hotShot Posted October 18, 2011 Report Share Posted October 18, 2011 That special relativity idea seems to be wrong. Dr. T. Feldmann from the PTB Braunschweig who was involved in developing the method of time measurement claims that relativistic effects were taken into account and that Ronal A.J van Elburg made a mistake himself by adding signal- and satellite speed in a classical way instead of a relativistic way. So the mystery is still on. Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted October 18, 2011 Report Share Posted October 18, 2011 The last paragraph is the best: What got me was the earlier comment: "the tricky part is keeping the clocks at either end exactly synchronised." Doesn't Special Relativity say that there's no such thing as synchronized clocks? No, what it says is that "simultaneity is relative". Since clocks being synchronous is a series of simultaneous events (ticking every second together) this is a relative thing. The difficulty is synching them in your reference frame when you can't actually easily see both of them at the same time. This was (provisionally) their error. Quote Link to comment Share on other sites More sharing options...
semeai Posted October 19, 2011 Report Share Posted October 19, 2011 That special relativity idea seems to be wrong. Dr. T. Feldmann from the PTB Braunschweig who was involved in developing the method of time measurement claims that relativistic effects were taken into account and that Ronal A.J van Elburg made a mistake himself by adding signal- and satellite speed in a classical way instead of a relativistic way. So the mystery is still on. Do you have a link? What got me was the earlier comment: "the tricky part is keeping the clocks at either end exactly synchronised." Doesn't Special Relativity say that there's no such thing as synchronized clocks?No, what it says is that "simultaneity is relative". Since clocks being synchronous is a series of simultaneous events (ticking every second together) this is a relative thing. The difficulty is synching them in your reference frame when you can't actually easily see both of them at the same time. This was (provisionally) their error. Maybe a simpler way of putting it: Two clocks that are at rest with respect to each other have a notion of being synchronized. 1 Quote Link to comment Share on other sites More sharing options...
hotShot Posted October 19, 2011 Report Share Posted October 19, 2011 Do you have a link? http://heise.de/-1362506 As to "Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?" M V Berry, N Brunner, S Popescu & P Shukla answer that with "Probably not." http://arxiv.org/ftp/arxiv/papers/1110/1110.2832.pdf Quote Link to comment Share on other sites More sharing options...
semeai Posted October 19, 2011 Report Share Posted October 19, 2011 That special relativity idea seems to be wrong. Dr. T. Feldmann from the PTB Braunschweig who was involved in developing the method of time measurement claims that relativistic effects were taken into account and that Ronal A.J van Elburg made a mistake himself by adding signal- and satellite speed in a classical way instead of a relativistic way. So the mystery is still on.http://heise.de/-1362506 Thanks for the link. It makes complete sense that the people who think about time synchronization using GPS would already take into account relevant effects like this. After all, as we all know from xkcd, even general relativity is necessary for GPS to be accurate. That said, I'm not sure why there's the comment about there being an error. Maybe the reporter misunderstood, or put the researcher on the spot and it was a throwaway comment? Equation (2) in Elburg's paper is correct; he's not adding velocities. An analogous equation shows up as equation (8) in the paper cited in that news article as already taking into account the effect. Quote Link to comment Share on other sites More sharing options...
mike777 Posted October 20, 2011 Report Share Posted October 20, 2011 Thanks for the link. It makes complete sense that the people who think about time synchronization using GPS would already take into account relevant effects like this. After all, as we all know from xkcd, even general relativity is necessary for GPS to be accurate. That said, I'm not sure why there's the comment about there being an error. Maybe the reporter misunderstood, or put the researcher on the spot and it was a throwaway comment? Equation (2) in Elburg's paper is correct; he's not adding velocities. An analogous equation shows up as equation (8) in the paper cited in that news article as already taking into account the effect. so at this point there is an experimental error or not? Quote Link to comment Share on other sites More sharing options...
semeai Posted October 20, 2011 Report Share Posted October 20, 2011 so at this point there is an experimental error or not? No experimental error confirmed yet I guess. My take from the sources mentioned in this thread: The paper giving the "correction" didn't make a mistake in its physics, but the original paper presumably used GPS time calibration that already included the physics "correction," according to some guy who knows about GPS time calibration. Quote Link to comment Share on other sites More sharing options...
