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A Dialogue on SETI

Last October, a conference at the Royal Society looked into “the detection of life, the communication with potential extra-terrestrial civilizations, the implications for the future of humanity, and the political processes that are required.” It was a fascinating gathering, one whose results I’ve been able to study ever since thanks to Keith Cooper, who forwarded videos of a debate there on interstellar messaging (METI) and passed along transcripts of the various panels. Keith is editor of the superb Astronomy Now and is an accomplished writer on space exploration and astronomy, with over 100 articles published. I especially want to mention SETI: Cosmic Call and SETI: Terminating the Transmission in relation to what follows below.

For as Keith and I discussed these issues, it occurred to me that our correspondence in the form of a dialogue was a natural for Centauri Dreams. So here’s a slightly edited version of some recent thoughts of ours on SETI, the strength of extraterrestrial signals, and the possibility of sending return messages to the stars. Expect more in this exchange in the near future.

  • Paul Gilster

Trust a Benford to get me thinking, Keith. In this case, Jim Benford, who along with brother Gregory and son Dominic, has told us so much about the feasibility of detecting and/or building interstellar beacons. As you know, I’ve written a lot about so-called ‘Benford beacons,’ fascinated with the cost constraints that the brothers have been able to establish. We have so little quantitative information to work with when it comes to SETI issues, so having an idea of how we might view beacons in terms of cost optimization was a real plus for the field.

Last week, though, I got into the question of how easy it would be to detect a signal from our Solar System. Specifically, the famous case of I Love Lucy episodes propagating out into the cosmos, and what it might take to receive them — can an extraterrestrial civilization (ETI) hope to make sense of them, or even figure out that they represent an artificial signal? And Jim’s new paper, written with John Billingham (former head of NASA’s SETI program), argues with the help of a lot of math that radio telescopes of the sort we have now couldn’t manage the task. I know you heard Jim present these results at the Royal Society meetings last October.

Image: The Parkes radio telescope in Australia. Credit: CSIRO.

Send us the Alpha Centauri equivalent of I Love Lucy, in other words, and we’ll receive nothing at all. Up the technology a bit to the level of the proposed Square Kilometer Array, operating over a wide range of frequencies and fifty times more sensitive than any radio receiving instrument we currently have, and you do manage to reach further. But even with this, we’re talking about a receiving radius less than 20 light years, and what would be at best a very low data-rate detection. So any civilization remotely at the same level as ours just isn’t going to be able to settle in to watch the Ricardos and Mertzes at all. It would be astonishing if they recognized the signal as artificial in the first place unless they already had our system under close study.

SETI implications? I think so. Back in my shortwave radio days, I used to prowl the radio dial looking for hard to detect signals from the other side of the world, and I think I always believed we would pick up ETI the same way. A chance detection, in other words, a whisper from across the stars that simply told us, for a fleeting moment, that something intelligent other than ourselves was out there in the galaxy. Now I’m thinking that scenario is more and more dubious. If Benford is right — and there are few people whose work I trust as much as Jim — then with our current state of technology, we just won’t be able to pick up any unintentional leakage at all.

Is this a rational answer to the Fermi paradox, that the stars are too widely spaced and intelligent civilizations too immature in their growth for us to be aware of each other? Or do we turn the issue around, and ask what a civilization far more advanced than ourselves would be likely to be transmitting? SETI strategy issues are much in play, and I’d be interested in your take on this latest Benford work. What do you think, Keith — is this helpful in SETI terms? And what about METI, if it turns out that we’re not quite as visible to the galaxy as we thought we were?

  • Keith Cooper

You make some great points Paul, and I broadly agree with all of them. However, we must always be mindful of the assumptions that we are making, so allow me to play devil’s advocate. To highlight this, I want to briefly raise the issue of the Fermi Paradox, which you mention.

I find Fermi’s Paradox to be vastly overrated. How so? Consider what data we currently have on extraterrestrial civilisations (ETCs) – it’s a big fat nothing. We’ve closely surveyed around a 1,000 stars at water hole frequencies, briefly glanced at around a million more, but there are hundreds of billions of stars in our Galaxy. We’ve barely even begun to explore the optical, infrared or ultraviolet regimes with SETI, or search for artifacts of ET origin. So the Fermi Paradox isn’t a paradox of data, as we have none – it’s a paradox of our assumptions. It’s telling us that our assumptions are wrong, and that ET may not be as easy to find as we first thought. It’s a good springboard for new ideas, but I don’t think we should get hung up on it.

Image: Keith Cooper (left), with Michael Michaud (center) and Alexander Zaitsev, at the Royal Society conference.

Paul, you ask how all this ties into Jim Benford and John Billingham’s work and the wider issue of METI. Taken at face value it tells us that Earth remains, to all extents and purposes, invisible at radio wavelengths, and the transmissions that we have made are negligible. Our METI signals don’t even repeat – a cardinal rule in our own search. But what assumptions have Billingham and Benford made?

In this case I feel that their analogies to terrestrial technology and resources may be too strong. They assume SKA-sized radio telescopes, but who is to say that ETCs are not using something larger and more sensitive? We saw how cost optimisation led to the Benford Beacons model – a realistic viewpoint that I applaud – but here it becomes limiting. How do we know that what is expensive for us is expensive for ETCs? We really don’t know anything about their resources, or their motivations.

Furthermore, it was clear from attending the Royal Society debate that nobody could agree on the numbers. Seth Shostak, whilst agreeing that our television signals could not be detected with technology similar to ours at a distance greater than about a light year, pointed out that the Arecibo telescope could detect another Arecibo at a distance of 500 light years, while Alexander Zaitsev disagreed with Benford and Billingham’s assessment of his Cosmic Call message. So I don’t think it is clear-cut yet. Hence why Jim Benford made the call at the end of his Royal Society presentation for all transmissions from Earth to be fully documented so more thorough analyses can be made.

So there is still the risk that we could be detected, and that’s why I think there should be an international moratorium on METI until we know a little more about what is out there. Admittedly human civilisation could be detected by other means, a point of view I’m currently wrestling with, but what do you think Paul? Is it wrong to have a cautious attitude towards METI?

  • Paul Gilster

I think ‘cautious’ is a reasonable attitude toward our broadcasts, Keith, but let me answer your point about extraterrestrial technology first. What you’re driving at is the great question about SETI in general. For fifty years we’ve been listening to the skies in the hopes of detecting a radio signal (and, lately, an optical signal) from a distant civilization. But now we see that radio transmission itself may be a short-lived phenomenon. Go back to the start of our earliest transmissions and you can see that we may be talking about no more than a century or so from the time our own society became radio-capable to the point where most transmissions at whatever frequency are going to be carried through cable and other non-detectable means.

So SETI is currently in a mode of intense self-examination, as you know even better than I, having attended those Royal Society meetings (lucky guy). The whole question becomes, how do we put ourselves into the minds of creatures who are by definition alien? Even if we assume they want to contact us — quite a big assumption, in my view — we still have to figure out what means they would use. Can we predict what kind of technology we’ll use for communications in a scant 100 years? Or, put a better way, can we see the shape of a future breakthrough that might change everything? Probably not. And we may be talking about a civilization that is not just a century but a millennium or, even more likely, a million years or more ahead of us.

The question of detectability has that wild card built into it. We can nail down the numbers — and Benford and Billingham have shown us some pretty hard figures for just how far out our signals are going, even if those numbers are still controversial (I see there was disagreement at the Royal Society). But if there is a risk in METI, it’s that upping our visibility in the electromagnetic spectrum might attract something we know absolutely nothing about. We’re not particularly worried, I wouldn’t think, about a civilization that builds SKAs or their equivalent — if they’re at our stage, it’s hard to see how they might present a threat to us. But that hypothetical species that’s a million years ahead of us would have all kinds of technology at its disposal for detection.

