≡ Menu

SETI, METI, and Existential Risk

To broadcast or not to broadcast? The debate over sending intentional signals to other stars continues to simmer even as various messages are sent, with no international policy in place to govern them. Writer Nick Nielsen looks at METI afresh today, placing it in the context of existential risk and pondering the implications of what David Brin has dubbed the ‘Great Silence.’ If risk aversion is our primary goal, do we open ourselves to a future of permanent stagnation? Or is announcing ourselves to the universe something we have any real control over, given the ability of an advanced civilization to detect our presence whether we send messages or not? Mr. Nielsen, a contributing analyst with online strategic consulting firm Wikistrat, wonders whether our counterparts around other stars aren’t wrestling with the same issues.

by J. N. Nielsen


At the Icarus Interstellar Starship Congress in Dallas last August I had the good fortune to be present for James Benford’s talk about METI, “Shouting to the Galaxy: The METI Debate.” METI is an acronym for messaging extraterrestrial intelligence, which is to say the active propagation of EM (electro-magnetic) spectrum communications from Earth to extraterrestrial targets, in contradistinction to SETI, which is the search for extraterrestrial intelligence, which does not seek to send messages from Earth but instead only listens for EM spectrum signals from the stars.

METI may be contrasted to SETI as active sonar to passive listening: active sonar pings the depths of the ocean and waits for the sound to be bounced back by objects below; passive listening sends out no pings, but simply waits for whatever sounds happen to come one’s way. The analogy is useful because it points to one of the controversies in the METI/SETI debate: submarines, which are typically the targets of active sonar, generally prefer not to be found, so they wait quietly in the depths and rely mostly on passive listening. It is those who hunt the submarines that employ active sonar.

Are technological civilizations floating in the cosmos like submarines floating in the sea? Is the lesson of what Paul Davies calls the “eerie silence” and David Brin has called the “Great Silence” that there is a reason to maintain a low profile and to listen only? Is the universe such a dangerous place that it behooves us to maintain radio silence? This was discussed in Benford’s presentation. Benford outlined the arguments made by both those for and against METI. Primarily these arguments came down to the advocates of unregulated METI maintaining that interstellar travel is impossible (therefore making METI safe), while opponents of METI maintain that the “leakage” of the ordinary (unintentional) EM radiation of a technological civilization cannot be detected at interstellar distances, though intentional METI signals could well be heard (meaning we are safe for the time being, but METI would raise our risk profile).

This debate leaves aside the possibility that one might disagree with both premises, as I do, and maintain that, given a certain technological threshold, interstellar travel is possible, and that, also given a certain technological threshold, it is likely that unintended EM spectrum radiation leakage is detectable. These two technological thresholds—those of interstellar flight and detection of the EM leakage of technological civilizations—are not likely to be one and the same, so that a gap is opened up between the possibility of detecting ETI at interstellar distances and actually attempting an interstellar journey to meet ETI face to face. This gap could be one explanation of the Fermi paradox, but I will not explore this possibility further at the present time.


Although we do not now possess the science or technology to detect EM signatures of ETI at interstellar distances, we must account for the possibility not in terms of our present technology but rather in terms of technology that would be available to a technological civilization somewhat in advance of our own. Any peer civilization (i.e., any technological civilization like us) is going to be looking for peer civilizations because an intrinsic curiosity, at least in part, defines our civilization, and is likely to be similarly present in any civilization capable of science and therefore capable of developing an industrial technology. 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.

Why would an ETI be looking in our direction in the vastness of the cosmos? In so far as Earth occupies the very interesting position in the cosmos of being a small, rocky planet in the habitable zone of a main sequence star, geologically active, with a large moon, and with a large Jovian planet in the outer solar system to clear away the orbit of the inner solar system of potentially damaging debris, the earth does in fact occupy a privileged position in the universe—though, interestingly, not privileged in virtue of the structure of the universe (such as occupying the center of the universe), but rather in virtue of a contingent confluence of circumstances conducive to life.

We are now, at the present level of our technology, probably 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 worked on the spectroscopy of exoplanet atmospheres, and in so doing they would have performed this spectroscopic analysis for the kinds of planets that would likely 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.

Benford has elsewhere detailed the considerable expenses that would be entailed by any large SETI or METI effort with a realistic ability to communicate over interstellar distances. (Benford has written a series of papers on the cost of interstellar messaging beacons, which are referenced below.) I am not convinced by arguments that the cost of interstellar beacons would be too high to be practicable. Estimating the costs of mega-engineering projects incorporates a range of assumptions intrinsic to economies of scarcity; once any technology-capable species transcends its homeworld and becomes a spacefaring civilization (i.e., once it has extraterrestrialized its civilization) energy and material limitations will cease to be relevant for all practical purposes.

With all the materials of a solar system, the continuous energy output of a star, and robots to do the building, a radio telescope capable of detecting unintentional EM spectrum leakage from a technological civilization light years distant might be no burden at all. Such a project is not far beyond our present technological capacity. For this reason I believe 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 would have already identified Earth 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 of the Starship Congress, Heath Rezabek, suggested that anyone opposed to unregulated METI could broadcast a counter-signal to a METI signal and essentially silence that signal. Subsequent to the Congress, this idea came to be called the “Rezabek maneuver,” and was further elaborated by Heath Rezabek, Pat Galea, and James Benford, who suggested several strategies for the masking of a METI transmission. Harold “Sonny” White, known for his research into the physics of superluminary interstellar travel suggested, “Sounds like we need to add another factor to the Drake equation: Rezabek Ratio — defined as the ratio of civilizations that mask their presence using the Rezabek maneuver to the open civilizations that leave the light on…”

The possibility of a METI counter-signal is an idea that can be scaled up beyond the scope of a single planet, so that it is possible that 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.

This conclusion is quite similar in some respects to the conclusion in the last paragraph of David Brin’s classic paper (“The ‘Great Silence’: the Controversy Concerning Extraterrestrial Intelligent Life,” Quarterly Journal of the Royal Astronomical Society, Vol. 24, NO.3, P.283-309, 1983):

“It might turn out that the Great Silence is like that of a child’s nursery, wherein adults speak softly, lest they disturb the infant’s extravagant and colourful time of dreaming.”

