Is the Pen on My Desk a Geodesic and Is My Room an Inertial Frame?

[wpoely]

Hi,

I was wondering: I'm sitting at my desk and on my desk lies a pen. Does the pen describe a geodesic? And is the room I'm sitting in an inertial frame?

I think the pen doesn't describe a geodesic because it's not in free fall and i think my room is a good approximation of an inertial frame for things that happen in my room.

Am i right? Thanks!

 

[cesiumfrog]

No. If the desk wasn't there, then for a few seconds the pen would describe a geodesic. Similarly, your room is no better inertial frame than an elevator.

 

[JesseM]

Your room would be a good approximation for the frame of a room undergoing constant 1G acceleration through space in special relativity.

 

[wpoely]

So, in practice, only when an object is in free fall, we know it describes a geodesic.

Thanks for the answers!