Is Inertia Quantifiable and Measured by SI Units?

[Loren Booda]

If the definition of inertia includes changes in momentum, by its definition how do interactions of photons (non-inertial) or masses (inertial) differ otherwise?

 

[Yor_on]

Photons and mass are two different subjects. They both 'obey' the geometric properties of spacetime though. That is, both will 'bend' to gravity. Photons have what's called an instant acceleration, relative or rest mass do not. Otherwise I agree in that it is a 'muddy' question :)

We can slow down light and even stop it, when we do that it disappear, as far as I understand, only to show itself when we accelerate it again. Then again, I might be wrong here. On the other hand, electrons are not defined particles either, they just have a probability focus, right:)

And inertia is a property of relative / rest mass which differs from photons instant acceleration. But I have problems with exchanging mass for inertia as inertia is a intangible property concurring from mass, whereas mass does not, as far as I know, create itself by experience inertia.