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An Abundance of Technosignatures?

What expectations do we bring to the hunt for life elsewhere in the universe? Opinions vary depending on who has the podium, but we can neatly divide the effort into two camps. The first looks for biosignatures, spurred by our remarkably growing and provocative catalog of exoplanets. The other explicitly looks for signs of technology, as exemplified by SETI, which from the start hunted for signals produced by intelligence.

My guess is that a broad survey of those looking for biosignatures would find that they are excited by the emerging tools available to them, such as new generations of ground- and space-based telescopes, and the kind of modeling we saw in the last post applied to a hypothetical Alpha Centauri planet. We use our growing datasets to examine the nature of exoplanets and move beyond observation to model benchmarks for habitable worlds, including their atmospheric chemistry and even geology.

Technosignatures are a different matter, and it’s fascinating to read through a new paper from Jason Wright and colleagues. – Jacob Haqq-Misra, Adam Frank, Ravi Kopparapu, Manasvi Lingam and Sofia Sheikh – discussing just how. The intent is to show that technosignatures offer a vast search space that in a sense dwarfs the hunt for biosignatures. That’s not what you would expect, as the latter are usually described as a kind of all-encompassing envelope within which technosignatures would be a subset.

On the contrary, write the authors, “there is no incontrovertible reason that technology could not be more abundant, longer-lived, more detectable, and less ambiguous than biosignatures.” How this potential is unlocked impacts how the search proceeds, and it also sends out a call for collaboration among all those hunting for life elsewhere.

Image: Photo of the central region of the Milky Way. Credit: UCLA SETI Group/Yuri Beletsky, Carnegie Las Campanas Observatory.

Technosignatures as Subset?

Remember that technosignatures do not require an intent to communicate, but are evidence of technologies in use or even long abandoned, perhaps found in already existing datasets needing re-examination, or in results from upcoming observatories. Check your own assumptions here, based on the Drake equation, in which factors include the fraction of habitable planets that develop life, the fraction that produce species that are intelligent and can communicate, and so on. Traditional thinking sees technosignatures as an embedded feature within a broader spectrum of life.

Reasonably enough, then, we might decide that if intelligence is a rare subset within biological systems, technosignatures would prove even rarer. Our own planet seems to exemplify this, with our species having become communicative only within roughly a century of today, despite 4.6 billion years in which to evolve. But Wright and team make the case that technology cannot be bounded in this way. Its emergence may be rare, but once it appears, it is possible that it will outlive its biological creators.

Biology may confine itself to a single habitable planet, but why should technosignatures be thus limited? In our own Solar System, we are producing, the authors argue, technosignatures for multiple worlds right now, especially at Mars, where we have our combined force of landers and orbital assets taking data and communicating results back to Earth. Such signals should increase as we follow through on plans to explore Mars with human crews and robotic spacecraft. As we spread into the Solar System, new technosignatures will emerge at each venue we study.

Why, too, should technology not spread through self-replication, perhaps not under the control of the biological beings who set it into motion? For that matter, why should we confine technology to planets? Places with no biology may prove extremely useful for our species, as for example the asteroid belt for resource extraction. We might expect technosignatures to emerge from these operations, another separate appearance of technology that grows ultimately out of the single planetary source. Moreover, this diaspora is unlikely to confine itself to a single star system, as the authors point out:

There is also no reason to think that technological life in the galaxy cannot spread beyond its home planetary system (see Mamikunian & Briggs 1965; Drake 1980). While interstellar spaceflight of the sort needed to settle a nearby star system is beyond humanity’s current capabilities, the problem is one being seriously considered now, and there are no real physical or engineering obstacles to such a thing happening (e.g., Mauldin 1992; Ashworth 2012; Lingam & Loeb 2021). Even if we cannot envision it happening for humans in the near future, it is not hard to imagine it transpiring in, say, 10,000 or 100,000 yr.

What a shift in thinking in the above paragraph, which to us merely states the obvious, when compared to a mere 75 years ago, a time when the idea of interstellar flight was considered science fictional in the extreme, and we were only beginning to probe the physics of the engines that might make crossing to another star possible. Today we’re more likely to be thinking about interstellar journeys as expeditions awaiting new generations of technology and engineering rather than a mystical new physics. We also factor artificial intelligence into an interstellar future that may be exclusively robotic.

Image: A rendering of a potential Dyson sphere, collect stellar energy on a system wide scale for highly advanced civilizations. How many separate technosignatures might have emerged out of a single biological source in the building of such a thing? Credit: sentientdevelopments.com.

Recall our recent discussion of von Neumann probes. While the average distance between stars is vast, Greg Matloff looked at the problem in an exceedingly practical way. Suppose, he said, we confine ourselves to times when stars are within a single light year of each other, which happens to our Sun every 500,000 years or so. If we launch a self-replicating probe only every 500,000 years, we nonetheless set up a process of such crossings that fills a large percentage of stellar systems in the galaxy within a time frame of tens of thousands of years. All of these can produce technosignatures.

