🚀 go-pugleaf

Patrick Van Esch wrote:
> 
> Fred McGalliard wrote:
> >
> > Be careful. If you draw your circle around a community of organisims,
> > rather than just an individual, your subject may certainly be in
> > equilibrium. The current dynamic equilibrium is supported by the steady
> > input of solar power, and is remarkably stable over all.
> 
> That is not right.  In the same way you could say
> that my car is in equilibrium when driving 100 km/h
> as long as I can tank enough petrol.
> 
> Of course it is right if you redefine the word equilibrium.
> But then everything is in equilibrium, for a suitable redefinition
> of the word.

No. He was speaking about *dynamic* equilibrium; and your car
example is another case of dynamic equilibrium.

In a dynamic equilibrium, incoming and outgoing flows of extensive
parameters (like energy, matter) are equal.

In the example Fred was dealing with - life - the initial question
was about dynamic equilibrum in the circulation of chemicals
(for a human, incoming and outgoing chemicals are not the same;
but for the whole system of life it is).

He added that there is also a dynamical equilibrium in the energy
domain: the Earth radiates in the end the same amount of energy
than what it received from the Sun.

He added that because this is what keeps the whole circulation
upright: the low-entropy radiation from the Sun is "used" by
life to sustain and build order and is radiated away in the end
as high-entropy radiation; just as you wrote:
 
> Life lives on entropy increase.  A system that causes an increase
> in entropy cannot - by definition - be in equilibrium, for equilibrium
> only occurs at a state of maximum entropy.

That's called *thermal* equilibrium.


Bye

 Daneel [#323]    (ustokos@cs.elte.hu)   
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