Understanding the controversy over "Messages to Extra Terrestrial Intelligence" or METI requires a grounding in the history and rationale of SETI (Search for ETI). Insights since the turn of the century have changed SETI's scientific basis. Persistent null results from the radio search do not invalidate continuing effort, but they do raise questions about long-held assumptions. Modified search strategies are discussed. The Great Silence or Fermi Paradox is appraised, along with the disruptive plausibility of interstellar travel. Psychological motivations for METI are considered. With this underpinning, we consider why a small cadre of SETI-ist radio astronomers have resisted the notion of international consultations before humanity takes a brash and irreversible step into METI, shouting our presence into the cosmos.
The mystery of the Great Silence  or "Fermi Paradox"  has joined the Drake Equation as a key metaphor in appraising both the possibility of Extra-Terrestrial Civilization (ETC) and our own prospects to flourish as a progressive, outward-looking species. In simplest form, the Paradox states the obvious, that a vast majority of humans today, including astronomers, are unaware of clear evidence for the existence of ETCs. All participants in the broad discussion agree that — if anyone truly is out there — they are more difficult for contemporary 21st Century humanity to perceive than optimists of the 1960s expected. (See a resource list below for works that deal in-depth with this complex subject, whose history goes back many centuries.)
More than a hundred hypothetical explanations have been catalogued  for the absence of not only signals, but evidence of past physical visits to our planet, or any of the great interstellar works that some forecast our descendants will achieve. As Michael Hart , then Jones and Finney  pointed out, this quandary grows more difficult by far, if we accept the possibility of interstellar colonization — either by biological sapients or by self-replicating probes. This demands that a factor be added to Drake's Equation, accounting for hypothetical "colonization or ship speed." When significant, this factor dramatically expands the Drake estimates, because detectable colonies (or active probes) would be expected in locales far more numerous than the sites where ETCs originally evolved.
Hypothetical explanations for the Great Silence have sometimes been called "fermis" for short. Fermis range from some that are chillingly plausible all the way past unlikely to the nearly impossible. These generally involve suppressing the estimated value of one or another factor in an expanded Drake Equation. In addition to colonization speed (which some disputants set at zero), such an expanded version must also include detectability cross sections, because many fermi hypotheses posit reasons why aliens might be difficult to notice.
The key point is that each "fermi" must have one trait, that of explaining the paradox by suppressing the overall estimate for ETC pervasiveness, so that it lies below our current experience, especially the sampling density derived so far from the Cosmic Haystack probings of to-date SETI experiments. Indeed, for a fermi to rank highly, it must account for the effect that any exceptions might have on the observable universe. For example, even if 99% of all ETCs become addicted to virtual reality realms that are far more voluptuous than cold-sterile space, causing them to huddle home where the bandwidth is high, that only means the remaining 1% that colonized would soon dominate the galaxy.
Moreover, while SETI researchers take pains to claim that the Cosmic Haystack has been barely sampled in area-frequency-coding space, the same cannot be said for the space of possibilities, whole swathes of which have been eliminated — including the gaudy "tutorial beacons" that advanced ETCs would supposedly erect, blaring helpful insights to aid all newcomers along their rocky paths.
As Michael Michaud put it in Contact With Alien Civilizations: "Drake admitted that the negative results... do imply that there are no large numbers of civilizations transmitting at many frequencies, at least not lately." Something has kept the prevalence and visibility of ETCs below our threshold of observation, And while this may change tomorrow (note: all of the METI skeptics or "dissenters" are fervent supporters of funding for expanded passive-SETI research), it is by now clear that something — some unknown effect — is keeping the nearby cosmos more barren-looking than we expected. A collection of classic SETI papers, gathered by Kuiper and Brin, show how far back the argument goes .
Another term for this is the "Great Filter" . In other words, some effect that spans galactic distances appears to be filtering the number of observable, advanced ETCs down to a level where their failure to be noticed can be explained away with the common saying among SETI folk: "Be patient. We just haven't found them yet."
Alas, in a scientific field that lacks any known subject matter, many otherwise bright participants tend to seize upon one "explanation" and deride all others. A recent example caught public attention when the eminent theoretical physicist Professor Stephen Hawking suggested that humanity should keep silent and not attract attention, because alien civilizations might (a) be attracted to Earth and (b) possess the means to travel faster than light and (c) come to plunder our resources. While none of these components are precluded absolutely... indeed (a) & (c) have precedents in the histories of past, predatory inter-human first contacts... the whole scenario seems far-fetched for a raft of reasons we will not go into here. I raise this event only to exemplify that many prominent people, even top scientists, have weighed in, without first immersing themselves in the full range of ideas that are already catalogued, or engaging in open give and take.
As it happens, there is a certain predictability as to which "fermi" or scenario for the Great Silence a person may choose. And this is where we must take a pause to pick up a tool — the Drake Equation, since so much of what follows will refer to it. This formula, well-known by millions, remains the most widely accepted tool for xenological speculation, even though its traditional form predicts absolutely nothing that might be testable or observable.
Let N = the current number of technological civilizations currently in the galaxy. Then,
N = R P n(e) f(1) f(i) f(c) L
Here R is the average rate of production of suitable stars since the formation of the galaxy, approximately one per year. The other factors include n(e), the number of planets supporting liquid water and other life-ingredients, per suitable star; f(1), the fraction of these congenial planets on which life actually occurs; f(i), the fraction of these on which "intelligence" appears; f(c), the fraction of intelligent species that attain technological civilizations, and L, the average lifespan of each species. In its classic form, the Drake Equation does not even attempt to correlate with an actual observable. You must always then massage it, asking "what should we actually see?" It is also short several factors.
A modified version  attempts to convert the standard Drake Equation into a version that predicts an observable, thus letting us derive the number of technological species that might be currently visible to us. And since we know of no aliens (so far), that output number must be set at one (representing humanity) and the factors adjusted accordingly.