Thus even the most conservative assumptions for interstellar flight using speeds not much beyond what we can achieve with a Jupiter gravity assist today still create the opportunity for technology to spread far beyond the planet of its origin. As the authors are quick to point out, the Drake equation cannot capture this spreading, and the search space for technosignatures could vastly outnumber that for biological life.

Lifetimes Civilizational and Technological

Looming over discussion of the Drake equation has always been the issue of the lifetime of a technological civilization, the L factor. How likely would we be to pick up a signal from another civilization if our own is threatened at this comparatively early stage of its growth by factors like nuclear or biological war? The Fermi question may be answered simply enough by saying that no technological species lives very long.

Here it’s fair to ask how much we are projecting human tendencies onto our extraterrestrial counterparts. This gets intriguing. The collapse of civilization would be a dire event, but absent actual extinction, our species might recover or, indeed, re-develop the technologies that once proliferated. The time between catastrophe and potential recovery is not known, but such events do not put a fixed limit on a civilization’s lifetime. Even if we assume that technological civilizations will roughly track our own, we may understand our own only imperfectly. From the paper:

…humanity is the first species on Earth that can prevent its own extinction with technology, for instance by diverting asteroids, stopping or mitigating pandemics, or building “lifeboat” settlements elsewhere in the solar system or beyond (Baum et al. 2015; Turchin & Green 2017; Turchin & Denkenberger 2018). This means that the upper limit on our technology’s survival is essentially unlimited in theory, even in the face of inevitable natural catastrophes. Apart from these modern examples, Earth-analogs from human history teach us that a technological downshift—to temporarily become less technological until circumstances improve—is a common and healthy adaptation to catastrophe in human history and that technology and longevity are in this way inextricably linked…

Nor can we rule out the possibility that the Earth could develop other species beyond our own in the future that can produce a technological society following humanity’s extinction. For that matter, are we so sure about our past? If there have been prior periods of technology on Earth, the processes of time over millions of years would likely have eradicated them. Thus using our experience on Earth as the model for the Drake L factor is inadvisable because of how little we know about L for our own planet.

Technosignatures can outlast the beings that create them, and as the authors point out, the ones we produce are already on a par with Earth’s biosignatures in terms of detectability. While we would not be able to detect the biosignatures of Earth from Alpha Centauri’s distance, the final iteration of the Square Kilometre Array should be sensitive enough to pick up our radars at distances of several parsecs, and an advanced space telescope within our engineering capabilities now (such as the proposed LUVOIR) might be able to detect atmospheric pollution at 10 parsecs.

It seems a safe assumption that if our biosignatures and technosignatures are roughly comparable in terms of detectability today, the advance of technology as a species continues to innovate should produce ever more robust technosignatures. We cannot, in other words, assume a biology-like trajectory, as implicit in the Drake equation, for the evolution of technosignatures and their detectability through SETI. Indeed:

…the spread of technology could reasonably imply that the number of sites of technosignatures might be larger than that of biosignatures, potentially by a factor of as much as > 1010 if the galaxy were to be virtually filled with technology.

No wonder some authors have considered adding a ‘spreading factor’ to the Drake equation, which accounts for the possibility of technologies moving far beyond their home worlds. Thus one technosphere produces myriad technosignatures, while the Drake equation in its classic form inevitably does not account for such growth. If the equation assumes life emerges and stays on its home world, the authors of this paper see technology as having a separate evolutionary arc which potentially takes it far into the galaxy in ever proliferating form.

While the search for biosignatures continues, it makes sense given all these factors for technosignatures to remain under active investigation, and to encourage the astrobiology and SETI communities to engage with each other in the common pursuit of extraterrestrial life. Comparative and cooperative analysis should enhance the work of both disciplines.

The paper is Wright et al., “The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous,” Astrophysical Journal Letters 927, L30 (10 March 2022). Full text.

{ 74 comments… add one }
  • Edwin March 18, 2022, 6:10

    This paper looks interesting

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Popular Physics (physics.pop-ph)
    Cite as: arXiv:2203.08968 [astro-ph.IM] (or arXiv:2203.08968v1 [astro-ph.IM] for this version)
    Submission history
    From: Jacob Haqq-Misra
    [v1] Wed, 16 Mar 2022 22:18:52 UTC (163 KB)
    Astrobiology, SETI, Technosignatures,

  • Robin Datta March 18, 2022, 8:07

    Coverarge of related topics on John Michael Godier’s podcast:
    Have Older Alien Civilizations Already Settled the Galaxy? w/ Marshall Eubanks

    • Adam J Crowl March 22, 2022, 7:36

      Marshall’s ideas are definitely worth discussion here on CD. Now to get him to write something up…

