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The Dyson Sphere Search

The Dyson sphere has become such a staple of SETI as well as science fiction that it’s hard to conceive how lightly Freeman Dyson himself took the idea. In a 2008 interview with Slate, he described the Dyson sphere as no more than ‘a little joke,’ and noted “it’s amusing that of course you get to be famous only for the things you don’t think are serious.” Indeed, Dyson’s 1960 paper “Search for Artificial Stellar Sources of Infrared Radiation,” was but a one-page document in Science that grew out of his notion that an intelligent civilization might not have any interest in communicating. How, then, would astronomers on Earth go about finding it?

Waste heat was his answer, a nod to the laws of thermodynamics and the detectability of such heat in the infrared. Coming hard on the heels of Frank Drake’s Project Ozma (a likewise playful name, coined out of affection for L. Frank Baum’s imaginary land of Oz), Dyson saw a search for what would come to be called Dyson spheres as a complement in the infrared to what Drake had begun to do with radio telescopes. And in fact, Dyson didn’t refer to spheres at all, but biospheres. Let me quote him on this from the 2008 interview:

I suggested that people actually start looking in the sky with infrared telescopes as well as regular telescopes. So that was the proposal. But unfortunately I added to the end of that the remark that what we’re what we’re looking for is an artificial biosphere, meaning by biosphere just a habitat, something that could be in orbit around the neighboring star where the aliens might be living. So the word biosphere didn’t imply any particular shape. However, the science-fiction writers got hold of this and imagined a biosphere means a sphere, and it has to be some big round ball, so out of that there came these weird notions which ended up on Star Trek.

Changing Notions of a Dyson Sphere

Dyson told Slate he hadn’t been thinking remotely of a shell around a star, but a ‘a swarm of objects surrounding a star,’ one that from the outside would look more or less like a dust cloud. He was also quick to give credit for the concept to writer Olaf Stapledon, who as we saw in the previous post introduced it in his novel Star Maker all the way back in 1937. And indeed, we find Stapledon writing about a way to tap the energies of entire stars through “a gauze of light traps, which focused the escaping solar energy for intelligent use, so that the whole galaxy was dimmed…”

That Star Trek reference is to an episode of Star Trek: The Next Generation that ran on October 12, 1992 (Season 6 Episode 4). It depicted the Enterprise crew encountering a shell-like Dyson sphere. Dyson didn’t mention Larry Niven’s wonderful Ringworld (1970), which draws on the shell concept to envision a vast ring around its star, a ‘cut-through’ of a full Dyson shell. I suspect he read it somewhere along the line, as he was frequently in conversation with science fiction writers who increasingly found his work a source for good ideas.

Image: Olaf Stapledon, author of Star Maker and Last and First Men.

As far as his light-hearted approach to the things he is best remembered for, I take that as a personal quirk. When I interviewed Dyson back in 2003, I found him quick to shift credit for ideas to other people and charmingly dismissive of his own contributions. I think his was an intellect so formidable that it surprised him with ideas that seemed to well up unbidden, so that in a real sense he didn’t want to lay claim to them.

And on Stapledon’s Star Maker, a further thought. It’s fun to note that Dyson sphere hunter Jason Wright at Penn State maintains a blog he calls Astrowright. It’s a fine play on words, I assume intentionally containing a nod to Stapledon. For if a shipwright is a maker of ships, an astrowright is surely a ‘star maker.’

The paper by Wright and Macy Huston that I looked at yesterday notes the distinction between Dyson shells and Dyson spheres; i.e., between a solid spherical shell and a vast collection of objects in orbit around the star, adding that ‘for simplicity of language, we refer to any configuration of a starlight-manipulating megastructure as a Dyson sphere.’ I think that’s common usage throughout the literature, saving the intriguing work on Shkadov thrusters, which are inherently asymmetrical and don’t fit Dyson sphere modeling. But moving stars is a topic for another day.

How Dyson Sphere Searches Proceed

Playful or not, it didn’t take long for Dyson’s SETI notion to take hold. In 1966, Carl Sagan and Russell Walker delved into “The Infrared Detectability of Dyson Civilizations” in a paper for the Astrophysical Journal. This too is no more than a note, but it makes the case for looking for astronomical sources that would appear as blackbodies with a temperature of several hundred K. Such detections were possible, the authors argued, but “discrimination of Dyson civilizations from naturally occurring low temperature objects is very difficult, unless Dyson civilizations have some further distinguishing feature, such as monochromatic radio-freqency emission.”

Note that last comment, because we’ll come back to it. It’s insightful in describing the nature of Dyson sphere searches and the possible results from a detection.

Which brings me to the Russian radio astronomer Vyacheslav Ivanovich Slysh, who in the 1980s examined sources identified by the Infrared Astronomical Satellite (IRAS) in a search for just the kind of waste heat Dyson had discussed. In 2000, Slysh’s work was followed up by M. Y. Timofeev, collaborating with Nikolai Kardashev (most famous, of course, for the ‘Kardashev scale’ ranking technological civilizations).

