector in northern Italy, called OPERA. The speed at which the neutrinos are traveling is determined by noting the time it takes for the neutrinos produced in Geneva to be detected in Italy. The distance used for the calculations is determined by using GPS measurements and triangulating the location of the collider and the detector.
The results of the measurements are what have caught the scientists’ attention — according to their measurements, the neutrinos appear to have reached the detectors about 60 nanoseconds faster then they would have if they were traveling at the speed of light. Thus it appears that the neutrinos are moving faster than light — but if this were so, it would undermine general relativity, the central theory of modern physics, which holds that the speed of light is a constant, to which everything else in the universe is relative.
A few observations:
1. The experimental results still require confirmation. The scientists who have reported the results have explicitly stated that they are releasing their data not to make any claims, but to request confirmation and analysis. It is still not at all unlikely that these results are the product of some sort of systematic error in the experiment — in the measurement of distances, in neutrino detection, in the time of the neutrino production. The scientists have operated exactly as scientists ought to — measuring data and opening the results up for critique and replication. In the meantime, there’s no need to jump to conclusions.
2. If the results are confirmed, it will be revolutionary. Relativity, with its “light-speed speed limit” underlies all of modern physics. Overturning this fundamental principle will have repercussions throughout science. It’s not entirely unexpected that fundamental changes are awaiting science — after all, physicists still can’t reconcile quantum theory and relativity — but to find the change here would be dramatic.
3. If the results are confirmed, it will not be revolutionary. Objects will still fall if you drop them, the Earth will still orbit the Sun, and Mr. Fusion will not start appearing on the shelves at Wal-mart anytime soon. Even in theoretical physics, it’s not as if “relativity” will be simply abandoned. The very GPS system the scientists used in this experiment has built-in corrections for relativistic effects. If it didn’t, GPS systems wouldn’t work. In other words, we already know relativity is real and have to deal with it practically. So it’s not as if the principle of relativity will vanish entirely — it will simple have to be understood in a wider context.
What remains is to wait and see. Physicists are skeptical, but interested. Either result — experimental error or confirmation — will be an important contribution to science’s understanding of the world.