Re: Spookiness in physics

From: Patrick Reany (reany_at_asu.edu)
Date: 09/14/04 

Date: 14 Sep 2004 07:40:00 -0700

dubious@radioactivex.lebesque-al.net (Bilge) wrote in message news:<slrnckbtfd.2v1.dubious@radioactivex.lebesque-al.net>...
> Patrick Reany:
> >dubious@radioactivex.lebesque-al.net (Bilge) wrote:
> >> Patrick Reany:
> >> >Why don't we regard all noncontact forces as "spooky"?
> >>
> >> What is a ``contact force?'' Don't give a naive definition.
> >> Explain what it means for two objects to be in contact. So,
> >> you need to define what an object is first. You'll need to
> >> do this such that your definition explains why two objects
> >> don't pass through each other. I think once you try to deal
> >> with a contact force, you'll discover it's not very simple to
> >> make that concept physical.
> >
> >I'm referring to the model of the perfectly rigid body to make the
> >point that there is no reason to think of one type of force as any
> >more "spooky" than any other kind of force.
>
> So, your model of a contact force starts with the force having the
> form,
>
> F(r) = \infty 0 <= r <= R
> = 0 r > R

You have chosen to model the forces associated to spheres. OK, but
since these spheres will never intersect in this crude model, we can
claim:

Assume we have two or more nonintersecting spheres of finite radii (no
part of any sphere is inside any other sphere). Let S and S' be any
two such spheres. Let S have of radius R. Let \ell be the line
containing the centers of S and S'. Let P be the point of intersection
of S' and \ell. Let r be the distance along \ell from the center of S
to P. Then the force on S due to the existence of S' is given by:

  F(r) = oo, r = R
       = 0, r > R

Patrick

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