By far, one of the most sensational science stories of 2011 has been that of the allegedly faster-than-light particles reported by the subterranean physics laboratory under the Apennine mountains in Italy. When the news broke this past September, it instantly triggered speculation (some of it a bit overheated) that the discovery might upend physics, force a rewrite of Einstein's theory of special relativity, reveal particles traveling backward in time, and undermine concepts of cause and effect.
Physicists around the world were quick to temper such speculations by pointing out that the reported results were almost certainly a mistake. Last week, however, the Italian team announced that a rerun of the experiments carefully designed to eliminate a source of possible error had only confirmed the earlier results.
Yet physicists aren't satisfied. They keep on citing reasons why the faster-than-light particles would conflict with theory. Even colleagues at the same Italian physics facility have declared that the observations must be wrong.
So why aren't scientists accepting the verification of these seemingly impossible faster-than-light particles? Are they just refusing to acknowledge that the concepts on which they built their careers are wrong? Are they rebelling against a "paradigm shift" in their field, as the historian Thomas Kuhn put it in The Structure of Scientific Revolutions? And does their behavior lend credence to the idea often spread by cold fusion enthusiasts, climate change deniers, intelligent design theorists, UFO believers and others that researchers are more interested in protecting mainstream scientific orthodoxy than in finding the truth?
Not at all. In fact, the scrutiny of these supposedly faster-than-light particles is an example of how science is supposed to work and helps to demonstrate why such conspiratorial criticisms are wrong.
Faster than expected
First, a quick recap of exactly what the strange faster-than-light results are. Fourteen hundred meters beneath the Italian mountain for which it is named, the Laboratori Nazionali del Gran Sasso (Gran Sasso National Laboratory) is conducting an experiment called OPERA (Oscillation Project with Emulsion-tracking Apparatus). OPERA detects and measures neutrinos, ethereally aloof particles that have long been understood to shoot unperturbed through matter at the speed of light. OPERA's detectors are set up to catch a beam of neutrinos generated by a powerful accelerator at the CERN laboratory in Geneva. In less than three milliseconds, the neutrinos zip 730 kilometers through the earth's crust, which filters out other, unwanted particles in transit.
Sifting through the data, however, the OPERA team repeatedly saw that the neutrinos appeared to be arriving 60 billionths of a second sooner than expected. They were therefore moving 0.00025 percent faster than light -- a tiny but jarring discrepancy because Einstein's special relativity theory established that no particle could be accelerated to beyond light speed.
It's worth noting that the OPERA experiment is not the first one to find evidence of faster-than-light (or superluminal) neutrinos. Back in 2007, the MINOS neutrino project associated with Fermilab in Illinois published a similarly curious result, but the support for that conclusion was thin and few scientists were persuaded by it. The observations by the OPERA team presented in September were far more robust and compelling (the team claims that the result has a statistical significance of "6 sigma," meaning that the odds of it being a fluke are less than one in half a billion). And the latest, more rigorous repetition of the experiments adds that much more evidence that the effect might be real.
This OPERA ain't over ...
But the OPERA results are still far from constituting proof for superluminal neutrinos, revolutionary as those would be. First, the re-do of the experiment was only a very limited test of the first's findings. One criticism of the first OPERA evidence was that the way of measuring precisely when neutrinos left Geneva and arrived at Gran Sasso was in effect slightly mushy. The improved system in the second round of experiments used sharper, shorter bursts of neutrinos whose timing was more certain.
Yet that change fixes only one source of potential error. Scientists have also called into question, for example, whether relativistic effects in the GPS system that helps to clock the neutrinos might be biasing the measurements, or whether distance between the CERN and OPERA setups might be slightly shorter than believed. (The distance would only have to be off by about 22 meters over the 730-kilometer distance to account for the discrepancy; of course, the distance is supposedly measured to an accuracy within 20 centimeters.) All these possibilities need to be ruled out before the results stand firm.
Another problem is that the OPERA team performed both the initial measurements and the more recent ones. No one questions the credibility or competence of the OPERA researchers, but independent verification is needed because the scientists might unwittingly be introducing the same skew repeatedly into the experiments. Replication of the results by different scientists is the acid test. Indeed, spokespeople for the MINOS facility have said that it may be able to run a preliminary test next year.
For the OPERA results to be strongly vindicated, they need as many independent, rigorous verifications as possible because "extraordinary claims demand extraordinary evidence," in the words of the late astrophysicist and skeptic Carl Sagan. Frustrated proponents of unorthodox science sometimes complain that Sagan's standard begs the questions of what constitutes "extraordinary evidence," but no matter what, more than one repetition is necessary for something this amazing.
Of course, those same disgruntled and suspicious critics might also claim that all these rationales for more proof are beside the point -- that the ugly truth is the physicists don't want to see the edifice of Einstein's physics toppled. That argument, however, is built on a misunderstanding of why scientists hold the views that they do.
The inconvenient facts
Faster-than-light particles don't seem unlikely just because they are at odds with theories that physicists are loath to give up. Rather, they are at odds with huge amounts of observational and experimental data that gave rise to those theories.
For example, one of the stunning vindications of modern astrophysics involved the supernova 1987A: shortly before that star exploded in 1987, it released a burst of neutrinos precisely when models of stellar collapse predicted that it should. But if neutrinos actually move faster than light by the margin OPERA suggests, those neutrinos should have arrived at Earth four years earlier than they did.
Similarly, the theoretical refutation of the OPERA results that Nobel laureate Sheldon L. Glashow and Andrew G. Cohen have offered is that any superluminal neutrinos from CERN should have shed almost all their energy by the time they reached Gran Sasso because of a phenomenon called bremsstrahlung radiation. Bremsstrahlung is observed whenever charged particles interact with matter.
Perhaps some extenuating complexities can explain these discrepancies: maybe neutrinos from CERN and those from stars move at different velocities, and maybe superfast neutrinos may uniquely avoid radiating away their energy. But for now, the more parsimonious explanation is that the OPERA results are wrong.
What's almost absurd, however, is to think that scientists would steer away from iconoclastic discoveries to protect their professional standing. But the career of any scientist who has the evidence to knock down pillars of his or her field isn't ruined -- it's made.
The physicists who first prove the existence of faster-than-light particles are instantly in the history books. That credential looks pretty good to tenure committees and granting agencies. The same would be true for any climate scientist who could truly, conclusively prove that worries about climate change from industrial greenhouse gases were groundless, or for any biologist who could knock off evolution as the best explanation for living things' traits. They wouldn't be blackballed by their professions: they would be among the most famous scientists alive and able to name their own appointments.
Moreover, revolutions in science aren't just good for the leaders of the revolution. The demonstrated existence of faster-than-light particles would mean that other new physics remains to be discovered, and lots of new work needs to be done to fit the older observations into the new paradigms. Those opportunities would be welcomed by legions of physicists looking to make their mark. Indeed, the OPERA results have already inspired a number of scientific papers.
Einstein's theory of special relativity sits on a pedestal of honor, not on an altar. Plenty of physicists would be glad to knock it off and put something else in its place. But it may take something more substantial than OPERA's superluminal neutrinos to bring it down.
Image: Particle tracks. (Credit: CERN)