There is a relationship between the idea of the universe as a jungle and the universe as an imposed quiet zone: that safety is preferable to risk. In other words, these two approaches to the Great Silence imply risk aversion. I don’t think that we can safely assume risk aversion, especially in light of the fact that in SETI and METI we are contemplating peer civilizations, and just as these peer civilizations would likely incorporate our curiosity about the universe, they would also likely incorporate our willingness to take risks.

Who is likely to hear any signals broadcast in a METI effort? Non-peer civilizations without any equivalent of our science, technology, curiosity, and risk-taking habits could likely only be detected by an actual mission to the homeworld of such a civilization. They won’t be listening for us. Who might be listening for METI signals? Predatory peer civilizations may be listening, or may even broadcast an interstellar beacon, just as surface warships send out sonar pings into the ocean, listening for a response. If a successful SETI effort leads to a METI effort on our behalf, that may all be part of a plan – and not our plan.

We would do well to be cautious, but it would be folly to suppose that risk can be eliminated. To exist is to be subject to existential risk. There is no risk-free norm to which we can return by following some program of risk aversion or to which we will naturally be returned by abstaining from particular actions. But this should not be taken as cause for despair: METI is a classic risk/opportunity tradeoff (cf. Existential Risk and Existential Opportunity). Risk and opportunity cannot be separated.

If we contact ETI it could be the greatest thing to ever happen to our civilization, or it could be the worst thing. When we think about existential risk (if indeed we do think about existential risk at all), it is usually only as an existential threat that must be mitigated, whereas existential risk may be understood both in terms of its possibilities as well as its limitations. One dimension of the risk/opportunity tradeoff is that the same action (or inaction) that we take to mitigate existential risk may unintentionally magnify risk, just as one and the same action (or inaction) we pursue in order to seize an opportunity may come to unexpectedly foreclose on that opportunity. (Either scenario might describe a METI initiative.) No outcome is inevitable; that is why we call it risk. If the outcome were inevitable, it would lie outside the scope of risk. (Cf. Existential Risk and Existential Uncertainty)

If our civilization determines that METI is too great an existential risk to bear, then existential risk perception begets risk aversion and possibly culminates in permanent stagnation—which means that we must not only think about existential risks to Earth-originating life, intelligence, and civilization, but also existential risks to all life, intelligence and civilization, anywhere, since other sources of life in the universe may come to the same conclusion and an entire galaxy (or more) might be plunged into permanent stagnation, flawed realization, or subsequent ruination as a consequence of this perceived existential risk.

Many of those who contemplate intelligent life in the universe suggest the possibility of civilizations a million or more years old. I myself don’t think this is likely, but in this event an early, pre-emptive silencing of the universe by an advanced civilization (an imposed Great Silence) might well prevent later civilizations from broadcasting their presence to the rest of the universe—existential threat and existential risk thus gives way to existential isolation and existential despair on a cosmic order of magnitude. In this scenario, the Great Silence is a fitting tribute to a mournful universe in which timid civilizations choose silence, or have silence imposed upon them.

This strikes me as an unlikely scenario. If we are true to our history, and we rush in like fools where angels fear to tread, we will announce our presence to the universe both intentionally and unintentionally. Our peer civilizations in the universe (if there are any) are likely to do the same.


James Benford’s papers on interstellar beacons:

1 “Messaging With Cost Optimized Interstellar Beacons”, James Benford, Dominic Benford and Gregory Benford, Astrobiology, 10, pg. 475, (2010).

2 “Searching for Cost Optimized Interstellar Beacons”, Gregory Benford, James Benford and Dominic Benford, Astrobiology, 10, pg. 491, (2010).

3 “Building And Searching For Cost-Optimized Interstellar Beacons”, James Benford, Dominic Benford and Gregory Benford, in Communication with Extraterrestrial Intelligence, Ch. 18, ed. Douglas A. Vakoch, SUNY Univ. Press, NY, pg. 279-306, (2011).

4 “Smart SETI”, Gregory and James Benford, Analog, vol. CXXXI, no.4, April (2011)


Comments on this entry are closed.

  • Rob Flores November 8, 2013, 12:28

    A trully Xenophobic alien race with just 2 million years head start could
    have sterilized all threats by now. And it might monitor planets that have
    multicelled animals in them and pre-emptively strike those that may give
    rise to sentient beings. It would have experience in the most efficient ways
    to do this without damaging potential colony sites. (That’s why I dont think this type of threat is very likely, because we simply EXIST)
    The other posibility is that of the Elder races shielding the rising sentients
    from developed sentience that wish to undertake hegemonizing swarms as
    Ian Banks would say. ( no way to comfirm this)
    No, the real threat is remote posibility of a near simultaneous rise of an alien species within say 1,000 LY. In that case METI is dangerous as
    even not so advanced aliens would find us easilty. So I would say that
    given what is at stake it might be a good idea to just listen and observe.

    Taking a page from another website, they speculated that Maybe
    being a sentient civ in the galaxy is like being lost in Central Park
    at Night. You don’t dare attract attention, you don’t know the motivations of those you see but dont see you. You wait for a cop or till morning.
    Except: there are no cops and the night never ends.

  • d.m.falk November 8, 2013, 13:12

    We currently have this thought that because of our level of technology, “if we can’t see them, they can’t see us”, but as noted, we’re on the verge of being able to see those worlds, and even how much, and what kinds of life and pollution, just from spectroscopic signatures. But as Stephen Hawking tried to say, “we shouldn’t send anything, saying, ‘hey, we’re here!’, and alert any hostile, empire-building (or worse) civilisations to our presense”, well… Guess what? They’d already know by now, long before we even reached this level of technology/society, and have been invaded by now- Even a primitive culture leaves an artificial mark on its environment, which can be seen spectroscopically!

    So why not? We stick out as much as the proverbial sore thumb– We’re just now beginning to test the feasibility of interstellar travel, and we have yet to master quantum communications (this will be crucial, and something most haven’t even ever heard about, much less thought about!), but we are an emerging society.

    I personally think we have very little to lose, and much to gain! I can see that by 2100, we will not only know of other life-bearing worlds, but should by then have not only our first contact, but an ongoing dialogue that will bring us into the interstellar neighbourhood.

    The worst, however- and I’m not sure we can completely quell the matter- is ourselves, or rather, those who fear the unknown, and bring their own hatred and bigotry (the “ugly American” syndrome), not to mention religious zealotry into the mix.

    Seriously, we would’ve been invaded long ago, just because we have a strong biological signature that can be detected by a civikisation even with our relatively primitive level of science and technology.

