I'm not sure if my interpretation is correct, but this Dirac Sea interpretaton does as far as I understand this, tell us that every energy level from -infinity to a certain energy level E<0 is filled with anti-particles. And this should be true for every single location in the universe. If this would be true, how is it possible that we can even travel through a vaccuum? I mean, not only the outer space vaccuum but even the vaccuum between two molecules here on Earth. If every single spot containts more than an infinity amount of -for instance- positrons, and these particles have a mass greater than zero, we would have an infinity mass density in every single location, which should make it impossible for any motion. So how is motion possible if the dirac sea is true?