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coolrainbow木虫 (著名写手)
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http://news.sciencemag.org/scien ... -undoes-faster.html BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame. Physicists had detected neutrinos travelling from the CERN laboratory in Geneva to the Gran Sasso laboratory near L'Aquila that appeared to make the trip in about 60 nanoseconds less than light speed. Many other physicists suspected that the result was due to some kind of error, given that it seems at odds with Einstein's special theory of relativity, which says nothing can travel faster than the speed of light. That theory has been vindicated by many experiments over the decades. According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos' flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis. |
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22楼2012-07-06 14:19:02
coolrainbow
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Nature连接： http://blogs.nature.com/news/201 ... ossible-errors.html Faster-than-light neutrino measurement has two possible errors 22 Feb 2012 | 22:49 GMT | Posted by Eugenie Samuel Reich | Category: Physics & Mathematics The OPERA collaboration, which made headlines in September with the revolutionary claim to have clocked neutrinos traveling faster than the speed of light, has identified two possible sources of error in its experiment. If true its result would have violated Einstein’s Special Theory of Relativity, a cornerstone of modern physics. OPERA had collected data suggesting that neutrinos generated at CERN near Geneva and sent 730 kilometers to its detector Gran Sasso National Laboratory were arriving 60 nanoseconds faster than a light beam would take to travel the same distance. Many physicists were skeptical but the measurement appeared to be carefully done and reached a statistically significant level. But according to a statement OPERA began circulating today, two possible problems have now been found with its set-up. As many physicists had speculated might be the case, both are related to the experiment’s pioneering use of Global Positioning System (GPS) signals to synchronize atomic clocks at each end of its neutrino beam. First, the passage of time on the clocks between the arrival of the synchronizing signal has to be interpolated and OPERA now says this may not have been done correctly. Second, there was a possible faulty connection between the GPS signal and the OPERA master clock. An anonymously sourced account on Science Insider today broke the news that OPERA may have made a mistake . That report says the faulty connection can account exactly for the 60 nanosecond effect. OPERA’s official statement stops short of that, saying instead that its two possible sources of error point in opposite directions and it is still working things out. Its statement reads in full: “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. While continuing our investigations, in order to unambiguously quantify the effect on the observed result, the Collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam will be available in 2012. An extensive report on the above mentioned verifications and results will be shortly made available to the scientific committees and agencies.” Caren Hagner, a member of OPERA at the University of Hamburg in Germany, says “For the moment the collaboration decided not to make a quantitative statement, because we have to recheck and discuss the findings more thoroughly.” At Fermilab, members of the MINOS collaboration (Main Injector Neutrino Oscillation Search) continue to try to make their own independent measurement of the speed of neutrinos, with initial results expected later this year. |
2楼2012-02-23 13:27:56
nyzhaoyin
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4楼2012-02-23 16:39:44
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