Re: Understanding MinEP and MaxEP

Tim Tyler <tim@xxxxxxxxxxx> wrote in
news:dfrcf7$12h0$1@xxxxxxxxxxxxxxxxxxx:

> William Morse <wdmorse@xxxxxxxxxxxx> wrote or quoted:
>
>> The point of self organization is that the organization outcompetes
>> the disorganized states by utilizing part of the available energy
>> gradient to create a structure. This only makes sense if the
>> resulting structure can process energy faster than the disorganized
>> states. But "processing energy" is not the same as "producing
>> entropy" - the processed energy can go into work (e.g. into
>> maintaining the structure) as well as into entropy.
>
> My current take on this is that I've discarded the idea that entropy
> is being maximised. Power isn't really being maximised either.
>
> ISTM that there's more than one mechanism invovled producing the
> effects under discussion - but an important one - and the one most
> obviously involved in biological systems - is driven by selective
> competition between self-perpetuating systems. These systems behave
> as though their main aim is to maximise their "staying power" by
> feeding off the available energy gradients. The winner isn't *always*
> the one that can use the resorces most rapidly - but that is often a
> big factor in the end.
>
> In practice, the effect is *pretty* close to maximising power (i.e.
> rate of work). Essentially the closeness is because the kind of
> technological breakthroughs that allow better staying power to be
> achieved with a reduced rate of work are rather rare.
>
>> There is obviously a change in potential energy between the water in
>> the upper bottle and the water in the lower bottle, but what is the
>> change in entropy? To make this even more clear, let us say that the
>> bottles are perfectly insulated, and that the air in the bottles is
>> completely saturated with water vapor before we start the experiment.
>> After the water has flowed from the upper to the lower bottle, there
>> is a difference in potential energy, so presumably the water in the
>> lower bottle has higher kinetic energy, i.e. it is hotter. But where
>> is the entropy difference?
>
> The water being hotter represents an entropy difference.

I don't think so, but I will be happy to be corrected by an authority.

> Heat is a highly disordered form of kinetic energy.

True, but irrelevant regarding an entropy difference. Heat engines are
the stuff of thermodynamics.


> Forgive me if I don't discuss the bottle example further. With
> no convenient way of measuring the entropy of the water on exit
> from the top bottle - or the work it has done - the example seems
> to me to be relatively unenlightening.

Actually, I think the example would be quite enlightening if we could
understand it. What I don't know is whether the lack of understanding has
to do with the lack of knowledge among those of us discussing it or with
more fundamental complexities of fluid mechanics, which I have mentioned
earlier.

Yours,

Bill Morse

.

Relevant Pages

  • Re: Understanding MinEP and MaxEP
    ... > can process energy faster than the disorganized states. ... My current take on this is that I've discarded the idea that entropy is ... > There is obviously a change in potential energy between the water in the ... > upper bottle and the water in the lower bottle, ...
    (sci.bio.evolution)
  • Re: Understanding MinEP and MaxEP
    ... >>> rate at which you have to pour water in at the top increases. ... > My bottle example is a *real* example. ... > of a discontinuity in the drain rate. ... thought was maximized was not rate of entropy production but rate of ...
    (sci.bio.evolution)
  • Re: Understanding MinEP and MaxEP
    ... >>> the upper bottle and the water in the lower bottle, ... >>> is a difference in potential energy, so presumably the water in the ... >>> is the entropy difference? ...
    (sci.bio.evolution)
  • Re: Entropy confusion, please help!
    ... entropy will always ... | ordered" form, liquid water a a more random form, and steam the most ... Heat is really the motion of the molecules and will spread randomly, ... so that fast molecules will transfer that energy to slow molecules ...
    (sci.physics)
  • Re: Gasoline vs. battery
    ... Entropy invites the idea that changing H2O to HHO should ... HHO is just a simpler form of water. ... In short, two water molecules, with the addition of energy to break the bonds ... will form two molecules of hydrogen gas and one molecule of oxygen gas. ...
    (sci.chem.electrochem.battery)