Faulty Cable To Blame For Superluminal Neutrino Results

smolloy writes "It would appear that the hotly debated faster-than-light neutrino observation at CERN is the result of a fault in the connection between a GPS unit and a computer. This connection was used to correct for time delays in the neutrino flight, and after fixing the correction the researchers have found that the time discrepancy appears to have vanished."

This isn't definite

[JoshuaZ]

There's no definite statement from OPERA or CERN yet. Right now this is just a rumor. This also is definitely not the first suggested explanation. Let's wait and see.

Re:Headline is wrong

[ceoyoyo]

Don't believe everything you read in a summary. They found a loose cable that could have caused the delay. They're checking now. Despite the slashdot headline and summary, nothing has been confirmed.

Re:Glad they found the error

[gstrickler]

The cable transmitted the signal 60ns faster than the time used in their compensation. I wouldn't call that defective.

Either the cable is shorter than they thought, or it's propagation factor is higher than specified, or they simply used the wrong number in their original calculations.

Way too early to blame anything on the cable manufacturer.

Re:Headline is wrong

[UnknowingFool]

He meant the original results showing FTL have not been reproducible by anyone other than the original team. It seems that after fixing the cable, the original team has been unable to reproduce the same results of the original test. Hence, FTL results were most likely due to the cable.

Re:XKCD pretty much predicted this

[Chris Burke]

Uh many, many people predicted that it would turn out not to be true. An error was considered the most likely explanation from the beginning, even by the publishers.

And much like the XKCD author, everyone who predicted that it wouldn't be true would have been ecstatic to be wrong.

What I find much more amusing is all the people who instantly jumped on the result and assumed it was true and proof of whatever they wanted it to be proof of -- from 'science is all a lie' to 'my replacement for Relativity which The Man has stifled is now proven correct!'

Re:Glad they found the error

[NEDHead]

even if the propagation was at the speed of light through the cable, it would mean about a 60 length discrepancy. Unlikely to be missed

Re:This isn't definite

[ananyo]

It's more than a rumour, as this later report from Nature [slashdot.org] makes clear. There is an OPERA statement circulating today that suggests two potential problems with the set-up. One is the one reported here - the cable issue - the second is a problem with "the experiment’s pioneering use of Global Positioning System (GPS) signals to synchronize atomic clocks at each end of its neutrino beam". But you're right - they haven't made a public statement yet nor been able to quantify yet the contribution of each to the potential error. It doesn't look good for them though.

Re:Face it

[sneakyimp]

Ahem. *bullshit*.

The heliopause, which has not yet been reached by Voyager 1 is apparently 23 x 10^9 km [universetoday.com] from earth. Alpha Centauri [wikipedia.org], the nearest star to our sun is 4.366 light years away which is 4.1306 x 10^13 km away.

If it has taken 38 years for Voyager 1 to reach the Heliopause, it would take 1,795.9 times as long to reach Alpha Centauri at that speed which comes out to something like 68,000 years. I'm assuming a couple of things of course:
* the speed so far is roughly the speed it will continue to travel
* it can escape the sun's gravitational well.

Suppose we are somehow miraculously able to accomplish the following:
* we send a system powerful enough to transmit an intelligible signal to us across 4.5 light years of space
* we somehow manage to travel 100 times faster than Voyager 1

You're still talking about roughly 680 years for it to get there. There might be some tiny relativistic effects that come into play, but I doubt they would alter the situation much. Are you sending humans? If so, you have to dramatically increase the weight of the vehicle to accommodate life-sustaining water/air/energy in which case you also need shit loads of propellant if you want to slow down on the other end. Forget entirely about the difficulty of insuring the survival of roughly 20 generations of humans against the problems of cosmic radiation and health and reproductive problems related to roughly a millenium spent weightless and getting fried by space rays.

Re:Glad they found the error

[c0lo]

Suffice to say that science still insists on verification, which government abhors.

FTFY. Not to worry though, it won't take long [slashdot.org]; after all precedents exist [wikipedia.org] and, if the electorate require [slashdot.org] it, I'm sure the politicians will oblige [thechicagodope.com] ( ;) [xkcd.com] )

Re:I don't understand

[bobbied]

Sorry but you are going to have to start shoveling. Consider that GPS can routinely produce location solutions measured in tens of meters in a small fraction of a second. Also consider that if you avarage the time signals recovered over long periods of time you can generate time bases that are very high granularity. I'll Quote from NIST.gov... "Tests between widely separated receivers have demonstrated standard uncertainties for time comparisons of less than 10 ns and relative standard uncertainties for frequency comparisons of less than 1 x 10-13, both for averaging times of 1 d. The frequency uncertainty decreases as the averaging time increases. The frequency uncertainty is limited by the relative standard uncertainty of the NIST primary frequency standard which is 2 x 10-15." That's not even for GPS, but for ground based radio. GPS is similar accuracy and 1x10-13 is better than a pico second after a day of observations.

Wiki article has the best technical summary so far

[funkboy]

So, it seems that the previously calculated stddev was -5.9/+8.3ns [wikipedia.org], which is about double the certainty of the best COTS systems (it had better be, they're plugged directly into atomic clocks). Basically:

"A loose connection between the fiber link from a GPS receiver to a computer is thought to cause the 60 nanosecond delay; tightening the connection makes the delay through the fiber decrease. However, additional data has to be taken to test the hypothesis. A second error with the crystal oscillator is expected to have lengthened the reported flight-time of neutrinos. Repeat tests with short pulsed beams have been scheduled for May. The two errors affect the result in opposite ways. The OPERA collaboration has not released quantitative estimates of how the errors affect the results, and expect to check the effects directly when a bunched beam is available later in 2012."

So this thing is far from over...

Re:Glad they found the error

[jpapon]

Neither photons nor electrons travel near C in a cable, they travel around 0.6C-0.7C

Not to be pedantic, but electrons do not travel anywhere near "0.6C-0.7C" in a cable. The signal may propagate (outside of the cable) at that velocity, but the electrons themselves move much much slower.

Re:Glad they found the error

[stjobe]

Prove it false, and you are out of a job.

A proof is sufficient evidence or argument for the truth of a proposition, never for the falsity of a proposition.

Re:Glad they found the error

[c0lo]

How is this being modded informative?

( ;) [xkcd.com] )

Because I provided a way to signal a tongue-in-cheek type of post without the smiley-between-brackets looking wrong?