Why assume the universe is spreading, why not coalescing?

scientist think the universe is expanding because everything we can observe is moving further from us. though this could also be explained by observing the matter at the center of a galaxy. the gravity of a black hole is so strong that everything gets pulled in, and even stretched, similarly to what is going on around us. is it not plausible that we are heading into a black hole rather than expanding out from the big bang. mind you, i'm not saying this is fact, but isn't it just as probable as the current theory.