What factors or estimates should be added to the classic equation? We must start by including all likely colony worlds that a species might have settled, not just its point of origin. Plus, if we are relating all of this to observation, we need factors for "approach/avoidance/visibility" or how likely each species is to be noticed by us, if we stare right in their direction. For example, a race that took to living within comets in the distant Oort Cloud fringes of stellar systems would gain access to more living volume than offered by the surfaces of all the galaxy's watery Earthlike worlds! But they would be very hard for us to notice. One that builds garish Dyson Sphere habitat structures that envelope whole stars might be a bit harder to miss. Hence, we need these added factors:
V(i) = each tech civilization's average ship speed or rate of expansion. L(i,c) = the average duration/lifetime of each colonized site. A(i) = the visibility cross section of that species and site.
If this sounds like quibbling, consider: we now can take nearly all of the hundreds or so hypotheses that have been offered about the Great Silence and assign them to factors in the modified Drake Equation. It is now a tool for organizing the debate.
For example, those who are part of a general community of "uniqueness" proponents — stretching back to Hart and Finney & Jones, leading to Ward & Brownlee  — tend to pick one or another of the factors on the left side of the Drake Equation to suppress. These are factors having to do with the origination of species like ourselves. They explain the absence of evidence for ETCs by positing that good, stable planets with liquid water on the surface may be rare, or that such worlds may develop life with less alacrity than apparently happened on Earth, or that other living worlds experience catastrophes at much higher rates than our placid planet. We live in a golden age for studying these factors. Not only are extra-solar planets being found at a rapid clip, but recent discoveries suggest that the universe may throng with "roofed" worlds like Europa and Enceledus, whose oceans are protected by icy ceilings, not requiring the contingent stability of an Earthlike "goldilocks zone." So much expanded real estate with liquid water might seem likely to expand the Drake output; but not if the resulting life forms fail ever to interface with the sky outside their icy ceiling.
I find more plausible those uniqueness proposals which argue for low values of f(i), the rate at which worlds develop technology-capable intelligence. Recent discoveries of linguistic and tool-using ability among monkeys, parrots, corvids, prairie dogs, sea lions and even octopi suggest that intelligence among higher animals may cluster against a glass ceiling, just below the abilities of dolphins and apes. If so, and if that ceiling can be shown to have strong Darwinian reasons, then the human anomaly might be truly rare, even unique across the galaxy.
I have also catalogued many fermis that purport to explain why intelligent races may only seldom develop detectable technology, or that they might relinquish such abilities, or else move beyond our modalities into realms that make them successively harder for primitives like us to perceive.
What seems more interesting than any specific theory is what appears to be an emotional driver among those in the Uniqueness Camp — a desire to believe that whatever is suppressing the numbers must lie behind us. "The Great Filter" that keeps Galactic ETCs rare or unobservable is something unique about the path that brought us here, and therefore we can now look ahead to a pitfall-free destiny ahead of us and a mostly-empty galaxy that our descendants will blithely and happily fill. Thus we see that those who at first appear pessimistic are — for the most part — sunny and cheerful fellows.
The opposite effect can be seen in members of the classic SETI community. Clinging to the original estimates of Sagan and others, for high values of f(l), f(i), f(c) etc, they want to believe that life and intelligence and emergent tech-ETCs are common. Only, that leaves them with a Great Silence to explain. And they do that by suppressing factors on the right side of the Drake Equation.
For example, Carl Sagan famously posited that humanity must grow up or else annihilate itself via Nuclear Winter. Further, Sagan generalized that all those other species out there who passed through a similar phase, and who did not cure themselves of their aggressive tendencies, would wipe themselves out. Aside from political and moralizing motives, this also provided a polemical tool to accomplish several more ends. First it provided a filter to reduce Drake Equation outputs, but a filter that's compatible with a fecund cosmos, teeming in life and proto-intelligence. Second, it envisions a universe whose overall condition fits one of the favorite SETI dogmas — that advanced and powerful life forms will tend to be altruistic, or at least benign, because those who weren't — those who were combative or aggressive — would eliminate themselves.
A third benefit to Sagan's scenario was that it allowed a bonus: an assumed reduction in that pesky factor — the ship or colonization speed. Sagan intelligently realized that some form of interstellar travel is probably possible, if difficult. But he could eliminate the effects that colonization would have upon Drake estimates by insisting that those ETCs who survive their danger-ridden adolescences and eliminate aggressiveness will also reduce to near-nil their eagerness to expand. Of course this logical conclusion is easily refuted with a counter example from real nature: rabbits are unaggressive, but very expansionist. Moreover, Darwin will reward the children of the few expansionists in a species. Those whose traits led them to colonize even one new world will be the ones to send forth further waves, taking those traits throughout the galaxy.
Others in the classic SETI clade have seized upon variants of Sagan's theme. Some offer reasons why ETCs might seem less detectable — for example the fact that our Earth is now much "dimmer" in the age of fiber-optics than it was when TV stations and cold war radars blared across the skies. If advanced ETCs were hyper efficient — and weren't broadcasting prodigious beacons — then it might take a while longer for us to build instruments good enough to detect their minor leakage.
Others, such as the late Dr. Barney Oliver  attempted to prove that interstellar travel of any kind — even self-replicating probes — was virtually impossible, a view well-refuted by the late Dr. Robert Forward .
The fascinating psychological aspect to all of this is that SETI community members do not deny the blatant need to "filter" the numbers down below what we observe. They differ only over which factors of the expanded Drake Equation they choose — those on the right side. By picking species lifetime and ship or colonization speed, or detection cross section to suppress, they can model a level of sparseness of detectable ETCs to match any cosmic haystack result and still say: "any day now we'll find 'em."
Ironically, by presuming that ETC numbers are winnowed by death and failure, and then calling starship colonization and travel next-to impossible, it would seem that the "optimists" in SETI are not as sunny of disposition as many in the uniqueness crowd.
But it does not end there.
Any serious attempt to catalogue and compare "fermis" or hypotheses to explain the Great Silence should begin — we've seen — by arraying them along an expanded Drake Equation. It's been thirty years since that job of cataloguing has been done in a systematic way, and so another attempt may be in order.
