OT:Why Aliens dont come here

[dmm]

Arkcon said:
...if there was another rock oxygen planet here, how close would we be to establishing a colony? We don't have near the technology now, but if we had the incentive, would we be closer, or be there already?

Interesting question. Some thoughts:
1) You assume that it is possible to have two stable Earthlike planets around one star. May not be true.
2) Is there life on that other planet? The dominant opinion nowadays seems to be that liveable planets will automatically have life. This is by inference from Earth, where life exists in every ecological niche that is conceivably liveable (as well as in many niches that we thought were not liveable). However, the data from Earth may be unrepresentative.
3) Is it possible for a planet to be livable (for humans) without an already-existing biosphere? I would guess "no."
4) If there is a biosphere on that planet, would it be right for us to go there at all, much less colonize it? Would orgs like the Sierra Club put up a huge fight to prevent it? My guess is that, regardless of morality or scientific ideals, there is no way in the world that you could keep nations from setting up research colonies at least and that these would gradually become intrusive. Example is Antarctica.
5) If there is a biosphere on that planet, would it be compatible with us? It could be amazingly similar, yet the amino acids and sugars might all have the wrong chirality. (Hmmm...none of it would be digestible. Earth Lite?)
6) What about the problem of non-indigenous organisms being accidentally transferred? And you thought zebra mussels and kudzu were bad!
7) I think we have the technology now, and I think we'd colonize it. Absolutely.
8) Someone should invent a computer game where our solar system captures a liveable planet (or two). Like "Alpha Centauri," but the home planet is still very much part of the game. (Anyone know if AC can be modded to do that?) Actually, "Conquest of the New World" was somewhat like that, except that of course it was historical not sci-fi.