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Why Fill a Galaxy with Self-Reproducing Probes?

We can’t know whether there is a probe from another civilization – a von Neumann probe of the sort we discussed in the previous post – in our own Solar System unless we look for it. Even then, though, we have no guarantee that such a probe can be found. The Solar System is a vast place, and even if we home in on the more obvious targets, such as the Moon, and near-Earth objects in stable orbits, a well hidden artifact a billion or so years old, likely designed not to draw attention to itself, is a tricky catch.

As with any discussion of extraterrestrial civilizations, we’re left to ponder the possibilities and the likelihoods, acknowledging how little we know about whether life itself is widely found. One question opens up another. Abiogenesis may be spectacularly rare, or it may be commonplace. What we eventually find in the ice moons of the outer system should offer us some clues, but widespread life doesn’t itself translate into intelligent, tool-making life. But for today, let’s assume intelligent toolmakers and long-lived societies, and ponder what their motives might be.

Let’s also acknowledge the obvious. In looking at motivations, we can only peer through a human lens. The actions of extraterrestrial civilizations, and certainly their outlook on existence itself, would be opaque to us. They would possibly act in ways we consider inexplicable, for reasons that defy the logic we apply to human decisions. But today’s post is a romp into the conjectural, and it’s a reflection of the fact that being human, we want to know more about these things and have to start somewhere.

Motivations of the Probe Builders

Greg Matloff suggests in his paper on von Neumann probes that one reason a civilization might fill the galaxy with these devices is the possibly universal wish to transcend death. A walk through the Roman ruins scattered around what was once the province of Gaul gave weight to the concept when my wife and I prowled round the south of France some years back. Humans, at least, want to put down a marker. They want to be remembered, and their imprint upon a landscape can be unforgettable.

But in von Neumann terms, I have trouble with this one. I stood next to a Roman wall near Saint-Rémy-de-Provence on a late summer day and felt the poignancy of all artifacts worn by time, but the Romans were decidedly mortal. They knew death was a horizon bounding a short life, and could transcend it only through propitiations to their gods and monuments to their prowess. A civilization that is truly long-lived, defined not by centuries but aeons, may have less regard for personal aggrandizement and even less sense of a coming demise. Life might seem to stretch indefinitely before it.

Image: Some of the ruins of the Roman settlement at Glanum in Saint-Rémy-de-Provence, recovered through excavations beginning in 1921. Walking here caused me to reflect on how potent memorials and monuments would be to a species that had all but transcended death. Would the impulse to build them be enhanced, or would it gradually disappear?

Probes as a means of species reproduction, another Matloff suggestion, ring more true to me, and I would suggest this may flag a biological universal, the drive to preserve the species despite the death of the individual. Here we’re in familiar science fiction terrain in which biological material is preserved by machines and flung to the stars, to be activated upon arrival and raised to awareness by artificial intelligence. Or we could go further – Matloff does – to say that biological materials may prove unnecessary, with computer uploads of the minds of the builders taking their place, another SF trope.

I can go with that as a satisfactory motivator, and it’s enough to make me want to at least try to find what Jim Benford calls ‘lurkers’ in our own corner of the galaxy. Another motivator that deeply satisfies me because it’s so universal among humankind is simple curiosity. A long-lived, perhaps immortal civilization that wants to explore can send von Neumann probes everywhere possible in the hope of learning everything it can about the universe. Encyclopedia Galactica? Why not? Imputing any human motive to an extraterrestrial civilization is dangerous, of course, but we have little else to go on. And centuries of human researchers and librarians attest to the power of this one.

Would such probes be configured to establish communication with any societies that arise on the planets under observation? This is the Bracewell probe notion that extends von Neumann self-reproduction to include this much more immediate form of SETI, with potential knowledge stored at planetary distances. Obviously, 2001: A Space Odyssey comes to mind as we recall the mysterious monoliths found on the early Earth and, much later, on the Moon, and the changes to humanity they portend.

But are long-lived civilizations necessarily friendly? Fred Saberhagen’s ‘berserker’ probes key off the Germanic and particularly Norse freelance bodyguards and specialized troops that became fixtures at the courts of royalty in early medieval times (the word is from the Old Norse word meaning ‘bearskin’). These were not guys you wanted to mess with, and associations with their attire of bear and wolfskins seem to have contributed to the legend of werewolves. Old Norse records show that they were prominent at the court of Norway’s king Harald I Fairhair (reigned 872–930).

Because they made violence into a way of life, we should hope not to find the kind of probe that would be named after them, which might be sent out to eliminate competition. Thus Saberhagen’s portrayal of berserker probes sterilizing planets just as advanced life begins to appear. The fact that we have not yet been sterilized may be due to the possibility that such a probe does not yet consider us ‘advanced,’ but more likely implies we have no berserker probes nearby. Let’s hope to keep it that way.

Or what about the spread of life itself? If abiogenesis does turn out to be unusually rare, it’s possible that any civilization with the power to do so would decide to seed the cosmos with life. In this case, we’re not sending uploaded intelligence or biological beings in embryonic form in our probes, but rather the most basic lifeforms that can proliferate on any planets offering the right conditions for their development. Perhaps there becomes an imperative – written about, for example, by Michael Mautner and Matloff himself – to spread life as a way to transform the cosmos. Milan Ćirković continues to explore the implications of just such an effort.

In an interesting post in Sentient Developments, Canadian futurist George Dvorsky points out that self-reproduction has more than an outward-looking component. Supposing a civilization interested in building a megastructure – a Dyson sphere, let’s say – decides to harness self-reproduction to supply the needed ‘worker’ devices that would mine the local stellar system and create the object in question.

At a truly cosmic level, Matloff speculates, self-replicating probes might be deployed to build megastructures that could alter the course of cosmic evolution. We’re in Stapledon territory now, freely mixing philosophy and wonder. We’re also in the arena claimed by Frank Tipler in his The Physics of Immortality (Doubleday, 1994).

