[Phys-L] Interaction (was feeler-dealer...)

[Jeffrey Schnick <JSchnick@Anselm.Edu>]

What is an interaction?  When we have two charged particles, is the interaction what is going on between the two charged particles?  In an exchange particle model, they are exchanging virtual photons.  Is that ongoing exchange of particles the interaction?  If it is not what is going on between the two charged particles, is it what is going on between a virtual photon and one of the charged particles?  In a field model, is it what is going on between a field and a particle, right there at the boundary between the two of them? 

 Is that which keeps a neutron star from collapsing an interaction?  If so, that would suggest that there doesn't have to be any kind of particle exchange going on in the case of an interaction.

> -----Original Message-----
> From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Richard Tarara
> Sent: Thursday, December 12, 2013 11:15 AM
> To: Phys-L@Phys-L.org
> Subject: Re: [Phys-L] feeler-dealer, third law, et cetera
>
> I'm not sure I'm comfortable with the electron/proton example as a violation
> of the third law.  Unlike situations like that presented below by Philip, even
> at the intro level I would never say that electron A exerts a force on proton B.
> Rather I would state that moving electron A produces a magnetic field C that
> interacts with proton B producing a force on that proton.  At the same time,
> moving proton B produces a magnetic field D that interacts with electron A.
> Even at the most elementary level, we HAVE to talk about the fields with the
> moving charges, but don't need to bring in fields to a hand/ball interaction.  It
> is the field/charge interaction that will deflect the
> particles.   I'm certainly not absolutely convinced there is a third-law
> violation here, but if so, I suspect it is because we have left the "Newtonian
> world".
>
> rwt
>
> On 12/12/2013 7:23 AM, Philip Keller wrote:
> > When I state the third law in class, I begin: "when an object A exerts
> > a force on object B..."
> >
> > This formulation evades the issue of whether the third law applies to
> > the sum of the forces.  And I am glad to evade that question:  I care
> > about the sum of the forces that act ON object A because that sum
> > determines object A's acceleration.  I don't care about the sum of the
> > forces exerted BY object A because it is likely that they are acting
> > on an assortment of objects, each which are experiencing their own
> collection of forces.
> > I have often told my students that I am unaware of any exceptions to
> > this law and that if there were any exceptions, they would violate the
> > law of conservation of momentum.  But now I see from Bruce's post
> > about the electron adn proton pair that I have some reading to do.
>
> --
> Richard Tarara
> Professor of Physics
> Saint Mary's College
>
> free Physics educational software at
> www.saintmarys.edu/~rtarara/software.html
>
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