What to do? Two things come to mind. First of all, while we can make a highly educated estimate of how far our signals can be detected by a civilization like our own, I think we have to be aware that a sufficiently advanced ETI could well be aware of us at far greater distance. Alexander Zaitsev has maintained for a long time that our planetary radars would make the strongest detectable signal, although as Jim points out, the signals would be non-recurring and hard to identify. But for a civilization able to work science that is ‘indistinguishable from magic,’ even our far more routine leakage at various wavelengths might still be enough to work on.

I’m not convinced, then, that we can put the genie back in the bottle. But it’s clear that the more we transmit, and the stronger our signals become, the more likely it is that we might be detected. Cautious? Well, I’m not really worried because I suspect intelligent life is rare in the galaxy. But if I were wrong, and considering the stakes that’s an important ‘if,’ I’d want to at least do what Jim Benford recommends, which is to start documenting our electromagnetic output with exactly these issues in mind. And I think conferences like this one at the Royal Society should be expanded to bring in a wide range of disciplines, from anthropology to history, sociology and mathematics. We need many eyes on the issue, from many different backgrounds.

Here’s the problem with your moratorium, though. We’re going to be approaching the point where, absent draconian governmental measures, every company with a product to peddle or Hollywood director with a movie to sell will have more and more power to work with to try a METI broadcast. I don’t see how you stop this brightening of our EMF signature, but that’s the kind of thing I would hope people from different disciplines might kick around at future meetings.

And Keith, don’t you think figuring out alien motivations is way beyond us? It drives me crazy when people start talking about what it would be ‘logical’ for an alien species to do. We have no notion whatsoever about what might drive such a society, as Michael Michaud made clear in his talk at the Royal Society. And our only example of a technological culture is our own. How on Earth do we draw any conclusions based on that single, highly limiting sample? Have a shot at that, Keith — you can have the last word, and let’s plan on tackling Michaud’s insights in a future session, too.

  • Keith Cooper

Paul, you’ve got it spot on. We don’t know anything about what life might be like out there, or how it might think or be motivated, and so allowing our assumptions (such as the idea that advanced civilisations will be inherently altruistic and happy to bestow their knowledge onto us) to be taken as fact is dangerous and limiting. Of course assumptions are all we have at present, but we have to make ourselves aware of what assumptions we’re making, and not reject alternatives out of hand. There’s an awful lot of phase space for debates on SETI and METI to explore. That’s why we need a moratorium, to give us time to discuss all those possibilities. And Paul, you might be right in saying that a moratorium may prove too difficult to enforce, but just because something is difficult doesn’t mean we shouldn’t at least try.

In 1972, Project Cyclops (page 32) recommended that:

“Before we make such a response or decide to radiate a long distance beacon, we feel the question of potential risks should be debated and resolved at national and international level.”

So what has changed? The problem is that we – the astronomical and SETI community and all interested parties – are failing to deliver a balanced debate on METI to the public. As science communicators, it’s our responsibility to present a fair and open discussion before we begin a programme of transmission. We need to avoid sensationalising it, as happened with Professor Stephen Hawking’s comments last year. If, at the end of the debate, the democratic consensus is that we should transmit, then fine. As Michael Michaud told me at the Royal Society, he would stand aside under such circumstances. We will be all the more stronger for just having the debate.

Whatever happens, the debate shouldn’t be left in the hands of just radio astronomers. It should be opened up to historians, anthropologists, social scientists, evolutionary scientists, biologists and so on, and then the public. Paul, you touched on the historical aspect, but the more I study the issues surrounding METI, the more I realise that our own history books are rocky ground.

They’re usually not written by the people involved in those historical events and frequently have skewed perspectives. For example, how many people realise that disease has been the worst enemy in contact, not swords or guns? A 1993 conference on Cultural Aspects of SETI recommended that analogies from previous contact scenarios on Earth should be used only as a rough guide for thinking, not as a roadmap of what contact with ETCs will be like. Furthermore, it also suggested that the best analogies would be ones where contact was via the transmission of ideas between cultures, rather than physical encounters, because a message from the stars is more likely than aliens actually arriving on Earth. Real world examples of this include the rediscovery of ancient Greek science, or the decipherment of Egyptian or Mayan texts. However, we should also be aware that the transmission of ideas – ‘memes’ – could be dangerous, even if their intention is well meaning. A destructive meme could spread like a virus.

I’m not saying we should never transmit Paul; one day, when we’re ready, we’ll reach out to take our place in the galactic community, if there is one. But first we have to explore the Universe more, and understand better both the intricacies of contact and, what I feel is very important, the prevalence of altruism amongst species. Should SETI discover a signal first, then it would be remiss of us not to consider replying in kind – otherwise why are we doing SETI? In such a situation we would at least have some information about the transmitting society, and we could take our time in debating and formulating a reply.

Contact with ET will be unlike any first contact that has come before in human history. We should expect the unexpected, and not rush in with our eyes closed.


Comments on this entry are closed.

  • Alexander Zaitsev February 16, 2011, 13:01

    Very interesting!

    If you want, you can also visit my web Album:

    “United Kingdom, Oct 2010” at:


  • Paul Gilster February 16, 2011, 13:07

    Wonderful photos. I hadn’t realized these were available — thanks so much for the link! That was one meeting I really wanted to attend.

  • Alexander Zaitsev February 16, 2011, 13:10

    Also, please visit web “JOURNAL OF RADIO ELECTRONICS”, May, 2008:


    in order to read my paper:

    “Detection Probability of Terrestrial Radio Signals by a Hostile Super-civilization”, with illustration

    >that our planetary radars would make the strongest detectable signal…

  • Alexander Zaitsev February 16, 2011, 14:35

    It is very easy to lose the way in wood if it is wood from another’s formulas, I guess. To estimate S/N ratio is enough only one classical formula! For example, it is possible to use the formula (1) on page 1111 of this my paper: “The first musical interstellar radio message”


  • The Cosmist February 16, 2011, 15:56

    I’m not too worried about the risks of sending a message. I figure any civilization that is advanced enough to detect our signals and to actually pose a threat to us are probably far more altruistic than we are for the simple reason that they haven’t yet destroyed themselves. More likely, such a species already knows about us, or no such species exists in our galaxy.

    These assumptions could be completely false, but in general I don’t think caution is called for when it comes to exploring the Cosmos. We need to factor in the problem that our technological civilization is not guaranteed to last long, so the window of opportunity where we can pursue projects like SETI and METI may be short. If contact with ETI is important we should risk what could be the most important event in the history of our planet and boldly seek contact now while we still can!

  • Tarmen February 16, 2011, 19:25

    I can imagine that the outlook of creatures from vastly different evolutions will lead to strange encounters . Like dolphins try to communicate with bumble bees. Or like house cats trying to communicate with a tuna fish. Or a wise old elephant trying to communicate with a giant squid.
    Eventually we or they will learn 5 or 10 simple meanings, and then give up. Or sting us. Or eat us. Or we eat them. Or sting them. Huge possibility for clash. I see little likely-hood of a meeting of the minds . Most all of that sci-fi we read is just us projecting our own selves into imaginary ‘others’.
    I think it’s like a jungle out there. Or a maybe an ocean reef.
    Be careful.

  • Astronist February 16, 2011, 20:01

    Hello, Paul and Keith. Thank you for sharing this fascinating discussion.

    Keith said that we have no data whatsoever about extraterrestrial civilisations (ETCs) — “a big, fat nothing”. Excuse me if I disagree.