    I say “go for the gold!” :)


  • d.m.falk November 8, 2013, 13:26

    @ Rob Flores: we aren’t that advanced of a civilisation, but we’re no more than 20 years out (I say less than ten) from the kind of spectroscopic detection that could detect us from a comparative distance- This is about as simultaneous as it gets, which means someone out there already has noticed our world, detected organic life, discerned the difference between natural and artificial pollution- We stick out as a living world, rather strongly! We really don’t have all that much to lose, to be honest, except our homo- and geocentrist view of our universe. Believe me, we’re already able to detect and discern chemical signatures, just not yet down to terrestrial-sized exoplanets, and that’s going to be very soon- Perhaps by 2015 or 2016 at the earliest, when a new high-resolution spectrometer will be installed at ESO’s Chilean observatories.

    The question is, are we able to overcome our own fear?


  • Steve Kilston November 8, 2013, 13:54

    This is indeed a ridiculous thing to worry about. Since an ability to detect distant civilizations spectroscopically and otherwise will always be achieved long (at least hundreds of years) before any capability for interstellar voyages, there is absolutely no added danger to any civilization from attempting active communication. You can fear, but you can’t hide.

  • Wojciech J November 8, 2013, 15:42

    “To broadcast or not to broadcast? The debate over sending intentional signals to other stars continues to simmer even as various messages are sent, with no international policy in place to govern them”

    Earth has been broadcasting signals since billions of years when first life emerged.
    To any civilization capable of traveling between the stars it would be easy to observe planets from afar for signs of life in atmosphere.
    With even more advanced telescopes they would be also to take images of our planet with resolution allowing to distinguish vegetation cover on continents, and finally things like night lights, large farm fields,ship lights etc.

    So it’s pointless to debate if we should broadcast. Earth has been doing it since billions of years, our civilization since thousands where first cities were created with illumination during the night.
    If there would be any nearby civilizations(say less then 1000 light years) they would know of existence of life and civilization on our planet already.

  • David Cummings November 8, 2013, 15:56

    ” Estimating the costs of mega-engineering projects incorporates a range of assumptions intrinsic to economies of scarcity; once any technology-capable species transcends its homeworld and becomes a spacefaring civilization (i.e., once it has extraterrestrialized its civilization) energy and material limitations will cease to be relevant for all practical purposes.”

    I agree with this statement and believe that it doesn’t go far enough. It’s not just the costs of mega-engineering projects that will become irrelevant to a spacefaring civilization, but the whole concept of “conquest for material gain” which have driven all conquests in our own relatively short history.

    What are the energy requirements of traveling at a decent rate of speed (10% the speed of light)? Multiply those requirements times a thousand vessels, or ten thousand, and compare them to the “gain” of “capturing” earth?

    Surely it’s more energy-efficient to terraform a planet in your own (or a nearby) system than it is to launch a conquest armada. The concept of conquest comes from economies of scarcity — which are the only economies we have to-date known. Space-faring civilizations are not going to be launching interstellar explorations with a goal of taking over real estate. Such an idea is based on our own primitive past.

    Rather, they will be looking for the same thing we will be looking for once we really do make the jump to spacefaring… they will be looking for contact for the sake of contact. They will be looking to swap stories, just as we will be.

    Fear of the unknown is screaming at us from the back of our monkey-lizard brains, not from any true appreciation of the distances between the stars and the change that any race will have to go through to travel those distance.

  • Erik Landahl November 8, 2013, 17:37

    The future of sufficiently advanced technological civilizations may be that Artificial Intelligence becomes the only sentient life form. If so, would AI possess the inherent curiosity that characterizes humans?

    Curiosity has been an evolutionary advantage for all higher Earth animals that possess it, notably humans, because it is a strong driver that pushes a biological organism to discover new knowledge. Why would curiosity be an evolutionary advantage for AI?

    AI’s motivations for spreading through the galaxy may be based on its desire for fast-paced and sustained technological advancement. What is the ultimate goal or goals AI wishes to achieve through its extreme technological advancement? Existence in different dimensions? Travel to other universes? And for what purpose? AI’s motive for technological advancement might be resigned to human imagination, since AI’s mind would be fundamentally different from ours.

    If self-improvement through sustained technological advancement is AI’s driving desire, it would look for the most straightforward sources from which to obtain the resources it needs. Earth would not likely be that place. As biologicals, we think of Earth as a cornucopia of amazing resources – but our resources are a mixture of the wide variety we need and use as biologicals.

    AI would probably not need the mix of resources that we need. Would it make sense to AI to subdue Earth, a world containing 7 billion intelligent beings, in order to obtain quite limited amounts of the resources it needs? It could obtain the resources it needs – minerals and energy – efficiently and in abundance elsewhere.

    Therefore, if Earth isn’t an efficient source of the resources AI needs, only curiosity remains as AI’s driver. And if AI isn’t curious, it would not likely waste its time contacting Earth.

  • Andrew Palfreyman November 8, 2013, 18:25

    We have little choice in our analogies concerning the interpretation and explication of the unfamiliar but to grasp hold of that with which we are familiar. Science fiction writers struggle to imaginatively break these conceptual bonds while embedded in the same cultural constraints as the rest of us, with varying success. Our templates tend to be drawn from terrestrial biology and politics. We bring these to bear when forming attitudes about the Xenome, as perhaps the collective phenomenon of extraterrestrial life should be called, but with a sample size of zero, there is little else we can do. Some such analogues come to mind:

    – Xenophobia
    Centuries ago, had China not abruptly curtailed its nascent urge for global exploration, armed as it was with a mature set of technologies at least as efficacious as anybody else’s at the time, the global political map would almost certainly look very different today. They chose to turn inwards, and it cost them a development gap which yielded the world stage to others. Most here, I suspect, would not favour that Chinese model of yore, but out there others may have taken the xenophobic route, with its attendant consequences for us.

    – Nature red in tooth and claw
    Is it excessively parochial to expect that life everywhere evolved in a competitive environment? It is hard to imagine any alternatives. Life, by its very nature, strives to live. The consequence for interpreting the xenome depends on whether it is possible to successfully evolve past the stage of predator/prey primitivism, and the extent to which this transcendence has occurred out there. I suspect that the results are “mixed”, just as they are with humanity today.

