Dynamic and static eq. (was Re: concepts)

Cliff Joslyn (joslyn@KONG.GSFC.NASA.GOV)
Tue, 10 Oct 1995 12:32:43 -0500

>Don Mikulecky,MCV/VCU,Mikulecky@gems.vcu.edu
>>>1.2. Examples of non-equilibrial self-organization: Benard cells,
>>> vortices, cellular automata, autopoiesis.
>>
>> I believe that the usage more in keeping with the technical literature to
>> capture the same concept is "static equilibrium" vs. "dynamic equilibrium".
>> If my hand rests on a table, that's static; if mine pushes against yours
>> with equal force and neither moves, that's dynamic. Each is equilibrial in
>> that there is no movement.
>
>Help me please! How does the hand on the table countering gravity by
>the existence of a stationary table differ from one stationary hand
>countering the motion of the other. In fact, as far as hands go, there
>is never anything approximating equilibrium in either case, so you must
>be talking about mechanics vs. statics here.

Equilibrium is a concept used in thermodynamics, in dynamical systems, and
in natural language. Here's I'm referring to dynamical systems and natural
language, where equilibrium means zero velocity (no change in state). If I
didn't make it clear, the two hands are PUSHING against each other with
OPPOSING force. If either lets up, the other moves. That's dynamic eq., as
opposed to a hand resting on a table, where a static force of the table
opposes gravity.

>The notion of dynamic
>equilibrium in that context has a lot more meaning when we thing of the
>least action principle as an alternative to Newtonian mechanics.

To the extent that I understand it, I agree that least action provides an
elegant generalization, but I'm not familiar enough with it.

O---------------------------------------------------------------------------->
| Cliff Joslyn, NRC Research Associate, Cybernetician at Large
| Mail Code 522.3, NASA Goddard Space Flight Center, Greenbelt, MD 20771 USA
| joslyn@kong.gsfc.nasa.gov http://groucho.gsfc.nasa.gov/joslyn 301-286-2598
V All the world is biscuit-shaped. . .