We’ll want to search the Earth Trojan asteroids and co-orbitals for any indication of extraterrestrial probes, though it’s also true that the abundant resources of the Kuiper Belt might make operations there attractive to this kind of intelligence. One of the biggest questions has to do with the size of such probes. Here I’ll quote Matloff:

In a search for active or quiescent von Neumann probes in the solar system, human science would contend with great uncertainty regarding the size of such objects. Some science fiction authors contend that these devices might be the size of small planetary satellites (see for example L. Johnson, Mission to Methone and A. Reynolds, Pushing Ice). On the other hand, Haqq-Misra and Kopparapu (2012) believe that they may be in the 1-10 m size range of contemporary human space probes and these might be observable.

But there may be a limit to von Neumann probe detection. If they can be nano-miniaturized as suggested by Tipler (1994), the solar system might swarm with them and detection efforts would likely fail.

I remember having a long phone conversation two decades ago with Robert Freitas on this very point. Freitas had originally come up with a self-reproducing probe concept at the macro-scale called REPRO, but went on to delve into the implications of nano-technology. He made Matloff’s point in our discussion: If probe technologies operate at this scale, the surface of planet Earth itself could be home to an observing network about which we would have no awareness. Self-reproductive probes will be hard to rule out, but looking where we can to screen for the obvious makes sense.

The paper is Matloff, “Von Neumann probes: rationale, propulsion, interstellar transfer timing,” International Journal of Astrobiology, published online by Cambridge University Press 28 February 2022 (abstract).

{ 48 comments… add one }
  • Michael Fidler March 10, 2022, 9:58

    One of the problems I see is the same as the Mars Canals. The beginning of the 20th century saw a huge effert to to make the Panama canal and the earlier Suez Canal. Irrigation in many places was becoming a important project for goverments. So Canels on Mars fit well with the publics IQ. So now we have nano-technology and soon quantum entangelment. Going the other direction you end up with dyson spheres, etc… Here may be the oldest method to find unknowns, like our eyes, the Argus Optical Array.

    Low-Cost Access to the Deep, High-Cadence Sky: the Argus Optical Array.


    900 of these little babies; 8″ 200mm apature F2.8 Rowe-Ackermann Schmidt Astrograph


    Now we need AI to look thru the data for all those mysteries objects…

  • Henry Cordova March 10, 2022, 11:19

    It’s not unreasonable to assume advanced civilizations might design and disperse self-replicating probes. After all, nature, without any intelligent design behind it , appears to have done the exact same thing using natural selection. Living things, even the simplest microbes, are self-replicating von Neumann probes.

    But there appears to be some fundamental differences between “artificial” and “natural” self-replicating organisms. To begin with, one would expect life-as-an-artifact to have some purpose, some overall mission, a raison d’etre programmed into it by its creators.. No such motivation seems to be a part of the biological realm. Like the rest of the universe, as far as we can tell, there appears to be a reason for everything, but a purpose to nothing.

    And there is another consideration, one probably intimately associated with the first. In order to survive in an unpredictable and ever-changing environment, living organisms must not only be capable of reproduction, but also of evolution. Living things (as well as von Neumann devices) not only must be able to maintain their structural and behavioral integrity in the short term, they must be able to change it in the long term. Whatever morphology and behavior they may been programmed with, they must be able to adapt to meet new conditions.

    So far, the only initial programming we seem to be able to detect in organic life is the “instinct of self-preservation”. At the individual level,
    the species level, and even at the taxonomic level, all living things seem to go to extraordinary lengths to stay alive, and to reproduce.

    This seems to be the only rationale behind any living thing, and it is not part of their initial programming, it is the inevitable consequence of their existence. If they weren’t that way to begin way, it is unlikely they would have lasted long enough to reproduce.

    There is no reason to believe there can be no von Neumann machines prowling about the cosmos, they are certainly possible, but there is little reason for there to actually be any. All living things, and certainly all conceivable advanced civilizations, are ALREADY self-replicating probes. They don’t need to make any more. In fact, since their ultimate form and behavior can’t be predicted, it might be very wise to not turn any loose on the universe.

    • Alex Tolley March 10, 2022, 17:05

      I agree with what you are saying. Life certainly is algorithmically driven to evolve to successfully occupy every spatial and ecological niche it can.

      However, we don’t know if it can successfully travel across interstellar space to find new places to occupy. So far we are only fairly sure technology can do that. Technology can increase the probability that life does spread to suitable habitats.

      Von neuman probes solve the cost problem of manufacturing billions of probes, much like bioreactors solve the problem of ensuring cellular replication can be maximized within it. The other benefit of self-replication at the destination is that the journey times are reduced for each offspring.

      However, given your argument about the possible evolution of VN probes and the unexpected consequences, perhaps the better solution is more like our bioreactors. Let the probes self-replicate under controlled conditions in the host system, and send the probes from there with no further replication possible. The energy and material cost may be high as it must all be supplied from the host system, but that may be the most responsible approach.

      In effect we are thinking about this already. Tiny laser propelled sails, carrying life and with enough smarts to make decisions on reaching target systems, could seed worlds with life. At 20% c, the galaxy could be easily visited by one or more probes within 1 million years. Life would then take billions of years to evolve into complex life and perhaps new technological civilizations. If those sails could self-replicate like cells in our system but then be incapable of further replication, we could establish our sail reactors to create sails, and send them on their way with the bacterial/archaean/plant spores/seeds. Sterile worlds would be seeded and maybe mature into rich biospheres. Our civilization might not even survive to see more than a handful of worlds successfully seeded and on the road to achieving a biosphere. The only observers would be civilizations that emerged in the deep future, whether from our seeding efforts, other civilizations’ seeding efforts, or their own abiogenesis.

      A possible issue is that if our seeding efforts are not unique, we may find ourselves creating competing biologies with other seeding efforts. In this regard, in the future, we may detect such multiple seeding efforts from other extant or extinct civilizations, if we find connections between biologies on different worlds, like a patchwork distribution of different basic biologies, where each dominated some worlds and failed on others. It would be interesting if it turned out that civilizations were biologically driven to replicate their own biologies and aggressively competed for dominance. We might even be one of the successful efforts should it be found that our biology is exactly replicated in other star systems where panspermia probabilities are too low and abiogenesis probabilities of exact duplication also too low compared to directed seeding efforts.

