Searching the Sky

21 November 2013



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, fp) 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”)

Frank Drake

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.

Kepler neighborhood

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.

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.

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.

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.

civilizational ZPD

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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Grand Strategy Annex

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Day 4 – Congress Summary | Sunday August 18th, 2013

Day 4 of the Icarus Interstellar Starship Congress began with a presentation by science-fiction artist Stephan Martiniere and, because Monsieur Martiniere is an artist the audience was treated to a wide variety of his work. He told the story of his life in pictures, and linked it throughout to developments of the Space Age, which was an artful touch. …

After this Andreas Hein launched into a sober assessment of technologies necessary to interstellar flight in “Project Hyperion: Disruptive Technologies for Manned Interstellar Travel”. Much of what Mr. Hein presented were ideas that I had independently worked out for myself, describing the S-curve of technological maturity and how technological succession can extend this S-curve upward. Using these analytical tools, Hein assessed which technologies would be necessary to any interstellar mission, and which technologies might prove to be disruptive breakthroughs that rendered other technologies obsolete, ending with the suggestion that investments in technologies must be balanced across a spectrum of low risk/high probability of use and high risk/high gain technologies.

Next came Aaron Cardon, a doctor, with “Ideal Biological Characteristics for Long-Duration Manned Space Travel.” This presentation was much more interesting to me than I expected it to be, and suggested to me that designs of a long term interstellar mission would not be uniformly good or bad for human health, but rather that some starship design parameters may compromise human physiology while others may actually optimize human physiology. For example, Dr. Cardon stated that the circadian rhythm of the human body, if taken out of the context of our 24 hour rotation of the Earth may be closer to 26 or 28 hours, which an artificial environment could easily accommodate. Dr. Cardon also spoke about some of the psychological and sociological consequences of long-term missions — something covered in yesterday’s Odyssey presentation — including the dramatic shift that would need to take place in making the transition from an open frontier to prioritizing social cohesion, and how human intuitive heuristics may pose a risk in artificial environments. This talk gave me much to think about.

Rob Swinney gave an update of Project Icarus, which was the seed from which Icarus Interstellar originally grew, and discussed a number of design parameters of the starship project that is, essentially, the successor to the Daedalus project. This was followed by a presentation that was not on the program, Robert Kennedy on “Dyson Dots: Geoengineering is the Killer App.” Mr. Kennedy demonstrated how the interests of those seeking to mitigate anthropogenic climate change coincide with those seeking space industry, since space-based geoengineering could both address climate change and result in space industry. Specifically, we could construct a “Dyson dot” between the Earth and sun that would cast ever so slight a shadow on the Earth, marginally lowering terrestrial insolation. Moreover, the sun side of this Dyson dot could be covered in photovoltaic cells, which could generate a significant amount of electricity. Mr. Kennedy rightly noted that this approach is both scalable and reversible, which are real virtues in this context.

Jim Benford then presented, “Shouting to the Cosmos: The METI Debate” — METI being Messaging Extra Terrestrial Intelligence, in contradistinction to SETI or the Search for Extra Terrestrial Intelligence. Benford represented that school of thought that feels messaging ought to be discussed before it is undertaken on any great scale, and he contrasted this to the views of some in the field who support vigorous efforts to create a “beacon” and to attempt to send messages out into the cosmos. Benford rightly noted that today a wealthy individual could sponsor such a beacon and engage in METI without anyone to stop such activity. He suggested that international consensus, peer-reviewed publication of messaging details, consultation, and perhaps also an enforcement mechanism were in order.

Benford laid out the case both for and against METI, which was quite interesting to me. There were several stated assumptions and derivations from this assumptions, but each assumed something fundamental that was formative to the given position. Those in favor of METI believe that interstellar travel is impossible, while those opposed to unregulated METI assert that EM leakage cannot be detected. As it happens, I can’t belong to either camp because I disagree with both assumptions. I think that interstellar travel is possible, and I think that it is pretty clear that the EM radiation leakage (unintended signals) of a peer industrial-technological civilization can be detected.

