Why do people say that mass is too fundamental to know exactly what it is?

[Drakkith]

Thanks a lot for clearing that up. My AP Physics teacher told me wrong last year when he said that m represents the inertia in F=ma. And I went on for a year thinking this way. By the way, how is inertia measured? You say that it can be done.

As far as mass goes, mass is simply a systematic quantification of matter as I have tried to explain. You guys are telling me it is something more as if it is a ghost. It is an amount, not a property.

Hrmm. I think I was incorrect. The way inertia and mass are related, i believe it would be m that is the inertia in that formula. Honestly, after a bit more reading, it looks like mass and inertia are almost the same thing. It just depends on what you define as what. As wikiepedia put it, you could define mass as : "the quantitative or numerical measure of body’s inertia, that is of its resistance to being accelerated". Changing mass always results in a change of inertia, and changing the inertia requires changing the amount of mass.

But mass is defined differently under GR and such. So one could say that the inertia of an object is the measure of it's mass. Which makes sense, as measuring how fast a force will accelerate an object will give you its mass.

Is there anyone reading this with more knowledge that could elaborate?

 

[Lead Salad]

"My message was meant to convey that mass should have been defined in terms of distance and time only."

Yes yes yes!

One thing I think we can all agree upon is that the "masses" of the particles are characteristic, as in eigenvalues. If we can express mass interms of space/time, don't you think this hints at the wave-metric structure of these particles? That the particles are localized eigenmetric solitons?

Has anyone looked at localized time-harmonic eigenmetric solutions to equations that describe space (more specifically, the relationship between metric perturbations and energy), such as the Einstein field equations?

 

[Goldstone1]

How can anything be too ''fundamental''. It either is fundmental or isn't. And mass by the way, as fundmental as it is, it is not fully understood why photons can gain a mass, but it not because it is fundamental which makes it almost incomprehensible. If you don't know exactly what mass is, then that is a strict statement saying we will never know what mass is. That is demonstratably false, especially for anyone with any background in spontaneous symmetry breaking.