Searching the Sky

Thursday

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When Frank Drake first formulated the eponymously-named Drake equation the number of planetary systems in the universe (the second term in the Drake equation, f_p) was an unknown among other unknowns. Now we are rapidly approaching a scientifically-based quantification of this once unknown number. We now know that planetary systems are common, and moreover that planetary systems with smallish, rocky planets in the habitable zones of stars are relatively common. (Cf., e.g., Earth-Like Worlds “Very Common”)

As soon as we reached a level of technological and scientific expertise that made the search for exoplanets practical, we began to find them. The most recent exoplanet discoveries, and the recent announcement that planets and planetary system are common, are primarily due to the NASA Kepler mission. According to the NASA website, the Kepler mission was…

“…specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets.”

In this, the Kepler mission has been wildly successful. But in order to get to the point at which our civilization could conceive, design, build, and operate the Kepler mission we had to pass through thousands of years of development, and before our civilization developed to its current state of technological prowess, it took terrestrial biology billions of years of development to arrive at organisms capable of creating a civilization that could develop to this level.

Contrast the experience of Kepler’s exoplanet search with the experience of SETI, the search for extraterrestrial intelligence. What did not happen as soon as we began searching for SETI signals? We did not immediately begin hearing a whole range of intelligent extraterrestrial signals, which would have been a result parallel to the immediate successes of the exoplanet search (immediate, that is, in the technological zone of proximal development). Both Kepler and SETI are searches of the sky. The Kepler mission gave nearly immediate results; Frank Drake conducted the first SETI study in 1960. Drake found only an eerie silence, and ever since we have only heard an eerie silence. Once the technological threshold of exoplanet search was reached, the search immediately discovered its object, but once the technological threshold of SETI was reached, the search revealed nothing.

Please understand that, in making this observation, I am in no sense criticizing SETI efforts; I am not saying that SETI is a waste of effort, or a waste of money; I am not saying that SETI is wrongheaded or that it is not a science. On the contrary, I think SETI is interesting and important, and that includes the fact that SETI has found only an eerie silence — this is in itself important and interesting. We have discovered radio silence, except for natural sources. This tells us something about the universe. If there were a truly predatory peer civilization in our region of the Milky Way, it would be expected that they would go to the trouble to broadcast their presence to the universe, in hope of luring unsuspecting peer civilizations. Like Odysseus having himself strapped to the mast of his ship so that he could hear the song of the Sirens while his crew rowed on oblivious, their ears stopped with wax, we would have to listen to such signals restraining ourselves from rushing toward that fatal lure.

Don’t expect to find anything like this close to home.

What we now know, as a result of SETI’s discovery of the eerie silence, is that METI (messaging extraterrestrial intelligence) beacons are not common. If METI beacons were common in the Milky Way, we would have heard them by now. There may yet be METI beacons, but they are not the first thing that you hear when you begin a SETI program (unlike looking for exoplanets and finding them as soon as you have the capability of looking). If METI beacons exist, they are rare and difficult to find. I think we can go further than this, and assert with some degree of confidence that there is no alien “super-civilization” in our galactic neighborhood constructing vast mega-engineering projects and pumping out high-power EM spectrum emissions that would be easily detectable by any technological civilization that suddenly had the idea to begin listening for such signals.

James Benford has argued that METI beacons entail prohibitive expense, and has argued against unregulated terrestrial METI efforts.

I wrote above that SETI and exoplanet searches are sensitive to a technological threshold. We passed the SETI threshold in the 1960s, and we have passed the exoplanet search threshold in the first decade of the twenty-first century. There is a further technological threshold, which is also an economic threshold — the ability to detect the unintentional EM spectrum radiation “leakage” from technological civilizations that have not had the interest or the resources to establish a METI beacon, but which, like us, are radiating EM spectrum signals as an epiphenomenal expression of our industrial-technological civilization. I say that this is also an economic threshold, as James Benford and colleagues have taken pains to point out the expense associated with establishing a METI beacon. (This is something I discussed in my Centauri Dreams post SETI, METI, and Existential Risk; James Benford responded on Centauri Dreams with James Benford: Comments on METI; my post on Centauri Dreams, along with responses from Benford and from David Brin, received quite a few comments, so if the reader is interested, it is worthwhile to follow the links and read the ensuing discussion.)

If METI is “shouting to the galaxy” (as James Benford put it), then the unintentional leakage of EM spectrum radiation of industrial-technological civilization is not shouting to the galaxy but rather whispering to the cosmos, and in order to be able to hear a whisper we must listen intently — holding our breath and putting a hand to our ear. Whether or not we choose to listen intently for whispers from the cosmos, we have not yet reached the developmental stage of civilization in which this is practical, though we seem to be moving in that direction. If we should continue the trajectory of our technological development — which, as I see it, entails both increasing automation and routine travel between Earth and space — such an effort will be within our grasp within the coming century.

Advanced industrial-technological civilizations will, by definition, know much more than we know. Their science will be commensurate with their technology and their engineering, since their civilization, if it is an industrial-technological peer civilization (and in so far as industrial-technological civilization is defined by the STEM cycle, which I believe to be the case), will experience the advance of science joined inseparably to the advance of technology and engineering. What would they do with this epistemic advantage? Such an epistemic advantage presents the possibility of SETI and METI asymmetry. We have an asymmetrical advantage over civilizations at an earlier stage of development, as older industrial-technological civilizations would have an asymmetrical advantage over us, with the ability to find us while concealing themselves.

A Pythagorean geoglyph based on Gauss’ idea for signaling to ETI.

The developmental direction of industrial-technological civilization as defined by the STEM cycle means that any advanced industrial-technological civilization will be “backward compatible” with earlier forms of technological communication. We might not (yet) be able to build a quantum entanglement transmitter in order to communicate instantaneously over cosmic distances (even though we can conceive the possibility), but an advanced peer civilization will be able to listen for our EM spectrum radiation leakage, in the same way that we today could continue to look for signs of ETI compatible with earlier stages of industrial-technological civilization. Karl Friedrich Gauss suggested geometrical shapes laid out in wheat in the wastes of Siberia to get the attention of extraterrestrials, while Joseph von Littrow suggested trenches filled with burning oil in the Sahara. Interesting in this context, although our civilization had the technology to pursue these methods, no one undertook them on a large scale.

When, in the future, we have the ability to image the surface of exoplanets with large extraterrestrial telescopes, we could look for such attempted signals within the capability of less developed civilizations to produce, such as those suggested by Gauss and Littrow. But when it comes to advanced peer civilizations, we don’t have the knowledge to know what to look for. The more advanced the civilization, the farther it lies beyond our civilizational zone of proximal development (ZPD), but the more advanced a civilization the earlier it would have to have its origins in the history of the universe, and at some point in the development of the universe (going backward in time to the origins of the universe) it would not be possible for an industrial-technological civilization to emerge because if we go far enough back in time, the elements necessary to an industrial-technological civilization do not yet exist. So there seems to be a window of development in the history of the universe for the emergence of industrial-technological civilizations. This strikes me as a non-anthropocentric way of expressing one formulation of the anthropic cosmological principle (and an idea worth developing further, since I have been searching for a formulation of the anthropic cosmological principle worthy of the name).

In an optimistic assessment of our place in the universe, we could hope that any substantially more advanced civilization could serve as the “more knowledgeable other” (MKO) that would facilitate our progress through the civilizational zone of proximal development.

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