Math of GR - Addendum 3

But relative to you seeing Ring World rotate floating in space, the GEM does have a solution: motion with a constant velocity. Hence, this motion is CAUSED by the gravitational field. It predicts it. Hence, "mass" is caused by gravity.

More specifically, we tentatively venture into the "quantum" realm and say that the energy of gravity is QUANTIZED, and the quanta are called GRAVITONS. So just using my interpretation of GR and the most conservative quantum hypothesis imaginable, I conclude that it is gravitons interacting with matter that cause the "mass" of matter.

Not the Higgs particle.

The Nobel Prize in Physics 2013 was awarded jointly to François Englert and Peter W. Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider."

ATLAS and CMS found a particle, probably, but the origin of "mass" for any particle, either an apple or an electron, comes from the particle called THE GRAVITON.