Is there a ‘Galactic Club’ of civilizations to which our species might one day deserve admission? If so, the club’s members are being mighty quiet about their existence. But David Schwartzman (Howard University) thinks it might be out there. In that case, he finds three possible explanations for the ‘Great Silence,’ our failure to detect any signs of extraterrestrial intelligence in the last fifty years. He rejects the first, the notion that we are alone in the galaxy — life is, in his view, all but inevitable in the universe, and he’s keen on the idea of high levels of intelligence developing on many worlds, as he tells us in this article in Astrobiology Magazine:
I have argued that encephalization – larger brain mass in comparison to body mass — and the potential for technical civilizations are not very rare results of self-organizing biospheres on Earth-like planets around Sun-like stars. Biotically-mediated climatic cooling creates the opportunity for big-brained multicellular organisms, such as the warm-blooded animals we observe on our planet. Note that several such animals have now been shown to pass the “mirror test” for self-consciousness: the great apes, elephants, dolphins and magpies, and the list is growing.
The second explanation is that the advanced civilizations of our galaxy are simply unaware of our existence. But this seems unsound as well. Assume that but a single planet among the huge number of Earth-like worlds Schwartzman assumes fills the galaxy becomes home to an advanced technical civilization, one capable of spreading among the stars at sub-light speeds. Such a civilization would have had billions of years to develop and expand before life appeared on our planet, and if it set out to build the Encyclopedia Galactica by using Bracewell probes, it would have placed surveillance stations throughout the galactic disk. He’s careful to note that no faster-than-light technologies are assumed in any step of this expansion.
Back Into Quarantine
We’re left with option three, which is that the ‘Galactic Club’ is avoiding communicating with us on the grounds that our culture is too primitive, the so-called ‘quarantine’ explanation. Now you can read what you like into the notion of ‘primitive’ — the article is freighted with the author’s assumptions on the matter. The key question is this: IF an extraterrestrial civilization is aware of us and uncommunicative, what ramifications would this have for our SETI search? For it seems obvious that a culture explicitly avoiding contact will not set up a beacon specifically targeting our planet. Thus the basic premise of most observational SETI disappears.
Paul Davies has a take on this in his new book The Eerie Silence (Houghton Mifflin Harcourt, 2010), one that Schwartzman examines and I’ll also quote here:
“…we should search for any indicators of extraterrestrial intelligence, using the full panoply of scientific instrumentation, including physical traces of very ancient extraterrestrial projects in or near the solar system. Radio SETI needs to be re-oriented to the search for non-directed beacons, by staring toward the galactic center continuously over months or even years, and seeking distinctive transient events (‘pings’). This ‘new SETI’ should complement, not replace, traditional radio and optical SETI.”
That interesting shift of strategy is well examined in Davies’ book, which I can’t commend too highly. But Schwartzman’s notion is that there won’t be any non-directional beacons, either, assuming an extraterrestrial civilization that does not alert others to its presence. His answer, first proposed back in 1988 along with the radio astronomer Lee Rickard, is that SETI should go after leakage radiation from late-stage primitive civilizations like our own. Leakage radiation is very hard to detect and would presumably only appear in a brief window in a culture’s evolution, as appears to be happening in our own, but Schwartzman believes such a search at galactic scale could be productive:
The technical requirements for a galaxy-wide search are dictated by the size of the radio telescope, with the detection range proportional to the effective diameter of the telescope. A large enough radio telescope situated in space could potentially set meaningful upper limits on the rate of emergence of primitive Earth-like civilizations (‘N/L’ in the Drake equation), without ever actually detecting the leakage radiation of even one ET civilization.
The Aspirations of Conjectural Beings
That, of course, would be useful information, but unfortunately the 1988 paper goes into the costs of creating the needed dish, a telescope with a diameter of 500 kilometers that — in 1988 dollars! — weighs in at $10 trillion. It is not a project Schwartzman expects to be implemented, for obvious reasons, although he opines that a ‘newly mature’ world might one day choose to build it. But let’s assume that $10 trillion adjusted for inflation is too much to ask. We’re left with Davies’ notion (and that of Michael Papagiannis before him) that evidence of a Bracewell probe might be lurking in our own Solar System, if we have the wherewithal to find it.
Short of making that detection, contact with the ‘Galactic Club’ seems to be a matter of waiting for the Club to contact us; i.e., restructuring our own civilization so that extraterrestrials will find it to their liking. It’s a prospect unlikely to satisfy those with the restless urge to push SETI to its limits using buildable technology. And it’s hard to know how to re-structure a civilization so that it would satisfy the entrance requirements to a club populated by extraterrestrials whose existence is purely conjectural. Schwartzman thinks an end to war and poverty will do the trick, laudable goals, to be sure, but he assumes that ETI’s aspirations largely parallel our own.