From: jpasini@cipres.cec.uchile.cl (Pasini Krug Jose Miguel)
Subject: Re: Science and choice
Summary: predictability and determinism are just similar... 
Originator: jpasini@araucaria
Date: Wed, 23 Dec 1992 05:06:12 GMT
Distribution: world, public
Organization: Centro de Computacion (CEC), Universidad de Chile
Keywords: chaos science determinism 

In article <1992Dec21.103136.19425@jcnpc.cmhnet.org> mam@jcnpc.cmhnet.org (Mike A. McAngus) writes:
>Shawn Green (greens@mentor.cc.purdue.edu) wrote:
>: In article <1992Dec16.030334.20463@nmsu.edu> epowers@spock.NMSU.Edu (POWERS)
>writes:
>:   [stuff about science implying determinism deleted]
>:
>: >  So you must "choose":  either you must base an important part of your
>: >philosophy on science and deny free will, or you'll have to find something
>: >outside of science to base it on.
>:
>: I will quickly admit that I am way out of my depth here, so maybe someone who
>: knows something can help me out.  Doesn't chaos theory say that not every
>: event could be predicted even if you had perfect knowledge of everything that
>: was happening in the universe at that moment in time?  If this is true, scien
>ce
>: would not necessitate a deterministic philosophy.
>:
>: Comments/corrections from any net.physics-types?
>:
>:
>: Shawn Green
>: greens@mentor.cc.purdue.edu
>
>Thanks, I was going to ask this question if noone else did.

	First of all, there's a little problem here: what chaos theory says is that
even if you do have perfect knowledge of all the factors in play, you won't be
able to PREDICT what will happen next. This doesn't mean that the universe is
not DETERMINISTIC. The universe is deterministic in the sense that, if you
"put" the universe in the same "initial conditions" then it will behave in the
same way. Deterministic philosophy should be called, IMHO, predictability
philosophy. This sounds a little weird at first but, if you can, read one of
the first chaos articles wich appeared in "Monthly Weather Review", by a guy
called Lorenz. It is called "Deterministic non-periodic flow", and tells us
about how he devised a set of IFS (iterated function systems) that could
simulate the reports of a weather station by "creating" the weather conditions
by the use of these equations. At first he used a set of equations for the IFS
to "create the weather", but had the problem that the program reached
equilibrium after a number of "days"; this means that the program created the
same conditions (or at least very similar) every day. This, due to everyday
experience, is evidently false, so he started working on a new set of
equations that would create a never-repeating pattern for his illusory weather.
After some time he could devise a set of twelve equations that would serve 
his purpose. The important point is that this set of equations had a non-linear
element introduced into some of them.
	With this new set he saw that his weather creator created data that never
repeated itself nor reached equilibrium. He also observed (by a casualty) that
if he changed a little his initial conditions (the data for starting the pro-
gram), no matter how small the change, the results were very different from
each other. This means that these systems have a "sensitive dependency on the
initial conditions".
	Another thing to notice is that chaos is not something purely physical: its
"substance" is *mainly* mathematical. The fact that physics rely heavily on
mathematics is closely related to the appearance of chaos in nature, for when
you put down to equations *many* physical phenomena, the non-linear elements
already mentioned appear in these, not letting the solution of these be
explicit, and thus not letting you predict the state of the system in any future
moment without the use of numerical methods, which imply some error, as little
as it may be.
	I hope this cleared the picture up a little for you guys, and if out there
is anyone who really dominates the subject, please be kind to me.
	Also, I'm conscious that everything I said above excluded quantum mechanics
completely, so if there's someone who knows more on the subject and thinks I'm
talking nonsense, please be kind and clear things up for me a little via 
e-mail, so as not to do it again, ok? ;)

					Dagan.

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