Re: Newton's 3rd law?

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

David Bowman wrote:

> ... Newton's 3rd law implies and is consistent only with instantaneous
> interaction at a distance.  It is inconsistent with the retarded
> causation of relativity--both special and general. ....

What about saying that "as soon as an object A (magnet or sun) starts
acting on an object B (iron block, planet) the object B starts acting on A
with the force of equal magnitude"?  ["A starts acting on B" means that
B starts experiencing an effect of A. I will clarify this, and the "as soon
as" at the end.]

I am anticipating a reply in the form of "in whose frame of reference?".
My answer, without too much thinking, would be "it does not matter".
It is probably wrong. But where is the error? I am in the frame of the
magnet, you are in the frame of the block. Each of us makes the same
statement about Newton's third law. And each of us is correct, even if we
do not agree on the mathematical description of the force at any given
moment (moments are short intervals dt1 and dt2 in our proper frames).

How can the law be verified? Suppose each of us records a(t) with
respect to the center of mass (inertial frame of reference). As we come
closer and closer I observe a(t1) and you observe a(t2). The accelerations
increase from zero up to some final values. I multiply each  a(t1) by the
mass of the magnet, m1, you multiply a(t2) by the mass of the iron block
m2. We would probably be able to match our mean products in consecutive
dt1 and dt2 intervals. Would this not be a validation of Newton's third
law? To simplify the problem I assumed we are massless creatures in a
one-dimensional world.

Ludwik Kowalski