A few comments about what others have said so far (and I only read
the digest so excuse me if you've added more today):
Maurice says, "There are much simpler, much more important issues to handle in
their first physics classes." I agree I have no intention of spending
multiple class periods on this issue. However, as a physics educator
I feel I need to have a clear understanding of as fundamental an
issue as N1. As Leigh implies, even if I don't spend much time
*directly* addressing this topic, it does form an important
foundational issue which makes itself felt at least implicitly at
many different junctures in the course. Right now, my understanding
of N1 is fuzzy. References from AJP and the like would be
appreciated; Arnold Arons let me down by not discussing inertial
frames in his fine book.
Bob accuses me of trying to use the first law in isolation to find
inertial frames. Guilty as charged: I thought that was the point of
N1. Okay, what is N1, as distinct from a special case of N2?
Finally, John D reminds us that we only need a reproducible
experiment and shouldn't worry about all possible minor effects.
Okay, I'll settle for an experiment which can tell me to within a
specified accuracy that a frame is inertial. And I'll now allow you
to use the full arsenal of physics, not just N1. What
state-of-the-art experiment can I do and what accuracy will it give
me? For example, Taylor and Wheeler say that a reference frame is
locally inertial when "throughout that region of spacetime--and
within some specified accuracy--every free test particle at rest wrt
that frame remains at rest...." As I've already said, that recipe is
lacking because they don't tell me what a "free" test particle is and
the only way I can think of answering that requires Newton's laws,
which leads to circular reasoning.
--
Dr. Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Annapolis, MD 21402-5026 mailto:mungan@usna.edu http://physics.usna.edu/physics/faculty/mungan/