Re: Lizard engines and rat engines

Perplexed in Peoria <jimmenegay@xxxxxxxxxxxxx> wrote or quoted:
> "Tim Tyler" <tim@xxxxxxxxxxx> wrote in message news:db6va6$qrd$1@xxxxxxxxxxxxxxxxxxxxxx
> > Perplexed in Peoria <jimmenegay@xxxxxxxxxxxxx> wrote or quoted:

[Materially - but not energetically closed systems]

> > Since E=mc^2 tells us that energy and mass are fundamentally
> > interchangable, the whole idea doesn't make very much sense to me.
>
> That comment MIGHT make some sense if e=mc^2 had been known when the
> standard terminology of thermodynamics was being hammered out. But
> it wasn't. Now that we know about relativity, I'm sure that someone
> has worked out just how the basic definitions and theorems need to
> be changed.
>
> I am familiar with how that process played out in
> mechanics. Some formulas are still valid (though the terms have
> slightly different meanings). Some formulas have to be modified
> by adding one of those ugly Lorentz terms.
>
> I am not familiar with how that process played out for thermodynamics.
> Bekenstein and Hawking worked out the details only recently.
> Apparently, entropy needs to be redefined so as to involve the
> surface area of any black holes in the system. But since I use
> thermodynamics only for biochemistry, I haven't bothered to learn
> the details. I only carry my calculations to two decimal places.
> But I have seen thermodynamics used in an analysis of stellar
> structure, and the fact that the star is losing mass as a result
> of fusion reactions didn't seem to bother anyone.
>
> Tim, just in case my sarcasm in the previous paragraphs didn't
> come through, what I am really saying is that invoking e=mc^2
> is grasping at straws. I have no idea why you think that doing
> so is reasonable.

If a system is not energetically closed, it's not going to be
materially closed - since energy and mass are interchangable.

Maybe the concept was developed before this was appreciated - or
maybe it's only intended as a simple approximation - whatever.

Complete closure looks like the more important and fundamental
idea to me.

Partial closure looks like a much more messy concept - one that
doesn't stand up very well to close scrutiny.
--
__________
|im |yler http://timtyler.org/ tim@xxxxxxxxxxx Remove lock to reply.

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