    We know there are no ETCs in our own Solar System (100 years ago, this was not known). I think we can be pretty sure there are no active or growth-oriented ETCs close to us on an interstellar scale, otherwise they would have a long-standing presence in our Solar System already (a robotic explorer or a full-scale colonisation programme) and no reason to conceal it from us, and in addition their extensive colonisation of their own local system would cause a detectable infrared excess.

    Maybe there could be an ETC in the Alpha Centauri system, though it would have to be a pre-industrial one, not one employing radio astronomers. Something on the level of the Roman Empire. But say a million-year-old active spacefaring ETC within a few thousand light-years would surely be pretty obvious. So we can place some constraints on what might be out there.

    Again, I want to disagree with Paul when you say that figuring out alien motivations is totally beyond us. If they live in the same universe as we do, they must be subject to the same laws of physics. One fundamental restraint, it seems to me, is the ungovernability of society. As rational beings ourselves, we like to think we’re in control of our civilisation, but in fact we’re not, because (as I understand) of a basic law of cybernetics according to which a complex system cannot be fully controlled by a less complex one, such as a subset of it, such as a government. So a civilisation is not really under anybody’s control, and the upshot of this, for aliens as well as for us, is that a global industrial civilisation is surely not stable over say million-year timespans.

    Given a global civilisation such as our own, there are, I would argue, two alternative futures: either it continues to grow, or it falls into decline. If the latter, then it reduces back to a pre-industrial stage, and will not engage in interstellar communication. If the former, if it continues with its industrial revolution, then by colonising its local planetary system it spreads itself over a volume of space large in comparison with the distances which are easily covered by its transport technologies. With its centres of power thus widely dispersed, it ensures its long-term survival: in a mature colonised Solar System, if Earth falls, that does not affect Mars, and Mars can later recolonise Earth.

    I don’t think this is affected greatly by whatever mixture of biological and digital intelligence a civilisation ends up with (nod to Seth Shostak).

    The Drake paradigm is to imagine industrial civilisations sitting prettily on their home planets for thousands or millions of years (a period of time subject to pure guesswork) paying their radio astronomers to do CETI which we can then pick up. I disagree that the Drake paradigm is practical. Either civilisations will decline and fall, or they will colonise their planetary system, from which starting-point expansion throughout the Galaxy becomes practical.

    We are looking for either a world with ruined temples poking out of the sand, or a fully populated Dyson sphere and trails of starship exhaust — or for somebody else like us who is in the geologically brief instant (a few thousand years) of transition between these two long-term stable states.

    The fascinating thing about this subject, which no doubt you will bring out in later dialogues, is that the discussion of ETI is at the same time a proxy for our views on the future course of our own civilisation.

    Oxford, UK

  • Adam February 16, 2011, 23:18

    Contrary to Stephen’s summary we don’t know ETCs are in the Solar System, we just know that if they are, then they’re really quiet about it. Hasn’t been sufficient searches to rule out IR emitting colonies in the Kuiper Belt/Oort Clouds – as Greg Matloff suggested a few years ago – so saying “we know” is premature. There could be thousands of inactive or passive monitoring probes, for example, and we wouldn’t know them from other bits of space debris.

  • Rob Henry February 16, 2011, 23:20

    To my mind psychology today is stymied by commonsense – that is by instinctive interpretations imbedded by our peculiar path of evolution. I think that The Cosmist acknowledges that when he says that he could be wrong about advanced ETI’s being typically altruistic. I would go much further that along our path of admitting ignorance, and to illustrate my point will look at what we think we know about war, a phenomena that also has relevance to alien contact.

    Of the few species that we know to engage in war, almost all are female run hymenoptera societies, yet, from what I have seen most psychologists persist in seeing war as a natural outgrowth of male violence. Even to see human war as an otherwise normal form of conflict may be wrong, as hinted by the following: all other natural types of chronic conflict illicit stress related illness, yet during wartime these symptoms can drop well below normal levels. A well-studied case is Britain during WWII.

    For my part I think that alien contact may be extremely bad for us, even if I can never bring myself to believe that they would entertain the traditions of conquest. IF there is any prospects for METI results, we should not rely on the argument that advanced civilisations must be peaceful if they have not destroyed themselves.

  • tesh February 17, 2011, 3:28

    The main danger from communicating with ETCs is if they are roughly at the same technological level as ourselves or slightly ahead (200-1000 years). If they are at a level below ours then they wont respond because the can’t and if they are far ahead of us they have nothing to gain by communicating. If they are close to our level, then I think we have a lot to worry about. We just have to look at ourselves and the history books. Time after time, when a technologically advanced people have met a less technologically advanced people, the less advanced people have met a rather painful and sticky end…

    This is but one side of the story for me. If we know there is an advanced civilisation out there, then I fear that we probably would not be able to handle it. You could pick from a multitude of reasons for this being the case. I would fear that eventually, we would have a cold war mentality, an us and them situation. Politicians, could easily use the situation and spin it for all sorts of nefarious reasons to suit their “needs”.

    I say lets look and see and sit tight, until our own house is in order.

  • Alexander Zaitsev February 17, 2011, 3:55

    Given the huge distance between the stars, as well as the fact that over 50 years of space exploration, we were able to fly at a distance equal to one light second (“Apollo”, The Moon), it becomes abundantly clear that only radio messages are able to come to Earth!
    My suggestion is: let’s leave hungry alien’s visits for writers of bad unscientific fiction.

  • Ronald February 17, 2011, 8:45

    The Cosmist makes two intersting assumptions:
    1) “(…)any civilization that is advanced enough to detect our signals and to actually pose a threat to us are probably far more altruistic than we are for the simple reason that they haven’t yet destroyed themselves”.
    2) “More likely, such a species already knows about us, or no such species exists in our galaxy.”

    I fully agree with assumption 2, which I why I consider it futile to try and hide. We ourselves will probably have a more or less complete overview of living planets in our MW galaxy (and maybe even in neghboring galaxies) in the course of this century and/or the next few. Interstellar detection is endlessly easier and cheaper than interstellar travel. Therefore dare state that any advanced civilization in our MW galaxy already knows that we are here, maybe not our exact state of affairs, but our presence yes.

    I am not too sure about assumption 1, altruism, though I would imagine that any advanced technological civilization would be able to solve its own problems closer to home, i.e. would not need our planet for real estate or resources (other than knowledge). Comparable to the US being very able to wipe out any Amazon indian tribe but at the same time not feeling any need to do so, on the contrary. The comparison is even more unfavorable for the Amazon tribe: a powerful nation might want certain resources that happen to be in the tribe’s territory. As said, an alien civilization would be very unlikely to travel all the way to us to obtain a vital resource (contrary to the Avatar movie), simply because the economics would virtually always be strongly against it.

    The only rationale for wanting our planet, other than scientific study and some sampling, would be if (potentially) habitable planets appear to be exceedingly rare ánd the alien civilization are emphatic about living on planets (i.e. instead of artificial structures sensu O’Neill, Dyson, etc.). But this seems unlikely, since at least terraformable terrestrial planets should be reasonably common.

  • Ronald February 17, 2011, 9:00

    Brings me to Astronist and alien motivations.
    I think that the only motivation that we can surely say is universal is the drive for survival, self-preservation and self-continuation. For very fundamental and simple biological reasons and the very fact that any species and civilization that do not possess such a drive will per definition go extinct.

    Interestingly, Astronist makes two almost contradictory argumentations: one that a civilization will either continue to expand, or perish, and the other that re-colonization is an option for any widespread civilization (or species I may add). Exactly this latter fact makes it also conceivable that a planetary civilization will continue in a kind of pulsating process of subsequent rise and decline, like continuing oscillations, always surviving and emerging from the dark ages but never getting much further.