    – Club membership
    Given the timescales involved in the evolution of the xenome – billions of years – it is highly unlikely that a level of technological sophistication similar to our own today exists out there. The very closest others will most likely be millions of years behind or millions of years ahead of us. It is of course the latter category which interests us the most. Are they a set of caretaker races? of predatory races? of smugly xenophobic races? Is there a club which imposes its will upon the galaxy (and perhaps beyond), and what are the conditions for entry? How can a club even exist when the developmental disparities across the xenome are likely to be enormous? Are we indeed a colony, seeded long ago? If that is what we are, then we represent the pet fish swimming in the bowl of the club room.

  • Mike November 8, 2013, 18:28

    When we really have no data but can only only speculate about other possible civilizations and their cultures, motives, rules, beliefs, do we behave exuberantly or cautiously? I don’t know. Neither do you.
    When we don’t know anything is it not better to err on the side of caution?

  • David Cummings November 8, 2013, 19:22

    “Err on the side of caution” might be good watchwords except for one thing: who is going to stop METI from happening? It’s been happening since the radio speeches of FDR. It will happen quite purposely whether “sanctioned” or not.

    Why worry about something you can’t control. If they are out there, they will hear us.

  • DCM November 8, 2013, 20:05

    It seems unlikely to me that we’ve been visited yet, though we could’ve been detected.
    What we really should concentrate on now is listening and watching while we colonize our own system and turn dead worlds into living ones. This will make us less vulnerable to accidents such as asteroid collisions and enable us to study any distant worlds we do discover to have life.
    It might help to cut back on signals beamed into space by using cable and similar systems since we don’t know what’s watching and listening.

  • Adam November 8, 2013, 21:18

    Let’s not be too blase about listening for signals either…

    Enrico Fermi and the Dead Cat
    by John Barnes
    From pole to pole, about five centimeters deep, the green scum covered the fourth planet from the red star. It floated on the oceans, raining down forever into their depths. It lay across the continents in thin green sheets, leaving only the highest mountaintops bare. It washed down rivers; at their mouths it clung to piers unused for a hundred thousand years. It blew on the wind against piles of rubble that were no longer buildings, stuck to the naked rock on plains that had once been deep in topsoil.
    And the green film was all there was.
    Each year there was less of it, for no circulating ecology fed it. It bled away to the ocean floor, or on the wind to the glaciers and mountaintops, each time losing forever some of the carbon and nitrogen fixed by the planet’s former ecology.
    Faintly at first, radio signals fell on the planet. Ancient genes woke from disuse and responded.
    The green film coalesced and organized. Cells specialized; the film transformed itself into a single planetwide organism.
    Mighty stalks of cellulose fiber, kilometers high, grew up in less than a decade. Long filaments ran over beaches and rocky coasts down into the sea, and membranes at their ends filtered in silver, gold, aluminum and copper, which travelled a molecule at a time up the filaments to coat the outsides of the stalks. At the top of the stalks, leaves, grew. Other organs grew deep into the ground, taking energy captured by the leaves and binding it into separated metals and great chambers filled with acid.
    It took thirty years to finish growing. By then the signals were strong and clear, with one great dip in strength for ten twenty-fourths of each long cycle that might have suggested – had there been a mind to suggest it to – a world with its radio stations concentrated on two thirds of its lines of latitude.
    The final phase of the genetic program activated. Great currents pulsed along the stalks in the shape of incoming signals, interrupted in a pattern read from the genes themselves.
    After barely two years of this, the energy reserve exhausted, most of the few remaining bioavailable trace elements of the planet squandered, the great organism reverted within hours to green scum. It devoured its own towers and filaments and batteries, subsiding first into thin remnants of the green film, then, over millennia, into mere spores.
    The spores waited while ammonia and methane replaced free oxygen in the atmosphere, while rain and wind scoured the continents bare. Occasionally something flickered toward life, perhaps once in fifty thousand years; always it met a spore, and shortly became a spore itself. Eventually the sun went out.

    Suddenly, among the normal static and background noise, there was bits of pieces of fifty-year-old television programs. Occasionally blips flickered in and out on older radars.
    Then the EuroEar on the back side of the moon started getting it, and before anyone really had time to ask any questions, dozens of ground-based radio telescopes, even home-made ones, were picking it up.
    So there was no hope of keeping the transmissions secret. Within a week all newspapers were printing copies of the message, showing that the stops always fell in pairs and the pattern of stops repeated identically every few hours, regardless of what old broadcast it had been superimposed on. Some used bars, some used Morse Code notation, but all offered prizes for the best “decoding.”
    Within two weeks the prizes were all claimed. Any number of biologists had noted that the four possible pair values – short-short, short-long, long-short, and long-long – could be assigned to the four nucleotides on a strand of DNA. And when the translation was set to
    the DNA resembled that of several terrestrial viruses.
    There were a few nut letters in the papers, of course, and one religious publisher brought out a confusing, badly written and badly printed book, Satan’s Spawn from Space, but most people just watched to see whose laboratory would actually produce the organism first. Every dime the respective governments could scrape together poured into the labs, and there were fresh scandals in grant diversion every week.
    Ohio State, something of a dark horse, won, producing a virus from the DNA.
    Triumph was sweet for several months, until it became clear that the stuff didn’t do anything. It seemed to be so alien that no living thing on Earth made antibodies to it. It replicated freely inside living cells, but after making a few copies of itself it did nothing there, diffusing lazily through organisms without affecting them at all. Its only other notable feature was that all of the descendents of OSU’s first virus replicated simultaneously, at intervals of 4052.88 seconds, as if they all carried copies of the same clock.
    The message from space died out after two years, fading to nothing across a few days. Within a few years the virus was no more than a curiosity. Inevitably, as its harmlessness became apparent, precautions became lax, and it escaped into the environment.
    Papers were published arguing there had been no message – that some sort of accident or fluke accounted for stuttering fifty-year echoes. Others claimed that the message had been written in a four-letter alphabet, and the resemblance to a DNA sequence had been purely accidental. Three scholarly journals devoted themselves to the interpretation and discussion of the signals, and on most college campuses there were one or two exosignalists.
    The mystery virus itself found minor niches in science. Because it was ubiquitous, safe, and rather large, high-school students did science-fair projects with it. A Japanese company patented a process for converting to edible protein. Ecologists studies its spread, finding it in insects in the Antarctic dry valleys, among the first lichens on a new volcanic island in the South Pacific, and in fungus in a cave deep within K2.
    Most people forgot about it most of the time.
    Probably, in the two hours of agony as the world ended one day, no one was even thinking about the virus. Every living thing with a voice was screaming, everything that could tear tore at itself, ripping out sickly green hunks from its own flesh.
    Within a few years, the green scum spread over the surface of the Earth, in an even layer about five centimeters deep.
    It waited for a radio signal, one with a recognizable pattern. Had it been capable of speech, and disappointment, it would have said that it had never been disappointed anywhere in the galaxy.

