I'm a physics graduate, but have not used my skills for 15 years, so I've
forgotton most of it.
Just some idle questions here if anyone has nothing better to do at this
I think it is generally recognised that gravity is not a force as such, but
is something that changes the zero acceleration frame (the accelleration
where no force is required to produce that acceleration aka newtons law
a=f/m). So for example in deep space the acceleration that requires no force
is zero (except for the forces/gravity from the rest of the universe), but
on the surface of the earth the acceleration that requires no force is
10m/s/s downwards, and an upwards force is required to produce an
acceleration of zero.
How does this work with a zero frame of rotation? This is the rate of
rotation where no centripetal force is required to keep the body from flying
In deep space the zero frame of rotation is zero rotation relative to the
distant stars, but what is it if you are in orbit around the earth? Is it
the same as deep space (characterised by the non-rotating object always
pointing to a distant star) or is it the same as the orbiting object (so
that when you're on the orbiting object, it will appear that it is not
I think the answer is the former (take the example of the faucoults pendulum
(sic)) so that there is a true "absolute zero" frame of rotation.
I wonder whether there are any gravitational situations where this zero
frame is changed.