  • Jer March 18, 2022, 8:59

    I, as well, am most compelled by the idea of a technological/ post-bio-dominant spread of conscious/ reasoning complexity (aka life).
    As with all things, I would argue that the ‘modern’ direction of the group/ community/ civilization is primarily driven by the aggregate motivations of its individual constituent’s fundamental (but evolving) values. If we are open to the idea that the most durable and functional of civilization constituents are likely augmented biologicals or full-technologicals, it is reasonable to believe that these may also make up the vast majority.
    But now to depart from notions of group and community: As the likely technological advances made available to the individual, from the community/ civilization, increase and develop, so does the individual’s ability to ‘forge its own path’. With such a vast expanse of space, discovery, and opportunity available, so goes the dreams and goals (in the most highly developed curiosity sense) of its most able members, likely making up a vast portion of the community’s resources, in a thoroughly advanced, post-scarcity society. With community merely being but the nest and creche of such adventurers, this civilization’s communal ‘techno-signatures’ remain comparatively small, dispersed, and localized to convenient cores of resources. However, further to the idea of the individual increasingly seeking the most promising objectives (whatever that means) and increasingly trying to augment and support its own discovery adventure, so does this constituent continue to travel, spread (perhaps by sensors or other mean to expand its awareness), and covet additions to its knowledge and understanding. This may, of course, mean that complex/ reasoning consciousness may travel fast, isolated, and barely-detectable. A possible solution to detecting these would be to determine ‘points of nearby Universal interest’ or possibly, devise ‘honey-pots’ to attract (ideally, several light years away from Sol). At the end of the day, what are we most interested in (read: have the resources and available technology for)? Intelligent detection/contact or civilization-scale archaeology?

    • Alex Tolley March 18, 2022, 12:13

      I too think that long-lived civilization is likely to be post-biological. I also think that they will populate much of the galaxy as they do not need suitable HZ, biologically transformable worlds to live on, and even space habitats need not be supportive ecosystems to provide all the biological necessities of [terrestrial-type] life. Simply from the POV of cost and complexity, machine civilization will outpace biological expansion.

      But here we run into the Fermi Question. If that is the case, why hasn’t at least one of those post-biological civilizations made the galaxy (and the universe) more obviously “unnatural”? We may have difficulty recognizing this artificial nature, but we really are more cognitively intelligent than ants at the side of a new freeway.

      Either we happen to be near the start of such expansion by other civilizations, or…. we are the first and it will be our machine civilization that will expand into the galaxy sometime in the future. The Pioneer, Voyager, and New Horizon probes are our first crude emissaries, eventually to be followed and overtaken by far faster, and more intelligent probes and more.

      If that is the case, then I hope that our species will seed the galaxy with terrestrial life on all the sterile worlds, so that we green the galaxy. Our machines will be tasked with that duty as a long-term goal as they develop their own civilizations as they spread through space. IDK if we can guarantee that our machine descendants will maintain that goal, but I would like to think that billions of years from now, our galaxy will be full of both terrestrial and non-terrestrial biospheres, and possibly the galaxies around us. In Asimovian terms, the highest priority goal (-1 th?) law is to nurture all life and no other goal can supersede this one.

  • Alex Tolley March 18, 2022, 9:13

    Techno-signatures are more prevalent than biosignatures? Technology replicating itself? I’m not buying it.

    If technology replicates, then the spreading issue reintroduces the Fermi Question. Wright is just claiming we have to look harder for them rather than seeing evidence in front of our noses. If technology doesn’t replicate, then its spread is likely limited to the home system or a few nearby, otherwise, it’s the Fermi Question again.

    Technology might last billions of years, but probably only in certain circumstances. Our Mars rovers will not, being buried by sand quite quickly. The lunar Apollo descent stages will last longer, but for billions of years? Satellites and spent rocket stages in high orbits and ones well away from perturbations will fare better. But how much more observable are they than the life covering a planet? We have previously discussed the difficulties of hunting for Lurkers in our system, even the Moon. But how much easier is it to detect the life on Earth and with unambiguous biosignatures?

    Any paper designed to suggest the ubiquity of one type of observation over another is designed to push the funding in that direction. The logic that biosignatures are more common than techno-signatures is clear. While that doesn’t mean we should focus all our efforts on biosignatures, it does suggest that is the most fruitful approach. We can argue all we like that SETI has barely sampled the galaxy, which while true, is still greater than our biosignature sampling. The former has shown no results for decades, so lets give biosignatures a chance.

    The obvious bet if technology is more ubiquitous is to put some skin in the question of whether we will find life or technology first when we explore our system more systematically. The most probable outcome is neither. After that, I would bet on life, whether extant or extinct. If the technology exists in our system, it will be hard to find, either due to rarity, or it is hidden or so small as to be nearly unobservable. This implies to me, that techno-signatures observable elsewhere will have to ve very large, comparable in size to planets, or emitting signals of some sort that have the same strength as the reflected radiation from a planet.