hotShot Posted October 20, 2011 Report Share Posted October 20, 2011 No experimental error confirmed yet I guess. My take from the sources mentioned in this thread: The paper giving the "correction" didn't make a mistake in its physics, but the original paper presumably used GPS time calibration that already included the physics "correction," according to some guy who knows about GPS time calibration.While I can't say anything about the physics involved., I can tell you that the PTB is the german equivalent of the NIST. One of it's main objectives is to synchronize clocks and to evaluate and develop methods for accurate time measurement . "This guy" finished his ph.d. thesis on "Advances in GPS based Time and Frequency Comparisons for Metrological Use" this year.Part of this was " Improved GPS-Based Time Link Calibration" to be found here:http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/2010_Esteban_Improved_GPS-based_Time_Link_Calibration_Involving_ROA_and_PTB.pdf So I think that he knows about this stuff. Quote Link to comment Share on other sites More sharing options...
semeai Posted October 20, 2011 Report Share Posted October 20, 2011 While I can't say anything about the physics involved., I can tell you that the PTB is the german equivalent of the NIST. One of it's main objectives is to synchronize clocks and to evaluate and develop methods for accurate time measurement . "This guy" finished his ph.d. thesis on "Advances in GPS based Time and Frequency Comparisons for Metrological Use" this year.Part of this was " Improved GPS-Based Time Link Calibration" to be found here:http://www.ptb.de/cm...ROA_and_PTB.pdf So I think that he knows about this stuff. I didn't mean "some guy" to be disparaging. However, as you imply, "an expert on" would have been better wording than "some guy who knows about." By way of lame excuse, maybe I can erroneously suggest that I have a high bar for using the word "know(s)." Quote Link to comment Share on other sites More sharing options...
barmar Posted October 23, 2011 Report Share Posted October 23, 2011 If high-energy physics were easy, everyone would do it. Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted November 18, 2011 Report Share Posted November 18, 2011 I'd still back Einstein (as per several XKCD strips) but apparently the experiment has been repeated. Oh, and doesn't The odds have shrunk that Einstein was wrong about a fundamental law of the Universe. mean that it's less likely that Einstein was wrong? Why put a sentence like that in front of an article describing how an experiment "showing" he was wrong has been repeated? Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted November 18, 2011 Report Share Posted November 18, 2011 One question for the physicists (or physics knowledgeable people). If the neutrinos really are going faster than light, shouldn't they arrive before they are produced? Or is the theory that relativity is completely wrong with regards to faster than light travel and its effects? Quote Link to comment Share on other sites More sharing options...
S2000magic Posted November 18, 2011 Report Share Posted November 18, 2011 Oh, and doesn't "The odds have shrunk that Einstein was wrong about a fundamental law of the Universe" mean that it's less likely that Einstein was wrong? Why put a sentence like that in front of an article describing how an experiment "showing" he was wrong has been repeated?Not the way it's written; if it had said that the odds against Einstein being wrong had shrunk, it would mean that it's less likely that he was wrong. (In your defense, the author of the sentence you quoted probably meant the odds against Einstein being wrong, and fouled it up; most laymen, in my experience, don't understand that the common (mathematical, statistical) use of "odds" refers to odds against something happening.) Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted November 18, 2011 Report Share Posted November 18, 2011 Not the way it's written; if it had said that the odds against Einstein being wrong had shrunk, it would mean that it's less likely that he was wrong. (In your defense, the author of the sentence you quoted probably meant the odds against Einstein being wrong, and fouled it up; most laymen, in my experience, don't understand that the common (mathematical, statistical) use of "odds" refers to odds against something happening.) Thanks for clearing that up, I was suspicious about the use of the term. So much for all the probability theory I took in grad school. We never discussed "odds" as a term like this. Quote Link to comment Share on other sites More sharing options...
gwnn Posted November 18, 2011 Report Share Posted November 18, 2011 One question for the physicists (or physics knowledgeable people). If the neutrinos really are going faster than light, shouldn't they arrive before they are produced? Or is the theory that relativity is completely wrong with regards to faster than light travel and its effects?They should arrive in imaginary time, or not? There will be some negative numbers under some square roots I guess. Quote Link to comment Share on other sites More sharing options...