    In fact, it is interesting to note that until recently our own planet was examplary of this: different parts of our world and different peoples and nations have known their own renaissances: not just Europe, but also China, Japan, the ‘Muslim world’, etc. Great inventions and ideas were often obtained multiple times in various parts of the world, or by exchange.

  • James N. Benford February 17, 2011, 9:39

    Your commentary is very interesting to me, of course. What I’m doing in my recent SETI-related work (Benford Beacons and their detectability, leakage radiation eavesdropping and the Lucy show claims, detectability of the METI messages) is directed toward making SETI more scientific, which means being is trying to make SETI quantitative. Qualitative statements abound in SETI discussions and can mislead. SETI cannot afford to stay in the qualitative comfort zone and be considered a science.

    I want to elaborate on a few things:

    1) The myth that Earth TV is being watched in the stars is kept alive by speakers who know better but want to use it for comic effect. Seth Shostak takes both positions about TV observability, depending on whom he’s talking to. He recently gave a talk at the SETI Institute where he used slides from the Lucy show without ever saying that they can’t be observed outside the solar system.

    2) Similarly, neither Zaitsev nor any other broadcaster has rebutted my calculations showing the unlikely observability of METI ‘messages’. And by ‘rebut’ I mean showing, not just claiming, some error in my arguments. Such claims should not be repeated without making a quantitative reply. That keeps it in the realm of science, not public relations.

    I also note that there has been no response to my call for documenting the METI transmissions to date, and no calls from their ranks for the conferences we advocate.

    3) I’m not saying that ETI must have our level of technology, cannot do more, hence cannot detect us. What I’m doing, again, is making the discussion quantitative. I show that even a telescope we haven’t built, just conceived, can’t detect us at rather short 20 light year range, within which there are only about 100 F-through-K stars. (I don’t see the SKA being built anytime soon, by the way; it costs $2.5 billion. Being quantitative helps estimate probabilities.)

    If you want to imagine a much larger investment by ETI, you’re making what we have called the Altruistic Alien argument — that rich aliens of great ability and benign intent will listen for our leakage radiation without taking any consideration to the cost. This argument is seldom directly quantified. The Benford Beacon papers have shown such costs to be high in our terms. But this argument meets a conceptual danger: If Altruistic Aliens have great, near-infinite resources, they would find it easy to make themselves apparent in our night sky. If so, where are they?

    4) Many then fall back to asserting that aliens are unknowable in that they are beyond economic arguments. We dealt with that in our ‘Searching’ paper (http://arxiv.org/abs/0810.3966 ): it is an established principle in evolutionary theory that, whatever the life form, evolution will select for economy of resources. That’s bio-economics, a general feature of life from plants to us. Any social alien will be accustomed to cost/benefit arguments, just as we are.

    5) Note that the ‘optical, IR and UV bands have serious background noise competing with the signal, which is why we’re concentrating on microwaves, with the lowest background in the EM spectrum.

    6) The Seth Shostak statement, that the Arecibo telescope could detect another Arecibo at a distance of 500 light years, doesn’t state the details, especially the assumptions: What broadcast time, integration time is assumed? Remember, Arecibo goes over the horizon in less than 12 hours. What system temperature was assumed? I’ve tried to find the source of these Arecibo–to-Arecibo claims, but have found nothing yet. To my knowledge, this hasn’t been documented. Again, we need quantified statements.

  • ljk February 17, 2011, 10:11

    Costs and Difficulties of Large-Scale ‘Messaging’, and the Need for International Debate on Potential Risks

    Authors: John Billingham, James Benford

    (Submitted on 9 Feb 2011)

    Abstract: We advocate international consultations on societal and technical issues to address the risk problem, and a moratorium on future METI transmissions until such issues are resolved. Instead, we recommend continuing to conduct SETI by listening, with no innate risk, while using powerful new search systems to give a better total probability of detection of beacons and messages than METI for the same cost, and with no need for a long obligatory wait for a response.

    Realistically, beacons are costly. In light of recent work on the economics of contact by radio, we offer alternatives to the current standard of SETI searches. Historical leakage from Earth has been undetectable as messages for credible receiver systems. Transmissions (‘messages’) to date are faint and very unlikely to be detected, even by very nearby stars. Future space microwave and laser power systems will likely be more visible.

    Comments: 13 pages

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:1102.1938v1 [astro-ph.IM]

    Submission history

    From: Gregory Benford [view email]

    [v1] Wed, 9 Feb 2011 18:48:56 GMT (380kb)


  • Ronald February 17, 2011, 10:13

    Brings me finally to the Fermi paradox and Drake equation.

    A determining factor in the presence of ETI and ETC is not only the chance of one arising on a planet, but just as importantly it’s survival. We simply have no idea how long a technological civilization survives. But I dare argue that the contemporaneous number of civilizations in a galaxy must be exceedingly low and *the* main reason for the Fermi paradox.

    Just for the sake of argument and the fun of guesstimating, let’s take as a starting point a reasonable estimate of the total number of habitable planets in our MW galaxy. There are a few that come to similar results, see for instance:
    which give estimates from 50 to 200 million truly habitable planets in our MW galaxy.

    Let’s take a medium 100 million habitable planets (the result of the first 3 parameters in the Drake equation but a much lower resul than Drake’s own) and let’s assume that about 10% of those ever develop higher life (a bit beyond the parameter fl of Drake, which is the fraction for all life), that’s some 10 million. And that 10% of those ever develop any kind of self-aware intelligence (fi of Drake), making 1 million. Of which 10% ever develop some kind of culture and civilization (100,000) of which again 10% ever develop a technological civilization: 10,000 (the total result after fc of Drake).
    These are all, except the initial number(habitable planets) rather arbitrary and probably optimistic numbers. It is also reasonable to assume that a sunlike star has a certain window of opportunity during which higher life can survive in the Continuous HZ (after and before conditions become too hostile). For ouw own sun about 1 gy.

    If, just for example, an average planetary techno-civilization survives for 10,000 years (L of Drake, not bad at all, we are just above 1% of that now), and, as the above implies, some 10,000 of those are arbitrarily scattered across 1 gy of time, the chance that any two of those civilizations overlap in time becomes rather small: something on the order of 1% or less. Even Drake himself came to only about 10. Other, more recent, estimates come to about 2 only. Even great optimists come to the conclusion that neighboring civilizations must be a few thousand ly apart on average.

    Hence my assertion that the predominant cause of the Fermi paradox is most probably and simply the extreme rarity of (surviving) technological civilizations.

  • ljk February 17, 2011, 10:37

    James Benford, who and what do you need to document all METI efforts? I strongly agree that *all* such projects need to be recorded in specific places, not just the “scientific” ones that Alex Zaitzev focuses on. Because guess what – as communications technology improves and becomes more readily available to businesses and individuals, more “messages” are going to be sent from this planet into the Milky Way galaxy and beyond. Whether these transmissions are “important” or not or if they can even get past Pluto will not matter so long as the fact is that more and more non-scientists have and will be attempting to shout their presence to the stars.

    ETI are not going to discriminate (at least initially) between, say, the Arecibo Message and the Doritos advert any more than our SETI programs will be picky about the first messages we receive from another civilization. Such examples include Joe Davis of MIT’s amazing 1.5-hour transmission of the DNA of “the most abundant protein on Earth”, to quote the man, sent from Arecibo in November of 2009. At the very least, this clearly artificial signal will strongly indicate to galactic recipients that beings of some intelligence reside in the Sol system.

