[The OPERA neutrino detector on the left is leagues above the cold fusion cell on the right.]
Lots of people in the news, in university hallways, and even in cartoon form are urging caution against putting too much confidence in the measurement of neutrinos that travel faster than light. Many of them have suggested that the whole thing looks a lot like the ill-fated cold fusion announcement of 1989.
It's certainly true that the superfast neutrino experiment is one of the most surprising and unexpected announcements in the modern history of physics. And as Carl Sagan said, "Extraordinary claims require extraordinary evidence." While results from a single experiment probably fall a bit short of the extraordinary evidence level, I think it's misguided at the very least to cite cold fusion's sad story as a reason to be skeptical about this experiment.
Cold fusion and the recent neutrino experiments are superficially similar in that they each seemed to take catch the physics community off guard. Beyond that, there's not much the two have in common.
At least initially, cold fusion looked like a stunning technological development that had the potential to solve all the world's energy problems. The fast neutrino results, if true, are unlikely to have any practical applications for the foreseeable future, but they could make physicists rewrite some of the best established physics theories we've ever known. (It wasn't until people started finding flaws in cold fusion experiments that proponents began claiming to have discovered new physics.)
That is, from a fundamental physics point of view the fast neutrino results are actually much more extraordinary than the initial cold fusion claims. That suggests that the OPERA collaboration has an even higher bar to clear that the cold fusion "discoverers" faced.
The more important difference between the two cases, however, is the response of the scientific community once the researchers began discussing their experiments publicly. Following their press conference in 1989, it was clear to the vast majority of physicists just how shoddy an experiment Pons and Fleischmann had put together. There were countless suggestions for ways the experiment should have been done, as well as endless criticisms pointing out the many things they could have tried in order to double check their results. It was also clear that they lacked the expertise in the statistical analysis necessary to evaluate their own results.
The reaction at the seminar in CERN where the fast neutrino results were presented couldn't have been more different from the cold fusion fiasco. The OPERA collaboration appears to consist of a group of very sharp physicists who were eager to call in experts to handle particularly difficult portions of the experiment. Over the course of years, they repeatedly checked every source of error they could think of. They performed a double blind analysis that ensured that any biases they had would not affect the experimental statistics. No one at the seminar could come up with a single design flaw that the OPERA collaboration had yet to consider.
Of all the suggestions physicist at the seminar at CERN offered, the only one the collaboration hadn't already tried was building a duplicate set of detectors right next to the neutrino source to confirm that the distant set didn't suffer from some systematic design error. (I hope they will try it, but by the time build extra detectors other experiments may already have the data to back up or dismiss the fast neutrino results.)
It's true that most physicists remain skeptical of the notion that neutrinos move faster than light, but unlike cold fusion, which was built on a shoddy and rotten experimental foundation, it appears that the neutrino experimental design is as solid as the rocks beneath the Gran Sasso mountain.
It's not yet time to rewrite the physics texts, but there is clearly something very strange going on here. Either an extremely subtle experimental error is at work, or physics has suddenly gotten very interesting. It looks like we'll know for sure in a year or two. Personally, I'm not going to put all my chips on superfast neutrinos. Still, I sure hope we can one day look back on September 23, 2011 and think of it as the moment a new chapter in physics began. Thankfully, no matter what the outcome, it looks like it's not going to be a rerun of the tragic comedy that was cold fusion.