This substance rushing in to the center of the earth creating pressure could be what we call gravity, no? Could gravitational lensing be the result of this substance rushing into the center of a mass and changing the direction of photons or other particles? Do different types of particles react differently to gravitational lensing? If there is a substance that fills the universe does it have measurable properties? Conductivity, Density... 100+ years ago Scientists called it "ether". What terms are they using today?