[Rockingham]

Under observation by advanced telescopes, our solar system would beckon as having an unusually stable set of planets orbiting in resonance. The Earth would be especially attractive because of its abundant water and green chlorophyll indicating the presence of life.

I believe that the reasons to visit Earth are: (1) scientific curiosity; (2) the potential for useful DNA and whole biological specimens; and (3), as a waystation and base for further exploration. Similar reasons impelled and guided exploration throughout human history.

[sphinx]

Scientific curiosity would indeed be the likely motive … assuming that alien rationality parallels our own. An alien race capable of interstellar travel would presumably have solved its own resource problems long before it reached Earth. If such a race were capable of mining Earth, it would be capable of mining other planets and asteroids. Unless we hypothesize that our alien visitors would be very near neighbors — quite possible — and that Earth is their nearest port of call, resource issues seem an unlikely motivation.

[jmacusa]

An advanced civilization studying us would realize, as I said, our predilection to destroy ourselves. They would also know, or very soon find out we would most likely react to their contact with skepticism at the least and out right hostility at the worst.

They would also no doubt know we are in possession of not only nuclear power for the generation of electricity and peaceful uses but we're in possession of nuclear weapons, that we have used nuclear weapons in the past and if we're threatened we will fight. If there is an advanced civilization(s) out there and most assuredly there are , they know where we are. Whether or not they have been here before in our early history for myself I doubt it very much.