Path: utzoo!attcan!uunet!wuarchive!mit-eddie!media-lab!minsky
From: minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky)
Newsgroups: comp.ai.philosophy
Subject: Re: emergent properties
Message-ID: <3841@media-lab.MEDIA.MIT.EDU>
Date: 27 Oct 90 04:59:30 GMT
References: <1990Sep29.213139.2876@watdragon.waterloo.edu> <3499@media-lab.MEDIA.MIT.EDU> <1990Oct26.220658.11281@ncsuvx.ncsu.edu>
Reply-To: minsky@media-lab.media.mit.edu (Marvin Minsky)
Organization: MIT Media Lab, Cambridge MA
Lines: 29

In article <1990Oct26.220658.11281@ncsuvx.ncsu.edu> fostel@eos.ncsu.edu (Gary Fostel) writes:
>
>I was discussing the idea of emergence with a physicist recently and 
>something he said rings very true with this view of emergence.  He suggested
>that gravity might be considered an emergent property of collections of
>elementary particles.  In fact the "inexplicable emergent" property
>of gravity and the effort to make it more explicable has been a dominant
>influence on the direction of 20th century physics. 
>

Well, at least to first order -- that is, in Newtonian physics --
gravity is a simple property of single particles; a simple
inverse-square attractive force.  So there is nothing new when you
have larger collections of particles - elementary or otherwise.  We
usually use the term "irreducible" for such phenomena, rather than
"emergent" because nothing new happens (once we have the superposition
theory) with larger collections of particles.

To be sure, the gravitic phenomena in general relativity do not add in
such a linear fashion, but (as I understand the situation, which is
not very deeply) there is no reason to suppose any permanent mystery
once the correct field equations are found.  I'm not saying that
gravity is understood, only that there is no reason to think that
basically new phenomena arise with large collections of particles.

In Eddington-style "fundamental theories", the gravitational constant
is indeed a function of the total number of particles in the universe.
(These theories have not stood the "test of time", for what that's
worth.)  So you might consider that an "emergent", of a particularly
uniform and "simple" kind.