yeah man, coral castle! crazy shit
dark matter -- the notion that heretofore undetectable matter provides the extra gravitational "umph" needed to keep galaxies from flying apart (which our calculations predict given their rotational velocities) -- has been a monkey on the back of physics since inception, and we're not really getting any closer to unraveling the mystery of why gravity doesn't act like we expect it to. some are beginning to think dark matter is and always was a theoretical crutch to keep us comfortable in our "knowledge;" that the problem lies rather with our understanding of gravity which is obviously not comprehensive enough to account for our observations:
Dark Matter: The Plot Thickens