    • Robert March 18, 2022, 12:38

      While we haven’t yet developed molecular nanotechnology as Drexler envisions it we can see the possibility and with it a technology base that continuously repairs and renews itself given suitable resources. Much discussion in the early days revolved around the problem of runaway or uncontrolled replication, the so-called grey-goo problem. One could imagine an advanced society having strict protocols to prevent such a problem on the cosmic level by exponentially replicating technology because it would eventually overwhelm even them.

      • Alex Tolley March 19, 2022, 10:34

        While we haven’t yet developed molecular nanotechnology as Drexler envisions it we can see the possibility and with it a technology base that continuously repairs and renews itself given suitable resources.

        We can envision lots of things, many well beyond our capabilities, maybe even impossible.

        The “gray goo” issue was concerned not will replicators, but with entities that we lose control over. Now the term is “paperclip maximizers”. We already have those, not AIs, but human intelligence in the form of corporations with the singular goal of profit growth. Profit maximization is doing an admirable job of apparently unstoppably consuming the planet.

    • Joe H. March 19, 2022, 10:54

      “The logic that biosignatures are more common than techno-signatures is clear.” I would think this is self evident. The ratio of ordinary life to technological civilization here on Earth is about 8.7 million to one, even higher if you include extinct species. I suspect that finding evidence of oxygen producing vegetation on other planets is far more likely than finding evidence of alien technology.

  • Henry Cordova March 18, 2022, 9:54

    “Here it’s fair to ask how much we are projecting human tendencies onto our extraterrestrial counterparts.”

    Its not just “human tendencies” we’re projecting here, it is mostly the tendencies of SETI enthusiasts and space groupies…benign but obsessed hobbyists like me and thee. We do not necessarily represent the goals and desires of alien civilizations, we may not even be characteristic of most humans in our own civilization, or even of the scientifically literate community.

    We seem to have convinced ourselves that once any biological organism evolves to the point of developing technology, it must necessarily embark on a program of galactic exploration and conquest. Of course, it is certainly possible that if the evolution of intelligence is extremely common, then the sheer number of galactic civilizations will ensure that even the small proportion of them that are aggressively expansive will produce sufficient technosignatures that we might serendipitously stumble onto one. This may very well be true, but we just don’t know that, do we? And there is really no way we CAN know that.

    I’m all in favor of scrutinizing archived astronomical data looking for evidence of distant civilizations, or of looking for anomalies in new data. By all means. But lets not get our hopes raised unrealistically, and let it not divert resources from real research with some probability of turning up real results. Resources are always scarce, let’s not squander them chasing wild geese.

    It is the responsibility of communities like ours to manage this activity,
    to suggest reasonable strategies and call attention to promising fields of interest, to find a balance between fanatically proselytizing pointless searches and obstinately refusing to search at all.

  • Alex Tolley March 18, 2022, 10:09

    Observational technology and search strategy:

    In the 19th century, all we had was optical telescopes. We could image most planets in our systems, however crudely, and none beyond. A Lowellian Mars was the obvious target.
    The 20th century brought in radio telescopes. With radio communication now common, it made sense to listen for ET using radiowaves. The Drake Equation was the “they must be easy to detect” argument especially if a galactic club was broadcasting, and hence SETI. Then our optical technology improved sufficiently that we could detect exoplanets, and with spectroscopy sufficiently capable of detecting molecular signatures of just the planets. We are just at the beginning of the biosignature search.
    With science fiction at our backs, we can postulate those Drake Equation predicted technological civilizations have expanded as far as our imaginations and our plausible technological developments will allow. Interstellar travel? Possible, but difficult. Space habitats in Dyson swarms? check. Self-replicating probes? Theoretically feasible, but beyond our capabilities, although 3D printers and automated fabs are pointers to one way to achieving this feat. If feasible, how distributed. Enter any number of papers suggesting that the fermi Question is answered by “they are out there, everywhere, but hard to see. Given us the resources to look.” So we are back to SETI but this time, cognizant of the signal detection failure to date, we look for the evidence of various Ozymandiases, and our own scientific curiosity posits Bracewell probes (now Lurkers). Papers like Wright’s and Benford’s, amongst others, suggest that this techno-signature search is now the “low hanging fruit” that needs modest resources for a potential huge scientific gain. No doubt as technologies improve, the new directions for the search of exobiology and civilizations will be proposed.

    While I am skeptical about the likelihood of success, I see no reason not to add funds from less productive areas to initiate a more comprehensive search. Just diverting the funds from one F-35 fighter would be a huge bonus. Reducing our military spending by a sliver instead of increasing it, and diverting it to research, of which space exploration and the search for life is but one direction, would be better, and certainly more productive, whether we find anything or not.

  • Michael Fidler March 18, 2022, 10:14

    We made our loud cry of a new civilazation many years ago when nuclear bombs where first exploded and tightly focused high intensity radar beams scanned the horizons. Less then two years after that we saw an answer. Any sane civilazation is not going to give us their location but the preferred procedure would be to send probes that do not come in direct contact with the young civilazation but observe and study it. The real answer to this problem is to do the same to their probes, they have allowed us to see them. This is all that should be said since any other line of reasoning ends up going down the rabbit hole. We now have that capability to observe and study them without goverment intervention.