Richard Carrigan, a scientist emeritus in the Accelerator Division at the Fermi National Accel­era­tor Laboratory, went to work on IRAS data as well and in a 2009 search, used the data on 250,000 infrared sources (covering 96 percent of the sky), looking for both full and partial Dyson spheres in a blackbody temperature region from 100 K to 600 K.

The result: Some 16 candidates with temperatures below 600 K in a field of objects out to 300 parsecs. And as Carrigan noted, most of these have non-technological explanations, and all are in need of further study before any conclusions are drawn. I should also mention the searches for Dyson spheres by Jun Jugaku and Shiro Nishimura when talking about IRAS. Their work in the 1990s found no Dyson spheres around the roughly 550 stars they surveyed within 25 parsecs.

This is a good time to mention some useful background materials. The first is a video presentation Jason Wright made to a seminar at Penn State in 2020, helpfully made available online. It’s an excellent encapsulation of the Dyson sphere concept and the investigations into it, including the subsequent searches using WISE [Wide Field Infrared Survey], with higher resolution than IRAS could provide. One problem with all of these is what Wright dubs ‘infrared cirrus,’ which basically refers to diffuse dust that greatly compromises the consequent data. Carrigan would doubtless have retrieved a much higher number of candidates if he could have worked without this background.

The second reference is Wright’s overview “Dyson Spheres,” which ran in the Serbian Astronomical Journal, Issue 200 (2020), with preprint available here. For those wanting to come up to speed on the origins and development of the idea of Dyson spheres, their purpose, their engineering, and their detectability, this is an excellent resource.

Until reading the Huston & Wright paper, I had been unaware of Massimo Teodorani, whose 2014 paper in Acta Astronautica presented what he called a ‘pragmatic strategy’ for searching for Dyson spheres involving infrared excess and anomalous light curves using Spitzer data to locate such signatures at G-class stars. A common theme in much of this work is the recognition that the goal is to identify interesting targets for further study. A detection of an interesting source would not in itself be proof of an extraterrestrial civilization, but rather identification of an object that could be followed up with more conventional methods such as laser or radio search. There is no single ‘aha!’ moment, but steady and careful analysis.

The search space for Dyson spheres has been expanding dramatically. In the late 1990s, James Annis analyzed the rotational dynamics of 137 different galaxies in the Ursa Major and Virgo galaxy clusters, looking for Kardashev Type III civilizations. He found no evidence for them, but going to this scale inevitably reminds us of the Fermi paradox. As Annis told Lee Billings in 2015:

“Life, once it becomes spacefaring, looks like it could cross a galaxy in as little as 50 million years. And 50 million years is a very short time compared to the billion-year timescales of planets and galaxies. You would expect life to crisscross a galaxy many times in the nearly 14 billion years the universe has been around. Maybe spacefaring civilizations are rare and isolated, but it only takes just one to want and be able to modify its galaxy for you to be able to see it. If you look at enough galaxies, you should eventually see something obviously artificial. That’s why it’s so uncomfortable that the more we look, the more natural everything appears.”

The mid-infrared WISE survey [Wide-field Infrared Survey Explorer] gave us far more data within which to conduct such a search. Wright’s work using WISE data has been extensively covered in these pages, including an article he wrote for Centauri Dreams called Glimpsing Heat from Alien Technologies, the name of the program he started at Penn State. The G-HAT program led to a search through WISE data that culled out some 100,000 galaxies looking for unusually strong signatures in the mid-infrared. Fifty of these galaxies showed interesting infrared properties, though as with Carrigan’s results, without any definitive signs of a technology.

I’ve quoted Wright on this result before, but that was years ago, so let me pull this out again:

“Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes. That’s interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognize them.”

Note the phrasing: This is explicitly a search for Kardashev Type III, one manifestation of which would be civilizations that fill their galaxy with Dyson spheres. The G-HAT results do not close the book on Dyson sphere searches, but they do tell us that such Type III civilizations are not detected within the energy levels we might expect.

Image: A false-color image of the mid-infrared emission from the Great Galaxy in Andromeda, as seen by Nasa’s WISE space telescope. The orange color represents emission from the heat of stars forming in the galaxy’s spiral arms. The G-HAT team used images such as these to search 100,000 nearby galaxies for unusually large amounts of this mid-infrared emission that might arise from alien civilizations. Credit: NASA/JPL-Caltech/WISE Team.

G-HAT is all about putting upper limits on energies emitted as waste heat in nearby galaxies, and while Dysonian SETI methods seem to diverge from earlier radio and laser SETI, the two approaches actually work quite well together. As the search continues, anomalous objects form a catalog which can be consulted by the entire SETI community, using its resources at various wavelengths to probe the result more deeply.

Search References

Although I’m out of time today, I want to make the point that Dyson spheres shouldn’t be thought of purely as means of energy collection, because the manipulation of a star at this level could involve changing the character of the star itself. In a future article I’ll look at why a civilization might want to do this, and who has been investigating the matter. Until then, here are references to the searches we’ve talked about today.

