[PatrickHenry]

The simplest explanation is that they are there, they know we are here, but they are leaving us alone until we become sufficiently civilized to be invited to join the Federation.

It's not that simple; because it is most unlikely that every civilization in the galaxy plays by the same rules. All it takes is one rogue civilization to break the rules.

[realpatriot71]

It's not that simple; because it is most unlikely that every civilization in the galaxy plays by the same rules. All it takes is one rogue civilization to break the rules.

Agreed. I've never liked the explanation that EVERY single E.T. civilization is leaving us alone because we are not "mature" yet. There is no possible way that EVERY advanced civilization has the same morals and ethics. In fact, if the universe knew what was good for it, it would destroy us before we destroy them.

We're either alone, ahead of the game, so far behind the game as to not see a trace, or (religious explanation) kept separate from the rest of the universe, by God, due to our corrupt nature.