≡ Menu

Alien Civilisations: Two Competing Models

by Stephen Ashworth

Being a jazz buff (the 1950s and early 1960s are my era of choice) I naturally note that frequent Centauri Dreams commenter and contributor Stephen Ashworth is a tenor sax man who regularly plays in venues near and around Oxford in the UK. Stephen is also, of course, an insightful writer on matters touching our future in space, not only through his work in the Journal of the British Interplanetary Society but also in his Astronautical Evolution site, which bills itself as studying “The social and political basis for the optimistic, progressive, astronautical society of the present and future.” In this essay, Stephen looks at ways of viewing extraterrestrial intelligence that pose different models for the emergence and spread of life in the universe. NOTE: If you’d like to comment, be aware that today is a travel day for me, so comment moderation will be sporadic, but I’ll catch things up tonight.


Speculations about the existence of extraterrestrial civilisations analogous to our own fall naturally into two broad camps, which we may for convenience describe as the Steady State model versus the Big Bang model (not to be confused with the cosmological theories of the same names). There is also a Hybrid model which combines the two in true Hegelian fashion (thesis → antithesis → synthesis).

The Steady State model

This is the basis of the famous Drake equation. Drake assumed that for a long time in the past, and for a long time to come, civilisations have been and will continue to be coming into existence, persisting for a while and then vanishing again. The question which interested him was whether the rate of appearance of civilisations capable of interstellar radio communication, and their average longevity, were large enough to make it statistically likely that we would be able to establish contact with a nearby alien society before either they or we became extinct.

Drake regarded civilisations as entirely sedentary or static phenomena. Thus the locations at which they might be found today are always the same as those at which they originally evolved from their biological forebears, and thus closely resemble our planet Earth. They must be found orbiting closely Sun-like stars in circular orbits, thus in the so-called “habitable zone” (planets outside the zone where surface liquid water is possible presumably being habitable only by creatures who were not capable of radio astronomy, or of changing the atmospheric chemistry if there was no atmosphere, and therefore undetectable by astronomical means).


Diagram 1: The Steady State model.

Diagram 1 shows schematically how many civilisations exist at any one time in the Galaxy on the Steady State model. For simplicity it is assumed that each star has either one civilisation, or none. The total number of stars continues to increase slowly as long-lived dwarf stars are added to the population. The number of civilisations rises slightly faster, as longer-lived planets come into play. We are now at point A on the time axis.

The number of stars occupied at any one time is a small fraction of the total (the diagram exaggerates the fraction for clarity). For example, if we share the Galaxy with a million other civilisations at the present time, as optimists may hope, then only 0.00001 of the stars are currently occupied.

All such civilisations arise independently of one another. Collapsed civilisations are not replaced on their planet of origin, but are replaced by other civilisations arising elsewhere. Civilisations are randomly scattered throughout the Galaxy, though Gonzalez, Brownlee and Ward have presented arguments as to why the centre and the outlying galactic regions may be less hospitable than a ring partway out from the centre, where indeed our own Solar System is found.

Civilisations remain completely dependent upon their planet of origin, and the distance between nearest-neighbour planets of that type (perhaps tens of light-years) forbids interstellar settlement.

The Big Bang model

In his book Contact with Alien Civilisations, Michael Michaud reviews the ideas of a number of people who have gone beyond the Drake equation by taking account of the possibility of interstellar colonisation, including Freeman Dyson and Seth Shostak. A similar view has been taken by Ian Crawford, whose article in Scientific American a few years ago discussed the prospect of a dynamic civilisation colonising the entire Galaxy by star-hopping.

Using technologies readily conceivable today (such as nuclear fusion rocket propulsion), a wave of colonies from an expanding civilisation in our Galaxy might take 1,000 years to make each 5 light-year jump (say, travelling for 500 years at 1% of light speed, then taking another 500 years to build up sufficient infrastructure at the target system to make the next jump). Since the Galaxy is about 100,000 light-years across, such a civilisation could spread daughter civilisations to every suitable star and planetary system in the Galaxy within 20 million years.

This, however, is only 0.2% of the age of the Galaxy. The introduction of faster ship speeds makes absolutely no difference: even without warp drive or FTL travel, on a cosmological timescale such a transition from civilisation nowhere to civilisation everywhere is, as Crawford demonstrated, essentially instantaneous.

For a long time, then, the Galaxy is completely devoid of intelligent life. But then one civilisation appears, and spreads throughout the Galaxy in a burst of expansion which we are calling the Big Bang. Thereafter, the locations at which intelligent, technological life is found are almost all colonies, and that life is ubiquitous and permanent.


Diagram 2: the Big Bang model.

Diagram 2 shows schematically how many civilisations exist at any one time in the Galaxy on the Big Bang model. If humanity is alone, then we are at point A. But there is a possibility (though a small one) that another civilisation in our Galaxy is, say, only a million years more advanced than we are, and has not yet colonised our part of the Galaxy, in which case we are at point B.