      • Henry Cordova March 11, 2022, 1:02

        Hmmm…So maybe spacefaring civilizations are DNA’s mechanism to allow it to travel to other stars.

        That is, biological organisms cannot leave a planetary surface and colonize another until they evolve to a point where they can develop a technology that will allow them to do so. In other words, sentience and civilization are not the apex of organic evolution, they’re just an adaptation that allows DNA to spread more efficiently. Maybe the Mad Molecule isn’t just a feature common to all living things, maybe civilizations are just an organ evolved for transport purposes.

        Civilization and intelligence just a transport mode for nucleic acid. Isn’t that a humbling thought?

        • Alex Tolley March 11, 2022, 11:42

          Dawkins might well agree with that thought.

        • DCM March 13, 2022, 12:25

          Purpose is the biological activity of fulfilling matter and energy goals, meaning is the psychological or conscious aspect of purpose.
          Is knowing that “humbling” or merely awareness of a truth?

  • Brett March 10, 2022, 12:17

    I could imagine a civilization of immortals creating monuments to memory, so they can find concrete mementos of events within a vast span of lived time. But they might also just have ways of storing memories for the long run in ultra-secure back-ups, and perhaps not care about that either.

    One issue I have with species reproduction as a cause for sending them is that a civilization that advanced probably also has the capabilities to heavily modify themselves. They may simply not have a drive for species reproduction, seeing it as something that only needs to be done when there’s a pressing need for more beings.

  • Alex Tolley March 10, 2022, 13:13

    I have difficulty in accepting VN probes are in our system replicating to do some sort of local cosmic engineering. We have the same problem with ET technology levels – they are either very primitive or very advanced, but unlikely to be anywhere close to our level of technology. With probes, either they are no here, or they have been here for a very long time and therefore any engineering has already been accomplished.

    A recent article in New Scientist suggested our solar system planetary arrangement looks like it is not common but freakish. We might then consider that any probes have either ensured that arrangement billions of years ago, or still maintain it. Possible, but smacks of the intention and power of deities. Not a good hypothesis.

    There needn’t be binary classifications of probe sizes either (large such as Reynolds “Pushing Ice”, to nanotech everywhere). All scales may be present to do certain tasks. An Oort object would be hard to find unless it is doing something that makes it stand out. Ubiquitous nanotech has limits on the tasks it can perform, although it could, in principle, be actively modifying genomes, like viruses.

    Our current set of crises might be deliberate meddling by ET to ensure we self-destruct. But more likely it is just the failure of humanity to truly transcend its short-term thinking and rationally plan the future.

    The only “monument” that I see is a rich, functioning biosphere. That could be a motive for a long-lived civilization. It may be as simple as a galactic art project, or a desire to let intelligent organisms evolve that they can interact with. This would be a deep-time version of Brin’s “Uplift”.

    The problem we have is that we don’t have any evidence for any of this. We don’t see, or at least don’t recognize, any artificiality in our galaxy. No megastructures that probes have completed for unknown purposes. No other signs of advanced civilization. We don’t see or recognize any indications locally either.

    Suppose we did find some advanced technology probe in our system. Could we understand its purpose? It might prove as difficult to understand as the artifacts in Strugatsky’s “Roadside Picnic”. Even human technology from the past can be inscrutable, and a millennium from now, many of today’s technological artifacts may prove impossible to understand, and certainly, most software will be totally opaque to understanding.

    Given the size of our system, our best chance of finding something might be by serendipity via huge coverage by billions of low-cost probes where chance results in a discovery, simply by coverage, rather than directed search.

    • Michael Fidler March 10, 2022, 17:09

      Speaking of our unusual solar system, the very odd fact of the Earth’s total solar eclipses makes the idea of intervention seem even more likely. There are many things you can read into this fact but the two most important is our ability to understand how the sun works from solar eclipses and the development of nuclear fusion and that our active ecosphere is reflected in the active surface of the sun so magnificently during a total solar eclipse.

      • Henry Cordova March 11, 2022, 9:55

        Much nonsense has been proposed based on the fact that the lunar and solar discs (as seen from the surface of the earth) appear approximately the same size. The moon’s orbit is changing, this coincidence is only an accident that will not last long, in terms of deep time. The alignment is a temporary thing.

        Any “intervention” that might have arranged this perfect alignment would also have to have taken into account WHEN the human race would have developed to a point where eclipses where observable and widely commented on by sentient observers.

        I personally witnessed the last solar eclipse visible over North America a few years ago. It was absolutely glorious, but if I had been born just a few million years earlier or later it never would have happened. at all. Would the Interventionists not only have the ability to coordinate orbital dynamics, but also be able to time the geometry so precisely to human evolution?

        Sometimes a cigar is just a cigar.

      • Alex Tolley March 11, 2022, 11:46

        So when do you think the tampering was done? Unless ET knew when humans would be able to use the solar eclipses then the tampering with the lunar orbit would have to be relatively recent in time as the Moon continues to increase its orbital radius as it slows the Earth’s rotation rate. Perhaps when they tampered our ancestors’ minds a few million years ago?

      • Michael Fidler March 11, 2022, 22:25

        Well, I have seen two solar eclipse, in 1988 here in the Philippines and in 2017 in Oregon, in both it was very impressive to see a giant hole in the sky. I’ll take that cigar and smoke it. Human evolution of the naked ape or how an ape has become so so jaded. We create all sorts of ideas of what is out in the universe from black holes to dark energy none of which is proven in our reality. Even exoplanets could be flat or square planets for all we see is shadows. As for how long this will exist, after I brought up the point here many years ago, NASA said it will exist for another 650 million years. So by thier determination they will all be annuler eclipses then. At this time in our history they are pretty much 50/50. If it is just a coincidence (The state or fact of occupying the same relative time and position or area in space.) then there must be a huge number of alien civilizations in our galaxy. It’s like the FERMI paradox in reverse. ;-}

        You can’t have your cake and eat it too.

