Introduction
The universe is characterized by continuous endogenous motions, acceleration and deceleration in all directions, with all the corresponding mass/energy changes/transformations. The continuous universal transformation process is the basis of this. Light forms part of this transformation process (see also post 41).
Everything moves, nothing remains still (Heraclitus). Nothing cannot happen in space (see also post 38). There is no such thing as rest mass. Rest mass is not a property of the real world.
Endo-inertia
In post 23 I have described endo-inertia as tendency to maintain mass (see also posts 25 and 27).
The continuous endogenous universal transformation process is autonomous.
Accelerating masses emit energy (mass decrease), decelerating masses absorb energy (mass increase); these phenomena are compatible with EDU (see post 41) as they are accompanied by time acceleration and time delay. Comparable with the behavior of light under the influence of gravitation, that is to say the impact on the frequency of the radiation concerned (see post 12). I also refer to posts 38 and 39.
Nota bene: no matter whether time accelerates or delays, it always goes forward, in all directions.
I therefore suggest the possibility that the tendency of Endo-inertia to maintain mass is determined by the autonomous, automatic mass/energy control processes caused by time differences, thus preventing that energy emissions and energy absorption get out of hand. For instance as active and effective singularity contraceptive.
Conclusion
The source/nature of eendogenous (autonomous) inertia is a matter of time. It is determined by time differences, in compatibility with EDU (Einsteinian Dynamics Updated).
The consequence of my suggestion is that quantum mechanics is redundant, not a theory of the real world. Time is an endogenous, continuous, fundamental, real and variable property of the world.