Faster-than-light neutrino result may have been due to bad connection
news.sciencemag.org
news.sciencemag.org
Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It's a little bit off because he had the incorrect value for the viscosity of air. It's interesting to look at the history of measurements of the charge of an electron, after Millikan. If you plot them as a function of time, you find that one is a little bit bigger than Millikan's, and the next one's a little bit bigger than that, and the next one's a little bit bigger than that, until finally they settle down to a number which is higher.
Why didn't they discover the new number was higher right away? It's a thing that scientists are ashamed of - this history - because it's apparent that people did things like this: When they got a number that was too high above Millikan's, they thought something must be wrong - and they would look for and find a reason why something might be wrong. When they got a number close to Millikan's value they didn't look so hard. And so they eliminated the numbers that were too far off, and did other things like that...
And don't forget there is a check and balance in the form of meta-studies and statistics that are sometimes uncanny can exposing bias and flaws.
Finally - this highlights the dual nature of 'experimental' vs 'theoretical' physics, and they work so well in tandem.
In a nutshell, we know that science more or less progresses from one theory to another after the existing theory has been falsified (Popper), but this transition does not happen overnight, even after a falsifying result has been put forth. That is because science is really structured with a "hard core" hypothesis (say, in physics, that nothing moves faster than c), and various "auxiliary hypotheses" that bear the brunt of criticism before the core belief is attacked (say those that posit the integrity of the measurement instrument, for example). And that is all that is going on here. There are many, many theories that are going to be dismantled before physics transitions to something post-relativity. It's just the way the assumptions are structured.
While this may seem trivial, we see this playing out in the battle of classical against behavioral economics. Are the results of experimental psychology admissible in the criticism of certain economic models? Models don't claim to be perfect, after all...
1. http://en.wikipedia.org/wiki/Imre_Lakatos#Research_programme...
As the OPERA result showed, it has the problem that if you don't understand everything in your experiment perfectly (which is difficult to do in a very large, complicated experiment) you run the risk of embarrassing yourself by making some obvious-in-retrospect mistake and publishing an obviously absurd result. But in the long run it's not so bad a price to pay to avoid the sort of confirmation bias that Feynman was talking about.
[1] http://people.psych.cornell.edu/~jec7/pcd%20pubs/simmonsetal...
How does that help when the prediction matches the measurement but the experiment is flawed ?
1. Hubble was actually measuring the local motion of nearby galaxies, the so called Local Group. These galaxies are too close for Hubble expansion to matter, they're just gravitating.
2. The actual value for the Hubble constant he measured was way off, by something like 10x.
1. Hubble's draftsman made an error while preparing his famous diagram. From Figure 1 of his paper (http://adsabs.harvard.edu/abs/1931ApJ....74...43H), you'll notice that the vertical axis is in "km" rather than "km/sec."
2. Measurements of the Hubble Constant over time: http://www.pnas.org/content/101/1/8/F2.large.jpg For some reason it's not plotted logarithmically so it's hard to see the convergence towards ~70 km/s/Mpc in the last twenty years.
When Millikan's experiment was new it was new; people hadn't done it before, there was slop to work out, and the theory was miles behind. These things take time to converge on a consensus. Sometimes a long time. Also, money.
How would such dynamics pan out for experiments that aren't amenable to the sort of polite gradual adjustment as Millikan's was?
The real lesson is that this sort of thing (fudging numbers, lack of scientific integrity) is quite prevalent but most of the time goes unnoticed because there isn't something as dramatic as with the Millikan experiment to show it plainly.
(http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach...)
> The cables house 36 strands of superconducting wire, each strand being exactly 0.825 mm in diameter. Each strand houses 6300 superconducting filaments of Niobium-titanium (NbTi). Each filament is about 0.006 mm thick, i.e. 10 times thinner than a normal human hair.
> tolerances are only a few micrometers.
> Total superconducting cable required 1200 tonnes which translates to around 7600 km of cable (the cable is made up of strands which is made of filaments, total length of filaments is astronomical - 5 times to the sun and back with enough left over for a few trips to the moon).
Compared to Wolfe-Simon et al (the group that claims to have found arsenic in the DNA of certain bacteria) they show exactly how science should be done.
I think they could gain far more with a mea culpa than with living in denial, which is what they seem to be doing.
Scientists are humans too. I can understand why they prefer to live in denial, even if that doesn't make them better scientists. Or humans.
Update: a spokesperson for CERN has confirmed "a problem with the GPS system." http://www.cbc.ca/news/technology/story/2012/02/22/technolog...
