Where does the universe end?

There are so many questions.. such as are there ghosts, ufos, bigfoot, and to me the biggest question........when does the universe end? Think about it, if the universe is trully as big as it is then there must be some other life from out there. It seems like you would have to be ignorant to think that we would be the only ones to be living in such a large place. Other civilizations could be thousands of years more advanced then us or thousands of years behind. When i really get to thinking about it it creeps me out. Let me hear your thoughts or experiences on any of these subjects I have mentioned