For the astronomers tasked with finding intelligent life elsewhere in the solar system, one of the most vexing questions is why ET is being so quiet. The Search for Extraterrestrial Intelligence (SETI) began in 1960 when astronomer Frank Drake spent 3 months scanning the cosmos for life, but in the 50-odd years since Drake's initial experiment, SETI astronomers have yet to find any convincing evidence that we are not alone.
The disappointment this lack of results has led to the creation of a controversial wing of SETI research known as METI (Messaging to Extraterrestrial Intelligences) or Active SETI. The basic idea here is that if the aliens aren't going to call us, we'll call them instead.
Although a handful of messages have intentionally been sent out into the cosmos over the last half-century, ranging from 8-bit drawings to the entirety of Craigslist, most SETI research institutions do not fund active SETI projects. Moreover, in February of 2015, a number of leading SETI scientists published a letter listing the perils of METI and calling for a global consensus before any sort of message is sent on behalf of spaceship Earth.
The researcher's concerns are well founded: as detailed in a paper posted to arxiv last week, a critical analysis of the leading arguments for and against METI found that the project is probably not a good idea, going so far as to call METI "unscientific and potentially catastrophic."
Authored by John Gertz, President of the Foundation for Investing in Research on SETI Science and Technology and chairman at the SETI Institute, the paper begins by outlining the main arguments in favor of METI. In the first place, there's the fact that all non-active SETI projects to date have failed to find evidence of intelligence elsewhere in the universe, which suggests that it might be time to try a new approach. Then there's the argument that Earth has already been leaking radio waves into space for decades, potentially broadcasting our position to extraterrestrial intelligences. If we've already blown our cover, the thinking goes, there's no harm in focusing our transmissions in a more organized search.
Yet as Gertz points out, there are a number of problems with the METI-ists arguments. In the first place, we don't know anything about the alien civilizations we are contacting—perhaps we are saying hello to a hyperviolent and superintelligent alien race. If the history of our own planet has taught us anything, the contact between two civilizations when one is technologically advanced and the other comparatively primitive usually results in the extermination of the latter, so perhaps it's best to wait and listen.
The most forceful argument in favor of METI, that we've already blown our cover by leaking radio waves into space, was ironically disproven by SETI Institute chief astronomer Seth Shostak, who is skeptical about the danger posed by active SETI. As Shostak has pointed out, the leakage from terrestrial radio transmissions would be so faint that it would be essentially impossible for an alien civilization to detect them from the interstellar distances where SETI researchers are looking for life.
Finally, there's the issue of who gets to speak on behalf of Earth and what they get to say. Although the International Academy of Astronautics has drafted a protocol forbidding sending messages into outer space, it is not enforceable by law, so anyone with access to a radio telescope can say whatever they want to the universe without any legal repercussions.
Gertz argues that because of the large number of unknowns about who we're contacting, the huge stakes involved in contact (namely, the existence of humanity), and the haphazard method of going about sending messages, the METI enterprise remains "unscientific and potentially catastrophic."
So for the time being it appears most SETI astronomers are in agreement that trying to contact aliens is probably a pretty bad idea, although it's still one worth thinking about. Due to recent donation boosts for SETI, Shostak has predicted we may hear from aliens inside of 20 years, and if he's right, the question of what to say in reply may ultimately become the question of our generation.