But it usually isn’t.
This past week, scientists at CERN announced some very interesting results suggesting that neutrinos may be able to travel faster than the speed of light. This is understandably big news, so you almost certainly didn’t read it here first. I just have a few additional observations.
First, the initial paper is available on arXiv.org here. I am no particle physicist, but the basic story is not very complicated, and with my usual educational bent, I think this makes for an interesting and useful exercise even for young students… because it essentially boils down to distance = rate * time. Scientists measured the time required for neutrinos to travel 731.278 km (about 454 miles) from a particle accelerator in Switzerland to a detector in Italy. For those here in the U.S., imagine particles traveling underground between Baltimore, Maryland, and Martha’s Vineyard in Massachusetts– or for those reading back home, between Kansas City and Dallas, Texas.
Traveling at the speed of light (exactly 299,792,458 meters per second), the trip should take about 0.0024392808 second. However, detection equipment on the receiving end observed the arrival of neutrinos about 60 nanoseconds earlier than this, suggesting that the particles were traveling faster than light. That’s not much less time… but it’s a lot more speed. It means that neutrinos would beat light to the finish line by just about 60 feet (one light-nanosecond is approximately one foot), but in doing so they exceed the speed of light by more than 16,000 miles per hour, about the speed of the Space Shuttle or the International Space Station in orbit around the Earth. (This is a small fractional increase in speed, though, relative to the speed of light: just about 25 parts per million.)
As usual, I recommend reading the original source. Something that the “popular” press frequently seems to miss in this story is that it’s not completely new. Neutrinos have behaved in funky ways before; the paper mentions and references similar observations back in 2007, although with admittedly less precise measurements.
Finally, it is the improved measurement technique and precision that are under much of the scrutiny in this most recent experiment. As described in the paper, the scientists are not able to actually measure the times of departure and arrival of any single neutrino. Instead, they collect timing information for multiple particles over a larger interval, and use statistical techniques to “shift” entire distributions of departure/arrival times until they “line up.” Even for the non-physicist, there is some interesting mathematics involved.
As I said, I’m not a particle physicist. But even watching from the sidelines, I find it exciting, and not a little inspiring, to watch science in action like this. There is an enormous amount of attention, review, and criticism of these experiments, and that scrutiny is what science is all about. The basic practice of science may not be changing, but I think the speed of science may very well be undergoing a radical increase even as we speak. Similar to the polymath projects started by Timothy Gowers, today’s technologically small world allows very large numbers of eyes and brains working on a problem, which can have the doubly-beneficial effect of “parallelizing” more exploratory investigation while at the same time more quickly recognizing and abandoning dead ends.
Do I think the result will be fundamental changes to our current understanding of physics? My uneducated guess is that I doubt it. It could turn out to be as simple as some unexpected systematic measurement error. Or maybe there really is a new phenomenon here, but one that merely requires refinement, not complete rejection, of currently prevailing theories.
But I could be wrong.