    • henry cordova March 18, 2022, 13:49

      I’m not quite sure what you’re getting at. Our ability to advertise our presence to the cosmos (nuclear explosions and focused radar beams) has not had enough time to potentially alert more than a few thousand other stars due to the speed of light, a tiny fraction of the galaxy. And just what happened ‘less than two years after that’ that is supposed to be their response?

      We delude ourselves if we believe anyone knows we’re here, or if they even care.

      • Michael C Fidler March 18, 2022, 23:08

        I don’t think it’s that simple, as in 2001 A Space Odessey, probes may be in all solar sytems that may develop life. What would we be doing a million years from now?
        A plentiful supply of raw material in our asteroid belt to produce probes and AI chips from the main mothership to power them. Best place to hide in our solar system would be the asteroid belt with plenty of camouflage. They do not need to come here for they are already here.
        The UAP probes that the astronomy community is so scared to even seriously investigate is what I’m talking about.

        Do we know that FTL is impossible? No…

        It only needs to be one UFO report to be a real non earth alien object and at least in the USA a 150,000 people have reported them.

        How many people actually report UFO sightings? A reality check.
        November 12, 2018


        National UFO Reporting Center.


        • henry cordova March 19, 2022, 8:25

          I think I understand you now.

          • Michael Fidler March 19, 2022, 10:49

            The difference is I have seen unexplainable UFOs when I was younger thru my telescope after spotting it with my eyes in the evening. Before that happened I was was as most people being a sceptic.
            I had a second group of UFOs with my wife while out observing Jupiter with my 8″ telescope on June of 1983. It was also reported in the newspaper by a sheriff. At the time I worked for the FAA as an ATC and we had a direct line to NORAD and they said that no satellites were reentring in that time period. This was 5 differnt objects passing overhead over a 15 minute period with each having a 30 to 40 degree tail and taking 3 to 4 minutes to rise from the south to the north for each object. Thru the telescope no ablating just a smooth object with a long smooth tail. The first started far to the east and after that disappered the next one rose from the south to the north but further west after two more doing the exact same thing only moving further west the last one went directly over us. No sound and the sky was clear and dark.

            So you see my dilemma, amatuer astronomer since I was 12, 4 years in the Air Force in NORAD and radar sites on the Tonopah Nevada red flag sites next to Groom Lake and 24 years as an FAA ATC. To make matters worst I meet Sir Eric Gary of UFO – United Nations fame back in 1969.

            I take most of what you see in the UFO community with a grain of salt, but there are many competent observations by astronomers and others since the 1940s. So why are we not looking for them? The Galileo Project and the Congress UFO office is a good start but it will take time…

            15 Mar
            NEW: Biden Approves Omnibus Bill, Which Includes Funding For UFO Office, As Growing Evidence Suggests UAP Does Not Reflect Adversarial Technology.


            • Henry Cordova March 19, 2022, 19:56

              I too, am an amateur astronomer. And I too have seen baffling things, naked-eye, through the telescope, and on a Navy radar, that I could not identify or explain. But that doesn’t mean I saw alien spacecraft. There’s a very good reason why they’re called UNIDENTIFIED flying objects.

              Carl Sagan was right on both counts:
              “Absence of evidence is not evidence of absence.”
              “Extraordinary conclusions require extraordinary evidence.”

              I want to believe, too, Michael. That’s why I have to be skeptical. The easiest person to fool is yourself.

              • Michael Fidler March 20, 2022, 6:56

                We will see in the next year or two, but I think the results will be a suprise to many, many people. You sould take a look at the Galileo Project.

                “When a reporter mentioned Sagan’s famous assertion that extraordinary claims require extraordinary evidence, Laukien replied, “We are not at all—listen to us carefully—we are not jumping to conclusions. We are not making extraordinary claims.” Loeb joined in: “Although I’m a theorist, my approach to this is very observational. It is a fishing expedition. Let’s just go out and catch whatever fish we find.”


                75 years of UFO’s is not a giant public hallucination or some goverment/military/industrial complex mad scientist project. World wide we are talking about millions of people of which only a few percent are reported. I myself had no outlet as to how to report what I saw till going to the library in 1986 and finding a obscure book that had contacts in the appendix, that is how I became invoved with MUFON. What I found there covinced me that there is evidence such as vehicle interference reports of slowly rotating magnetic fields arounds these objects. This goes clear back to the orginal 1947 Arnolds report 1947 Kenneth Arnold report:

                Electromagnetic Effects
                Case 30 — June 24, in Cascade Mts., Oregon: On the morning of the same day that Kenneth Arnold made his sighting, a Portland prospector, Fred M. Johnson, saw a loose group of five or six objects in the Cascade Mountains of Oregon. He described them as “round, metallic-looking discs” and said they appeared to have tails, or fins, as they banked in the sun about 1,000 feet overhead. They were approximately 30 feet in diameter and Johnson turned his telescope on one of the objects for a closer look. As he did this, he noticed that the needle on his compass was behaving in an unusual manner, weaving wildly back and forth while the objects were overhead. This strange reaction stopped as soon as the objects moved off to the southeast. They had been in view from 45 to 60 seconds. The Air Force classifies this sighting as Unidentified.