Nevertheless, everything depends on what's on the other side of the equal sign... the observed outcome. What we know about the number of currently known ETCs. Which (not counting ourselves) is currently zero.
That could change any day! And here we start with a very strong consensus that it is a good endeavor to look, to listen, to seek in the radio and optical spectra for any sign that others might dwell out there. While funding problems persist and donors fluctuate warm and cool, at least the bad old days of William Proxmire and ridicule are behind us. Still, it is hard not to feel daunted by the failure, across two generations, to find any of the long-predicted traces. Moreover, there is a growing suspicion that current methods are flawed and should be re-evaluated.
FIRST: The debate over search strategies. Put yourself in alien shoes. And let's (for now) make standard SETI assumptions — that the Others out there are at least benign, probably altruistic, not engaged in extensive colonization and interested in communicating with newcomer sapient species like us. Posit also that they are very long-lived and can take a patient attitude. Further let's suppose that such ancient ETCs have already used advanced instrumentalities to survey hundreds of thousands of solar systems in their galactic region, cataloguing those planets with oxygen atmospheres and other signs of life.
Having assumed all of that, what will be their best approach to tracking and communicating, when one of those catalogued candidate planets finally develops someone interesting to talk-to?
That could take tens or hundreds of millions of years. Omnidirectional beacons can cost a lot over such time scales. A recent economic analysis of interstellar radio propagation [10, 11, 12], demonstrates clearly why there are no such garish tutorial beacons, loudly calling out welcome to newcomers, all-day, every day, in all directions for millennia and eons. There are other ways to accomplish the same goal! Ways that would call for many orders magnitude lower capital and energy cost.
One of these alternatives is to dispatch probes across space to wait in orbit near life worlds. Initial costs are much higher than for radio messaging. But radio messages sweep onward and are lost. A physical probe (whether self-replicating or not) can wait near a world that has life but no sapience, enduring for ages until someone arises worth talking to. More about this below.
Another method is to "ping" messages at each candidate world — in sequence — once per year, or per decade, or millennium, in essence asking: "Is anyone there yet?" Cheap collimated beams can shine on each, in turn, make a routine query, then move to the next, till it is time to begin the cycle anew. Historical note: the famous "Wow Signal" — often cited as a possible SETI hit that was detected in great force, but only briefly and never again — would seem to fit this model.
Are today's SETI programs and telescopes suited to detect either of these much lower-cost alternatives? They are not. The Paul Allen Array, for example, looks at relatively narrow patches of sky, one at a time (though such patches can encompass millions of stars, if aimed at clusters or at the galactic center.) They are in effect peering through a soda straw in various directions, for very brief intervals. SETI currently searches narrowly for alien signals that aliens are supposedly sending (or leaking) broadly. But what if ET is using the equivalent of a laser pointer, aimed our way briefly, and only on occasion? Then the soda straw approach is unlikely to work.
Clearly SETI would benefit from a supplementary system that covers the Earth, searching continuously and broadly for pings that are sent by ETCs narrowly. That system would be ready to detect and pounce upon any new Wow Signals and automatically net-notify larger telescopes to zoom quickly on the source. Not a competitor with classic SETI, this second layer could serve as an ideal alert-generating system, filling a glaring deficit in the current approach.
One model for such a system might be a network of phased arrays that can electronically reconfigure to glance at thousands of patches of sky in a single hour. Just a dozen or so major arrays, well distributed and sited, could effectively sift the whole sky.
Perhaps an even better model and more economical would be Project Argus of the SETI League, which attempted to create a network of backyard, amateur radio telescopes. It is estimated that 1000 such private stations, properly tuned and interconnected, could provide enough coverage so that nearly all of the Earth's sky might be watched, nearly all the time, albeit at much lower sensitivities than the Allen Array. Imagine were some philanthropist to finance the development of a simple, turn-key kit that several thousand amateurs could easily purchase, set-up and network. This complement to the Allen Array would be inexpensive to create and could help ensure that we do not miss the pings of any curious ETC.
Inclusion of such a supplemental amateur network could also defuse and help refute suspicions that the field is now dogma-dominated by a narrow-minded group, intent on defending their cramped model and turf, maintaining instead that it is an eclectic scientific field, accepting of fresh insights and capable to adjusting to a more open world.
NEXT: The dogma of dismissing interstellar travel. We have seen that the classic SETI community reflexively downplays the possibility of interstellar flight for a number of reasons that are largely propelled by teleology. For example, in his contribution to the METI debate, Stephane Dumas  reached way back in time in order to ridicule the Daedalus and Orion projects from the 1960s. This is called "beating a strawman," as far more plausible proposals have been developed across half a century. Some that envision using antimatter and/or laser-propelled light sails are entirely based upon sound physics, imposing per year costs that would be minimally acceptable for an ambitious civilization that had industrial access to both asteroids and copious solar energy, as our own heirs may, in just two generations.
The math gets even better when you either freeze the passengers or send only autonomous artificial intelligences. And when those AI probes are tuned to be "Von Neumann Machines" — capable of making multiple copies of themselves after reaching the next star system, and dispatching those daughters ahead to new systems — then calculations show there might be one such daughter next to every star in the Milky Way within just three million years. An eyeblink in the history of the galaxy !
Indeed, that possibility of self-replicating probes has a stunning cascade of potential effects. One implication already alluded-to is that our solar system might presently have such ancient resident emissaries, perhaps concealed in the asteroid belt, at some lagrangian libration point, or sheltered under the lunar surface. There might even be several generations of probes from successive waves, sent out by ETCs motivated by curiosity, or gregarious eagerness, or for commercial purposes, or as scouts... or with an array of motives we might find chilling, inspiring, or bizarre.
