A graduate student here at the Physics Department is a former roommate of mine, so I will periodically bug him with things that I don't know and I think he should. This time, I thought he had a GPS (Global Positioning System) receiver, and could tell me exactly where we are located. Oh, yes, last time I asked him this question, the department moved to a new building. In any case, our correspondence: ---------- > To: Jeff George <georgej@dumand.phys.washington.edu> > From: Mike Andersson <anderss@u.washington.edu> Jeff: Can you tell me exactly where we are (GPS)? ---------- > From: Jeff George <georgej@dumand.phys.washington.edu> > To: Mike Andersson <anderss@u.washington.edu> [two weeks later] Mike: I haven't responded to your question because I do not yet know where we are. In fact, I am somewhat hesitant to find out. As a fine example of Heisenberg's uncertainty principle, last time you asked me about the position of the building, that knowledge caused great uncertainty in the momentum of the building. It is now exceedingly likely that we are somewhere else. Aside from the fact that having a building with very uncertain momentum could be quite dangerous to neighboring structures and passersby, I simply don't have the time or the inclination to keep packing up our lab every time you want to know where we are. ---------- Jeff: OK, so how about if I determine the momentum of the building to be zero? Can you tell the location *then*? ---------- Mike: If you find it is near zero, fine, the building isn't moving. But if you find that the building's momentum is exactly zero, you won't have the foggiest idea where it is. Furthermore, I have no objection to your making this momentum measurement as long as you do not share the results with me. I have a hard enough time getting getting myself from the bus to my lab that early in the morning without making the location of the building even more uncertain. More importantly, since you're staff, I do not know if the state employee handbook allows the inability to find the worksite to be a valid excuse for absenteeism. ---------- By the way, I still don't know exactly where I am. :-)
(From the "Rest" of RHF)