Hello! My name is Edward Solomon and I have found a very particular concept in classical physics to be more mystifying and puzzling than even more advanced topics covered in modern physics. This is the theory of "inertia." Although there is much literature covering the effects of inertia, I have yet to come across any texts that state the "cause" of inertia. The best answer I've come across is that it is an "inherent property of mass." What is interesting is that inertia cannot be a force. This follows from the very definition of inertia. Here is a simple (and hopefully well-known) proof of this claim. F = ma We can interpret inertia to say that an object will not accelerate unless acted upon by some force. In other words inertia preserves scalar and angular momentum, thus the "force" of inertia is equal to zero. So now for my ultimate question. Photons carry electro-magnetic radiation, gluons carry the strong force, the predicted-but-yet-unobserved gravitons carry the gravitational force (recall that inertia and gravity are derived from the same quantity "mass"). Is there any hypothesized particle that may carry inertia? Another question: The centrifugal force, Coriolis Force and the Euler force are known as the three fictitious forces. Is the concept of inertia simply a "fictitious" entity itself to explain what we do not know. Last question: Even if inertia is real, its force is equal to zero, so how could we ever detect it? How can it even interact with our universe? For instance if in some strange universe, Newton's Gravitational Constant (G) was equal to 0, then we could hypothesize that gravity exists, but we could never detect it because as far as our universe is concerned, gravity does not exist. The same concept seems to apply to inertia in OUR universe, unless there is a different concept of force that must be invented/discovered in order to adequately explain how it does interact with our universe.