The great physicist Ernst Mach did not consider Mass to be a true property of matter. He contended that what we label “Mass” does not exist for one object in isolation. Mass is only created by the “mutual relationship” between two or more objects. To speak of “Mass” is merely to speak of the changes in Velocity that each object generates in the other.
Said Mach: “It is possible to give only one rational definition of Mass, and that is a purely dynamical definition.”
Relatedly, Mach considered the Law Of Inertia superfluous. His reasoning was this… If we know that a change in Velocity only occurs when one object is acted upon by another, than this already tells us that something unmolested will continue in a straight line and in uniform motion… no need for a separate “law of inertia” asserting this fact.
Now, we all know that heavier things are more difficult to move than lighter things. The standard scientific line would have it that this is due to Inertia (heavier objects possess more of it). However, this really just boils down to a tautology… Something is more resistant to movement because it possesses more Inertia, and things which have more Inertia are more resistant to movement.
I feel that physicists have failed to provide any real scientific explanation for why “heavier” objects are harder to move than “lighter” ones—or really, what even makes one object “heavier” than another, fundamentally speaking. I mean, yes, obviously, denser objects or larger objects with more mass are harder to move than less dense or lighter ones… but WHY?
Somewhat in opposition to his own dynamical theory of Mass, Mach, in his book The Science Of Mechanics, attempted to explain Inertia this way: Inertia can be viewed as “an endeavor of the whole towards the center.” But I’m left wondering… if this endeavoring toward the center somehow accounts for Inertia, would not a circular object’s endeavorings cancel-each other out, producing a net-zero effect in regards to how much the object resists movement? Still, perhaps the answer to the riddle of Mass is somehow related to this conceptualization of Inertia.
Actually, I’ve come to believe that the whole concept of “Inertia” is bogus. We really do not know WHY more massy objects are more difficult to move. My best guess is that it has something to do with Mach’s (now forgotten) dynamical interpretation of Mass. But if Mach is right, then an object alone would have no mass (or– would the interactions of its component parts generate some?). Generally speaking, I’m betting that Mach was correct and that Mass (that is, resistance to movement, a.k.a. Inertia) only manifests as some sort of unexplained interaction between objects.
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