By now, I've listened several times to Brian Greene's talk about the OPERA experiment. And, although I largely agree with him, there's one nagging question I have: Gravitation was, at a time soon following the Big Bang, a repulsive force. The existence of "Dark Energy" suggests the persistence of repulsive gravitation in our universe. If gravitation was once, and, within certain contextual constraints regulating our universe, apparently still is, a repulsive force, does it not make perfect sense, well within the bounds of Einsteinian Special Relativity, that particles under the influence of "Dark Energy"/repulsive gravity would, although possessing mass, exhibit the characteristics of RELATIVE negative mass, with respect to our observational perspective? Relative negative mass would REQUIRE relative superluminal velocity of particles under the influence of repulsive gravity/"Dark Energy". Am I an idiot? (I sure feel like one right now!!!) Does anybody have any other idea?