Supernova 1987a set a limit on the speed neutrinos can travel too...
I was in Spain when the neutrino story broke. I returned to see a comment on my Facebook wall from a friend who studied physics with me saying something to the effect of ‘Neutrinos can travel faster than light? Everything I have learned is wrong!’. A quick google revealed dozens of news articles about the amazing discovery, and several blog posts disputing it. A few weeks on and the excitement has somewhat died down – although a seminar held at Queen Mary, University of London on neutrino physics last night was still very well attended.
The general consensus amongst most physicists I have spoken to seems to be that this result is likely to be a systematic error. There was another event which compared the speed of neutrinos to the speed of light: and a much more dramatic one. When massive stars collapse at the end of their lives, in a supernova, they lose vast amounts of energy through flinging out huge numbers of neutrinos. These are released shortly before all the light which is normally the indicator of a supernova – a sudden brightening of the star. In 1987, neutrino detectors spotted a burst of neutrinos, much higher than the normal background, indicating that they had spotted something interesting. Sure enough, about 3 hours afterwards the supernova was discovered by astronomers in Chile, when they spotted the star brightening.
If neutrinos really do travel faster than light, we would expect to be able to compare the time that the neutrinos took to get to us from this supernova to the time the light took. We would expect the neutrinos to get here much earlier, even if they are only a tiny bit faster, as the supernova was very far away. If we use the speed that the OPERA experiment measured for neutrinos, we discover that the neutrinos should have appeared approximately 4 years before the light was seen. This is subject to large errors (plus or minus a year), but it still isn’t anywhere near to the three hours we actually saw. Some of the detectors were running four years earlier, but they didn’t see anything of note.
So what is really interesting about this result is that it is totally at odds with another. Both experiments can’t be totally right – there must be something we don’t understand, and it could be about neutrinos (maybe different ways of making neutrinos give them different speeds?). The supernova is mentioned in the paper itself, and the paper concludes with a health warning that since faster than light neutrinos would be such an important result they are wary, and are investigating for further, unknown systematic errors. But you wouldn’t know this from the Reuters article. In fact Supernova 1987a wasn’t even mentioned in reports until the next day, when scientists started pointing it out.
And here lies the problem. If neutrinos do travel faster than the speed of light, that is an incredible discovery, deserving of the excitement the initial announcement generated. But Reuters published the initial article before the paper was even available, and without mention of any evidence pointing in the opposite direction.
I’m not actually saying that they are at fault – it is a journalist’s job to get in first with exciting stories, and lots of reputable papers have pointed out the problems. What I feel uncomfortable with here is the worrying trend in science – especially in physics – of going to the press too early. I’ve lost count of the number of times that scientists have ‘discovered the Higgs‘ only to go very quiet when it turns out that this was just a random fluctuation in the background noise, not the famous particle at all (a google search of ‘Higgs discovery’ illustrates this pretty well). The number of times I’ve had to explain to an excited non-physicist that this will probably go away is a bit depressing – although xkcd has given me some ideas for what to do with the next big news.
It’s hard not to get disillusioned. When the next claim of some miraculous discovery comes out, I’m going to be skeptical, not excited. I can’t help but wonder if this is damaging public faith in science. It doesn’t seem to be yet – people still can’t stop talking about the neutrino results, even if it is a systematic error – but surely it must eventually have an effect. Physics coverage has got a lot better over the past few years, and we need to keep the excitement bubbling, not to get to a point where everyone ignores the real discoveries because they are so sick of finding out that they aren’t real after all.
Just after the announcement, I was talking with a colleague who is very experienced in this sort of thing (he’s a professor and has had a long, successful career in research). He was pondering on whether he would have released the data or waited for feedback from peers. That seems to be the answer here – urging caution with blogging and going to the press, to make sure that physics doesn’t become the subject that cried wolf…
Bryony Frost is studying for an MSc in Science Communication at Imperial College London, and is one of the editors of Refractive Index
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