The classic example of the latter is to consider a rotating beacon such as a lighthouse or an airport beacon which sends out a bright beam of light that falls on a distant wall or perhaps the side of a cliff. The spot of light cast by the beam moves across the wall with a linear velocity v equal to r<omega>, where <omega> is the rate at which the beacon turns in radians/second. For sufficiently large r, v can be greater than c, that is, the time it takes the light to swing from point A on the wall to point B, divided into the linear distance between A and B yields a result which is >c. However, no _information_ can be transmitted from an observer at point A to another observer at point B at a speed greater than c. Frex, if A has a switch which can turn the light on or off, and as soon as he sees the beam he hits the switch to turn the light off, it will take longer for the electrical signal from the switch to reach the light than it will for the light to swing to B, so the light will still be on when it reaches B.
Unfortunately, on another list, there has been one poster who has been insisting for several months that he has come up with a way to transmit information faster than light using a slight modification of such a setup, regardless of what everyone else has pointed out to him . . . Ronn Can I ask: There are spinning pulsars and other objects which emit a beam of energy, right? I know we can't 'see' the energy like the original Enterprise phasors, but can we prove any warping of the energy beams from this pulsar? I'm assuming that for some distance around the pulsar the beam is straight, but after some distance it would start to drag, look more like a pinwheel? Moot question, obviously pulsars are in our past, and we would have to wait for the galaxy to rotate a half turn to measure any difference in the pulsars arrival time. Kevin T. What I lack in vocabulary equals what I lack in intelligence _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
