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A Nod to ‘Stapledon Thinking’

Taking a long walk in the early morning hours (and I do mean ‘early,’ as I usually walk around 4 AM – Orion is gorgeously high in the sky this time of year in the northern hemisphere), I found myself musing on terminologies. The case in point: The Fermi Paradox. Using that phrase, the issue becomes starkly framed. If there are other civilizations in the galaxy, why don’t we have evidence for them? Much ink, both physical and digital, has been spilled over the issue, but I will argue that we should soften the term ‘paradox.’ I prefer to call the ‘where are they’ formulation the Fermi Question.

I prefer ‘question’ rather than ‘paradox’ because I don’t think we have enough data to declare what we do or do not see about other civilizations a paradox. A paradox is a seemingly self-contradictory statement that demands explanation. But is anything actually demanded here? There are too many imponderables in this case to even frame the contradiction. How can we have a paradox when we are fully aware of our own limitations at data gathering, to the point that we have no consensus on what or where to target in our searches? Possibilities for technosignatures abound but which are the most likely to be productive? Should we truly be surprised that we do not see a clear signature of another civilization?

We make our best choices based on the technologies we have. On the galactic scale, that means looking for anomalies that might flag a widespread Kardashev Type III civilization. We know that such a civilization’s technologies would far surpass our own and its communications might involve methods – the use of gravitational waves, for example – that are far beyond our capabilities to detect. The Fermi Question tells us about our limitations but doesn’t point to a genuine conundrum. We should also keep in mind that although all the debates on this matter have elevated its status, the statement Fermi made could be considered relatively light lunch-time banter.

On the scale of the Solar System, it would be better to say that we do indeed lack evidence of extraterrestrial visitation, but also that we really have only begun to look for it. A lengthy book could be written on where or why another civilization might plant a ‘lurker’ probe in our Solar System, conceivably one that could have arrived millions of years ago and could even today be quietly returning data on what it sees. We have yet to examine our own Moon in the kind of detail now available to us through the Lunar Reconnaissance Orbiter, and as my friend Jim Benford never tires of pointing out, we know almost nothing about other nearby objects such as Earth’s co-orbitals. Until we sift through actual data, we’d better use caution about these matters.

So while I don’t think it rises to the level of a paradox, the Fermi Question is an incentive to continue searching for data whose anomalous nature may be useful. And while we do this, working the borders between SETI and philosophy seems inevitable. Because when we discuss extraterrestrial civilizations, we’re talking about behaviors that can be detected, without having the slightest notion of what those behaviors might be. What we call ‘human nature’ is hard enough to pin down, but how truly alien cultures would address the issues in their realm is purely imaginative conjecture.

I’m reminded of something Milan Ćirković said in The Great Silence: Science and Philosophy of Fermi’s Paradox (Oxford University Press, 2018):

As we learn more, the shore of the ‘ocean of unknown’ lengthens, to paraphrase Newton’s famous sentence and, while we may imagine (on some highly abstract level) that it will eventually contract, this era is not yet in sight.

Thus, we have another prediction: there will be many new explanatory hypotheses for Fermi’s paradox in the near future, as the astrobiological revolution progresses and exploratory engineering goes farther and farther.

Pondering Smaller Stars

That said, I note with interest a paper from Jacob Haqq-Misra (Blue Marble Space Institute of Science, Seattle) and Thomas Fauchez (American University) that makes the case for low-mass stars as the logical venue for expanding civilizations. If we wonder where alien civilizations are, the question might be resolved by the idea that if such cultures expanded into the cosmos, they would select K- or M-dwarf stars as their destinations. Here we’re squarely up against issues of philosophy and sociology, because we’re asking about what another species would consider its goals.

But let’s go with this, because the authors are perfectly aware of all that we don’t know, and also aware of the need for shaping our questions through broad theorizing.

Why smaller stars? Here we’re dealing with an interesting hypothesis, that G-class stars are the most likely place for life to develop in the first place. Haqq-Misra has written about this before (as have a number of other scientists referenced in the paper), and here makes the statement “We first assume that technological civilizations only arise on habitable planets orbiting G-dwarf stars (with ∼10 Gyr main sequence lifetimes) because either biogenesis or complex life is more favored in such systems.” And the idea is that stars like our Sun have lifetimes far shorter than the trillions of years available to M-dwarfs or the 17 to 70 billion years for K-dwarfs.

That’s a big assumption, but it leads to a conjectured motivation: A civilization will choose to maximize its longevity, just as an individual human will try to stay alive as long as possible. A culture that manages to become long-lived will have to cope with the eventual loss of its home G-class star and will look for longer-lived destinations that can serve as more lasting home worlds. And while I’ve mentioned M-dwarfs, the K-class seems to hit the sweet spot, so that the authors title a section of their paper “The K-dwarf Galactic Club.”

K-dwarfs are plentiful compared to G-class stars like the Sun, accounting for about 13 percent of the galactic stellar inventory (G-class stars comprise about 6%). M-dwarfs are the most common star, at about 73 percent, according to the authors’ figures. We’ve already seen, though, that K-dwarfs offer significantly longer lifespans than G-class stars, and because of their size and the nature of habitable orbits, they offer possible living planets without tidal lock.

