Re: System boundary

On Jun 6, 5:08 am, Haines Brown <bro...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
PD <TheDraperFam...@xxxxxxxxx> writes:
On Jun 5, 12:01 pm, Haines Brown <bro...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
I'm trying to grasp the broader ontological implications of a
system boundary as described in physics.

There are no ontological implications. It is a definition, associating
a connotation to a word, and therefore it may have semantic
implications. Not ontological ones, though.
2. The boundary is a structure (material or forcefield), that allows
matter or energy having certain characteristics to pass or be
blocked in the passage from the system to its environment.

Nope. This is plain wrong. It is a mental dotted line, that's it.
Nothing complicated or even ontological about it.

No, I'll stick with "ontological". The reason is simple, in that I
don't adopt a postmodern view that all statements necessarily lack
truth value. Most physicists are not postmodern, and they assume that
a boundary (wall, membrane, mediation), has some objective reality. It
is not a very helpful critique of a set of propositions to argue that
everything is fiction and so there's no point in having offered them
in the first place.

How can I justify the proposition? I suppose by referring to an
authority. For example that old classic, Foundations of Physics by
Robert Linsay and Henry Margenau (1938). In Section 1.9, they
discusses specific and general boundary conditions at length. While
the description of a system state engages a subjective element (such
as specifying the space-time frame so that the system becomes
measurable), the authors assume there is nevertheless a truth value
in that description; boundaries are real. "... specific boundary
conditions are customarily in physical texts referred to as 'initial'
conditions ..."

Nowadays we are less fixated than the authors on closed systems. For
example, Prigogine's open systems remain systems because they are
distinguished from their environment by their maintenance of a
far-from-equilibrium state. Such a system is obviously not merely the
effect of our subjective viewpoint. I happen to be such a system and I
well know that I exist as a living organism.

This is not the place to discuss the merits and demerits of
postmodernism, but I believe that because it represents a view not
widely shared in the scientific community (unlike the political
community these days), it must be accompanied with some justification
before it can be used to dismiss the common-sense view that our
statements about things are nothing more than fictions.

3. The minimalist functional definition of such a boundary is that it
limits the system's degrees of freedom/phase-space.

This is also wrong. A system can have unrestricted degrees of freedom
and still have a mental dotted line around it.

Of course. Since you reduce boundary to a fiction, it has no effect on
the system.

Again, quoting the text cited above: "... we see the significance of
general boundary conditions: they impose fundamental restrictions on
the type of activity possible for the system considered" (pg. 53).

Clearly, the authors differ with you here. That does not mean they are
right and you wrong, but only that if you choose to differ with a
convention or authority, you need some justification for doing so.

4. This phase-space is a description of all possible system
states, and it can either be inferred from multiple observations
of system outcomes, or it can be represented as being real
potencies present in the system. Representing the boundary as
limiting phase-space implies that this distribution of possible
outcomes is being acted upon and therefore these are real
unobservable potencies that exist independently of our
observations.

Well, since both 2 and 3 are wrong, it is plain that 4, 5, 6, and 7
(which follow from 2 and 3) are also wrong.

I did not say I was offering a set of mutually dependent syllogisms,
but merely independent propositions. Except for the reality of systems
posited in #1, each hopefully stood on its own. Admittedly, item 4
(presuming scientific realism) and 5 (presuming probabilistic
causality) adopt minority views, but these positions are taken
seriously these days. Other than that, as I state in the line you
quote at the beginning, I was merely trying to explicate
the convention, not arguing a case of my own.

--

Haines Brown, KB1GRM

Well, your babble-generator certainly starts easily with a light pull,
doesn't it? You've read too much and learned too little. It might be
useful to talk with a *physicist* to understand the difference between
a system boundary and where a boundary condition applies. Those are
two different contexts that are sometimes but not often connected.

PD

PD

.