The Essence of Inertia -Mass is Merely a Practical Term

<div xmlns="http://www.tei-c.org/ns/1.0"> Acceleration in elementary particles exhibiting inertia is accompanied by an increase in their internal energy U and a concomitant decrease in the characteristic radii R and r, as prescribed by our particle model. This model yielded the derivation and accurate calculation of their masses (Appendix A). The external force required to produce acceleration performs work that enhances the local curvature of space, effectively reducing R and r. This process introduces additional stress and strain within the spatial structure, thereby amplifying curvature. Through this mechanism, Newton's Second Law is recovered, providing a geometric and energetic basis for the emergence of inertia. Accordingly, mass should be interpreted not as a fundamental property, but as a derived, operational parameter. In inertial particles, it is the energy content that gives rise to resistance to acceleration, justifying the relation m = U/c 2 over the conventional form U = mc 2 . (Here, U is used in place of E to avoid confusion with electric field strength). This distinction becomes particularly salient in the context of massless particles -such as photons and gravitons -which possess energy and momentum but do not exhibit inertial response, and hence, lack mass. </div>