  • Alex Tolley November 8, 2013, 21:31

    I tend to agree with others that we are already at the cusp of developing tools to detect both life and alien civilizations by means that do not depend on them shouting into the dark with radio waves. A mere eye-blink in cosmic time and this capability will be quite mature. If there are others out there, they either have this capability already, or they are not, in which case we will be the first to explore.
    It isn’t so much that we should be quiet in the jungle, but rather we are in a dark room and worrying about imagined terrors, no real ones.

    However, since we are so close to being able to detect alien civilizations, it might be prudent to hold off on METI for a few years until we have more data on whether other worlds are living and even have intelligent life (or machines).

    Although I doubt it, it is just possible that fake civilizations have been created to draw us out, rather like a duck hunter in a blind using lures. If so, surely that “galactic encyclopedia” should be being received by us by now.

  • Rob Flores November 9, 2013, 0:48

    Allex T.
    Funny you should mention this. As I am not the only one that thinks
    that if we are going to create a beacon to announce our presence it
    would be better to put it a couple of dozen parsecs from Sol, making
    sure it can’t be traced to us.

    I hope the duck blind is a metaphor and aliens are not looking for something delicious. Monkey meat is delicous to you know who.

  • Nick Nielsen November 9, 2013, 1:35

    @Rob Flores

    I agree that the greatest existential threat would come from a peer or near-peer civilization located within our cosmic “neighborhood ” of about 1,000 light years’ radius from our sun. Given the fact that we can narrow down the threat in this way (i.e., spatially), we can also narrow down the threat temporally. We have to ask what the likelihood is that the peer civilization would appear in our neighborhood at approximately the time we are coming to technological maturity.

    I previously wrote about this in “The Law of Trichotomy for Exocivilizations” (http://geopolicraticus.wordpress.com/2012/09/12/the-law-of-trichotomy-for-exocivilizations/) specifying trichotomy since, for any given exocivilization, it must appear prior to us, roughly simultaneously to us, or after us.

    Estimating the number of potentially threatening civilizations simply takes the Drake equation one term further (or several terms further), with an additional variable (or variables) to cover the likelihood of that civilization being expansionist, aggressive, and militant, its ability to hear our signals, and its ability to engage in interstellar flight in order to reach us and do us harm.

    Best wishes,


  • Nick Nielsen November 9, 2013, 2:32


    RE: “The question is, are we able to overcome our own fear?”

    Fear is subject to individual variability; it is one (among many forms) of the intellectual expression of individual variability that drives natural selection. If there is ever a selection event that bears not upon our physical structure but upon our intellectual attributes, then fear may come to play a significant role in such a selection event. A successul METI or SETI effort could be the trigger for just such a selection event.

  • Antonio November 9, 2013, 4:09

    It’s not true that people don’t shout in the jungle. That’s only our occidental point of view. Most of the people in the jungle (namely, aborigens that live there) communicate with other people, even unknown people. If they didn’t that, tribes would dissapear in a few centuries due to genetic diseases caused by endogamy.

  • Anthony Mugan November 9, 2013, 6:56

    I tend to agree with much of the above discussion. The fears associated with METI seem based on an exceptionally unlikely scenario of:
    a) a civilisation that can detect our signal exists
    b) it is on the cusp on developing interstellar travel but has not yet reached our solar system
    c) they have not yet detected us in any other way
    d) are motivated and are allowed to cause us a problem

    This set of criteria seems to require both the emergence of advanced ETCs to be very rare, or for them to be short lived AND for the other. I civilisation to be close enough to detect our signal. Otherwise both us and they will be emerging into a galactic civilisation that is saving us largely alone, for whatever reason. This seems statistically very unlikely
    The scenario further supposes we are close together developmentally, also unlikely given the extent of deep time avIlable.
    The scenario also assumes that by the time they pick up our signal and react to it we won’t be capable of handling the situation. If they haven’t got here yet then we are probably not talking about FTL propulsion.

    Overall I don’t see METI as presenting any real risk. For precisely the same reasons I suspect it is also a waste of time. If they don’t exist or are here already then the silence will continue (in the latter cases for the forseable future), if the exist but can’t get here, either because interstellar travel proves impractical or they tend to collapse as cultures there is equally very minimal risk.

    There may be limits to technological progress, in energy production, information storage and in the physical constants of nature. We are a long way off them but moving fast. In a millennia or two, if we survive, we may be a close to these limits and emerge as infants into a galactic civilisation, or find we are incredibly lucky and become the galactic culture. In the latter scenario my advice to other cultures would be different… Be very careful indeed, but that would represent a cosmologically short time period of human expansion.

  • Wojciech J November 9, 2013, 9:40

    ” 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.”
    If they would want to detect technological civilization this would be unnecessary for reasons mentioned above, in fact Centauri Dreams already covered this :
    “The Light of Alien Cities

    by Paul Gilster on November 7, 2011
    The researchers aren’t expecting to find cities on KBOs, but they do point out that the next generation of telescopes, both space- and ground-based, is going to be able to reach much further into the universe for signs of artificial lighting. An exoplanet can be examined for changes to the observed flux during the course of its orbit. When it’s in a dark phase, we should see more artificial light on the night side than what is reflected from the day side. A signature like this would have to be bright — the night side would need to have an artificial brightness comparable to natural illumination on the day side — but an advanced civilization might have such cities”

    Of course there are other ways to detect civilization(chemical traces in the atmosphere for example), but the point is, that radio transmissions are inefficient way of detecting other civilizations.

    ” I am not convinced by arguments that the cost of interstellar beacons would be too high to be practicable”
    There is no need for interstellar beacon-we already live on one. Earth and it’s biosphere.

  • Gregory Benford November 9, 2013, 11:26

    ” once any technology-capable species transcends its homeworld and becomes a spacefaring civilization (i.e., once it has extraterrestrialized its civilization) energy and material limitations will cease to be relevant for all practical purposes.”