    These quotes from Keith Cooper in the article are worth repeating:

    “The problem is that we – the astronomical and SETI community and all interested parties – are failing to deliver a balanced debate on METI to the public. As science communicators, it’s our responsibility to present a fair and open discussion before we begin a programme of transmission.

    “We need to avoid sensationalising it, as happened with Professor Stephen Hawking’s comments last year. If, at the end of the debate, the democratic consensus is that we should transmit, then fine. As Michael Michaud told me at the Royal Society, he would stand aside under such circumstances. We will be all the more stronger for just having the debate.

    “Whatever happens, the debate shouldn’t be left in the hands of just radio astronomers. It should be opened up to historians, anthropologists, social scientists, evolutionary scientists, biologists and so on, and then the public.”

  • ljk February 17, 2011, 10:55

    Dr. Paul Shuch of The SETI League looked into whether the Arecibo radio telescope could detect a signal from a copy of itself across the galaxy here:


  • Alex Tolley February 17, 2011, 11:40

    As other commentators have noted, this conversation is still mostly bound up with specific technologies and assumptions about why aliens would “communicate” with us.

    I think a nice parody would be E O Wilson discussing using orbital satellites to “communicate” with an ant colony in Mexico.

    Obviously we don’t communicate with ants, we study them. We may “communicate” in experiments by testing chemicals, changing environments etc. Most experiments try to exclude the effects of the observer, so why might this not be true for aliens observing us – what might their hide be? Generally we study ants up close, not from far away, although, who knows, maybe there is a need for a global ant and termite map of Earth. Similarly, we have tried to communicate with dolphins and killer whales, but these are us8ually in marinas and I suspect their wild cousins know nothing about these attempts.

    If there are aliens out there, and they are very advanced (time suggests that they must be either very advanced or very behind us) and they are interested in earth, they are studying us with local means. Any electromagnetic signals they were sending back to the stars would not be detectable by us, assuming they were using such means.

    As for what the aliens might be like, we have no idea if they would be biological, machines or non-corporeal. They might be all around us now, but either invisible or just not recognizable to us. This is a little like Davies’ arguments for an almost invisible “shadow biosphere” on earth.

    In conclusion, I find much of the discussion on SETI and METI highly reminiscent of the mindset of the golden age of exploration, when Europeans made contact with Pacific island cultures.

    We really should take Haldane’s dictum more seriously.

  • Keith Cooper February 17, 2011, 12:05

    Some great discussion on here, and I really appreciate the interest in our dialogue. I’d just like to acknowledge/respond to some of the great points that have already been made.

    The Cosmist: Good point about the window of opportunity. A few years ago Charles Cockell at the Open University wrote a book, Space on Earth, in which he talks about how space exploration can help us combat terrestrial problems such as climate change and overpopulation, and how our experiences on Earth can help with space exploration. He ends the book warning that if the environment really gets out of hand, we will be devoting so much of our resources to that futile struggle that we won’t be able to afford space exploration anymore. Hopefully those prophecies of doom don’t come true, but I take your point.

    Stephen – you make some interesting points, particularly that we can make a few constraints: we know that the Solar System has not been colonised by ET, for example, although as Adam says there could still be probes here, hidden in the asteroid belt or a Lagrangian point, which negates that argument somewhat. But I’m not sure that those few constraints really help tell us about who is out there; furthermore, I think they hinge on the assumption that ETCs not only must be interested in colonising, but that they colonise the entire galaxy, and expend a lot of energy in doing so. I think those models were based on Fermi’s initial back-of-the-envelope calculations during that famous lunch at Los Alamos in 1950, and other models that suggest a civilisation moving at a fraction of the speed of light could colonise the Galaxy in 50-100 million years. But there are alternatives: Milan Cirkovic recently proposed optimised ‘city-state’ civilisations that explore the Galaxy with probes (http://arxiv.org/abs/0805.1821); Jacob Haqq-Misra and Seth Baum argue that exponential expansion cannot be maintained in their sustainability solution (http://arxiv.org/abs/0906.0568) and of course there is Geoffrey Landis’ percolation model. That these alternatives exist is enough to suggest that we shouldn’t cling too tightly to the idea that ET should have visited and colonised us by now.

    As for motivations: I think we have to be careful not to assume that ET societies are going to be like our own. Could we predict the motivations of a powerful hive mind, for instance, or motivations of AI? I don’t think so, other than it seems fair to say that there’s a decent chance they won’t act like us, and we may not even understand why they act the way they do.

    Jim Benford – I didn’t realise the Arecibo claim wasn’t based on a research paper or some other calculations that could be cited. Speaking as a journalist, to have peer-reviewed, quantitative arguments would certainly help when writing about SETI, to help counter critics’ claims that it’s all a bit vague. I can’t imagine that this situation would be allowed to persist in other scientific disciplines – is the reason because SETI scientists are unwilling to publish, or that there are very few journals for them to publish in?

    Again, thanks everyone for the discussion!

  • Paul Gilster February 17, 2011, 14:57

    I certainly second Keith’s thoughts about the discussion, and thank all of you who have participated so far. The more angles on this we can develop, the better our subsequent insights, and I feel like I learn something every time I check the comments when the level of discussion is this high. Well done!

  • Marc G Millis February 17, 2011, 15:16


    Great discussion here and it would be great to have its essence distilled down to a short summary – impartially (include points and counter points).

    To those out there who have been wanting to volunteer your help to the Tau Zero Foundation, compiling such a distillation (without bias) would be a welcome contribution! I regret that I get too many volunteer requests than I can respond to in a timely matter, so this just hit me as a volunteering idea.


  • Scott G February 17, 2011, 15:18

    I think Ronald pretty much nailed the argument. What are the chances of technological civilizations (at our level, or above) being nearby in time, let alone, nearby in space? The galaxy is extremely large and extremely old. I wouldn’t place two communicating civilizations any closer than 2000 light years from each other (until we come up with some really solid evidence that says otherwise).

  • Tarmen February 17, 2011, 15:55

    Even if our near peer civilizations don’t overlap with us in time, we can still hope to find old old artifacts frozen in long orbits. Or we might fear to find certain such artifacts. I half suspect that, over the ages, lots of old things might have fallen into our sun’s gravity well. Unimaginably ancient long dead probes Or ancient coke cans etc.. Flotsam.

  • The Cosmist February 17, 2011, 16:14

    A few more quick thoughts about this very interesting post:

    1) A link to Mr. Benson’s new paper would be very helpful!

    2) I’m shocked that issues of detectability are still controversial in 2011 when the science is so well understood. I thought this had all been settled 50 years ago!

    3) I don’t think we should commit too many resources to SETI/METI because to me it seems a lot like an appeal to gods. Rather than hoping for contact with some benevolent super-beings who can save us, we need to face the reality that there probably is no such group in our galaxy and it is therefore our responsibility to become such super-beings rather than behaving like religious children!

  • Paul Gilster February 17, 2011, 16:18

    Cosmist, Jim Benford’s latest is here:


  • Adam February 17, 2011, 18:46

    Hi All

    Jim, Sagan & Shklovsky computed the range of detection of an Arecibo by an Arecibo in “Intelligent Life in the Universe” (Chp.27) as 100 ly-100 psc. A pretty tight bandwidth was assumed. It’s a figure that has been around a LONG time.

  • Rob Henry February 17, 2011, 19:26

    Psychology is such a new science that its extension beyond the Earth is foolhardy. Since no one else seems silly enough to go too deeply into the topic of the nature of extraterrestrial minds, I feel free to rush in were you angels fear to tread.

    Even if we assume that the alien mind has been shaped by evolutionary pressures, and not latter technological pressures and designer genetics, what little can we say about them. Surely, when faced with something new, all of them will still have the priorities, “can it kill me”, “can I eat it”, then “can I mate with it”, but none of that seems useful. What we really want to know is do they share any strange personality quirks with humans?