The Sagan and Walker paper is “The Infrared Delectability of Dyson Civilizations,” Astrophysical Journal 144 (3), (1966), p. 1216 (abstract).

The Slysh paper is “A Search in the Infrared to Microwave for Astroengineering Activity,” in The Search for Extraterrestrial Life: Recent Developments, M. D. Papagiannis (Editor), Reidel Pub. Co., Boston, Massachusetts, 1985, p. 315.

Timofeev and Kardashev wrote “A Search of the IRAS Database for Evidence of Dyson Spheres,” Acta Astronautica 46 (2000), p. 655.

Richard Carrigan’s 2009 study is “The IRAS-based Whole-Sky Upper Limit on Dyson Spheres,” Astrophysical Journal 698 (2009), pp. 2075-2086. Abstract / preprint.

The Teodorani paper is “A strategic “viewfinder” for SETI research,” Acta Astronautica Vol. 105, Issue 2 (December 2014). Abstract.

On G-HAT, see Griffith et al., “The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. III. The Reddest Extended Sources in WISE,” Astrophysical Journal Supplement Series Vol. 217, No. 2, published 15 April 2015 (abstract / preprint).


{ 34 comments… add one }
  • Wojciech Jacyk January 20, 2022, 12:27

    The search for K3 civilizations while interesting, seems very ambitious. Due to limitations of speed of light in communication it would require a civilization to either function on a very different timescales or break known physics.
    It would also demand that a civilization constantly expands like bacteria in petri dish, which seems unlikely.

    By the way I have read the paper by M.Yu Timofeev and Kardashev and it states the following:

    “In a future investigation we have selected 10 stellar sources (see Table 2). Seven sources are variable stars, five of them are single stars, one is a binary star, and one is of unknown type. We plan to use
    these 10 objects for next observations at the different frequency ranges”

    Of interest is the unknown type star and if any follow up observations were actually made.

    I believe Carrigan did mention in one of his past papers that modern astronomy doesn’t really have options of confirming found candidates as Dyson Spheres(but I could be wrong). Perhaps technology moved on from that point of time to allow such confirmation?

    And finally, does anyone know if there are any proposals for JWST to observe Tabby’s Star or look/observe Dyson Sphere Candidates in future cycles of observations?

    • gbaikie January 20, 2022, 20:41

      “It would also demand that a civilization constantly expands like bacteria in petri dish, which seems unlikely.”

      I think a civilization is measurably smarter than bacteria in petri dish {or anywhere]. You don’t think bacteria can constantly expand?
      The problem is humans living on a planet which fairly hard to leave- but humans can create system where easier to leave Earth, then go down to corner store.
      The human problem has been, and might always have, is political.
      So, all bacteria would need to do, is overcome or deal with politics.
      There is nothing as particularly as oppressive than our political class- and we had disease for thousands of years- without much measurable “improvement”.
      So, question is, have other civilization actually become civilized, do prevent criminals from running the place. We certainly have not.

    • Jeff Wright January 21, 2022, 4:57

      Forget a sphere…maybe a ‘Dyson Loop’ –reflectors that are themselves on Molniya trajectories that relay starbeams to escaping sail craft. The signature thus isn’t a shell at all…but lobes.
      Now, if the dimming stars nearby one another also have the lobes facing one another…to catch and accelerate, say….

  • ljk January 20, 2022, 12:47

    Let us not forget the late Robert Bradbury’s paradigm-changing ideas regarding Dyson Shells (not Spheres).

    Thankfully, many of his original papers on the subject are saved here:



    Although this is a fictional universe, Orion’s Arm utilizes a number of ideas Bradbury had about Dyson Shells. His most important breakout feature was seeing them as far more than just a new kind of dwelling for organic species. Dyson Shells could be beings unto themselves for a variety of reasons.

    Others have also envisioned Dyson Shells/Swarms as places to launch interstellar vessels using beamed power, or as weapons of immense power, reach, and destruction.


    Regarding the Nicoll-Dyson beam, see these two next:



    Other references:



  • Alex Tolley January 20, 2022, 12:57

    My first (I think) scifi story encounter with a solid sphere was Shaw’s “Orbitsville”. The sheer size of the interior surface was depicted quite well.

    For shell-type DSs, why must they emit excess heat isothermally over the surface? Some equivalent of a heat pump could maintain a very low surface temperature with the excess heat concentrated and emitted in narrow beams/jets. The DS would then appear dark unless the observer was able to detect that beam/jet. It only makes sense if the DS is a swarm of habitats, and even then…

    It must take time to create a complete star enclosing swarm. Why not are habitats forming a think ring around the star, rather than enclosing it? The star would still look bright, but perhaps look like it had a protoplanetary ring around it, as well as planets that were not dismantled.

