DNAunion: Another 2-parter in response to a post by David Bowman. This is
part 1 of 2.
>>>David Bowman: Regarding DNAunion's comments about his "Teeter-totter
Analogy":
It seems that you use the terms "overcome", "downhill", & "uphill" in a way
that has led to some unnecessary confusion. Apparently, you want to use the
terms to refer to particular *parts* of composite processes and *parts* of
composite interacting systems where you imagine excising the said parts from
of the interacting system at hand and imagine such parts as a separate
independent system which is no longer in interaction with the rest of the
interacting process.
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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.
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.
And of course the total (overall, combined, net) tendency has not violated,
refuted, defied, broken, or done away with gravity.
***************************
>>>David Bowman: And then you imagine the behavior of said parts to continue
to be the same as it was when the part with its partial contribution to the
composite process was acting in full interaction with the rest of the
previous integrated system.
********************
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.
********************
>>>David Bowman: If this continued behavior when the part and partial
process is isolated becomes non-spontaneous and thermodynamically unfavorable
under the new disconnected conditions, you dub it as "uphill" and say that
the full process of the integrated system is "overcoming" the 2nd law as this
subsystem's partial process is driven "uphill". Unfortunately, the
spontaneous behavior of such an excised and isolated piece of the interacting
system has little, if anything, to do with its behavior as part of the
integrated system.
*********************
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 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.
*********************
>>>David Bowman: *Of course* changing the system will change the observed
behavior. But I would not want to call the operation of the integrated
interacting system as "overcoming" the 2nd law, nor especially, would I want
to label the operation of the full process as "uphill".
***********************
DNAunion: Neither did I label the overall process uphill. Only individual
processes (such as raising the bag of sugar) were uphill. In fact, I stated
that an uphill process itself will not occur - yet I stated that the bag of
sugar was raised. Obviously, I was stating that the *overall* process was
downhill, even if I did not explicitly state such.
***********************
>>>David Bowman: The behavior of the isolated subsystem doesn't tell us
anything about the behavior of the integrated interacting system, and is
irrelevant to it. Each system with its own particular internal connections
to its parts and to its surroundings and their conditions has its *own* kind
of spontaneous "downhill" behavior.
The way I was using the terms was in reference to the *actual interacting
system* at hand since it is the behavior of *that* system that is relevant,
by definition or by tautology (i.e. the behavior of the interacting system is
what is relevant to the interacting system).
************************
DNAunion: I would add that the tendencies of the individual components of an
interacting system are also relevant to the whole.
************************
>>>David Bowman: When we focus on the fully integrated system at hand we see
that any process that happens in nature is thermodynamically favorable and is
"downhill", and its operation is just another example of the 2nd law working
normally.
*********************
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.
*********************
>>>David Bowman: It *doesn't matter* if the interacting system is a
complicated biological system or a cup of tea cooling off in a cooler room
(as far as any potential appeal to the 2nd law is concerned). If you take
the hot tea out of the cooler room and isolate it in a sealed
super-insulated dewar it behaves differently than when it is in strong
thermal contact with the air of the cold room. When it is in contact with
the cold air of the room the tea's entropy and temperature quickly falls as
it cools down to the ambient temperature, and some of this cooling is via
evaporation of water from the tea/air interface at the tea's top surface.
This changes the concentration of the tea as well as further decreasing the
entropy of the remaining tea. When the tea is isolated in the dewar from the
room's cold air, its entropy, mass, temperature, internal energy,
concentration, etc. remain fixed. 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. I would not say that the tea's "tendency
to disorder" is "overcome" by the process. 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. Its tendency is not the same in a dewar as in a cold
room, and neither of these is its tendency when it is in a room that is much
hotter than the tea, with air that is supersaturated with humidity. In the
latter case the tea's entropy and temperature and water concentration
*increases*.
********************
DNAunion: When I mentioned a hot cup of tea cooling I thought to myself, "I
bet David could write a whole chapter on the physics of this", and it looks
like I was right (I am sure David could have gone on further). I don't mean
this in any way as an insult: it is a compliment. To be able to look at a
hot cup of tea and find so much that the ordinary person couldn't hope to
grasp - to understand to some extent how the universe operates by examining a
simple cup of hot tea - this to me is truly amazing.
Now, as far as where you and I differ…
[quote]"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."[/quote]
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.
[quote]" I would not say that the tea's "tendency to disorder" is "overcome"
by the process.[/quote]
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.
[quote]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.[/quote]
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.
[quote]Its tendency is not the same in a dewar as in a cold room, and neither
of these is its tendency when it is in a room that is much hotter than the
tea, with air that is supersaturated with humidity. In the latter case the
tea's entropy and temperature and water concentration *increases*.[/quote]
Again, my original statement was about *hot* tea. This adjective itself
implies that the tea is hotter than its surroundings. This was made more
explicit when I added *cooling off*.
Again, I feel that David has bowled another strike, but not on the same lane
I am using.
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