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back to article OPERA grabs spanner, fixes kit, and slows down neutrinos

According to a breaking report from Science, last year’s famous faster-than-light neutrino finding has been attributed to a cable fault. The report says insiders at the OPERA collaboration have found that “a bad connection between a GPS unit and a computer may be to blame”. The experiment last year seemed to identify neutrinos …

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The most intelligent reaction I can think of

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHA

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Holmes

NOT an intelligent reaction.

Looks rather like standard work in precision measurement.

Noisy people (including sundry sunday-physicist bloggers) pushing extra-dimensional neutrino travel, string pretzel phenomena or imaginary mass will have to wait for another measurement discrepancy and in the meantime might fall back - if they are testosterone-fuelled enough - to neutrino-denial conspiracy theories. But really this is all as it should be. A suspicious result leads to publication leads to checking of gear and statistics which leads to the result disappearing. Thus the telenovela of "still no kinks in current physical models" continues.

Then again, it might reappear after even MORE checking.

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FAIL

Re: The most intelligent reaction I can think of

I think you mean "the most childish reaction i can think of".

This is how science works. Full credit to the OPERA team in being as open with this as they have been. They are (and have been from the start) more than prepared to accept that this is some sort of error and this is part of of that checking process.

They should not be mocked for reporting this, they should be credited. This rational, reasoned approach is the basis of science and has led to much progress.

Unlike your approach.

Grow up.

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Re: Re: The most intelligent reaction I can think of

Well, no.

If they were at all competent, they would have done these tests before they published their ridiculous result.

I hope they don't lose their jobs, but if they do, there's plenty of work for them in the Cold Fusion field.

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Re: Re: Re: The most intelligent reaction I can think of

They were doing lots of tests before they published. However it takes time to go through every bit of kit, measure it carefully & convince yourself that it's working as it should, or not. The team assumed there probably was some kind of measurement error in the original paper, and were in effect asking for help to identify the problem. Now they have, and the theoretical physicists can get on with what they were doing. No doubt some of them will be sad, as previously unseen phenomena showing up, if they can be substantiated, are the stuff of future Nobel prizes.

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Re: NOT an intelligent reaction.

Actually, the checking of the equipment should have been done BEFORE publication of the result. I'd say the early publication of the "surprising" result is more indicative of how badly the money race has already corrupted scientific pursuits. If you publish a "surprising" result, you get more funding to study it. Although it does reinforce the necessity of publishing raw data, experimental methods, and conclusions as the bedrock of science. Because the subsequent public beat-down seems to have prompted a second look at the experimental apparatus, which in turn revealed the true cause of the "surprising" results.

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Re: Re: NOT an intelligent reaction.

I seem to recall what they actually said originally was something along the lines of -

"We have this anomalous result which we consider is unlikely but we need input from our peers to suggest possible sources of error that we may not have already considered"

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Anonymous Coward

Opera

Not only are its neutrinos faster than everyone else's, but it was also the first large hadron collider to use tabs and restart exactly where it left off after a magnet quench.

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Unhappy

Let me be amongst the first to say-

Oh Bugger.

...and now back to the X-Factor.

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Pint

60ns fits into a millimeter gap?

Smallest nanoseconds ever.

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WTF?

Tightening a connector?

60 nanoseconds at the speed of light (299,792,458 m/s) would be nearly 18 metres. Taking into account the relative propagation speed of a signal in a typical coaxial cable at 0.7 they would need to take out 12 metres of cable. A poor connection might introduce resistance and a slow rise time, but if they are basing this measurement on the timing pulse output from a GPS receiver then they deserve the results they got.

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Re: Tightening a connector?

I very much doubt the delay is related to distance directly; much more likely normal behaviour of the serial protocol employed in the presence of errors (e.g. check and retry). Granted 60ns is very fast retry, but it's not un-imaginable.

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Anonymous Coward

Re: Can't get better than a Quik-Fit physicist

It sound like the kind of diagnosis you get when you take your car in for a minor fault, such as replacing an indicator bulb.

