Board Thread:General Discussion/@comment-9154802-20180509212825/@comment-29564364-20180514194331

Quartzmaser wrote: Unfortunately, inertia is the capacity to resist change to motion or rest; it isn't a quantitative property but a qualitative property. *Sigh* I knew I should have left it in... My original reply had the mention that I was basing this hypothetical on the assumption that inertia was independent from mass so that finite mass could have infinite inertia. That way, I got rid of the problem of having infinite mass in a finite volume or infinite mass in an infinite volume, which is for the least problematic when considering two such objects in relative motion to each other, but I later removed it, thinking that my reply was already lengthy and that no one would bring attention to that detail. I now see I was wrong.

Given that mass is the amount of inertia that an entity has, i think it would be more appropiate to say if an entity had an infinite amount of mass, [...] As you pointed out, since inertia is a quality of mass, the difference between infinite mass and infinite inertia is a purely semantical one.

[...] it would be both immovable to an observer at rest and unstoppable (or at least able to move faster than light) to an observer in motion. Relative to what? Given that all motion (and rest) is relative, it's ambiguous at best and meaningless at worst to state that an observer is in motion or at rest without specifying a frame of reference.