        • Henry Cordova March 12, 2022, 10:59

          So what you’re really saying is…

          The creator(s) of Earth, Moon and Humanity could foretell that the life he, she, them or it seeded here would eventually evolve into an intelligent, surface-dwelling creature with hi-res eyes. Similarly, the climate would eventually generate a transparent atmosphere, all on a timetable that was carefully coordinated so this magical coincidence would enlighten those same creatures with a glimpse of The Ultimate Truth.

          If the orbital geometry that yields roughly similar apparent sizes to the Sun and Moon is indeed that long-lasting, then the fact we have evolved to the point we can speculate why is no coincidence at all. It was almost inevitable!

          It all sounds too much like Velikovsky to me, just one more pseudo-science substitute for the more traditional and pious Medieval mysticism, Hellenistic humbug, and Bronze Age baloney.

          I’m sorry, maybe its just overly subjective thinking on my part, but I feel much more at home (and safer!) in my blind, random, chaotic and indifferent universe than I ever could in yours.

          • Michael Fidler March 12, 2022, 23:14

            Lets tone this down a little because we are talking about the same thing and here are the basic 3 ways we may look at it.
            1. Somebody, thing or whatever was around long before us and decided that our solar system was a good place to start some life, etc, etc
            2. Total solar eclipse are just a coincidence and we happen to be here just when they are 50% annuler and 50% total.
            3. We are really a strange freak accident or was ordained by God, etc, etc..

            Now my own opinion is number 2 and most scientist would agree. But here is the problem with that, in that this is rare in most solar systems especialy this close to a large sun.

            Number 3 smells of the earth centerd universe and has religious connotations.

            Number one is just an idea to keep an open mind but not much evidence to support it.

            I like 2 for a very good reason that it may also mean that inteligent civilizations may be very common in our galaxy because we are seeing a 50/50 percent of annuler to total eclipses. This could be a very rare occurence for a maturing inteligent space faring civilizations to exist at that particular instant.

            An indifferent universe still works by chance and odds would favour more civilizations not living under a sun that has total solar eclipses. We may know this when enough habitable planets are found with large moons.

            I would appreciate if there are concepts that differ on this subject because the three I mention has been something I have been tossing around for decades.

            • Henry Cordova March 13, 2022, 12:11

              My money’s on 2.
              1. is highly unlikely, but not impossible,
              3. violates every tenet of my Faith. ;)

              We do need to keep an open mind, even supernatural explanations should not be summarily dismissed, after all, much of what science now routinely proposes and accepts is just as counter-intuitive, bizarre and spooky (a finite and evolving cosmos, creation from a singularity, universe-as-a-hologram, Dark Energy, Anthropic Principle, etc).

              There is plenty of mystery in our cosmos already, there is no need to resort to mysticism. At least, not yet.

              “We are, by definition, at the very center of the observable region. With increasing distance, our knowledge fades, and fades rapidly. Eventually, we reach the dim boundary—the utmost limits of our telescopes. There, we measure shadows, and we search among ghostly errors of measurement for landmarks that are scarcely more substantial. The search will continue. Not until the empirical resources are exhausted, need we pass on to the dreamy realms of speculation.”
              ― Edwin Hubble, The Realm of the Nebulae

        • Alex Tolley March 12, 2022, 15:42

          The extent of the solar eclipse depends on where and when the observer is viewing it. Most of the time, the eclipse will be partial, not total. The size of the moon eclipsing the sun will depend on its orbit, which we know is not perfectly circular.

          So not only do these aliens have to plan the orbit of the Moon (did their calculations not get it quite circular), but they need to know where the civilization will be located for full eclipses to be seen on a semi-regular basis.

          Worse, while one can calculate an average distance of the Moon from Earth over time, the vagaries of plate tectonics and landmass distributions appear to make the rate of changing distance quite variable. (It happens to be slow right now).

          All these predictions must be made, and still, the eclipses are not perfect for our time, although they would have been for our ape ancestors.

          Add to all this the long-term chaos in planetary orbits and any planning would have to be quite recent for it to have happened, certainly not when the earth was created or shortly thereafter.

          However, if the lunar orbit was changed much more recently (when they buried that monolith!) won’t there be evidence for us to find unless the manipulation was very subtle?

          As Henry C says, the eclipses are just coincidental. All else is numerology and superstition. Pantheistic religions have gods chasing each other across the sky. How did they describe eclipses with that model? [Had we evolved on Mars, I wonder what superstitions we would link to the orbits of Phobos and Deimos?]

          • Michael Fidler March 13, 2022, 9:49

            And I agree with Henry Cordova as you see in my last reply, but being coincidental has not changed the subject to it does not matter but only shows that such an unusual event is not the norm. In the excellent article on “A SETI Reality Check”
            Henry makes a very good point. Instead looking for a mirror refection of our Naked ape mentality we should be looking for the suttle indications as the Galileo Project is working on and the many other wide field searches for unusual indications. Saying no one is nearby may be for the simple reason that they do not play by our rules. Our AI and Transformers may be able to see thru the camouflage of advance civilazations.

            Will Transformers Take Over Artificial Intelligence?


      • DCM March 14, 2022, 12:13

        Everybody seems to be seeking intervention by other, “higher” entities. If we didn’t get to where we are on our own how did those creatures get to where they are? If others showed them how, then how’d those others get to that stage?
        The vast size of the universe makes it likely that any possible event — and for conscious entities, any possible illusion — will happen. So why can’t we be where one of those happened?
        Ultimately, I think, such interpretations are based on continuing religious concepts and on the self-hatred that’s been cultivated and taught in Western countries from the last century on. At least the religious interpretations are positive; self-hatred is not good.

      • Gramaglia Paolo May 16, 2022, 8:19

        The precognition of God Is demonstrated by the fact that he put our noses between our eyes, so we could later design spectacles.