The mechanic then does that long sharp intake of breath and says, "Ooooooh, you know your oil filter's knackered, don'tcha? Look how it's all caked up with grease and dirty oil", pointing at the OUTSIDE of the filter, which has inevitably become covered in harmless dirt, hoping you're stupid enough to equate dirty on the outside with broken on the inside.

He then wipes the filter clean with a bit of white spirit when you're not looking and charges you £240+labour+parts+VAT+beer money for a "replacement unit and fitting"...

Oh god, you don't think OPERA went to PC World and got one of their in-house "engineers" to service the damn thing, with this being the explanation on the work sheet when it came back?!! Check to see if they also hard-selled OPERA into upgrading their RAM and hard drive at the same time, to make the neutrinos go faster.

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Boffin

Perhaps an impedance mismatch?

I could see the 60 ns difference occuring if they were detecting a pulse that had reflected off the poor connection, re-reflected at the far end, and come back. The extra round trip could easily make the 12m difference you're talking about if it were a 6m long cable. This type of reflection happens all the time in poorly-terminated cables.

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Anonymous Coward

Re: Tightening a connector?

The way things like this work is:

The GPS receiver outputs a pulse once a second (the 1PPS output).

You have a very stable oscillator at a high frequency, such as a cesium or rubidium oscillator. These types of devices can be "tweaked" a bit to run slow or fast, but once tweaked, will be very stable. That gives you a very fast clock (sub-nanosecond per click), that won't change in rate unless you tweak it.

Now, you need to tweak that clock to match the clock at the far end. You do that via GPS like this:

You make a 1PPS signal from your clock. You compare that with the GPS 1PPS signal - FOR A VERY LONG TIME (like, days), averaging the time difference between the pulses from your clock and from GPS. Any single pulse may show a lot of jitter (random noise-like errors), but if you average them over long enough you can remove the noise and get a good measurement of how they are drifting. You use that very averaged signal to make very small tweaks to your clock. Eventually, your 2 clocks are in sync. You can then use the very high frequency output of them to make very precise time measurements.

Now, if that 1PPS signal cable from the GPS is a bit loose, then the rise time of the pulse will be slower, and the pulse will act like it is delayed by the slower rise time. Thus, you will sync your clock with a built-in delay due to that slower rise time.

(If you want more info, look up NTP (network time protocol) and PTP (precise time protocol, a.k.a. IEEE-1588) and that will go into more detail about getting things synced up.)

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Re: Re: Tightening a connector?

Serial is at way too high a level for this, it'll be a cable from a GPS head unit not a decoder, I.E. the antenna and LNA.

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Re: Re: Tightening a connector?

That's just one of many reasons why you shouldn't use a GPS 1PPS output for anything requiring accurate timing. Use a proper GPS timing receiver that has a high accuracy clock built in that is directly compared against the measured GPS position/time solution, and will also tell you the difference to any other time signal of you feed it.

Atomic clocks are not stable. They are long term accurate, but need to be phase locked to a quartz crystal oscillator to produce a short term stable output. Chaos theory etc.

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@Bronek Kozicki -- Re: Re: Tightening a connector? -- 60ns in perspective.

For those who are trying to picture 60ns in a real world example here's one:

In a traditional 625-line studio-quality television picture 60ns represent the fastest black-to-white transition possible. That's to say it's the minimum 'smear' or maximum sharpness on an edge going from full back to full white.

At home on a domestic TV, this transient extends out to about 120ns due to the reduced bandwidth of the television broadcast system which is about 5MHz in bandwidth.

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Re: Tightening a connector?

I think you'll find it's a fibre optic cable, not a bit of wire..

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Right then.

I hope we've all learned a valuable lesson?

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Anonymous Coward

Re: Right then.

Yes, don't use Opera.

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Re: Right then.

Is it plugged in?

And did they try rebooting?

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Re-seating the cable?

