Hey guys, first post here. I'm just starting to learn physics at the college level, so keep that in mind. While doing some reading on dark energy and dark matter, something occurred to me that I'd never had answered before. Do virtual particles exist long enough to have even a slight gravitational effect on other things? If so, then couldn't the acceleration of galaxies be due to the fact that there is much more empty space on the "outside" of them then there is matter on the "inside"? This empty space would contain countless virtual particles, and if they had any gravitational effect at all, then they would eventually have more of an effect than the matter trying to bring everything together. Does this sound valid at all, or am I totally missing something?