In order to cover this slice of possibility space, Anthropology Professor Allen Tough in 1996 established a website called "Invitation to ETI" or IETI  based on the delightfully obvious premise that such probes might already know a great deal about us from observation at close proximity. Indeed, they would likely have already inveigled their way into our computerized networks, in order to watch and learn. Professor Tough's presumption was that such entities might only need coaxing — a clear and welcoming invitation — to reveal themselves and begin the benign process of First Contact, via web or email. Allen Tough asked me to contribute a segment to the IETI site and was surprised by the extent of my appraisal, posting thirteen sub-messages to such entities, based on their hypothetical reasons for having "lurked" — watching and reading our web while keeping silent up till now . A fun exercise in logic, that dissection of alien machine motives became a component of my recent novel about the alien probes scenario, entitled Existence .
Alas, having taken precautions to prevent spoofing by human hoaxers, Tough collected no clearly verifiable replies from alien probes, during the period leading up to his lamented passing. This negative result does not completely invalidate the Resident Probes hypothesis. Their reticence might be a matter of choice. But it did slice away some sub- variants and helped us to narrow down possibility space.
The current debate over METI or "Messaging to Extra Terrestrial Intelligence" is of fairly recent provenance. Back in the 1960s, 1970s and 1980s, the SETI pioneers Frank Drake, Phil Morrison and Carl Sagan disdained de novo attempts to attract attention Earthward, saying that advanced ETCs should "do the heavy lifting" of making contact.
Our job should be — they asserted — to keep developing better technologies for listening and understanding, while also cleaning up our act as a species with better skills at peace, justice and planetary management. All of these imperatives are still deeply believed by the "dissidents" in the SETI Community who object to METI, who include former director of the NASA SETI Program, Dr. John Billingham, former senior U.S. diplomat Michael Michaud, and this author, who have all resigned from major SETI-related committees and commissions in protest over what we deem to be the precipitate, unscientific and unprofessional manner that the original Drake-Morrison-Sagan program has lately been violated. This group was recently joined by Dr. James Benford and Dr. David Messerschmitt, both of them experts on communication via both broadcast and narrow beam radio, plus others who share our concern about premature METI. Our reasons will be summarized below.
The "no outward messages" admonition always included reasonable exceptions. For example, one harmless and inspiring stunt was the Arecibo Message of 1974. Taking what they had learned from creating the famous the Pioneer plaque, Frank Drake and Carl Sagan aimed a radio burst at the M13 star cluster. It consisted of 1679 digits that formed a pong-like picture of us and our planet. But this exception — as well as the earlier (1962) Soviet Morse Code Message sent to Venus — had been deliberately designed not to be detectable with any plausibility by actual aliens! (One was aimed at a planet known to have no life and the other target was vastly far away.) Both were meant to inspire discussion here at home. And they succeeded.
During the 1980s and early nineties, a sober effort was made to develop documents that could serve as guidelines for a First Contact event. This led to the First and Second SETI Protocols, which set down:
what principles should guide astronomers and other participants amid the hectic period during and following an actual SETI "hit."
whether, how and when to transmit de novo messages — wholly of our own volition — far more obtrusive than the Arecibo signal.
I served along with chairman Michael Michaud, John Billingham and others on the loose committee that drafted these documents. And while they were never formally accepted by international or national agencies as having any sort of legal force, the First Protocol (concerning behavior in the event of a verified SETI detection) did get various degrees of informal blessing and has been adopted as a guideline by most of the scholarly communities that turn big radio telescopes skyward. It is widely accepted as having the considerable effect of a consensus agreement on best practices.
For a primer-background about the First and Second SETI Protocols, see: "A Decision Process for Examining the Possibility of Sending Communications to Extraterrestrial Civilizations" [17, 18].
The First Protocol contains an injunction against anyone peremptorily responding to a discovered alien signal, before appropriate international consultations have taken place. And, while that loose term is left undefined, any sensible adult would recognize what the clause means. That no one should impudently arrogate a right to speak for all of humanity before there has been a serious attempt to gather as many of humanity's brightest intellects as practical, from a wide range of relevant disciplines — plus sages and statesmen from outside science — to hold a very public conversation about what to do next.
A conversation whose lively periphery might engage — via the internet — more than half of the planet's human population. More will be said about the matter of "consultations" below. But retain the image you just pictured in your mind — of an open and illuminating and fun intellectual extravaganza — for comparison against the caricature of "consultations" offered in the debate by Dr. Seth Shostak.
One must feel sympathy for SETI-ists. They have devoted lifetimes to a project that always bore the brunt of both ridicule from one side and fervent fandom from the other. Today, the ridicule that torpedoed NASA's brief venture in SETI — headed by my fellow dissident Dr. John Billingham — has lessened considerably, while the fandom aspect has expanded prodigiously to include frequent allusions and references in Hollywood films. And yet, SETI is forever plagued by financial problems, depending upon unpredictable spates of largesse from donors such as billionaire Paul Allen, or upon infrastructural support from hard-pressed universities.
Even as new, SETI-specific telescopes and sophisticated signal processing systems come on line, there is another pressure — the beating of time. Each better instrumentality sifts the cosmic haystack for the proverbial needle ten or a hundred times better than the ones that came before it. Great! But the refrain: "any day now" starts to ring hollow and the ongoing silence grows frustrating, even daunting.
Under those conditions, is it understandable that a temptation would grow, to poke at the experiment? If ET is keeping quiet, then should we be the ones to speak up? To shout into the cosmos? To cry "Yoohoo!" and provoke the conversation into being? We dissidents have been careful to parse our complaint over this new, untidy, and presumptuously tendentious endeavor. Though we start by appraising a scientific sin — poking-at-the-experiment.
There is, for starters, the core community that clusters around the SETI Institute in Silicon Valley, California. Both Dr. Jill Tarter and Dr. Seth Shostak deny having any intention of using their facilities to beam messages skyward. (It would violate agreements with their donors, for one thing.) On the other hand, they have grown ever-more vigorous in running interference for and enabling others around the world — such as Russian radio astronomer Dr. Alexander Zaitsev — whose METI efforts at the big Evpatoria dish in Crimea have several times attempted to burst open the shell of mundane static surrounding the Earth .
