Re: laws of thermodynamics

Yep - sloppy on my part. Thanks guys for the more careful articulations.
JimA

Randy Isaac wrote:

> Jim,
> Your comment that "First, the 2nd law refers to a closed system
> (no net energy in or out) which our local situation (in universe
> address terms) is not." is a common misunderstanding of the 2nd
> law. The 2nd Law is actually universal in scope.
>
> Allan,
> Thank you for the link to your well-written essay. Specifically
> your paragraph addresses Jim's comment very well: "It is worth
> mentioning here that the usual reply to creationists that "the second
> law doesn't apply to non-isolated systems" is not quite correct. The
> second law always applies; in fact, it was originally developed for
> non-isolated systems (the working fluid of a heat engine). The key
> point is that it is only in isolated systems that the second law takes
> the simplified "entropy must increase" form. For non-isolated systems,
> the second law still applies as a statement about heat flows and
> temperatures, just not in the form used in creationist arguments."
>
>
> Of all the statements of the 2nd Law, my favorite is one I learned
> from George Uhlenbeck: "The second gradient of the free energy is
> positive" (which is much more elegant in equation form), meaning that
> the free energy is minimized in every physical process. The Free
> energy includes not only the well-known terms "U-TS" but also terms
> for pressure/volume, strain energy, chemical potential, magnetic
> potential, gravitational potential, etc. The overly-used "closed
> system" simplification keeps all the extra terms constant so that the
> remaining variable, entropy S, must be maximized to keep the free
> energy at a minimum.
>
> Randy
Received on Tue Jan 4 22:03:11 2005