[Tichy]

I think I just found a possible alternative explanation, which given the odds might actually be very probable: there is one situation in which aliens might not want to show themselves to us. That is, if we are an experiment that their interference would mess up. Perhaps they are just studying some sociology and evolution theory with earth. We already are the result of the "von Neumann probe".

We are not seeing any other aliens because our creators (not god, but some aliens) are so powerful that they destroyed them or kept them away.

Well, just a random thought I had after reading the article.

[r7000]

Maybe the idea of messing with anything interesting is unthinkable. If you were very advanced the only thing interesting would be stuff that originated elsewhere (and mathematics). The thought of "contaminating" it would be immoral. Even terraforming a lifeless planet or moon would seem like a waste as you would be destroying information.

[ks]

I've thought about that too. What if there is a civilization out there that are millions of years ahead of us. What can't they do?

We think in human terms, but they might not have the need to spread to every planet. But they may want to stop other civilizations, because they can become threats to them. Perhaps they just monitor the galaxy and stops other civilizations from spreading too far?

That could also explain why UFO observations have increased so much after WWII. When they noticed that we could make nuclear bombs, we were put on the "no fly list" :-)