    I have seen a good defence to our reluctance to mate in public being central to the development of a cooperative society. The reasons for our hidden ovulation are harder to discern, and given its large effect on the structure of our society, a lack of this in aliens, should make the structure of their civilisation very different. One of our traits that does seem a fair bet to have in aliens is an inbuilt tendance to ape the action of others, and to learn this way. Surely such natural mimicry would be helpful to prospects of desire for communication. If they come from predatory stock, they may have the ability to project their empathy on other species in order to second guess their movements, and that would look even better for us. Actually I always felt that aliens that were natural predators are far more likely to be well disposed to us than those from other stock.

    Some likely outcomes of alien contact may be driven entirely by the nature of the human mind. Earlier I mentioned clues that war may be nearly unique to humans among civilised societies, but that does not make us immune from its effects. Much earlier in the discussion it was correctly mentioned that European contact with natives was a very poor analogy to the outcome of exterritorial contact, and the example of how different this was, was that of introduced diseases being responsible for most of the New World death toll. One of the few places were disease was only a minor factor was in my homeland of New Zealand, so perhaps it should be noted that the bloodiest effect was of natives with European contact fighting wars of conquest with ‘advanced’ weapons against other tribes with fewer contacts.

    Looking at combined effects from human and alien psychology, I can’t help but note how difficult it is to compare intelligence across species. The humans communicating with ants analogy was mentioned above, but even if our intelligences are comparably, I see a grim factor. I wonder if we have really proved that all species of whale are less intelligent that us even at just the p<.05 level. If so, wouldn’t our continued hunting of them while we simultaneously pushing for equal rights among all humans look especially bad to alien observers. It is almost as if whale hunting (until the point at which we have proved them less intelligent) is designed to minimise any potential alien empathy with us.

  • Chris T February 17, 2011, 19:56

    Even ignoring the potential risks, what possible benefit is there to transmitting signals to random stars? The only rationale for METI at this time seems to be ‘because I can’.

  • Astronist February 17, 2011, 21:13

    Keith, thanks for your comments. I took a look at Haqq-Misra and Seth Baum. Their paper is very scholarly, but doesn’t make too much sense to me. They keep on talking about “exponential” expansion of a civilisation into the Galaxy, when this is obviously impossible on grounds of elementary geometry. Then they offer “slower growth” as an alternative, without once quantifying the rate of growth they’re thinking of or the time taken for it to spread around the Galaxy. And on p.6 they suggest that a civilisation can collapse on a solar system scale and even a galactic scale, when it is surely obvious that the impact of the collapse of say Earth’s civilisation will have little effect on a mature colony out in the asteroid belt, and no effect at all on a colony in the Alpha Centauri system, let alone further afield. And they rely heavily on analogies between space colonisation and terrestrial colonisation by humans, with no recognition of the differences between these two things. So I am not impressed by their logic.

    Regarding their key point: they claim that the sort of growth needed to colonise the Galaxy “is not a sustainable development pattern”, but I don’t see that they have demonstrated this at all. They have only raised it as a possibility.


  • Alexander Zaitsev February 18, 2011, 5:02

    I suggest to return to the declared theme: Royal Society Conference in Kavli Center!
    Seth Shostak thesis is here: “Should we make deliberate transmission to putative extra-terrestrials? This question, which has roiled the SETI community in the past, is rooted both in PARANOIA and a mistaken impression as to the detectability of Earth. There is much to be learned in an active transmission experiment, and there is demonstrably no risk in doing so. Consequently, attempts to proscribe broadcasts towards the skies are not only impractical, they are ill-founded”. (Book of Abstracts, page 6).

  • Astronist February 18, 2011, 9:09

    Keith, thank you also for ref to the interesting paper by Cirkovic on city-state versus empire-state civilisations.

    I’ll need to think carefully about his arguments, tho there’s much here I disagree with straight off. For example, the idea that a post-human civilisation will also be post-biological. Basically, I’ll believe this the day I hear that computers are having better sex than flesh-and-blood humans — until then, it’ll be the intelligent computers who want to be humans, not the humans who want to upload themselves into digital devices. I don’t think we’ll shake off our biological heritage as easily as that.

    In other words, the idea that the future belongs to pure, cool, digital intellects processing information with ever-increasing efficiency is a product of an over-intellectualised view of life. In reality, quality of life is just as important a criterion as intellect, if not more so, in deciding how to live — and this will apply to any intelligent beings arising from biological evolution. So biologically derived motivations for interstellar colonisation can’t be dismissed as obsolete as easily as Cirkovic does at the start of his article. But obviously, this needs more analysis.


  • Alex Tolley February 18, 2011, 11:35

    @ Astronist:
    “I’ll believe this the day I hear that computers are having better sex than flesh-and-blood humans”.

    It depends on your meaning of “better sex” but consider. Long ago it was shown that rats rewarded with jolts to the pleasure centers would self stimulate to the exclusion of eating. The massive growth of online porn suggests humans try to do the next best thing. A recent study showed that recent university students would prefer a compliment on their work or a better grade in preference to sexual favors. Let’s not forget those medieval monks abstaining from sex in order to get closer to god. And finally some people are wired to enjoy pain, with fMRI studies showing that the brain lights up in the same way a normal person ‘s does under pleasure.

    So I wouldn’t be too quick to assume that humans want “better [biological] sex” , nor that the digital realm cannot create the equivalent of a pleasure center in non-biological brains or substrates, and what it might be wired to, to stimulate it. Those cool, machine intellects may well be getting the equivalent of great sex by solving great intellectual problems…

    As has been discussed elsewhere, we know the current difficulties of transporting biologicals across space. This suggests to me that we might expect first contact aliens, or their emissaries, to be non-biological, just as our dominant form of exploratory craft in space are machines.

  • Alexander Zaitsev February 18, 2011, 15:04

    To: Chris T.

    In order try to understand

    >rationale for METI

    please visit:

    to read Chapter 21:
    Alexander L. Zaitsev. METI: Messaging to Extra-Terrestrial Intelligence, pages 399-428.

  • Chris T February 18, 2011, 16:17

    So we’re going to spam the galaxy because we feel lonely? Wouldn’t popping a prozac be less expensive?

  • Bounty February 18, 2011, 20:00


    I have to disagree with you, as I’m 1/3rd Native American and I’m not sticky or in pain. Also I’m very happy that someone came along and civilized us, otherwise we’d be chatting by smoke signal. (My Native American grandma agrees.)

    @ Alex Tolly

    “If there are aliens out there, and they are very advanced (time suggests that they must be either very advanced or very behind us) ”

    I’m not sure we can assume that time = very advanced. The most advanced any civilization can ever hope to achieve may be where we are in 100 years.


    I don’t think we can assume aliens or our future selves have defeated gravity, biology or space. I honestly don’t believe space travel gets too much easier. Sending a probe to Alpha Centauri is doable, it will probably never be easy. A manned mission, that stops/lands there, is going to be incredibly tough. I could visualize an alien civilization which reaches a peak which puts 20+ lightyear travel out of practical reach. They would still have advanced telescopes, possibly colonize and terraform nearby systems though. How many years it would it (us) last? I think that is a very important unanswered question. Also I think close to the galactic core where stars are closer together, life may be hazardous. Further out, and you bump into that 20+ lightyear distance easier. That could make small clusters of civilization the norm, or max.

