[ericb]

I have a sci-fi inspired theory that as a civilization advances, it modifies itself such that it's mental processing speed and speed of communication become faster. At a certain point, species at other speeds have less to offer and communicating would be impractical as emitting a signal at our speed would involve what would seem like eons of effort to them. Due to the speed discrepancies, they'd mainly prefer talking to themselves.

One way or another, the "sends radio waves into space hoping for contact" phase is probably very short. The possibilities for what phases come next are not all bad, but whatever the "usual" is, it probably doesn't involve sending radio waves out anymore. It's possible the next step is to evolve into something that wouldn't like talking to us very much. Maybe that's not bad.

[ph0rque]

Charles Stross explores a very similar thesis in Accelerando (http://www.accelerando.org): the civilization needs such intensive bandwidth to continue functioning "normally" that the distance between galaxies is too large to support both the bandwidth required and intergalaxical expansion (it's been awhile since I read it, so correct me if the details are fuzzy).

[andrewl]

ericb, your comment about mental processing speed and speed of communication makes me think you would enjoy "The Mote In God's Eye", by Larry Niven and Jerry Pournelle. I thought their concept of an alien race was quite original.

(Anybody else reading this, human or alien, may also enjoy the book.)