According to my starry night software the sun passes though the galactic longitudinal equator on December 9, 2012 at 12:47:29 AM Eastern US Time. On that day absolutely nothing will happen. The world and solar system will continue to exist as they always have. There is no empirical evidence to state otherwise that something bad will happen. Other stars have passed though the galactic equator and nothing happened to them. The sun moves though the equator every 2 or 3 years and we are all still alive.