In contrast with the Steady State model, in which stars are occupied randomly, galactic real estate is occupied by colonies in an expanding bubble of space centered on the first civilisation’s planet of origin. Two or more such expanding bubbles may appear, but only if two or more independent civilisations make the breakthrough to space colonisation within about 20 million years of one another – unlikely to occur within any one galaxy. Once the Big Bang is complete the number of stars occupied at any one time is a large fraction of the total, including virtually all main-sequence stars, thus certainly over 0.9 of the total.

Collapsed civilisations are likely to be recolonised from other colonies. In fact, it is possible for every single civilisation to collapse (just as every individual in a population dies), but so long as each civilisation despatches on average more than one colony during its lifetime, the galactic population of civilisations continues to grow.

The original civilisation quickly leaves its planet of origin and adopts a new, space-colony mode of living which allows its offshoots to prosper at all stable stars with orbiting planetary or asteroidal material. This both reduces the distances of interstellar journeys for such a species, and pre-adapts them to living conditions on multi-generational voyages. But all civilisations which evolve after the Big Bang (unless they appear almost simultaneously with it, around point B on the diagram) grow up in an environment dominated by their local colony of the original civilisation.

Their access to space transport would presumably be analogous to the access which a non-developed tribal people on present-day Earth may or may not have to the developed world’s existing motor, rail, shipping and air networks.

The Hybrid model

It is possible to combine these two contrasting models in a single Hybrid model if some emerging technological civilisations get as far as radio astronomy but do not achieve interplanetary and hence interstellar space colonisation.


Diagram 3: the Hybrid model.

Diagram 3 shows schematically how many civilisations exist at any one time in the Galaxy on the Hybrid model. If our own civilisation collapses before we establish viable extraterrestrial colonies, then we are at point A; if we do succeed in spreading into space, then we are at point B.

In either case, we are unlikely to find interstellar conversation partners. The level of development at which we have radio astronomy but not space colonisation is not in itself a long-term sustainable level, I would argue, but rather an unstable intermediate stage. Having got as far as radio astronomy, a civilisation will either complete the transition to a space-based civilisation within a few centuries, or completely collapse.

This means that the longevity of a society which tried to stabilise itself at that level would be very small, certainly less than 1000 years; the number of such civilisations present at any one time would be correspondingly small; and the distance over which any messages would have to be exchanged correspondingly large, making successful communication correspondingly unlikely.

(If there were as many as 1000 civilisations at any one time, i.e. N = L in Drake’s equation after all the other factors have roughly cancelled each other out, and 1011 stars in the Galaxy, then for an average interstellar spacing of 5 light-years the average spacing between active civilisations would be 2000 light-years, and the waiting time between sending a question and receiving a reply would be greater than the lifetimes of both the transmitting and receiving civilisations.)

The question of longevity

Given modern fears about nuclear war, peak oil, environmental degradation, social degeneration, technological disaster, climate change and terrorism, spiced with a strong dose of post-colonial guilt and self-loathing, for many people it goes against the grain to think of an industrial civilisation like ours as something which might become a permanent feature of the universe.

What is the lesson from the past evolution of life? Firstly, it must be acknowledged that industrial mankind is as different from our pre-industrial forebears as they were from single-celled Precambrian organisms. Unless one is to maintain that science and technology are somehow unnatural, an aberration from the God-given natural order, then the facts must be acknowledged: a new type of life has emerged with capabilities never before seen. They include the abilities to access other heavenly bodies, and to digest the raw materials found there, neither of which was possible before, except in the marginal case of small numbers of bacteria being randomly exchanged between Earth and Mars.

The pattern from evolution is that each level of biology has given rise to a higher level founded on it: thus prokaryotic cells produced eukaryotic cells produced multicellular life produced technological life – in my own terminology: microbiota → gaiabiota → technobiota.

As each new level of complexity appears, the previous level also persists in symbiosis with it. Furthermore, whereas even bacterial life could not originally have hoped to outlive the death of the Earth (and of Mars) when the Sun approaches its red giant phase, providing that our civilisation fulfils its potential then those less complex organisms will, along with ourselves, continue to live and prosper long after the death of the Sun.

The pattern therefore suggests not only that our technological civilisation will produce some kind of successor at a higher level of complexity, but also that it will not die out once it has become properly established.

Clearly our society is still going through a period of rapid transition, and cannot possibly be regarded as well established yet. It is still experiencing technological and social revolutions, it has not yet reached its final form, and it is still a monoculture. Only once it has technologically matured and begun to diversify at a variety of different Solar System locations, and even more so at a variety of nearby stars, will it be possible to say that civilisation has finally arrived.

Once it has arrived in full flower, the more dynamic branches of it will certainly spread, because regardless of the precise impulse at work that is what life has always done.

