Re: is free-fall an inertial frame?

[Stefan Jeglinski <jeglin@4PI.COM>]

> now i'm really afraid  this is a dumb question, (i'm a chemist and an
> educator, not a physicist) but without air or visual clues you would have
> no sensation of falling?

I think the sensation of falling is something that one gets from
sensory cues (eyes, ears [balance]). Imagine yourself on the space
shuttle, essentially in free fall. Aside from getting used to the
feeling, and seeing objects floating around you, I don't think there
is a real sensation of -falling-. And this is one of the points: To
investigate this situation without relying on your senses (am I
really falling? am I being fooled? I've been on the shuttle for 7
days now, why haven't I hit the ground?), you would rely on an
instrument. An excellent one in this case would be an accelerometer,
which would float beside you, registering... nothing.

That it registers nothing is part of the point of my question, which
has to do with the definition of an inertial frame. But aside from
this, the result appears to be non-intuitive to many and might make
an excellent exam question for introductory students (or even more
advanced students). Since they have "some outside knowledge" (like a
textbook or authority figure) that states they are being accelerated
by gravity, they assume that this would register on a measuring
device. But no.


Stefan Jeglinski