    One last thing. My opinion is that METI is equivilant to saying “is anyone there.” I mean that literally. If you’ve ever said that out loud, you probably shouldn’t be arguging against METI. (Well, other than for cost reasons.) Maybe you’re home alone, maybe your wife is in the kitchen making dinner, or maybe a burgler is now looking to hatchet you. I don’t know about you, but I don’t go sneaking around my house looking for people when I get home from work. My opinion is based on our numerous other broadcasts that haven’t led to our deaths. The only thing new here is a higher bit rate. I guess if we were talking about building a new very powerful transmitter we’d have a discussion.

  • Alex Tolley February 18, 2011, 21:12

    I agree it does not necessarily follow that time allows for highly technically advanced civilizations. All we have is our history and the lack of evidence that there are any obvious limits to scientific and technical advance. Without any roadblocks, we have to assume that we can continue to advance, and that if there are other civilizations out there, they too will face similar conditions. It only takes one civilization to advance to super civilization status, even if most fail. What their capabilities could be, we don’t yet know, but I would bet on too many limitations given the state of our knowledge.

  • Adam February 18, 2011, 22:12

    Here’s a thought, aside from all the others I have offered in similar discussions to this one – what if stars worth visiting are too far apart for practical thinking species and so they settle for just listening, perhaps eventually mounting a physical cultural exchange once Contact has occurred. How far apart do worthwhile star systems have to be before a species, for economic reasons, decides it can’t be bothered trying to “conquer” the stars?

  • Alexander Zaitsev February 18, 2011, 23:53

    To Chris T:
    All is much easier – my outlook and your outlook very strongly differ from each other. Therefore we never can understand each other. Besides, I am not able so quickly to read – you have read Chapter 21 of all for 1 hour. I have simply nothing to tell you more.

  • Rob Henry February 19, 2011, 7:12

    Before I criticise some of the Astronists conclusions, I feel obliged to mention that I love the way that he recombines facts de novo instead of just following the crowd. Who can forget him dismissing exponential growth as the pattern for galactic colonisation “on grounds of elementary geometry”. Had I been writing I would have felt obliged to flesh it out by saying something like “if we feel tempted to use geometric growth as a driver for galactic expansion, we should think of our current human situation. Take a low natural human population growth rate such as 1% per annum, and note that, if somehow maintained, it would lead to an solid ball of humans expanding at close to the speed of light in just 11,000 years. Since models for galactic colonisation take in the order of a few million years, this gives a feel as to why it is very hard to model galactic colonisation as an exponential process.” Even here though we can easily imagine exponential growth as responsible for the establishment of the core of a budding galactic empire. The establishment of this core should represent the irreversible step, after which complete galactic colonisation becomes inevitable. His assumption that any interstellar civilisation is immune from collapse, while probably true, is not insurmountable. The great depression was caused by the spread of an idea – that banks could collapse if people panicked and withdrew their money from them. Surely even an interstellar empire is not entirely immune from the spread of an idea. Thus Haqq-Misra and Seth Baum were not too bad.

    But all the above it just quibbling, I write because I am deeply uneasy about is his seemly benign assertion of 16 February that a more complex system cannot control a less complex one, its extension to governance, and, in particular, its further extension to a general rule that can be followed when considering the stability of any single system alien society. The postulate seems so logical when you just add the distortion of our commonsense. We humans naturally seek to control other humans, rather than processes. I feel that this explains why when we really are desperately seeking a singular goal, as we were during the Apollo missions, progress is spectacular compared to if we have more general goals, such as during the shuttle programme. For humans all power is bluff, and face is everything, actually spending time on their designated job is a luxury that few at the top can afford much of. Furthermore their firm grip on underlings makes them look in charge. Actually all conspiracy ‘theories’ seems based on the popular belief that total submission of underlings is equivalent to total control. Since the more scientific of us realise the fault, we are tempted to believe that lack of control of outcome is universal.

    If we now imagine a very different intelligent species that genuinely aims to control the gross outcomes of its society, everything looks different. It is true that they could never gain complete control of such processes for reasons given by Astronist, but they only need enough control that it would make no practical difference between this and truly complete control. If so, a well founded such society inhabiting a single system really can last forever.

  • Chris T February 19, 2011, 21:09

    Alexander – The problem (besides the sheer hubris required to think one can speak on behalf of all humanity) is the sheer scale of any effort likely to have any chance of success at this time. There are an estimated 300 billion stars in the Milky Way galaxy. Even if we think only 1% have any chance of holding intelligent life, that’s still 3 billion stars. On top of that, if you want your signal to be unambiguously artificial, you must maintain it for a time for each star.

    That’s one heck of a lot of resources to expend for very questionable and unlikely benefit centuries or millenia down the road. We’re beginning to map planetary systems around other stars, would it not behoove us to wait until we have a far better idea of where even to send signals? It would seem vastly more efficient than targeting random stars now.

  • Alexander Zaitsev February 20, 2011, 4:36

    To Chris T:
    In the Wiki Category “Interstellar messages” (IMs):


    it is very clearly and very intelligibly written that all IMs, which were sent from Evpatoria Planetary Radar, are the private initiative. People spoke on its own behalf! And people have a just cause on similar performances. The freedom of speech and a freedom of expression is guaranteed by the Constitution.
    You see, your pathos
    >speak on behalf of all humanity
    is incorrect and inappropriate.

    P.S. By the way, all attempts of an interdiction of the METI are based on myths! The aliens travelling on boundless open spaces of the Universe is a myth! Superaggressive and gluttonous aliens are a fruit of sick imagination.
    It is not necessary to forget that gluttonous monsters waited for medieval seafarers on border of the Earth.

  • intercostal February 21, 2011, 4:58

    I do not think the idea that ‘aliens would be altruistic or they’d have destroyed themselves’ is true; the same tech needed for a nuclear war lets you build a ‘Project Orion’ – it’s pure politics that we didn’t.

    For that matter, does technology necessarily presuppose ‘intelligence’ in the broader sense we tend to mean it? I see no a priori reason to rule out beings ‘intelligent’ (in the narrow computational sense) enough to build spacecraft but which are not *people* — there would be nothing to communicate with, at least beyond the level we can communicate with parrots or apes.

    Hello, Paul and Keith. Thank you for sharing this fascinating discussion.

    Keith said that we have no data whatsoever about extraterrestrial civilisations (ETCs) — “a big, fat nothing”. Excuse me if I disagree.

    More specifically:
    “One fundamental restraint, it seems to me, is the ungovernability of society. As rational beings ourselves, we like to think we’re in control of our civilisation, but in fact we’re not, because (as I understand) of a basic law of cybernetics according to which a complex system cannot be fully controlled by a less complex one, such as a subset of it, such as a government.”

    I think this statement involves unexamined assumptions about the nature of society and government — specifically, the existence of a government as a *subset* of society trying to *control* that society. Both those terms are crucial — we require governments (ie constraints) largely because following our instincts leads to chaos and an unworkable society; I see no reason to assume this is true of all possible intelligent species. A species which developed a functional social order as a natural outworking of its instincts would not need ‘controls’ in the sense of something imposed — it would likely not have a ‘government’ that could be distinguished in any way from the society as a whole (even as a subset of it), or possibly even from its biology/psychology.

    “Given a global civilisation such as our own, there are, I would argue, two alternative futures: either it continues to grow, or it falls into decline.”

    Only with a narrow definition of ‘such as our own’. I will agree that our current civilization could not exist at the same economic and technological level for centuries, millennia or more. But I am not sure that is universal even among human societies (a civilization whose ideology crippled the development of science, which existed in a sufficiently that natural changes such as climatic shifts did not force change, and which was sufficiently isolated that invasion etc. were not a threat could probably do so.) Especially if the civilization were purposely designed for long-term stability.