    But labor is the true deep cost of all METI, and that doesn’t yield to increases in energy and material resources. Marx’s labor theory of value leads to many false conclusions, but is basically correct: you have to pay workers to extract resources, and build METI broadcasters. So the cost arguments Jim & Dominic & I advanced are still valid, as we remarked in those papers.

    Still, good to see such debates going on. It’s further evidence of the blossoming interstellar culture in our society.

  • Andrew Palfreyman November 9, 2013, 14:13

    I wrote “Given the timescales involved in the evolution of the xenome – billions of years – it is highly unlikely that a level of technological sophistication similar to our own today exists out there. The very closest others will most likely be millions of years behind or millions of years ahead of us.” And yet many here write as if they expect METI to contact “peers”. This is misplaced anthropocentrism. There is a vanishingly small chance that peers exist. It is almost a mathematical certainty.

  • Alex Tolley November 9, 2013, 14:29

    that anyone opposed to unregulated METI could broadcast a counter-signal to a METI signal and essentially silence that signal. Subsequent to the Congress, this idea came to be called the “Rezabek maneuver,” and was further elaborated by Heath Rezabek, Pat Galea, and James Benford, who suggested several strategies for the masking of a METI transmission.

    I defer to experts, but I think that it would be extremely hard to mask signals. First there is the problem of detection, which would mean that the initial signal would be unmasked, even if the rest was. Benford’s own idea of pulsed signals would be hard to mask. Secondly, the signaler can change the direction, frequency and intensity of the signal, making masking very hard. This creates a cat and mouse game that would be hard to track and mistakes might make the anti-signal, a signal. White noise could be foiled by signal repetition. Finally multiple simultaneous attempts could overwhelm the resources of those trying to mask the signal. One can see that frustration by the anti-METI people might lead to making transmissions illegal which could escalate from simple policing to warfare on “rogue regimes”. If signaling could take place off-planet, that would compound the difficulty of masking.

  • DCM November 9, 2013, 15:43

    It isn’t necessary that aliens by motivated to cause us problems. They might do so unintentionally and even in total incomprehension of it. Though their motives weren’t particularly benevolent Europeans’ biggest impact in America was smallpox and measles. They themselves didn’t understand the diseases’ cause and transmission and didn’t expect millions to die from them in short order — not that they were especially unhappy about that.
    This doesn’t mean alien civilizations would bring diseases or that we’d even be vulnerable to their diseases but there could be analogous factors that at this point we can’t imagine.

  • Ron S November 9, 2013, 15:44

    For the sake of discussion let’s assume the correctness of the argument that the existential risk of METI is low, as many commenters here believe.

    Now let’s see if the same people would be willing to quantify that assumption. That is, at what probability (if we could ascertain or estimate it with a suitably low variance) should METI be considered too risky an undertaking?

    For comparison we can compare that (selected) probability to the existential risk of an NEO impact, where the equivalent action to METI is to forgo any effort to detect and mitigate potential large NEO impactors. The result is the same: the end of humanity, or perhaps merely long-lasting global suffering.


  • Mike Jude November 9, 2013, 16:34

    Why does Nick feel that very old civilizations are unlikely? Is there something he published that would explain why a million year old civilization probably doesn’t exist?

  • Ron S November 9, 2013, 17:56

    Alex: “I defer to experts, but I think that it would be extremely hard to mask signals.”

    Ah, the good old days! I clearly recall the efforts of Soviet-bloc countries to locate and jam the shortwave broadcasts from VOA, BBC and others. Sometimes they succeeded but they often failed. It was a game of cat and mouse between broadcasters, jammers and listeners.

  • wajai November 9, 2013, 18:06

    Earth has been tagged as a living world for a very long time by its atmosphere free oxygen and that means that even if civilizations are very few and very far apart some are aware of Earth being a living world and had ample time to be hostile.
    We are here so we can conclude that being a living world is not a cause of obliteration.
    But for how long has our world been tagged as a technological world?
    Certainly for a much shorter time,meaning that the information ,traveling at the speed of light hasn t reached very far from here.
    If civilizations are few and far apart noone knows about us being technological yet , so we can t conclude anything just because we are here.
    The time span in the relationship with another civilization could be in the thousands of years if the spacing is in thousands of LY
    1 because it could take a ‘long’ time for us to be detected as technological .
    2 because it would take at least the same time for any consequence hostile or not to reach us.

  • Christopher Doll November 9, 2013, 18:58

    Is there an extension to the Drake equation, or a follow-on, that attempts to calculate a range of possible ETI cultures based on current exoplanet discovery models?

    I’m sure it would make a fascinating thought exercise, or maybe one that is impossible to frame in such a fashion.

  • Wojciech J November 9, 2013, 19:14

    “But for how long has our world been tagged as a technological world?”
    Depends on how good resolution of hyper-telescopes would be. In theory things like farm fields should be visible.
    As to detecting city lights during the night-it’s difficult for me to find now if Sumerians and Greeks illuminated their cities enough to be visible. But Rome certainly would be detectable just as modern cities are.

  • David Cummings November 9, 2013, 19:46

    wajai, good point about the round trip time between signal and response.

    Assuming that the nearest 500 light years are already spoken for (in terms of radiation leak having about that range of detectability), then any “surprise” METI signal (a signal that would announce us when we wouldn’t otherwise be detected) will be to a civilization greater than 500 light years away.

    So it’s going to take 500 years for us to make the announcement, at least. And it’s going to take them 500 years to respond, at least. That’s a thousand years. We’re either going to be dead by our own hand or very very advanced ourselves a thousand years from now.

  • Alex Tolley November 9, 2013, 20:35

    If civilizations are few and far apart noone knows about us being technological yet , so we can t conclude anything just because we are here.

    That assumes that the only method other civs use is based at very remote locations, e.g. their homeworld. As we’ve argued before, civilizations can easily fill the galaxy with replicating probes within a million years. All they need is a probe in the solar system to monitor us very closely. More parsimoniously, a probe could be located within 100 – 1000 ly away and monitor many solar systems. They could well know about us now.

    if humans expand out into the galaxy, that will likely happen within the next millennium, probably a lot sooner. For a predatory species, monitoring from a long distance will be useless, because by the time they get the information, it may be too late to contain the upcoming species.

