On Thu, Jun 09, 2005 at 04:09:15PM -0700, Norman Samish wrote: > > Here's a variation. Is my interpretation correct? > > Suppose we take ten apparently identical ball bearings and put stickers on > each with the identifiers "1" through "10." We leave the room where the > balls with stickers are, and a robot removes the stickers and mixes the > balls up so that we don't which ball is which. However, the robot remembers > which sticker belongs on which ball. We come back into the room and pick > one ball at random to destroy by melting it in an electric furnace. If at > this point we ask "What is the probability that the destroyed ball is ball > '3'?" we can truthfully answer "My memory tells me that the destroyed ball > has a one in ten probability of being '3.' " > > However, by reviewing the robot's record we can see that "6" was, in fact, > the one destroyed. > > Does this mean that the quantum wave functions of all ten balls collapsed at > the moment we viewed the record and observed what happened to "6"? Or did > the wave function never exist, since the robot's record always showed the > identity of the destroyed ball, irrespective of whether a human observed > this identity or not?

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Yes and no. In a 3rd person description of the situation, the Multiverse has decohered into 10 distinct universes at the moment the robot decides which ball it picks up. What about the 1st person description? According to the interpretation I follow, the observer is in fact superposed over all 10 branches, and only collapses into a single branch the moment the observer becomes aware of the robot's record. A more conventional physics interpretation would have the conscious observer as belonging to a definite branch since the Multiverse decohered, but not knowing which. I understand that David Deutsch holds this interpretation, for example. There is certainly no 3rd person experiment that can be done to distinguish between these two interpretations, and the only 1st person experiment I can think of relates to tests of quantum immortality. I find it hard to believe the "no cul-de-sac" conjecture would hold in the latter case. Cheers -- *PS: A number of people ask me about the attachment to my email, which is of type "application/pgp-signature". Don't worry, it is not a virus. It is an electronic signature, that may be used to verify this email came from me if you have PGP or GPG installed. Otherwise, you may safely ignore this attachment. ---------------------------------------------------------------------------- A/Prof Russell Standish Phone 8308 3119 (mobile) Mathematics 0425 253119 (") UNSW SYDNEY 2052 [EMAIL PROTECTED] Australia http://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 ----------------------------------------------------------------------------

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