If the authors are correct that life is more likely to arise around G-dwarfs, then it could be said that a K-class star offers a living experience closer to that of the homeworld for any civilization that chooses to migrate to it. This is because the spectra of these stars are much closer to G-star spectra than to M-dwarfs. With M-dwarfs, as well, we have to contend with higher stellar activity than on the more quiescent K-dwarfs. Planetary environments are thus much closer to G-dwarf norms than around M-dwarfs.

The problem of what we might call exo-sociology looms large in this discussion, and it’s one the authors frankly acknowledge. Whether or not life exists anywhere else remains an open question, and we have no knowledge of what extraterrestrial civilizations, if out there, would consider important or desirable as guides to their activity. But if we’re asking philosophical questions, we can ponder what any living intelligence would consider its primary goal, as the authors do in this excerpt from their paper:

Newman & Sagan (1981) performed a detailed mathematical analysis of population diffusion in the galaxy and concluded that only long-lived civilizations could have established a Galactic Club; however, such a possibility was excluded because the authors “believe that their motivations for colonization may have altered utterly.” Although it remains possible that long-lived technological civilizations do not expand, it also remains possible that such civilizations pursue galactic settlement in order to ensure their longevity. The numerical simulations by Carroll-Nellenback et al. (2019) found solutions where “our current circumstances are consistent with an otherwise settled, steady-state galaxy.”

Image: M31, the Andromeda Galaxy. What might drive the expansion of a civilization outward from its native system, and how can we, with no knowledge of other civilizations, plausibly come up with motivations for such activity? Credit & Copyright: Robert Gendler.

We have a scenario, then, of long-lived civilizations preferentially expanding to particular categories of stars to ensure the survival of their species, but otherwise not expanding exponentially into the galaxy. Such a scenario would fit with what we see, being a level of activity that would not necessarily announce itself through contact with other civilizations. Cultures like these would be content to mind their own business as long as their survival could be ensured, but we might or might not expect them to actively probe stellar systems as relatively short lived as those around G-class stars. We should look in our own system, say the authors, but a failure to find evidence of extraterrestrial travelers might simply reflect a preference to visit other types of star.

This makes identifying these cultures a tricky matter indeed:

We can exclude scenarios in which all G-dwarf stars would have been settled by now, but the possibility remains open that a Galactic Club exists across all K-dwarf or M-dwarf stars. The search for technosignatures in low-mass systems provides one way to constrain the presence of such a Galactic Club (e.g., Lingam & Loeb 2021; Socas-Navarro et al. 2021; Wright et al. 2022; Haqq-Misra et al. 2022). Existing searches to-date have placed some limits on radio transmissions (e.g., Harp et al. 2016; Enriquez et al. 2017; Price et al. 2020; Zhang et al. 2020) and optical signals (e.g., Howard et al. 2007; Tellis & Marcy 2015; Schuetz et al. 2016) that might be associated with technological activity, but such limits can only weakly constrain the Galactic Club hypothesis. Further research into understanding the breadth of possibilities for detecting extraterrestrial technology will become increasingly important as observing facilities become more adept at characterizing terrestrial planets in low-mass exoplanetary systems.

Thus the value of the Fermi Question at highlighting the staggering depth of our ignorance about what is actually out there. I enjoy creative solutions to conjectural problems and am all for applying what I might call ‘Stapledon thinking’ (after the brilliant British philosopher and science fiction writer) as forays into the darkness. We can expect many more ‘solutions’ to the Fermi Question as our capabilities increase. The outcome we can hope for is that one of these days a present or pending astronomical instrument will deliver data on a phenomenon that will resolve itself into a true technosignature (or even an attempt to communicate). Until then, these stunningly interesting questions will drive thinking both philosophic and scientific.

The paper is Haqq-Misra & Fauchez, “Galactic settlement of low-mass stars as a resolution to the Fermi paradox,” accepted at the Astronomical Journal and available as a preprint. Be aware as well of Michaël Gillon, Artem Burdanov and Jason Wright’s paper “Search for an Alien Message to a Nearby Star,” Astronomical Journal Vol. 164, No. 5 (27 October 2022). Abstract. And for all things Fermi, see Milan Ćirković, The Great Silence: Science and Philosophy of Fermi’s Paradox (Oxford University Press, 2018).

{ 43 comments… add one }
  • Alex Tolley October 28, 2022, 10:16

    When speculating about civilizations elsewhere and thinking about where they might migrate to, we get caught up in our own terrestrial history of migration. Cpmp[arable questions might be: “Do we migrate/retire to another [larger] continent, or would an island be better, and if so, is there a sweet spot size to migrate to?”.

    Yet even now some people are designing floating oceanic cities, that would be like smaller city-states of ancient Greece, or contemporary Singapore. IOW, mega-engineering, even of our capabilities, enters the terrestrial migration question.

    Is it possible ETI has stellar engineering capabilities? “Starlifting” to remove a star’s martial to reduce its mass and extend its lifetime is a known idea. But what about going further? What about carving up an F or G-type star and constructing a binary or multiple-star system? With a civilizational lifespan of billions of years, there would be plenty of time to build such systems, and even add planets of optimal design and orbital position. Could this be detectable using existing telescopes and characterizing systems looking for a statistically unlikely star and planetary arrangements compared to models?

    Could supernovae be not just natural but artificially induced to provide the material for star and planet formation? The opposite of carving up stars, but rather combining stars and then detonating them.