  • William S Guerin January 20, 2022, 13:28

    See my Dyson Shutter toward the end of this Centauri-Dreams Article;


    Low bandwidth high visibility

    • Scott Guerin January 23, 2022, 8:28

      Is a Dyson Sphere/Swarm/Ring/Shutter a solution in search of a problem? At least the shutter is a signaling system.

      I am intrigued by @traeh’s comment below. Why would a million year old civilization waste time building a big collector/radiator when 95% of what we see around us is unknown? It suggests to me that 95% of physics remains thusly unknown, and as Traeh suggests, that part of the universe is the real playground.

      Casimir effect energy and propulsion, using multiverses as batteries and waste heat dumps, dark matter fusion, black hole habitats, or lower vacuum energy bubbles (ala Greg Egan’s Schild’s Ladder) and unimaginable other technologies run by vast minds could be invisible to us.

      On the other hand: we’re just simply it in our observable space/time.

  • Jason Wright January 20, 2022, 13:34

    Thanks for the very nice writeup of this work!

    I’ll add that Dyson was considerably more serious about Dyson Spheres than he let on. He clarified in letters to the editor to his short Science article that he was not thinking on solid spheres:

    And he wrote a much longer explanation of the idea with detailed engineering notes here:

    The term “Dyson sphere” was coined by Kardashev in his classic 1964 paper:

  • Stanley January 20, 2022, 15:41

    I wonder, has anyone considered that a significantly advanced civilization would use a very efficient energy conversion system, thus reducing their waste energy signature?

    • Robert January 21, 2022, 12:49

      We are told that energy cannot be created or destroyed but it merely changes form. It seems to me regardless of how efficient in converting energy an advanced society was, if they build a Dyson sphere around a star to capture all of that stars energy, beyond the growth phase of forming the Dyson sphere, when they reach some equilibrium, they are going to have to reject as much waste heat as solar energy they absorb or they will end up like the surface of Venus. If not, I’m not sure how such a society could use essentially all the energy of a star without most of it eventually converting to waste heat. What would they be doing with it?

      • Dan K January 25, 2022, 18:41

        “What would they be doing with it?”
        A few possibilities:
        1) Converting it into matter
        2) Expelling all waste energy in a single directed beam. That would make them harder to detect unless you happened to on the line of the beam. If they wanted to stay hidden.

    • gbaikie January 29, 2022, 3:35

      I think energy per capita, could quite low if we were spacefaring civilization. But we don’t count the energy of the sun as energy cost- unless you count your feeble solar harvesting with solar panels which convert sunlight into electrical power. But use a lot solar energy to grow everything- not counted. In terms solar panels use on Earth we waste a lot energy, as compared solar panels used in space. Solar panels for electrical power in Germany are very inefficient, but in places with more sunlight one gets solar energy around 25% of the time and its fairly dim sunlight. And solar panels only use part of solar spectrum. But without trying imagine how separate the sun’s sunlight, one can simply look at sunlight reaching Venus L-1, about 2600 watts and 100% of the time, that makes solar energy a different thing than solar energy on Earth surface. Plus sunlight at earth surface can’t boil water, whereas lunar sunlight, can. We spend a lot energy boiling water.
      We spend a lot energy cooling stuff.
      Permanent shadow in space is cheap- or making liquid air is cheap on Earth, but with permanent shadow liquid air in space is cheaper {assuming one get some air to turn into a liquid]. It seems one can passively keep house warm or cool enough somewhat on Earth, and seems one more easily do this in space. Or ISS is not really designed for this, but main thing with ISS, is cooling it.
      The big advantage of Earth, is it at constant and correct air pressure, and structurally to hold that much pressure in space environment is an economic/energy extra cost. And other free thing, is Earth gravity.
      It seems harder part is related space to making artificial gravity- and whether any kind artificial gravity can actually replace the “natural” Earth gravity. But it seems making stuff hot and keeping it hot, and making stuff cold and keeping it cold, seem fairly simple in space.
      What is normally considered expensive/requiring a lot energy regarding space, is transportation.
      But this largely related to high cost to leave Earth. Which can be lowered, quite significantly, in not too distance future.

  • GeordieTwo January 20, 2022, 15:55

    I don’t believe in endless technological advancement by any sentient species. Life works via a series of feedback loops (among other things of course) and these are both positive and negative. Species arise and disappear over varying timescales. If a technological civilization arises it may be gone again before achieving anything like a Dyson sphere around its home star, let alone any other nearby stars. It seems likely sentience is rare and possibly often fleeting when measured by the timescales of galaxies. Why is that surprising? There may be no Dyson spheres around any star in any galaxies we can observe. There may be no Kardashev type III civilizations. Advanced sentient species may go in entirely different directions, such as using less and less energy per “person” and even then these civilizations may disappear in relatively short time frames as well (meaning tens to hundreds of thousands of years). The lack of results with these efforts doesn’t surprise me at all. The lack of results may also just reflect our fairly feeble current abilities to detect advanced civilizations. Let’s check our results again in a thousand years if our own civilization lasts that long.

