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A SETI Reality Check

Given how much we do not know about everything from abiogenesis to the lifetime of technological civilizations, what can we say about SETI’s chances for success? Henry Cordova, a Centauri Dreams regular, is a long-time SETI enthusiast who has nonetheless been revising his thinking on the discipline’s prospects. Our one useful sample, Earth, tells us how long it took for life just to become multi-cellular, much less to reach the tiny window opened by our technological society. And need we assume that intelligence will inevitably arise even with complex biology to support it? A retired geographer and mapmaker currently living in southeast Florida, Henry served in the US Navy and was originally trained as an astronomer and mathematician. Amateur astronomy, celestial navigation and collecting star atlases occupy his time when he’s not pondering questions like how civilization might arise without technology, or whether Dysonian strategies — looking not for beacons but evidence in the form of engineering suggested by anomalies in our data — may or may not be the best way for SETI to proceed. One thing’s for sure: The questions SETI raises offer many solutions, not all of which lead to contact.

by Henry Cordova

The last few years have been kind to SETI enthusiasts. As hard scientific facts continue to accumulate, the factors in the Drake equation seem a little less unknowable and the evidence, although circumstantial, is starting to look very compelling. We know now that the molecular clouds where solar systems form are seeded with the chemical precursors to life and with the comets and meteoroids which can transfer this chemistry to planetary surfaces. The detection of organic compounds in meteorites and in the spectra of celestial bodies, as well as the serious proposal of fossils of Martian microbes, all argue that science is comfortable with the idea that life arises spontaneously wherever conditions are favorable. Our planet’s own geological history corroborates this; it appears that life began here almost as soon as the primitive Earth cooled. The non-photosynthetic food chains found in submarine vents and the recent discovery of deep crustal microbial communities have made scientists comfortable with speculation of life on Europa and other solar system sites. It now seems likely that life can gain a foothold in any suitable environment and will arise spontaneously in many places throughout the universe.

We may add to this evidence the results of one of the more mature branches of astronomy: stellar structure and evolution. Stable and long-lived stars suitable for nurturing life seem to be the rule, not the exception, and planets are probably a normal by-product of the formation of these systems. The recent detection of many extrasolar planets, albeit non-earthlike, suggests our own solar system is not unique. All the evidence is not in, but it is not unreasonable to assume that life is quite common in the Galaxy. Our own planet’s past supports the conclusion that living worlds are self-regulating and quite capable of surviving all but the most devastating of cosmic catastrophes. The combined speculations of astronomy, geology, and biology are in agreement that SETI is on the right track. In my opinion, there are tens of millions of life-bearing worlds at this moment in our galaxy, give or take an order of magnitude.

And now, the bad news… The evidence for extraterrestrial intelligence, that is, extrasolar species capable of constructing communications devices, is totally non-existent. We have very little to go on other than our own example. The Earth has been the abode of life for at least 3 billion years, but for most of that time it was represented by only the most primitive micro-organisms. For a substantial portion of Earth’s history life consisted solely of anaerobic microbes. The development of photosynthesis appears to be a bottleneck in evolution, but not as severe as the appearance of multi-cellular organisms, which did not appear until about half a billion years ago. If this pattern is not peculiar to Earth and is typical of life-bearing worlds, the consequences for SETI are troubling.

SETI requires reasonably complex and active life forms as participants–on both sides. We must expect that candidate species share an oxygen metabolism and a multicellular architecture comparable to vertebrates in sophistication. We know that intelligent primates, and possibly intelligent cetaceans, appeared on Earth only a half-billion years after the first appearance of multicellular creatures, a relatively short time by astronomical standards. But we should not conclude that intelligence was inevitable, simply awaiting a mammalian nervous system of sufficient capacity to support it. Mammals have been around for as long as the reptiles and have spent most of this time without developing any technical abilities. The dinosaurs and birds never chose intelligence as a strategy, and the cetaceans prove that even intelligence does not necessarily lead to tool-making. Primate cooperative technical intelligence, aided by language, arose only a heartbeat ago in the cosmic time scale. Its late arrival and explosive growth suggests it was not inevitable, and probably accidental. We cannot even conclude from this history that intelligence is a survival trait; it is possible that its very advantage to a species is destabilizing to the biosphere as a whole. I shall omit at this point the usual cautionary remarks about nuclear war and environmental pollution… Neither should we forget that highly advanced civilizations need not necessarily be technological, even if they start out that way.

If we determine that technical societies capable of interstellar communication are common and not prone to self-destruction; it is still not obvious that they will be eager to communicate with us. Many will be cautious about talking to strangers and choose only to listen, others may tire of SETI after the first success–just as I suspect we will, as much as I hate to admit it! In fact, the more likely a culture is to engage in SETI, the more likely that it already has all the correspondents it wants. Once a SETI-prone species makes contact, it may prefer to cancel expensive searches using energy-inefficient methods and concentrate on upgrading its existing communications and refining its technologies. In other words, if CETI is common and widespread in the Galaxy, newcomers will probably not be sought out very aggressively.

The limiting factor in interstellar communication is not distance, but time. Even neighboring civilizations might be highly separated in time, time also affects the conduct of individual contacts. Centuries have to pass before each transmission’s success can even be evaluated. If we assume that during the course of its existence the Galaxy has hosted a million technical societies, and each of them survived an average of a million years, at any one time we could expect only a hundred active cultures in the entire Galaxy–about one for every billion stars. These numbers are not very encouraging, the average age of a civilization is one of the big teasers in the Drake Equation. For ETIs to be common enough to find easily this value has to be inordinately high. It seems inescapable that even if civilizations are very common, at any one time they are few and far between.

It is risky to make predictions about ETIs, but let’s try a few very liberal assumptions in order to further explore some issues in SETI targeting. Assume that there are a million species in the Galaxy right now capable of and interested in communicating with their neighbors using microwave or laser technology (the only ways we know how!). With about a hundred billion stars in the Galaxy, this works out to about one civilization for every hundred thousand stars. The stellar density in the solar neighborhood is such that there are approximately that many stars within two hundred light-years of Earth. This line of reasoning suggests that civilizations are at least several hundred light-years apart and that for them to have the slightest chance of contacting their neighbors they must be prepared to transmit (and listen) to hundreds of thousands of stars for millions of years just to have a fighting chance of making a one-way contact. Even if our hypothetical ETI is capable of using advanced astronomical techniques to eliminate unsuitable stars, the magnitude of this task is enormous.

Any society contemplating a passive search for the first time (like us) must hope that its neighbors have been carefully tracking thousands of targets and transmitting continuously at them for millions of years in order to have even the remotest statistical chance of intercepting a signal. Passive SETI is easy, but it depends primarily on what the other guy is doing. If the passive party further expects the active member to be transmitting at him in a narrow, energy-efficient beam, and has designed its listening strategy accordingly, in my opinion, they are wasting their time and squandering their budget.

Most SETI passive strategies are based on high signal-to-noise ratio directed searches of nearby stars, selected for their high probability of harboring intelligent life (old and stable Pop I disc stars on the main sequence). But as we have demonstrated, even a perfectly suitable world is highly unlikely to be transmitting at us when we look at it. To have a good chance of intercepting a signal, we must simultaneously observe large numbers of stars, i.e., large volumes of space. The active partner will also realize this, and will know that transmitting directly at nearby sunlike stars on narrow beams will be energy-efficient but highly ineffective. To listen (or transmit) using narrow “spotlight” methods allows weak signals to be heard or sent immense distances, but does little to maximize the number of stars reached. A “floodlight” or broadcast approach will saturate small volumes of space with signal, but is very wasteful and reaches few stars for the energy expended.

I suspect advanced SETI species will adopt an intermediate “searchlight” methodology where a wide beam, on the order of a radian in diameter, will be aimed at regions where large numbers of stars are found. I envision active transmitters to be aimed at the galactic plane, the signal footprint wide enough to encompass the thickness of the entire Milky Way and nearby disk stars. The best way to listen for these signals would be to concentrate on wide areas near the galactic equator, and to worry about the location where the signal originates only after it has been detected. Design receivers for sensitivity, not resolution. In other words, sweep the galactic plane first, particularly in areas of high galactic longitude. ETI will most likely be transmitting towards the nucleus, the direction where most of the old stars are. Those civilizations at low galactic longitudes might even be transmitting across our line of sight, towards the galactic center, and we would not be able to hear them at all.

We have just recently learned, in cosmic terms, how to conduct SETI. At present, we cannot develop the antenna power to transmit a searchlight signal that would stick out above the noise for more than a few light years. We can only hope that others have been at this a lot longer than we have and will be able to do so.

The remarks above apply to the traditional thinking on SETI that has been the operational paradigm since the introduction of radio astronomy. The only way we know to make our presence known across galactic distances is with electromagnetic radiation, radio, or possibly, laser signalling devices. This may not necessarily be the case, but we have little choice but to proceed as if it were. We are forced to conclude that the only way to find ET is with physics-based technology similar to our own.

But what if there may be highly advanced civilizations with no technology at all? I suspect that high degrees of sophistication and culture are possible with no technology whatsoever. This may be no surprise to anyone reading this, but has the consequent reduction of the statistical probability of communicating civilizations sunk in to the average SETI enthusiast?

I must confess it has become apparent to me only lately. As you get older, you get wiser. Not necessarily smarter, but wiser.

And what about technical civilizations whose development proceeded among lines very different from ours? A cetacean-like creature may have evolved along acoustic lines, not mechanical or electro-magnetic. A commensal colonial organism might have concentrated on genetic technologies, breeding living organisms for practical use, rather than building machines. Some societies may have highly advanced chemistry based on biological concepts, rather than in vitro tech. Alien civilizations may not even be recognizable to our eyes as civilizations; we may only see them as complex ecosystems, rain forests or coral reefs (Gaia and Solaris-type entities come to mind) than as communities. Some civilizations may have evolved on permanently cloudy worlds, or under water, or in water under ice under clouds.

Even if we could realize them for what they are, they may be operating on vastly different timescales than we do. Those of us who read science fiction no doubt are familiar with these possibilities, but do we ever really consider how that rarest of cosmic accidents, the intelligent alien species, is made even rarer still by the fact maybe they never discovered fire, electricity, glass, metals? No matter how many of them there are, if they can’t build radio telescopes or spacecraft, how will they find us? How will we even recognize them if we find them first?

And of course, there is always the possibility they will have long ago stumbled onto technologies that make radio telescopes and spacecraft unnecessary. Broadcasting microwaves at nearby stars may be like Amazonian tribesmen trying to signal jet contrails by beating drums or lighting fires. There are lots of things allowed by nature that we do not know about, that perhaps we will never know about.

Indirect evidence suggests that SETI-capable civilizations will be highly separated in space and even more so in time. There may be a much smaller probability than previously thought to make contact with these cultures. In order to maximize this probability, we may have to rely on search strategies which are counter-intuitive. We can only hope that these civilizations will also anticipate these conditions and modify their procedures accordingly. I wish to go on record as saying that conducting passive searches for alien communications is a waste of resources. The aliens have probably realized this and are not actively signalling us anyway. Although I hesitate to suggest that any form of research be discouraged, perhaps our resources could be directed in other, more productive directions. At the very least, our searches could be piggybacked onto other research programs with a higher probability of success. It is also worthwhile to seek evidence of extraterrestrial industrial activities; navigational beacons, planetary defense radars, weapons testing, industrial accidents, experimental or accidental energy releases, or perhaps even deliberate attempts to make their presence known, such as the dumping of short-lived radio-isotopes into the local sun. It might not be worthwhile to search specifically for such speculative events, but they might very well turn up in the course of other investigations.

It may be a long time before we make contact, perhaps never. We are almost certainly not alone, but we may never be able to know for sure.


Comments on this entry are closed.

  • Michael Michaud July 3, 2020, 14:05

    This is a useful critique of traditional SETI. However, it makes an argument about distance based on uniform distribution. The nearest civilization might be closer. Other sectors of the electromagnetic spectrum may deserve a closer look. Observations of exoplanet atmospheres might reveal evidence of a technological society that is no attempting to communicate. Searches for megastructures or alien artifacts in our own

    • Carson July 10, 2020, 1:21

      Michael, you’r the man. Good points. So many unknowns. Hopefully astrobiology and exoplanet science helps us with values, parameters and variable.
      I have your books and got started in this subject reading your works and Paul’s. Big thank you to you both.
      Take Care,

      • Paul Gilster July 10, 2020, 6:14

        Glad to have you here, Carson. Michael’s Contact with Alien Civilizations is a core text in the field, packed with insights. A great place to start!

  • Andrei July 3, 2020, 14:17

    Hello mr Henry Cordova, we appear to be on the same page for our chances of finding another civilization. The Fermi paradox already tell us that two types of civilizations seem unlikely to exist nearby. The extremely longlived one that spread slowly but eventually develop into a Kardashevian behemoth with mega structures all over the galactic arm that dump excess energy as easy as we throw away a soda bottle. Neither is the civ that live for a medium long but spread very fast, for the simple reason that Earth was not colonized long ago. And the zoo hypothesis would not be any stopping bloc as mammals or other advanced species only have been around for a comparably short time here.
    But I certainly think it’s worth looking, we could be lucky, and to piggyback instruments or use existing ones for SETI purposes is a very good idea to get the program going for a long time.
    I agree it is a very good strategy to think out of the box as it’s equally unlikely to find an active signal as any ET will know that two way communication will not work with speed-o-light limited radio, laser or unobtanium particles. I can only imagine one civ that would find it economical who find it worth the effort to create such a powerful transmitter. And that would be a race that are about to expire and who have an almost religious idea that their heritage will go on as long as someone remember they once existed.
    So yes I am positive and think a second look of data from other observation programs eventually will provide the holy grail of undisputed data about the activity of an ET civ, the FRB’s did provide some fun speculation for a while. And could be an example of what to look for, though I never thought those were anything but natural. And I got quite unpopular for stating so.
    Any civ that travel between the stars would reveal themselves in one way or other by the enormous energies involved.
    The dismantling of a Jupiter size planet would be a definite sign if found, and at larger distances star lifting would also provide proof of an activity that not happen in nature.
    Lastly, just imagine for fun that the ET civ actually have been here, they did indeed mine a bit in the asteroid belt but decided to leave and left a ½ mined asteroid behind – and lets imagine that this was 16 Psyche.
    On such a world we would find the proof no one could question the validity of, but leave us none the wiser where they came from or if they even exist today. But yes, this was only one amusing speculation on the origin of this very unusual metal asteroid. My point is that I do not doubt there been other intelligent races in this galaxy, only that odds are stacked against us, that we will exist in the same point in time and space.