    [As an aside, I am skeptical about the engineering of solutions like Marioshka brains because they create an infrastructure that makes physical migration very difficult. OTOH, a digital civilization could migrate by beaming its intelligences to a new, prepared location, avoiding the need for starships, just slow-moving “planet builders” eons in advance to prepare the destination[s]. ]

    Our metaphorical ant colony [intelligence] living near a road might be aware that the road looks very different from the landscape around it – flat, with smooth surfaces, and without rocks or plant material on, or embedded in, its surface. The surface would be hard and the worker ants cannot bury into it, and food and predators are notably absent.
    As we build ever better models of natural star and planet formation, we could create statistically expected systems. Today we might tweak our model to try to fit the observations, but possibly we should not and see if the observations suggest an abundance of artificial systems that look more designed than natural.

    KIII civilizations might be like the Abrahamic religions with a G*d who builds a planet in 7 days, although this may require more like 0.7 bn years.

    • Geoffrey Hillend October 28, 2022, 17:57

      Interesting. As I was reading this paper an idea came to me about taking “Stapledon Thinking” further and Alex Tolley has already done it. If one can make designer spacetimes with an Alcubierre Warp drive, a fleet of those could easily push planets out of their orbits and they could make designer planets. A Galactic Club might decide what planet and solar system a civilization has to move which has had to leave their home world because it moved of the main sequence hydrogen burning and into the red giant phase. A solar system which a G class star, outer Gas giants and inner rocky planets and Earth sized exoplanet which is not in the life belt might be moved it into the life belt making a designer solar system. Gravity and anti-gravity technology could increase the spin of the planet without a Moon. Heck if you want a Moon for tidal forces and ocean tides they could add that too. Terraforming and engineering K class exoplanets would be easy for FTL civilizations.

      At some point, the G class star turned into a white dwarf so even if an advanced FTL civilization can move their home world much further away into the outer solar system during the red giant phase life belt which would be the easiest solution physically since one does not need to find a new world(s). The problem there is after the red giant become a planetary nebula, the star sheds its’ outer layers of gas and becomes a white dwarf. There is no habitable life belt around a white dwarf star due to low light and high ultra violet radiation. The ET civilization would have to move to another solar system and so would we in the distant future.

      The Fermi Paradox becomes a not paradox if we consider it is limited to today’s technology and radio signals with a maximum velocity of light, but not the FTL tech of tomorrow and very advanced civilizations.

    • torque_xtr October 31, 2022, 19:43

      Creating artificial supernovas looks nuch easier than star-carving: just tweaking orbits until stars collide. No need for operations in stellar-interior environment or to collect
      spilled plasma tails into new bodies.

      I always thought that migration opened up by iterative interstellar colonization could answer at least some of the Question. Mobile population seeks better home and it ventures far, driven by subtle (to us) differences between places in the Galaxy, or even becomes interstellar-based, like Ousters from Hyperion. Those who choose not to radiate from their (current) homeworlds become non-expansionist. Neither are readily detectable, first because none of them are close (the “we’re in the outback” argument), second because they leave few signatures. Ousters, too, will migrate towards higher energy/matter density if it matters to them. The population density per million cubic parsec may differ much more than human population density here on Earth. But if this is true, it’s better to look for the cities.

      Now the Outback argument seems even more solid to me. We see only wilderness around Sol, standing on grass and breathing pristine air. Not a single whiff of bonfire smoke or distant highway rumble in the wind, much less concrete paving right beneath our feet or orange city glow lighting our night skies.

    • torque_xtr November 2, 2022, 16:09

      I was writing previous comment musing while trying to get asleep, but it stuck in my mind and now I see it can be said much more articulately.

      If non-uniform Galactic population density hypothesis is correct, the observability of technosignatures will vary about as much as population density contrasts. If we were in populated areas, we would see technosignatures as clearly as standing on a highway tarmac, seeing and feeling it by eyes and feet and perceiving it’s unnaturalness. Signatures would be ubiquitous and alive. Paleolithic human would surely see the difference immediately, despite being ten kiloyears behind in knowledge. No doubt all mammals and many birds perceive it too, despite even much greater gaps in understanding. Instead, the observable cosmos is so natural that we haven’t recognized any slightest unnaturalness in it even by now.

      In the forest, signatures will be sparse, if any, long-defunct and hugely less evident. They still could be found and identified with some effort depending on how pristine the area is. But compare this to the cities where technosignatures just fill the whole eyesight, instead of unconspiciously lurking in the grass! Some litter here and there, quite much in suburban forests, tens of kilometers apart in the jungle. Distant faint skyglow on the horizon from the cities, while most of the wilderness still does not have obvious light pollution.

      There’s a point that city-class technosignatures would be far beyound imagination of forest dwellers, and we can’t imagine what is like to live in a galactic city. If instead we lived our whole lives in it, we wouldn’t guess it is not natural. But I bet we would, even if the gap between us and others is like between earliest primates and us. And that’s at least tens of megayears – less than it takes for thermonuclear propulsion-based iterative colonization of the Galaxy.

  • Erik Landahl October 28, 2022, 14:04

    Paul’s article champions a necessary curiosity regarding the aptly renamed “Fermi Question.” Alex’s comment does the same regarding the requirement to understand potential alien engineering efforts as antecedent to detecting alien technosignatures, Both gentlemen pump some new life into their subjects, and hopefully, both will produce another article regarding the same.

    • Paul Gilster October 28, 2022, 14:10

      Why thank you, Erik. And yes, more to come.

