Re: operationally inertial frames

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

And let me add (I hope John doesn't mind an "ally" rewording a few things,
perhaps not to his liking); while there may be a global way in principle to
perform the test; operationally it is basically impossible to perform the
global test. The reason being the global test requires you to investigate
every location and determine that the force is proportional to the inertial
mass and proportional in the same way, *at every point*.

I interpret this to be the reasoning behinds John's comment earlier:

"For me, it is because there is no satisfactory operational way to
determine whether or not you are in a so-called "inertial frame."

To which I say Amen.

I point people to the following reference:

"On the Classical Laws of Motion", Am. J. Phys., 26, 144 (1958).

Saletan in his newly published graduate Classical Mechanics Text (from
Cambridge U. Press) bases his formulation of Newton's Laws on the above
reference.

This all has bearing on the perennial "centrifugal/centripetal" force
discussions.  When I entered the foray of that discussion in one of its
incarnations, I did an exhaustive search utilizing the Science Citation
Index from 1958 to 1997; (I was really bored one summer day in Atlanta, and
killed the time doing the above at Emory U. library).  I looked up every
citation and found no criticism of the above reference.  (I did not look up
one citation, it was to a Polish journal that the library did not subscribe
to, and I imagine my Polish would have been inadequate for the task.)

I strongly recommend all Physics instructors on all sides of these issues
read that reference sometime in their life.

Joel Rauber

> On Wed, 13 Oct 1999, I wrote:
>
> > ... if the earth and all of its occupants were accelerated in some
> > direction at an arbitrarily large rate, say 1000 g, we'd
> have *no* local
> > way of detecting that fact and we could treat the earth's
> surface as a
> > Newtonian inertial frame anyway.
>
> Perhaps it would help to make this important point more
> forcefully (so to
> speak) if I add that we could even "shake" the earth and all of its
> inhabitants with an *arbitrary* time dependence and still
> have no local
> way of detecting that fact as long as the shake was performed
> inertially, that is, applied to each particle in the form of a time
> dependent force that is proportional to each particle's inertial mass.
>
> There; *that* oughta force someone to develop enough outrage that they
> will find a "nitpicking" flaw in my argument!  ;-)
>
> John Mallinckrodt      mailto:ajm@csupomona.edu
> Cal Poly Pomona          http://www.csupomona.edu/~ajm