I'm afraid you are so badly wrong and the "system" we exist in, is a multiverse, and that multiverse is infinite... Just because you can not prove it, does not mean it isn't there... We do have members of other interplanetary civilisations visiting us, but their intelligence level is so advanced that they see us as an interesting ant, no need to worry about aliens killing us as there are better planets that are uninhabited out there for there building resources, scientific programmes and individual desires... So you should work on that basis and not just our Galaxy... You should also work on the alien systems invented by these civilisations, which includes the travel mechanics enabling the exitance of a multiverse traveller and their craft... BUT...… As we know, a multiverse "well anything is possible there isn't it due to the size of infinity and the number of civilisations existing?"..... Plus evolution also needs technology for advancement which includes humans becoming androids or a "good Borg species"..