    • randomengineer July 5, 2020, 16:04

      I am curious regarding the understood requirement for a civilisation to be at a particular Kardashev level.

      For example. Recent rational/sober discussion in the climate world posits potential geoengineering in the form of giant solar shades orbiting earth to block sunlight. One assumes that if we can discuss this now then in say 500 years we humans would be capable of doing larger shades, such as around the sun.

      Meanwhile we can image a lot of stars with what we have now, including weird objects like Tabby’s star. Meanwhile our site host is busy working on technologies that here and now can go to Alpha Centauri. Sober and rational, no Buck Rogers nonsense.

      OK, so in 500 years we also ought to have AI and the ability to send plenty of hardware to Alpha Centauri (or another nearby bright star) wherein AI piloted ships could construct giant orbital shades and keep them positioned fairly indefinitely (along the galactic plane, I assume.) If so then arrangement of shades to block light to yield a pattern of blips of prime numbers ought to be a cheap and effective way of transmitting unambiguously without using Kardashev level energy. It’s just big shades in orbit. This would be detectable at least out to 1470 light years (we can see Tabby’s star at that distance.)

      This is why I’ve been saying that if ET is there then we ought to be able to see stuff exactly like this.

      • Henry Cordova July 5, 2020, 22:56

        You have a point.

        If you don’t care who knows you’re there, its not really that difficult to let them know where you are.

        I don’t know if you’re familiar with the story, but a few years ago astronomers noticed evidence of short-lived radio isotopes in a stellar spectrum. Since these materials had a short half-life, they had to be continuously replenished, and it was reasoned that someone was dumping these materials into this star in order to advertise their presence.

        Eventually, several other stars with these peculiar spectra were discovered in other parts of the sky, and they seemed to be similar to one another in other ways as well. The conclusion was reached that it was unlikely these stars were being artificially seeded with radio nucleides by intelligent beings, but they were the result of rare but perfectly natural internal nucleogenesis processes and convective transport to the stars’ photospheres.

        The point is, that it is conceivable that ways do exist of advertising one’s existence to other civilizations with technologies not that far advanced than ours is. It is not necessary to posit Type III super-intelligences to be able to make one’s presence known omnidirectionally across galactic distances

        Of course, that we don’t see this doesn’t mean they’re not there. It just means they’re further apart (in space AND time) than we’d like.

        I’m sure astronomers would love to have the funding to do this kind of search program, but I doubt they are likely to get it any time soon. Basically, its the same problem we have with radio searches. In order to say for sure that nobody’s probably out there, we can’t generate the will or the effort, even though we have the technology.

        And even if we don’t find anybody, we still can’t say for sure they’re not out there, all we can say is that they’re not common enough to find easily.

        And here’s something else. Even this technique is limited to relatively short distances from Sol. Its only good for our immediate neighborhood. We simply can’t see that far into the galactic disc.


      • Andrei July 8, 2020, 14:45

        Hello Randomengineer.
        Thank you for your nice reply.
        As I understand the Kardashev scale, a civ need to have that level of energy to control, basically at their fingertips and push at a button.
        So the creating of shades around the Sun would not qualify IMO, only a Dyson sphere / swarm would make us get the galactic trophy cup for outstanding achievement.

        But yes, you talk to one very concerned researchers here, and as a desperate but necessary solution we do indeed have such shades on the advanced solution list, and it is one that would work better than to mess even more with Earths atmosphere – suggestions like spreading various compounds in the atmosphere or geneered algae in the oceans which I am strongly against for several reasons we need not to get into here. But such would only be done if things start to get out of hand badly, and we need to make changes to the current energy system anyway – burning oil and coal to make electricity is so stupid it’s laughable. I am actually optimistic we might be able to come trough this in the end, but if the need arise we could find a sensible use for Musk’s silly Buck Rogers rocket. :)

        Yes there’s a lot of weird objects around, Tabby’s star or KIC 8462852 seem to have been explained, though Jason Wright don’t seem convinced yet. Though I agree it’s worth further observations. Even better ones are:
        HD140283 impossibly old, could it have been artificially aged?
        R136a1 impossible mass of more than 265 solar masses, such a star should not form at all but tear itself to pieces before it even got started. Stellar engineering?
        SAO 206462 Might be star lifting caught in the works.
        HE2359-2844 with lead in the atmosphere, this go against every known natural stellar process.
        And I bet everyone here have heard of HD 101065 or Przybylski’s star that break every rule in the playbook.

        Anyway back to those shades you suggest, such regular dips could be observed by any civ with a powerful telescope from anywhere in most of the galaxy – it would be a question of what field of view their instrument got. For a wide field telescope such dips would get lost in noise at some distance, while a narrow field instrument would see the regular signal at immense distance.

        Anyway there’s other ways to signal trough a stellar atmosphere and this is what Henry Cordova mention, and I do think he refer to HD 101065 there. His first words do very much sense though – and I paraphrase that by saying ‘if you don’t care who you send the signal to’ but should we do that? Even though an alien civ might be perfectly in harmony with itself and peaceful, as they need to be to survive very long and not nuking themselves to oblivion.
        That does not mean that they will be equally nice and reasonable toward other civ’s, but like the aliens in Douglas Adams hitchhiker novel, they are all nice plays cricket and write the most beautiful music until they discover that there’s a galactic community out there and the leaders of planet Krikkit decide ‘That has to go!’ and start an intergalactic war exterminate everyone else. The risk that we live in the same time as such a murderous race is unlikely, so I suggest we should keep looking but not broadcasting to find proof of other intelligent life. As a way to get an early warning if something might be threaten us – if that be aliens so advanced we would be nothing but ants to stomp out, or runaway clouds of Von Neumann machines or nanobots. And only if and when we find some kind of proof that the civ is benign should be attempt contact, like for example we find a civ that already are made up of several species or we find they are not aggressively expansionist etc.

  • James Jason Wentworth July 3, 2020, 14:33


    In two words: Bracewell probes. Ronald N. Bracewell’s interstellar messenger probes would, in the broadest sense, also be Pioneer/Mariner-type spacecraft, designed to investigate their target stars and their planets, moons, asteroids, and comets. But in addition to their stellar and planetary bodies fields & particles instrumentation and imaging systems, Bracewell probes would also carry electromagnetic (radio and optical, including close-view telescopic), and spectrographic equipment to search for and contact any local intelligent societies. Bracewell probes could possibly also–depending on their sizes and performance capabilities (and the level of practical miniaturization of electronic and electro-mechanical systems)–carry planet and/or moon (such as ice/ocean-bearing satellites) landers (or submersibles) with Viking-type microbial life-detection instruments.

    • Henry Cordova July 3, 2020, 19:52

      Dear Mr Wentworth

      Thank you for your comments.

      I’ve always found the Bracewell Probe (self-replicating or not) concept fascinating. I find the vision of earth explorers stumbling onto the wreck of an alien machine on an asteroid or drifting in the Kuiper Belt a compelling speculation (especially if it was still equipped with functioning hardware!) Man, that would certainly kick off a new space race in no time flat!

      But if sending messages to suspect worlds is expensive and has little chance of success, sending an actual manufactured artifact would be even more so.

      Still, we need not limit ourselves to something as parochial as a robot probe. That is what WE might do. They, with the benefit of more advanced tech, might prefer instead to send tailored DNA-like molecules encoded with the genetic instructions to create (or infect) local life forms to carry out some agenda of their own. The dramatic productions “The Expanse” (TV) and “Annihilation” (film) speculate on what these biorobots might look and act like. Tailored genetic molecules packed into interstellar dust grains (or Bucky Balls) could be scattered across the galaxy, driven by stellar winds and supernova shock fronts. The time scales would be enormous, of course, but a truly advanced civilization would not necessarily be in a hurry, would they? And being biological (albeit artificial) they would also be self-replicating.

      Perhaps they’ve already been here, infecting the Pre-Cambrian microbial fauna and launching the Edicarian Metazoan Revolution. Maybe our own ribosomes are alien artifacts, manufactured devices with encoded instructions to create a space-faring civilization.

      These are just wild speculations, of course. But somehow it seems more the sort of thing you’d expect from a truly advanced civilization. A rocket with a few antennas and cameras somehow strikes me as unlikely as humanoid saucer people in silver jump suits speaking only- slightly accented English.

      John Fowles’ “A Maggot” describes a manned probe from the future landing in 1600s Britain on some mysterious mission. The locals have no idea what it is, and the crew realize they could not explain themselves to them either. But it underscores the idea that a truly alien technology might not be recognized by us as a technology at all, it might appear to us instead as a religious event, a biological manifestation, or even a meteorological phenomenon.

      Or maybe its been here all along and we haven’t even noticed it.

      • James Jason Wentworth July 5, 2020, 3:13

        You’re welcome. Bracewell probes may not be the most advanced way of acquiring information about other planetary systems and any inhabitants (especially intelligent but non-technological ones) thereof, but if people didn’t make such attempts as soon as technology allowed, they wouldn’t be human. (In the 1960s, there were those who advocated that manned lunar exploration should wait until nuclear rockets, then estimated to be available around 1975 [NERVA was ready to take people to *Mars* and back–but was cancelled–in 1973], made such exploration cheaper and easier. Had their advice been taken, we’d still be waiting for that “One small step” onto the Sea of Tranquility…)

  • Abelard Lindsey July 3, 2020, 15:01

    The emergence of the Eukaryote via the hydrogen hypothesis of endosymbiosis appears to be a singularly rare event and, thus, is the likely bottleneck in the development of advanced life and sentience.

    • Harold Shaw July 4, 2020, 12:52

      Endosymbiosis is not a singular event, but instead describes a diverse spectrum of relationships. The big endosymbiosis events are chloroplasts, mitochondria, and possibly the eukaryote nuclei but they aren’t the only examples. I wouldn’t be surprised if endosymbiosis occurs everywhere abiogenisis occurs and has sufficient time and available resources to produce sufficient variety.


      When we contemplate the potential for complex life developing, it is significant that there are 2 examples of endosymbiosis that formed the base for 2 distinct families of life, plants and animals. Endosymbiosis events that produce complex unicellular life don’t necessarily produce complex multicellular life. Imo though, complex unicellular life and complex multicellular life, including loose cooperatives of cells such as slime molds and microbial colonies can be considered examples of co-evolution. They all exist on a spectrum where the scale of a discrete metabolic system increases. If we consider the problem to be overcome as combining two discrete metabolic systems into one, then endosymbiosis and all forms of multicellularity are different solutions to the same problem.

      When we consider the potential for complex life it is significant that we see multiple solutions to multicellularity on Earth. Perhaps Life can be described as a recursive symmetry of thermodynamics driven metabolism and information theory driven system definition and management. If so, we shouldn’t be surprised if Life frequently or always explores the limits of the probability space provided by the planet. Complex life could be only marginally less common then simple life.

  • Michael July 3, 2020, 15:17

    We always think about the rare earth theory but have we ever thought of rare sapients. Intelligence in my opinion and I bet many others is its extremely rare !

  • Hamilton1 July 3, 2020, 15:18

    One point that seems to be overlooked is that a technological civ can colonise otherwise inhabitable planets. Mars will never have intelligence in the normal course of things – but will if we put it there. Ditto for billions of other hostile planets. And this intelligence could then spread out in ways that might not have happened if left to the host civ alone. Therefore one of the Drake criteria – lifespan of an intelligent civ – becomes meaningless. And the result is many more civs than Mr Cordova presumes.

    • AlexTru July 4, 2020, 2:02

      Wandering, how your “theory” helps to explain Fermi patadox?

  • randomengineer July 3, 2020, 16:07

    Although I expect to be pilloried here I would be happy to state on record that all of SETI is a colossal waste of time and resources. As per my observation about finding ponies in an earlier (celestial exotica) post, it makes no sense that an ET determined to signal would find increasingly obscure means of doing so, that ET would choose the simplest/easiest tech mechanism to be observed with — because it’s the most likely one to be receivable by ET’s target. Catching flies with vinegar vs honey is another way to see this; ET is going to be clever enough to be obvious (honey.)

    If you wander into unknown territory and wish to announce your arrival/presence, you would intentionally choose the mechanism that is the most likely to be noticed. You don’t choose morse code at a UV frequency and expect lions or natives to notice and/or grasp. Nope. You light a fire or grab a megaphone. A simple repeating signal that is in an easily detectable and logical frequency (radio or optical) was how SETI first started looking because this made sense. Still does.

    • alex@4z5lv.net July 4, 2020, 2:13

      I agree that SETI radio listening does not have any logical reason to be successful, but intentional sending radio signals to the void has multiple more chances to be fruitless. In addition we are (unintentionally) radiating to the space lot of artificial signals, that are enough for detection. Problem – the natural communication distance limit caused by speed of light . I am sure there is natural distance limit that make impossible dual side EM waves communication for intelligent species impossible.
      So long time fruitless try to communicate using EM waves – is not the sign of advanced intelligence .

    • Harold Shaw July 4, 2020, 9:48

      Your reasoning assumes that an ETI would want to contact much less technology advanced civilizations. With optical transmitters, an ETI could make their presence known to primitive intelligences. If we allow for ETIs to be selective about the technology level of who they want to contact, your reasoning breaks down. To make your reasoning unbreakable you will need to explain why an ETI would never decide to be selective.