  • Alex Tolley October 28, 2022, 15:44

    I think I first read the term “Fermi Question” rather than “Fermi Paradox” in Stephen Baxter’s novels, possibly the Manifold trilogy, around the turn of the century.

    As there are so many explanations for the absence of alien evidence that it seems unnecessary to continue using “paradox”, substituting “question” seems far more appropriate. Didn’t Fermi pose the issue of the lack of evidence for aliens as a question rather than suggesting it was a paradox?

    A google engram of the 2 terms shows some correlation, with “Paradox” being used about 5x as frequently:

    N-gram for fermi Paradox, fermi Question

  • ljk October 28, 2022, 16:53

    To avoid any hoary and obvious cultural jokes and at the risk of sounding like a plot point from Star Trek, it could simply be that we are a young society and species and the more sophisticated intelligences that can interstellar travel and communicate agree among themselves to avoid us until and if we grow up enough to handle contact.

    The other possibilities are indeed that we are too different and not interesting enough to be contacted by certain alien life. Or that we are not advanced enough to be noticed by other species in other parts of the galaxy. Remember our electromagnetic bubble is only about 200 light years across and most of our signals are untargeted and weak. As for being able to detect that there is organic life on Earth, that may not be enough to get an ETI to come visit us or send signals.

    Again I invite folks to review this site to get different taste of things:


  • Christian G October 28, 2022, 17:12

    Thank you, Paul. As I’ve said before, all the Fermi “Paradox” really says is that certain assumption s about ETI do not give conclusions that match our observations. Alex’s comment reiterates something I’ve seen mentioned here before, that a sufficiently widespread technosignature is indistinguishable from natural phenomena. People are eager to find explanations for what they see or don’t see, and a great deal of discussion of the possibilities of ETI seem to be, as Sherlock Holmes put it, theorizing in advance of the data. A little humility in front of a universes worth of unknown unknowns might keep us form that mistake.

  • Harold Shaw October 28, 2022, 18:23

    I would map my biggest SETI pet peeve to the term Fermi Paradox; the demand that any solution must filter the entire probability space for space faring people. Many filters works, perhaps even better. I am all for using a different term. I have been using Fermi Puzzle because it invites a multitude of solutions.

    We understand chemistry and evolution well enough to apply generalizing first principles to Life. However those principles can’t be used to predict the existence, traits and lifestyle footprint of the platypus, elephant, and ant. Or the lack of unicorns and fairies. We aren’t looking the platonic ideal of alien people, we are looking for whomever ending being a space faring people.

    I am not recommending we abandon the search for first principles of space faring evolution. Imo, the insistence that space faring people will be nothing like us or beyond our imagination can’t be right.

  • Harold Shaw October 28, 2022, 18:41

    I don’t think it far fetched to think a K3 lifestyle would value wild interstellar spaces where Life could emerge more than population increase. We don’t have to prove every K3 people would feel the same. Rather, I think we should assume a spectrum of K3 lifestyle footprints on first principle.

  • Michael Sloboda October 28, 2022, 22:20

    Exo-sociology starts from human sociology. On Planet Earth now, birthrates have fallen below replacement level in one prosperous country after another, despite political, religious and social differences. In Japan, adult diapers outsell baby diapers. As other nations increase the GCP, global population will peak, maybe in 40 years, and start to decline.
    In the 1930s, the question was “Guns or butter?” In the 2030s, “Guns (and space exploration) or wheelchairs?”
    In 400 years, there could be ample room on Planet Earth for everyone without any need for space colonies. Time will tell.

    • Alex Tolley October 29, 2022, 11:24

      The predictions of population often are related to economic development, that is as child mortality falls, social safety nets increase, and economic opportunities increase, the need for many children to survive and support you, declines. But supposing this is true and economic development must increase to encourage this situation, we have a problem in that we cannot keep increasing the planet’s creation of manufactures without destroying the planet itself. (At least not with today’s low level of recycling.) OTOH, as the climate warms and crop production falls, we may see an increase in the mortality rate (diseases reappearing and untreated as well) which will reduce the population, but with that decline, a reduced ability to invent and innovate, and with it a stagnating or declining global economy.

      The 2 largest anglo nations, the US and UK, both seem to be making the same “more guns, fewer wheelchairs” decisions rather than the reverse.EU nations that resisted that stance are now threatened by disruption from outside. Authoritarian nations, from Singapore to Hungary are encouraging higher childbirth rates. India has overtaken China as the most populous nation.

      Absent global conflict, and reactionary governments, we could win the race o create a prosperous, livable plane that doesn’t look like Trantor or Coruscant. But the odds of achieving this seem to be getting longer and a major, dystopic upheaval occurring instead.

  • Jer October 29, 2022, 0:33

    Thought provoking article.
    As seemingly pertinent and inspiring a search and/or discussion of possible co-existing civilizations might be, I might inquire about origins and precedents. When we consider what systems, configurations, and stages of stellar development that may best suit some form of complex and socially-reinforcing organic conglomerations, which some may refer to as Life, I think of what could have been. Using our understanding and extensive research into galactic and universal development, I would wonder how many life opportunities could there have ever been and when/ where was the first opportunity for likely complex/ sentient -though not necessarily intelligent or space-faring- Life? As one would ask when and where were the first proto-humans – when/ where was the first habitable place and why? From there we may draw paths or splits or concurrent starts or dislocated scatter plots. I picture a time where the universe was much smaller but the possibility of life could still exist in some areas more than others. Perhaps a density/ grouping of early possibilities suggests the likelihood of more complex civilizations able to detect neighbours earlier. Perhaps the Fermi Surmise – not quite a conjecture, but typically a starting point assuming truth but allowing much opportunity to refine and discuss; also a bit more affirming than a speculation or ‘feeling’. Cheers.