One common complaint about METI is that: "if everyone else out there is being quiet, maybe it's because they know something we don't know." The notion that we should make assumptions about a benign cosmos and start hollering, when others who are presumably older, wiser and vastly more powerful are evidently refraining... this would seem preposterous and at least face a steep burden of proof.
Alexander Zaitsev has crafted a response to this assertion, one that — while perhaps weird — certainly has the virtue of originality. He has stated explicitly that any nearby ETCs are perforce — by reason of their silence — cowards who must be coaxed into opening up. Zaitsev even suggests a new Drake Equation factor f(m) for the low fraction of technological species who have a "clear and non-paranoid consciousness sufficiently courageous to engage in deliberate interstellar transmissions," and thus he concludes that we, as the new (and presumably courageous) kids on the block, are behooved to do the coaxing .
Ironic juxtapositions abound. During the USSR era, Soviet dogma insisted that any advanced ETC would automatically be both altruistic and socialist. Since then, Russian and many European SETI-ists have dropped the "socialist" portion, while retaining belief in automatic harmlessness on the part of any advanced race. While reconciling altruistic with cowardly and paranoid may seem awkward to some, it appears to have been no problem for Zaitsev. Indeed, let me avow that it is conceivable that we, as the descendants of gregarious-omnivorous apes, might indeed possess some traits of personality that make us inherently more outgoing than average. Than (say) the heirs of sapient herbivores or carnivores. It certainly merits inclusion on the growing list of "Fermi" hypotheses! Though not in the top, most-plausible tier. Certainly, this startling notion qualifies as no more than assertion, one of many to be examined by sages who are much more knowledgeable about such things than either Zaitsev or me. As a fact-free assertion, it does not qualify as a reason to gamble the lives of all of our descendants without prior consultation.
This whole topic of altruism, its roots in biology and likely prevalence in the cosmos is discussed elsewhere [21, 22]. Indeed, it is one of many topics that should be given scrutiny in appropriate international conclaves.
This is not the place for a complete "j'accuse" indictment against METI and its fellow travelers. We dissidents have laid out our case of objections elsewhere. My own public protest, perhaps the most colorful , followed years in which — successively — each of us grew frustrated and felt compelled to resign from varied SETI or SETI-related committees. That part of the story is best told by Michael Michaud and John Billingham, whose exile from the community was a great loss and unambiguously cause to fret about the direction chosen by the core SETI-ists.
To show how eclectic and diverse and productive the discussion had been, until ruptured around the turn of the century, let me quote from Billingham : "The issues involved in sending messages to extraterrestrial civilizations raise profound philosophical and political questions. These questions are of such weight for the future of our own civilization that they merit extensive discussion in the years to come."
Such discussions have begun. Michaud has asked "If Contact Occurs, Who Speaks for Earth?" Michaud has also published a seminal paper on "Ten Decisions that could Shake the World" . Billingham has constructed decision trees that involve both scientific and societal questions and answers. Doug Vakoch has published extensively on the content of messages that might be transmitted. In his "Dialogic Model", he has also argued for the representation of diversity in messages to extraterrestrials . Alas, the conversation has been rather one-sided.
Our complaint began coalescing when what had been a collegial discussion started falling apart. When deliberations and decisions regarding what should be a scientific field — the appraisal and search for extrasolar intelligent life — were increasingly treated as the semi-private domain of a very small group of radio astronomers and their surrounding coterie of fans. Moreover, at a series of gatherings that had the appearance of being carefully "potemkin" stage-managed, drastic alterations of earlier consensus agreements were rubber-stamped, with the blatant goal of removing all obstacles from the path of those pursuing METI.
For example, the Second SETI Protocol, widely circulated and accepted by consensus during the 1980s and early 1990s, had simply reiterated the language of the First Protocol, in ways that were completely un-controversial when it was first drafted. Only, where the first protocol called for significant international consultations before responding to a detected signal, the Second suggested such consultations should take place before beaming de novo "messages" into the Cosmos on behalf of all humanity. If consultations seem a good idea in the one case, why not the other? But the upshot of the offending meetings was to rewrite and eviscerate the Second Protocol, eliminating even any fig-leaf or moral suasion for METI zealots to consult with humanity before shouting on our behalf.
As it appears to be my role here to state things bluntly, I'll be frank. It appears to us that the psychology behind this shift is frustration. It happens to all scientists, now and then, when the experiment obstinately refuses to comply with expected results. With deeply, fondly, passionately yearned-for results. The temptation to meddle, to poke, to prod and holler is understandable, even if giving in to it is unforgivable. Especially in the manner that it has taken place in SETI.
As citizens of an emerging worldwide, technological civilization, we have begun coming to terms with a valuable new branch of science called Risk Analysis. While our power as a species increases, we keep uncovering ways that both nature and our own actions might bring grief, death, destruction upon the nations, homes and hopes that we depend upon. The history of our planet is riddled with extinctions and we can now see that Carl Sagan was right — that a new and rash sapient race is capable of meting out disaster upon itself or the planet that nurtured it. This dreadful realization of our power should not daunt us from moving forward! But it behooves us to study the methods of foresight, anticipation, and maturity, weighing plausible risks and ranking them along a scale that takes into account both their estimated probabilities and the potential severity of their outcomes. Rational consultation, argument and precaution do not preclude all action! But there is a mature way to do things.
It is easy to see how this relates. To be clear, the First and Second Protocols were great successes. They had the power and influence of consensus-accepted practice, even without the slightest coercive authority. Had the Second Protocol not been altered, we might have been able to bring it to Russian and Crimean authorities, who would have then asked Alexander Zaitsev to justify his attention-grabbing events that parted so dramatically from world consensus practice. Mindful of public opinion, those facilities owners would have at least asked him what he had against talking to some big, eclectic international meetings, before using their taxpayer financed radio telescope to shout messages skyward.
