Re: Lizard engines and rat engines

Perplexed in Peoria <jimmenegay@xxxxxxxxxxxxx> wrote or quoted:
> "Tim Tyler" <tim@xxxxxxxxxxx> wrote in message news:db2792$2a5b$1@xxxxxxxxxxxxxxxxxxxxxx

[thermodynamics]

> > There are some more candidate laws on the horizon, though their
> > outlines are perhaps less distinct.
> >
> > Assuming for the moment, that we wind up with two more "laws" -
> > roughly along those lines. Should they be "marketed" as laws
> > four and five?
>
> We already have two more "laws" that are fairly fundamental.
> Onsager's reciprocity relationship and Prigogine's law of
> minimum entropy production. Both apply to the "linear" regime
> close to equilibrium. Neither has been marketed as a fourth
> law of thermodynamics. But their logical status is similar
> to that of the second law. They can be derived using statistical
> arguments from more fundamental laws of physics. Onsager's
> reciprocity law, for example, is a consequence of the time-reversal
> invariance of fundamental physics and the principle of detailed
> balance.
>
> Coming up with new "laws" that apply to situations far from
> equilibrium - especially if they are supposed to apply to ALL
> situations far from equilibrium - strikes me as very difficult.

I'm not sure if we'll make good progress on the "all situations"
case either. However, IMO, attempts to characterise the thermodynamic
behaviour of far-from-equilibrium systems are important.

Such complex systems are ubiquitous. Meteorologists, engineers and
biologists all need the results.

How difficult the project is probably depends on how far we get into it.

Even the basic assertion the "dissipative structures tend to dissipate
energy" still seems to be being discussed here as though it is
contraversial :-(

That seems like the very first thing to more firmly pin down and
characterise. However, there are lots of more advanced projects
bearing on the subject of a thermodynamic characterisation of
far-from-equilbrium systems:

Is the rate of production of disorder related to the extent of the
order generated? Are there limits to the rate with which dissipative
structures can dissipate entropy? Is burning fast wasteful? What's
the relationship between the rate of dissipation of entropy, and the
efficiency with which the resulting energy is used? Can systems develop
the ability to conserve resources? Can the maximum entropy production
principles make useful predictions about the form dissipative structures
take? Are there more classes of dissipative structure waiting to be
discovered? If so, where do we look for them? What can be done to
*stop* dissipative structures dissipating available resources, in order
to preserve them? How long to dissipative structures take to burn out?
What useful statements about the final stable state be made from the
initial (unstable) conditions - without performing an exhaustive
simulation? Are there minimum gradients which the various dissipative
structures can work off? And so on.

> Perhaps we can at least come up with a better characterization
> of some special far-from-equilibrium situations - phase transitions,
> say, or dynamic steady states.

>>From my point of view, those things already have reasonable thermodynamic
charaterisations.

IMO, it's the case of dissipative structures where there's still
a substantial hole in our thermodynamic knowledge.
--
__________
|im |yler http://timtyler.org/ tim@xxxxxxxxxxx Remove lock to reply.

.

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