8 ms·

Faster-than-light neutrino result may have been due to bad connection

153 points by necubi 15y ago

jcfrei 15y ago
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 15y ago
  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.
lukeholder 15y ago
they just tightened the cable to see the error? science is scary.
- rauljara 15y ago
  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 15y ago
    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!
- geuis 15y ago
  It has little to do with science, and I don't understand your comment about science being scary. Science is simply method used to discover how things actually work. There is nothing "scary" about that. 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.
  - sharkbot 15y ago
    You're probably referring to is, "Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken", discussed here: http://news.ycombinator.com/item?id=1130463 http://news.ycombinator.com/item?id=1130463 Talk about scary...
    - geuis 15y ago
      Thanks! I was hoping someone would provide the link to that again.
- maaku 15y ago
  I don't know if scary is the word I would use. Exacting, that's for sure.
DanBC 15y ago
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/components/cable.htm 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).
nathanb 15y ago
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?
- rubidium 15y ago
  AFAIK, that was what someone suggested as a source of error, but that was never proved or supported. So... yes?
  - learc83 15y ago
    From what I read, that was just a suggestion from someone's blog that showed up on HN and reddit as if it was an accepted fact due to a poorly worded headline.
- sliverstorm 15y ago
  It was suggested repeatedly, and it was then repeatedly mentioned that GPS already takes relatively into account.
  - didgeoridoo 15y ago
    This comment got me wondering how important it is for navigation to take into account relativistic time dilation in GPS. Apparently: very. Turns out that ignoring it would cause a drift in position of about 10km/day. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
    - platz 15y ago
      nice dig!
- DanBC 15y ago
  META - why is nathnb's comment being down-voted? (It's not rude or aggressive or meme-spewing or vapid "me too" / "plus one".)
pessimist 15y ago
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...
- polemic 15y ago
  Surely this is just a reflection of the fact that science is performed by humans with limited resources. I mean, there is something to be said for getting the approximately result correctly many times over. 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.
  - pessimist 15y ago
    Agreed, its the nature of science. That's why theory is so important and why physicists pay as much importance to non-experimental features like "beauty" when judging theories. Experiments cannot be trusted unless explained by theory!
- siglesias 15y ago
deleted 15y ago
[deleted]
wavephorm 15y ago
Shouldn't they have tried to eliminate instrumentation errors before going public with findings that conflict with all human understanding of physics?
- Florin_Andrei 15y ago
  Shouldn't you eliminate ALL bugs from your software before you release it? All of them.
  - wavephorm 15y ago
    But bugs in my software don't prove Einstein wrong. There's a difference.
    - Florin_Andrei 15y ago
      The point was - you can't check everything beforehand. No matter how hard you try, there's always a non-zero probability that a bug will "prove Einstein wrong", or drive people into a ditch, or find horribly mismatched partners on a dating site, or explode toasters and kill puppies.
    - DanBC 15y ago
      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 15y ago
        Modern science - open source before Open Source was invented.
        adavies42 15y ago
        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.
jackfoxy 15y ago
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 15y ago
  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 15y ago
    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 15y ago
      And no one was claiming that.
- lurker17 15y ago
  What sort of experiment could test the hypothesis "x > c" in a binary way without depending on a precise measurement in a complex system? "x > c" is a binary test, BTW.
  - lmkg 15y ago
    Anything which is going faster than C in one inertial frame of reference, is going backwards in time in another inertial frame of reference, which allows for a violation of causality. I'm sure the experimental set-up would be complicated as balls, but a qualitative property like causality is probably more robust to measurement.
jacquesm 15y ago
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 15y ago
  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 15y ago
    > 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 15y ago
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/technology-faster-than-light-neutrinos.html http://www.cbc.ca/news/technology/story/2012/02/22/technolog...
ajuc 15y ago
> http://news.ycombinator.com/item?id=3252135 http://news.ycombinator.com/item?id=3252135 jonhendry, you're a prophet :)
azernik 15y ago
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."
gammarator 15y ago
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-neutrino-measurement-has-two-possible-errors.html http://blogs.nature.com/news/2012/02/faster-than-light-neutr...
joshmattvander 15y ago
Keep the dream alive!
deleted 15y ago
[deleted]

