I don’t usually post just to link to articles, but this one was particularly intriguing: Alone in a Crowded Milky Way.

Executive summary: the author and his colleagues did some modeling of the expansion of interstellar civilizations through a segment of the galaxy. They made some fairly conservative assumptions – STL travel only, how many planets would be worth colonizing, how long a given planetary civilization would be likely to survive. The result was that space-faring cultures tended to form “archipelagos” in interstellar space, leaving vast regions unvisited for many millions of years at a time. The limiting factor was imposed by stellar cartography – the arrangement of interesting planets among a population of stars that move over time.

This strikes me as a similar approach to Geoffrey Landis’ percolation theory, and yields similar results. In either case, we get a galaxy that could be full of interstellar-capable civilizations, and yet one in which many habitable worlds (like ours) might appear unvisited at any given time. It’s a sophisticated solution to the Fermi Paradox, and one which avoids nightmare scenarios.

One insight the authors of this article mention, which I hadn’t considered, is that even if Earth had been visited – or even colonized – at some point in the distant past, we might have no way of knowing that. My own models for putative galactic civilization might stand to be relaxed a little. That might go on the list for some deeper research, if and when I get back to working on space-opera projects.