                You see I do not have to believe, I know and all that is needed is a real effort to research these objects. You turned away from finding the truth by saying it does not fit into your world view. But it is a very small world indeed with many small minds, you understand much more then the average Joe so think about it.

                SETI has looked for radio signals for so long without finding anything so why don’t we look a little closer to home. It is that simple! ;-}

                • Ron S. March 20, 2022, 10:58

                  Perhaps Paul, with his many connections, can persuade ET to write a guest article for CD in which they can put forward a convincing argument that they really exist and are here.

                  • Paul Gilster March 20, 2022, 13:22

                    Well, I suppose I can always ask…

                • Henry Cordova March 20, 2022, 11:55

                  Half the people in the world carry very capable cameras (on their mobile telephone) in their pockets.

                  I have yet to see a convincing image of Bigfoot, the Loch Ness monster or a UFO. Perhaps none of those items is manifestly impossible, that is, they violate none of the laws of physics. But that does not mean they have to exist.

                  And as an amateur astronomer, surely you understand that many of the natural celestial phenomena you see routinely an untrained observer often sees as unequivocal evidence of an alien vehicle. Eyewitness reports from lay observers not only misidentify ordinary items, they often describe them totally incorrectly. Eyewitness testimony, even my own, is worthless when used to describe unfamiliar phenomena under stressful circumstances.

                  While we’re going anecdotal, I once watched a routine nighttime launch from Cape Canaveral, about 100 miles away. A friend from out of town (a police officer, supposedly a trained observer) simultaneously witnessed the same event and described it as an alien craft, with windows, erratic maneuvers (including right angle turns!)
                  and bizarre light displays. Eyewitness testimony simply cannot be trusted. It is often mistaken, open to suggestion, and, of course, outright fraud. And after it has been processed and propagated through the press, even a legitimate report is likely to be distorted beyond recognition. An honest reportof a real UFO observation of a bona fide alien spacecraft is likely to be totally unrelated to the actual sensory experience. Its not the kind of event likely to evoke a sober, critical response.

                  You should keep in mind that the UFO phenomenon did not begin with Kenneth Arnold in 1947. There are numerous 19th century reports of interplanetary craft, and they all seem to have one thing in common with contemporary ones: the alleged space ships seem to be based on the technology in use during the time of observation, or based on what the alleged observers suspected might be just over the technological horizon. Victorian UFOs looked like blimps or zeppelins. Ours exhibit evidence of inertialess drives and cloaking devices.

                  I suspect if we ever do encounter a truly advanced extraterrestrial technology, we will not even recognize it for what it is. We will mistake it for a biological, meteorological, or even supernatural phenomenon.

                  Imagine Neolithic man stumbling onto a helicopter.

                  • Alex Tolley March 20, 2022, 16:32

                    Imagine Neolithic man stumbling onto a helicopter.

                    Or how the indigenous population interpreted square-rigged ships arriving in the Americas, or the Spaniards riding horses.

                    There is a great line in the movie: The Hunt for Red October. The sonar operator reports that the Russian submarine is being interpreted as a whale. Why? because that is the default if it cannot recognize the sound.

                    AI systems, when symbolic or neural nets often make the same miss-interpretations, generating an output that is not the correct label for the input. While the technology is “primitive”, object recognition is on a par with human recognition, often much better. Yet errors still happen. Why should we believe humans are infallible when so much evidence suggests otherwise. We have long accepted that recorded information is far better than human recollection in court cases.

                • Alex Tolley March 20, 2022, 12:49

                  You see I do not have to believe, I know and all that is needed is a real effort to research these objects.

                  Without equating the two, can you not see the similarities to those who say the same thing about their belief in the son of the ME god, anecdotal tales of miracles, etc, etc. Reread the last line of Henry’s comment and introspect on this. Skepticism is really important, which is why Feynman emphasized that one must be so careful about fooling oneself. It is so easy, especially if one is primed to expect a certain result.

                  • Michael Fidler March 21, 2022, 1:59

                    You use all the same arguments that I have heard time and again and the same great scientist, Feynman and Sagan and Fermi. It is as old as the hills. Please read UFO reports involving Vehicle Interference by Mark Rodeghier from the CUFOS.

                    The book of 144 pages, is free to download at this address.

                    Please read with an open mind, this is not some fanasty but actual Scientific evidence.

                    And while you are at it take a look at this movie about Galileo Galilei.