      Business advertising is a decent analog for what I am talking about. Do companies on Earth advertise to everyone or do they shape their message to reach fewer, potentially profitable costumers?

      • randomengineer July 4, 2020, 23:13


        Hi Harold, I don’t think so. Paraphrasing and being concise, I’m saying that if ET isn’t found using the easy low hanging electromagnetic fruit and in obvious frequencies then SETI as we know it isn’t useful.

        Now if you were to posit that ET broadcast comms experts decided on ansible use due to a physical constraint we aren’t aware of yet (e.g. power consumption far lower than electromagnetic spectrum tech would need, etc) then SETI still isn’t useful until humans develop ansibles. So basically, if you want to claim increasing difficulty in our developing the needed comm technologies or flip that to increasing ET selectivity in whom they let join their comms club, at a practical level it’s the same problem.

        Either way SETI as we know it isn’t useful.

        • Harold Shaw July 5, 2020, 9:24

          The only way to solve the dilemma you offer is to know exactly which technique an ETI is using before we search. Apply your reasoning to any other experiment or prototype that doesn’t deliver positive evidence or a working device. In the context of the scientific method, failed experiments and prototypes are never useless.

          An ETI could raise the selection bar using intermittent radio or optical signals. Doing so would select for receivers who have invested in a certain level of SETI. A transmitting people wouldn’t need magical devices to practice selection.

    • Wojciech J July 8, 2020, 8:40

      An advanced ETI would that would be capable of interstellar travel, would also be able to detect life bearing worlds such as ours quite easily as well.Therefore I don’t believe there are any active attempts to signal from local Galactic neighbourhood , it would take too much time and resources when it would be just easier and faster to send a probe(provided of course any ETI exists).

  • Adam Crowl July 3, 2020, 16:42

    Hi Henry,
    Thanks for the discussion. SETI is, by necessity, about the search for communicative intelligences, thus a sub-set of all the kinds of Intelligence that might develop Out There. Your essay is a pertinent reminder of that and the Dysonian approach – looking for visible signs of ETIs – might be the more fruitful option. However astrophysicists are highly skilled at imagining natural processes to fit the data, yet imagining artificial processes is not something they’re trained to do. Jason Wright’s work in this regard, for example, is a welcome change of pace.
    However, I disagree that there’s no evidence for the existence of ETIs – there’s no uncontroversial evidence. There’s plenty of controversial evidence in the field, but it’s unfashionable to discuss UFOs in polite scientific circles. And it doesn’t really change the Fermi Paradox, merely reframes it – if They exist, why haven’t they colonised the planet or made open contact? Human imagination abhors a vacuum, thus “The X-Files”, The Prime Directive, conspiracy literature and the like. More restrained speculations have appeared in the scientific literature, such as the Interdict Hypothesis and the variations on the Zoo Hypothesis. In the absence of solid answers, I think ruling out any option is counter productive.

    • Michael Fidler July 3, 2020, 19:05

      Very good point but open contact could lead to many problems. We as humans have a bad habit of killing off any thing that is considered dangerous or infects our insecurity complex. Remaining anonymous with limited contact would give them time to study and develop ways to deal with the human psychological problems. Giant industrial military complexes, leaders with inflated egos and gun toting morons leave much to be desired with direct contact.

  • Michael R. Watson July 3, 2020, 16:58

    The idea of a million technical civilizations in our galaxy, each lasting about one million years, each associated with only a single star, seems rather limiting.
    Even at sub-light speeds, even a single civilization might spread throughout the galaxy, or a substantial portion of it, within that time. Instead of 100 transmitters around 100 stars, there might be billions.

    Once a fully settled galaxy is considered, with settled worlds established at various times, and each lasting their own million years, the horizons seem to open up a good deal. Of course each settled planet could, in its turn, reoccupy suitable worlds, where earlier civilizations had died out.

    The Earthly analogy would be the way territory has been occupied by one civilization after another, not simply left vacant and silent after a single civilization has gone.

  • Dale Smith July 3, 2020, 19:08

    As a layperson,I don’t understand why an extraterrestrial intelligence has to be an “Extrasolar species capable of constructing communication devices”.Surely dinosaurs were just as intelligent as us,if not more so,and most habitable extrasolar planets with advanced life will be populated by the same.

    • jonW July 3, 2020, 21:37

      Dale, it’s known (from skull size) that dinosaurs had pretty small brains for the most part, and physiological arguments suggest it’s exceedingly unlikely that any dinosaur species could have been “just as intelligent as us if not more so”. Even if they *were* intelligent, like dolphins for example, they would not be relevant to a discussion of SETI, because neither dinosaurs nor dolphins have/had any means of communicating with extra-solar civilizations. If magically we could watch a David-Attenborough-style nature video of non-communicative species on other planets, it would be absolutely fascinating, and you’d have to be insane not to want to study that life. But since there is no way of ever finding out about such species, absent them being technologically capable and interested in communicating with us, any discussion of them is futile and a non-starter. That is why the conversation in SETI is about species capable of constructing extrasolar communications devices, and not because no one would be interested in non-communicative alien species.

    • Henry Cordova July 3, 2020, 22:30

      Regardless of how intelligent they are, if they don’t have radios we can’t talk to them. They might as well not even be there.

      For SETI purposes, the definition of “intelligent” is “they build radios”.

      • Dale Smith July 4, 2020, 18:41

        Thankyou both jonW and Henry for your comments.I understand that there is no way,at the moment,to discover such life if it has no way of communicating.SETI has many subsets-SETA being the most promising IMO,but I think if SETI is to engage with the public more then the message needs to be clearer .I don’t think many people have heard of CETI and it’s a shame because many non scientists would be greatly engaged if they knew the full extent of what SETI encompasses.

      • AlexT July 5, 2020, 1:55

        …if they don’t have radios we can’t talk to them…

        It is huge illusion to think than if ETI have radio, so we can communicate them.
        Using radio (or other Electromagnetic wave band) we can communicate only with relatively close worlds (something located in the sphere that has radius of tens light years ).
        With more distant civilizations we do not have any chance to communicate (using radio).
        It is traditional SETI fairy tales – communication with ETI, that is absolutely disconnected from our current technological ability.

  • Douglas Phillips July 3, 2020, 20:03

    I’ve often thought SETI scientists should read more science fiction! We sci-fi authors let our imaginations run wild every day, and while we might now and then get into trouble with the Physics Police, we regularly stretch the boundaries of what might be possible. The gaping hole in the Drake equation is fc, the fraction of civilizations “capable of communicating”. But what is “capable”? SETI is stuck in the electromagnetic messaging rut, because “that’s all we know” – and therein lies the whole problem. I would argue we are NOT capable. There is some technology yet to be discovered that will open the door for humanity. Once we discover it, we’ll be slapping our foreheads for wasting decades wondering why our silly smoke signals never caught anyone’s attention, or why we never saw their own puffs of smoke. In 2017, I wrote Quantum Space as my take on this question (it has now been read by more than 50K sci-fi enthusiasts). https://www.amazon.com/dp/B06ZY9T5Y5. I’m happy to provide a free copy to anyone involved in this topic. I’d love to get your take on it.

    • AlexTru July 4, 2020, 2:29

      I agree that we are not capable for interstellar communication, the way as we are using electromagnetic waves for communication is useless on space distances and could not be used by advanced intelligence for long distance communication.
      Problem – we do not know any alternative communication technology, our science prohibits faster than speed of light information transfer (please do not remind here quantum entanglement , fruitless hope for wishful thinking)

      • Douglas Phillips July 4, 2020, 23:00

        Agreed. Electromagnetic communication (radio/laser modulation/etc) is utterly useless over galactic distances. It’s one an only purpose would be to signal “we are here” to anyone who might pick it up. But back and forth communication is absurd, even if two civilizations are “neighbors” at a few hundred light years away. Given the consensus is advanced civilizations are rare, a few thousand light years is more likely. It’s hard to know how we might break through the light-speed barrier, but that’s where our imagination comes in. It’s not purely fiction, either. Kip Thorne has imagined how it might be done.

        • AlexTru July 6, 2020, 3:16

          1. I do not deny absolutely that there could be found some way to overcome seed of light limits, but our present science does not know how…
          2. Even one way ETI message sending – dies not have any intelligent reasoning (only wishful thinking reasons). Every planet that rotating around it’s host star isotropically radiating (reflecting) significantly more electromagnetic energy, than our SETI activists can imagine…
          So we will be able to detect ET life or intelligence remotely only when we could make direct imaging of remote world using advanced astronomical instruments. By the way, the Instrument that will be able to resolve direct image of remote world, will be able to detect different artificial signals from ETI.

    • Ross Turner July 7, 2020, 20:43

      Hi Douglas, I read your book and really enjoyed it. I liked the scientific background you provided and learned a few things along the way. A really good read for anyone here that is interested, and free on amazon.ca as well.

      I agree with your take on communication, we are probably not looking in the right direction. EMR is far too slow for any space faring species to use to communicate with one another. I also suspect that expanded consciousness might have a role to play here. I know its a subject not usually talked about or even mentioned on a science forum, but my guess is unless we can get our own consciousness upgraded somehow, to a higher level, as a species, we aren’t going anywhere. Our current technology level has gone beyond our ability to use it safely. Anyway as with all other opinions here, it’s a guess. We simply need more information before we can draw any concrete conclusions.

      Thank you for writing that book. I can’t wait to read the next one.

  • Brett P Bellmore July 3, 2020, 20:30


    Are we conflating SETI and METI? I can’t see why the *search* would necessarily be energy inefficient, if limited to simply listening on every available channel.

    • henry cordova July 3, 2020, 22:25

      Even passive SETI requires an investment. To have even the slightest probability of picking up a signal, you have to listen to many, many stars, for a very long time. Thousands of radio telescopes? Millions of years? To paraphrase Carl Sagan; ” You can walk a beach in a few minutes, but how long does it take to examine every grain of sand?” It is important to remember that even if many worlds evolve into transmitting cultures, they will not all do so at the same time. They are far apart in time as well as space. The Galaxy could eventually contain millions of broadcasting species, but most of those worlds would have been silent for billions of years until communicating cultures evolved there.

      Switching back and forth between worlds or between frequencies wouldn’t necessarily help either, because it ignores the advantage of integrating the signal, that is, listening for a long time, as with an optical time exposure, to improve the signal to noise ratio.

      If you are shipwrecked on a desert island, throwing bottles with messages in them into the sea is not an efficient way of attracting rescuers. Unfortunately, it may be the only way we have available to us.

  • Kamal M Ali July 3, 2020, 21:02

    I cannot understand why people assume civs will embark on an insane spreading program through the galaxy. Or that even if they do, they will be successful: we’ve all seen how civs have a lifecycle: they often fail. Maybe it’s exceedingly unlikely for any civ to make a machine that will successfully last a thousand years and enter orbit around another star ? Spreading bio-seeds seems much more likely to succeed.

    I am struck by the difference in our one-shot philosophy (make a large spacecraft) versus nature’s massively distributed ways of doing things. Maybe to make things that last millions or billions of years, one-shot is simply not going to work. I’m thinking instead of spreading via millions or billions of very simple craft – maybe just seeding the universe.

    • Michael R. Watson July 4, 2020, 10:18

      There seems to be nothing extraordinary, and certainly nothing ‘insane’ about an interstellar civilization expanding beyond its home world, and extending its territory throughout the galaxy. This is the basis for the thinking around the Fermi paradox.
      Expansion of territory is very common in a wide variety of species on this planet. Our own pre-history is a very good example of this. From one small corner of Africa, the human race managed to fill the entire inhabitable space of this planet in a few hundred thousand years.

      • Henry Cordova July 4, 2020, 14:11

        I’m not sure I agree with you.

        Why would an alien civilization even want to settle another planet? Any culture capable of interstellar spaceflight wouldn’t need a planet, it would be perfectly capable of building solar powered orbital communities and not need to go to the trouble of terraforming or adapting to new worlds. By the time interstellar travel becomes routine, we probably won’t be living on earth anyway.

        A culture could conceivably want to leave its home system if it felt it was threatened, or if they had polluted it beyond repair, but one asteroid belt is pretty much like another. A true space-faring race doesn’t need planets, it needs plenty of energy and matter, and enough dispersion to protect its population and culture from extinction.

        The idea of leaving a world and colonizing another just doesn’t hold up. If you have the capability of interstellar flight, you can live anywhere you want. Going to Alpha Centauri to grow turnips or hunt whales is going to be a hard sell to asteroid miners or ice moon prospectors..

        Even in our own case, the whole idea of moving to a planet round a nearby star and homesteading it is absurd. By the time we can colonize a planet ten light years away, we will all be living in orbital habitats and we won’t need planets. The Earth will be either a smoking ruin or a national park.

        What I do foresee is a far-thinking civilization realizing that its planet’s (or solar system’s) habitability was not guaranteed forever, for whatever reason, and its orbital habitats were potentially threatened by stellar evolution or cosmic catastrophes. In that case, it might be wise to place colonies around nearby, stable stars with the energy and material resources to build more orbital habitats. But actually finding (or terraforming) a duplicate of the home world would not be necessary, or even desirable.

        All a truly advanced civilization really needs is ice, rock, and plenty of sunlight. And I suspect most stars already have plenty of that. I don’t foresee galaxy-spanning empires, I suspect once any civilization ensures its longevity by settling a few nearby stars, it will stabilize and concentrate on other pursuits. This is another good reason to look closely in old open clusters.

