Actually, I recall an old Machian reference to this, so I will not claim it as my idea. In it, he said pretty much the same thing. I have no idea what source I was reading at the time. I do recall it was a quote in a text by another author, whether in a journal, textbook, or magazine..I remember not. Perhaps someone else does. But like you, I have realized for a long time the vacuum is not empty, with the principal entities being the , the local deformation of Minkowski space-time, the neutrino sea and the zero-point radiation..not necessarily in order of importance. Pete.