Re: Definitions

["Glenn A. Carlson" <gcarlson@MAIL.WIN.ORG>]

To chemists (and to me) "static equilibrium" and "dynamic equilibrium"
are different concepts.  In static equilibrium nothing changes, e.g.,
the ball sits at the bottom of the hill.  In dynamic equilibrium
something changes but some aggregate property does not, e.g., in a
sealed container water molecules are continuously exchanged between
the liquid and vapor phases, but the average amount of liquid and
vapor does not change.

If "equilibrium" is "less precise" than "static equilibrium," then the
use of "static" must add something to "equilibrium" to make it more
precise.  What does it add?  And what is lost or missing if it is not
used?  If "equilibrium" is only a "near synonym" of "static
equilibrium," then give an example of equilibrium which is not static
equilibrium.  My example is chemical equilibrium (an example of
"dynamic equilibrium" to chemists).  What's yours?  The term "static"
means something; if not, it is mere surplusage (e.g., an "illegal
crime").

Glenn A. Carlson, P.E.
gcarlson@mail.win.org

> Subject: Re: Definitions
> Date: Sat, 28 Oct 2000 12:39:24 -0400
> From: John Denker <jsd@MONMOUTH.COM>
>
> At 09:49 AM 10/28/00 -0500, Glenn A. Carlson wrote:
> > I'll back up a bit to offer a couple of situations in which arguing
> > about definitions is not mere bickering.
>
> > ... When someone talks about "static equilibrium", but cannot
> > distinguish static equilibrium from non-static (dynamic?) equilibrium.
>
> I agree that "dynamic equilibrium" is an ugly and unhelpful term.
>
> Constructive suggestion:  When somebody starts talking about "dynamic
> equilibrium", try to steer the conversation toward three different terms
> for three different concepts:
>          * equilibrium
>          * stability
>          * damping
> For example:
>    http://www.monmouth.com/~jsd/how/htm/equilib.html
>
> Subject: Re: Definitions
> Date: Sat, 28 Oct 2000 21:56:23 -0700
> From: Leigh Palmer <palmer@SFU.CA>
>
> The term "static equilibrium" is integral; "static" is not a modifier.
> "Equilibrium" is a less precise near synonym which may be used when no
> confusion can arise.
>
> Perhaps the term "dynamical equilibrium" is appropriate to equilibria
> established within a noninertial frame of reference. I'm thinking of
> the status of particles at the L4 and L5 points in the restricted
> three body problem which was elaborated by Joseph Lagrange. There are
> many other similar examples in celestial mechanics.
>
> Leigh