        • Douglas Phillips July 4, 2020, 23:22

          “Why would an alien civilization even want to settle another planet?”
          We must all broaden our thinking beyond 21st century human culture. It’s hard for us to imagine other ways of existence, but we can try. Why would an alien civilization seek out other planets?
          1. What if the home planet is slowly changing, becoming less habitable? Strong motivation to leave! It’s essentially the same reason birds seasonally migrate, sometimes thousands of miles at great cost to the flock.
          2. What if their science discovers inviting targets? The effort of building transportation is always going to be lower than the effort of constructing a habitable pseudo-planet from scratch.
          3. What if the life form benefits from abundance? A little is good. More is better. A lot more levitates the species to a new level. Take the light spectrum for example. A life form might flourish in infrared. They could scrape by on an Earthlike planet, but would blossom on a planet with stronger infrared.
          4. What if we don’t know all there is to know about life? About travel to the stars? About constructing orbital stations? And about terraforming? A thousand years from now, the 21st century will seem primitive.

        • Eniac July 4, 2020, 23:54

          Spreading out over all available living space is not some conscious decision that a “civilization” (species is a better term) makes based on careful reasoning. It happens because there are individuals that wish to get a way from the powers that be and start a fresh life somewhere else. Not because the grass is greener, or the asteroid belts thicker, but because they are not yet ruled over by someone else. Even trees spread all over the Earth, obviously without making any decisions on how much sense it made. It is inevitable, and any species that achieves the capability to settle neighboring systems will inevitably spread across the Galaxy. This transcends the whole SETI paradigm: The first species to jump this hurdle will propagate indefinitely. Drake’s L is infinite, and the spatial spread is not even in the Scope of his equation.

          • Harold Shaw July 5, 2020, 10:14

            What happens when unsettled space dwindles? If you are right and the desire to expand is an immutable libertarian passion, there will be war. Resources that could be spent on expansion are spent instead on war, limiting the rate of expansion. Either immutable passions self regulate how far a people can spread or immutable passions aren’t immutable and a people can apply reason to their expansion plans.

            Brainless trees creating a forest is a weak analog for a space faring people colonizing a galaxy. You can’t discard the impact reasoning and consciousness has on a process that couldn’t exist without sophisticated reasoning and consciousness. The potential of biotechnology can’t be ignored either. A space faring people don’t have to be driven by instinct, they won’t have to dominate the galaxy or reproduce to survive. Creating new people could be a liability for instinctually libertarian persons.

            Depending on lifestyle, a people could spread across the galaxy without filling every corner or niche. There could be trillions of spaceship people spread across the Milky Way and we may not see them because they only occupy a narrow niche.

            • Eniac July 6, 2020, 16:58

              As unclaimed territory runs out in the galaxy, the reason to colonize will cease. Given light speed limitations, war isn’t really practical over interstellar distances, so war will be restricted to be between different factions within the same system. Invasions will be impractical, because the defenders will have a huge logistical advantage over an invasion fleet that would have been decades in transit.

              Trees are a minimal example, to show that the bar of “will” or “reason” is incredibly low. It is hard to imagine a society so unified and strictly regulated as to not allow even one faction to pursue colonization. Even if that was possible, it would have to be the rule rather than the exception. Even a single faction in a single system is enough to keep the process going.

              With light and dirt being the only resources a space-based species needs, it is hard to imagine the “niches” you speak of. My original reasoning suggests that any unoccupied stellar system will eventually be targeted for colonization by at least one faction on one of the surrounding settled systems, so they will be occupied soon enough.

              • Harold Shaw July 7, 2020, 9:07

                Hello Eniac and thanks for responding. It is good to see you back.

                I agree that people will expand from their home system, but I don’t see expansion leading to a fully colonized galaxy that leaves no room for other people to emerge as a space faring people.

                I don’t think an empty system is responsible for a people’s desire to colonize. You were right in your first post that it is the people who produce the drive to spread. Whether it is the urge to explore, have an adventure, start a new kingdom; all emerge from the people. What happens when a people can fulfill the urge to explore or adventure by becoming a living spaceship? What happens to the urge to have families when a people can be immortal? I am not arguing that people won’t have urges, but that those urges don’t have to produce a galaxy stuffed with civilizations resembling our own.

                With biotechnology, a planet could be sterilized without much effort. Your vision of interstellar conflict is too narrow.

              • Wojciech J July 8, 2020, 9:25

                It is really doubtful if an interstellar civilisation would expand ad infinitum. One, space is incredibly vast, and our own Solar System could support trillions of humans for eons. Two, as your technology grows, you gain control over your biology and the need for reproduction is greatly diminished. Three, vast interstellar empires are impossible due to time lag, so besides some tight star clusters that communicate between each other there will never be some unified form of governance.
                It is most likely that any advanced civilisation has long abandoned needless continuous reproduction in favour of longevity.

                • Eniac July 9, 2020, 11:00

                  One, no amount of vastness is a match for exponential growth. Two, it is not about reproduction, it is about spreading out. Three, no empires are needed, as demonstrated by the trees.

                  • Wojciech J July 15, 2020, 15:01

                    We are not talking about bacteria in petri dish, but self aware civilizations capable of modifying their own biological nature, moving through vast and highly hostile environment.
                    For the record our civilization is likely to experience a crash in population growth already(and we haven’t even started tinkering with our genome yet!)






                    • Eniac July 16, 2020, 15:00

                      The only way the “biological nature” of wanting to spread out could possibly be suppressed is a global, absolute and perpetual tyranny. And even then, there is not really a good reason why someone would even want that.

                      Population growth, while a possible contributing factor, is not necessary for expansion.

          • Henry Cordova July 5, 2020, 11:00

            “Inevitably” is a term we should be very cautious about using when referring to extraterrestrial beings, whose existence, and indeed, very possibility, is totally speculative.
            Even the concept of of a collection of “individuals” is hopelessly parochial. We don’t know that about them..

            Aliens, if we ever meet them or communicate with them, will be totally unlike us, although no doubt we may notice some similarities. That’s all we can say for sure. In fact, that’s why we are all here, because we recognize that.

            • Eniac July 6, 2020, 17:09

              You may be right, and all alien species would be very content to constrain themselves forever to their one home, despite being surrounded by dozens of other reachable potential homes. But it is a very hard argument to make that there are many of those, and that they are ALL like that without exception. Your only way out would be that, somehow, the “reachable” I used above is wrong, i.e. interstellar colonization is impossible. I do not believe that is the case.

          • Alex Tolley July 5, 2020, 12:10

            I agree. competition is most acute between individuals of the same species inhabiting the same niche. When the geographical expansion is possible, individuals gaining the ability to increase their range to be freer of the competition will thrive.

            Human expansion has similarly due to competition between individuals. The drive to colonize Mars, whether from Zubrin or Musk, whatever the stated motives, still come down to escaping the restrictions (competition) from existing social systems. Both individuals have a strong libertarian ethos that is quite clear.

            If life can be sent by directed panspermia to other worlds, I see that as quite natural, even if done for “altruistic” reasons by those who will not directly benefit. Greening habitable, but uninhabited, worlds will allow our species to benefit should passenger interstellar travel ever become possible. If not, then at least we have sown the seeds for other civilizations to potentially emerge. I don’t think we need to expend huge amounts of resources to achieve this, as long as we keep velocities and payload sizes low. Rather than slow world ships, we could send millions of tiny “life ships” with organisms in some sort of stasis (e.g. dried, frozen) to colonize and evolve on these worlds. It may take many millions of years to reach each target, and perhaps hundreds of millions of years to create rich biospheres, but it should be doable. Perhaps send 1 per year over a million years, a cost that is trivial. Or send many per year at a higher cost, commensurate with the size of the seeding budget. At just 1/10% of c, 300 km/s, the farthest stars in the galaxy can be reached in 100 million years. It is a long-term project, but certainly manageable for a long-lived civilization.

            • Douglas Phillips July 5, 2020, 22:42

              Either a) we’re the only life in the universe, or b) any planet that is “habitable” WILL be inhabited. There won’t be any planets that are suitable for life that don’t currently have life. So, I think we can forget about finding that perfect Earth twin that doesn’t happen to have any life on it.

              • Eniac July 6, 2020, 17:25

                Only in case of b). In case of a), there will be plenty of planets of all kinds with no life on them. Chances are, though, that travelers arriving after an interstellar journey won’t need or want planets.

              • Wojciech J July 8, 2020, 9:30

                There won’t be any “perfect Earth twin” because each planet has its own unique atmospheric and solar conditions, geology.
                It is more likely biospheres would be left alone anyway as they are more valuable as source of research and uniqueness than colonization. Colonization itself becomes unnecessary as your species manages to overcome its biological limits and space habitats become better options than planets for living(and you already know how to create them if you have spaceship capable crossing vast interstellar distances).

                For these and many other reasons I don’t believe in the concept of “galaxy spanning colonization”. It is simply unnecessary and wasteful.

                • Alex Tolley July 8, 2020, 12:52

                  It [galaxy spanning colonization] is simply unnecessary and wasteful.

                  However, it may be the most resilient way to ensure no catastrophe that could await a K2 civilization. Distance might also be teh best protection against unwanted conformity of governance.

                • Eniac July 9, 2020, 11:49

                  Your use of “galaxy spanning” suggests that you think of colonial spread as some collectively organized effort. It is that no more than a recently germinated sapling has grand thoughts about covering the Earth with trees. The maximum effort involved is that needed to bridge the gap between neighboring systems, around 5 light years. Once the technology exists, any sufficiently powerful faction (e.g. nation) in any inhabited system can undertake the effort without a need to cooperate with the others. Likely, because there are only a limited number of close systems, there will in fact be competition to expedite the process. The galactic scale comes from simply repeating that process, like bacteria that keep dividing and eventually spread over the entire Petri Dish.

                  • Wojciech J July 15, 2020, 15:13

                    Why should they? Also what if the nearest habitable planet is 1500 light years away? This is also a possibility.
                    In any case, our own civilisation is limiting its growth.There is no reason to believe we would behave like bacteria in petri dish(which the universe is not)

                    • Eniac July 16, 2020, 15:07

                      A true spacefaring civilization can thrive on starlight and asteroids. It does not need planets. Because every star system has both in large amounts, 1) the next target is always ~4 light years away, and 2) the galaxy is in fact a petri dish.

            • Eniac July 6, 2020, 17:19

              I am not sure it is practical to send life to other star systems without also sending sophisticated machinery to survey the system for suitable locations and actively start “planting”. It is almost certain that such machinery would also be sent ahead of any colonization, to survey the system and prepare habitats. In a way, the presence of such machinery already constitutes colonization, especially if they are operated by AI systems that can be considered descendants of the species that sent them.

      • Marc July 4, 2020, 15:07

        A species that relentlessly expands its reach by exploiting technological advantage to kill and enslave millions of others might be viewed as inherently ‘insane’. Yet, here we are. Perhaps we are the outliers.

  • Thomas W. Hair July 3, 2020, 23:50

    “I wish to go on record as saying that conducting passive searches for alien communications is a waste of resources…”

    Henry, I agree with your comments. The space and time conundrum is a tough nut. If they exist at all, and it would be nice to know we are not alone, then I think they will be very ancient and not a culture or a civilization, but simply an intelligence. I don’t know exactly what that means considering the speculative nature of these sorts of discussions. However, considering the geologic epochs they may have been around before us suggests to me that if we detect them we may discover some very deep time information on how the current 7.8 billion of us and our descendants will proceed into our own deep time.

    • Harold Shaw July 4, 2020, 13:20

      Just one intelligence?

      I agree that intelligent civilizations will explore the landscape of cognition. Such a people will exhaust explorable space and science before they exhaust the landscape of cognition. As well, an intelligent civilization is likely unlock the tools to explore cognition before they have colonized their own star system. Humanity will.

      I disagree that exploration of cognitive space leads to a Singular Super Intelligence. Cognitive space inflates through the interactions among discrete cognitive states. People who want to explore cognitive space will demand inflation and resist the emergence of a singular cognitive state.

      One of the key problems of SETI is predicting the hardware an ancient people use to explore the limits of cognitive space. That isn’t a small problem. Dyson has some suggestions but we shouldn’t be confident he got the right answer.

  • Alex Tolley July 4, 2020, 0:03


    The evidence for any extraterrestrial life is also, at this point, non-existent. Hopefully, we will have proof within a few decades that life is generally common. But until then, Earth could be the sole abode of life in the universe.

    • James Jason Wentworth July 8, 2020, 12:46

      I wouldn’t say that evidence for extraterrestrial life is *totally* non-existent. The Viking lander data (particularly, but not only, from the Labeled Release experiment), looked at again with our greater knowledge today, suggest that microbes may well have been detected (and there are organic molecules in the soil, which Viking’s less sensitive instruments couldn’t detect). If nutrients of both chiralities had been sent (this was planned, but was reduced to one [and Wolf Vishniac’s “Wolf Trap” microbe detector was deleted] for budgetary reasons), we could know for sure. Also:

      The sub-ice crust oceans of some Jovian and Saturnian moons would be comfortable environments for terrestrial microbes, and we haven’t even begun to explore them. It would be very surprising–and in a sobering way, because of the ramifications of such a discovery (what you alluded to above)–if those satellites’ oceans all proved to be sterile.

      • ljk July 13, 2020, 9:37

        In regards to Viking I am guessing they did not have the technology for a small camera inside that $60 million automated biology laboratory inside those two landers circa 1975? That might have solved several decades of debate.

        Correct me if I am wrong, but I am also amazed that they did equip the Viking landers with sensors to determine the mineral composition of the surface. That might also have resolved lots of debates and arguments about native life forms.

        NASA and others have spend decades tip-toeing around the life issue after Viking. I hope the upcoming rovers will finally resolve the issue.

        And no more declaration of water! We get it, Mars has and had water. Now let’s get bolder – again.

  • Alex Tolley July 4, 2020, 0:23

    For any long-lived civilization, like your million-year-old hypotheticals, will have to be economically stagnant. The equivalent of a Malthusian condition for economic activity. What does that do for a civilization?

