A possibility is that in cosmic background, primordial photon lattice where emerges a way to mass conservation, a photon was disturbed to create a spin then lead to its neighbors consecutively avalanching -- CMB -- into this a small ripple, which inverse spin directions pointing to a world was made of matter or antimatter whichever is parity violation; now cosmos was like an expanding hole -- an isotropic gravity field -- in photon lattice that influenced on everything, so inertia will be partly clarified.