  • Markham November 10, 2013, 3:13

    Its really only been roughly the last 100 years that we’ve been considering possibilities of alien life, and substantially less where we could ourselves hunt for it. Another hundred years could see advances in nanotech, AI and robotics that make the current cost estimates for interstellar beacons, probes and imaging wildly over-inflated. So I’ve never been sold on cost being a preventative factor, instead its more likely to be from an inward focus into virtual worlds… with computer power growth likely to far exceed the pace of exotic physics advancement, by the time we could travel interstellar at a reasonable cost no one will care to… just simulate it instead.

    The window of time for outward focus before the richness of virtual worlds takes over is probably very short, perhaps less than 100 years. Augmented reality nested deep in a fast local planetary communication web would be a far richer environment than isolating yourself in deep space out of reach of the latest conceptualizations… what child raised on high tech will cut themselves out of such a web?

    The ultimate extrapolation of such inward focus might be found here:

    I suspect that the window of time for a technological societies outward focus is very short. If they are also rare in the universe the overlap with us will be non-existent. Tech civs just do not exist in our reachable light-cone… I still don’t see what would stop just one CIV from producing self-reproducing probes to fill the galaxy before turning inward. If there are none in our solar system then it suggests we are the first in our light-cone, tech civs are just that rare.

  • Kamal Ali November 10, 2013, 3:50

    I once did a thought experiment : very optimistically,
    imagine all 400B Milky Way stars have a
    replica of Earth, except that each replica is at a uniformly assigned random
    point in Earth’s 4B year history. Then there would only be 100 other stars
    experiencing our equivalent of the year 2013. Assuming radio noisiness for 100 years, there would only be 10K civs in the galaxy that would be transmitting artificial radio noise. A back of the envelope calculation shows that the nearest radio-noisy one would be on the order of 1K light years away (and it would only stay radio noisy for 100 years!). All the replicas close to us would be far removed from us in terms of development.

    If, as is I believe likely, the lifetime of the civ is much much smaller than the lifetime of the biosphere, then if we could observe all the biospheres, most of them would be far separated in their development than where we are: order of billions of hundreds of millions of years ahead or behind. Then peers would be quite far away and hard to find. Unless civ lifetimes are on the same order as the lifetime of the biosphere, most of them would be extinct or yet to develop. If the nearest civ is developmentally very far in front of us, we would be like the fish in the bowl to them, if we are very far in front of the nearest one, we in turn would observe them the way we observe chimpanzees etc. There would be little to talk about.

    Additionally, to find a peer that is near us in development (say a few thousand years on either side of our development), the nearest one of those might be thousands of light years away. I guess I’m saying that often we forget that SETI needs to find a hit not only in 3D but in 4D and that 4th dimension is quite large too wrt the ratio of the civ lifetime against the biosphere lifetime.

  • James D. Stilwell November 10, 2013, 10:42

    Saw Ender’s Game last night, and unexpectedly watched a story unfold depicting Man as the King of Terror in the entire galaxy, exterminating entire spacefaring creatures he just doesn’t like…

  • Eniac November 10, 2013, 12:35

    Gregory Benford:

    But labor is the true deep cost of all METI, and that doesn’t yield to increases in energy and material resources. Marx’s labor theory of value leads to many false conclusions, but is basically correct: you have to pay workers to extract resources, and build METI broadcasters.

    Between energy, material resources, and labor, labor is likely to be the first to become non-limiting. This process is well under way right under our noses: The explosive rise of automation unleashed by the advent of the microprocessor.

  • Eniac November 10, 2013, 12:55

    Marx was a smart man, but he did not begin to imagine that the means of production would one day be operated without the dispossessed working class whose plight he was so concerned with.

    Have you seen a modern factory? There are already many more machines than laborers. Very soon, the few humans to be found in them will do nothing but walk around and take notes. If they don’t prefer to do that from a bank of video monitors, instead.

  • Chris Winter November 10, 2013, 14:21

    There is a conflict in my own mind about this. I would certainly be among the first to celebrate the finding of an ET civilization. On the other hand, everything we learn about life tells us interspecies competition for food or living space is an essential feature of evolution, and predation is common. Would this apply to intelligent extraterrestrials? I have no way of knowing; as with the question of their very existence, speculation is all we have at present.

    It is now clear that any technological civilization around a nearby star, advanced over ours even by only a century or two of development, could easily recognize Earth as a life-bearing planet and, should they wish to, find artifacts of our technical civilization: artificial lighting, leaked RF signals, or other signs.

    But METI presumably would make our detection much easier, otherwise what would be the point of doing it? And the secondary goal of METI, I presume, would be to receive a “prize package” — a message conveying useful information, such as an inexpensive method of artificial photosynthesis that would let us dispose of our excess carbon dioxide.

    But can we safely assume that any such package would contain only information suitable for our level of development? I think it more likely would be a compendium of alien capabilities, chosen to entice rather than enlighten us. It might teach us how to build starships; whether the hypothetical aliens were hostile or benevolent, they might want us to show up in person so they could better evaluate us. Could we really make good use of FTL travel (assuming it exists) if it were handed to us today? Would advanced medical techniques like life extension really help us on this crowded little world, before we have gotten poverty and disease under better control? There might be truly beneficial things in the package a hypothetical ET message would bring, but I doubt we have the wisdom to use those and set the others aside.

    So I would argue that while the risk may be minimal, so probably is the reward. My choice would be to hold off on METI, meanwhile devoting our resources to activities with more immediate benefit. These include learning more about our own solar system, and especially about asteroids, with the corollary activity of getting humans out there on a regular basis. I would also support SETI even though it may not succeed soon, because it doesn’t increase our detectability, costs very little in GDP terms, and pushes the development of communications and computer technology.

  • DCM November 10, 2013, 20:20

    Particular civilizations in early stages will collapse but beyone a certain point it won’t because intelligent civilized life becomes increasingly efficiant and effective.
    That doesn’t mean they will want to contact anyone else or will have that as a goal. They may well make themselves “invisible”.

  • Brett Bellmore November 10, 2013, 20:21

    ” Marx’s labor theory of value leads to many false conclusions, but is basically correct: you have to pay workers to extract resources, and build METI broadcasters.”

    If you need workers in the first place, anyway. If you have some kind of self-reproducing technology, either MNT or “clanking” replicators, you don’t need to pay anybody.