Benford took the trouble to point out contradictions in the position of those advocating unregulated METI, but it seems to me that the glaring contradition in Benford’s position was that he asserted that EM leakage could not be detected, but he openly admitted that an advanced ETI could pretty easily build an antenna large enough and sensitive enough to hear us. The way he gets around this contradiction is something that I have thought about a bit, and I wrote about it last year in The Visibility Presumption. I want to go into this in a little more detail because it is so interesting.

Benford asked the rhetorical question of why ETI would be looking in our direction, in all the vastness of the cosmos. This is a rhetorical question so long as one maintains an unproblematic conception of the cosmological principle, but it becomes a live question and not merely rhetorical once the classical cosmological principle is called into question. Benford’s position perfectly exemplified the cosmological principle, i.e., that we occupy no privileged place in the cosmos, therefore there is no reason for ETI to point their antenna in our direction. I will not here dispute the idea of our not occupying a privileged cosmological position (advocates of the anthropic cosmological principle have spent enough time doing this), but there is a very different way to think about this that undermines the assumption of there being no reason for ETI to look in our direction.

Any peer civilization (i.e., any civilization like us) is going to be looking for peer civilizations because this intrinsic curiosity, at least in part, defines our civilization. In looking for peer civilizations, any advanced ETI will show at least as much ingenuity as we have shown in the search for ETI, since ingenuity of this kind is another quality that, at least in part, defines our civilization. We are now, at the present level of our technology, less than twenty years from the spectroscopy of exoplanet atmospheres, which could reveal markers of life and civilization. Any advanced peer civilization would have already done this (spectroscopy of exoplanet atmospheres), and they would have done this for the kind of planets that can host peer civilizations — small, rocky planets in the habitable zones of main sequence stars. In other words, ETI would have already by now done the spectroscopy of Earth’s atmosphere, and in so doing they would have focused in on the Earth as a place of great interest, in the exact same way that we would focus on an “Earth twin.” This would mean that they would focus all their best radio antennas on us, just as we could focus intensively on a planet that would likely host life and civilization.

It would be relatively easy for an advanced ETI of a peer civilization to build a custom antenna for nothing other than the possibility of detecting our EM leakage, since they had already identified us as a promising target for SETI and perhaps also METI.

In the question and answer session following Benford’s talk a new wrinkle in all this appeared. My co-presenter from Day 2, Heath Rezabek, suggested that someone opposed to unregulated METI could broadcast a counter-signal to a METI signal and essentially silence that signal.

The possibility of a counter-signal is an idea that can be scaled up, so that it is possible that what Paul Davies calls the “eerie silence” and David Brin has called the “Great Silence” is not something natural, but could be imposed or generated.

One metaphor that has been used to explain the eerie or great silence is that no one shouts in a jungle. This is plausible. If the universe is a dangerous place filled with predators, you don’t want to call attention to yourself. But it is just as plausible that everyone is “shushed” in a library as that everyone keeps quiet in a jungle, and therefore it is just as plausible to think of our universe as a library as to think of it as a jungle.

And with that discussion I had to leave the 2013 Icarus Interstellar Starship Congress at noon in order to catch my flight back to Portland.

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My co-presenter Heath Rezabek and myself on the final day of the Icarus Interstellar Starship Congress.

My co-presenter Heath Rezabek and myself on the final day of the Icarus Interstellar Starship Congress.

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Here is an incomplete schedule for the day’s events (incomplete because Robert Kennedy’s presentation is not mentioned below.

8:30am Coffee
8:45am Introduction to Day 4
9:00am Keynote: Stephan Martiniere, “FarMaker Speed Sketch Awards”
9:45am Presentation 1: Andreas Hein, “Project Hyperion: Disruptive Technologies for Manned Interstellar Travel”
10:10am Presentation 2: Aaron Cardon, “Ideal Biological Characteristics for Long-Duration Manned Space Travel”
10:35am Break
10:40am Presentation 3: Rob Swinney, “Project Icarus”
11:25am Presentation 4: Jim Benford, “Shouting to the Galaxy: The METI Debate”
11:50am Break
12:00am Session Chair Panel, “Discussion of Tracks”
12:45pm Icarus Project Lead Panel, “Progress Report and Future Objectives”
1:30pm Mike Mongo, “Build a Starship”
1:45pm Richard Obousy, “Building an Interstellar Community”
2:00pm Icarus Starship Congress Ends

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Grand Strategy Annex

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