# Free fall and orbit question.

If I am in orbit around earth that means that I am in constant free-fall around earth.
Is this an inertial reference frame?

I do not believe you are. An inertial reference frame is one in which there is no acceleration. Here you have a centripetal acceleration due to gravity.

WannabeNewton
In the Newtonian framework no, a freely falling frame is not inertial because it is accelerating with respect to some fixed background inertial frame. In the GR framework, a freely falling frame is locally inertial.

so it would be considered inertial, then I could use special relativity in that frame

WannabeNewton
In Newtonian mechanics it is not an inertial frame (however you can still do Newtonian mechanics in this frame as long as you transform to the frame correctly). In GR, it is locally an inertial frame and locally you can do SR.

Dale
Mentor
2020 Award
so it would be considered inertial, then I could use special relativity in that frame
Locally, yes.

ok here is a question I have had for a while related to that. Lets say there is a charged spherical shell around me and the earth, and I am orbiting the earth, and the charged spherical shell is rotating with me at a constant
$\omega$ so relative to me the charged spherical shell is not moving and the shell is just slightly at a larger radius than me. But to someone standing on earth the shell is rotating, and in their frame this will produce a B field that points up and is constant. whats going on.

WannabeNewton