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Post by StuartG on Sept 22, 2011 21:13:46 GMT 1
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Post by eamonnshute on Sept 22, 2011 23:57:47 GMT 1
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Post by StuartG on Sept 23, 2011 18:07:41 GMT 1
In trying to get a handle on this, the best place to start is with a general view of the subject... CERN News - May 2010: Neutrino oscillation observed by OPERA www.youtube.com/watch?v=ufCyDHSAvLEa .pdf entitled "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam" was found. Page 6 shows a block diagram of the timing system which seems to show a reliance for timing, to what extent is not clear, on GPS. The receiver [Rx] is a "Symmetricom Xli GPS receiver" as shown here www.symmetricom.com/products/gps-solutions/gps-time-frequency-receivers/XLi/ static.arxiv.org/pdf/1109.4897.pdfComment: GPS timing problems are not unknown. However it would have to be a 'constant' error otherwise it would have shown in the results, or some sort of 'delay' in the timing system. There seems to be another 'clock' within the system, that runs independently once started of the main timing sequence. Page 2... "Reference clock generation The CBCM contains its own clock generation which once initialised can run independently of the Global Positioning System (GPS). The One Pulse per Second (1PPS) signal is initially obtained from a commercial GPS satellite receiver, and a synthetic version is manufactured from a 10 MHz voltage controlled oscillator. By adjusting the period and phase of this clock, the system phase locks a synthetic 1PPS with the GPS version to within 20ns, the locking process may take hours to complete. The final 10 MHz local clock has a drift of less than one part in 10-11 per Month. These two signals, the local 10 MHz clock, and the synthetic 1PPS, are fed into the CTSYNC [4] reference clock generator in the CBCM. The CTSYNC produces the 40.000 MHz event encoding clock for the GMT, the basic period or Linac repetition rate clock, currently 1.2S, the 1 KHz coarse timing clock, and a 1PPS clock advanced in time by 100us for later cable length delay compensation. All these reference clocks are in phase with the advanced 1PPS, so that ticks of the 40.000 MHz correspond to 25ns increments in the advanced UTC second. Once the system is running, all that remains is to set the Second number of the next 1PPS, and the system is then locked to UTC. The required precision for setting the CBCM clock in this way is ~400 ms, so even the Network Time Protocol (NTP) could be used." Furthermore, in the next para it makes mention of "There are also many legacy hardware modules" but as this document is circa 2003 perhaps these latter remarks are irrelavent. accelconf.web.cern.ch/AccelConf/ica03/PAPERS/MP535.PDFGPS or length of the 'particle circuit' if there is a problem. Maybe it's correct that neutrinos [some] can travel at 'c' or faster, but then it doesn't seem sure if they are 'massless' or not? StuartG
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Post by StuartG on Sept 24, 2011 20:15:52 GMT 1
'Because a tachyon moves faster than light, we cannot see it approaching. After a tachyon has passed nearby, we would be able to see two images of it, appearing and departing in opposite directions. The black line is the shock wave of Cherenkov radiation, shown only in one moment of time. This double image effect is most prominent for an observer located directly in the path of a superluminal object (in this example a sphere, shown in grey). The right hand bluish shape is the image formed by the blue-doppler shifted light arriving at the observer—who is located at the apex of the black Cherenkov lines—from the sphere as it approaches. The left-hand reddish image is formed from redshifted light that leaves the sphere after it passes the observer. Because the object arrives before the light, the observer sees nothing until the sphere starts to pass the observer, after which the image-as-seen-by-the-observer splits into two—one of the arriving sphere (to the right) and one of the departing sphere (to the left). ' en.wikipedia.org/wiki/Tachyon"Despite the theoretical arguments against the existence of tachyon particles, experimental searches have been conducted to test the assumption against their existence; however, no experimental evidence [5] for the existence of tachyon particles had been found until the CERN laboratory in Geneva, Switzerland made public the results of an experiment with neutrinos[6] that found them 60 nanoseconds faster than light. The findings have yet to be independently duplicated." " Currently there is research from CERN and Laboratori Nazionali del Gran Sasso suggesting the existence of tachyonic neutrinos. More information will be provided in the coming days." .... "Speed One curious effect is that, unlike ordinary particles, the speed of a tachyon increases as its energy decreases. In particular, E is zero when v is infinity. (For ordinary bradyonic matter, E increases with increasing speed, becoming arbitrarily large as v approaches c, the speed of light). Therefore, just as bradyons are forbidden to break the light-speed barrier, so too are tachyons forbidden from slowing down to below c, because infinite energy is required to reach the barrier from either above or below." [Conventional massive particles that travel slower than the speed of light are sometimes termed "bradyons" or "tardyons" in contrast, although these terms are only used in the context of discussions about tachyons.]
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Post by StuartG on Sept 24, 2011 21:04:29 GMT 1
This BBC iPlayer programme helps explain a little about tachyons... In Our Time The Speed of Light www.bbc.co.uk/iplayer/console/p0038x9hor the main page... www.bbc.co.uk/programmes/p0038x9hthe reference is at 0:34:00 and starts group velocity/phase velocity. [aside: M bragg's programmes are generally good and I know he has an agenda to stick to, but I just wish one of the interviewees would say 'Melvyn, for once, just shut up and listen] Cherenkov Radiation This video is an advert but the first 1:32 will explain... www.youtube.com/watch?v=LMWI4j6i9nY
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Post by StuartG on Sept 28, 2011 7:33:16 GMT 1
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Post by StuartG on Sept 28, 2011 7:34:56 GMT 1
Can't help feeling that the GPS is suspect. No proof, just a feeling.