Consider the question: where can one find bacteria on Earth? The answer is: nowhere, for an unknown period of time early in Earth’s history. Then there is a Big Bang, a relatively brief explosion of bacterial life, and thereafter the answer is: everywhere.

Our industrial society has yet to experience the equivalent of that Big Bacterial Bang, or of the Cambrian explosion of 550 million years ago when a plethora of new and diverse multicellular forms emerged and went their own ways. That will require our descendants to expand on an interplanetary and ultimately an interstellar scale. But when they do, or when some other civilisation does if we don’t make it, and if life develops in the future as it has in the past, then civilisation will certainly become a ubiquitous and universal feature of the Galaxy for as far into the future as it is possible for us to glimpse.

Answering Fermi’s question

I discussed this at length on the I4IS blog last December.

In brief: the question is why civilisation did not arrive before now, with a starting point elsewhere than on Earth, given that the stelliferous universe with earthlike planets is about three times older than the Solar System.

The reason why people have such a problem with this, and refer to it as a paradox, is because they are wedded to the traditional view since Darwin that life evolved from chemistry on Earth, whether in a “warm little pond”, a piece of damp clay or a hydrothermal vent. If that was the case, then since it evolved within about 300 million years after the end of the late heavy bombardment, it should have done so on many other planets, and billions of years earlier.

But Robert Zubrin makes the point that there is a huge complexity gap between the simplest bacterium known to science and the most complex molecule that can be synthesised by shaking up raw materials in a test-tube. Some proto-bacterial form of life must have preceded life as we know it. But there is no evidence of proto-bacterial life on Earth.

This to my mind is strong evidence that, contrary to the generally accepted view, life does not evolve from non-life on Earth-like planets. The obvious alternative scenario involves it first emerging in a microgravity environment in something like a comet nucleus, and doing so only extremely rarely. This decouples its initial emergence from its subsequent evolution to multicellular forms, allows a period perhaps 100 times longer for that initial jump in complexity to occur, explains why proto-bacteria have never been found on Earth, and furthermore adds in the requirement for a low-probability space transfer before evolution towards multi-cellular forms can begin, pushing the Big Bang of technobiotic life to the right on the diagram.

But not too far to the right. For all that the accepted age of the universe of 13.7 billion years seems to us to be unimaginably ancient, on its own terms the universe is still young. Judged by the lifetimes of its longest-lived stars, the red dwarfs, the universe will continue to contain stars and planets as we know them for a period on the order of tens of trillions of years to come, though the brighter stars will fade long before then. If the universe was a human being, it would still only be about a month old.

Another factor may play a part. Carl Sagan has described how the modern alien encounter/alien abduction mania perpetuates the phenomenon of encounters with angels and demons and with the Virgin Mary in earlier centuries. Could the flood of speculations about alien civilisations – where are they? are they hostile or friendly? – be the modern equivalent of the search for God? Do people still yearn to submit to an Overlord (the name given to the aliens in Arthur C. Clarke’s Childhood’s End), whether beneficent, or intent on our punishment?

Until we find any evidence of alien intelligence, the most parsimonious explanation is that there isn’t any where we have looked, that there is no invisible dragon in my garage (Sagan’s image). So we must look further, before it will be possible to use observations to rule out either of the models described here.


Ian Crawford, “Where Are They?”, Scientific American, July 2000, p.28-33.

Guillermo Gonzalez, Donald Brownlee and Peter D. Ward, “Refuges for Life in a Hostile Universe”, Scientific American, October 2001, p.52-59.

Michael A.G. Michaud, Contact with Alien Civilisations (Copernicus, 2007).

Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark (Headline, 1997); Contact (Century Hutchinson, 1986).

Robert Zubrin, “Interstellar Panspermia Reconsidered”, JBIS, vol.54, no.7/8 (July/August 2001), p.262-269.


Comments on this entry are closed.

  • Eniac September 21, 2013, 22:23


    So until we get that signal from Vega, the most parsimonious explanation of the existing facts is that life itself is of recent, space origin

    I do not follow that. The most parsimonious explanation surely is that life is of recent, Earth origin. What really pushes you away from that?

    But Geoffrey Hillend above says: “The elements necessary for the survival of life are most abundant on the surface of the Earth so that is where the highest chances are for it to originate.” Yes, agreed! So why has life not originated multiple times on Earth? Why is there not an independent abiogenesis on Earth every few hundred million years?

    Because abiogenesis is extremely unlikely, EVEN on Earth, where at least the conditions are right. Without the conditions, it is even much more unlikely, of course. I do not at all see any reason here to resort to a space origin, or to even consider it.

    Or is there only one possible molecular structure that life can use, so that independently originated organisms appear to have a common ancestry?

