They make it appear out of an infinitely dense soup of primordial matter, which expands into a bridge shape. Nobody has seen this happen though unfortunately. We are suppose to believe it because during the day the bridge expands, meaning if we reverse calculate the expansion rate, we can figure out how old the bridge is, and prove that it started out as an infinitely dense soup of primordial matter.
Does this reasoning sound familiar? It should. It is the exact same argument of Big Bang Creationism.