Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!uccba!uceng!dmocsny
From: dmocsny@uceng.UC.EDU (daniel mocsny)
Newsgroups: comp.ai
Subject: Re: Simulation verus reality
Summary: Mind Storms.
Message-ID: <865@uceng.UC.EDU>
Date: 13 Apr 89 19:27:23 GMT
References: <827@htsa.uucp> <5227@cs.Buffalo.EDU> <864@uceng.UC.EDU> <5244@cs.Buffalo.EDU>
Organization: Univ. of Cincinnati, College of Engg.
Lines: 49

In article <5244@cs.Buffalo.EDU>, rapaport@sunybcs.uucp (William J. Rapaport) writes:
> I was thinking of the sort of computer simulation of a hurricane that
> the weather service might construct, not a machine that produces a
> hurricane artificially.  The latter ought to get you wet; the former
> wouldn't.

The hurricane simulation that the weather service might construct
outputs a list of numbers representing the velocity field of the
hurricane. The velocity field is not the hurricane, but a formal
description of the hurricane that we can obtain directly by planting a
grid of instruments in the hurricane's path. So strictly speaking, I
would not call the weather service's simulation a simulation of THE
hurricane, but rather a simulation of some abstract measurements we
might take of the hurricane. Also, the artificial hurricane I
suggested need not reproduce every single effect of the hurricane on
the real world, but only those that lead directly to sensory
experience of the observer. If the observer inconveniently wants to
walk around and poke through the wreckage, then we have to include
more of those effects. If the observer is very persistent, we have to
generate a full-blown artificial hurricane.

I don't see a sharp distinction between a "simulation" and "a machine
that produces a hurricane artificially," but rather that they lie on a
continuum. Can we agree that a physical system has no reality outside
the sensory experience it conveys to an observer? If so, then a
"simulation" is the action of some artificial device that reproduces
some or all of the sensory experience we associate with the "real"
thing. If the simulation leaves something out, then it is incomplete.
If it doesn't leave anything out, then the observer cannot tell it
apart from the "real" thing. From the observer's standpoint, it IS the
real thing.

Every simulation must effect some change in the real world, because
the observer exists in the real world and can only detect things in
the real world. Two of our most important senses--vision and
audition--respond only to energy fluxes from the real world. The other
senses respond to both energy and material fluxes (or perhaps I should
say, energy fluxes mediated by material fluxes). Perhaps the
distinction we are trying to draw is that "simulating X" delivers
strictly energy-mediated sensations, while "reproducing X
artificially" includes whatever material fluxes are necessary to
deliver the full range of sensations. But I don't see this as
being a particularly natural division. Since every simulation must
have some detectable real-world effect, what is the difference
between an energy-only effect and an energy+material effect? They
differ only in the complexity of the output devices required.

Dan Mocsny
dmocsny@uceng.uc.edu