    By comparison, terrestrial species live for perhaps a million years on average, as they do not engage in economic growth, but are strictly limited by their ecosystem. Perhaps the only long-lived species are not intelligent enough to design systems that engage in growth by resource exploitation. The longest-lived terrestrial civilizations existed when economic growth was about 0.1% on average. Even these civilizations eventually exhausted themselves or fell victim to younger civilizations.
    Our industrial civilization is barely 300 years old, has become global, and is in danger of collapsing not just human civilization, but many ecosystems with it. Just possibly, the most rational approach for “communication” is to green the universe with terrestrial biology, where all but a tiny fraction ever become technological and continue the greening expansion before they too collapse.

    We may be the prime civilization in our galaxy, even the universe, or we may be the beneficiaries of an earlier civilization’s greening. I doubt the latter case, as it makes no obvious sense why the Earth would have been seeded only with bacteria, when it could have also been seeded with eukaryotic life, possibly even with multicellular life, reducing the time for evolution to reach our stage by billions of years. So it might mean we must be the first, and that the Fermi Question is simply because we are alone.

    • Henry Cordova July 4, 2020, 8:37

      I prefer the term “stable” to “stagnant”. Lets not let our choice of words guide our pattern of thought. It would truly be a tragedy for all sentient life if uncontrolled predatory resource exploitation was the indicator for civilization. I would like to think a truly advanced culture would be able to manage its economy and environment in a more rational manner than we have. Besides, the technology, abundant energy and material resources of a spacefaring species, (not to mention plenty of empty space to dump its wastes) suggests a truly ancient society would have had the time and experience to resolve the contradictions of primitive, toxic, slash and burn agriculture and industrial capitalism.

      I do agree with you that ultimately, the “greening” of the Galaxy may be the ultimate goal of a truly advanced culture, with plenty of time, resources and wisdom to ensure a cosmos friendly to itself and diverse enough for others to flourish. In my response to Mr Wentworth’s Bracewell Probe post above I mentioned just such a Panspermic approach. Sorry about the choice of words, but “Panspermia” is really just an old-fashioned alternative to “Bracewell”.

      Scattering engineered genetic material on the solar winds and spreading it around with radiation pressure and gravitational tides may be one way to do it, if time is no object. Maybe that explains the Cambrian Explosion. The clues to ancient galactic cultures may not lie in space, but in our own world’s nucleic acids.

      Still, these speculations get us nowhere. If we are really interested in finding ET, our best bet for the time being is funding astronomical research. Sooner or later, those guys are going to stumble onto an observation that cannot be explained as “a natural phenomenon”.

      I just hope it happens in my lifetime, and all the reasoning in my essay can be demonstrated as false.

      • Alex Tolley July 4, 2020, 18:40

        I prefer the term “stable” to “stagnant”

        Is it possible to have a “stable” economy? Expansionist economies will overturn stable ones. When economies fail to provide positive ROI, they start to decline. This is inevitable in any economy driven by requiring positive ROI to invest in change. Human history, under a wide variety of political and social systems, shows that civilizations rise and then fall. Without competition, some maintain some stability for a period, but eventually, they collapse. While it is possible we could design a more stable type of economy that will continue, it is far more likely that long term stability comes from a succession of civilizations that rise and fall. Can ETI do better? Perhaps. The motivation to continue to develop technology will have to be non-economic, perhaps more like other cultural pursuits like science.

        Bear in mind that we need economic growth to support our endeavors to engage in interstellar communication and travel. Are we to reach some high level of development and then cease growth? I don’t see it myself. Either human nature has to change, or we must be replaced by a different species, perhaps machine-based. The later I don’t see as wanting to seed the universe with life.

        • Henry Cordova July 5, 2020, 10:51

          Human nature? We are trying to speculate on the motives and actions of non-humans. We’re bound to make mistakes because of our limited experience, but we can’t really judge the future behavior of alien species by assuming they will behave like terrestrial primates fresh off the savanna. Galactic economies will not “have” to resemble mercantilistic or capitalistic models that have only lately (by even terran historical standards) appeared on earth. What if they act and think like social insects instead of inquisitive and acquisitive monkeys? What if they have evolved totally different social and psychological motivations than our own culture(s)? Isn’t it likely these differences will result in very different politics and economics than ours? Imperialism and competition, military or otherwise, may be rampant in the galaxy, but the one thing we can be sure of is that it will not look at all like the models our own history offers us. It won’t be like Commodore Perry’s black ships anchored in Japanese harbors.

          Competition, Return on Investment,” expansionist” economies overpowering and replacing “stagnant” ones. …Were talking about aliens here, not Junior Chamber of Commerce Republicans. And these aliens may never even meet us, even our exchanged messages may be unintelligible to the other. Sure, these modern economic terms can often be applied to the behavior of biological yet non-sentient collectives, but only as metaphors and models, not as natural law.

          Extraterrestial intelligences are going to be VERY strange. We may not even recognize them as being intelligent. They may not even recognize us as being intelligent. Our best hope is that we won’t be the first one they’ve encountered, so only one of us will be totally ignorant of what to do next.

          • Alex Tolley July 6, 2020, 12:30

            Life has its own ROI, increasing biomass to use every resource it can until it reaches its resource limits for a particular habitat. This drive can be across species as with ecosystem succession (lake->meadow->climax forest). It is no different for humans, and it is irrelevant that we happen to be a primate species. The same would happen with a non-primate intelligent species.

            Currently, terrestrial life is limited to Earth, but it must expand to new environments to become interstellar. Without that expansion, in our case with an organized economy, that cannot happen. If we “stabilize” within our current resource limits, then we will not be able to build an interstellar civilization. Historically, terrestrial cultures reach some resource limit, typically food, which eventually fails for a variety of reasons, and that culture declines or collapses. That decline may be due to another culture invading to acquire those resources for itself. Biology and our need for chemical food may limit our ability to expand our biomass, but this will not be a constraint for our robots that can feed directly off sunlight with simple means to convert it to the energy they need.

            Any alien civilization, however it arose, must go through some pattern of growth to become an interstellar one. But it will face the same resource constraints as we do, with the same imperatives as life to expand up to those resource limits. Like life, it will evolve its systems to maximize its economic outputs against the inputs it has. It will also face incursions by newer, expanding civilizations that wish to acquire new resources. I do not see some utopian situation where this never happens. It may be a unipolar galaxy (universe?) with just one diverse civilization. It may look stable for long periods of time, but like life, it will keep evolving its components, whether biological or machine. Indeed, that is how resilience is built-in, through diversity and every changing components to fight against the forces of entropy.

            Does such a civilization need to evolve? Just consider what might have happened if one of our cultures/civilizations had never disappeared but remained the sole example. While it is tempting to think that the Ancient Greeks would now be more advanced than us, that is purely speculative. Civilizations have typically expanded, reached a peak, then become rather static. Fortunately, they also decline or are replaced by new cultures. This cycle paved the way for our current civilization. It will likely similarly be replaced by the next, which, after more cycles, will result in one reaching greater heights of achievement. The major fly in that ointment is that our culture has “cheated” by using more energy than that currently provided by our sun. Currently, we use fossilized solar energy, with a dose of nuclear provided by other stars, and eventually fusion. Ultimately, the best we can imagine today is to become a K2 civilization. Beyond that we must become interstellar, growing our civilization until it meets the limits of our galaxy. This phase would take millions of years and our species would evolve and speciate while doing so, replicating on a galactic scale, the changing composition of species and ecosystems of Earth.

            What has this to do with your thesis?

            because time particularly separates civilizations, if there is ETI out there, it will likely have had teh time to expand to fill everywhere in the galaxy where energy can be acquired. That implies they should be everywhere, in whatever form they take – biological, machine, transcendent “mind-stuff” We may not recognize them, but they must be there. Or not, because we are the first. Worse, the universe is strewn with galaxies, where we assume surely one has a civilization that has reached K3 stage. So far no signs, although we may not recognize it. Or again, not, because we are the first.

            If we are the first, then SETI, METI, and even CETI, will prove fruitless in that we will be forever unable to get a positive response. If there is a K3 civilization out there, then they will be aware of the lightspeed constraint for emerging civilizations and will have to send emissaries to interact with us locally. Either that, or there is an FTL communication mode that they expect new civilizations to discover and join the galactic club. But why not find ways to signal their presence by means we can detect, like light? The last option is that they are there, but due to chance, they are still in the expansion stage, somewhere else in the galaxy and out of sight. But if so, why can we not see a more advanced civilization in another galaxy that is expanding or has become a K3?

            The simplest explanation that fits the facts is that we are the first. Human cultures seem to want to invent “others” (gods, fairies) where none exists. We want to talk to the animals around us. I suspect we wish that ETI was out there so that we would not be alone in an indifferent universe. Like extraverts going crazy in self-isolation during the pandemic, humanity wants to communicate with others. It may just be wishful thinking.

            • Henry Cordova July 6, 2020, 21:46

              “Civilizations have typically expanded, reached a peak, then become rather static.”

              Perhaps that is the wrong way of looking at things, guided by how we wish to see ourselves, as bold, entrepreneurial, kick-butt innovators. Maybe the truth is most human communities seek stability, peace, comfort. It is only the ones who are permanently and psychopathically aggressive, or who go temporarily berserk, or who undergo fits of avarice, or “expansion” (to put it more charitably), that we remember and sing about in our histories. Most of the time, until finally forced by external stresses, human communities remain stable and peaceful. The bloody pageant of human history is mostly the catalog of short, bitter traumatic conflicts, not the long periods of quiet and peace between them. But that’s human history, primate behavior, not a law of physics.

              If there is conflict, and if it is indeed a result of our hard-wired biological architecture, then our competition will be like that of most animal species: limited, ritualized, brief, and mostly non-lethal skirmishes confined to boundaries and frontiers. The alien ships may well be heavily armed, but they won’t come in battle fleets. Only a fool ventures into the unknown without a weapon, but it takes a real idiot to go out spoiling for a fight.

              In an environment where a civilization can spend millions of years without knowing of its nearest neighbor, and where resources and Lebensraum are plentiful, things will go differently than on a small crowded planet without enough resources to go around.

              No, I’m not saying ETIs can’t be xenophobic murderous robber barons and imperialists. I just think we can’t really expect them to be that way, either.

            • AlexTru July 7, 2020, 2:27


              Sorry, but (knowing homo sapience psychology) I cannot imagine scenario when SETI (meti, ceti) actors will recognize that search results are negative and we are alone.
              There will be always “consensus” among SETI that we should continue .
              I.e. SETI will never recognize negative results, I know SETI activists are frequently using this argument, but it is hoax…

            • Wojciech J July 8, 2020, 9:41

              A K3 civilization is sadly impossible to achieve, as it would require FTL communication. A pangalactic society simply blocked by physics.Time lag and distances would make any attempts to operate it fail.

              • Alex Tolley July 8, 2020, 12:41

                You assume 2 things:
                1. That civilizations must operate on timescales similar to humans. That need not be so. There are various means to obviate that and allow what appears to be reasonable communication across teh galaxy.
                2. FTL communication cannot exist.
                3. That a K3 civilization must be cohesive like a nation-state, rather than highly distributed in operation and governance.

                Without one or more restrictions, a K3 civilization is quite possible.

                • AlexTru July 11, 2020, 2:21

                  Speed of light limit is very serious factor, our science still do not have any scientific evidence that FTL information transfer is possible.
                  So it is not scientific approach to try to build scientific theory using wishful thinking and non scientific arguments (FTL), in same time it is good for Sci-Fi literature. I like Sci-Fi as well as fantasy or folklore fairy tells, but distinguish it from reality.

                  • Alex Tolley July 11, 2020, 11:41


                    I agree. However that neither proves FTL is impossible nor that it cannot be used as an example constraint that may be invalid.

      • Douglas Phillips July 4, 2020, 23:36

        Agreed, astronomical observation is our near-term hope. I’m excited by the prospects of exoplanet spectral analysis. We may find O2 in the planet’s atmosphere – a good indicator of life – or we could get lucky and stumble upon an unnatural molecule that could only be explained by intentional chemistry from a scientifically literate species. This has much higher chance of success than electromagnetic communication.

        • Ramses Ramirez July 6, 2020, 19:51

          This is the reason I am currently more optimistic about astrobiology than SETI+technosignatures. Astrobiology is better formulated and its inclusion of “simple life” significantly increases its chances of success. SETI, if anything, has shown that there is not much happening nearby, at least in the wavelength regimes we have been able to assess. However, as Henry’s essay underscores, we need to improve the way we do SETI (including technosignatures), but focusing on more generic ways of searching for life. IMHO, nearly all proposed SETI+technosignature techniques are far too anthropocentric and myopic in vision (although I am intrigued by the “waste heat” idea). Whoever is able to devise a viable agnostic search method (both in economics and probability of success) would have truly advanced the field.

    • Harold Shaw July 4, 2020, 11:01

      Mature biotechnology will transform the economics of resource exploitation and property rights. Economic agents could be functionally immortal and individuals could exploit the resources of a star system. The population of an ETI civilization, or humanity, could shrink and still expand to fill the galaxy. Trade within a civilization could shrink and expansion would still be possible. A Malthusian crisis could still exist but it would be defined more by the limits of physics and agent personality and less by an economic system.

  • Law Wong July 4, 2020, 2:24

    If civilizations don’t travel, the logic is sound.

    The traditional paradox argument is that a single expansionistic starfaring species would have colonized the galaxy within ten million years. In my opinion, that’s where the Fermi paradox becomes scary, since it suggests that interstellar settlement or even large-scale interplanetary civilization is virtually impossible – which may well be the case. Space is boring, deadly and empty, and the actual benefits of expansion are rather limited (negative, in many cases) in the short and medium term. The incentives for large-scale interplanetary and interstellar civilization seem very limited from our perch (and to be honest, that is what matters).

    Not exactly a happy thought for those hoping for such developments to come to pass (myself included), but then again reality is not supposed to conform to ideology.