They might as well have turned it off and on again!

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Get the Atomic Vector Plotter

Put the small plug into the small receptacle. Put the large plug into the large receptacle. Now all we need is a nice hot cup of tea as a source of Brownian motion...

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Anonymous Coward

Re: Get the Atomic Vector Plotter

It works better if you give it a fresh cup of really hot tea...

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So loose connectors make things go faster than light? Cool.

FTL starship drives here we come.

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Bah!

As expected (and anticipated by some people here when the original article ran), nothing to see.

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There *is* something to see.

...and that's good science. As a couple others have pointed out, a strange result got investigated, checked, re-checked, and now apparently discarded as erroneous. This is science working as designed and scientists setting a good example.

That can only be a good thing given all the bad examples out there. There are plenty of fields where the politics trumps the science. AGW is the obvious target around here -- on *both* sides -- but reproductive health is one I care more about. Physics seems to have escaped the problem so far, possibly because the public doesn't understand it well enough for it to be fuel for demagoguery.

Damn, now I have this mental image of some weasel going on about how the Light Sympathizers' refusal to believe in FTL neutrinos is holding us all back from FTL travel...and another weasel claiming that the Neutrino Sympathizers just want to open a wormhole to the lair of Azathoth....

(wow, spellchecker claims I spelled Demagoguery right on the first try.)

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Happy

Physics seems to have escaped the problem

Or what was it the famous man said about Physics and stamp collecting?

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Coat

Now if they could make it work with proxies properly...

..ooops sorry wrong Opera.

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Anonymous Coward

re. There *is* something to see.

"Physics seems to have escaped the problem so far, possibly because the public doesn't understand it well enough for it to be fuel for demagoguery."

I think that physics escapes from politics because it's (relatively) easy to measure the results and thus test the theories. Politicians fear to tread where testing can be performed, far better to meddle in areas of uncertainty.

The science behind the climate change (previously known as Global Warming even though it wasn't necessarily either of those) is physics - the science of matter and energy. The problem is that macroscopic systems that involve a lot of chaotic elements are hard to analyse and the timescales are beyond the scope of politics (i.e the next election).

The reproductive health issues tend to get overshadowed by "Sky Fairy" influence, and politicians like to be allied to the most vocal deity-botherers in their constituency as this is perceived as a vote-winner.

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Really

I can't believe that the biggest and most expensive science experiment on the planet are using some old SatNav gear for critical timing. Really.

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that's not the whole story.

Why not look at what Cern have to say? http://press.web.cern.ch/press/PressReleases/Releases2011/PR19.11E.html there are 2 possible effects. it's not quite so cut and dried as the reg/science mag make out. in fact they could even have been going faster than previously thought.

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Boffin

Wot no fanboi/droid trolls?

Is it just me, or do we seem to get a much better class of commentary on a physics article? Even the Opera comments are amusing rather than blatant trolls.

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Boffin

Re: Wot no fanboi/droid trolls?

I'd love to say it's because Register attracts a higher calibre of commentors, but the truth is most likely that for these kinds of purely scientific articles, all the normal commentors suddenly bust out their highly scientific knowledge and technical experience in order to prove how smart they are, leaving the trolls and fanbois to either:

a) Leave immediately, as they can't understand wtf is being said, so can't actually do trolling/promoting without being immediately spotted and ignored/destroyed.

b) Adapt to it by upscaling the intelligence of their own posts, which pretty much makes them near indistinguishable from a smart commentor who's argumentative.

Either way, a very nice change of pace from the usual, right?

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Anonymous Coward

Re: Wot no fanboi/droid trolls?

Yes, compare to the "DRM in HTML5" article comments.

I think certain topics attract certain kinds of posters. Pretty much any article about DRM or protecting intellectual property has the same net effect as burning a copy of the Koran on a US army base in Afghanistan. In fact, The Register should add a new icon to the list which symbolises that noise women in such angry mobs make. You know the one - "Ye ye ye ye ye ye ye ye ye ye ye ye ye ye ye ye ye!"

