Re: Centrifugal force

[Jerome Epstein <jerepst@worldnet.att.net>]

Bob Sciamanda wrote:
>

> I think Newton believed in absolute time and space and, at the outset,
> fully expected that the best that he might do would be to find a physics
> which would work only for an observer at absolute rest.  The existence of
> a whole class of inertial frames was an unexpected (and, I think,
> undesired) conclusion, not an assumption.

The invariance under the Galilean transformation (between inertial
frames) was already implicit once it was clear that the fundamental laws
involved acceleration and not velocity. Acceleration is invariant under
the change to a uniformly moving frame. YOu are correct, however, that
Newton clearly believed in sbsolute space and absolute motion ever after
knowning that his mechanics was invariant under Galileian
transformations.
> He certainly believed in INVARIANT force pairs of interaction between
> bodies as the basis of his mechanics.  Only the inertial observer can use
> observed acceleration as the measure of these forces, since accelerations
> are frame dependent, but Newtonian forces are frame invariant, 

I am baffled by this. Acceleration is unchanged by a transformation to a
frame in uniform motion with respect to the first frame. For inertial
frames, accleration is NOT frame dependent.