The discussion centers around the nature of inertia, its relationship with mass, and how it arises according to various physical principles. Participants explore theoretical aspects, practical examples, and philosophical implications of inertia, touching on concepts from classical mechanics to modern physics.
The discussion reflects multiple competing views on the nature of inertia and its explanation, with no consensus reached on a singular understanding or framework. Participants express differing interpretations of inertia, its causes, and the implications of various physical laws.
Participants acknowledge limitations in their understanding and the complexities involved in defining concepts like "straight line" motion, particularly in the context of orbits and forces acting on objects.
Doesn't "mass there governs inertia here" imply that the inertial mass of a body depends on the spacetime geometry?PeterDonis said:My personal view on GR is closer to that of the Cuifolini and Wheeler textbook I referenced, whose tag line is "mass there governs inertia here", i.e., GR is Machian to the extent that such a question even matters. The Einstein Field Equation says that the spacetime geometry at any event is determined by the distribution of stress-energy in the past light cone of that event. That seems pretty Machian to me.
No. A more precise phrasing would be that mass there governs inertial motion here. Mass there determines the spacetime geometry here, and the spacetime geometry here determines which worldlines here are inertial, and what the path curvature is of worldlines here are not inertial. But path curvature is only proper acceleration; what you feel as weight is proper acceleration times inertial mass. The spacetime geometry does not determine what the inertial mass of a body is.timmdeeg said:Doesn't "mass there governs inertia here" imply that the inertial mass of a body depends on the spacetime geometry?
Yes this way it makes sense to me and I would prefer to call it just Einsteinian.PeterDonis said:No. A more precise phrasing would be that mass there governs inertial motion here.