    It is not just the molecular structure, it is other things like certain highly conserved sequences, or the genetic code. It is inconceivable that all known life on Earth is not really related. With modern genomics, it can be excluded with astronomical certainty. If we ever found unrelated life, it would be easily identifiable as such.

  • Eniac September 21, 2013, 22:38


    I think of the ancient tribes who crossed the land bridge from Asia to North America. They took tens of thousands of years to spread by gradually moving to new hunting grounds until the entire continent was settled. What would they think of a man in a space capsule circling the globe every 88.5 minutes, able to drop out of orbit and parachute to a landing just about anywhere on that continent?

    They would be amazed, of course. As they would be by the sight of airplanes plying the sky, and highways criss-crossing the land. If such tribes were still around, however, they would no longer be amazed at those things. They would be using radios and cell-phones and SUVs, and be hosting anthropologists regularly. Contact with the modern world is unavoidable, simply because it has spread all over the globe. In an incredibly short few hundred years, too.

    The ant analogy is tired and misleading. Ants are not intelligent or curious, or even conscious in any meaningful way. And they will be affected when you decide you don’t want them coming into your house and let loose the chemical warfare agents. Or if their nest is where you want to build your shed.

  • Eniac September 21, 2013, 23:11

    Alex Tolley:

    Abiognesis is special in that there was no evolution to help bring it about.

    We really do not know what level of complexity evolution can apply its algorithms.

    Very true. However, it is reasonable to define the moment of abiogenesis as precisely the moment where evolution begins to act, in which case my statement would be tautologically true. The real issue is the rate of this happening (how often per unit of time), and that we do not know.

    That said, I do believe that we have some pretty good upper and lower limits on this rate. The absence of evidence for a previous Big Bang type expansion points pretty strongly (although perhaps not conclusively) towards an upper limit of “less than once in the galaxy per billion years” . The lower limit for the rate of abiogenesis is something like “about once in the universe per 10 billion years”. This rate would make a single occurrence likely, explaining our presence.

    In any case, the rate for a single planet is astronomically low, because we now know there are billions of planets in the galaxy and billions of billions in the universe. To get the rate for one planet, we have to divide the rates in the galaxy or the universe by the number of planets therein.

    I am assuming here that everything after abiogenesis has a much higher rate. Our best evidence for technology is about once every 3 billion years per planet, which is indeed astronomically faster than the above limits for abiogenesis. Of course, this is a very shaky estimate based on a sample of one, so there are certainly options here were abiogenesis is common, and expanding technological civilizations are rare. In my view, though, these are not the most parsimonious options, because of the game-changing effect of evolution.

  • Astronist September 22, 2013, 6:00

    Mark: you bring up one of the variations on the theme of “the aliens are there, but we don’t see them”: we’d have no more idea of the existence of ultra-high-tech aliens than ants do of us (an idea that Carl Sagan vividly portrayed in his novel Contact). So this is certainly a possible instance of the Big Bang model, but with our own position shifted to the right of the completion of the Big Bang.

    The reason why I did not include this in the essay is that in my view it is unscientific to postulate the existence of something which is not needed to explain the facts. The most parsimonious explanation of the evidence we have so far is that there are no other civilisations within current hailing range, and the logical corollary is that abiogenesis is rare, not common. As Rob Henry nicely put it: “a killer blow to the “just add water” school for the origin of life”.

    RonSmith: yes, you are quite right that these models are affected by the possibility of excessive radiation sterilising planets on a galaxy-wide scale. This pushes the first emergence of civilisation to the right, but does not, I think, invalidate this way of thinking about them, unless galaxy-wide sterlising events occur on a regular basis. Even then, it only disrupts the Steady State model, as civilisations advanced enough to colonise space and airless moons and planets would presumably be able to survive such a natural disaster.

    Eniac: ” let me observe that in the second figure, you might have added a third point (say, Z), in the time period before A. That would be us in the case that we do not make it, after all.” — thanks for this point, which is in fact taken care of by point A in the Hybrid model. I should have made the letters more consistent from one diagram to the next, for clarity.

    Stephen (Ashworth)

  • David Cummings September 22, 2013, 7:46

    Stephen, I just read http://www.astronist.demon.co.uk/astro-ev/ae090.html and find it very interesting.

    I’m on the fence on the whole singularity/plateau argument but I find your linked article very persuasive. I would like to ask you what you think of the “Robot Reply” to the John Searle Chinese Room argument (http://plato.stanford.edu/entries/chinese-room/#4.2)

    As an update to the Searle Chinese Room itself, I would like to point out that no one in their right mind would say that the google servers that translate the question ¿dónde está la zapatería? know anything about shoes. You could easily program those (or any) servers to spit out a bunch of information about shoes — endless links on suppliers, prices, sizes, styles, etc — but still the servers themselves (or any of their software components) would not have the slightest inkling of what a shoe really is.

    However, I do have a weakness for the “Robot Reply” and would like to get your response to it.

