>>>David Bowman: 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.
>>>David Bowman: 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 not claim there was any
overcoming either.
>>>David Bowman: 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.
***********************
DNAunion: No I didn't. You missed my qualifying statement even though I
emphasized it with asterisks.
"Okay, but your system is not composed of two interacting components - *at
least not in the sense that my teeter-totter analogy was*"
In my teeter-totter analogy, the objects were those placed in the baskets and
the tendencies were those that each item in a particular basket had for
taking up a position as close to the center of Earth's mass as possible.
Each basketed-item counted as 1 object with 1 tendency. Likewise, a hot cup
of tea cooling off is 1 object with 1 tendency. That is keeping it in line
with my analogy, as I stated.
Even if you want to get technical - leave the point of my analgoy - and argue
that the tea is actually two interacting systems, as you did in your post,
then we would have to be just as technical with the see-saw analogy and count
the bag of sugar and the medium it interacts with as two interacting systems.
As you yourself pointed out, as a bag of sugar falls towards the ground, it
displaces air which flows around the bag and ends up in a higher position
than originally: as the bag moves downward, a net upward movement of
displaced material (air) occurs. Yet I did not consider this to be
overcoming: only when a second item (snowballs) was introduced and its
tendency countered that of the original item (bag of sugar) did I mention
overcoming. So even being technical (which misses the point of an analogy),
my statement about your cup of tea example not being parallel to my analogy
of overcoming stands up.
*****************
>>David Bowman: 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".
********************
DNAunion: Yes, and in discussions a hot cup of tea cooling is a single
object/system with a single tendency, just as a bag of sugar falling is a
single item with a single tendency (the technicalities of taking into
consideration the net upward displacement of air is overlooked). That is the
sense in which I have using terms.
********************
>>>David Bowman: 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?
*****************
DNAunion: The same way as I always did.
*****************
>>>David Bowman: Just which side of this discussion are you arguing?
*****************
DNAunion: Mine, of course, which has not changed.
*****************
>>>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.
>>>David Bowman: 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?
*******************
DNAunion: I have maintained that a local decrease in entropy is possible if
accompanied by an equal or greater increase in disorder elswhere. This is
exactly what occurs when hot tea cools off.
I have not used the word overcome in reference to hot tea cooling off - that
is your version of my statements.
*******************
DNAunion: Can't finish or recheck my "work". AOL will kick me off in 1
minute.
This archive was generated by hypermail 2b29 : Mon Nov 20 2000 - 12:38:51 EST