  • Adam J Crowl October 29, 2022, 3:12

    Hi Paul
    Always happy to hear Stapledon’s name bandied about. Geoffrey Hillend’s suggestion of designer Solar Systems makes me think of Stapledon’t rings of artificial worlds around lone stars in the advanced stages of Galactic society. But to do one better, for really advanced Galactic Society, why not the rings of planets posited by Sean Raymond in his Million Earth Solar System? Orbiting an Super Massive Black Hole (SMBH), such a Sidereal Engineering structure would be an obvious Technosignature, though I’m unsure of its observables. Raymond’s SMBH has a relatively low luminosity, so that could be one.

    Combined with the prospect of an Industrialised SMBH (as discussed here on Crowlspace) and the numbers of planets orbiting the SMBH can swell into a huge Ecospace, especially if there’s illumination of gas clouds by directed beams to support in-space ecosystems.

    More complicated many-body periodic orbits are possible, forming vast clouds of gyrating planets where the planets keep each other together in a gravitational embrace, their collectice centre of mass orbiting the SMBH.

    There’s no telling the long-term aesthetics of Kardashev-III style Civilizations. But there may be Universals of Beauty.

  • Mike Serfas October 29, 2022, 11:03

    I don’t think we should count out Sun-like stars just yet. Based on https://www.nature.com/articles/s41467-022-33497-1 I’d speculate perhaps even modern humans can construct a probe of plasmonic high-energy carbides capable of “landing” on a sunspot. The probe would need to interact with the solar magnetic field to levitate — perhaps an advanced civilization could adapt these interactions to allow the probe to function as a fusion reactor. The probe might synthesize needed elements in situ to self-replicate until its progeny cover the surface of its star.

    Given this network, a civilization might tame and harness the once-fickle flow of material outward from its star, directing plasma or other forms of energy to warm the outer planets of their system. At this point they would be nearing “Kardashev II”. With sufficient skill, even passing rogue planets might be connected to networks of “ball lightning” that span light years. (Solar-powered laser beaming is also possible, bu thermodynamic efficiency should favor a means by which heat rather than usable work is transported; also, we would see the lasers) Interstellar voyages would no longer be a trouble for such folk!

    But harnessing the power of a sun would not be parasitic, but symbiotic. If they can manipulate the magnetic fields of their star, and extract ever-increasing amounts of energy (“Kardashev II.I”, maybe?), they ought to be able to manipulate a type G star to be fully convective, despite its size, and give it some fraction of a class M lifespan, while preventing it from expanding and disrupting ancient historic landmarks such as their home planet.

    Is there a chance someone has already observed a galaxy home to many too-old Sun-sized stars that perhaps have a strong line of carbon in their atmospheres?

  • Greg Hullender October 29, 2022, 11:49

    It’s a paradox because the mediocrity principle (which states that there’s nothing special about Earth/humanity) implies that we shouldn’t be the first (or only) intelligent species. But the facts that a) Earth is untouched (no one colonized it in the past few billion years) and b) we see no signs of civilization elsewhere imply that we really are alone. That’s the paradox.

    Arguing that “maybe they prefer K-type stars” doesn’t work. Maybe some aliens prefer K-type stars, but to explain the paradox, all aliens–across the last few billion years would have to have felt that way. Ditto arguments like “maybe they don’t want to talk to us.” It’s not about us at all; it’s about what they could have done before we were even here.

    • Alex Tolley October 29, 2022, 17:06

      It is only a paradox if one accepts the Copernican principle concerning the evolution of technological ETI. There is no paradox if that assumption is discarded, or at the very least, reduced the probability of that happening to an extremely low level. ETI might emerge every few million years, briefly flower, then disappear, without achieving star flight or perhaps only visiting or colonizing a few nearby systems before the civilization ends. The low frequency of occurrence ensures that Earth would not have been visited or signs left of their presence, and that technological mega-structure artifacts will have decayed or been very sparsely located. The paradox only works if ETI is so common or distributed that we should be able to see them just by looking – i.e. what the Ufologists claim is actually the case.

  • Steve Muise October 29, 2022, 11:58

    As to the Fermi Question (I like this terminoloogy!):

    1) We’ve only been searching for 62 years, and we’ve been searching using equipment that would be hard-pressed to detect US over a relatively short distance.

    2) We think of a technical civilization as using radio, etc, but perhaps that level of technology is rarer than we think. It’s entirely possible that the nearest neighbors are marveling over their latest inovation: steam power.

    • Alex Tolley October 29, 2022, 16:57

      The problem is that in reality, ETI is likely to either be in the paleolithic or earlier or many millions of years ahead of us. For ETI to be at a stage of technology that is effectively contemporaneous with us (+/- a century) is so extremely unlikely that we can ignore it.

