Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!rpi!sarah!bingnews!kym From: kym@bingvaxu.cc.binghamton.edu (R. Kym Horsell) Newsgroups: comp.theory Subject: Re: Question on halting problem Keywords: for 10 bonus points... Message-ID: <1991May1.072918.844@bingvaxu.cc.binghamton.edu> Date: 1 May 91 07:29:18 GMT References: <1991Apr26.135918.8607@m.cs.uiuc.edu> <3132@ylum.Morgan.COM> Organization: State University of New York at Binghamton Lines: 32 In article jono@dec06.cs.monash.edu.au (Jonathan Oliver) writes: >There is indeed an upper limit on the amount of memory a computer can have, >since the universe is finite (approx 10^70 electrons from memory). The current ``popular'' success of the BB aside, I don't know that the finiteness of the (material?) universe has been proved. In any case here are some other outs -- (a) why use electrons? Maybe there is some class of thingy around here somewhere of which there _are_ an unbounded number. Since it _has_ been shown the lower bound on energy required for computation is zero (i.e. it can continue after any ``heat death'') we don't even require that thingy to have energy associated with it -- merely to be detectable (and I don't know how to detect something with zero rest energy, so don't ask :-). (b) The amount of information is not limited to the number of particles; but the number of energy states they can collectively access. A free particle can access an infinite number of states. If we consider the universe to be a closed system then collectively it is a set of free particles and can access an infinite number of energy levels (states). (There are obviously quite a few deep philosophical problems/questions here). (c) Various interpretations of QP may indicate info can be stored ``between the cracks'', so to speak :-) :-) Reality may know no limits. ;^) -kym