>At the AAAS meeting's discussion, CERN's director of research, Sergio Bertolucci, placed his bet on what the results would be: "I have difficulty to believe it, because nothing in Italy arrives ahead of time."
jonhendry, you're a prophet :)
"The OPERA Collaboration, by continuing its campaign of verifications on the neutrino velocity measurement, has identified two issues that could significantly affect the reported result. The first one is linked to the oscillator used to produce the events time-stamps in between the GPS synchronizations. The second point is related to the connection of the optical fiber bringing the external GPS signal to the OPERA master clock.
These two issues can modify the neutrino time of flight in opposite directions."
http://blogs.nature.com/news/2012/02/faster-than-light-neutr...
"x > c" is a binary test, BTW.
As an example, suppose that we were able to go faster than C in the reference frame of the fixed distant stars, but not in other reference frames. There are reference frames where you can go backwards in time, but none in which you can violate causality.
(That said, General Relativity allows for causality violations. However setting them up is well beyond any engineering ability our species is likely to develop...)
Of course I state this as a theoretical point only - there is absolutely no reason to suspect that any such thing is possible.
Part of the point of experimentation is to find holes in our existing models, so it is reasonable for scientists to look for faster than C without violation of causality.
PS: Meant to upvote, but hit the wrong button. Sorry.
But I see that several other comments at that level were also downvoted.
Science is not a process of walking from one stepping stone of absolute, solid truth to another stepping stone of truth. Science is messy. Because the world is messy. Science is the process of observing the Universe as best we can given our limits and attempting to verify various models and conjectures about the way the Universe works. But along the way there are many potentials for pitfalls. Every experiment has a degree of error due to factors unrelated to what the experiment is trying to measure.
Published scientific papers are not like chapters in a text-book, they are merely the results of experiments. Sometimes it's possible to have experiments which seem to support one result or another but turn out to have some flaw or merely involve factors which we cannot explain yet. For example, we still don't know what "dark matter" actually is even though we have a pretty good idea that it does exist and some rough estimate of some of its properties. And for decades we did not know the origin of gamma ray bursts. It's the rare experiment that is definitive enough to provide unambiguous support or refutation for a specific theory, most experiments are somewhere in the middle, somewhat muddled, imperfect, and generally only gain strength once independently repeated and producing the same result.
Similarly, they didn't know what their results would be until after they ran the experiment. At that point, they can either: share the results, or hide the results. Hiding the results is the absolute worst thing that any scientist can do. The only time the option not to share the results would be acceptable is when they can be discredited or discounted (and sometimes they should still be shared). Since they couldn't discredit their results (they tried), they took the only responsible option remaining.
Indeed, they didn't just publish the results, they asked others to look for the bug. Like others have said, this is the best possible outcome.
What's wrong with that?
It takes courage to stand in front of every camera on earth and claim to have measured something impossible, no matter how cautious you are, and no matter how gracious everyone else is. It takes courage to knowingly and deliberately turn yourself into the butt of jokes in foreign languages whose names you don't even know, all on the very slim chance that this thing you can't explain is something breathtakingly awesome, Isaac Newton-awesome, Albert Einstein's 1905-awesome. It was bound to be embarrassing in the end, and lo and behold it is shaping up to be exactly as embarrassing as every one of my fellow experimentalists knew it would be, and I can't decide whether to laugh, cry, or salute, because when you've spent months or years of your life in utter despair, trying to get your experiment to produce something halfway believable, or redoing six months of work because a broken fridge probably contaminated the first batch, or trembling as you cross-check the simulation code the week before your thesis is due, you've learned how it feels: Awful.
I'll go with "salute": Let's all raise a glass to these folks and be grateful that they are on the road to finding their problem, rather than being haunted by uncertainty forever. May their next result be twice as exciting and only half as wrong!
This is more a question of engineering. Doing modern physics experiments require extremely complicated machines with tolerances so fine that the tiniest amount of noise in the results can throw off the accuracy of the measurements.
The experimenters were not some quacks making spurious claims. They very, very, very carefully checked and rechecked their results before deciding to talk to the outside scientific community and asking for help.
Given the complexity of these machines, it doesn't surprise me at all that a single cable might be the source of the errors. If you write code, you find many times throughout your career you get errant results. In the process of tracking down the cause, you may spend hours, days, or longer going line by line and missing the problem. In the end, it may turn out to be a mis-named variable or the wrong kind of comparator (== vs === in js). Simple things that are easy to miss.
There was a story recently about a commonly used algorithm that dates back decades that had a bug in it. When the algorithm was originally developed, it was never thought that it would still be in use 30 years later and disregarded the size of data sets available. When the algo was used on a very large, modern set of data an integer would flip and go negative. The point is, its easy to miss things in very complicated systems and very hard to make sure there are little or no bugs at all. I don't remember what type of algo it was, but it was an interesting read.
Talk about scary...