Without question, responsibility for abandoning the wisdom of the original Second Protocol falls upon the shoulders of those who gutted it, and who now disparage even the very notion of eclectic international consultations — meetings of world sages to discuss how and when we Earthlings should shout into the cosmos.
The tussle over METI has many levels, from superficial to psychological to philosophical to legal.
FIRST: Among the rationalizations we frequently hear is the Barn Door excuse — that the "horses are already out of the barn," or the "cat is already out of the bag." That the Earth is already detectable, both as a living world by its atmospheric composition and as the abode of intelligence from our radio leakage into space. Therefore, if any aliens wished to do us harm, they would already be on their way and no further danger can arise from deliberate messaging.
This reasoning — though flawed in several ways — begins with a truth. Clearly, ETCs with advanced telescopes will be able to see, even at fairly large distances, that Earth is a living world with an atmosphere far out of equilibrium, maintained that way by life. It has been this way for more than a billion years with an oxygen rich blanket. This reduces to near zero the likelihood of one "fermi" scenario — the classic destroy-all-life berserker probe. Moreover, it suggests that alien civs out to a great distance might have marked our solar system on a long list sites meriting "ongoing interest." This might entail routine re-examination (as discussed earlier), even if our system offered no signs of tech society for eon after eon.
But the rest of the Barn Door Argument is specious on many levels. The SETI Institute's own Dr. Seth Shostak himself has calculated that the TV and radar flowing across Earth during its noisiest decade — the 1980s — would not be detectable above background very far into space, unless truly fantastic alien antennas were aimed exactly at us for relentlessly dedicated staring. The accompanying paper by Billingham and Benford  shows that truly substantial resources — even for an advanced ETC — would have to gaze fixedly at us even to detect brief flashes from the rare, laser-like planetary radar sweeps that have on occasion flashed from Earth.
But the most searing refutation is logical. If we're already detected, then why are you striving so hard to shout into the cosmos and attract attention? Michael Michaud put it succinctly: "The advocates of Active SETI want their efforts to have consequences." They intend to seek consequences — without prior consultation — and even make strenuous efforts to avoid interference from those wanting consultation. They intend to alter whatever our current equilibrium situation happens to be viz a vis the Galaxy at large. Claiming that this does not matter, because the alteration that they blatantly seek has already happened? Because the horses have already left the barn? That is illogical and hypocritical.
SECOND: No bad outcome from METI is physically possible. That is another of the standard nostrums given in order to dismiss the concerns of those seeking consultations before METI. Note that, in dismissing even the possibility of interstellar travel, this community is keeping fealty with one of its most venerable tenets. Not only do ETCs remain fixed in number and pinned in the home systems where they evolved, they cannot dispatch messengers, either benign or malign.
Putting aside the psychological and traditional roots of this position, it is certainly a tenable one to put on the table of argument! Possible ways to cheat around Einstein's speed limit are highly speculative, even coming from brilliant fellows like Hawking or Thorne. And if we push such unlikely speculations aside, obeying the speed limit of light (with ship speeds likely below 0.2c) then most "Independence Day" style, garish Hollywood versions of interstellar aggression sink to very low probability. Despite assertions to the contrary, none of the main SETI Dissenters has ever raised the serious likelihood of alien invasion.
Still, some means of interstellar harm-doing are clearly compatible with physical law. An ETC can build a simple antimatter rocket and propel it accurately at 0.1c to intersect with a faraway planet, wreaking horrible damage when paths intersect. We do not claim this to be likely. It merely suffices to refute the notion that long-reach harm is impossible.
Nor is even that necessary. An alien probe, resident in our solar system, might be commanded to steer asteroids toward Earth. Or else to meddle in our computer networks or in our political affairs. The list of unlikely but physically quite possible scenarios is very long, many of them already explored in cogent, higher-end science fiction tales, a great library of thought experiments that SETI-ists seem willfully bent on ignoring.
The mere existence of so many hypothetical dooms and threats does not, by itself, preclude anything. A prudent and carefully-discussed cataloguing of such possibilities — under paradigms of Risk Analysis — might very well lead adults to conclude that the summed danger falls below some acceptable threshold, allowing measured and accountable exercises in METI or Active SETI to proceed. We do not deny that possibility!
But it is quite another thing to evade such a discussion and appraisal. It should have begun long ago, instead of commencing with this particular session (the 2011 debate at the Royal Academy).
THIRD: Muzzling the Earth? Some METI supporters interpret our call for substantial, eclectic, broadly inclusive prior consultations before METI as an effort to muzzle our planet forever. Dr. Seth Shostak has asserted that such consultations can only have one outcome, permanent repression of free enquiry in an important field of science: "Even if the odds of a devastating reaction are long, those consequences could be lethal, and therefore there is no acceptable level of risk." Whereupon he concludes that any such extended discussion would inherently be disposed to extend a METI moratorium forever.
This strikes home in personal ways. My own nonfiction exploration of transparency, openness and accountability — The Transparent Society: Will Technology Make Us Choose Between Privacy and Freedom? — won the Freedom of Speech Award of the American Library Association and is among the leading public policy books promoting open discourse as a fundamental element of our social and technological compact. I note this only to show that I am deeply aware of the scenario that Dr. Shostak has raised. Indeed, it is widely discussed in the rapidly developing field of Risk Analysis.
To be clear, the kind of scientific rigor mortis that he describes — renunciation of forward progress because of hyper-prudence — is certainly a danger that must be both considered and countered, if we are to move forward. (It is also major topic in Existence.) Many fields other than SETI have already begun adapting ways to meet this challenge, blending reasonable caution and responsibility with determination not to let science be imprisoned by fear.
Michael Michaud refers to the archetype example of successfully negotiating this dilemma — the Asilomar Process by which the community of genetic biologists met, discussed, assayed dangers and came up with a list of reasonable, consensus-compromise measures to both minimize risk and maximize effective research. We have referred to the Asilomar Process repeatedly, in discussions with Seth Shostak and in public, hoping that the core SETI-ists would perceive that as our proposed model, especially since details of the consultation are up for adult negotiation, and they would have a role it its design.
