I updated the OP to be a bit more correct, I left the opening statement with the word "weight" for the sake of simplicity, but took care of my summary statement. I was talking with a friend in the Secrets of Destiny about the shadow realms (like VoG, CE, and other "pockets" of darkness), and there's some speculation that there might be a realm of Light, and that the Traveler is actually just a conduit to this realm, not the actual source. So, I know very little about physics, but maybe this mass is being used to tear a very small hole in the realm of light...