Re: [Fis] Szilard's Engine and Information

Shu-Kun said:
>Regarding the related entropy of mixing (Delta S), it is certain that >the
>entropy of mixing is an information theoretical entropy >because there is
>no heat involved. It should not be taken as a typical >thermodynamic
>entropy (Delta S). Mixing of two chiral molecules >gas R and gas L you
>mentioned cannot be a thermal process. Therefore, >it is not a
>thermodynamic process in an heat engine. Mixing of R >and L cannot be used
>to generate mechanical work. This is a fact. >When we discuss the engine
>and related possibility of energy >conservation, this fact must be kept in
>mind. > >If the mixing of gas R and gas L would create work (a kind of
>mechanical >energy calculated as distance times force), one should be able
>to also create >mechanical work by mixing red color and black color.

to which I replied:
     SS: I find this interesting in regard to the understanding of
physical entropy as disorder. This interpretation has been disputed because
of examples like mixtures of oil and water, which seem to spontaneously
separate, making a more orderly result than was present in the mixed state.
But Shu-Kun's posting here suggests why this understanding is specious.
What is neglected in this view is that energy-utilizing work had to be done
to mix the oil and water to begin with, in a thermal process. This process
set up a curious kind of dispersed energy gradient, which then dissipated,
producing the separation, and giving off heat again. That is to say, the
unmixing of oil and water is a kind of work (not unlike the unwinding of
many wound up rubber bands!), and, as such, would not be expected to
produce disorder. Put another way, the unmixing of oil and water is NOT
SPONTANEOUS, but is instead a massive amount of microscopic work.

then Victoras said:
> How would behave a mixture of oil and water if Earth's field of
>gravitation was absent - would it mix or separate ? Can this be described
>by a conditional sentence like the one below ? if (gravity
>present){separation} else {mixing} Then it seems like an algorithmic
>process where entropy produces opposite results given different initial
>conditions. Thousands, millions, mirriads of similar conditional branches
>take place every moment everywhere in the Universe. Thence everything can
>be described/modelled as causal chains of events. That's how our
>(natural) and artificial inteligence (rule based or case
>(experience) based reasoning) work. Just interesting parralels...

to which Shu-Kun replied: They would separate.

     SS: So, Victoras sees the energy gradient being used to power the work
of separating oil and water as being gravitational energy, while Shu-Kun
implies that it is instead some kind of chemical gradient. Either way my
point is not being disputed. Therefore, even though the energy gradient
dissipation view of entropy production is historically prior, and
empirically measurable, the increasing disorder view is not falsified by
this oil/water example in the way that some folks thought it was.

STAN

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Received on Fri Apr 16 20:10:35 2004