    • AlexTru July 5, 2020, 1:39

      It is very wrong and unscientifically approach to make conclusion from Fermi paradox that interstellar travels and expansion is impossible.
      Because there are very simple and obvious explanations for this paradox:
      1. We are alone (in limited by hundreds/thousands light years volume)
      2. We are most technologically advanced
      3. Among wide diverse of ETI civilizations, Our, technological , civilization is unique , other species are going different way.
      If I could accept your point of view , so I could conclude that sea (ocean) traveling is impossible, fallowing this logic – Columbus should never go to long see travel to look for alternative way to India, because none arrived to Europe by sea ways :-)
      I.e. Fermi Paradox is not frightening and does not mean automatically that interstellar travel and/or interstellar civilization’s expansion are impossible…

  • AlexTru July 4, 2020, 2:48

    It will be much more effective for modern science to apply more funds and efforts to development of new instruments dedicated to direct imaging of distant objects (stars, planets etc.).
    Direct imaging does not require any assistance from ETI located on the distant side, every planet that is rotating around their star naturally isotropically reflects significant part of Electromagnetic energy that it gets from its host star. It is natural omnidirectional radiator, no need any help from ET intelligence.
    Our task – is to build advanced instruments to extract maximum usable information from this “free of charge” source.
    Direct imaging will allow to detect even non intelligent life, for distant it will give us obsolete information about distant worlds (due to speed of light), but it does not requires any dual direction communication and any scheduling procedures with any distant ETI.
    So the only solution we have today – is improvement resolution of traditional astronomical instruments and invention of new one, only for example:
    Use of Solar gravitational lens (and other massive objects), also build and use of gigantic coherent antenna’s arrays to get direct images in higher and lower radio wavelengths.
    Problem that methods used in modern SETI are obsolete, have bad resolution and no chance of any detection.

    • Law Wong July 4, 2020, 7:53

      Agreed. I think SETI’s primary focus should be on detecting technosignatures at galactic distances rather than detecting METI attempts.

      The detection of a radio signal seems far less significant than large scale stellar engineering.

      Radio signals, unless encyclopedic in nature (which would imply targeting), do not give us useful information on what is technologically possible. The discovery of large scale technosignatures would immediately change numerous paradigms on our understanding of the future.

  • Harold Shaw July 4, 2020, 13:43

    Evidence of the absence of signals is immensely important. SETI is valuable.

    If we except the possibility of ET people, then we are rational agents playing a game of galactic diplomacy and we need to know what other players are doing. Their behaviour must inform our decision making process regardless of differences in motivation, cost, and risk. If every hypothetical player is quiet then being quiet has value as a strategy.

    Many common pro METI arguments are weak. The strongest is that we are already doing METI. If we can’t avoid METI, we must SETI to increase our ability to play rationally.

    • Wojciech J July 8, 2020, 10:42

      No such thing as being quiet in the Universe I am afraid, the universe is a sea with lighthouses, not a dark forest.
      Both our biosphere and signs of our civilization would be clearly visible to any advanced ETI.

  • Gary Wilson July 4, 2020, 14:58

    Thank you Mr. Cordova. This is one of the best and most well reasoned articles and discussions on attempts at communicating with or at least detecting E.T. that I have read. Your arguments seem sound to me. Passive listening for E.M. communication from other civilizations almost certainly won’t work. I have seen estimates of the probable lifespan of our civilization in the tens of thousands of years or less (and some estimates are much less). The likelihood of successfully receiving such a message is very low. Dr. Wright’s ideas of looking for Waste Heat signatures and your ideas of looking for other technosignatures seem much more likely to succeed. Creating a green wave as Alex Tolley suggests sounds very interesting although very difficult given the distances and resources involved. Our chances of a green wave in the Solar System as in the work of Kim Stanley Robinson seem fairly likely but beyond that, outward into the galaxy very unlikely. Stability of our civilization rather than stagnation seems to be a key as well. Reducing population until we can use energy much more efficiently and less destructively would not be stagnating but rather re-thinking our approach to survival. Small and smart versus big and dumb. Right now our civilization is big and dumb. It won’t survive in its current form and therefore we won’t survive to possibly make Contact at some point. We can and should be able to overcome our near term problems involving human induced climate change, overpopulation, habitat destruction, etc. etc. and I might add a real attitude problem about humans “owning the Earth” along with all of its resources and controlling the destiny of almost all other species. A lot of intelligence and a fair bit of humility and empathy will be required to be a long lived technological species.

    • Henry Cordova July 5, 2020, 14:12

      Thank you for the kind remarks, Mr Wilson.

      But I must remind you that my opinions on these issues have changed a great deal, even over the last few years. I used to embrace many of the same arguments my critics here are throwing against me, and who’s to say who’s right?

      The real truth (whatever THAT means) is probably some combination of the two, or perhaps even some third (or fourth or fifth) alternative we haven’t even considered yet. We are, after all, talking about how alien intelligences will think and act, and how they will relate to other intelligences they may stumble across. We really haven’t a clue.

      You did bring up a point that might be worth following up: Do we really “own the Earth”? What is the “natural limit” of our own jurisdiction. If the aliens land here and start harvesting us for protein, what gives them the right, or our right to stop them? If they start dismantling Jupiter and Saturn for building material are they justified in doing so because we didn’t do it first? Suppose they concede to us the sovereignty of our solar system, but feel they have the right to colonize and exploit every star system within 10 parsecs? Who gets to draw these lines, what is the natural law that assigns ownership and economic rights? What if the visitors are essentially benign, but simply do not recognize or even comprehend our concepts of boundary and property. Have you ever read the essay by Theodore Roosevelt that describes in detail why we have the right to take and exploit Native American lands because they simply have no idea how to “properly”use and develop it. Essentially, we have plow agriculture, they don’t. We have the right to plant crops and prevent them from hunting and gathering. He actually concedes to them the right to own and defend their land, but that they have forfeited that right because their exploitive technology is primitive.

      We simply have no idea how the LGMs and BEMs are going to consider things like “rights”, or concepts like “fair”, when even our own economic and political relations with others of our own species are so blatantly self-serving and arbitrary, and so subject to change over short periods of time.

      I don’t think we can count on them being Libertarians. Or Republicans or even Capitalists, for that matter. And it could go either way. They may be totally unprepared for anybody as greedy and territorial as us.

  • Astronist July 4, 2020, 15:14

    “it is not unreasonable to assume that life is quite common in the Galaxy” – this is the point where you go wrong. A galaxy in which life is quite common at the present early stage in its life cycle is a possible scenario. A galaxy in which life is very uncommon at the present early stage in its life cycle is another possible scenario. The function of science is to identify which hypothetical scenario is most economically accounted for by the available evidence. I submit that your conclusion “we are almost certainly not alone” does not match the most economical scenario.

    • Gary Wilson July 5, 2020, 19:50

      Let’s let the future data decide how common life is in our galactic neighbourhood at least. With respect is it possible neither of the two alternatives you have described is useful either? That means we need as many means of gathering data about both our own solar system as well as nearby systems as possible. We must resign ourselves to the possibility that we won’t know much about even nearby exoplanets in habitable zones for many years to come. I am hoping we will explore our own solar system in the coming few decades and begin to get some answers nearby at least.

      • AlexTru July 6, 2020, 3:04

        Science can give answers about ET life appearance frequency, but SETI (due to used for life search methods) – does not have any chance to collect scientific data.

  • Geoffrey Hillend July 4, 2020, 17:28

    Quote by Henry Cordova: “But what if there may be highly advanced civilizations with no technology at all? I suspect that high degrees of sophistication and culture are possible with no technology whatsoever.” The history of our planet has already had this which goes all the way back in time to the democratic elements in the Roman republic. etc.

    If we look at evolution, technology must always be part of any intelligent ET civilization after 10,000 years of civilization. Maybe the time a civilization becomes technological is convergent so it takes roughly the same number of millennia for each world to become technological using our Earth as an example.

    There is a psychological view that must also be included because it is clear than we were more primitive in the past, so there is an evolution of consciousness from more lower primitive and naive state to higher wiser, but maybe even smarter state. My point is that we don’t start at the top of the pyramid so there must be wars, and our world wars have resulted many technological innovations, RADAR, the rocket, and from these the radio telescope and space travel.

    I like the idea of time involved with an ET civilization. I read a book called Beyond UFO’s by Jeffrey Bennett who I think was a consultant for SETI. He writes about a galactic civilization which might exit without us knowing about it that we may not have access since our technology is not advanced enough. If our technology was not advanced enough and the advanced ET’s used a way of communication which made radio signals obsolete, they would be invisible to us. We could not access it until our technology became advanced enough and not until then would we be allowed into the galactic club. If this speculation is true, then it could explain the Fermi paradox because the number of worlds using radio signals would be limited to today’s level of technology or one not too much more advanced than ours. Consequently, SETI and METI would not be obsolete, but there might not be lot of ET intelligent worlds at our level of advancement so we might have to wait a long time to get a radio signal.

    It makes financial sense to only send a radio signal to an exoplanet when we have an Earth twin with all of the biosignatures so we don’t have to have a wide signal. METI might be expensive, but SETI is a lot less expensive.

    • AlexTru July 6, 2020, 3:30

      If there is lot advanced civilization that radio technology is obsolete for them, it make any SETI/METI efforts hopeless, useless and not clever …
      In same time SETI (much worst case METI), in useless and hopeless for detection and communication with civilization that still using radio, because long interstellar distances time delay make dual direction communication impossible, as sequence single direction message detection – senseless .

  • DCM July 5, 2020, 3:53

    We just gotta wait and see.
    Meantime we better expand and develop environments to improve our and other Earth life forms’ survival chances. Grow, entrench, grow…

  • ole burde July 5, 2020, 12:28

    Well , the good news seem to be SETI is slowly increasing the probability we might have a good part of the galaxy for our own human purposes…..but the bad Telecope- News is a growing probability of a need to terraform any planet we can reach in the neighborhood…..and this could take a long , long time …

    • DCM July 6, 2020, 4:45

      Quite right — which is why we need to emphasize developing other worlds and building sustainable space biospheres.

    • ljk July 6, 2020, 14:25

      Why do we keep assuming that those who come from Earth / Sol system to eventually start spreading out into the wider Milky Way galaxy are going to be contemporary organic humans? Besides the decades of indoctrination by science fiction media.

      Oh of course it is possible. I can see some group of ultrarich types hollowing out a planetoid or comet or two, stuffing their followers and material wealth inside them, attaching a rocket motor, and heading off for some tax-free and monitoring-free interstellar haven.

      I can also see the possibility of a When Worlds Collide equivalent scenario, assuming the backers, builders, planners, and participants can do it without the rest of the panic-stricken species knowing about their escape plans before they take off for relative safety.

      However, I think the real explorers and, if the terms can be used here in the same way it usually is, settlers of the stars will either be made of silicon or bioengineered to survive all sorts of extraterrestrial environments, which will likely render them in appearances and mindsets quite different from what we are accustomed to circa 2020.

      This will render the need to terraform a planet pointless and save a lot of time and money, in case this was being used as yet another barrier against Terran natives spreading outward.

      Incidentally, the antiquated mindset regarding Dyson Shells is often still in effect – that being that such a megastructure would be used for organic bipedal humans to live inside of – when it would make a lot more sense if the Dyson Shell were an entity unto itself, or at least a collection of Artilects. Paradigm shifting, folks.

      In Orion’s Arm, Earth is a nature preserve guarded by an Artilect named Gaia. All humans were kicked off the planet to preserve it for the rest of the creatures there before humanity exterminated them. Now I don’t think we need to be that drastic: In fact, I can see where what they call baseline humans (us) might actually be part of the preserve, seeing as we really are not designed to live off word without a lot of external (and expensive and resource-consuming) modifications.

      Humanity is serving its purpose: To herald the next levels of intelligence from Earth. There is no shame in this; after all, we are the products of seven million years of earlier species who led up to us. We will have done our jobs. Now we can retire on a more beautiful and cared-for world as we always want in the end.


      • DCM July 7, 2020, 4:47

        Our descendants will see…

      • Harold Shaw July 7, 2020, 9:36

        Can any people become space faring without also discovering the technologies needed to transform themselves? Can any people with the drive to explore, to expand the boundaries of person-hood and people-hood avoid using those transformational technologies. I don’t think so.

        You are describing what I think is an important filter. Humanity and its lineage does not have to survive this experience.

        • DCM July 7, 2020, 12:54

          But let’s not let the present scourge of self-hate color our expectations, either.
          We will learn to modify ourselves for different purposes but that will involve a lot of social strife and struggle.
          Let’s not eagerly await becoming something else any more than eagerly anticipate aliens to reveal superior human values.
          The quest will shape the explorers; there’s plenty of time and room for that.
          We start off as present humans and move from there. None of us can know what’ll happen, so one step at a time.

      • ole burde July 7, 2020, 11:55

        Why “ ..asume flesh and blod descendants…´´ ? because that´s what any living thing , including myself , wants to asume , with all the tenacity inherited from evolution….if it doesn´t want that ,it´s probably dead or will be soon ….Evolution has created humans as its ultimate masterpiece in the art of surval , in all conditions and in all environments….humans will survive a thousand generations in the unnatural conditions of a mobile spacecollony striving to terraform a new planet , but it will help a lot if they can retain the HOPE of one day breathing fresh air and generally enjoying the beaty of a New Earth ….hopefully without mosqitoes , fireants, rats and coronavirus !

        • Alex Tolley July 7, 2020, 12:14

          Keats once lamented that science would “unweave the rainbow” and reduce the human perception of beauty. I daresay all of us reading the CD posts would disagree with that, and like Dawkins, argue that science has revealed even more beauty in nature. Our post-human future will likely reveal even more beauty through senses and physical forms that we cannot even imagine, able to experience first-hand extraterrestrial planets and even space itself. IMO, not everyone will want to embrace that future, but a sufficient minority will.

