Re: SOHO Thanks

[Leigh Palmer <palmer@sfu.ca>]

> the normal hs class has enough trouble with inertial frames that
> introducing accelerated frames is too great a stretch.

I must point out that the normal frame of reference used in hs is
*not* inertial. It includes a force which is proportional to mass,
just as the centrifugal force is. That force is the gravitational
force which is approximated by mg uniform and downward everywhere.
That's why free particles don't obey Newton's first law (the law
of inertia) in the "normal" frame of reference. Since it is not
an inertial frame why would one expect such objects to obey the
law? Finally let me point out that centrifugal force is present
and appreciable* at your latitude in the "normal" frame of
reference. The fact is that you simply ignore it by lumping it
into the force you call "gravity". The direction you call "down"
is not toward the center of the Earth; it is in the direction of
this combined force.

I think that students should be told this in high school even if
only *en passant*. It wouldn't take much time, and real world
examples abound to help them understand. Accelerated frames are
quite familiar to your students, and those same students have
very few other real world referents to things they learn in
physics class. Small wonder that many do not associate physics
with the real world when they enter college.

I know I won't win this argument; such is the nature of religious
arguments. What I hope to do is raise consciousness. Einstein
teaches us that gravitational fields are locally indistinguishable
from accelerated frames of reference. Recognition of that idea
(the principle of equivalence) led him to his general theory of
relativity. Pondering the meaning of that principle is worthwhile.

Leigh

*Please do the calculation.