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The Zero-Point Universe from Amazon.com
Concepts of mass began with respect to a body's acceleration due to gravity, its weight. But mass has to be considered as something separate from gravity, a fundamental property of matter, when we calculate that acceleration due to gravity. As scientists learned about particles like electrons and protons, those particles were presumed to have an amount of mass that was intrinsic to the particle. The origin of mass at the particle level has never been understood. Oh, there are some known proportionalities so numerological systems for computing mass energy were developed, but underneath it has never been clear why a proton has the mass it has, why an electron has the mass it has and how and why the ratio between those masses is ~1836.
As with everything in the universe, we can never be confident that we understand what is going on unless the theory of choice takes zero-point energy into account. The first thing that happens when a particle, or any other body exists in a space is that it displaces vacuum energy. Vacuum fluctuations that would have been present are not because a particle is in the way. If we consider a particle as a spherical shell of some kind, it will effectively be a Casimir cavity. The zero-point energy wavelengths that would normally exist in that space that happen to have a wavelength the same diameter as the particle's shell, can no longer exist. The higher energy wavelengths inside still exist, the lower energy wavelengths outside still exist, but the ones equal to the shell diameter are displaced. The displacement of zero-point energy reduces the energy density of the vacuum in the region of the particle. Here is a drawing showing the inner diameter di and the outer diameter do with vacuum fluctuations in the middle shown as ellipses.
We can calculate the mass-energy density of the proton from the proton mass-energy 938 MeV and its charge radius 0.88 x 10-15 meters giving 3.3 x 1038 GeV/cm3(GeV equals a billion electron volts which is approximately the mass-energy of a proton). Then if we consider that the spherical shell with the same radius, we find that the vacuum energy excluded by a shell the size a proton with a reasonable thickness is exactly identical to the proton mass-energy, 938 MeV. Similarly an electron has a mass-energy density of 6.8 x 1025 GeV/cm3 and if we consider the vacuum energy excluded by a spherical shell the diameter of the electron charge radius with respect to electron scattering, which is essentially the same as the Compton radius, we find that the excluded vacuum energy is the same as the electron mass-energy. These computations are described in greater detail in this paper in pdf format.
This fundamental description of mass has significant consequences for particle theory and gravity. With respect to particle theory, all mass must be considered with respect to zero-point vacuum energy displacement. As far as gravity goes, if mass is a fundamentally electro-magnetic phenomena, then gravity must be as well. The true origin of mass tells us that we must consider alternatives to the existing particle and gravitational theories, and these new theories must be consistent with the existence of zero-point energy.