    • Alex Tolley January 20, 2022, 19:40

      A corollary to civilizations that have fleeting lifetimes (L) on the cosmic scale, that such civilizations are rare in space and time, and that interstellar travel (and communication) is limited by c, then there should be no real issue about hiding ourselves (or shouting into the dark). For all intents and purposes, our space-time bubble is empty of high technology civilizations. In terrestrial terms, it is like being on foot in the desert, with only desert-adapted creatures around, and no other human within earshot or walking distance before death arrives, and no one is likely to meet one by chance.

      So no saviors from space to save up from our stupidities. Little change that humans 1.0 will reach the stars, although our machine descendants may do so. [Maybe machine “civilization” can outlive an advanced, biological civilization, if so, maybe they will meet another such civilization.]

      • Gary Wilson January 20, 2022, 20:40

        I absolutely agree Alex. There is nobody organic near enough to our space time bubble to communicate with and there won’t be over the likely time span of our species. Machine intelligence either here or elsewhere is a different matter. We may find evidence of an intelligent visitor from the far past in our solar system or nearby eventually but no organic beings. Possibly we have recently or in the past been visited by advanced machine intelligences. How would we know if they are sufficiently advanced to hide or escape capture? I’m more afraid of us than of aliens. I wouldn’t be surprised if a machine intelligence found us quite revolting in our behaviour and attitudes towards each other and to the other species inhabiting the Earth. GeordieTwo is me by the way. Sorry about that. No intention to mislead.

  • Ivan Vuletich January 20, 2022, 22:54

    Maybe the reason that Dyson swarms are undetectable on an excess IR basis is that a more realistic upper limit on swarm density is set by a requirement to avoid the Kessler syndrome https://en.wikipedia.org/wiki/Kessler_syndrome.

    This is already a problem in LEO and while a ~1 au orbit around a Sun-like star has a lot more room, the collision velocities are a lot higher, with a worst case collision having a relative velocity on the order of 42 km/s.

    Taking a long term view, there is not much point in building a Dyson swarm if a substantial fraction of your physical resources need to be devoted to debris mitigation and station keeping. And no point in building a Matrioshka brain if most of your processing power needs to be devoted to conjunction assessment.

    Assuming these constraints the design requirements of a Dyson swarm are likely to emphasize things like propellant-less station keeping maybe using radiation pressure and/or the solar wind, some form of space traffic management like a well defined number of satellites evenly spaced in circular orbits, with the orbits arranged in well defined shells to minimise the chances of collision. Another requirement is liable to be sweeping of the inner solar system to keep the swarm orbits clear of dust, rocks and end of life satellites.

    The overall number of satellites is also likely to need to be capped at some limit to keep the collision risk and traffic management requirements low. Which will lead to a much sparser swarm than would be expected purely on physics constraints.

    So, in terms of hunting down Dyson swarms, maybe the observational criteria should be things like anomalously low IR emission at the wavelengths corresponding to dust, and regular high cadence patterns in either transits or glints from solar sails.

  • Brian Altmeyer January 21, 2022, 0:23

    Looking for Dyson spheres/swarms is a worthy goal, but should be low-priority compared to humbler objectives like detecting techno-signatures in planetary atmospheres. Just by sheer logic, the latter should be much more common and easy to find if civilization is as abundant as we hope.

    Even if the most common form of civilization is weirder than we would know to look for, things like us should be relatively common if our assumptions make any kind of sense. Certainly more so than Kardashev IIs and IIIs, which we probably won’t find until we can sample entire galaxies.

    The search for Dyson structures is like trying to find human footprints by scoping individual grains of sand on Earth. Even if you’re doing them a thousand at a time, the statistics are daunting.

  • Andrew P January 21, 2022, 10:16

    Our current minor pandemic got me thinking that the size of a technological species (as in # of individuals) and their distribution is limited by infectious disease. As the number of individuals increase so does the probability of a deadly pathogen emerging – particularly once the species does genetic manipulation of organisms and has lab accidents. The probability must be a highly non-linear function of # of individuals and their density distribution. And expanding into space makes the problem worse. Much worse. Just imagine a person growing up in an isolated Mars colony and visiting earth in adulthood. I can’t imagine he would last a year after exposure to viruses and bacteria unlike any he ever experienced before. The reverse is also true about an Earth person visiting a Mars colony or any distant isolated colony. It is therefore very unlikely that any civilization expanding into space will be able to function as a single civilization. Distant colonies will rapidly become isolated from their parent. In fact, if new virulent strains of SARS2 evolve on Earth, countries may disconnect from each other like a Tower of Babel, as international trade and travel drop to near zero. And I am not even considering the likelihood of biological war.

    • Ron S. January 21, 2022, 19:59

      Our ability to rapidly respond to, manage and prevent disease has a far faster rate than our ability to become star faring. It won’t be a problem.

  • Mike Serfas January 21, 2022, 12:13

    A Dyson swarm seems more believable in terms of having a gradual origin, but it is not tremendously different from a sphere. It is essentially a forest canopy around a star, with the advantage that different parts routinely orbit into close proximity, and the disadvantage that large-scale structures are difficult to negotiate into the existing system of orbits.