153 points by necubi 15y ago

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 15y ago
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.

lukeholder 15y ago

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

rauljara 15y ago
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 15y ago
  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!
geuis 15y ago
It has little to do with science, and I don't understand your comment about science being scary. Science is simply method used to discover how things actually work. There is nothing "scary" about that. 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.
- sharkbot 15y ago
  You're probably referring to is, "Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken", discussed here: http://news.ycombinator.com/item?id=1130463 http://news.ycombinator.com/item?id=1130463 Talk about scary...
  - geuis 15y ago
    Thanks! I was hoping someone would provide the link to that again.
maaku 15y ago
I don't know if scary is the word I would use. Exacting, that's for sure.

DanBC 15y ago

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/components/cable.htm 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).

nathanb 15y ago

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?

rubidium 15y ago
AFAIK, that was what someone suggested as a source of error, but that was never proved or supported. So... yes?
- learc83 15y ago
  From what I read, that was just a suggestion from someone's blog that showed up on HN and reddit as if it was an accepted fact due to a poorly worded headline.
sliverstorm 15y ago
It was suggested repeatedly, and it was then repeatedly mentioned that GPS already takes relatively into account.
- didgeoridoo 15y ago
  This comment got me wondering how important it is for navigation to take into account relativistic time dilation in GPS. Apparently: very. Turns out that ignoring it would cause a drift in position of about 10km/day. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
  - platz 15y ago
    nice dig!
DanBC 15y ago
META - why is nathnb's comment being down-voted? (It's not rude or aggressive or meme-spewing or vapid "me too" / "plus one".)

pessimist 15y ago

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...

polemic 15y ago
Surely this is just a reflection of the fact that science is performed by humans with limited resources. I mean, there is something to be said for getting the approximately result correctly many times over. 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.
- pessimist 15y ago
  Agreed, its the nature of science. That's why theory is so important and why physicists pay as much importance to non-experimental features like "beauty" when judging theories. Experiments cannot be trusted unless explained by theory!
siglesias 15y ago

deleted 15y ago

[deleted]

wavephorm 15y ago

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

Florin_Andrei 15y ago
Shouldn't you eliminate ALL bugs from your software before you release it? All of them.
- wavephorm 15y ago
  But bugs in my software don't prove Einstein wrong. There's a difference.
  - Florin_Andrei 15y ago
    The point was - you can't check everything beforehand. No matter how hard you try, there's always a non-zero probability that a bug will "prove Einstein wrong", or drive people into a ditch, or find horribly mismatched partners on a dating site, or explode toasters and kill puppies.
  - DanBC 15y ago
    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 15y ago
      Modern science - open source before Open Source was invented.
      - adavies42 15y ago
        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.

jackfoxy 15y ago

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 15y ago
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 15y ago
  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 15y ago
    And no one was claiming that.
lurker17 15y ago
What sort of experiment could test the hypothesis "x > c" in a binary way without depending on a precise measurement in a complex system? "x > c" is a binary test, BTW.
- lmkg 15y ago
  Anything which is going faster than C in one inertial frame of reference, is going backwards in time in another inertial frame of reference, which allows for a violation of causality. I'm sure the experimental set-up would be complicated as balls, but a qualitative property like causality is probably more robust to measurement.

jacquesm 15y ago

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 15y ago
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 15y ago
  > 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 15y ago

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/technology-faster-than-light-neutrinos.html http://www.cbc.ca/news/technology/story/2012/02/22/technolog...

ajuc 15y ago

> http://news.ycombinator.com/item?id=3252135 http://news.ycombinator.com/item?id=3252135 jonhendry, you're a prophet :)

azernik 15y ago

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."

gammarator 15y ago

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

joshmattvander 15y ago

Keep the dream alive!

deleted 15y ago

[deleted]