Finally An OPERA Plot that Makes Some Sense

Ok, thanks to a commenter (Titus) to this morning’s post, I learned of information available in the German language press that is vastly superior to anything I had seen previously— much better than today’s New York Times article, because it contains detailed and extensive quotations from a participating scientist on OPERA. [There is nothing like nearly-first-hand information.] Here is the link:

http://www.faz.net/aktuell/wissen/physik-chemie/interview-ueber-die-moeglichen-fehlerquellen-messfehler-koennten-ueberlichtgeschwindigkeit-erklaeren-11660876.html

You can try Google translate and it isn’t awful, but it does contain some important mistakes; my German is good enough to read some more of it but not good enough to do a proper translation for you.  I encourage someone fluent to help us out with a proper translation.    Someone has done so — see the comments.  [Thanks to the translator!]  You’ll see, when you read it, that there are some minor discrepancies between I wrote, based on imperfect translation, and what the OPERA physicist is quoted as saying in the better translation, which is obviously what you should go with. 

Facts that one can glean from this article bring me to the following conclusions:

As I suspected all along (and contrary to the original press reports), the OPERA experimenters do not claim to have found the cause of the 60 nanosecond shift in the timing of the neutrinos.  They only have suspect causes.  This is not the same thing.  The mystery is not over yet (though it has probably entered its final chapter.)

The situation is complex, because they know of two problems, one (with an oscillator) decreasing the shift and one (with a fiber) increasing it.  We now know (thanks to the German article) that both of these effects are tens of nanoseconds in size, and one (the one involving the famous faulty fiber) could be as large as 100 nanoseconds.  That means that in the language of yesterday afternoon’s post, whose Figure is reproduced here, the situation with OPERA is perhaps describable as case (d), perhaps as case (e).  In short, it is now confirmed that there currently is no known discrepancy — not even a weak one — with Einstein’s theory of relativity.

(a) What OPERA said originally. (b) What the original press articles on February 22nd claimed OPERA was now saying. (c),(d),(e) Three possible interpretations of OPERA's statement. In each case, a bar whose center lies at the most likely result of the measurement, and whose width indicates the degree of uncertainty, is shown. If we take OPERA's statement at face value, we still don't know if it is inconsistent with zero but less certain than before, consistent with zero, or simply unknown (in which case the previous measurement must be discarded.) We now know what was implied was something like (d) or (e).

Despite all of the jokes and snide remarks, it sounds as though the problem with the fiber was quite difficult to find, and was a really nasty one: it depended very sensitively on exactly how the fiber was screwed in, which means a defective fiber or a defective connection, I guess. We’re not just talking about an ordinary loose wire. This is not inconsistent with what my experimental colleagues tell me about looking for sources of electronics problems; in particular, note the comment (highlighted in red) from this morning’s post.

The experimenters believe that over the coming weeks they can, with some considerable effort, nail down to some degree how big these two effects were. If they succeed, perhaps they will be able to bring case (d)/(e), which is what we are currently dealing with, back closer to case (a) or (b), or at least case (c). We’ll see what they say then.  But no one, not even OPERA, will be very confident in the result at that point.

OPERA cannot be absolutely sure that they have found the cause of the timing shift in the neutrinos — and that there are no other major problems — until they rerun the experiment, to see whether fixing the two problems changes last year’s result by just about 60 nanoseconds. Apparently this is not something they can tell post facto just by looking at the way the fiber and the oscillator behave now; it is still not entirely clear why, but surely the devil here is in the details, and we won’t get those from press articles.

Apparently there are people within OPERA who argued back in September that the result was not ready for public presentation.  They are vindicated now.

Several experiments (OPERA, ICARUS, BOREXINO, and apparently another one I didn’t know about, LVD) will all attempt the neutrino speed measurement, independently but simultaneously, this spring.   (The neutrino beam is very wide when it arrives at the Gran Sasso laboratory, and all of the experiments sit inside it.)  Hopefully OPERA will have eliminated its problems, and the other three experiments will not make any mistakes, and all four experiments will get the same answer.  Of course these are very hard measurements, so they might not get the same answer.  We’ll see.  If they all find no shift, then we’re all happy with Einstein and the story is over.  If only OPERA finds a shift, and it is still 60 nanoseconds (or comparable), then we’ll know the OPERA folks still haven’t found the source of their problem.  If all the experiments find the same non-zero shift, we’ll start talking about Einstein and relativity again… but don’t hold your breath.