    I don’t believe that waste heat needs to be an issue for advanced civilizations. Even humanity, if it can progress a few centuries further, should be able to defeat this problem. All we need is some kind of catalyst that can do neutrino pair production. We don’t know exactly how small the smallest neutrino is, but it’s *tiny*. Each of those neutrinos and antineutrinos produced ought to carry away the standard 3/2 kT of thermal energy like any other particle. Additionally, there is discussion of “neutrino nuggets” – chemistry-like associations of neutrinos. (I’m not qualified to recommend specific papers there, but try a search for that term and draw your own conclusions) We’re nowhere near making these diffuse structures, but bear in mind that if we had a magic enzyme that only interacted with a particular *combination* of neutrinos and their antimatter equivalent, then it would not take up energy from any other type of emitter nearby, so it should be possible to increase the total heat dissipation for each such channel. I think an alien civilization could use this (and/or other means I can’t imagine) to disperse their entropy into the universe in a way that we’re not prepared to see yet, and which is less disruptive to ordinary activities than EM radiation.

  • traeh January 22, 2022, 1:08

    A million-year-old alien civilization would presumably have developed an inconceivably more encompassing experience and conception of the world than we possess. Their experience might be so much more profound and advanced as to make our relativity- and quantum physics and our whole mode of experience 95% illusion by comparison. Put differently, they may think of relativity and quantum physics (if at all), as relevant to only 5% of reality, with other conceptions necessary for the rest of reality. In that light, our extrapolations and imaginings of a million-year-old civilization, our hypotheses of Dyson spheres, for example, might seem to those aliens a quaint projection of our own image onto a world of experience and thought almost completely different in its goals and extent. Which is not to say that we shouldn’t search for Dyson spheres, but we may be sleepwalking much more than we know, living within a paradigm far more limited than we realize, perhaps a paradigm that filters from view the very things that would make million-year-old civilizations (if such exist) visible to us. The Dyson-spheres concept may tell us much more about ourselves than about some super-advanced civilization. But we have to start somewhere…

    • Alex Tolley January 22, 2022, 10:35

      The Dyson-spheres concept may tell us much more about ourselves than about some super-advanced civilization.

      Or ideas of ETI are very likely biased by projections of our society. For example, invading aliens taking over our planet is a staple since Wells, and reflects our long history, especially the colonialist history that was about to end when Wells wrote “War of the Worlds”.

      However, just because ETI may know more about the universe than we do does not necessarily imply their worldview will change to reflect this knowledge. Our knowledge of science and reality dwarfs that of the ancients, but it doesn’t seem to change the basics of human behavior, which is reflected in both ancient and contemporary societies. For example, the acquisition of wealth and power seems a constant. Control over others whether by slavery or employment arrangements hasn’t changed much (and illegal slavery exists today, even occasionally in our so-called enlightened modern Western society). I would argue that knowledge is mostly reflected in technology, of which ETI’s might seem like magic to us, but their behavior will probably be that of their evolutionary history, as ours is of our primate lineage.

      • Mike Serfas January 24, 2022, 9:49

        I would disagree with this. Human society really has changed, even if there are throwbacks. For example, the situation of women – even in Afghanistan – is better than what it was a few centuries back in most places. Mass rape, foot-binding, sati … common and widespread horrors have been sent to the endangered species list, if not outright extinction.

        Moreover, the advance of technology is inherently limited by the ability of society to improve in these more fundamental ways. Imagine what Henry VIII would have done with nuclear weapons! The ability to have such destructive instruments and not get sent back to the drawing board is dependent on the ability to do things in a more reasonable, equitable, free manner.

        We know this in our own time: corporate duplicity limits what we can do with software without fearing for privacy and the consequences of social bullying when employers routinely cave to it and workers don’t have another route to income. An outbreak of Covid is killing hundreds of thousands more people than it had to because public health authorities can’t overcome the embedded system of economic penalties enough to limit early transmission, and many people aren’t trusting the modern system of medical regulation even enough to take a vaccine. The daydreams of billionaire supervillains who want to put chips in people’s brains and wrap transcranial magnetic stimulators around nurses’ heads to keep them working 24/7 are right out – and so are any potential beneficial uses of such technologies that a wiser society might have safely enjoyed.

        If we believe that a genuine philosophical and moral progress in society is impossible, then we have met the end of this cycle of civilization. We won’t find aliens channeling the power of stars based on the bonus one of them expects after the next quarterly report.

        • Alex Tolley January 24, 2022, 14:53

          I get what you are saying. I agree that attitudes have changed, e.g. slavery is not really acceptable in most countries (although I would argue it has been transmuted), women definitely have the vote (although not in Switzerland until 1973?) but patriarchy is still predominant, as is rape, etc., and if nuclear weapons really are unusable, why haven’t we been able to universally abandon them?)

