The answer to this question for me at least is incredibly obvious, especially in light of all the recent astronomical observations of planets around other stars and considering the huge estimated numbers of planets similar to earth in the universe. It's a matter of probability! Thus far of course, scientists have no direct proof of life outside the Earth, but what do people think? Y or N?
While I'm certain, by simple probability, that intelligent life exists elsewhere in the universe; I'm also comparatively certain that it has not visited us, simply by the distances involved.