Re: [Phys-l] Simulating a disturbance of a stable planetary system.

[chuck britton <cvbritton@embarqmail.com>]

Use the analogy of the 'cone' lying on its side.
This a mechanically 'Neutral Equilibrium'.

Not 'Stable' (self correcting) Disturbance => Return to Initial  
Condition.

Nor 'Unstable' Disturbance => disaster

But' Neutral'	
	Disturbance => moves to (most likely) New, Different condition of  
equilibrium.

Circles and ellipses are both neutral equilibrium conditions.
Each disturbance shifts the system to different (but still neutrally  
stable) equilibrium.


Confusion comes from naming the 'cone standing upright' as Stable
while naming the lying down on its side as being 'Neutrally Stable'

Perhaps we need a pedagogical adjective to describe the 'Standing  
Upright' stability as maybe 'Self-Correcting Stability' as opposed to  
'Go-with-the-Flow (neutral) Stability.

	I think that PC (Pedagogically Correct) semantics
	is a big part of this current discussion.

On Dec 30, 2007, at 9:45 PM, Ludwik Kowalski wrote:
> The idea was to show that a disturbance applied to a two-body  
> system is
> self-correcting