  • Peter Popov October 30, 2022, 2:41

    The average lifetime of a mammalian species is a few milion years on average. Our current civilization will likely survive much less. From that perspective, a star with a lifetime of a few billions of years offers an infinite amount of time for multiple civs to thrive, multiple times. Just like a star with a lifetime of hundreds of billions of years. If you have the resources to move from a G class to a K class star once, you will have the resources to do it many multiple times over and over again. So the stated reason why K class stars are more desirable target is preposterous. What if the aliens prefer sunshine? Why waste money to go to a cold and dim, red-coloured wasteland?

    If our current civs continuous to develop it will expand into the space around the solar system on a timescale of hundreds of years. Surely, after one billion year people could move to the outskirts of the Kuiper belt and enjoy a big red supergiant…

    • Alex Tolley October 31, 2022, 14:49

      And when it becomes a white dwarf? Interesting coincidence [?] that in a post about Stapledonian thinking, in this case, “Last and First Men”, you mention living in the outer system with the sun as a red giant. Isn’t that the situation with the 18th Men living on Neptune when the sun has gone RG?

      Asimov noted that interstellar travel to find a new home when the sun no longer is suitable is like run to another tree in a rain storm hoping that tree isn’t saturated and letting the water through. I’m surprised at that thinking as we know star formation is continuous as the Hubble and JWST pics of the “Pillars of Creation” have so beautifully illustrated.

      I agree with Astronist that thinking of civilizational longevity related to the billions, even trillions, of years that stars remain on the main sequence is ridiculous. I would argue that we needn’t be concerned about Earth becoming unlivable as the sun’s luminosity continues to increase. Humanity will have likely evolved into new species many times and either our lineage will expire (see Stephen Baxter’s “Evolution”), or we will have spread out into the universe long before then, hopefully bringing along samples of terrestrial biospheres along the way.

  • DCM October 30, 2022, 4:18

    Speculation will help prepare us but we won’t know till we find out.

  • tesh October 30, 2022, 5:23

    A number of drivers have been bandied about that could/would drive civs to expand:
    1. Resource
    2. Ensure survival (linked to 1 in many ways)
    3. Curiosity

    For me 3. is a non starter as curious individuals without resource will remain forever curious. 1 & 2 are linked in many ways and they could potentially drive an expansion effort that leads to a discernible/discoverable footprint in the sky but, and this is the point that a lot of people seem to ignore, why bother expanding. If your horizon is contracting, in terms of understanding the universe, why live in it – to face the perils and limitations therein? There are surely an infinite number of other universes that they could go to, physical or digital, where survival is no longer part of the equation and crack more stimulating. In particular, digital world offers infinity, survival forever, till the end of times and beyond.

    p.s. thank-you for the article Paul

  • Robin Datta October 30, 2022, 8:06

    The evidence for phenomena that could be called living, sentient and even intelligent (besides what is known on earth), still awaits discovery. That awaiting is dependent on the presumption that something will someday, somewhere be found. And with the further presumption of an abundance of such evidence “out there”, one may speak of a paradox.

    But of course the question ain’t settled yet. And the only way for it to be settled is the finding of evidence. Acceptable evidence can be quite catholic in this regard: technological artifacts composed of unusual isotopes of unusual alloys, for instance. Or elements from the Island of stability or the Continent of stability.

    Not finding evidence will not settle the matter: absence of evidence is not evidence of absence. And when we hear that the expansion of the universe will whisk away the more distant galaxies such that their remoteness and speed of recession prevents their light from ever reaching the earth, we will never know if they have intelligent life.

    The finer the comb we use, and the wider and longer we look without finding such evidence, the more remote the prospects become.

  • Harold Shaw October 30, 2022, 11:15

    The mediocrity/Copernican principles predict that no special laws of nature apply to Earth and are compatible with rare Earth hypotheses. Using poker as an analogy, every player (star system) is playing by the same rules and has access to a randomized deck. The mediocrity principles predicts Earth can’t deal from the bottom of the deck or hide cards up its sleeve. The conditions for space faring capable intelligence could be equivalent to being dealt a royal straight flush without contradicting the mediocrity or Copernican principles. Suggesting that rare Earth hypotheses are incompatible with either principle is wrong and unproductive.

    There are no good arguments for total colonization of every system being the default, average or mean result of a space faring people expanding into their galaxy. I would describe it as alchemy, a first principle untethered from observation.

    We can be certain that the space environment and Deep Time will select for fitness. We can be certain that the lifestyle and value profile of K3 people with be large and complex. A K3 civilization may be comprised of K1-K2 persons. Imo, we can also be certain that no self-aware people will spread to new environments for the purpose of preserving their species, since every new environment, especially artificial habitats, will select for unique fitness.

  • Astronist October 30, 2022, 19:55

    “I prefer ‘question’ rather than ‘paradox’ because I don’t think we have enough data to declare what we do or do not see about other civilizations a paradox.” – Thank you for this; I’ve been trying to get this message across for years.

    • DCM October 31, 2022, 3:34

      That’s right.

  • Astronist October 30, 2022, 20:06

    “A culture that manages to become long-lived will have to cope with the eventual loss of its home G-class star and will look for longer-lived destinations that can serve as more lasting home worlds.” – I disagree. A culture that manages to become long-lived will be by definition one that has spread widely enough that it regards a large number of stars as its home. It will have ceased to be a unitary civilisation, and will have become a population of related civilisations – recapitulating the original expansion of our species out of Africa to spread around the world. The lifetimes of main-sequence stars will not be a relevant factor when deciding where to expand to, because in all cases those lifetimes are vastly longer than the historical timescales on which travel and city-building decisions are made.

