astronomy by FAR. cmon it's SPACE, and how it works/exploring it. To me that is the ultimate form of science, because to know who we are, we must first know where we come from.

on a sidenote - does space end? whats at the end? how did we end up here? where is foreign life? and finally, will we have the hotel in space soon??? :P

honestly though, its just so unexplored and unknown.