  • Gary Wilson March 11, 2022, 14:24

    The simplest explanation I can think of to explain the lack of obvious non-human artificial structures in our solar system (at least not that we have detected) is that there are very few technological civilizations that have arisen in our galaxy and they are very far apart. In addition none of them have managed to reach the level of developing Von Neumann like self-replicating probes (they all have troubles and setbacks of their own just as we do). The only way to disprove this would be to explore a significant fraction of the galaxy. The distances are huge and even our machines would be very frail and susceptible to destruction by what I’ll call the friction (wear and tear) of travelling interstellar distances. The challenge to seed the galaxy is there in theory, but successfully achieving it hasn’t been done and probably indicates the degree of difficulty involved.

    • DCM March 17, 2022, 16:59

      Yes, it’s likely such civilizations are few and far between.
      And there’s no reason to assume them the inevitable outcome of any living systems as far as I can tell. Whatever works to get life to continue will be what we will find. Consciousness isn’t likely a necessity.
      Yet we need to go ahead and expand outward.

  • gbaikie March 11, 2022, 20:05

    –But for today, let’s assume intelligent toolmakers and long-lived societies, and ponder what their motives might be.–

    Must be a percent of them, fleeing their civilization.
    If fleeing their civilization, do they want to have anything to do with alien civilizations.
    Maybe if they are criminals of their civilization. But generally it seems unlikely. But they might want communicate with other alien civilizations- particularly if an alien civilization was not danger for them to communicate with. And particularly if they could profit in some way, exchanging information for information they might want. Or their information for some material need they could get from alien civilization.

  • Michael Fidler March 11, 2022, 22:37

    In this inaugural installment of “Our Cosmic Neighborhood”, Avi Loeb gives us perspectives on the challenges presented by any future attempts at communication with extraterrestrials.
    AVI LOEB·MARCH 10, 2022


  • Dimjo March 12, 2022, 8:54

    For data. The more advanced a civilization or entity the less likely naivete, ignorance, arrogance or curiosity influence their decisions. They would “monitor” their neighborhood. Make sure the neighbors/kids playing with nukes/black holes etc. don’t accidentally point them in the “wrong” direction.
    After evolving beyond a certain point, they “control” everything or “ascend to a different plane of existence”, whatever, but my point is, between two points of existence, all civilizations have “video” cameras and drones (probes) around their “hood”. If they see intelligence, biological or post biological, they are monitoring it.

  • torque_xtr March 12, 2022, 12:51

    The concept of ETI on microscale always fascinates me.

    Of course there might be some sand grains in Sahara populated by angels and we have no chance to find them. But if they are bound by forms of matter and physics we know of, or extrapolate, it might be not so hard to discover them.

    Microprobes wear out, malfunction, perish when they encounter unexpected conditions, just like lifeforms and our machines. And for any network designed to last aeons aeons, for each functioning probe there will be thousands or millions dead ones. Well, at least, I absolutely cannot imagine a technology which does not produce any waste and maintains itself intact over geological timespans.

    And here on Earth, a dead Lurker is much less a Lurker than a living one.

    I think of extracting some cores of sediments from river deltas, much like Martian strategy of biosignature search, and then thoroughly examining them for dead microLurkers washed from continents. Maybe making complete CRT scans and sending them to volunteers to look for “something highly unusual”, the real SETI@Home :-)))

    The second idea is that for any network, there has to be some way to transmit data, and this requires larger structures that emit some kind of signals – antennas, etc. A bigger active antenna could be spotted itself. Smaller antennas on the smartphone scale are more difficult to spot but require relays in near-Earth space or on Moon.

    Here on Earth, any conventional signals would be drowned in our noise, but I wonder if someone listened to the Moon closely for EM emissions or heat signatures which are not ours? (or asteroids)

    • Alex Tolley March 13, 2022, 12:33

      David Brin’s “Existence” has small probes that were activated under certain circumstances. Some ended up as artifacts in historical and art collections, others remained buried until activation allow detection.

      Microprobes, the size of grains of sand, or even pebbles, will make finding needles in haystacks a trivial proposition by contrast. There needs to be some method that makes them generate a signal, like metal detectorists finding coins and other metal artifacts. This may need to be done on a large scale.

      Bob Shaws’ “The Light of Other Days” had passive “slow glass” microbeads scattered over national territories. They would have been sufficiently ubiquitous to be detected by looking at soil samples. If microprobes, like the upcoming “smart dust” sensors, are sufficiently numerous, then they might be detectable by careful observation, a bit like finding and classifying microfossils in sediment cores.

      The assumption of needing to transmit may be false. Stealthy acquisition by a “sample return” alien probe might be all that is required to retrieve the stored information. Physically collecting the microprobes, or activating them to transmit information very locally, like the aforementioned metal detection. [Has anyone added high frequency signal analyzers to metal detectors in case the returned signal has embedded information? c.f. Brian McConnell’s recent posts here, and here on ET signal interpretation.]

      • torque_xtr March 16, 2022, 6:25

        Searching for micro-sized artifacts on Earth of course is a needle-in-a-haystack-class endeavour. No larger artifacts were found up to date. If microLurkers were abundant, we would have found some defunct ones accidentally, already. But this reminds me of dark matter search and it’s visualizations where limits of detection and explored volumes are plotted against the particle mass, showing widely different search domains. Micro-size is an underexplored domain just because dead artifacts the size of sand grain could not be spotted and recognized with a naked eye no matter how alien they look under a microscope.

        The assumption of many dead Lurkers per one living one is also ambiguous. If network units are designed to be (bio)degradable in the target planet’s conditions, than the “dead/living” ratio would be (much) less than “network age / unit lifetime” ratio. Still, some units could be conserved if they ended up under Greenland/Antarctic ice, anoxic sediments, etc…

  • ole burde March 12, 2022, 15:44

    If we are stupid enough to let selfreplicating mascines loose in the galaxy, where they will propably evolve to become our enemies, our decendants in the future will curse our memory when the fully evolved new non-biological lifeform comes back to exterminate humanity….why would anybody take such an enormous risk ? Death-wish ?

