Hi Horace. You write: >It seems to me that if the group velocity can be sensed at 3*c then that >constitutes data transmitted FTL.
Let's look at that graph again. http://physicsweb.org/articles/news/8/11/10/1/041110 Notice how the light speed delayed pulse is larger than the slow or fast wave? Let's imagine two machines as you describe, the only difference being that one is implemented using the fast wave and the other with the light speed delayed signal ( the large one ). If I set the detector to trigger at the peak ( roughly the "center of mass" of the energy of the pulse ) the fast wave will be faster than the delayed wave. If I set the trigger at the 50% point on the risetime, now my light speed delayed system is going to be faster than my fast wave system. Hmmm, that doesn't seem very attractive now. does it? Frankly, IMHO, the math is not adequate to describe the physical system. I agree with the authors that a new velocity definition is needed. I have no problem with FTL transmission, I just want to actually DO IT and judge the physical implementations accordingly... By the way, things do get more interesting when the transmission media is nonlinear and active. What is described on the site is pretty much the argument about tunnelling in QM, it's easy to build macroscopic models with radio techniques that behave the same way as the quantum systems do. One can see the same results as this experiment. However, you can probe the radio system much more intimately than the QM system. Very enlightening. Here's some more refs. http://www.aei-potsdam.mpg.de/~mpoessel/Physik/FTL/tunnelingftl.html This guy in particular has some interesting work. http://www.ph2.uni-koeln.de/Nimtz/pub/paper-list.html K.