In any event, as we will see in followup discussions, any moratorium could not be permanent or "muzzle" the Earth. Not unless a worldwide Orwellian tyranny took fierce hold. (That is, indeed, one possible "fermi" explanation for why other races might be silent.) Here on Earth, given the rapid advances of technology and a rambunctiously individualistic civilization, the capability to transmit laser-like signals that might be detectable across many light years will be in private hands, within a decade or two. Permanent "muzzling" was never proposed and is quite infeasible. Nevertheless, a world discussion before that day arrives can have only positive effects.
Our general proposal has been to start with an eclectic meeting attached to one of the major pan-science conferences, such as the annual convention of the American Association for the Advancement of Science, a mis-named event that now constitutes the greatest gathering of diverse disciplines, drawing eminent minds from around the world. Since they will 'already be in town anyway,' it should be possible to draw great thinkers from not just radio astronomy, but exobiology, genetics, animal behavior, anthropology, psychology, physics, ethics and experts on the history of first contacts among human civilizations in our past. Insights might be drawn from what happens when biomes encounter each other for the first time, such as when the rising Isthmus of Panama suddenly brought North American placental mammals into contact with marsupials from the south.
For the first time — and in public to edify folks around the world — the supposed tradeoffs could be discussed by Big Thinkers whose areas of expertise compliment each other, and span the vast array of topics that contribute to SETI. Always, one of the great attractions of the SETI field has been the way that it encompasses all fields of human curiosity and knowledge covered by the expanded Drake Equation. from physics all the way to art and questions of the soul. Indeed, the diverse sages will doubtless question blithe assumptions that both the SETI-ists and we dissidents take for granted. Of course, even a three hour symposium at the AAAS — or some other eminent gathering — would only be the beginning. It is our impression that this event would lead to others, in a world conversation that builds excitement and growing momentum. The kind of publicity that would do SETI itself — the scientific search — no harm at all.
FOURTH: What a difference a decade can make. A little over a dozen years ago, we humans knew of no planets outside our solar system. Now, the number of confirmed extrasolar planetary discoveries numbers in the hundreds and unconfirmed possibles are listed in thousands. Every year, we grow more knowledgeable about the core processes of life, of evolution, of intelligence, of the quandaries of planetary management, and every other factor in the expanded Drake Equation, including the plausibility of interstellar travel, as exemplified by DARPA's One Hundred Year Starship program.
Above all, each generation of new, rapidly improving SETI tools will let us better sift that cosmic haystack for bright needles, learning vastly more about the neighborhood and possibly making that wondrous find. Or else teaching us more about the daunting but mentally transfixing silence out there. And either result will prove enlightening.
We dissidents avidly support that progress! Moreover, we have faith that the experiment can and should continue as first envisioned by Carl Sagan and Frank Drake and other SETI pioneers. Looking, listening, seeking. And not meddling or interfering in the experiment, hoping vainly to force a result. Indeed, it seems very likely that just another dozen years from now, we will know vastly more about the situation in our corner of the galaxy than we do now. At the end of any such moratorium, we will be a wiser species, better able to calculate our best path forward. Especially if, by then, we have held a vast and open conversation.
We are the youngest of all technological races in the cosmos, like an orphan child who suddenly finds herself wandering a strange jungle that's quiet... too quiet. So quiet that the simplest, parsimonious explanations appear rather daunting. Almost as if the creatures and natives know something that we don't know, and are keeping silent for a reason.
Or else, something is keeping the number of creatures and natives low... too low. If you found yourself in such a situation, would you listen a while? Maybe talk things over with your fellow orphans? Especially when you are already learning at a rapid pace, and may have more of the clues you need soon, with a little more listening? And patience?
Perhaps you have the kind of personality that says: "What the heck! I might as well shout and see what happens!"
That's all very well if the only one you are putting at risk is yourself. But when that risk is also imposed upon our children — all of humanity and our planet — is it too much to ask that we discuss it first? Think of it as an interstellar test of both IQ and common courtesy. A way to show that we're the kind of responsible grownups who might actually be ready for First Contact with other adult minds.
Professor Steven Dick's Life on Other Worlds: The 20th-Century Extraterrestrial Life Debate (Cambridge University Press 2001) covers much of the history of these concepts during the latest human lifetime. For a tour of the concepts going back in time, see M.J. Crowe's The Extraterrestrial Life Debate, 1750-1900: The Idea of a Plurality of Worlds from Kant to Lowell (Cambridge University Press 1986). Another book that covers the general field is Contact With Alien Civilizations (Copernicus Books, 2007), by former senior U.S. diplomat Michael Michaud.
Extraterrestrial Civilization, edited by Thomas B.H. Kuiper and David Brin, (American Association of Physics Teachers, 1989) is a reprint book that offers some of the classic papers in the field ranging from SETI enthusiasts like Sagan, Drake Cocconi and Morrison to early uniqueness proponents (e.g. Hart) and appraisals of interstellar travel and migration by Forward, Finney and Jones and by Oliver.
Online resources include:
A compilation of SETI/METI quotations collected by Michael Michaud.
Genevieve Valentine, You Never Get a Seventh Chance to Make a First Impression: An Awkward History of Our Space Transmissions, Lightspeed Magazine, March 2011.
Here are a couple of recent papers of real significance to the field:
Jonathan Starling and Duncan Forgan, "Virulence as a Model for Interplanetary and Interstellar Colonisation" suggests that the spread of ETCs through the galaxy might be modeled by mathematical methods developed to appraise "virulence" of infectious parasitical organisms — an unpleasant comparison that eerily replicates my logic in EXISTENCE.
Another recent paper, "Kardashev Type III Civilizations Could Be Rare," goes straight to the extremum of seeking observable evidence that advanced (or super-advanced) ETCs have ever appeared in the universe, at all, by investigating whether there are any "Kardashev type three" civilizations emitting telltale infrared dignatures in other galaxies.
