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Not so sure, but this is certainly interesting: http://news.sciencemag.org/sciencenow/2011/08/pushing-light-beyond-light-speed.htmlScientists figure out how to advance a light pulse forward in comparison to light speed. The article says no relativity violation. BUT... If you view the front edge of signal as a carrier and the pulse as a bit, even though the onset of the carrier arrives at light speed, doesn't the bit travel faster? And isn't a bit information? Hence...? Other thoughts?
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jim wrote:
Other thoughts?
I wrote an article on this subject back in 2004. It seems as though old physics experiments continue to be re-packaged as if it is something new. I do not see anything new here... its essentially the same superluminal electromagnetic wave propagation experiment performed in a slightly different medium. Some older related papers: bandwidth theorumhttp://www.phy.duke.edu/research/photon/qelectron/pres/nlo-2004/NLO2004.pdfhttp://www.optics.rochester.edu/workgroups/boyd/papers/Schweinsberg_EuroPhyLett_06.pdfSome other thoughts: You may be asking yourself "Hey... If they can do this with photons... why not fundamental particles?". I have pondered the same. If the No-cloning theorem is incorrect... it would imply that matter/energy and information could be transmitted to any location in the universe instantaneously. Beam me up Scotty! If I could create a small bubble universe here in my laboratory... and No-cloning theorem is incorrect... I might be able to obtain some control over all matter/energy in my own little world. Of course keeping track of the activity within my bubble universe would require alot of computations so I would probably need a computer... -TheArchitect
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I am pretty sure we have discussed the princeton experiments in this forum before. I think it was about 2005 when some kind of special light through cesium vapor demonstrated group velocities greater than the speed of light.  If group velocities in wave propagation can move faster than light, then 299,792,458 m/s is not a limit on the occurance of FTL, but simply a limit on the observability of FTL -- meaning one cannot observe FTL directly, but one can see the effects of FTL indirectly.
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I understand group velocity, but somehow this looks different to me. Group velocity can appear to move faster than light because it is an envelope modulating the actual waves. As I read this, it is not an envelope of light waves, but rather a continuous pulse of energy? They are using the argument of Fourier analysis - that a pulse can be decomposed into multiple waveforms of very specific frequencies. But it doesn't start that way, it is just a pulse. And by filtering, they move it forward faster than light? Frankly, I don't see how it is possible because the waveform would appear to have zero energy prior to the pulse. So moving the pulse forward via filtering would seem to create energy out of nothing at that point of the waveform.
Also, I don't understand statements like "speed the signal up so much that it arrived at the second sensor 221.2 nanoseconds before it reached the first one." Sounds like reverse causality to me, which I thought could only be done with FTL. I don't think group velocity explains all this. But I am willing to hear more arguments. jdlaw? anyone else?
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