Pvjinflight wrote on Aug 2^nd, 2012 at 6:01pm:

Yes we definitely are not alone in the universe, I don't believe that earth would be center of everything and only place with life as there are so huge amount of planets where life could have also developed. But I think if there was any life from outer space around this exact planet we would know it already, so honestly I don't really believe that any of these seen UFOs have been actual aliens.

Technically, we have no indication, nor any true scientific proof that life may exist outside of earth, or our solar system. The fact is, whatever force caused life to begin (which shall forever be a mystery) it is quite possible that those conditions caused life to sprout here, and that it has not occured elsewhere in the universe. The nearest star is 8 light years away (proxima centauri) and it has no planets, therefore nowhere for life to exist. The nearest star with planets is probably 50 light years away, and those planets may not have the right life-supporting conditions. Plus, if life was first generated here, it would takes millions of years for any vessel, be it comet or asteroid, to make it to the next habitable location, and all that time is in the lifeless, near absolute zero conditions of deep space. I believe it is entirely possible that no life exists outside of our solar system, and if there is, the chances of that life being as intelligent or more than humans is incredibly slim. Take the 8.7 million species projected to live on earth, only one out of 8.7 million is intelligent enough to do what we do. Now say there is another race outside of earth just like us, or more intelligent, why would they invest their resources and hundred of thousands (to millions) of year traveling across the expanse of lifeless space, only to reach earth, flash by in a few minutes, and leave? That is the question. That is why I think they don't exist. Lightspeed travel is impossible for living beings, therefore the time spent is to great for any intelligent beings to not stop here, and make contact, or at least linger to observe.