  • Michael C Fidler October 31, 2022, 2:23

    Large eyes for red to infrared wavelengths around K and M dwarfs seems to fit very well with the current unscientific alien visiting us now. Unscientific in the sense of our belief system and dogma that this cannot be and where are they?…
    Would you want to give your position away in a world where nuclear missiles can target you or wars are the norm? Where their own species is put in slavery or killed for no good reason? Where the highest expenditure of almost every country is for weapons and military? Where insane people can own guns???

    Tidal Lock is the most stable system for technological civilizations since bizarre weather would not be a problem like spinning worlds have. A nice pleasant land area near the day and night terminator…

    But we may have something much closer, the dwarf planet Haumea! This planet has a Clark Belt a bizarre shape and two large satellites and a four hour rotation period. Enough mass to have geothermal heating for oceans like Europa and Enceladus. A perfect place to watch our earthly wars from a safe distance…



    • Alex Tolley October 31, 2022, 15:14

      Where the highest expenditure of almost every country is for weapons and military?

      Even the US spends less on the military than on social services and welfare. Britain, with the largest military spending as a % of GDP in the EU, spends far less on the military than on social services and welfare. Hard to find such figures for all other countries, but the Philippines has a low 1% of military spending on GDP, similar to Japan, suggesting to me that social welfare is a greater recipient than the military.

      So while military spending is large overall, one cannot claim that in most countries the highest expenditure is on the military. It can get larger during wartime, and I think I have figures in my library on Germany’s hugely increased military spending in the 1930s after the Nazis came to power with the intention of using their military to acquire lebensraum.

      • Michael C Fidler October 31, 2022, 21:13

        Thanks for the info but Japan and the Philippines are both protected from lebensraum by the U.S. military. We are the police for most of the world and at what cost, alien species may look at us from the perspective of the Whole Earth and see what we are doing to it. Two hundred years ago our expenditures on wars and the material to wage it was small since the industrial revolution more and more money and hard to get materials became a big business to wage war. What would we do if we went to Proxima Centauri and found a similar situation? Would we land in the middle of their wars and say stop or observe and see what it is doing and why. Granted war and aggression is part of us but anyone from somewhere else would be very careful to directly interfere at such a critical time in a planets and a civilizations history because the consequences could be horrific…

        Just how much of global warming is because of military industrial complex expenditures and the wars that are being fought since the industrial revolution, WWII, Vietnam, the middle east and Ukraine.

        Early onset of industrial-era warming across the oceans and continents.

        • Alex Tolley November 1, 2022, 10:03

          Japan and the Philippines are both protected from lebensraum by the U.S. military

          We could combine the military and social spending of the US, Japan, and the Philippines, and the result would be an even lower ratio of military to social spending in all 3 countries.

          I am not arguing that military spending generally is too high, just your specific point that military spending is higher than social spending in most countries.

          Both the UK and France maintain nuclear weapons even though they will not be used. There is a perennial discussion about whether Britain should abandon its nuclear deterrent, whether expensive US Trident missiles on British submarines and allow US airbases to maintain a stock of nuclear weapons. Note that even now with a huge budgetary crisis in the UK, there is not the slightest mention of reducing government spending on the military, just whether to increase it as was promised. Britain’s nuclear weapons ensure that it remains a permanent member of the UN security council. [Is Russia’s use of polonium for assassinations the only case of nuclear weapons being used to cause fatalities? US use of depleted uranium shells might be an inadvertent cause of fatalities.]

          What would we do if we went to Proxima Centauri and found a similar situation? Would we land in the middle of their wars and say stop or observe and see what it is doing and why.

          Apart from location, that is exactly the scenario that Stanislaw Lem uses in his novel Fiasco. However, I don’t think we need to worry too much about visiting ETI from Proxima.

          Just how much of global warming is because of military industrial complex expenditures and the wars that are being fought since the industrial revolution, WWII, Vietnam, the middle east and Ukraine.

          Very little compared to the CO2 (and CH4) emissions from fossil fuel use. The direct death toll is likely higher from wars, although the economic blunders of Stalin and Mao have caused the greatest number of deaths to date. Global heating seems sure to kill millions [billions?] slowly, whilst an escalation of war to the use of nukes will do the same much more quickly.

          • Michael C Fidler November 4, 2022, 6:27

            Alex! I’m not talking about us I’m talking about them! We could go round and round forever if you want to keep an earthly perspective, but that is what I’m getting at. What would advanced civilizations do with a bunch of warring natives. They look at the average individual as the same as the richest and most powerful as all the same. The ape that takes all the bananas for themselves is considered psychotic, but we glorify the rich…

            We won WWII and our nation became the most powerful on Earth and cars got 5 miles to the gallon till 1973…

  • Ron S. October 31, 2022, 9:11

    “Tidal Lock is the most stable system for technological civilizations since bizarre weather would not be a problem like spinning worlds have. A nice pleasant land area near the day and night terminator…”

    It is not at all certain that a predictable and extreme environment is better for life than an unpredictable and relative mediocrity. Unpredictability can be a strong evolutionary effect due to its selection pressure for adaptability. In any case, the existence of a habitable zone on a tidally locked planet is speculative since the transition zone is likely to be quite violent.

    • Alex Tolley October 31, 2022, 15:22

      I agree. As well as driving evolution in the myriad ways that change from environment distributions, climate, etc, short-period oscillations have become a part of many animals’ lifestyles, from day/night cycles, lunar cycles, seasonal cycles, etc.