    Thanks for posting that link.

  • David Cummings September 22, 2013, 7:52

    Alex, you are absolutely right on the question of “independent abiogenesis on Earth every few hundred million years”.

    There could be”independent abiogenesis on Earth every day, even every hour” and as soon as an “independent entity” reared its tiny and extremely-vulnerable head, it would last about 30 seconds before becoming a snack to some roving microbe. In fact, bands of roving microbes would probably fight over it to see who gets the privilege of eating it first!

  • Mark Lee September 23, 2013, 4:23

    Thinking that we are the only intelligent civilization in the entire MW galaxy would be equivalent to thinking that there is only one habitable planet in the entire MW galaxy. Therefore, the most likely scenario is that there are many intelligent civilizations currently growing throughout the MW galaxy and we are currently too far away in distance and time to the nearest intelligent civilization. One can imagine that the civilizations spread throughout the MW galaxy would be as diverse as the nations spread throughout earth with the same co-operation and competition between the various civilizations, each with its own unique culture, religion, politics, technology, and philosophy. It would seem that we are like the Hawaii islands waiting for the first contact with foreigners with the complexity of both the good and bad consequences from the first contact.

    One way of proving this theory would be the observation of a multitude of habitable planets in the MW galaxy as currently occurring. Another possibility is the observation of planetary scale structures being built by advanced civilizations or anomalies in the MW galaxy generated from growing civilizations.

  • Sedjak September 23, 2013, 15:49

    The Hybrid model is really the Zoo model. If the background steady-state genesis of technological civilizations produces on the order of thousands or millions of inhabited star systems, then given Stephen’s relatively small time to colonize the galaxy of 20 million years in the Big Bang model, in a galaxy conducive for life for at least 5 billion years, the first sufficiently advanced civilization could rule the galaxy. In the case of a slower or Fermi-paradox mediated crawl to the galaxy’s edges on the order of a billion years, then its much more likely in a Hybrid model that multiple Bangers divy up and colonize suitable (hopefully not civilization-bound) star systems, how ever that drama might play out. Assuming late-comer Banger civilizations and working with Stephen’s 1000 steady-state civilizations in a Hybrid model would eventually make for on the order of 100 million potential Banger-colonized star systems surrounding each nascent civilization (kinda scary, huh?) And it wouldn’t really matter when the super-advanced or aggressive Banger came along (including us) since it could completely fill out the galaxy relative to the pokey steady-staters if there was any room left.

    We have to go beyond benevolent, then, to give the newer kids on the block any fighting chance. The altruistic elder civilizations may leave breathing room of spheres of varying light-years depending on how interesting potential systems are, up to a radius of, say, 1000 light-years. Its highly unlikely that an advanced intelligence would colonize up to the doorstep of a proto-Earth and then dismantle thousands or millions of colonies as the newbies became space-faring, unless they could cloak them. What I am getting to here is that the nice Bangers or somewhat restrained Elders would purposefully have to hold back on colonizing the whole galaxy if they were interested in some kind of eventual Federation, a peaceful co-existence, interesting science, or at least some Interstellar Zoos and Parks. Even if they left around 10^8 star systems for each up and coming civilization, they could have already colonized (or seeded) ~ 10^11, or half the galaxy, and remain the stewards or Big Galactic Brother. The ultimate altruistic Elder civilization could perhaps quarantine itself within a radius of maybe a 1000 light-year sphere or unwisely not colonize at all!

    These latter philosophies could prove disastrous were the late but rapid-blooming Bangers to absolutely restrain themselves, and similarly for any Elders playing the role of the “Native” in the New World. Each could not guarantee that in millions of years hence that the newbie civilizations would not have designs on the whole galaxy. So at some point forced entry into the existing Federation — or colonial Africa :( — would be mandatory or the newbies could alternatively be completely culled by sentinels (thx Alastair), aggressively trimmed around the edges, reigned in by super-advanced non-lethal technology like an immense force field, or, less likely, agreed to be self-policed.

    In the case that we are not first and foremost, if our galaxy is hosting any kind of Hybrid or Big Bang model then our young Sol system is most likely already surrounded by uncountable civilizations and probes, as they would spring up and fill the galaxy like popcorn. Barring FTL communication or travel and given enough time, the explorer civilizations of each expanding post-singularity culture would be as different from their root civilization as they would be from each other…

    Simulating an evolving galaxy filled with ETIs by varying a few parameters in the Drake equation, varying expansion speeds (.001c-.5c), varying the benevolent-aggressive axis in the contact points between civilizations (war vs peace vs ambivalence), varying the level of quarantining, etc, might at least behoove us in understanding the Fermi paradox.

    This rambling aside, the moon must harbor millions or billions of tons of pristine radiation-shielded meteorite-blasted Earth rocks. So we may yet find the missing link between the organic soup and single-celled organisms.

