In a new paper (put putting forth an old argument) John Gertz argues that attempts to send deliberate signals for detection by alien civilizations is “unwise, unscientific, potentially catastrophic, and unethical.”  His rather caustic assault on METI-proponents is a pretty good summary of the extreme METI-opponent position. (METI = Messaging to ExtraTerrestrial Intelligences).

One thing that caught my eye that I had not heard before is that he obliquely proposes that something like an ethics review board weigh in on any powerful transmissions made by Earth.  He specifically mentions Arecibo radar pulses used to probe Solar System objects:

The asteroid detection radar problem is very easy to fix by adopting a standard of best practices that includes a provision for muting the radar during moments when the target occults a nearby star or transits the plane of the Milky Way.

The agent of our destruction?

I may be behind the times here, but this is the first time I’ve heard that the planetary science community should consider the ethical implications to the planet for their observations (as opposed to just the ethical implications of the deaths of any birds that happen to fly above the dish during transmission).

But Gertz interestingly does not mention laser AO programs, which send powerful laser beams to some of the nearest stars routinely.  Indeed, Kipping & Teachy recently showed how relatively powerful lasers from other worlds would be easily noticed as artificial signals even with our present technology, and searches for pulsed laser emission is one of the most promising SETI routes we have.  Tellis & Marcy have searched for lasers as weak as tens of Watts coming from tens of AU away from nearby stars.  I haven’t run the numbers, but it would surprise me if our laser AO systems, pointed right at nearby stars, were not detectable by an advanced alien civilization as being obviously artificial.

So my honest question to Gertz and other METI opponents is whether we should seriously be setting up review boards for laser AO and planetary radar?  What about the powerful arctic radars used to look for ICBMs that sweep across the sky? How powerful or coherent must a transmission be before we consider its ethical implications?

As a METI agnostic, I don’t have an answer to these questions; I’m genuinely curious to have this discussion.