                    GALILEO 1975 1080P BLURAY X265-RARBG.

                • Michael Fidler March 20, 2022, 23:32

                  Project Galileo: The search for alien tech hiding in our Solar System.


                  • Adam J Crowl March 22, 2022, 8:18

                    Michael Fidler,
                    The search for ET Artefacts in the Solar System isn’t helped by associating it with bad theorising that is chronic in the UFO community. It’s a completely reasonable extrapolation from our own capabilities to look for ET artefacts in the Solar System. Bracewell Probes, as a concept, are more than 60 years old, while Self-Replicating Space Probes are approaching 45 years of age. It’s not unreasonable to imagine ET “space junk” might collect in stable gravitational wells near the major planets – the L4/L5 Lagrange points for example. It’s not unreasonable to imagine active Space Probes surveilling us by unimaginable means.

                    What is unreasonable is Claims that the UAP’s reported by people time and time again *are* proof positive of technological ET Intelligences taking an interest in us. What’s missing is any solid evidence of that UAP’s are Artefacts. Doesn’t mean there’s no UAP’s – the reports don’t go away – but it does mean that our claims about *what they are* need to be seen as merely working hypotheses to help data-gathering. Nothing more. And, given the variety of the phenomena, it’s really hard to attribute it to *physical technology*.
                    I’ve read enough Jacques Vallee, Patrick Harpur, Carl Jung and Colin Wilson, to name a few, to dismiss the more intra-psychic explanations of the more lurid UAP encounters. Human brains and psyches work in ways we don’t really understand as fully as neuroscientists would like to admit.

                    • Michael Fidler March 22, 2022, 10:30

                      So how many UFOs have you seen? I agree the UFO community sucks, but if just one case is real that is it. Yes, I have seen two times things I can not explain but to classify me with the kooks is retarted. Look, take a camera and system out to look for these objects and stop the stupid BS. That is all I’m saying. That is what is HAPPENING NOW. The idea that you can sweep this under the rug or belittle normal people for what they have seen is retarted. Avi Loeb said this perfectly: “The reason I look for intelligence in space is because it’s hard to find on Earth.”

                    • Alex Tolley March 22, 2022, 13:27


                      Look, take a camera and system out to look for these objects and stop the stupid BS.

                      Isn’t this exactly what the Navy pilots did that caused the recent speculation. And the result was…?

                      As someone else has said, it doesn’t matter how improved the technology gets, the offered records are always fuzzy and ambiguous. That is why they merit being called “unidentified”. NORAD tracks a lot of objects, from aircraft to missiles, to meteors, yet somehow they don’t appear to detect any alien spacecraft. We have satellites offering surface images all over the planet with repeat images every few hours. There are local horizon to horizon recordings of the skies to record meteors and other aerial objects, but again, those alien spacecraft craftily refuse to show up. [Are they deliberately teasing us, as Ford Prefect intimates in THHGTTG?] But not one has captured an alien craft buzzing about. If they did, it would be a sensation.

                      So with the billions of smartphones, large numbers of amateur telescope and binocular users, radars tracking aircraft over continents, still no one has captured an image that shows at least an unambiguous spacecraft.

                      Your previous suggestion to watch a video about Galileo just triggered me. So I just feel I have to provide this link about referring to the great astronomer.

                      The Galileo Gambit

            • Michael Fidler March 20, 2022, 20:03

              I understand where you all are coming from but you very well no what the problem is. Sarcasm is not the answer, I live in a country that has a 95% Catholicism and I respect their beliefs yet I come from a family that goes clear back to the Mayflower. My Parents were the old style liberal Democrat that believed in ecology long before it was a popular. I consider myself a scientist in a world with few.
              All I’m saying is that you can have your skepticism but support a real effort by scientist to study such objects. The benifit is two fold, public support will be very high and spending is minor compared to the billions spent to find life elseware. You want to get to Alpha Centuari, where do you tink the money is coming from? This in an instant could change a world view of sarcasm and dislike because of useless money spent on pet projects to explore space. We are talking millions of dollars not billions for a hurting world that would love to find someone else in this universe…

              • Alex Tolley March 21, 2022, 10:18

                If we take the Kenneth Arnold sightings as the start of the modern era of UFO/UAO/UAP sightings, then 75 years have passed. During this period, there has been zero hard evidence of any alien technology. No crashes, no instruments left behind (a la “Roadside Picnic”), and no good photos or video apart from hoaxers like Adamski. The USAF investigated UFOs during the 1950s and 1960s (Project Blue Book), yet with the resources they could command, no evidence of alien craft or technology was discovered. Today, almost everyone carries a multi-megapixel camera and video recorder in their pocket, and yet there are still no good unambiguous sightings. The recent navy “sightings” were effectively explained as terrestrial craft and misinterpretations of what was observed. I don’t expect any new government investigation will come up with anything new.

