Ghosts - total bull. And I say that *completely* unbiasedly.
Physics - probably bull too, but it's more plausible than ghosts. I suppose there have been those police stories, but TV always lies about things.
Aliens - totally out there. Most likely not in the forms that TV/book/blah make them out to be, but yeah, totally exist. If they are, I hope they aren't smarter than us. Random chance of birth or not, Go Team Human!