  • Ronald February 21, 2011, 8:41

    Chris T: “There are an estimated 300 billion stars in the Milky Way galaxy. Even if we think only 1% have any chance of holding intelligent life, that’s still 3 billion stars.”

    Chris, although I agree with your general idea for a different reason (see further), forget this kind of figure, even the greatest Drakean optimist would dismiss it.

    I would rather say that maybe 1% of all those stars may harbor a planet with any kind of life, at the most. The percentage of those that may have intelligent life must be extremely small, probably just a few for the whole MW galaxy at the most.

    Exactly for that reason we should be highly selective and go one step at the time, doing first things first: first and foremost we should get a reliable and reasonably complete picture of planetary systems in our galactic neighborhood, then, by spectroanalysis, find the planets that host (any) life, finally try to find out whether any of those host intelligent life.

  • Michael A.G. Michaud February 23, 2011, 11:50

    This discussion is a good example of how much more sophisticated the arguments about contact have become since I first got involved in this debate thirty years ago. One positive trend, at least among those people who pay attention over time, is that more have recognized the complexity of this question. One hopes that the days of single-factor analysis are behind us.

    I was struck by Keith’s observation that science popularizers have failed to deliver a balanced debate to the public. The lack of balance is painfully obvious in films and television. Over the past year, I have been approached by three different companies producing television documentaries on the possibility of hostile contact. I was surprised to find that the tired stereotypes of mother ships, flying saucers, and alien storm troopers landing on Earth are still in force. When I suggested a more balanced approach, I was told by one company that they felt compelled to use “iconic images,” as if we are permanently locked into a previous era. Another company said that an alien invasion, and human resistance to it, made a better story than the more complex possibilities I suggested. If major media continue to present simplistic scenarios, we can expect more ridicule.

    One of the tired assumptions that many still make is that there are only two scenarios of contact: either we will detect a signal sent by extraterrestrials eager to communicate with us, or alien space ships will descend on us. Few scientists seem willing to recognize the possibility of alien robotic probes, which can be much smaller than inhabited spacecraft and much easier to propel over interstellar distances. A few prominent scientists have been so blinded by their assumptions that they declare interstellar flight to be impossible. (To his credit, Seth Shostak acknowledges that such flight is not impossible.) Also missing from the public discussion is the discovery of astroengineering or other artifacts of technological intelligence that are not aimed at us.

    Keith made the useful observation that the so-called paradox is not a paradox of fact, but a paradox of our assumptions. We do not have enough information to conclude that technological civilizations do or do not exist elsewhere in our galaxy.

    Paul emphasizes one of the points some of us have made for years: we need to bring in people from a wider variety of disciplines. I would add another dimension: we need to bring in people from the world’s most populous continent. The only Asian at the Royal Society meeting was a U.N. official from Malaysia. Where are the Chinese, the Indians, the Japanese? We Westerners are not the sole repository of wisdom.

    I look forward to further discussions on this fascinating issue.

    Michael A.G. Michaud

  • Eniac February 26, 2011, 12:06


    Interestingly, Astronist makes two almost contradictory argumentations: one that a civilization will either continue to expand, or perish, and the other that re-colonization is an option for any widespread civilization (or species I may add). Exactly this latter fact makes it also conceivable that a planetary civilization will continue in a kind of pulsating process of subsequent rise and decline, like continuing oscillations, always surviving and emerging from the dark ages but never getting much further.

    Any contemplation about the “low density” of “civilizations” as the reason for the absence of ETI signals is based on the assumption that interstellar expansion is impossible, and that strikes me as completely untenable.

    What is usually not recognized in this discussion is that the spread of a species in the galaxy is not at all like the growth of a complex organism, it is like the growth of bacteria in a Petri dish. This is because the enormous isolation between colonies makes them by necessity independent. There can be no “empire”, not even a coherent “civilization”. As a consequence, there are no internal limits to growth, and the sole external limits are availability of a substrate (livable star systems) and possibly competition. That means that even a single (yes, just ONE in the entire galaxy) society capable of colonizing nearby star systems (and all it takes is travel over 5-10 ly) will fill the galaxy (inhabit every single star system) within a few hundred million years. That this has not happened irritated Fermi, and it remains standing as important evidence that we are alone in the universe. The alternative would be that none of the other presumed civilizations ever moved to colonize the stars, not a single one. That is no less irritating than being alone, in my opinion.

    In fact, it is interesting to note that until recently our own planet was examplary of this: different parts of our world and different peoples and nations have known their own renaissances: not just Europe, but also China, Japan, the ‘Muslim world’, etc. Great inventions and ideas were often obtained multiple times in various parts of the world, or by exchange.

    You should realize that all this “limits of growth” history you mention here happened long after humanity expanded to completely cover the face of the Earth. The growth of humanity did not stop until the substrate (livable land) ran out. This happened in prehistoric times, during the expansion out of Africa, and before that within Africa, too.

  • Ronald March 5, 2011, 7:14

    Eniac, interesting and I fully agree, but: aren’t you making an argument that there are no other technological civilizations in our MW galaxy, for if there were they would have colonized the galaxy and we would have known?

    The alternative is that intelligences and civilizations come and go too quickly or they stay in a too primitive state, hence no intelligence ever colonized our galaxy.

    Agree, or am I misunderstanding you?

  • Eniac March 6, 2011, 3:11

    Yes, essentially that is right. As I have listed elsewhere, I see 4 increasingly contrived explanations:

    1) We are the only life
    2) We are the first life
    3) Life NEVER makes it to the stars
    4) ALL life among the stars is hidden from us somehow

    I think that this is pretty much following Fermi’s argument, but I might be wrong there. In my view, 1) is the most likely answer, and it is because life is so very unlikely to form. Some might argue this, but I make no distinction between life, complex life, intelligence and technology, because I see the latter as inevitable consequences of evolution, or at least much more likely compared with the biological Big Bang, abiogenesis, which does not have evolution to explain it.

  • Ronald March 6, 2011, 10:57

    Eniac, thanks.

    I would however prefer to make the clear distinction between any life, complex life and intelligent life. I think that the biggest gaps to bridge in the history of life were:
    – first life (abiogenesis)
    – Eukaryote cell
    – complex (specialized organs)

    Compared to this, indeed inteligence seems a much smaller hurdle to take.

    It is very well possible that our MW galaxy and the universe are teeming with primitive life, and complex life being very rare. On our own planet life has been present as single-celled for most of its history. First life appeared at least 3.8 gy ago, first Eukaryotes about 1.8 – 2 gy ago, first simple multicellular colonies about 1.2 gy ago, first simple organisms with specialized organs (i.e. complex life) 0.6 gy ago.
    So we could say that for at least 80 – 90% of its presence on earth, life was exclusively single-celled or simple cell colonies, and first complex life appeared after almost 4 gy.

    Hence, to be more specific, I would really prefer to have your 1) restated and fine-tuned as “we are the first intelligent life in our MW galaxy”.

    For the same reasons 2) is only relevant with respect to intelligent life, so I think that that one should also be restated as “we are the first intelligent life”.

    3) seems ok (if life makes it to the stars it will have to be intelligent life), with the possible exception that a civilization might be able to make it to a planet orbitting the other component of a (wide) binary star system (such as Zeta Reticuli or 16 Cygni) but not across truly interstellar distances. After all there is a very significant difference between a few hundred or even few thousand AU (say up to 0.1 ly as for the Zeta Reticuli pair) and several ly.

    For 4) I would just make the same distinction as for 1) and 2): intelligent life.

    In the not so distant future we may discover by means of advanced spectral analysis methods that life is quite common (i.e. not hidden at all). That would still not answer the Fermi Paradox.