Ever considered galactic sterilization?

This is a story from slashdot.

Megaport writes
"Promoting his new series on the Discovery channel, Stephen Hawking has given an interview to the Times in which 'he has suggested that extraterrestrials are almost certain to exist but that instead of seeking them out, humanity should be doing all that it can to avoid any contact.' He says, 'I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach. ... If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans.' Personally, I've always thought that the indigenous people of the world really had no chance to avoid contact here on such a small planet, but is hiding under our collective bed an option for humanity in the wider galaxy?"


This was a comment to that story by Dr. Spork

I come to the same conclusion as Hawking - that we should try to be a quiet civilization - but not for the same reasons.

The fact that we haven't detected advanced life in all of our SETI searching, and the fact that our solar system has not been visited by an alien probe (see Fermi Paradox) is some evidence that our galaxy has a "sterilizer civilization" - which is a pretty straightforward concept.

If two civilizations begin interstellar colonization in our galaxy, their spheres of expansion are bound to intersect in the future. As they will largely be competing for the same resources (sources of energy differential), some sort of conflict is inevitable. But a conflict at this scale would be so horrible that any reasonable civilization would want to avoid it at all costs. This reasoning makes me think that any suitably advanced, reasonable civilization will be a sterilizer civilization: For the moral purpose of preventing great suffering, they will sterilize any technological civilization before they begin their interstellar colonization. Being rational, they will do this in the most efficient way possible: They will send a robotic probe which will duplicate itself in our solar system, and this autonomous army will wipe out all technological life and monitor our system to make sure that none re-emerges. Since sending even a small payload at great interstellar distances requires great energy, the rational sterilizer civilization will choose a speed for the probe that will bring it to its target safely before their interstellar colonization phase begins, but not much earlier. It is quite possible that such a probe is on its way to us right now, but won't arrive for another thousand years.

On the very unlikely scenario that we are somehow the first technological civilization in our galaxy, I think that we have an ethical obligation to become a sterilizer civilization ourselves. Everyone now wishes that somebody killed Hitler when he was a baby. It would have prevented great suffering. Like Hawking, I think it's inevitable that if contact is allowed to occur between two colonizing civilizations, the result will be catastrophic on a scale that will make the casualty count of a nuclear war seem like a rounding error. So of course there are ethical downsides of sterilizing a budding, intelligent civilization, just like there are downsides to killing the still-innocent baby Hitler. But I think the refusal to do this would be far more monstrous. The costs could be mitigated by meticulously recording all information about the culture and biology of the extinguished life, or perhaps even saving some specimens who will be safely contained in some sort of a galactic zoo.

So how should we react if there is a sterilizing probe on its way to get us? We have to begin our interstellar colonization before the probe gets here. I don't think it makes much sense to try to raise up a defense, because we can't even guess at the mechanism of such a probe. One thing it might do is to create a tiny black hole and drop it into the sun. (Or perhaps the probe just is a small black hole set to collide with the sun in a thousand years or so.) At this point, we are still a very vulnerable civilization, and will remain so until we have covered a substantial part of the galaxy. Also, we should be working hard on the technology for an effective sterilizer probe, just in case SETI does eventually reveal an alien civilization. I know it's "no fun" to kill aliens before we ever meet them, but I think the ethical costs of not doing so are unacceptable.