Everybody’s a Critic

I wanted to make a few assorted comments about the OPERA experiment’s painful climb-down, and about yesterday’s widespread response to it, which bothered me a lot.  You may want to read my initial post from yesterday, and also my attempt to sharpen the main question OPERA left unanswered in my second post.  

Over the past day I’ve learned enough to be pretty convinced (but not certain) that the situation that we are in is case (e) as described in yesterday’s post: that probably the previous OPERA experimental data is tainted and we can draw no conclusions from it at all.  It’s not that they found a problem that shifts their data so that it is consistent with Einstein’s relativity [case (b) from yesterday], and they can say that the neutrinos travel as expected.  (Press reports that said so are just wrong.) It’s that they found a problem that means their data from last year can’t be interpreted at all… at least, not at the moment, and maybe not ever.  If true, this would indeed mean that there is no longer any data from OPERA that can be used to measure neutrino speeds to good accuracy, and we’re back where we were before OPERA ran in the first place: with no reason to think there’s anything amiss with Einstein’s relativity equations.  As for OPERA, the only way forward is to rerun the experiment (apparently in March-April-May.)

[The NY Times article that appeared today (which attributes OPERA, a non-CERN experiment, to CERN; what has journalism come to these days?) has some additional details, but if you read it carefully, those details don't change anything written in this post.  See the first comment at the very end of this post.]

Ok, some comments. Continue reading

Synopsis of the OPERA Situation

I thought I’d better try to clarify what the logical issues are regarding OPERA before things get too confusing.  [Read the previous post first.] What’s going on is sketched in the Figure below.

a) In September (and confirmed in November) OPERA claimed to have found that, compared to expectations, neutrinos from CERN seemed to be arriving early, by about 60 nanoseconds, with a six sigma significance.  That is sketched in the figure as a bar, centered at 60 nanoseconds, with a width of 10 nanoseconds in each direction (so if you made the bar six times larger its bottom would reach zero nanoseconds.)    Such a result is convincing — convincing that either they made a mistake or they’ve discovered a new effect in nature.  The new effect in this case — neutrinos going faster than the universal speed limit — is very implausible for many reasons that I’ve covered in the past, but such an experimental result cannot simply be ignored.

(a) What OPERA said originally. (b) What yesterday's newspaper article claimed OPERA was now saying. (c),(d),(e) Three possible interpretations of OPERA's statement. In each case, a bar whose center lies at the most likely result of the measurement, and whose width indicates the degree of uncertainty, is shown. If we take OPERA's statement at face value, we still don't know if it is inconsistent with zero but less certain than before, consistent with zero, or simply unknown (in which case the previous measurement must be discarded.)

b) On February 22nd, a news report said that OPERA had found a mistake — a problem with the connection in an optical fiber — that explained the 60 nanosecond shift.  That would mean that the result was now — with confidence — consistent with Einstein’s relativity.

But the OPERA statement contradicts b).  Unfortunately it doesn’t clarify whether we have the situation c), d) or e):

c) The uncertainty on the result is larger than it was before, although the result is still not particularly consistent with what you would expect from Einstein’s relativity.  However, the reduced confidence in the result would mean that instead of it being an impressive result it would become a much less impressive one, much easier to ignore.

d) The uncertainty on the result is so much larger than it was before that the result is actually consistent with Einstein’s relativity, though so weak that it can’t distinguish at all between zero and the original non-zero value that OPERA claimed.

e) There is no sensible estimate of the uncertainty on the result. The result simply cannot be used and will have to be discarded.

From the point of view of the plausibility of the original OPERA result, (b), (c), (d) and (e) are all bad.  From the point of view of the experiment’s credibility, though, case (b) would look the best: the experimenters could at least say that they figured out what they did wrong and knew what it was.  Cases (c), (d) and (e) are increasingly bad; they indicate less and less knowledge of how their own experiment worked.  [But see the first comment below, which criticizes the way I expressed this, and emphasizes that a lack of knowledge is not always the fault of the experimenters.]  However, the situation might change over time; right now they might be in case (d) [because they're still working on understanding what happened] but soon it might switch to case (b), or back to case (a), once they have it straight.  So we do have to let things play out a little bit, and not jump to conclusions.

But I think it is clear we are not currently in case (b).  Because if we were, why would one would emphasize the re-running of the experiment?  There would be no need.

OPERA in Question

[UPDATE: Some extensive comments added below.]

