>>14291915time being a dimension would not change things
The question of what inertia really is has not yet been answered
"an object in motion tends to stay in motion"
This is just an observation
It's like saying "apples tend to fall from trees" and believing there is no deeper mechanism causing this motion.
I don't think we will know the answer until we truly understand the single mechanism from which all other behaviors emerge
Maybe we will come to know it as god