quote:We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end. Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses.
Freaky weird stuff. This is obviously how God is omnipresent.
[ May 19, 2006, 02:27 PM: Message edited by: Kent ]
Posts: 1434 | Registered: Nov 2002
| IP: Logged |
"The pulse of light is shaped like a hump with a peak and long leading and trailing edges. The leading edge carries with it all the information about the pulse and enters the fiber first. By the time the peak enters the fiber, the leading edge is already well ahead, exiting. From the information in that leading edge, the fiber essentially 'reconstructs' the pulse at the far end, sending one version out the fiber, and another backward toward the beginning of the fiber."
The information about the pulse is really all contained in the very leading edge of the pulse. That essentially "tells" the medium about the different frequencies of light in the pulse and the length of the pulse.
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light."
Granted, it is very weird, but it turns out that the group velocity of a pulse of light can be greater than the speed of light. The phase velocity can be greater than the speed of light. The peak velocity can be greater than the speed of light. But, before anyone starts to think up any amazing inventions, as always, no information or energy can travel faster than the speed of light.
Posts: 420 | Registered: Jan 2006
| IP: Logged |