On 11 Sep 98, at 16:44, Pete Weiss wrote: > >The analogy that I like to use is how do you undo the throwing of a >ping-pong ball into a room of armed mouse-traps each of which has a >ping-pong ball attached? > >/Pete This is a much cooler analogy to visualise if you're old enough to remember that Disney (?) educational film on what nuclear fission looked like. ;-)