Re: Genealogical Momentum

From: Guy Hoelzer (hoelzer_at_unr.edu)
Date: 03/14/05 

Date: Mon, 14 Mar 2005 17:02:06 -0500 (EST)

in article d0v8ns$2lpq$1@darwin.ediacara.org, Tim Tyler at tim@tt1lock.org
wrote on 3/12/05 9:26 AM:

> Guy Hoelzer <hoelzer@unr.edu> wrote or quoted:
>> in article d0shbh$1o73$1@darwin.ediacara.org, Tim Tyler at tim@tt1lock.org
>>> Guy Hoelzer <hoelzer@unr.edu> wrote or quoted:
>
>>>> BTW, if you want an example of equations that are not reversible take a
>>>> look
>>>> at reaction diffusion equations, which I think were originally created by
>>>> Alan Turing. You can also have a look at the equations Prigogine used to
>>>> describe open dissipative systems.
>>>
>>> Reaction diffusion equations can be reversible in principle.
>>>
>>> Basically, the whole of the laws of physics exhibit time-reversal
>>> invariance - or at least all the modern attempts to formulate
>>> physical law have this property - so the rule of thumb is if
>>> you can do something in the real world, it can be done reversibly.
>>
>> How would you argue that the second law of thermodynamics exhibits
>> time-reversibility? They are inconsistent IMHO.
>
> Definitely not.
>
> In fact the second law is practically a *consequence* of reversibility!
>
> If you investigate reversible systems, one of the things you
> find is that they often tend to get more disoreded as time passes,
> if you start them in an ordered state. That's basically a consquence
> of the fact that the disordeded states massively outnumber the
> ordered ones - and so evolution from ordered states is likely to
> result in more disoreded ones.
>
> By contrast, irreversible systems often become more and more ordered
> as time passes.
>
> The fact that the temporal asymmetry in the second law could be
> derived from temporally-symmetrical physical laws - provided an
> initial ordered state was assumed - was one of the discoveries
> of Boltzmann, who:
>
> ``explained in statistical terms the second law of thermodynamics, i.e.,
> that entropy must in general increase for an isolated system, and showed
> how such `irreversible' behaviour could follow from the time-symmetric
> laws of mechanics.''
>
> - http://www.ias.ac.in/resonance/Sept2001/Sept2001p3-5.html

In it's simplest (most summarized) form, the second law of thermodynamics
asserts that order can only decrease in closed systems. This is identical
to saying that order cannot increase. Therefore, any change in order, which
must be a decrease, cannot be reversed. I don't accept using Boltzmann's
statistical approach as a valid way to contradict my claim here. Are you
claiming that Clausius was wrong, and that most other physicists would agree
that Clausius was wrong?

Guy

Relevant Pages

  • The second law of thermodynamics
    ... >> If you investigate reversible systems, ... > In it's simplest form, the second law of thermodynamics ... A more correct statement would be that order tends to decrease in systems ... Are you claiming that Clausius was wrong, ...
    (sci.bio.evolution)
  • Re: Genealogical Momentum
    ... In fact the second law is practically a *consequence* of reversibility! ... initial ordered state was assumed - was one of the discoveries ...
    (sci.bio.evolution)