I have a very mundane reply to this.
Us hairless apes, with our primitive technology and awful bureaucracy, have been able to detect extrasolar planets, some of which are terrestrial (not
gas giants, but rocky).
Also, we are planing on increasing our ability to detect terrestrial planets in the near future.
This is current technology. It isn't sci-fi or magic.
Without our distracting bureaucracy, politics, and war, this technology could even further increase our ability to see life sustaining worlds.
By launching four of these TFPs and placing them in solar orbits, it would give us a tremendous quadroscopic view of the stars we are examining.
I'm theorizing that any species, in a direct line of sight of Sol, that has gotten past this military-industrial hurdle that we currently face, has
almost certainly spotted earth.
AND, for every century's worth of technological advancement these "aliens" may have achieved, it becomes only more and more probable that they have
seen this planet.
I'm also assuming that life sustaining planets are a bit more rare than gas giants, so if aliens have seen earth, they most certainly have tried to
visit, if for nothing more than curiosity.
ERRRR... the woman is distracting me as I rant...
I'll finsih quickly and then I'm going to the gym, maybe I'll explain my insane point of view more later.
I've thought about this a lot and I've come to two conclusions. Either life is completely unique to earth for some yet-to-be understood reason.
Or, life is quite common and robust, and therefore advanced civilizations have already visited us (that's a big leap, but I've thought about it a
I reached this conclusion from a general relativistic point of view; I haven't even considered fringe science in my conclusion.
FTL of any kind only ups the ante even further.