If aliens could come to earth, they would need some extremely high tech spacecraft; so high tech in fact that they would seemingly be quite far ahead of humans in technology. With that said, why would an alien come here? It would be like humans studying cavemen; less intelligent and less advanced. There are some people who study cavemen, anthropologists, but most people dont care about cavemen because they are inferior in many ways. The only thing that makes sense to me is if it was humans from our future looking back on history like a tv show. And another seperate but related comment. If our radio signals have only reached about 100 stars thus far and we are waiting to hear back from them- does this not make sense to anyone else? The second humans established radio technology, they would have been picking up alien radio signals if they were being emitted on purpose or not. Thus i conclude that aliens are not using radio signals anywhere near earth; not only within the zone in which they could hear our signals, but far far beyond if their civilization was developed for a long time.