  • Robin Datta March 12, 2022, 22:07

    Turning over the apparent identical size of the solar and lunar disks while trying to extract some male bovine fecal material from the facts is like attributing the handful of universal physics constants to some source of intentionality, while conveniently overlooking the Anthropic Principle.

    The arrangement we view may be a roll of the dice. It permitted us, but that does not imply that something steered it for a specific purpose.

  • DCM March 13, 2022, 12:19

    It’s hard to see how a species or entire biopopulation would last long enough to achieve the technological level necessary for space travel if it lacked some kind of survival instinct or drive. Possibly something like jellyfish could exist as long as their planet without it but maybe not because those that survived and “prospered” for any reason would spread.

    • Henry Cordova March 14, 2022, 16:51

      Even coelenterates have the will to survive.

      Many years ago, I was standing on a pier in St. Petersburg, Florida, and watched as a moon jelly swam up and made contact with a circular oil slick floating on the surface. Upon touching it, the creature immediately recoiled and hurriedly swam back down into the depths. It remains a vivid memory now even after all these years.

      The cnidarians are amongst the simplest of the metazoan phyla, but they have sentience enough to recognize death when it brushes up against them.

      • DCM March 21, 2022, 3:53

        Maybe it’s common for pre-life to arise and even cross over to actual life but without some equivalent of a survival instinct. That could explain the seeming lack of “higher” life at least.

        • Alex Tolley March 21, 2022, 13:20

          Natural selection, whether of soups of chemicals, or living organisms works because of the key factor of successful replication. Failing to successfully replicate [enough] dooms this population to extinction. Behaviors that may look like sentience are usually programmed innate behaviors to avoid injury and death with the resulting reduced reproduction. All animals, and even plants, have mechanisms to avoid conditions that can be injurious, and also attracted to conditions that support feeding, growth, and reproduction.

          Any “failure” to evolve more complex life is most likely due to a non-emergence of the required proteins and signaling that allow multi-cellular organisms to appear. The long period of unicellular life on Earth was likely due to this. But eventually, multi-cellularity did arise, and its explosive radiation in forms is due to enhanced reproduction. Global catastrophes have stressed populations, resulting in mass extinctions of species and genera, but the subsequent flowering of new forms once the catastrophic conditions ended.

          You come from a long line of survivors over 3.5 billion years. Many survival behaviors are innate, but others are learned from our culture. Most people accept those lessons and survive. Those that don’t, collect their Darwin Award and depart the gene pool.

  • Harold Shaw March 13, 2022, 16:50

    The risks posed by relf-replicating vehicles could be mitigated. The risks could even be exaggerated. Starting with one vehicle and using the high estimate of 200 billion systems, the Milky Way would be filled before the 39 generation. That doesn’t provide many steps to go from locomotion and eyes to locomotion, eyes and teeth.

    Start with 1 million vehicles and the number of generations is halved. Produce all 200 billion using the same technologically assumed with self-replication, with a final step of self-sterilization and the risk of berserkers emerging is eliminated. If self-replication is utilized in the home system, the economics are largely the same as distributing the cost among all systems in the galaxy. Even at 1 metric ton per vehicle, the host system will barely notice the cost in mass. Depending on the vehicle, the cost in mass could be less.

    I imagine some of the “genotype” could be stored outside of the vehicle on a signal from the home system, eliminating the possibility for mutation of those genes. The assumed technologies would allow for a parent factory that could lay 200 billion eggs that could only grow but never evolve.

  • Robin Datta March 14, 2022, 18:02

    Zero defects in output and perfect quality control catching 100% of the defects is a tall order even with a simpler output item and with a lot fewer of those output items. Even the narrowest of gates allowing pass-through of variant product items could be a setup for evolution.

    When dealing with output in the billions, any guarantee of perfect replication has to be taken cum grano salis. The first lungfish that clambered ashore would not recognize us.

  • Armando Gascon March 14, 2022, 18:11

    Perhaps self-replicating probes are impossible.
    They are certainly impossible now, maybe they will be also impossible for future civilizations.
    Same as you need a whole town to teach a child, you may need all the resources of a planet to build and send self-replicating probes, of I suppose a mechanical electronic kind.
    So the probe would need to find a suitable planet -dismiss all thought of lurkers among the ices in the far system- develop a civilization, exploit all the resources of the planet (oil, gas, coal, uranium) to send more self-replicating probes with a high chance of fails.
    Perhaps an AI like that is impossible in the first place.

  • Robin Datta March 14, 2022, 18:32

    “Why Fill a Galaxy with Self-Reproducing Probes?”
    It is built into the genes.

    Among the large molecules in the soup, those that associated with each other formed molecular machinery, and those machines that persistently replicated continued their lineages. Those that had defensive and offensive features were more likely to survive. And those with a tendency to geographic spread dominated the scene, especially if they had the other two features.

    When the molecular machinery formed organisms, these features became biological imperatives. Species tend to spread till they come upon a limit. They then try to defeat that limit. Humans have been good at this, but light-years, gravity wells, cosmic rays, and the waterless and airless extreme desert pose challenges like none before.

  • Adam Crowl March 14, 2022, 21:34

    Hi Paul & Alex Tolley
    When I think of vNM’s (using Chris Boyce’s acronym from 1979) and their spread across the Galaxy, I think of quorum sensing in bacteria – if they detect each other nearby, they can stop or slow their reproducing. This would be especially needed if they have a finite range when travelling between stars. For example, if 10-100 light-years was the maximum range per generation, and the Galactic Core is avoided for some reason (eg. mini-Quasar bursts) then the self-reproduction spread would eventually turn into two fronts or waves that wrap around the Galaxy. Instead of the usual doubling time of 39 generations, some 1,500-15,000 generations traveling a distance of over 150,000 light-years are required to envelope the Galaxy. Depending on propulsion assumptions, 150,000 to 150 million years. Still lightning quick in Galactic terms, but on a truly evolutionary scale in biological terms.