  • Eniac September 23, 2013, 19:25

    Mark Lee:

    Thinking that we are the only intelligent civilization in the entire MW galaxy would be equivalent to thinking that there is only one habitable planet in the entire MW galaxy.

    No it is not. You could also be thinking that inhabitable planets are not necessarily inhabited.

  • Eniac September 23, 2013, 19:46


    RonSmith: yes, you are quite right that these models are affected by the possibility of excessive radiation sterilising planets on a galaxy-wide scale.

    Technically, this is correct, but in fact there is no known mechanisms for such a catastrophe. Interstellar distances make even the most violent of cosmic cataclysms ineffective at affecting the surfaces of far-away planets to any serious extent, much less “sterilize” them. Atmosphere, ocean, and crust are very effective at stopping what radiation remains after being spread thin by the enormous distance. From just tens of light years away, much less across the entire galaxy.

  • David Cummings September 23, 2013, 20:59

    Sedjak, thinking about your speculations of a galaxy filled with ETI’s and the possibility of quarantines and other zoo-scenarios, I think it behooves us to keep our eyes open. Maybe one of the visitors (now or in the past) dropped something. It’s good to have all those pictures from the surface of Mars, with a huge crowd-sourced effort to look for anything we can see there. Something might just pop up out of the sand some day and surprise us all. Some weird shaped object. Some twisted bolt or fastener that we can’t understand to look at other than to know that it sure the heck ain’t ours.

  • Brett Bellmore September 24, 2013, 12:32

    But we also need to keep our minds open to the possiblity that we really are at point “A” of the big bang model, and stand to inherit a galaxy… If we don’t dawdle so long that some natural phenomenon knocks Earthly life back to the single cell stage.

    I’m somewhat persuaded by the “rare Earth hypothesis”, briefly that while the origin of life is fairly common in the universe, the universe is a rough enough place that we’ve been extraordinarilly lucky to have a stable environment long enough to have evolved intelligence. All it takes is one decent asteroid impact, after all, and Earth will have to repopulate from the surviving bacteria.

    If we make it out into the galaxy, we’re going to find a lot of planets where the highest life is algae.

  • Eniac September 24, 2013, 21:58

    Brett Bellmore:

    All it takes is one decent asteroid impact, after all, and Earth will have to repopulate from the surviving bacteria.

    In all the 2 billion years of eukaryotic life on Earth, it has never, ever, had to “repopulate from surviving bacteria”. Same thing for 1 billion years of continuous presence of multicellular life. Something this rare is not likely to happen in the paltry few hundred years that it would presumably take us to finally get our a**es off this miserable third rock from the sun.

  • Rob Henry September 25, 2013, 0:43

    Astronist wrote
    “Keith Cooper: thanks! Yes, clearly there are two forms of intelligence. I was referring to technological intelligence, but it is clear that a non-technological form of intelligence is also possible, as exhibited by monkeys, cetaceans and the larger species of octopus on Earth.”

    I have a reply to that that is so bazaar, that at first I didn’t believe it myself. To me by ‘intelligence’ in this context we would never mean “monkeys, cetaceans and the larger species of octopus” we would only be talking of creatures of a level of sophistication equal to our first civilizations. On earth today there are only 2 animals that have that level of IMPACT on Earth. Man, and if you look at “fertilization of the sea” in Wikipedia, you will find the other – sperm whales. I have seen the effect estimated at a third of a watt per square metre in terms of greenhouse gas.

    We assume they do it by dumb luck, because ‘they love diving for squid’ but looking through the limited data on the matter, it is not at all obvious that that their diet doesn’t consist of more surface fish, in the quarter of their waking hours they spend topside yet it takes massive energy to dive as deep as they do. Doesn’t make sense does it!

    And that they sleep at all is stunning – all other cetaceans just sleep one brain hemisphere at a time – it’s one of leading reasons for explaining why they need such big brains ie that their hemisphere aren’t designed to coordinate as a single powerful unit. Sperm whales may not be the biggest whales, but they have the biggest brains of any creature – ever. Yet evolutionary pressure is so thirsty to add even more to their brain power that it makes them the only cetaceans that put themselves through a vulnerable sleep phase.

    Sure you say, all massive coincidence their ‘coda’ language only has two dozen words, so it can’t be. That’s what I thought too, so I checked the largest analysis of their language I could find.
    it analyses them with powerful Duda-Hart based software, and taking it naively by the normal criteria it detected about three hundred discreet words that had been used repeatedly on a sample space just 1800 coda words. They called that an obvious failure, but were at a loss as to why (they gave an example of how it could fail, but that was not applicable here). The reason why they thought it failed…

    “However, this particular method does not seem to be robust with coda data that was recorded at the Canary Islands; based on visual observations at the time of the recordings the method showed a tendency to find an unreasonable large number of clusters.”

