Regarding:
>DNAunion: Yes. I feel it is legitimate to look at individual components of
>an aggregate system and determine their individual tendencies, isolated from
>the others.
What makes you think they necessarily even have such intrinsic
"tendencies" that are independent of the situation in which such a
component finds itself?
>In a two-part system, if (1) the primary tendency is in one direction (the
>bag of sugar tends to take up a position as physically close to the center of
>the Earth's mass as possible because of gravity) and (2) a second tendency is
>in the opposite direction, and (3) the second tendency "overpowers" (arg!
>another word choice I will probably have to defend) the primary one, then I
>feel it is legitimate to state that the primary tendency has been overcome.
It doesn't *have* a prior intrinsic "primary" tendency. If the bag of
sugar was placed (at relative rest) near the surface of the Moon or near
Jupiter its "tendency" is *not* to be "as physically close to the center
of the Earth's mass as possible". If the bag was placed in near Earth
orbit around the Earth it also doesn't have this "tendency". If the bag
is initially moving away from the Earth above the atmosphere at a speed
greater than 11 km/s then its "tendency" is to continue to increase its
distance from Earth forever. *If* the bag was to be placed on the
Earth's surface at rest relative to it, then it *would* have the
tendency you claim. But if it were placed on the end of a previously
balanced teeter-totter while another weight of greater than 10 lbs was
placed on the other end, then, again, its "tendency" would be different.
The bag's behavioral "tendency" is relative to the circumstances it finds
itself in.
...
>DNAunion: No, not their *behaviors*, but their *tendencies*. Behavior
>implies what objects actually do (which can and does change for objects in my
>analogy), while tendency implies what objects tend to do (which remains the
>same for an object in my analogy). In my see-saw analogy, the tendency of
>one of the object's influenced the behavior of the other, but it did not
>influence the actual tendency of the other.
The way I see it objects "tend" to behave the way they behave. It seems
to me that the concept of "tendency" is a probabilistic concept. We
imagine preparing a large ensemble of effectively identically prepared
systems, and suppose that there might be a plurality of possible
behaviors that might conceivably ensue for each ensemble member, where
chance might have a role in the objects' behaviors. If there is one
behavior that occurs with a predominate frequency for the ensemble, then
we say that that particular predominant behavior is the "tendency" of
an ensemble member object. If no particular behavior is predominant
then there is no net tendency. If only one behavior ever happens or can
happen because of an underlying determinism in the natural laws governing
the objects' behavior, then that one possible behavior is also the
"tendency". If changing the circumstances under which the ensemble
members find themselves results in changes in the predominately observed
behavior, then the "tendency" is a relative concept which is relative to
the particular relevant circumstances under which the object's find
themselves. This latter case is the usual case for physical objects.
>DNAunion: Note that changing the word *behavior* to *tendency* changes the
>preceding statement dramatically.
>
>"Unfortunately, the spontaneous *tendency* of such an excised and isolated
>piece of the interacting system has little, if anything, to do with its
>*tendency* as part of the integrated system."
I see, very little difference in meaning whether the word 'behavior' or
'tendency' is used. The main difference is that the word 'tendency'
suggests that more than one behavior may be conceivably possible under a
particular set of circumstances, but that a particular behavior is
predominantly probable, whereas the word 'behavior' only refers to the
actual behavior that is observed under the given circumstances. If the
underlying dynamics for the system is deterministic then the two words
have identical import since only one behavior is then possible for each
set of circumstances.
>I believe this word substitution turns David's original true statement into a
>false one. And as I explained above, in my analogy, I was not insisting that
>the individual component's *behaviors* remained constant when isolated, but
>that their *tendencies* did. I believe David has bowled a strike, just not
>on the same lane I am playing on.
What lane *are* you bowling on?
>DNAunion: Agreed - I have not stated otherwise. But still, the individual
>coupled reactions in an interacting system can be uphill or downhill, and
>each one's tendency influences the overall tendency of the aggregate system.
>It is impossible for the individual uphill reactions/processes to occur,
>unless they are coupled in some manner to downhill reactions/processes or
>equal or greater magnitude. But then it is not the original process under
>consideration - our focus has expanded to include accessory
>structures/processes.
My point is that the particular arrangement of "assessory" circumstances,
structures, couplings, interactions, and processes between a given
subsystem with its external environment determine (or at least strongly
influence) just what the subsystem's tendency (and hence expected
behavior) actually happens to be.
>DB>I would say that the cooling tea in the cooler room is an example of
>a thermodynamically "downhill" process even though the tea's entropy
>decreases.
>
>DNAunion:
>Yes, it is downhill; and yes, the tea's entropy does decrease.; but… The
>entropy of the surroundings increases, thereby compensating for any decrease
>in entropy of the tea itself. For a hot cup of tea which is cooling (my
>original example), that tendency is for the tea to dissipate heat into the
>surroundings thereby increasing the molecular randomness of said surroundings.
>
>DB>I would not say that the tea's "tendency to disorder" is "overcome"
>by the process.
>
>DNAunion:
>Okay, but your system is not composed of two interacting components - *at
>least not in the sense that my teeter-totter analogy was*. You have only one
>object of interest (the tea) and only one tendency in one direction (for the
>tea to dissipate its heat into its cooler surroundings in accord with the
>second law). Under these circumstances, I would claim there was any
>overcoming either.
Wait a minute. You seem to have suddenly changed your story. The system
*is* composed of two interacting components. There is the tea, and there
is the cooler surroundings. There is a thermal coupling between them
that results in a spontaneous *decrease* in the tea's entropy. I was
under the impression that you had used the term "disorder" to be what the
entropy measured. Thus, the entropy decrease measures an decrease in the
tea's disorder (according to your use of the term "disorder"). *You* were
the one who was talking about things having an intrinsic "tendency toward
disorder". *You* were the one who wanted to look at the individual
subsystem to decide the subsystem's intrinsic "tendency". Now all of a
sudden, for some reason, it seems you agree with me in looking at the
composite subsystem of the tea and its cooler surroundings with which it
interacts, and agree with me that this does *not* represent an
"overcoming" of the tea's prior "tendency" (that you wished to claim
remained fixed independent of the subsystem's circumstances). Recall your
quote above: "I was not insisting that the individual component's
*behaviors* remained constant when isolated, but that their *tendencies*
did." Which way do you want it? Just which side of this discussion are
you arguing?
DB>The tea doesn't even *have* any specifically defined tendency at all
>until the rest of the system with which it interacts is properly
>specified.
>
>DNAunion:
>As you stated it here ("the tea"), you are correct: there is no
>specifically-defined tendency. As I stated it originally ("hot cup of tea
>cooling off"), then there is a specifically-defined tendency.
Yes, and the tendency, in this case is for the tea to *decrease* its
entropy. How does this fit with your earlier claims about such
decreases in "disorder" being an "overcoming" of the "tendency" of the
system toward "disorder" where this "tendency" is supposedly determined a
toward "disorder" where this "tendency" is supposedly determined a priori
by the 2nd law?
David Bowman
David_Bowman@georgetowncollege.edu
This archive was generated by hypermail 2b29 : Mon Nov 13 2000 - 00:12:28 EST