    But there’s an implicit assumption that needs exploring – that all off-spring survive their journeys. What if a finite death-rate is assumed? What does a Galactic expansion look like then? Will there be dead-zones? What if the vNM’s need a positive arrival verification before proceeding further? I can imagine regions avoided by more risk-averse vNM strategies.

    Of course all it takes is one species to violate our assumptions and the Galaxy is full of mad beer-can making self-reproducing factories or some such silliness.

    • Alex Tolley March 15, 2022, 9:53

      Instead of the usual doubling time of 39 generations, some 1,500-15,000 generations traveling a distance of over 150,000 light-years are required to envelope the Galaxy.

      I am not clear why avoiding the galactic bulge results in such a prolonged increase in the number of generations. Migrating around the arms cannot be that much harder. [I can’t find it, but there was a CD post on this type of migration and assuming stellar movement to aid dispersion.]

      As regards “quorum sensing” between VN machines, I have alluded to that as an answer to teh Fermi question, if the motivation is to seed sterile worlds to create biospheres. In my example, if the seed “takes” then a probe will not revisit that system and look elsewhere.

      You raise an interesting point about modeling reproduction and death/mortality, rather than the usual assumption of bacterial growth and replication. The bacteria model of endless replication and now death [from phages] seems the appropriate model for an almost empty galaxy. But if conditions are hard enough, mortality needs to be taken into account. Lengthened doubling times would have been a huge factor in colonization times. If high enough, the replication front would be very patchy, with possible zones behind the front being absent of living probes. Percolation models like forest fires might be the appropriate model here, as they might be if the biosphere worlds prevented visits.

      While we cannot rule out evolution, it should be borne in mind that we can devise far more reliable information copying than DNA replication. It is why bitrot is so slow in hard drives. Checksums ensure copy integrity far beyond that of DNA and can ensure that there are no working codes that are mutated. But even so, the vast number of DNA mutations are either neutral or degrading and lead to reduced fitness or death. The likelihood of any probes chancing on improved fitness by information mutation is extremely low, especially given how few replications there are before the galaxy fills with probes (or each system is visited). Think how slow large animal evolution occurs even with reproduction happening every year. Speciation can be rapid if the information is naturally variable as it is in sexual species with copy errors and gene duplication and small founder populations are isolated from the main population. If they are not, the Hardy-Weinberg law operates to force the population towards the mean dispersion of alleles and reduced speciation. Probes are more like asexual species that must replicate perfectly, or most likely die due to a copy error. Bottom line is that I would think probe evolution is as unlikely as the much-feared “robot revolution” of pulp science fiction.

      • Alex Tolley March 15, 2022, 12:01

        Let me add a caveat.

        If it turns out that the only way to create robust, self-replicating machines, is to make them more like biological life, then they may be forced to allow errors and remain robust. Indeed “errors” may even be important (Neurons in the brain appear to have many small differences, and this may be required to provide the variety of responses needed for intelligence.) Our cells contain self-destruct mechanisms to allow for errors, although cancers occur when these fail. Telomere shortening ensures that cell replication is limited (Hayflick limit) again, except in cancer cells. Complex life has built-in lots of processes to handle errors, as well as mechanisms to ensure successful development despite small errors. It should turn out that to make self-replicating probes work, similar errors and corrective processes are needed, then evolution could proceed in such probes. Imagine if replication was akin to sexual, requiring 2 or more probe information systems to be merged, rather than just one as in asexual reproduction.

        As we don’t know what the motives of our descendants might be, let alone that of various ETs, while I would be loathed to release such probes into the galaxy based on the precautionary principle, I cannot say the same for these others.

        While I am of the belief that long-lived ET civilizations will likely be non-biological, I would not like to think that the galaxy has become an ecosystem of machines, both predator and prey, and even berserkers exist as apex predators.

  • wdk March 17, 2022, 12:00

    It was a first impulse to try to summarize this discussion about VNMs saturating themselves across the galaxy. But on reflection it seemed that shifting aim to the issue of focus; i.e., how self-reproducing machines would be or were expected to be used.

    My memory of these things is faulty, but I believe my introduction to the von Neumann machine idea was from 1950s article by Isaac Azimov or another popularizer, telling about how von Neumann proposed such devices for terraforming ( yet to be coined) one of the Galilean moons, probably Ganymede. I don’t think terraforming the whole galaxy was mentioned at the time. Nor that possibly the use of the reshaping cosmos for artificial intelligence would be the main goal – or focus.

    In the context of Fermi and von Neumann, it would appear that Fermi posed the problem of “Where is everybody?” and someone (maybe Fermi himself) retorted that if any civilization had arisen to the level of launching a self-replicating machine fleet, the galaxy should have been reworked by now – or maybe several times.

    So already we see two different focuses or foci for the idea: terraforming the solar system or delineating the capabilities of LGMs in the cosmos.

    By now, at any rate, the galactic application appears to be the focus. Maybe it always was, or stood off-stage, but I still have trouble picturing Fermi and von Neumann coming up with that analysis in pursuit of “Where is everybody?” even if it was over a lunch break in the early 1950s,

    To illustrate, it was not Arthur C. Clarke’s “Space Odyssey” but the sequel, “Space Odyssey 2010” , that employed a von Neumann machine mechanism to configure Jupiter. I don’t think it was called out as such, at least, not in the screen version. But in application it appeared to
    be faithful to the notion.

    Does anyone else have any recollection of how this concept originated or evolved?

  • wdk March 18, 2022, 19:23

    Thanks, A.T.
    That is quite a diagram! First time I ever saw such a database.

    Trying to imagine what that does to activities like forensic debate teams. At the very least, it shows a chronology of topics or ideas. But one can imagine such charts being leveraged further. E.g., prevailing definitions of all manners of concepts: social, political, technical… One could watch language and constructs morph. As evidently this one did.
    And I can think of examples I would like to pursue…Though not necessarily related to this topic. It might be possible to show that solution to historic (xyz) questions might be in terms that decades ago in terms of definitions extant then did not exist, question or answer.