Mbodell Posted November 18, 2011 Report Share Posted November 18, 2011 One question for the physicists (or physics knowledgeable people). If the neutrinos really are going faster than light, shouldn't they arrive before they are produced? Or is the theory that relativity is completely wrong with regards to faster than light travel and its effects? My non-expert physics answer is: It depends on your frame of reference. From the frame of reference of where they arrive you'd see them arrive and then you'd see the light from where they were created later. From an external frame of reference roughly equally distant from the start and end of the path, you'd see them where they started. So faster than light doesn't necessarily mean backwards in time in the linear way some folks expect. Quote Link to comment Share on other sites More sharing options...
barmar Posted November 19, 2011 Report Share Posted November 19, 2011 One question for the physicists (or physics knowledgeable people). If the neutrinos really are going faster than light, shouldn't they arrive before they are produced? Or is the theory that relativity is completely wrong with regards to faster than light travel and its effects?If that part of the theory is correct, I think it states that time should go backward in the frame of reference of the neutrinos. That's not the same as the frame of reference of the observers measuring the departure and arrival times from their labs. Unfortunately, neutrinos have neither wrists nor pockets, so there's nowhere to put a watch on them to see what's happening in their time. But in any case, if Einstein was wrong about the speed of light being a fundamental limit, it throws into question all the conclusions that come from it, including time dilation. Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted November 19, 2011 Report Share Posted November 19, 2011 But in any case, if Einstein was wrong about the speed of light being a fundamental limit, it throws into question all the conclusions that come from it, including time dilation. Time dilation from (both special and general) relativity has been confirmed in lots of experiments (including every time someone uses GPS). I'm not so worried that what happens in most observable relativistic effects is wrong, it's this possible faster than c speeds that are weird. Quote Link to comment Share on other sites More sharing options...
shyams Posted November 20, 2011 Report Share Posted November 20, 2011 Not the way it's written; if it had said that the odds against Einstein being wrong had shrunk, it would mean that it's less likely that he was wrong.The opposite. It is more likely now that Einstein was wrong. When odds shorten, the probability increases Quote Link to comment Share on other sites More sharing options...
nige1 Posted November 21, 2011 Report Share Posted November 21, 2011 There was a young lady named Bright Who travelled much faster than light.She departed one day In a relative way And returned the previous night. There was a young fellow named Fisk At fencing exceedingly brisk. So fast was his action, The Fitzgerald contraction Reduced his rapier to a disk. Quote Link to comment Share on other sites More sharing options...
gwnn Posted November 21, 2011 Report Share Posted November 21, 2011 Bernoulli's equation has always been my favourite in Physics, but especially after I've heard this song: Superb Calculation of the Pressure in a Fluid new words by R. M. Panoff Tune: Supercalifragilisticexpialidocious Bernoulli knew he had a rule he used for wings in air For fluids incompressible he'd never have a scare. The density of energy's the same at every spot A caveat is cavitation in which case it's not! Oh, Superb calculation of the pressure in a fluid Is simple so that anyone with any sense can do it. We all deserve a force conserved among the objects paired. Just add to pressure rho gee aitch then add half rho vee squared A water tower tower's o'er a town so water goes Through every pipe, and when you turn the faucet on it flows. The pressure head is now instead a steady stream, you see, The pipe's diameter determines stream velocity. The sum at every point's a constant, check it if you care Each term can change within a range for water or for air. The key's to keep the units straight and don't have any gap Or else your fluid starts to leak and then you'll just get Oh.... 1 Quote Link to comment Share on other sites More sharing options...
barmar Posted November 21, 2011 Report Share Posted November 21, 2011 I'd still back Einstein (as per several XKCD strips) but apparently the experiment has been repeated. Oh, and doesn't "The odds have shrunk that Einstein was wrong about a fundamental law of the Universe" mean that it's less likely that Einstein was wrong? Why put a sentence like that in front of an article describing how an experiment "showing" he was wrong has been repeated?Where did you see that line? The first of the article is "The chances have risen that Einstein was wrong about a fundamental law of the universe." Quote Link to comment Share on other sites More sharing options...
gwnn Posted November 21, 2011 Report Share Posted November 21, 2011 I guess they changed the article. It did start with "the odds have shrunk". Quote Link to comment Share on other sites More sharing options...
BunnyGo Posted November 21, 2011 Report Share Posted November 21, 2011 Interesting, I guess an editor (or the author) didn't like that line either. Quote Link to comment Share on other sites More sharing options...
whereagles Posted December 6, 2011 Report Share Posted December 6, 2011 I can't wait to travel back in time, it's only a matter of time... or is it? Probably not. A series of people (myself included) have given evidence for the impossibility of time-travelling into the past. You can time-travel into the future, but into the past is a whole other ball game. In case you're wondering, to travel into the future you "just" hop on a spaceship, accelerate close to the speed of light and spin around a bit. When you're back, there will be more time enlapsed on Earth than in the spaceship, so you effectively travelled into the future. Quote Link to comment Share on other sites More sharing options...
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