Once we get down to the quantum level, mass is derived directly from energy.
From Wikipedia: Most of the mass of hadrons is actually QCD binding energy, through mass-energy equivalence. This phenomenon is related to chiral symmetry breaking. In the case of nucleons – protons and neutrons – QCD binding energy forms about 99% of the nucleon's mass. That is if assuming that the kinetic energy of the hadron's constituents, moving at near the speed of light, which contributes greatly to the hadron mass, is part of QCD binding energy. Considering that nearly all of the atom's mass is concentrated in the nucleons, this means that about 99% of the mass of everyday matter (baryonic matter) is, in fact, chromodynamic binding energy.
Since we know that velocity is a main cause of time dilation, would it not be true that it is the velocity of the hadrons constituents, moving at near c, that is the true source of time dilation for any object, including a planet or star?
