Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!munnari.oz.au!bruce!dec06!jono From: jono@dec06.cs.monash.edu.au (Jonathan Oliver) Newsgroups: comp.theory Subject: Re: Question on halting problem Keywords: for 10 bonus points... Message-ID: Date: 1 May 91 03:25:58 GMT References: <1991Apr26.135918.8607@m.cs.uiuc.edu> <3132@ylum.Morgan.COM> Sender: news@bruce.cs.monash.OZ.AU Lines: 18 In <3132@ylum.Morgan.COM> sethb@Morgan.COM (Seth Breidbart) writes: >>We pitiful humans are unable to build turing machines; nobody has ever >>constructed a computer that was more than a DFA, and nobody ever will >>(since all computers have a fixed amount of memory). >A Turing Machine need not start with an infinite amount of memory. If >I endow a foundation to add 1 tape square every year, then the memory >is eventually large enough, and a Turing Machine results. >In fact, if we consider USENET to be a single machine (why not?), and >assume it to be constantly growing, then it fits the definition. >Seth sethb@fid.morgan.com 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). Jon Oliver