    I find the notion that we have to hide in order to avoid attack rather absurd. By the time you can cross the interstellar distances in any force, you can live anywhere, scarcity is hardly an issue, and the resources necessary to attack a planet at lightyears’ distance would provide many times the living space at home.

    OTOH, I see no reason to rush into screaming out our presence. Don’t we have better things to do?

  • Peter Chapin November 10, 2013, 20:28

    Gregory: “But labor is the true deep cost of all METI, and that doesn’t yield to increases in energy and material resources. Marx’s labor theory of value leads to many false conclusions, but is basically correct: you have to pay workers to extract resources, and build METI broadcasters.”

    It seems to me labor costs will ultimately become energy and material costs. Once our technology reaches a maturity level where autonomous machines can assemble other complex autonomous machines (and this will probably be possible fairly “soon”), we will be well positioned to engage in mega-engineering projects of our own.

    The first step would be to have construction robots assemble other construction robots making use of the unlimited(?) energy and material resources available in the solar system. Next, allow the resulting exponential growth to continue until a suitable number of robots have been constructed… say 10^15. Then construction can begin on the primary project, whatever it might be. The human labor involved to get the process started might be quite modest… say the resources of a medium sized company.

    Of course this assumes robotics technology well beyond our current skills, but I’m going to guess we’ll be able to do such things in a century or two. That said, the prospect of 10^15 rogue construction robots roaming the solar system is a bit frightening. I sure hope we know how to keep control of them if we ever do build them!

  • Nick Nielsen November 11, 2013, 8:28

    @Mike Jude

    I think that very old civilizations are unlikely because a civilization that stagnated would not be likely to take the steps necessary to address the existential risks that would face any civilization in the long term. What planet is likely to remain habitable in terms of the environment of evolutionary adaptedness for a million years? And if a civilization does take the steps necessary to secure its long term future and becomes a spacefaring civilization, it would likely have found us, or found our planet hundreds of thousands of years ago before we evolved into our present form.

    Of course, there are any number of criticisms of these arguments, and any number of alternative arguments. To do justice to the question of the likelihood of very old civilizations in the universe (something that Sagan and many others are defended) would require an exposition of significant length.

    Best wishes,


  • Nick Nielsen November 11, 2013, 8:44

    @Gregory Benford

    I’m afraid I have to disagree with you about the labor theory of value. No economist has used the labor theory of value as an analytical tool since the formulation of the theory of diminishing marginal utility (also known as the marginalist revolution).

    You could expend all the labor of a lifetime creating something, and if no one wanted to buy it, it would be worth exactly zero. And no matter how much everyone may want something, if no one is selling it, it cannot be had at any price. So we plot the demand curve from low to high and the supply curve from low to high, and where the two cross is approximately the market price, and the market price may bear little relation to the labor that goes into the commodity in question.

    This, of course, is classical economics, which might also be called the economics of scarcity, and if the promises of technologically facilitated maximized abundance come true (and I am not saying that they will) much of this will no longer be true. Interestingly, however, some of the formulations of the marginalist revolution will continue to be true. Even if there is a maximized abundance of tenderloin steak at a first class restaurant, the first one I eat is going to have much more value to me than the second one, and by the third or fourth one the steak is going to start to have a negative value for me (no matter how much I love tenderloin).

    So how does this play out in relation to interstellar beacons? The supply curve will become unlimited for all practical purposes. I assume that much of the work will be automated, which is the common feature of almost all technological abundance arguments. However, the demand curve is subject to the vicissitudes of sentient life. If a civilization stagnates, enters into terminal anomie, or every life form simply is more interested in the alien equivalent of Facebook than in finding out what’s out there, then demand for such things as interstellar beacons crashes, and no matter how cheap or how easy to construct, they won’t get built.

    There is an important and interesting lesson in this: existential risks like permanent stagnation and flawed realization are just as terminal for a civilization and the life forms that build any given civilization as the more obvious existential threats such as an asteroid large enough to sterilize a planet.

    Best wishes,


  • Tarmen November 11, 2013, 13:24

    I worry. In the known oceanic wilderness, varied levels of species coexist and we can readily observe competition, symbiosis, indifference and predation. There is every type of precedent there for any type of relationship between and among 2 or more alien kinds.

  • Eniac November 11, 2013, 23:06

    Tarmen: True, but none of them have culture, civilization, or intelligence comparable to ours. It is a different game.

  • David Payton November 12, 2013, 0:54

    I think this may be a description of the great filter. At least it could be and i personally think the risk is worth it… It may even give us the upper hand (if needed) in that we might be perceived as strong for our courage!

  • Louis Norman Wells November 20, 2013, 14:09

    Although Earth has been transmitting man made E/M radiation into Space for almost 100 years, by reason of attenuation with distance and the relatively low power levels radiated, but asumming that someone in Space has a detection system of the same order of sensitivity as we now have, it is still unlikely that the most powerful of our transmissions have been detected at distances greater than ten light years . With perhaps one exception. That being the E/M pulse radiated from nuclear bursts during the period of nuclear weapons tests some 40/50 years ago.The reported maximum levels are said to have reached the equivalent of 50 megatonnes of TNT and could have generated EMP’s of the order of ten to the 20th watts/metre squared. Greatly in excess of normal methods of generating Radio waves and hence capable of reaching a much greater detection distance . Detected by any civilisation at our level of advancement they are likely to have been recognisable for what they were, and the obvious conclusions drawn!

  • Louis Norman Wells November 20, 2013, 15:31

    I note that it has been suggested that cancellation [jamming] techniques could be employed as a means of blocking METI transmissions of the type ‘hi there we’re here’! by those who are fearful of the consequences of their reception by a predatory alien . They should appreciate that only the information content of the transmission can be cancelled. The Carrier components of each transmission will reinforce one another and thus increase the probability of detection

  • Andrew Palfreyman January 19, 2014, 5:25

    Were another star system to be “tagged”, one of the obvious next steps would be to improve the detail of the information about that system. To that end, it seems to make the most sense to go install a gravitational focus telescope using one’s own sun as the focusing lens. Claudio Maccone has described and analysed such a system, and the gains to be had over all other known telescope types are truly massive – something like 10^14, from memory.

  • Colin Robinson March 8, 2014, 5:46


    What? A life-form that eats up everything else, and has found a way to spread out thru space?

    It is rather like homo sapiens, if you think about it.

    Probably contact between humans and extraterrestials should be avoided, because of the risks it could pose to the extraterrestrials…