    But our discussions here on Centauri-dreams often rove into such realms. There might be more opportunities to examine issues or concepts with such analytical devices.

    Reflecting on the past for von Neumann machines, a conjecture about the future: What if blockchains, cryptocurrency and energy and entropy are thrown into the self replicating machine notion? Maybe they already have…

    • Alex Tolley March 19, 2022, 11:37

      I am sure you must have seen similar things like the frequency of baby names over time. Since the data is now collated by Google and freely available, one can answer questions like why is this baby name common at this point in time, and with some knowledge find a celebrity or film star whose rise to fame is coincident with the popularity of that name.

      You may remember that Amazon once used to extract low probability phrases from books. Sadly it no longer does now that books are just a small part of its business. Use of this approach is used to determine the authorial provenance of a piece of text, most notably who wrote the plays attributed to Shakespeare.

      You can have endless fun selecting words and phrases, and displaying them in n-grams to gain some insight into the timing of usage.

  • wdk March 22, 2022, 19:54

    Coincidence, sentience, zero defects and von Neumann machines…
    What does link it all together? This past weekend the WSJ Review section had two articles on page C4Ș
    1. “Correcting Our Errors about Errors” by Frank Wilczek.
    2. “What Can Animals Tell Us about Emotions” by David J. Anderson.

    Unlikely that they were aware of our commentary on this Centauri-Dreams article, but both seem to address similar lines of thought – or mechanisms – or probabilistic behavior… – Er, check the code dump.

    Wilczek addressed Von Neumann and his machines. He argued that the statistical mechanics development behind vNM was “short-circuited” by the development of solid state semi-conductor technology – and hence our understanding of biological neural circuitry was set back many years. But ” a lot of progress has been made since 1956. The internet is designed to work around nodes that malfunction or go offline…. Von Neumann’s concern with unreliability fits within his vision of self replicating machines… would need to tap into an unpredictable, unreliable environment for their building material…. terraforming of planets…”

    Then, on the other hand, the second article examines whether presumed emotional responses of animals are reflexive or the same as we experience. That depends very much on whether we can prove there is any sentience in the animals, using crude criteria such as whether they identify themselves when looking in the mirror ( Have to wonder if Dr. Oliver Sacks had addressed that one with any of his unusual human patient case studies).

    But we were talking about coincidences like human sentience on a 4.5 billion year old globe with a moon that in this epoch does an excellent job of fully occulting the sun, an arrangement which, if planned went to a lot of trouble to provide a surveyor’s measure for the geometers of antiquity. And if they were, were they sure that we would have any sentience when we arrived on the scene?

    Then, on the other hand – or perhaps the subconscious – if live and sentience is rare, then what does the universe do in the intervals between its local planet-based emergence(s)? Does it exist? I guess it
    does. Because it would be hard to think up at the starting gate of

    If I had a little more time, I would get back to these questions and not leave things hanging on a precipice. But I have to finish writing up my taxes…

  • ljk March 24, 2022, 18:12

    Scientists propose sending tiny lifeforms to neighboring solar systems

    The interstellar travel plan involves mini bears, flying wafer chips, and bouncing laser beams off a sail.


  • ljk April 6, 2022, 11:41


    [Submitted on 15 Nov 2021]

    Research Programs Arising from ‘Oumuamua Considered as an Alien Craft

    Martin Elvis

    The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artifact designed to operate for 10^5 – 10^6 yr are also considerable.

    All three areas generate research programs going forward. The uncontrolled case could be either “anonymous METI” (messaging extraterrestrial intelligence) or “inadvertent METI”. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided.

    The “controlled” case has more strikes against it than the “uncontrolled” case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies.

    Some of these, e.g., intercept missions for new interstellar objects, are concepts being developed, and will be of value whatever these objects turn out to be.

    Overall, these considerations show that a many pronged, targeted, research program can be built around the hypothesis that ‘Oumuamua is an alien craft. The considerations presented here can also be applied to other interstellar visitors, as well as to general discussions of interstellar travel.

    Comments: 17 pages, 1 figure, 1 table. International Journal of Astrobiology, in press

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Popular Physics (physics.pop-ph)

    Cite as: arXiv:2111.07895 [astro-ph.EP]
    (or arXiv:2111.07895v1 [astro-ph.EP] for this version)


    Submission history

    From: Martin Elvis [view email]
    [v1] Mon, 15 Nov 2021 16:46:03 UTC (488 KB)


  • ljk April 6, 2022, 11:44


    [Submitted on 20 Oct 2021 (v1), last revised 12 Mar 2022 (this version, v3)]

    On the Possibility of an Artificial Origin for `Oumuamua

    Abraham Loeb (Harvard)

    The first large interstellar object discovered near Earth, `Oumuamua, showed half a dozen anomalies relative to comets or asteroids in the Solar system.

    All natural-origin interpretations of the Oumuamua anomalies contemplated objects of a type never-seen-before, such as: a porous cloud of dust particles, a tidal disruption fragment or exotic icebergs made of pure hydrogen or pure nitrogen.

    Each of these natural-origin models has major quantitative shortcomings, and so the possibility of an artificial origin for `Oumuamua must be considered.

    The Galileo Project aims to collect new data that will identify the nature of `Oumuamua-like objects in the coming years.

    Comments: 17 pages, 8 figures, accepted for publication as a review paper in the journal Astrobiology

    Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Physics and Society (physics.soc-ph)

    Cite as: arXiv:2110.15213 [physics.pop-ph]
    (or arXiv:2110.15213v3 [physics.pop-ph] for this version)


    Submission history

    From: Avi Loeb [view email]
    [v1] Wed, 20 Oct 2021 09:56:28 UTC (924 KB)
    [v2] Tue, 1 Mar 2022 23:48:39 UTC (852 KB)
    [v3] Sat, 12 Mar 2022 22:49:24 UTC (852 KB)


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