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Post by StuartG on Sept 30, 2011 16:53:55 GMT 1
Physics World "Do neutrinos move faster than the speed of light?" Sep 23, 2011 "... This is not the first time that a neutrino experiment has glimpsed superluminal speeds. In 2007 the MINOS experiment in the US looked at 473 neutrinos that travelled from Fermilab near Chicago to a detector in northern Minnesota. MINOS physicists reported speeds similar to that seen by OPERA, but their experimental uncertainties were much larger. According to the OPERA researchers, their measurement of the neutrino velocity is 10 times better than previous neutrino accelerator experiments. ..." physicsworld.com/cws/article/news/47283Faster-than-light [FTL] en.wikipedia.org/wiki/Faster-than-lightGain-assisted superluminal light propagation L. J. Wang, A. Kuzmich & A. Dogariu www.nature.com/nature/journal/v406/n6793/full/406277a0.htmlwww.nature.com/nature/journal/v406/n6793/pdf/406277a0.pdfJust as a matter of interest... How far can one travel from the Earth? Since one might not travel faster than light, one might conclude that a human can never travel further from the earth than 40 light years, if the traveler is active between the age of 20 and 60. So a traveler would never be able to reach more than the very few star systems which exist within the limit of 20-40 light years from the earth. But that would be a mistaken conclusion. Because of time dilation, the traveller can travel thousands of light years during their 40 active years. If the spaceship accelerates at a constant 1G, they will, after 354 days, reach speeds a little under the speed of light, and time dilation will increase their lifespan to thousands of years, seen from the reference system of the Solar System, but the traveller's subjective lifespan will not thereby change. If the traveller returns to the earth they will land thousands of years into the future. Their speed will not be seen as higher than the speed of light by observers on earth, and the traveller will not measure their speed as being higher than the speed of light, but will see a length contraction of the universe in their direction of travel. And as the traveller turns around to return, the Earth will seem to experience much more time than the traveller does. So, although their (ordinary) speed cannot exceed c, the four-velocity (distance as seen by Earth divided by his proper (i.e. subjective) time) can be much greater than c. This is similar to the fact that a muon can travel much further than c times its half-life (when at rest), if it is traveling close to c.[9] "Not only is the universe stranger than we imagine, it is stranger than we can imagine." Sir Arthur Eddington (1882 - 1944)
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Post by mak2 on Sept 30, 2011 19:44:10 GMT 1
60 nanoseconds faster than light in 2.4 milliseconds? An experimental error of 25 parts in a million could account for it.
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Post by StuartG on Sept 30, 2011 21:18:39 GMT 1
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Post by StuartG on Oct 4, 2011 13:47:37 GMT 1
"New Constraints on Neutrino Velocities" (Dated: September 30, 2011) "Thus we refute the superluminal interpretation of the OPERA result." arxiv.org/PS_cache/arxiv/pdf/1109/1109.6562v1.pdfPerhaps someone could interpret a little of what these gentlemen are saying, are they saying that CERN et al haven't done their sums right? That not enough of the known behaviour has been included in the calculations? I'm still stuck at the 'good experiment spoiled by a lousy clock' argument. GPS has its problems, but then so have 'phase locked loop'. The piece in #2 above, with all its convoluted timing chain is a recipe for problems. Perhaps they'd be better off taking their timing from a known regular 'pulse' from some pulsar or similar? www.seasky.org/celestial-objects/pulsars.html Anyone any ideas? StuartG
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Post by StuartG on Oct 4, 2011 17:34:19 GMT 1
Could this be a likely candidate? Science 6 November 1987: Vol. 238 no. 4828 pp. 761-765 DOI: 10.1126/science.238.4828.761 Millisecond Pulsar PSR 1937+21: A Highly Stable Clock L. A. RAWLEY, J. H. TAYLOR, M. M. DAVIS and D. W. ALLAN Physics Department, Princeton University, Princeton, NJ 08544. Arecibo Observatory, Arecibo, PR 00613. Time and Frequency Division, National Bureau of Standards, Boulder, CO 80303. Abstract The stable rotation and sharp radio pulses of PSR 1937+21 make this pulsar a clock whose long-term frequency stability approaches and may exceed that of the best atomic clocks. Improvements in measurement techniques now permit pulse arrival times to be determined in 1 hour at the Arecibo radio telescope with uncertainties of about 300 nanoseconds relative to atomic time. Measurements taken approximately every 2 weeks since November 1982 yield estimates of fractional frequency stability that continue to improve with increasing averaging time. The pulsar's frequency stability is at least as good as 6 x 10-14 for averaging times longer than 4 months, and over the longest intervals the measurements appear to be limited by the stability of the reference atomic docks. The data yield a firm upper limit of 7 x 10-36 gram per cubic centimeter for the energy density of a cosmic background of gravitational radiation at frequencies of about 0.23 cycle per year. This limit corresponds to approximately 4 x 10-7 of the density required to close the universe. www.sciencemag.org/content/238/4828/761.abstract.... "High-precision timing observations of the millisecond pulsar PSR 1937+21 at Nancay." adsabs.harvard.edu/abs/1995A%26A...296..169C
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