 Brin, G.D., "The Great Silence — the Controversy Concerning Extraterrestrial Intelligent Life", Quarterly Journal of Royal Astronomical Society, Fall 1983, v.24, pp 283-309.
 Wesson, Paul, "Cosmology, extraterrestrial intelligence, and a resolution of the Fermi-Hart paradox", Royal Astronomical Society, Quarterly Journal 31: 161-170, 1990.
 Hart, M., "An Explanation for the Absence of Extraterrestrials on Earth", Royal Astronomical Society, Quarterly Journal, 16: 128-135, 1975.
 Finney, B.R. and Jones, E.M., Fermi's Questions, University of California Press, 1985.
 Kuiper, T. & Brin, G.D., Extraterrestrial Civilization, American Association of Physics Teachers, 1989.
 Hanson, R., "The Great Filter, Are We Almost Past It?", 1998.
 Ward, P. & Brownlee, D., Rare Earth: Why Complex Life is Uncommon in the Universe, Springer, 2003.
 Oliver, B.M., "Review of Interstellar Rocketry Fundamentals", JBIS 43, pp. 259- 264, 1990
 Forward, R., "Feasibility of Interstellar Travel: A Review", JBIS 39, pp. 379-384 1986.
 Benford, G., Benford J. & Benford D., "Searching for Cost Optimized Interstellar Beacon", Astrobiology, 10 4, 490-498, 2010.
 Benford, J., Benford G. & Benford D., "Messaging with Cost Optimized Interstellar Beacons", Astrobiology, 10 4, 475-490, 2010.
 Benford, J., Benford G. & Benford D., "Building And Searching For Cost-Optimized Interstellar Beacons", Communication with Extraterrestrial Intelligence, Ch. 18, ed. Douglas A. Vakoch, SUNY Univ. Press, NY, pg. 279-306, 2011.
 Dumas, S., "The Fear of Contact", Journal of the British Interplanetary Soc. Vol 67, No 01, January 2014.
 Tough, Allen, "Invitation to ETI", 1996.
 Brin, G.D., "An Open Letter to Alien Lurkers", 1996.
 Brin, G. D., Existence, Tor Books 2012.
 Billingham, J., "A Decision Process for Examining the Possibility of Sending Communications to Extraterrestrial Civilizations", 1996.
 Brin, G.D., "SETI: A collection of introductions", 2004.
 Zaitsev, A., "Sending and Searching for Interstellar Messages", Acta Astronautica 63, 614-617, 2007.
 Zaitsev, A., "The Drake Equation: Adding a METI Factor", SETI League website, 2005.
 Brin, G.D., "A Contrarian Perspective on Altruism: The Dangers of First Contact", Searching for Extraterrestrial Intelligence, Paul Shuch ed., pp 429-449 2011.
 Oakley, B. Pathological Altruism, Oxford University Press, USA, 2012.
 Brin, G.D., "Shouting at the Cosmos", Lifeboat Foundation website, 2006.
 Michaud M.,"Ten Decisions that Could Shake the World", Space Policy 19, pp.131-136, 2003.
 Vakoch, D., "The dialogic model: representing human diversity in messages to extraterrestrials", Acta Astronautica, 42 10, pp. 705-710, 1998.
 Billingham, J. and Benford, J., "Costs And Difficulties of Interstellar 'Messaging' and the Need For International Debate on Potential Risks", Journal of the British Interplanetary Soc. Vol 67, No 01, January 2014.
Copyright © 2010 by David Brin. All rights reserved.
Where is everybody? And why can't we find them? Persistent null results from the Search for Extra-terrestrial Intelligence do not invalidate continuing the search, but they do raise questions about long-held assumptions over how we search.
"The Search For Extra-Terrestrial Intelligence: Should We Message ET? (published in full here) was first prepared for a debate at the Royal Society (2010), then published in the Journal of the British Interplanetary Soc. Vol 67, No 01 (January 2014). The formal version is available from JBIS at: http://www.jbis.org.uk/paper.php?p=2014.67.8.
David Brin, Existence (book)
David Brin, "SETI: A collection of introductions" (Scoop.It! compilation)
David Brin, "Shouting At the Cosmos"
David Brin, "Xenology: The Science of Asking Who's Out There"
Donald Brownlee and Peter D. Ward, Rare Earth: Why Complex Life is Uncommon in the Universe (book)
Michael J. Crowe, The Extraterrestrial Life Debate, 1750-1900 (book)
Steven J. Dick, Life on Other Worlds: The 20th-Century Extraterrestrial Life Debate (book)
S. Dumas, "The Fear of Contact"
Robin Hanson, "The Great Filter, Are We Almost Past It?"
International Academy of Astronautics (SETI Permanent Committee), complete SETI Protocols list
International Academy of Astronautics (SETI Permanent Committee), First SETI Protocol: "Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence," adopted by the International Academy of Astronautics, 1989
International Academy of Astronautics (SETI Permanent Committee), Second SETI Protocol: "A Decision Process for Examining the Possibility of Sending Communications to Extraterrestrial Civilizations" (pdf)
Invitation to ETI (Professor Allen Tough's website)
Thomas Kuiper and David Brin, eds., Extraterrestrial Civilization (book)
Franck Marchis, "Kardashev Type III Civilizations Could Be Rare"
Michael Michaud, "'Active SETI' Is Not Scientific Research"
Michael Michaud, Contact with Alien Civilizations (book)
Barbara Oakley et al, eds., Pathological Altruism (book)
H. Paul Shuch, "A Contrarian Perspective on Altruism: The Dangers of First Contact"
Jonathan Starling and Duncan Forgan, "Virulence as a Model for Interplanetary and Interstellar Colonisation"
Genevieve Valentine, "You Never Get a Seventh Chance to Make a First Impression"
Dr. Alexander Zaitsev, "The Drake Equation: Adding a METI Factor"
David Brin, "An Open Letter to Alien Lurkers"
David Brin, "Those Eyes"
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