Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!lanl!opus!ted From: ted@nmsu.edu (Ted Dunning) Newsgroups: comp.ai Subject: Re: Another letter to the New York Review Message-ID: Date: 26 Feb 90 21:48:33 GMT References: <18883@bcsaic.UUCP> <1589@skye.ed.ac.uk> <11488@venera.UUCP> <1754@skye.ed.ac.uk> <90Feb15.231415est.6212@neat.cs.toronto.edu> <2al902Zg8bnn01@amdahl.uts.amdahl.com> <3750@uceng.UC.EDU> Sender: news@nmsu.edu Followup-To: comp.ai Organization: NMSU Computer Science Lines: 32 In-reply-to: dmocsny@uceng.UC.EDU's message of 24 Feb 90 18:35:25 GMT In article <3750@uceng.UC.EDU> dmocsny@uceng.UC.EDU (daniel mocsny) writes: Can any phenomenon be so truly uncomputable that no logical process could behave equivalently (if not exactly)? yes. The presence of such phenomena would seem to imply a universe where theory is of no value at all. no. virtually all chaotic dynamical systems have the characteristic of a computational horizon beyond which any particular computer cannot keep up with the physical system in doing the simulation. the reason for this is that sensitive dependence on initial conditions requires that the arithmetic that needs to be done gets harder and harder to do fast enough to keep up with real time. before too long, you have a system which requires a computer larger than the entire universe to predict. all of this assumes that real numbers have some relevance to the real world, which would be pretty hard to verify. -- Offer void except where prohibited by law.