          • NS July 8, 2020, 1:41

            I can’t speak for Keats, but I always took “unweave the rainbow” to mean a completely analytical approach to nature, as opposed to one that includes awareness of its beauty (and horror, for that matter). IIRC in “Life on the Mississippi” Mark Twain writes of an old riverboat pilot who has no esthetic reaction at all to his natural surroundings, seeing everything as (say) indicating shoal water or approaching bad weather. While that sort of analytical vision was essential for a riverboat pilot Twain thought it sad that the man was unable to see anything else.

            • Alex Tolley July 8, 2020, 12:47

              Which may also tell you something about the limitations of Twain’s vision too. Beauty is a subjective experience and can be evoked by any number of different stimuli, from a natural landscape to an elegant math equation. “Beauty is in the eye of the beholder”.

          • DCM July 8, 2020, 5:16

            Such statements as Keats’ reveal an assumption that we can know everything.
            What we’ll really do is improve the mental versatility that has carried us this far. Nobody minds saying that dogs or chimps are limited; but so likely are we and only we can overcome those limits deliberately and not leave them to the chances of random mutation and natural selection. But we’ll still have limits….

          • Mike Serfas July 9, 2020, 9:56

            It is not science which unweaves the rainbow, but the rainbow which unweaves the sunlight. Science merely gives the rainbow a name – just as poets do. But to understand the rainbow is to understand the sunlight, and to be able to perceive the beauty within it at all times, and spot the rainbow bursting out in every tiny droplet. Then one can recognize the nobility of sunlight beside lesser lights that produce only a deceptive mockery of its illumination in a few narrow bands of emission.

            A mere poet may not find the beauty he seeks under the fluorescent light, yet would he understand why? Could he describe what was lacking? Then what use is he as a poet, and what hope does he have to find the Sun again in this life, save by expedient of not being long able to leave its sight?

        • ljk July 7, 2020, 13:34

          Again, I am sure some remnants and offshoots of organic humanity will went their ways into space to make an effort to survive in its various hostile environments. How well they will do and how long they last will depend on numerous factors, not the least of which will require both adequate and sustaining technologies and the proper psychological stance.

          One irony I can see is that for humans to survive in space permanently they may actually have to become less intelligent, or perhaps less psychologically diverse. In other words, they may have to take on the characteristics of mechanical drones that can also reproduce in order not to degrade mentally in the confines of the Final Frontier.

          So that being said, why not skip the middleman – or midwife in this case – and get right to the outright artificial which will be able to cope both physically and mentally with whatever the Universe can throw at them.

          If the higher life forms in our galaxy are indeed Artilects, this may be another factor as to why we have yet to find them, or hear from them.

          • Wojciech J July 8, 2020, 10:28

            Without delving into it much further, I would say that if we would speculate that the ambiguous SETI results so far were indeed detection of ETI, they would indicate just this. Rather uncaring and possibly artificial entitites engaged in their own megascale works.

      • Alex Tolley July 7, 2020, 12:02


        Who is “we”, Kemo Sabe? ;)

        • ljk July 7, 2020, 18:14

          All the smart ones that shift paradigms upon learning new things. :^)

  • Michael R. Watson July 5, 2020, 20:27

    It’s conceivable that more advanced civilizations continue to use radio waves for communications, just as we continue to find uses for fire, even though we discovered it hundreds of thousands of years ago.
    Perhaps radio waves are sent through some distance-defeating conduit like wormholes or bulk space, solving both the time-lag and diminishing signal strength problems.
    Such signals would probably be very efficiently modulated. We have already begun to do this with digital signals. The more efficiently a signal is modulated, the more difficult it is for the naive outsider to distinguish it from mere noise.
    If we could somehow learn how to tell such seeming noise from real, natural noise, we might be in for some surprises.

    • DCM July 6, 2020, 12:39

      I worry that if indeed we do pick up definite signals (not, somehow, echos of our early radio & TV signals), then resources will be diverted from exploration and use of our nearby resources into trying to communicate with the aliens — especially if controlled by people who already believe the creatures have moral and spiritual values that will seem to make sense to us and that we must follow.

      • AlexTru July 7, 2020, 2:12

        You are describing Frightening and very realistic (most probable) scenario by the way. A new religion…

      • ljk July 7, 2020, 11:56

        Not that I put just about anything past humanity these days when it comes to certain behaviors, but I doubt it will get that extreme.

        But since finding alien life, especially the intelligent kind, is one of the main goals not only of space science but for human development in general, how are you making this a bad thing?

        I feel like humanity has turned into a bunch of risk-adverse paranoids who would literally slam and lock the door on any and all progress beyond certain basic needs that humanity knows are safe – or supporting some sports team or crappy movie franchise or some transient feel-good source like that.

        As for SETI and aliens becoming a religion as Mr. AlexTru and his several other alias so often fret about, I say… why not? Humans have certainly done far worse when it comes to their deities and cults. At least this time their “gods” will be verifiable by science. :^)

        BTW – In reality I find your constant labeling of SETI as a religion to belittle it publicly in this forum and no doubt elsewhere to fulfill your agenda both annoying and offensive to the field and its practitioners, but I decided to just go with the flow this time because even I know when to stop banging my head against a dead horse.

        BTW 2 – this will probably have you clutching your chest…


        • Alex Tolley July 7, 2020, 12:36


          I don’t think that is what he is saying. It is the [endless]search that remains unfulfilled that could become a religion. The SETI becomes analogous to organized religion, with instruments instead of cathedrals. METI becomes like prayer, hoping for a reply. Organizations become self-perpetuating. Would a dedicated SETI organization ever declare that the search was over despite hundred, perhaps, thousands of years of ever-increasing efforts with no positive results? Will SETI produce Millerite predictions of success around the corner if we just keep funding the effort?

          I hope that SETL proves positive within a few decades. But SETI could easily take millennia to get a positive result (assuming that happens). How would it transform over that time, given that resources would be used yet no positive results attained, sustained only by the hope that ETI is out there, somewhere? That doesn’t mean we should not keep our eyes and ears open for signs of ETI. But it does mean that dedicating resources purely for the search may be a mistake over the long term. I think that the Allen Telescope Array that was designed so that SETI could piggyback on radioastronomy was the smart use of resources. If SETI turned up nothing, that would not detract from using the resources for productive areas of research.

          • ljk July 7, 2020, 18:25

            Astronomy is about an endless search in an utterly vast arena. So is space exploration. So is much of science in general. So finding alien beings among 400 billion stars in a galaxy that is one of over 2 trillion such stellar islands is going to take a while.

            Tell me when we should stop searching and asking questions.

            • Alex Tolley July 8, 2020, 12:35

              Tell me when we should stop searching and asking questions.

              Probably about the same time as theists stop expecting answers to their prayers. ;)

          • AlexTru July 8, 2020, 2:41

            By the way Allen Telescope Array can be good base for Radioastronomy researches. More coherent antennas in this array will allow to have better resolution in direct imaging of cosmic objects, there is only need to free resources for real science and postpone Amateur radio.
            SETI it is very expansive branch of amateur radio, no more.
            The popular among SETI activist movie: “Contact” is illustrating well this point.
            SETI can be very attractive and romantic , but far from science.
            In distinguish – astronomical researches constantly increasing our knowledge about Universe , adding non-stop a new scientific facts to homo sapience knowledge base.

        • DCM July 7, 2020, 13:02

          It will be a great thing to find another intelligent species. What I’m worried about is the impractical response of people seeking — whatever — to make their lives better. That’s scary and why we need to be more widespread. I’ve met some of the people yearning for alien enlightenment, who attribute human development to aliens, etc.
          While we can’t wait till life on Earth is perfect, which it won’t ever be (some do maintain we need to achieve that before moving on), we do need to expand and achieve as much as we can to put us in a better position to confront the unknown. And aliens are unknown.

        • DCM July 8, 2020, 12:20

          Having biological entities “verified” as gods would be a disaster. As I mentioned elsewhere, we don’t seek moral advice from spiders.

          • ljk July 9, 2020, 9:17

            How so? As opposed to the billions of humans who worship unseen sky beings based on the writings and beliefs of people thousands of years ago who knew virtually no science and thought every lightning bolt and bird entrail to be messages from supernatural beings who apparently had nothing better to do than get way too involved with a primitive primate species on one lone rock in space.

  • Bill Spillman July 6, 2020, 11:04

    One point I did not see emphasized was the technical evolution of communication. Starting from simple amplitude modulation radio signals, we have gone to frequency modulation and then digital signals. Much of our data transmission uses fiber optic cables now. In addition, spread spectrum signals are indistinguishable from noise unless one knows the key. What that all adds up to is that on the electromagnetic spectrum at least, the earth flared like a match in the the darkness and then went out, even though we are now communicating more than ever. The current Seti research is like the scientist who is looking for his lost keys at night under a street light because that’s the only place where he/she can see. I would speculate that there are alien communication signals all around us, but we are not yet at the technical level to see them for what they are.

    • Paul Gilster July 6, 2020, 14:40

      Claudio Maccone’s fine book Mathematical SETI goes exactly in this direction:


      From the archives here, ‘Intelligent Probes: The Spread-Spectrum Challenge’:


      Maccone’s work on using the Karhunen–Loève Theorem (KLT) as a key into all this is fascinating.

      Going further out, I’d also consider the possibilities in gravitational wave signalling vs electromagnetic, as Gregory Benford has explored in various ways (with more to come, I’m sure).

      • AlexTru July 7, 2020, 2:38

        No any type of super advanced modulation will allow to overcome speed of light limit, same facts we can apply to gravitational waves, neutrinos etc.
        Fruitless hopes to look for interstellar communication solution in our current technology.

    • Wojciech J July 8, 2020, 10:24

      Do however keep in mind that SETI results gave neither a categorical YES or NO.The latter part is for obvious reasons not much exposed but there have been ambiguous detections.

      • ljk July 9, 2020, 9:39

        The main problem is that, even in 2020, most professional astronomers do not want to deal with the issue of intelligent alien life, as it:

        – Messes with their getting funding for their own pet projects involving verifiable and academically “safe” astronomical objects.

        – Despite public displays by themselves and their colleagues espousing support for the idea of life beyond Earth, few pursue the subject beyond the “safe” topics of microbes and interstellar organic molecules. Avi Loeb has been the wonderful exception here as of late, but then again, when you are the head of the Astronomy Department at Harvard, your career and standing with peers are pretty secure from ostracism.

        – Messes with their concepts of how the Universe works. Oh sure, a few brave pioneers like Carl Sagan imagined a Cosmos full of ETI who were also altruistic and non-predatory (he assumed that “bad” aliens would destroy themselves before they achieved interstellar space travel. Sagan also assumed that advanced ETI would gladly beam around their knowledge to less sophisticated species throughout the galaxy to uplift them, so take that for what it is worth). However, many professional scientists would actually be glad if aliens just stayed away and let them have their little fiefdoms in relative peace.

        – There is also a high religious factor that few explicitly talk about in terms of how much influence it has on our views regarding life beyond Earth of any kind. Many humans think the Universe was deliberately made just for our primate selves and the fact that it is so vast and has gazillions of star systems just doesn’t seem to really matter as a factor. Even the ones who are not fundamental about it still think we are special and any other beings are either imaginary or if they exist will need our help ala missionaries to learn the “truth” while ironically not taking into account the possibility that some ETI may hold the exact same attitude and have the means to back up their educational methods to boot. There are also those of a certain bent who think that aliens are really just either angels or demons in the biblical sense, so there is no real reasoning here.

        In summation, while we have made some cultural progress in terms of our cosmic views on this subject, we have a long way to go. So this is why I am wary of your typical astronomer being the guardian of the search for ETI, ironically enough. We need more diverse professions in the mix.

        • ljk July 9, 2020, 11:07

          To back up what I have said above with some evidence, an essay I had published here exactly eight years ago on this very day by coincidence gives a good example regarding professionals who dismiss ETI because the existence of such beings would mess with their agendas and not because science has disproven the presence of alien beings:


          It is a shame, because the authors do have very good intentions and I agree with their overall plans, but dismissing other intelligences in the Universe because it won’t fit in with their agenda, however noble, is not only wrong but will ultimately damage their ideas and their goals for having others accept them. Which, eight years later, I cannot say I am seeing any huge transformation guided by their concepts so far as I can tell.

          Oh well, what did they expect? They wrote a book full of history and scientific ideas and not a bunch of seconds-long flashy soundbites and Internet memes.

        • DCM July 12, 2020, 4:45

          Religion as we have it has become inadequate.
          It needs to be reformulated in newer terms that will give people the reassurance they need without chaining them to Medieval or Bronze Age concepts.

          • ljk July 13, 2020, 9:40

            True, but good luck with that. Most modern religions have barely changed in the last two thousand years. The last big change was going from many gods to one and that took over a millennia to happen globally.

            • Wojciech J July 15, 2020, 15:10

              You might be surprised to learn that most higher echelons of major religions are quite open to existence of ETI.
              I actually believe that for colonization we will need the mindset of devout people like Quiverfull or Hutterites(they already have a model that could be easily copied for settlement purposes) ;)



              I was actually surprised to learn that Hutterites were mentioned in some studies on potential space colonization already



  • Michael Fidler July 6, 2020, 11:35

    Ceramic Metamaterial Solar Sail could also due double duty as the telescope mirror when reaching the SGL! ;-}

    Proposed First Gravity Lens Mission by 2028 that Could Spot Large Islands on Exoplanets by 2050.


    Millions of Telescopes 4 Light Days From Earth Could Permanently Explore Other Solar Systems.


    Getting to the Gravitational Lens in 8.5 to 15 Years.


    Ceramic Metamaterial Solar Sails Could Enable 300 Kilometers per Second.


  • wdk July 6, 2020, 11:52

    This essay is definitely a keeper. Just from the discussion so far, it has been like quoting articles of a constitution. A comprehensive review from which to launch. And I believe some of the feedback has launched some new things to examine as well.

    Going back to the issue of “Where is everybody?”, it looks like there is a greater likelihood that “They” are at home if they exist or ever existed at all. And as we contemplate the problem of interstellar flight, our first notions of such exploration appear to be mechanical or by means of artificial intelligence – save for what we can construct locally to observe telescopically.

