Re: Lizard engines and rat engines


"g" <gillawton@xxxxxxxxxxxxx> wrote in message news:dbvc4u$n0a$1@xxxxxxxxxxxxxxxxxxxxxx
> ... I need to do a lot more reading and thinking about entropy. I just
> sense that most of the people I come into contact with have a "gut feeling"
> about entropy whereby something has to be put into order by an intelligent
> orderer (divine, human... or whom have you)

While there is some pretty fuzzy thinking about entropy in this group,
no one here is quite THAT fuzzy. However, there are at least four
different meanings of entropy that are used by people in this group,
and that can be confusing.
1. Information theory entropy (as defined by Shannon).
2. Classical thermodynamic entropy (as defined by Clausius).
3. Statistical mechanics entropy (as defined by Boltzman).
4. Entropy as "disorder".

The first three are quantitative. You can measure them. The second
and third are nearly the same thing - the second "reduces to" the
third. The fourth one is a bit fuzzier - there is no way to quantify
it unless you can quantify "order" and everyone has their own opinion
as to how that should be done.

> and then, unless more energy
> is input to the maintenance of that order, all returns to chaos.

There is a bit of truth in that. Certainly it is true that entropy
(under all four definitions) tends to increase. And the descent
into disorder can be prevented only by the expenditure of free energy.

But it is sometimes the case that the increase in entropy is so slow
as to be negligible. Consider a grain of salt. Low entropy -
highly ordered. But there is almost no tendency to lose that order
spontaneously. Just keep that salt grain dry, and it will keep its
order until the sun becomes a red giant a few billion years from
now. You don't need to keep expending energy to keep that salt
grain from losing its order.


.

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