🚀 go-pugleaf

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

My car is in a certain view in steady state.  But certainly
not in equilibrium.  My car is only in equilibrium if it
has become a pile of rust.

> 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).

Actually I fail to see the distinction between one living
organism and a whole bunch of them pinned on a lump of stone
and iron... what makes one system be in "dynamic equilibrium"
and the other not ?  
Electrons, protons, neutrons, photons, where do you make
the distinction ?
> 
> 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.

But from a point of view of entropy this is NOT right.
The outgoing infrared radiation has a much higher entropy
content than the incoming visible radiation per unit
of energy.  So influx and outflux are NOT equivalent.
> 
> 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.


Well, I would like to know what you define as "dynamic" equilibrium.
I know of only one kind of "equilibrium".  The thing you describe
is "steady state".


In order to distinguish between a steady-state situation and
equilibrium, you have to include everything that can have any
influence (like the sun) and enclose the whole lot in a box.
(ok, it may be an imaginary box :-)
If -in principle- the situation can stay for ever the way it
is, it is - possibly - an equilibrium.  If not, it certainly
isn't an equilibrium.


cheers,
Patrick.