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Speed of individual photons cannot exceed speed of light in avacuum
On 27/07/2011 12:16 PM, dlzc wrote:
I'm wondering if individual photons do exceed the speed of light, but we just don't detect them as they get filtered out by the direction of time? That is to say that time polarizes the photons. Quantum mechanics has "real propagating" photons as a series of virtual photons. So maybe the question is moot. I've always been a little puzzled by this statement. What is the difference between virtual photons and real ones? Aren't all virtual photons real at some point? Is it just the amount of time that they are in existence before being terminated? Yousuf Khan |
#12
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Speed of individual photons cannot exceed speed of light in a vacuum
On Jul 26, 12:07*pm, Yousuf Khan wrote:
BBC News - Time travel: Light speed results cast fresh doubtshttp://www.bbc.co.uk/news/science-environment-14289114 "Now, a paper in Physical Review Letters shows that individual photons too are limited to the vacuum speed limit. That means that photons maintain the principle of causality laid out in Einstein's theory of special relativity - that is, an event's effect cannot precede its cause by traveling faster than light. It is violation of this causality that would, in principle, permit time travel. While the limit in vacuum is a fixed number - some 300,000km per second - the speed of light can vary widely in different materials. " Well, that will hold forever on Earth, since it's a circular definition of cause, Bu, whether it holds in advanced alien science it a different question. |
#13
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Speed of individual photons cannot exceed speed of light in a vacuum
On Jul 26, 9:07*am, Yousuf Khan wrote:
BBC News - Time travel: Light speed results cast fresh doubtshttp://www.bbc.co.uk/news/science-environment-14289114 "Now, a paper in Physical Review Letters shows that individual photons too are limited to the vacuum speed limit. That means that photons maintain the principle of causality laid out in Einstein's theory of special relativity - that is, an event's effect cannot precede its cause by traveling faster than light. It is violation of this causality that would, in principle, permit time travel. While the limit in vacuum is a fixed number - some 300,000km per second - the speed of light can vary widely in different materials. " If the speed/velocity of light speeds up with having less medium, then what's holding our photons back at merely the dull roar of 300,000 km/ sec? (which is kinda slow) http://translate.google.com/# Brad Guth, Brad_Guth, Brad.Guth, BradGuth, BG / “Guth Usenet” |
#14
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Speed of individual photons cannot exceed speed of light in a vacuum
On Jul 26, 2:49*pm, Sam Wormley wrote:
On 7/26/11 11:07 AM, Yousuf Khan wrote: BBC News - Time travel: Light speed results cast fresh doubts http://www.bbc.co.uk/news/science-environment-14289114 Experiment shows time travel impossible * *http://www.abc.net.au/science/articl...25/3277064.htm Hong Kong physicists say they have proved that a single photon obeys Einstein's theory that nothing can travel faster than the speed of light, demonstrating that time travel is impossible. See:http://www.abc.net.au/science/articl...25/3277064.htm So what's filling up the IGM that's keeping our photons down to only 300,000 km/sec? Obviously the IGM isn't nearly as empty as we've been told. So why don't you start earning your keep by telling us what's out there? http://translate.google.com/# Brad Guth, Brad_Guth, Brad.Guth, BradGuth, BG / “Guth Usenet” |
#15
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/2011 1:31 PM, Yousuf Khan wrote:
On 27/07/2011 12:16 PM, dlzc wrote: I'm wondering if individual photons do exceed the speed of light, but we just don't detect them as they get filtered out by the direction of time? That is to say that time polarizes the photons. Quantum mechanics has "real propagating" photons as a series of virtual photons. So maybe the question is moot. I've always been a little puzzled by this statement. What is the difference between virtual photons and real ones? Aren't all virtual photons real at some point? Is it just the amount of time that they are in existence before being terminated? It's a legitimate question, although I would invite you to turn around the statement a little to say that all real photons are in fact virtual. Virtual photons can be reasonably be characterized as off mass-shell. This just shifts the question to be, how far off mass-shell do you have to be to be considered off mass-shell? Any particle with a finite lifetime (as ANY detected photon necessarily is) therefore exhibits an energy (and hence an invariant mass) spread, due to the uncertainty principle. It really is a matter of degree, or if you like, an arbitrary boundary. |
#16
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/2011 3:14 PM, Brad Guth wrote:
So what's filling up the IGM that's keeping our photons down to only 300,000 km/sec? It's worse than that. In units that make physical sense, the speed of light is 1. It's one because there is a finite speed limit, and 1 is the most natural finite number. Which number would you think would be more appropriate than 1? If you're asking why there is ANY finite speed limit at all, and why the speed of light can't be infinite, the answer is that *all* causal connections are bound by the structure of spacetime to be within a cone of slope 1. |
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/11 11:16 AM, dlzc wrote:
Quantum mechanics has "real propagating" photons as a series of virtual photons. So maybe the question is moot. David A. Smith David, is some accessible material for the layman concerning "real propagating" photons as a series of virtual photons? Thanks, -Sam |
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/11 3:09 PM, Brad Guth wrote:
If the speed/velocity of light speeds up with having less medium, then what's holding our photons back at merely the dull roar of 300,000 km/ sec? (which is kinda slow) Brad, throw away the concept of medium, or at least replace it the the "fabric" of space-time. |
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/2011 4:28 PM, Sam Wormley wrote:
On 7/27/11 11:16 AM, dlzc wrote: Quantum mechanics has "real propagating" photons as a series of virtual photons. So maybe the question is moot. David A. Smith David, is some accessible material for the layman concerning "real propagating" photons as a series of virtual photons? Thanks, -Sam I think David is simply pointing out that what we observe in reality are not bare particles but "dressed" ones. That is, the measured properties of these particles (like the anomalous magnetic moment of the muon, for example) do not jive with calculations unless those calculations treat them as dressed ones. Dressed particles necessarily include loop contributions, where the original particle disappears, is replaced by a virtual particle-antiparticle pair, and then the pair annihilates to produce another particle like the first. Thus, the real, dressed particle is at least to some order a series of virtual particles interspersed by loops. |
#20
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Speed of individual photons cannot exceed speed of light in avacuum
On 7/27/11 4:34 PM, PD wrote:
On 7/27/2011 4:28 PM, Sam Wormley wrote: On 7/27/11 11:16 AM, dlzc wrote: Quantum mechanics has "real propagating" photons as a series of virtual photons. So maybe the question is moot. David A. Smith David, is some accessible material for the layman concerning "real propagating" photons as a series of virtual photons? Thanks, -Sam I think David is simply pointing out that what we observe in reality are not bare particles but "dressed" ones. That is, the measured properties of these particles (like the anomalous magnetic moment of the muon, for example) do not jive with calculations unless those calculations treat them as dressed ones. Dressed particles necessarily include loop contributions, where the original particle disappears, is replaced by a virtual particle-antiparticle pair, and then the pair annihilates to produce another particle like the first. Thus, the real, dressed particle is at least to some order a series of virtual particles interspersed by loops. Thanks PD. -Sam |
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