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Re: Real world



The falling newspaper example, given by Emilio (see below), in my view, is
an illustration of something else than complexity. It shows how things are
not predictable because conditions (initial and otherwise) are not
reproducible. The same piece of paper, in form of a parachute (or as a
crupled wad), would likly to be found in nearly the same place after each
fall. Complexity has to do with difficulties we encounter in modeling
something mathematically. What is gained by confusing it with the
"sensitivity to randomness"? Both concepts refer to barriers on the path
of predicting what might happen but they are quite different. In the first
case we have to think better, in the second we have to be more careful in
controlling the environment, when we can.
Ludwik Kowalski

Date: Thu, 06 Nov 1997 12:58:24 -0500 (EST)
From: "Emilio O. Roxin" <EROXIN@URIACC.URI.EDU>
Subject: Real World

Hi!
This is a suggestion of a new thread to talk about. The subject
is the fact that real phenomena are, practically always, extremely
complicated and not quite suitable for exact study. It is by
disregarding a lot of details (correctly chosen by a good intuition)
that a productive analysis is possible.
As an introduction to this state of affairs I will pose a (funny)
Challenge: I will perform a sinple tast{ and challenge that none of
you will be able to repeat it. The task is the following:
I will take a piece of paper (say, a page of newspaper) and throw
it, standing straight up, into the air. The paper will fall to the
floor at some place and in some position, which we should determine
precisely (taking, for example, a photo). I challenge that nobody can
throw the paper so as to fall again on the same place and in the same
position, exactly. Emilio