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Only half the story

More one-sided science reporting from El Reg?

"The OPERA collaboration has [...] identified two possible effects that could have an influence on its neutrino timing measurement. [...]. If confirmed, one would increase the size of the measured effect, the other would diminish it.

The first possible effect concerns an oscillator used to provide the time stamps for GPS synchronizations. It could have led to an overestimate of the neutrino's time of flight. The second concerns the optical fibre connector that brings the external GPS signal to the OPERA master clock, which may not have been functioning correctly when the measurements were taken. If this is the case, it could have led to an underestimate of the time of flight of the neutrinos."

Also, to all those conflating the OPERA experiment with the LHC: CERN does more than one thing...

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I for one...

... look forward to some fly-by-night outfit advertising their shite soldering as innovative time dilation technology.

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Conspiracy

Now they have confirmed they can build a time machine 'they' (the govt., Illuminati, Richard Branson, or whoever) need to squash the story and making it out to be an every day mistake that everyone can understand (even if they can't understand why it would have this effect) is a great way to do that.

That's the basics of the conspiracy theory, now how to we get it into the heads of the internet loons?

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Indeed

We can't have FTL technology left in the hands of beardy scientists, it's a military thing now.

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Ok then Opera, Cern

Now that you've "fixed" your kit, please do the experiment AGAIN

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Holmes

Re: Ok then Opera, Cern

Wow, great idea.

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Joke

Sounds like good investigative science to me

But how would we know they didn't just switch it off then back on again - that always makes things work properly!

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Mushroom

CERN: HEY LOOK EVERYBODY!! WE BROKE THE SPEED OF LIGHT!!!

EE*: Wait, what?

CERN: YES, THESE NEUTRINOS WE SENT ARRIVED 60 MS EARLIER THAN THEY WERE SUPPOSED TO!!! WE THINK WE MAY HAVE EVIDENCE AGAINST EINSTEIN'S THEORY OF GENERAL RELATIVITY!!

EE: Really? Try it again and see what happens.

CERN: SEE? SEEEE?? WE DID IT AGAIN!! 60 MS EARLIER, JUST LIKE LAST TIME!! DID YOU SEE IT? DID YOU? WE SAW IT!!

EL REG: So, it now looks like time travel, faster-than-light travel, plus a whole bunch of other things only seen in science fiction could be possible. Let's usher in the dawn of a new age in exploration and life in general.

EE: Believe it when I see it.

...

CERN: Umm...hey, guys. Remember when we broke the speed of light back then? Well...urrm <AHEM> it was a badly-terminated wire that threw off our measurements. And we fixed it and measured the time thing again, and it looks like those neutrinos may not have broken the speed of light after all. BUT STILL!! WE NEED MOAR FUNDING TO FIND THE HOGGS BOSON!! AND RANDOMLY SMASH OTHER PARTICLES TOGETHER AND CREATE ANTIMATTER!! WOOOOEEEEEE!!!

*Everybody Else

Explosion because it's the closest thing to a black hole I can think of, and I'm still waiting on the black hole to swallow the Earth from the inside.

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Anonymous Coward

@NukEvil

1) You make it sound like CERN set out to break the speed of light; whereas this was just something that was discovered in an experiment.

2) It was a 60 nanosecond difference, not a 60 millisecond difference; you're a million times out here.

3) It wasn't some kind of stunt to secure funding; CERN (IMHO) more than justifies its existence.

4) Calm down, no CAPS LOCK required.

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Re: @NukEvil

You missed the fact that he can't spell Higgs Boson.

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Coat

So I guess that means the Fat Lady

has finished her last aria?

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Coat

Underwear safe then...

May I be the first to congratulate Jim Al-Khalili's underwear on avoiding a premature digestive demise.

Coat because there's no underwear icon - which seems an odd oversight in this Paris-obsessed meta-reality, now I come to think of it...

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