Hello all, I'm currently doing a research paper on the coalescence of two Supermassive black holes (Sagittarius A and the Supermassive black hole at the center of the Andromeda galaxy) and have come across some difficult quandaries. First since (to an outside observer) nothing ever comes in contact with a Supermassive black hole's Schwarzschild radius, or any black hole's Schwarzschild radius for that matter, how can two black holes coalesce? Second, if they can coalesce then is it possible to calculate the minimum mass required for an object falling into a black hole to pass the Schwarzschild radius (to an outside observer). Third, do gravitational waves have interference patterns? Finally I've heard that gravity is created by matter in motion is this true?