🚀 go-pugleaf

Pentcho Valev wrote on Sat, 25 Oct 2008 00:27:59 -0700:

> On Oct 24, 9:08 pm, "Juan R." González-Álvarez
> <juanREM...@canonicalscience.com> wrote:
>> This is one of the more difficult topics for students of thermodynamics
>> due to the generalized confusion and lack of rigor of standard
>> textbooks.
>>
>> Entropy is usually identified with 'disorder', observer 'ignorance',
>> and other non-physical stuff. Moreover, several the interpretations of
>> entropy and irreversibility are based in incorrect application of
>> equations and concepts.
>>
>> Physicists as Murray Gell-Mann think that entropy is a measure of our
>> ignorance about the microscopic state of a system (that is not right)
>> and conclude that any observer with full access to micro-state
>> information will obtain zero entropy (that again is unfounded).
>>
>> He goes further in his 'analysis' and conclude that variation of
>> entropy for any real process (zero lost of information) is exactly
>> zero. As conclusion irreversible processes are, he says, an illusion.
>>
>> Well, the truth is that people pass away with independence of our
>> observations. Irreversible phenomena is real.
>>
>> I have tried to provide a more general and rigorous point of view about
>> the physical interpretation of entropy in
>>
>> http://canonicalscience.blogspot.com/2008/10/physical-meaning-of-
entropy.html
>>
>> http://www.canonicalscience.org/en/miscellaneouszone/guidelines.html
> 
> I suggest anyone dealing with this topic should first analyse very
> carefully the genesis of the concept of entropy nicely described in Jos
> Uffink's paper "Bluff your way in the second law of thermodynamics".

Thanks by suggestion but Uffink's paper, which I already knew, reflects 
his misunderstandings on theory of heat.

The author also shows his confusion on the relations between time-
asymmetry and irreversibility.

In fact, the author seems unable even to define reversible processes. He 
attempts several outdated definitions as

(\blockquote
 First, one can understand ‘reversible processes’ as processes which  
 proceed so slowly that the system always remains close to equilibrium.
)

and

(\blockquote
 The second meaning of ‘reversible’ is the notion of a process whose 
 initial state can be completely restored by some other process, using 
 any auxiliary device available in our world.
)

Instead just using modern axiomatic definition. A process is reversible 
when its production of entropy is zero.

Uffink recognizes is an ignorant of modern thermodynamic theories:

(\blockquote
 Such extensions, sometimes called ‘thermodynamics of irreversible 
 processes’, would be able to describe the approach to equilibrium, as 
 illustrated by the heat equation; see, e.g., de Groot (1945); Prigogine 
 (1955). Here, a more interesting connection with the arrow of time could 
 result. This work seems to have resulted in a large number schools, and 
 I can therefore say little about it. 
)

As contrast, Prigogine monograph is used as main reference in my blog 
article.

The author also shows his misconception of other branches of physics when 
writes

(\blockquote
 After all, Hamiltonian mechanics also allows the existence
 of irreversible processes, for example, the motion of a free particle in 
 an otherwise empty universe.
)

This is plain wrong. The motion of a free particle is a reversible 
process, because the production of entropy is zero. Mechanics is a 
reversible theory where the equations of motion (Newton, Schrödinger) are 
time-symmetric.

> Just an illustration of the claims made in the paper:
> 
> http://philsci-archive.pitt.edu/archive/00000313/ Jos Uffink: "The
> historian of science and mathematician Truesdell made a detailed study
> of the historical development of thermodynamics in the period 1822-1854.
> He characterises the theory, even in its present state, as 'a dismal
> swamp of obscurity' (1980, p. 6) and 'a prime example to show that
> physicists are not exempt from the madness of crowds' (ibid. p. 8)
> ...Clausius' verbal statement of the second law makes no sense...All

Right, Clausius ***verbal*** statements are difficult to accept. But they 
can be written in concise and rigorous ***mathematical*** form

d_iS >= 0

It is worth to remark that the own Truesdell accepts the *validity* of 
the Second law and in latter years he formulates a similar inequality (he 
names the "Clausius/Duhem inequality" for the total entropy) in his own 
thermodynamic theory

http://www.amazon.com/Rational-Thermodynamics-C-Truesdell/dp/0387908749


-- 
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