On Thu, Feb 02, 2012 at 07:45:53PM +0100, Evgenii Rudnyi wrote:
> On 01.02.2012 21:51 Stephen P. King said the following:
> >On 2/1/2012 3:10 PM, Evgenii Rudnyi wrote:
> >>First the thermodynamic entropy is not context depended. This must
> >> mean that if it is the same as information, then the latter must
> >>not be context dependent as well. Could you please give me an
> >>example of a physical property that is context dependent?
> >>
> >
> >Temperature is context dependent. If we consider physics at the level
> >of atoms there is no such a quantity as temperature. Additionally,
> >thermodynamic entropy does require Boltzmann's constant to be defined
> > with is a form of context dependency as it specifies the level at
> >which we are to take micro-states as macroscopically
> >indistinguishable.
> The Boltzmann's constant, as far as I understand, is defined
> uniquely. If you talk about some other universe (or Platonia) where
> one could imagine something else, then it could be. Yet, in the
> world that we know according to empirical scientific studies, the
> Boltmann's constant is a fundamental constant. Hence I do not
> understand you in this respect.

Boltzmann's constant is a unit conversion constant like c an Plank's
constant, nothing more. It has no fundamental significance.

> Indeed, temperature is not available directly at the level of
> particles obeying classical or quantum laws. However for example it
> could be not a problem with the temperature but rather with the
> description at the particle level.
> Anyway, I would suggest to stick to empirical scientific knowledge
> that we have. Then I do not understand what do you mean that
> temperature is context dependent either.

Temperature is an averaged quantity, so whilst technically an example
of emergence, it is the weakest form of emergence.

Evgenii is stating an oft-repeated meme that entropy is not

It is context dependent because it (possibly implicitly) depends on
what we mean by a thermodynamic state. In thermodynamics, we usually
mean a state defined by temperature, pressure, volume, number of
particles, and so on. The "and so on" is the context dependent
part. There are actually an enormous number of possible independent
thermodyamic variables that may be relevant in different
situations. In an electrical device, the arrangement of charges might
be another such thermodynamic variable.

Also, even in classic "schoolbook" thermodynamics, not all of
temperature, pressue, volume and particle number are
relevant. Dropping various of these terms leads to different ensembles
(microcanonical, canonical and grand canonical).

Of course, context dependence does not mean subjective. If two
observers agree on the context, the entropy is quite objective. But it
is a little more complex than something like mass or length.

This is explained very well in Denbigh & Denbigh.


Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au

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