I've heard much talk of dark matter and the universe being more massive (according to calculations) than it should be given the amount of observable matter in it. Or something to that effect. But Im thinking that since blackholes pretty much consume matter and gain mass and are unobservable to us other than their gravity's affect on the surrounding matter, that they would be my first guess as to where that extra mass is. Especially since - I would assume - there have been blackholes consuming whatever matter presented itself to it for billions of years now. i could see the mass of the amount of matter consumed to be quite massive by now. Why have they been ruled out and Dark Matter theorized?