    So that suggests that if there are intelligent life forms or civilizations, the odds of contact are better with their extended elements – machines that somehow can traverse the distances under program.

    Before becoming acquainted with John Wheeler’s studies of gravitation, I had come across an interview or two where he was examining another conundrum like Fermi’s “Where is everybody?”: The Anthropocentric Principle”. I am not sure where it originated since a number of other physicists picked up the glove as well. But one of its consequences was a line of reasoning that there was (is?) a universe so that it could be observed. A circular argument in a way, but I think it worth bringing up in this context. Since it seems less likely that the whole universe is for our sole observational benefit – not to be shared with anything else, spatial distribution being whatever it is. Because this line of reasoning poses other issues too. Does the universe disappear it “we” do? Or what is it doing between appearances of self aware forms? … Do we have the best view? Hardly the best sensory perceptions.

    A few times “cognition” was mentioned above. But between organic life and the consciousness and thought we have, there is more than simply the difference between unicellular and multicellular organisms. And same is true with our AI and mechanical devices. Our efforts to light them up are about as successful as Urey-Miller.

    From a scientific standpoint, do we really know why it exists locally?
    Or when does evolved life reach such a threshold? It looks to me like this is something that extends the improbable nature of self awareness.
    If Miller and Urey’s experiment with artificial lightning and organic compounds yields little more than precursors to life, then how much more lightning do you need to get self awareness? Kicking a dead horse in several ways perhaps, horse meat that was never alive or aware.

    So I would posit that we do not really know that our self awareness originated with life forming on Earth. It might be that the ingredients for life and awareness had to be shipped in. And that either intelligence elsewhere did the job, or there might be ways that the basic instructions
    for life and awareness are embedded in the universe. Each seems like
    a very difficult threshold, unless there is already an inherent recipe somewhere.

    Getting some positive exobiology results from anywhere in the Solar System would go a long way toward resolving that question – or else opening it up. So our solar system search for primitive life is likely to continue wherever there is a subsurface pond.

  • Harold Shaw July 6, 2020, 14:29

    The distance between civilizations is an important though exaggerated consideration. Two widely separated peoples could exchange 100% of their exchangeable value as quickly as their respective technologies allow. This could be much faster than conventional trade. Distance would impact the initial negotiation of open transfer and make conventional trading difficult. How would parties demonstrate the value of a trade good by describing it without giving up control of the good? Distance doesn’t eliminate the potential for value exchange but instead makes open transfer the most productive technique. If this is true, then civilizations would want to avoid open transfer relationships with significantly less advanced ones because value would predominantly flow in one direction.

    Imo, the concept that a people aware they only have a million years wouldn’t try to contact other people and potentially increase their lifespan is almost bizarre. If on average, peoples have longer lifespans, then they can not avoid interstellar diplomacy.

    Heck, even if SETI only eliminates the existence of territorial beacons close to us, it will have paid for itself.

  • ljk July 7, 2020, 10:41

    I tell ya, if it isn’t terrestrial pessimism regarding alien minds, then the aliens themselves might mess it up:


    All I can say is, just because humans are technological, intellectual, and cultural adolescents does not mean everyone else out there is.

    • Michael Fidler July 8, 2020, 8:40

      Well all those 10 billion year old suns are going to be red dwarfs and so far the majority of them have built planets around them. This is just another bias that life is a G2V sun only, they are still in the sun centered universe! Intelligent life is around M dwarfs, that is the norm, majority of stars, longest lived, have an area around the terminator that life develops. I wish someone would stop dreaming of the second earth around a G2V star and face reality, the red dwarf halo stars are the place to search. They have the longest ages of red dwarfs and the longest stable environment compared to the G class star flying thru the galaxy arms every 132 million years. Why do you think it took 4.5 billion years for intelligent life to developed on earth.

      • ljk July 9, 2020, 11:55

        I have said it before elsewhere in this blog and I will say it again:

        Red dwarf systems may be very attractive targets to interstellar level ETI for their very long durations. That they may prove problematic to produce their own intelligent species may in fact be another attractive factor to those beings who want to utilize them: No natives to complicate matters.

        So yes, SETI should aim its instrument at red dwarf systems because the residents may actually be very noisy and conducting business of the technosignature nature that SETI is focusing on now.

        • Michael Fidler July 10, 2020, 10:18

          Well, you may be right but the Population II red dwarfs in halo orbits are old and stopped flaring billions of years ago, long before the solar system formed. More of them, more habitual area on the planets then earth, much longer lived, stopped flaring 9 billion years ago. Seems to me they been around long enough to know better then to deal with a little 3 million years old baby. They have been around 3000 times longer then humans.

          • ljk July 10, 2020, 11:45

            Right. I would not automatically dismiss native life evolving on worlds circling red dwarf suns, either.

            My one concern is, would those initial billions of years of nasty solar flares cause some kind of permanent damage to any life that tried to evolve there? Perhaps enough to wipe them out entirely, or hobble them so much that the organisms never get past a certain point no matter how many eons of stability they have later on?

            I know life is resilient, but I wonder if even if it could manage to survive and evolve in the vicinity of a red dwarf, would it ever reach intelligence? After all, a planet in such a system would have a very narrow and close habitable zone to its sun.

          • ljk July 13, 2020, 13:21
  • ljk July 9, 2020, 12:39
    • Alex Tolley July 9, 2020, 15:31

      It is inevitable that language will drift. Just look at the differences between Britsh and American English. Having said that, I think machine translation by then will be enough to facilitate any necessary communication issues. It may take some time, and will not be like Star Trek “universal translators”, but it will eventually work. As for the drift between the ship’s manuals and the crew’s descendants, simply having translations done every generation or so would ensure that the drift did not cut them off from understanding the original instructions. No professional linguists required.

      • ljk July 10, 2020, 10:15

        Alex, I don’t know about you, but my first real encounter with the interstellar multigenerational starship concept was Robert Heinlein’s Orphans of the Sky, which had a huge impact on me.

        I know science fiction stories are supposed to contain drama and action, or at least the conventional ones, so perhaps the idea of people living aboard a huge vessel for generations thinking it is the entire world and behaving accordingly is hopefully an exaggeration, but it is hard not to imagine such a project failing in multiple ways due to the fact that humans in groups are so fallible.

        As you may recall, in Orphans the trouble started when one man named Huff fostered a mutiny onboard the ship named Vanguard and disrupted everything. What is to stop humans from behaving badly if they are in such isolation for centuries or more, without employing draconian methods that may still cause unforeseen consequences. For me changing languages would be among the least of their concerns.

        Speaking of evolving languages, I took a course on Chaucer in college. The man wrote as the English spoke in the 14th Century CE. Even in such a relatively short distance in our past, I often found it hard to follow his written words without speaking them out loud to get their meaning.

        I often wonder if in just two hundred years, between the various accents and evolving slang of native English speakers, that we will have as much trouble understanding each other then as I did with Chaucer from a distance of roughly 600 years?

        • Alex Tolley July 10, 2020, 15:07

          I agree the failure modes in a generation ship are many. Even fake voyages such as “13 to Centaurus”, and the more recent tv miniseries “Ascension”. We are a fractious species. However, we do have some history in how to reduce problems based on our seafaring forebears. Autocratic governance and harsh punishment for mutiny. Even Heinlein seemed to suggest that bad behavior could get you summarily tossed out an airlock without a spacesuit. Closer to home, as our technological development increases and potentially lethal things can be made by individuals or small groups, we have seen a steady increase in policing and harsh actions for transgressors.

          As you say, language drift may be the least of our problems in such situations.

        • Wojciech J July 15, 2020, 15:21

          English is a very innovative language. There are languages that still remain mostly the same since 800 years and are recognisable to modern speakers. Georgian is said to be similar today to what it was in 5th century, and supposedly Lithuanian hasn’t changed almost at all. It is easy for Polish speaker to read and understand Polish texts from 13th century. So really it depends.


          • Paul Gilster July 15, 2020, 16:31

            Icelandic is another good example. Lots of new vocabulary, of course, but grammatically and morphologically the language is close to that of the Sagas and the Elder Edda.

  • wdk July 11, 2020, 12:42

    Reflecting since I made an earlier comment…
    Want to note that sometimes discussions about extraterrestrial life can run up against several distinction lost. Distinctions between/among
    -micro-organisms with or without multi-cell organization
    – organisms comparable to invertebrates and vertebrates as we know them
    – organisms that organize into communities
    -organisms which we would consider “smart” or intelligent
    – organisms or organizations we would identify as civilizations…

    In the latter instances, distinguishing between termites and ourselves, we presume that there are communication systems that can be broken
    down beyond an instinct or a pattern developed like the cell structure
    we inherit. SETI we expect to send us messages or we can send some they can receive – and we will both croon over recognition of forms
    or theorems from geometry, math or physical science. Perhaps we will even be able to broadcast back and forth operas.

    These upper level cases, however, assume things that might not be prevalent in nature. Maybe the aliens do not have capital cities or libraries or encyclopedias. And maybe some of the things they do which we consider technological are the result biological processes.

    Didn’t want to lead in on this item, but it also is part of the picture.
    I am not a psychologist of any sort – I clinical, research, humanistic or whatever, but I do recall as a college undergrad a popular book titled
    “Walden II.” by B.F. Skinner. The proposition there, perhaps for sake of argument, was that WE are not really conscious – and that what our behavior is is conditioned response. I suppose Dr. Skinner would give a pass on this assumption for his A students and fellow behaviorists. But it does illustrate again how difficult the notion of self awareness is to
    examine here on Earth – and much more so on other planets.

    We, of course, know that we are here because we have been here all our lives; but our scientific tools and methods leave us with many reasons for doubt. Perhaps this is one reason to adopt the term “techno-signature”. The chatty intelligence with mastery of radio-waves is sought after at one end of the scientific spectrum – and locally, in other splinter sessions, the science community is trying to rationalize away
    our own membership in such a supposed cosmos.

  • DCM July 12, 2020, 4:48

    All this mental agonizing over things we don’t yet know….
    Does it really prepare us?

    • ljk July 13, 2020, 9:34

      Far better than being totally unaware and unprepared and suddenly having major culture shock.

      Our ancestors until just a few centuries ago had virtually no idea of beings on other worlds. Imagine their reactions to encountering a visiting ETI.

      Even now such an event will be neither smooth nor quiet, but the concept that we are not alone will at least not be entirely foreign and unfathomable to us. That will be to our advantage. That we have also played out numerous scenarios both in science fiction and serious speculation will be to our advantage, unless they do something so outrageously unexpected.

      It bothers me more than a little when I keep seeing these kinds of comments pop up in this thread here and elsewhere in this blog. Especially from a group I consider to be more educated on the subjects than the general public.

      What exactly would you prefer we think – or not think about – in regards to alien life? Or many other scientific subjects for which we can largely only speculate upon at this moment in time and space?

      • Alex Tolley July 13, 2020, 20:07

        But just as importantly, even when we have come to a consensus, it can break down. With pandemics, the consensus was that it was a global issue, which would be coordinated with a global body, the WHO. The US would take the lead in funding and managing resources, with other countries helping. Governments would have international organizations to monitor early outbreaks and resources to contain it. This seemed to work for SARS, MERS, and the last Ebola outbreaks. But this all broke down with Covid-19.

        This suggests that even if we deliberate now and could come to a global consensus of handling various contact situations, there would be no guarantee that this would be executed when the contact came.

        [Similarly with Fascism. In 1948, the US Congress published a nice little report/book on Fascism – clearly identifying its common themes and explaining what the individual fascist nations had done. There was a consensus that this could not be allowed again. Germany, in particular, executed very complete de-Nazification efforts after WWII. Yet here we are, 3 generations (75 years) later facing the same situation all over again, just with different nations taking the lead. (and with few people even daring to use the “F-word”).]

        Bottom line, the OP raises some very important points., allied to other issues such as biases in science (research topics, who does the research, who are the subjects, etc.) Some of these issues become “wicked problems”, someething that the SciFi author Karl Schroeder has written about – e.g. WICKED:


  • ljk July 13, 2020, 13:18

    While this press release title is probably playing on the various speculative possibilities for these cosmic objects, it is interesting to note that so far they are not falling into the usual suspected categories:


  • Mark July 15, 2020, 13:03

    Fermi Paradox makes sense if this universe is an elaborately detailed computer simulation, with the only constraint that the simulation is effected using finite compute resources. The other worlds in this simulated universe are not populated or even detailed with physical features, in order to save on compute resources (CPU time, RAM memory, etc).

    In other words, we’re it, because the beings who built this simulation wanted to simulate our species on this planet at this time in history, for reasons that could only be known to them. If and when we begin to probe these other star systems in more detail, the simulation is likely designed to flesh out those details at that time. Until then, it’s a waste of resources to simulate those details.

    The beauty of this is that it should be possible to instantaneously travel to the other parts of the universe using no energy at all. All we have to do is reverse-engineer the source code, or determine the cheat codes.

    Other miraculous things are possible as well, beyond our wildest imaginings. The drawback is that whoever is running the sim might get bored and switch us off, or worse, unleash multiple disasters including viral pandemics and worldwide civil unrest.

    • Alex Tolley July 15, 2020, 14:28

      Stephen baxter wrote a short SF story about how the Fermi paradox was maintained by a fake view of the universe from Earth. As out instruments created every more data that needed to be simulated, it broke the simulation, and we were able to see the true universe.

  • ljk July 16, 2020, 13:32

    Not so dark skies

    A recent book makes the argument that space settlement could be so detrimental to humanity it shouldn’t be attempted. Al Globus makes the case that the book’s analysis, done correctly, should reach just the opposite conclusion.

    Monday, July 13, 2020


    • Alex Tolley July 16, 2020, 18:34

      And the review suggests that the opposite conclusion could be drawn. I know I am biased towards space colonies/cities, but it seems difficult to see how they can logically increase existential risk rather than decrease it.