
Faster-than-light neutrino result may have been due to bad connection - necubi
http://news.sciencemag.org/scienceinsider/2012/02/breaking-news-error-undoes-faster.html
======
pessimist
The real issue is that experiments that give "expected" results are not
subject to this kind of scrutiny. Thus experiments are much less trustworthy
than one would assume. It sometimes takes decades for errors in experiments to
come out - eg. from "Surely your joking, Mr. Feynman":

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...

~~~
splat
Actually, most major experiments in particle physics these days (including the
OPERA experiment) avoid this sort of confirmation bias by being run "blind."
The scientists write all of their data reduction pipelines before taking any
actual data and test their pipelines on simulated data. When they are
confident that their pipeline is running as expected they run the experiment,
put the data through their pipeline and publish the result, no matter how
unexpected it is.

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.

~~~
jules
Physics is far ahead of other disciplines in this regard. Choosing your
statistical test after you gather the data, selectively removing "outliers"
after you gather the data, non-blind interpretation of pictures by humans who
have a stake in the outcome and only publishing statistically significant
results are all par for the course in e.g. neuroscience.

~~~
gammarator
This paper [1] points out that commonly-used measures of statistical
significance are downright meaningless when additional degrees of freedom are
hidden in the way you describe.

[1]
[http://people.psych.cornell.edu/~jec7/pcd%20pubs/simmonsetal...](http://people.psych.cornell.edu/~jec7/pcd%20pubs/simmonsetal11.pdf)

~~~
jules
It's even worse than that paper describes and this is something that every
statistics 101 class worth its salt points out: if you are allowed to choose a
statistical test after you've gathered your data _you can prove any conclusion
you want with arbitrarily high confidence_. Note that the paper does not list
choosing a test before you gather the data as a requirement. The only way to
do meaningful statistics is the way splat describes: describe exactly how
you're going to analyze it before you gather the data, then send the paper to
a journal which decides whether to publish it before the data has been
gathered, and then complete the paper by actually doing the experiment and
adding the data to the paper.

------
DanBC
While noodling around for more information I found this article which
describes some (completely unrelated) other super-conducting cable used at
LHC.

([http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach...](http://lhc-
machine-outreach.web.cern.ch/lhc-machine-outreach/components/cable.htm))

> _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)._

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jacquesm
I'm really impressed with how open this group was to be proven wrong and how
hard they worked to rule out or confirm error on their part.

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.

~~~
Maro
Wolfe-Simon and NASA is an absolute disgrace.

I think they could gain far more with a mea culpa than with living in denial,
which is what they seem to be doing.

~~~
rbanffy
> 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.

------
gammarator
Standard caveat: while Science is an extremely reputable outlet, this blog
post is unsourced. There hasn't been an official statement from the OPERA
collaboration yet.

Update: a spokesperson for CERN has confirmed "a problem with the GPS system."
[http://www.cbc.ca/news/technology/story/2012/02/22/technolog...](http://www.cbc.ca/news/technology/story/2012/02/22/technology-
faster-than-light-neutrinos.html)

------
azernik
The best comment on this, courtesy of Ars Technica:

>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."

------
ajuc
> <http://news.ycombinator.com/item?id=3252135>

jonhendry, you're a prophet :)

------
gammarator
The official statement from the collaboration:

"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...](http://blogs.nature.com/news/2012/02/faster-than-light-neutrino-
measurement-has-two-possible-errors.html)

------
jackfoxy
The best _pessimistic_ response I read to this experiment when it first came
out stated that overturning well-established theorems in physics should be
left to experiments where the result is clearly and simply binary, not where
the result is an extraordinarily precise measurement in a complex system.

~~~
nu23
Otoh, one of the early tests for general relativity was a minor deviation in
Mercury's orbit from what was predicted by classical mechanics. My rough
intuition is that inconsistencies can show up initially as faint flickers, but
once you investigate more closely, one can find interesting and prominent
counter examples.

~~~
jackfoxy
I'm not an expert on this, but I believe the deviation in Mercury's orbit was
easily observed and calculated, and thus became in a sense a binary call-out
of Newtonian physics. Until highly precise measurements of relativistic
velocities is common place, experiments like this are of course valuable and
interesting, but one instance of an experimental result like this cannot be
relied upon to supersede special relativity.

~~~
radarsat1
And no one was claiming that.

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jcfrei
the description of the error appears just too vague in my ears. due to "bad
connection between a fiber optic cable that connects to the GPS receiver"
seems unlikely, since it's first of all a very systematic error and secondly I
can't fathom how a fiber optic cable can have a bad connection - at least not
in this setting... unless they would've unintentionally bent the cable,
resulting in a higher error rate in the transmission of the signal but
shouldn't that show up in some network diagnostic tool?!

~~~
radarsat1
If the connector was bad or broken, there could be an air gap between the
fiber and the diode, creating an unwanted refraction that could introduce
transmission error.

------
nathanb
I thought they already proved that the faster-than-light neutrino was due to
relativity between the GPS satellite, the origin, and the destination? Did I
just hallucinate that?

~~~
DanBC
META - why is nathnb's comment being down-voted? (It's not rude or aggressive
or meme-spewing or vapid "me too" / "plus one".)

~~~
lepton
I didn't downvote, but nathnb's comment isn't adding anything to the
discussion. It's a personal aside about some confusion he is having; his last
question especially emphasizes that aspect.

But I see that several other comments at that level were also downvoted.

------
joshmattvander
Keep the dream alive!

------
wavephorm
Shouldn't they have tried to eliminate instrumentation errors before going
public with findings that conflict with all human understanding of physics?

~~~
Florin_Andrei
Shouldn't you eliminate ALL bugs from your software before you release it? All
of them.

~~~
wavephorm
But bugs in my software don't prove Einstein wrong. There's a difference.

~~~
DanBC
They didn't claim to have proved Einstein wrong. To continue the weird
analogy: They looked for the bug themselves, and couldn't find it, and then
asked other people to find the bug.

~~~
Florin_Andrei
Modern science - open source before Open Source was invented.

~~~
adavies42
pretty much. the mess newton caused by keeping calculus a proprietary
technology for so long (due partially to existing practice in the alchemy
industry and partially to being completely nuts) made it pretty clear that
some degree of openness was necessary to really get anything done.

------
lukeholder
they just tightened the cable to see the error? science is scary.

~~~
rauljara
Actually, from the beginning they've mentioned that equipment failure would be
one of the ways to account for the findings. They also have been incredibly
open in asking for help to explain the anomaly. I don't see this as scary at
all. Science has come out looking incredibly even keeled and reasonable. Some
of the news outlets that have covered the science... less so. But still,
almost every article I read had all the caveats listed even if there were have
some overly hopeful headlines.

~~~
mechanical_fish
Oh, "scary" is the right word, notwithstanding everything you just said, which
is all true.

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!

