Someone care to explain this to me in layman terms? "The key to understanding their results is envisioning every pulse of sound or light as a group of intermingled waves. This pulse rises and falls with energy over space, with a peak of strength in the middle. [They] transmitted sound pulses from the sound card through a loop made from PVC plumbing pipe and connectors from a hardware store. This loop split up and then recombined the tiny waves making up each pulse. This led to a curious result. When looking at a pulse that entered and then exited the pipe, before the peak of the entering pulse even got into the pipe, the peak of the exiting pulse had already left the pipe. If the velocities of each of the waves making up a sound pulse in this setup are taken together, the "group velocity" of the pulse exceeded c." http://www.msnbc.msn.com/id/16599496 "Sound beyond the speed of light: Measurement of negative group velocity in an acoustic loop filter." by W. M. Robertson, J. Pappafotis, and P. Flannigan, Department of Physics and Astronomy, Middle Tennessee State University. Applied Physics Letters. Jan. 2, 2007.
I've had one year physics and calc but don't understand what has been accomplished here. They state, "before the peak of the entering pulse even got into the pipe, the peak of the exiting pulse had already left the pipe." I don't understand how this is possible?
what they are doing is measuring the propagation delay of a pipe. they are apparently using 2 or more pulses in a train. or . . . they are using one pulse and feeding one side to one length of pipe. another to a longer piece of pipe. by adjusting the delay of the pipe you can get the results indicated.
The information on the link is far too sparse to know accurately what they did and how they observed it and therefore what the conlusion(s) should be.
Group velocity is the key term. I don't fully understand what group velocity is, but it's often contrasted with Phase velocity. It's come up in the past in the context of superluminal light pulses - see this experiment published in Nature in 2000: Gain assisted superluminal light propogation. The idea was discussed at least as early as 1966 - Nonlinear amplification of light pulses
http://forums.hypography.com/genera...-demonstrate-quantum-teleportation-atoms.html Atoms are faster than light too. Even light can be faster than light as we can speed it up or slow it down, even teleport photons. So speed does not really exist. Speed only exists if distance is real, and on the quantum level it's not real. This means speed and distance exist when connected to certain sizes somehow. The smaller something gets, the less important speed or distance become. http://www.spaceref.com/news/viewpr.nl.html?pid=20993