          So yes, we seem to have somewhat spottily been able to change our attitudes, but just how deep is this in our human psyche? As I said, we still seem to be deeply ruled by our ancestral evolution. So we don’t pick lice out of our close neighbors, just groom them in other ways, with words, gifts, etc.

          Pinker has argued that we have become less violent, but how much of that is due to our social structure, and how much is it due to changing ourselves? When laws and enforcement break down, violence seems to become rampant again, a correlation that seems quite evident when states fail, and even across US states where different gun laws impact homicide rates.

          Had we shown Henry VIII the effect of a nuclear weapon and told him that France had them as well, would he really attempt a first strike on Versailles, knowing that he could also be targeted? Maybe he and the French king (Louis XII/Francis I/Henry II) would agree to an armistice and cease hostilities?

          • Mike Serfas January 29, 2022, 18:52

            Alex: you raised some interesting points that are hard to respond to convincingly, but I should say some thoughts that come to mind. First, as to whether we are ruled by ancestral evolution … I am tempted to make an inductive leap here. Formerly it was common to argue that women or certain races had some inherent limitations, which may have seemed realistic at the time but faded when challenged like fog in the sunlight. So … are all of us still a bit bigoted against humans? Do we all assume that people have less potential than they actually do, and make it come true by mere assumption?

            When it comes to Henry VIII, yes, it looks like he could have simply chosen to be truly noble and done all the right things. But is it true? No matter how absolute the monarch, if he did not have a hypothetical nuke literally strapped to his back, he would be relying on others to control it. But in former times, where could you have found soldiers with the honor of a modern army, who would not sell their bomb on the market or use it in a plot to take over their country? Who could a monarch have trusted, to believe for sure that another country was not preparing a first strike? Whose condemnation would he have feared, had he made a bold strike that cost lives but increased his power before someone else could do the same?

            It seems to me that in moral or philosophical matters that there is something of a social Fermi sea that ties a society together, everyone in it, great and small, on one side and another. For example, if person A holds a prejudice against a certain group and holds them in contempt, and a person B, who is a member of that group, makes a foolhardy decision that discounts the value of their own life, I think there is an equilibrium between A and B. So I’m disposed to think that at least in the long term a decision whether to launch a nuclear war is directly affected by the everyday character of the entire population. While it is easy to imagine that a ‘Connecticut Yankee’ could have shown up to save the day, it seems like the best people only find some cross to be nailed to. Now that’s only a conceptual model, and even that should be stochastic, especially in societies where a few have outsized media influence. But my guess remains that 16th-century nuclear weapons would quickly and inevitably have been used, again and again, until they no longer could be. I suspect only the enlightenment of the overall population could change that.

  • Robin Datta January 22, 2022, 6:47

    The microbe’s ideology is often overshoot ==> dieback (if lucky) but fequently dieoff. Microbes that survived innumerable such cycles may have been the ones that evolved hardy spores to tide them over the dire times. However, that ideology may have been carried through even to humans: just as soon as fossil fuel energy became available, and with it the abundance of food, clean water and the control of communicable diseases, Homo sapiens manifested the behavior no better than that of yeasts in a vat in a brewery.

    An intelligent species that expects to survive for the long term will need to see the big picture and choose parsimony over profligacy in time to avoid the worst consequences. Even their Dyson spheres/shells/swarms etc. would be tailored to minimize the disruption of matter and energy. Growth for growth’s sake is an imperative of biology, but has also been noted to be the ideology of the cancer cell.

  • Daniel January 23, 2022, 20:34

    In my opinion Dyson Sphere it’s pure fantasy, explain how its go to building something like this, normally most of a planetary system mass concentrate in the star (99% of the planetary system mass) and 1% left I doubt will be enough to cover the entire star, even if you get from other planetary systems how this material would be transported? Even if was possible to transport the material many planetary systems material would be necessary to building such extraordinary structure, so I guess this destroyed system around would be detected.

  • ljk January 27, 2022, 13:38


    [Submitted on 26 Jan 2022]

    Project Hephaistos I. Upper limits on partial Dyson spheres in the Milky Way

    Matías Suazo, Erik Zackrisson, Jason T. Wright, Andreas Korn, Macy Huston

    Dyson spheres are hypothetical megastructures built by advanced extraterrestrial civilizations to harvest radiation energy from stars.

    Here, we combine optical data from Gaia DR2 with mid-infrared data from AllWISE to set the strongest upper limits to date on the prevalence of partial Dyson spheres within the Milky Way, based on their expected waste-heat signatures.

    Conservative upper limits are presented on the fraction of stars at G ≤ 21 that may potentially host non-reflective Dyson spheres that absorb 1 – 90% of the bolometric luminosity of their host stars and emit thermal waste-heat in the 100 – 1000 K range.

    Based on a sample of ≈ 2.7e5 stars within 100 pc, we find that a fraction less than ≈ 2e−5 could potentially host ∼300 K Dyson spheres at 90% completion. These limits become progressively weaker for less complete Dyson spheres due to increased confusion with naturally occurring sources of strong mid-infrared radiation, and also at larger distances, due to the detection limits of WISE.