  • Astronist September 25, 2013, 6:01

    Eniac: thanks for the correction.

    David Cummings: I’m sure you’re right that having a rich life of interactions with the physical world is part of the answer to Searle’s Chinese Room argument. But perhaps this is part of a larger issue. In his book Beyond AI: Creating the Conscience of the Machine (Prometheus, 2007), J. Storrs Hall writes: “The crux of the philosophical argument over AI is whether the quantitative difference between the Chinese Room and a computer system capable of real human-level performance is enough to amount to the qualitative difference between syntax and semantics” (p.276). He argues that the human brain is about a trillion times more complex than the scenario envisioned in the Chinese Room, and adds: “There is no case in our experience where a difference of a factor of a trillion doesn’t make a qualitative, as opposed to merely a quantitative, difference.”

    In other words, we understand because of the sheer size of our brains allows vastly greater complexity of interactions than that envisaged in the Chinese Room (including, of course, years of interactions with the physical world as in the robot reply). But I would only add: reproducing this pattern in an artificially constructed machine will not come easily; we will not simply build a huge machine that takes over the world in 2030 or 2040. More plausible by far, I would suggest, is a gradual evolution in which machine intelligence slowly improves, but at the same time is continually more closely integrated with our biological brains.

    Stephen (Ashworth)

  • Brett Bellmore September 25, 2013, 6:03

    Eniac: That’s rather the point. Either “that kind of thing” is rare, or we’ve been lucky to have gone without some such event long enough to have reached this level of biological and social development.

    I concur that a major asteroid impact of that scale isn’t likely before we *can* get our asses off this rock, though the sort of comparatively ‘minor’ impact necessary to reduce us to the stone age again, only with fewer easily exploited ore bodies, is presumably much more likely.

  • Ron S September 25, 2013, 11:12

    Brett: ‘Either “that kind of thing” is rare, or we’ve been lucky…’

    If you carefully think about those two clauses you’ll see that they are equivalent.

  • Rob Henry September 25, 2013, 17:25

    Could someone else please look at the above article I referenced. They seem to have some basic mistakes to miss this discovery – which taken on its superficial appearance to me is could be the greatest of all time.

    Unless they did something weird with the input data, one dimensional input data as for the normalised three click coda can’t be ‘elongated’ they can only be a perfect one dimensional sphere in terms of the direction of their spread – though they may not follow the normal distribution. There is no reason I can think of for the sample of 859 one dimensional data points to fall into 183 clusters by a Duda-Hart analysis other than them representing a real effect. As the number of clicks increases, so does the number of dimensions analysed, yet, as expected in a true language, their representation in the sample tapers of dramatically, Thus, the sample was only large enough to properly analyse the three click coda, but their language is known to go up to twenty clicks.

    What I’m saying is that we seem to have a prima facie case that sperm whales have a more complex language than ours. This is not a warm fuzzy point I’m making, but a statement that they could be so bright that their small pods might be able to decode lincos, or continue a sequence of prime numbers.

    I know everyone will think this all crazy; I would have thought so to a week ago, and before I took a close look at that article.

  • David Cummings September 25, 2013, 18:02

    Stephen, I agree with you that “a gradual evolution in which machine intelligence slowly improves, but at the same time is continually more closely integrated with our biological brains” is the most plausible line of development of AI.

    I forget who called AI “augmented intelligence” instead of “artificial intelligence”. Maybe Vernor Vinge.

  • David Cummings September 25, 2013, 18:05

    As for the Fermi Paradox… maybe we are living in a Rare Galaxy.

    There are at least 100 billion galaxies in our universe and let’s suppose that at Age Of Universe = 13 billion years the number of Technological Civilizations (TC’s) averages 50-per-galaxy.

    Since the average size of a galaxy is 100 billion stars, that means, on average, one TC for every 200 million stars. (That should be reasonably compatible with the Drake Equation.)

    But 50TC/galaxy is an average (hypothetical of course) and the actual distribution would be a bell curve — like most distributions.

    Most galaxies fall somewhere in the middle of the curve and have about 50TC’s and the current age of about 13 billion years since the Big Bang.

    On the far right of the curve there are a small number of galaxies that have an unusual number of TCs… 100 or more.

    At the far left, the number of TCs/galaxy is very small. Maybe a very small number of galaxies have only a single TC at Age of Universe 13 billion years. These are Rare Galaxies, and maybe we are living on one of them.

    Pure conjecture, I know. But provable and disprovable. Someday, as our astronomical technology increases, we should be able to say with some confidence whether we see Them in other galaxies… and how many of Them we see.

  • Astronist September 26, 2013, 6:23

    Sedjak: “The Hybrid model is really the Zoo model” — not so, though you could if you wanted include the Zoo model in it if you placed us to the right of the completion of the Big Bang.