      If a tidally locked planet has extremes of climate depending on where the surface faces, and there is only a “temperate zone” around the terminator, then the available environments for evolution to occur are going to be far more limited. If there is any liberation like the Moon with respect to the earth, then, this could add to the violent conditions at the terminator that you suggest.

    • Michael Fidler November 1, 2022, 7:06

      I think you are just speculating like me, but the M Dwarf planets are much older then earth. Find me a tidal locked planet, the only one is Venus, not a very good example but the weather on its surface is mild if you are from hell! We should have a much better idea as to how tidal locked planets evolve in the next few weeks. JWST is right now looking at the Trappist 1 system and results should be out soon. So how do you know the transition zone is quite violent, that is pure speculation…

      “At the edge of the nightside ice cap (which is not necessarily close to the terminator), there will probably be strong katabatic winds; the ice cap gradually slopes down from the ASP to this edge, and as descending air follows this slope it gains ever-greater speed until it shoots off the edge and buffets the surrounding area. But contrary to some early, simple models of tidal-locked worlds, the entire twilight zone (region of low light on the dayside near the terminator) will not be constantly buffeted by gales; rather, they’d be comparable to prevailing winds on Earth.”


      The planets passing so close to each other may give some chaotic evolution but what may be the norm is highly evolved zones that have effected the whole planet’s geologic systems. Billions of years under the same pattern will cause tremendous changes on the planet.


      The real chaos will be the comet impactors that will be happen at a pace 20 times or more often then our slow earth orbit impacts.

  • Abelard Lindsey October 31, 2022, 19:41

    Assuming aliens remain physical. That is, they don’t do the “uploading” thing and live as software. I would think they would make things like Bishop rings and the link instead of traveling all over interstellar space looking for the few habitable planets. I believe a bishop ring is the largest habitable structure that can be made with current materials. If they can make super-strong exotic matter in industrial quantities, maybe they can make banks orbitals or the like. The amount of real estate from these options are several orders of magnitude greater than a habitable planet and you don’t even need a habitable planet in the system you make them in.

    Exotic materials that would enable banks orbitals are as likely, or unlikely, as any kind of FTL. Yet everyone, especially science fiction writers, film screen writers, and producers assume the latter is much more likely than the former.

  • Javier Garcia November 1, 2022, 18:25

    When we try to answer “Are we alone?”, we mainly refer to aliens similar to humans to the point of being a threat to us.

    If we find somewhere a civilization of ant-like beings, able to explore the space but whose capabilities in terms of self awareness or energy deployment are so low that they can not face a violent confrontation with us, then they will be consider as part of a different level of the Nature and consequently being treated as natural phenomena and not as our pairs.

    • Alex Tolley November 1, 2022, 22:02

      I’m not clear if that scenario works. An individual ant-sized alien cannot have powerful brains. If the nest has a hive mind to reach the necessary cognitive capability needed, then the technology will need to be large enough to transport the nest of individuals, which puts it back at human scale again. I think this will apply whether biological or machine based.

      That is not to say that we may not recognize other life dues to some feature, such as cognition speed like that of plants, or distributed so that we cannot recognize an entity is present.

      But given we have tools and machines that can operate under these differing conditions, I do not think they will evade us for long.

      • Javier Garcia November 8, 2022, 14:01

        I am not saying a strange enough civilization can pass undetected because their achievements can be mistaken by natural phenomena. Which by the way is an interesting idea.

        I am more thinking that, similarly to what happens in some cases in our planet, spices different enough can life together because they don’t compete. Their goals are different or they level of energy is so different that a confrontation makes no sense: for example ants and elephants, whales and other fishes, big mammals and rodents.

        I believe this is also applicable to space. We don’t know whether there is a place where a civilization of strange beings is able to build out of their natal planet and spread into cosmos, and has, like ants, a kind of civilization, without space ships, democratic elections or MTV.

        Surprisingly complex and at the same time so delicate that they can not be a threat for us in terms of fire power.

        I don’t think they would be considered as our pairs. And consequently they could not make a satisfactory answer to the main question of whether we are alone.

  • ljk November 2, 2022, 12:13

    Might placing a radio telescope of serious size on the lunar farside not have to be as complicated and expensive as previous paradigms make such a plan out to be…


    The paper:


    Of course these guys are too savvy to mention SETI at this juncture, but you know that is definitely one of the more if not most interesting uses for such an observatory. To quote:

    “The resulting interferometric radio telescope would provide unprecedented radio images of distant star systems, allowing for the investigation of faint radio signatures of coronal mass ejections and energetic particle events and could also lead to the detection of magnetospheres around exoplanets within their parent star’s habitable zone,” the team wrote in their pre-print paper, published on arXiv.

    Additionally, FARSIDE would have the ability to characterize similar activity in our own solar system, from the Sun to the outer planets, including the hypothetical Planet Nine, said Dr. Gregg Hallinan, Professor of Astronomy at Caltech and one of the authors of the concept study.

    “I would personally be most excited about the search for exoplanet magnetic fields of candidate habitable exoplanets,” Hallinan told Universe Today via email. “This may be a key ingredient for planetary habitability in our own solar system and we have practically no data yet on other exoplanets. It is why I pushed the design to very low radio frequencies that are 100x lower than those accessible from the ground or even Earth-orbit.”

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