In earlier posts I have explained the difference between exogenous and endogenous processes and why the equivalence principle only holds if and when gravitation (endogenous), acceleration and inertia share the same endogenous driver .
Consequently we have to make a distinction between inertia as the tendency to maintain momentum (exogenous) and inertia as the tendency to maintain mass (endogenous, see for instance post 17). Therefore I make the distinction between exo-inertia and endo-inertia.
Endo-inertia, how does it work, what are its properties, its relations to gravitation and acceleration?
As explained in post 21, the tendency of an electron to go nearer to the nucleus gets stronger the greater the distance from it, its mass increases, time delays. In lower orbits the opposite happens, a stronger tendency to get away from the nucleus through mass decrease and time-acceleration. As suggesred there is no change of momentum.
In this article I suggest the possibility that electromagnetic interaction is in essence endo-inertia, the tendency to maintain mass (no change of momentum, in contrast with exo-inertia, the tendency to maintain momentum without change of mass).
Gravitation (consequence of a continuous relation between mass and time), time-driven (de)-acceleration and emdo-inertia are equivalent (see posts 9 and 15).
Why is the electromagnetic interaction force vastly stronger than gravitation? In electromagnetic interaction processes changes of mass and energy are directly proportional to each other, they are working together, reinforcing each other. In gravitational processes changes of mass and energy are inversely proportional to each other, they are counteracting.
cosmicsignals 
There’s no such thing as *a free lunch * for Inertia.
=.
Newton wrote:
* For the basic problem of philosophy seems to be to discover
the forces of nature from the phenomena of motions
and then to demonstrate the other phenomena from these forces*
=..
For the movement we must pay energy-money.
There isn’t inertia without force / energy.
Your car wouldn’t move even one inch without force /energy.
But Newtonian conception of *inertia* says nothing about the forces of inertia.
The idea of forces for * Inertia* was solved by Einstein.
In 1905 Einstein wrote paper:
“ Does the inertia of a body depend upon its energy content?”
As he realized the answer was:
“ Yes, the inertia depends on its energy E= Mc^2.”
How can E=Mc^2 be responsible for inertial movement of quantum particle?
Nobody explains the details of such possibility of inertia movement.
Someone wrote:
“An old professor of mine used to say
that anyone who can answer that question
what inertia is, would win a Nobel Prize. “
=..
Best wishes.
Israel Sadovnik. Socratus
=========================.
I have introduced in Physics the difference between exogenous and endogenous processes (quite common in Economic Theories, but not recognizwd yet by the Physics Community).
Although endo-inertia is not without “force/energy”, this “force/energy” is for free.