    I would suggest that the Zoo model is unsatisfactory, because it is a variant of the class of hypotheses in which the aliens exist, but we cannot see them. The scientific method prefers the simplest explanation of the facts as known at present, and the simplest explanation of not seeing any alien cultures is because there aren’t any (with the logical corollary, as I explained, that abiogenesis occurred recently, not long before Earth itself formed). But of course we need to keep testing the simplest explanation against new observations.

    Stephen (Ashworth)

  • ljk September 26, 2013, 14:09

    September 25, 2013

    “The Great Search” –Beyond Drake’s Equation (Today’s Most Popular)

    The SETI project – Search for Extra-Terrestrial Intelligence – has been in existence in one form or another for several decades, dating back to American astronomer Frank Drake’s first SETI experiment named Project Ozma. SETI is basically the search for intelligence through listening for radio waves of another civilization. For Drake back in the 1960s, this was the sign of a technologically prevalent society, and the smartest means to search for life.

    Beyond 500 light-years away, the chance of detecting any signal from an advanced civilization approaches zero. And that is exactly the range in which our present technology is searching for extraterrestrial radio signals. So, the “Great Silence” detected by our radio telescopes is not discouraging at all. Our signals just need to travel a little farther – at least 900 light years more – before they have a high chance of coming across an advanced alien civilization.

    In 1961 the Russian cosmonaut Yuri Gagarin became the first man to orbit Earth, while Frank Drake (image below) developed his now famous Drake Equation, which estimates the number of detectable extraterrestrial civilizations in our Milky Way galaxy, based on current electromagnetic detection methods.

    Full article here:


  • Astronist September 27, 2013, 18:15

    ljk: Thank you, but the article you reference misses the point that if interstellar colonisation is possible, then the Drake Equation is simply invalid, because in a relatively short period of time the locations where civilisation is found become overwhelmingly colonies and no longer dependent upon Earth-analogue planets!


  • Rob Henry September 27, 2013, 20:36

    Sorry, the last couple of my posts were written without benefit of much sleep. All is I know for certain is that I have found a massive error in a peer reviewed paper analyzing sperm whale coda data. To me this will have a different implication to you, since I was using to test a favorite hypothesis of mine.

    Since it is clear from the paper that the authors had no idea how the statistics they were using worked, the most parsimonious explanation is that they simply entered data for the normalized three click coda interval in the form (x,1-x) instead of correctly entering it as just (x), but, considering its potential consequences, it is something I will have to follow up

  • Eniac September 27, 2013, 22:19

    David Cummings:

    As for the Fermi Paradox… maybe we are living in a Rare Galaxy.

    There are at least 100 billion galaxies in our universe and let’s suppose that at Age Of Universe = 13 billion years the number of Technological Civilizations (TC’s) averages 50-per-galaxy.

    An intriguing thought. But why suppose the arbitrary number of 50-per-galaxy? I think it is much more interesting to suppose 0.00000000001-per-galaxy. You supposition implies that we are just incredibly unlucky to be in that one empty galaxy out of billions teeming with life. Does my supposition mean the opposite, that we are lucky?

    It doesn’t, because we do not have to be lucky. We HAVE to be in that one rare galaxy that is inhabited, naturally. It could be no other way, it is 100 percent certain!

  • Stan September 30, 2013, 0:14

    @Swage He has the first good reasoning I’ve seen that could have all civilizations advancing at about the same time in galactic history, us included. That is that the galaxy could be colonized totally by bacteria instead of technology. He has the time from one star to another at 40k years. That’s a big bang colonization of the galaxy by the first bacteria complex enough to survive the trip. That might explain why we haven’t detected ETIs. Because we’re all at about the same stage.

  • Brett Bellmore September 30, 2013, 18:21

    Yeah, but this presumes a roughly uniform delay between colonization by bacteria and the evolution of intelligence and technology. Considering the three to four billion years between one and the other, compared to 1-10 million years to colonize the galaxy, that’s either an awfully precise delay, or we’re back to being number one.

  • Zen Blade October 2, 2013, 11:07

    wow, great thread and post.
    Sorry I missed reading it while it was hot.

    I’ll just add that lack of evidence for pre-bacterial life does not mean that the predecessors had to come from off planet.
    What the heck would one expect to find as evidence that the earlier forms of life existed. They almost certainly had no hard body material that could be found as fossils… even “fossilized evidence of bacteria” is often controversial as various chemical reactions can produce similar by products.
    So, no fossils…
    As for the persistence of those organisms, well, we don’t see persistence of other hominids within the homo genus because we have out competed them (all of them). Transitional species must exist, but they are often not going to be the most fit, and really only serve as a bridge between species/forms that are longer lasting.

    And if you follow the RNA world hypothesis, then there would be ZERO evidence or survivors of this early world except for the genetic evidence that persists today in the form of the ribosome and related RNA molecules that have never been replaced by protein substitutes.

    -Zen Blade