[UPDATE: Journalists and Bloggers: PLEASE NOTE: OPERA is not a CERN experiment.  The CERN laboratory does not deserve the bad press it is getting (though they certainly unwisely put themselves in a position to receive it.)]

Many of you are probably already aware of various rumors running around By now you are all aware of yesterday’s initial report that the OPERA experiment — famous for announcing that neutrinos traveling from CERN to the Gran Sasso Laboratory in Italy arrived 60 nanoseconds (billionths of a second) earlier than expected, thus suggesting that neutrinos can travel slightly faster than the speed of light — had found a problem with a cable connector that exactly explains the 60 nanosecond timing shift.

But the immediate source of this rumor was a science journalist, and the article was based on an anonymous source who is not described as being in the OPERA experiment. And the details quoted in the article didn’t add up, in my view. Given the number of wrong reports and rumors that I have read over the past months about this experiment, my reaction was to wait.

I didn’t have to wait long. Presumably Perhaps to avoid misinformation from hitting the headlines, it appears that OPERA has released a statement  that indicates that the article from earlier today yesterday is not true. [Update: To be clearer, I probably should have written, ``true in its details.'']  But this statement itself contains big news. Continue reading

What to Watch in the Sky This Week: Beauty in Motion

Why does the sight of the Moon draw our gaze and silence our voices? What is it about the planets, those exceptionally bright points of light that wander among the stars, that we instinctively find so beautiful?  Is it perhaps that they make us dream of faraway, unreachable places? Is it that they are beacons in the night, nature’s candle flames, helping keep fear at bay, and offering us hope amid darkness? Or is it perhaps that they seem to float — we do love things that float, whether they be autumn leaves, balloons, clouds or birds — suspended in the sky, in apparent defiance of the force of gravity which keeps us pinned to the Earth?

This last thought offers a certain delicious irony… for in truth the planets and the Moon, in their procession above our heads, obey gravity’s dictates.

The next few days, weather permitting, will give us a chance to contemplate these questions. Our planet’s natural satellite, on its monthly trip around the Earth, will pass three of the brighter planets in the sky, creating one lovely spectacle after another. Of course, the Moon really passes nowhere near the planets, just as your outstretched hand, when it blocks your view of the Moon, is nowhere near the Moon itself. It is all a matter of perspective — of geometry, of cavernous spaces, of the play of light, and of the elegant choreography of the solar system.  But this perspective is not something we sense easily.  Our eyes can perceive no depth for objects so far away, and so our brains form a two-dimensional picture from the three dimensions of the universe, projecting the Moon, the planets and the stars, at extraordinary distances from one another, onto a psychologically flat black screen of the night sky. It takes great mental effort to see things as they are, and not as they appear. This, too, is worthy of contemplation.

First, on the night of February 22nd, just after sunset (don’t be late!), one of the most delicate of nocturnal sights awaits:   Click here to read more

How Do We KNOW a Proton Is So Complicated? (Data!)

Among the bridges that I hope to build, as I develop this website, is one connecting what we know today about nature with how we know it. After all, you’re reading my depiction of nature, based on how I think nature works.  I can try to assure you that my depiction is the mainstream viewpoint at the forefront of the research field — but you may still wonder if this website is legitimate, or if I might just be full of hot air, or if I might simply be mistaken. Well, my confidence in what I’m saying doesn’t come from having trained at some fancy university or my degree or from having been in the business for over 20 years. It comes from the data… in short, from nature itself.

So it’s important, I think, to link the data to the ideas and concepts, when it’s possible to do that.

You’ve heard the famous statement that “a proton is made from two up quarks and a down quark”.  But in this basic article, and this somewhat more advanced one, and in Wednesday’s post where I went into some details about what we know about proton structure, I’ve claimed to you that protons are actually chock full of particles, most of which carry a tiny fraction of the proton’s energy, and most of which are gluons, with a lot of quarks and antiquarks. [If this sounds unfamiliar, you should read those articles and posts before reading this one, which is a follow-up.]  And I claimed that these complications make a big difference at the Large Hadron Collider [LHC].

So should you take my word for this? You don’t have to.  Let me show you evidence.  From LHC data.  Here’s an article defending the main claim’s of Wednesday’s post.  It’s a near-final draft, still needing some proofreading perhaps, and probably some clarification, but I think it is fully readable now.  Enjoy it (and please feel free to give me feedback on its clarity, so I can improve it), or wait for the final version next week, as you see fit.  And have a great weekend!