Guy Hoelzer  wrote or quoted:
> in article cllqu1$1u0c$1{at}darwin.ediacara.org, Tim Tyler at tim{at}tt1lock.org
> > Guy Hoelzer  wrote or quoted:
> >> in article clc03g$24sv$1{at}darwin.ediacara.org, Tim Tyler at
tim{at}tt1lock.org
> >>> Guy Hoelzer  wrote or quoted:
> >>>> in article cl65so$b0p$1{at}darwin.ediacara.org,
Catherine Woodgold at

> >>>>> If you mean "maximizing, under the constraint of
> >>>>> following all the other physical laws" -- is
that really
> >>>>> any different from just plain "following all the other
> >>>>> physical laws"?  What exactly is your claim?
> >>>> 
> >>>> My claim is that this IS a physical law.  There is an
ongoing debate about
> >>>> whether this claim constitutes a fourth law of
thermodynamics, or whether
> >>>> it
> >>>> can be accommodated by a minor modification of the
way we articulate the
> >>>> second law.  I am in favor of the latter.
> >>> 
> >>> Several points here:
> >>> 
> >>> I wouldn't even describe the second law of thermodynamics
as a physical
> >>> law.  It's not a "law" - since it permits exceptions
> >> 
> >> Our traditional understanding of a static 2nd law explicitly
applies to to
> >> closed systems, and there are no exceptions permitted or
observed, AFAIK.
> > 
> > Violations of the second law are commonplace on small scales - e.g. see:
> > 
> > ``One of the most important principles of physics, that disorder, or
> >   entropy, always increases, has been shown to be untrue.
> > 
> >   This result has profound consequences for any chemical or physical
> >   process that occurs over short times and in small regions
> >  
> >   Scientists at the Australian National University (ANU) have carried out
> >   an experiment involving lasers and microscopic beads that disobeys the
> >   so-called Second Law of Thermodynamics [...]''
> 
> This is not inconsistent with my claim, because there cannot be such a thing
> as a truly closed system inside of the universe.  Closure can only be
> approximated at small scales.  In response to the interpretation of these
> empirical results I can only predict that the apparent failure of the 2nd
> law is due to either the cryptic openness of their system or a
> misunderstanding of what went on inside.  If this prediction is false, then
> so is my current paradigm.

Closure is no big deal - as with fluid dynamics, you can define a boundary
and measure entropy-flux through that boundary - if you are dealing with 
an analog of the second law in an open system.

There's no problem with the experiment.  The problem is with the second
law.  The second law expresses a statistical tendency - not an iron rule.
It's a rule that applies when the number of states in the system is large.
Nobody should have expected it to apply on small scales in the first 
place.

> >> So I do see it as a universal and physical law, albeit one that
> >> appropriately leads to statistical sorts of models. [...]
> > 
> > It's no more a physical law than evolution is.  Evolution and
> > the second law are *consquences* of the physical laws (and the
> > initial conditions) - but they are not themselevs necessary to
> > explain what happens in the world.  I.e. The physicist's "theory
> > of everything" would make no mention of either concept.
> 
> I expect otherwise.  Do you know of any instances where someone has tried,
> let alone succeeded, in deriving the second law from putatively more
> fundamental physical laws?  Would you agree that your view of the 2nd law as
> consequence is an unfounded (unproven? untested?) speculation at this point?

The second law is statistical.  It was derived from statistics (plus
some Newtonian physics) by Boltzmann:

``Toward the end of the nineteenth century, Ludwig Boltzmann showed that 
  that second law of thermodynamics is a statistical statement about the 
  behavior of particles. He proved that the molecules of a system tend to 
  approach their equilibrium distribution when started off away from 
  equilibrium. That equilibrium is characterized by a certain quantity H, 
  which is essentially negative entropy, approaching a minimum. In short, 
  Boltzmann basically derived the second law by assuming that matter was 
  composed of particulate bodies-atoms and molecules-and applying 
  Newtonian particle mechanics along with principles of statistics. 

 - http://www.csicop.org/sb/2002-09/reality-check.html

> >>> Care to say what you have in mind for a modification of
the second law?
> >> 
> >> I think that I've posted this before on sbe.  I would offer
the following
> >> conjecture as a universal physical law:  "Thermodynamics causes an
> >> exploration of paths (e.g., mechanisms, processes) affecting
the rate of
> >> entropy gain within closes systems (I suspect that the whole
universe is the
> >> only truly closed system), and favors those that maximize
this rate."
> >> Favoring these paths is equivalent to the structure of the
universe taking
> >> the path of least resistance as it "falls" toward
higher entropy levels.
> > 
> > In some respects, that seems weaker than the second law - in that it
> > doesn't explicitly say that entropy can't decrease.
> 
> The static second law is completely subsumed by the one I stated in today's
> universe due to the scale and particulate nature of the universe, and
> because it implies that the absence of bias favoring decreasing universal
> entropy. [...]

To "completely subsume" the second law - IMO - it would need rewording to 
explicitly state that entropy can't decrease.

> > I agree with the spirit of this sort of idea - though as we've
> > discussed, I have some issues about whether such maximisation
> > will necessarily happen in the short term - since organisms
> > can act to conserve resources in the short term under some
> > circumstances - as a squirrel burying a nut demonstrates.
> 
> To reiterate my previous response, if you think that this is a counter
> example to my argument, then you have not fully appreciated the argument.
> Everything that the squirrel does increases universal entropy.  The law I
> and many others are advocating as conjecture does not imply anything about
> those activities that do not occur, such as eating every nut as soon as
> possible.

In that case, it seems very unclear what it does imply.

The squirrel deliberately refrains from maximising entropy in the short 
term - something which it is evidently capable of doing.

To understand why I see no alternative to considering the
timescale over which the function being maximised is measured.
-- 
__________
 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
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