    For the ∼2.9e8 stars within 5 kpc in our Milky Way sample, the corresponding upper limit on the fraction of stars that could potentially be ∼300 K Dyson spheres at 90% completion is ≤ 8e−4.

    Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

    Cite as: arXiv:2201.11123 [astro-ph.GA]
    (or arXiv:2201.11123v1 [astro-ph.GA] for this version)

    Submission history

    From: Matías Suazo [view email]

    [v1] Wed, 26 Jan 2022 18:59:36 UTC (4,174 KB)


    • Alex Tolley January 27, 2022, 18:52

      An upper limit of 8e-4 fraction of 2.9e8 stars within 5kpc ( ~ 16,000 ly) is 232,000 stars. A lot to look at more carefully! Scaled up for all the stars in the galaxy implies about 1000x more.

      Not just a careful local search, but a very long search by interstellar exploration over the coming 10s of millennia.

  • Mike Serfas January 28, 2022, 14:45

    I’m hoping Centauri Dreams will run something giving us the lowdown on a most intriguing set of ‘megastructures’ at the center of the galaxy reported in the news a few days back: https://arxiv.org/pdf/2201.10552.pdf Looking at the sheer scale and unexpected consistency of these strange magnetic filaments, they seem ripe for interesting explanations, mainstream or otherwise. :)

  • ljk January 31, 2022, 11:38

    As Star Trek: The Next Generation did for Dyson Shells (not Spheres) in their 1992 episode Relics, so too is that new Disney+ Star Wars series on Boba Fett doing for educating the public on Ringworlds:


    A nice video on Ringworlds:


    And one from the same series on Dyson Shells:


    The rundown on the ST:TNG episode Relics:


    If nothing else it gets humans thinking on much larger scales than most of them usually do. Mind expansion is always good, right?

  • A layman February 1, 2022, 12:45

    We look for something that we already know, that we understand, that we can see/Hear/smell. In the past they looked for Spears, then for chariots, then for immutables Laws, then for watches and automatas up there in the Sky. But they had no clue as to the sheer, unfathomable, abysimal, mind-boggling quantity of space out there. We know It, still we Imagine an universe filled with individual points of view, with biological or artificial intelligence, teaming together for domination purposes, riding Rockets propelled by antimatter and communicating instantly thanks to entanglement. How can we be still so naive?

  • ljk February 1, 2022, 13:58
  • ljk February 8, 2022, 15:50


    After Einstein’s e = mc squared. New technology is improving our ability to search the skies for signs of possible extraterrestrial civilizations

    FEBRUARY 5, 2022

    Last year marked the sixtieth year of the iconic Drake Equation, developed by astronomer Frank Drake aimed at stimulating the public to think about the prerequisites for life on other planets. Seth Shostak at Search for Extraterrestrial Intelligence (SETI) says it is the most famous equation after e = mc2 and offers a bit of its history:

    The Drake Equation was cooked up by astronomer Frank Drake in 1961 to serve as the agenda for the first meeting on the topic of SETI. In 1960, Drake had conducted a pioneering search for extraterrestrial signals – a several-week long effort he named Project Ozma. Somewhat unexpectedly, this modest experiment attracted a great deal of attention, and Drake was encouraged by J.P.T. Pearman, a staff officer at the National Academy of Sciences, to organize an informal gathering of accomplished researchers and engineers to discuss the prospects for finding a signal. Was listening for radio signals a worthy endeavor or not?

    Approximately a dozen people attended this informal meeting, and they all were eminent. Among them was biochemist Melvin Calvin (who received a call during the meeting notifying him that he had just won the Nobel Prize), biologist Joshua Lederberg, physicist Philip Morrison, and planetary astronomer Carl Sagan, as well as Peter Pearman and self-invited guest Barney Oliver, a highly accomplished radio engineer. The conference took place at the Green Bank Observatory – the site of Project Ozma – in November 1961.

    He notes that the equation comprises seven factors (which he explains) that, if multiplied, might yield the number of extraterrestrial civilizations that might be broadcasting signals we could pick up.

    The Drake Equation has functioned mainly as a discussion anchor over the years, as well as a way of determining what searches might be useful.

    Drake’s daughter Nadia offers some insights as to how her then 91-year-old father got interested in the idea:

    Dad first started wondering whether humans are alone in the cosmos when he was growing up in Chicago in the 1930s and his dad mentioned one day that “there are other worlds out there.”

    My grandfather was talking about the other planets in the solar system—at the time, they were the only planets humans knew of—but eight-year-old Frank didn’t know that. To him, “other worlds” meant “other worlds like Earth,” places populated by smart, exotic beings who might be broadcasting their presence to the stars. The idea made sense to Dad, and he began thinking about how to detect such worlds.

    “To find the existence of intelligent creatures that are conscious—that would be very exciting,” Dad says now. “I wonder how widespread that situation is, in the universe.”


    The rest of the article is here…


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