Read the "Prime Directive", cadet! Hmm..., maybe your rank is not high enough to read that... Please Register or Log in to view the hidden image!
They are not here because , we are very smart, the moment they show up we will steal all theirs technology, and claim our share of space that they might be using. What may have took them millions of years we may have developed it in 300 years , that will be a scary thought for them. Depends on theirs neurobiology. Think about it, if a small alien ship lands in middle of live olympics games and is greeted by humans and never shows up again in say next 100 years. In that time we at SciForums would have sorted out most of the technologies that we saw on TV. We will get the most right directions to fund our research, and in a very short time we may become the next big headache for them thats my theory BTW.
My theory is that we most likely appear, to any aliens that have mastered interstellar travel, as we see bacteria or any similiar stuff in petri dishes.