                When I was at school in the 1960s, there were many books on strange phenomena, from UFOs, ancient aliens, psychic phenomena, spirits, etc, etc. Not one panned out despite scientific and amateur investigation. The late James Randi was able to make a career exposing frauds and debunking perceptions of psychic phenomena. Yet the likes of the aging Uri Gellar still do performances for believers. In the meantime, science and technology have hugely advanced since then.

                Like religion, followers of such phenomena can be summed up as “I want to believe”. No amount of evidence will convince believers that their beliefs are wrong. On the contrary, contrary evidence hardens those beliefs. QAnon is a perfect example of this in the modern era.

                We like to think we live in the Enlightenment Age, but for most people, this way of thinking does not take. Wealth and education don’t seem to help, as surveys of beliefs in a host of phenomena (e.g. angels, UFO abductions) demonstrate. Science works by carefully testing observations and paring away bad hypotheses. The recent analysis of the radio “signals” from the direction of Proxima Centauri shows how this is done. ETI may be out there, but so far there is no evidence that this is the case. Keep an open mind, but don’t succumb to believing ETI must be there, if only we try looking harder, as that is just wishful thinking. No amount of playing games with math substitutes for hard evidence. Similarly, no amount of unidentified phenomena, anecdotal, fuzzy images, and video, substitute for hard evidence. [I do wonder when deep fakes of hard evidence will be created like some of PK Dick’s stories, the modern equivalent of religious artifacts like wood from the crucifixion cross, or the bones of saints, or the Turin Shroud.]

                As a sci-fi movie fan, the opposite is demonstrated by the British army’s Colonel Breen in “Quatermass and the Pit”. No amount of hard evidence uncovered by Roney and investigated by Quatermass can change Breen’s mind that the buried artifact is not a Nazi V weapon. His is a closed mind, unchangeable by evidence.

                • Henry Cordova March 21, 2022, 15:59

                  Some things just have to be believed to be seen.

                  • Adam Crowl March 22, 2022, 8:01

                    Any Claim or Theory that demands belief without evidence isn’t worth believing. That being said, there’s plenty of things we can believe to be true and yet can not see, ever, with our physical eyes. Many mathematical proofs describe the unseeable, yet can be believed without contradiction. They’re known by logical argument, not by sense data. Similarly many physical phenomena can *only* be known by their effects, not seen directly.

                    Unlike the many, many Extraterrestrial Artefact theories about what UAP’s are, which are touted as explanations of experienced visible phenomena that are *untestable* and usually make no sense at all. It’s the assertion of facticity of such Claims or Theories, that really only tangentially explain the phenomena, which trained sceptics, like scientists, have trouble with. Especially when UFO groupies and odd-balls claim telepathic communications with the occupants of the theorised Artefacts, while others claim their Free-Energy Machine (FEM) or Low-Energy Warp Drive (LEWD) is based on the UAP propulsion system, or more commonly, the UAP’s are *proof* the FEM/LEWD works.

                    Good theories explain the phenomena and lead us to new potential or actual observables. Bad theories lead us to span abysses of ignorance with very narrow planks of evidence indeed.

                • Robert March 22, 2022, 14:21

                  Personally, I am amused by the dichotomy between the modern scientific view of suggesting the universe likely is teeming with life and at the same time ridiculing the idea that such life may have or may be interacting with our civilization in some way. I understand the reasons but still think it’s rather inconsistent. We don’t really know how to travel to the stars yet so we assume no one else has been able to either. If we suddenly learned how to do what now seems impossible we would likely reevaluate many UFO claims as possibly true.

                  • Michael Fidler March 23, 2022, 8:54

                    Yes, they do not understand the point. But what I hate the most is thier useless BS that you have to wade thru with hip waders. Planet of the Apes is a good analogy.

              • Michael Fidler March 24, 2022, 9:36

                Alex Tolly I work at NORAD and the system used a SAGE computers that had data sent in from radar sites used both by NORAD and the FAA. The computer was on the third floor of a 100 x 100 foot building with 5 foot thick walls. This computer took up that whole third floor and was developed by IBM in the late 1950s and the logic circuit was vacuum tube. You are the one that has the fantasy about how well we track objects.

                I also worked on the ranges in Nevada when the stealth aircraft was developed and used a Russian SAM – 4 radar system to see how well they could be tracked. The milatary does not track meteors! You have very limited knowledge of what capabilities the milatary has. When was the last time you read Aviation Week & Space Technology? Cell phone cameras can not photograph ufo’s because they are not mouted on a tripod. You see the problem is there are very few deticated systems that can track fast moving dim objects in enough detail and the milatary does have these systems but they definitely are not going to tell the public what they have picked up because then the advesaries know what they are capabile of. I sorry to tell you but when I was in the Air Force it was known as the Air Farce, but they are doing much better now… :-}

                • Alex Tolley March 24, 2022, 20:27

                  Cell phone cameras can not photograph ufo’s because they are not mouted on a tripod.

                  So you are saying that cellphone cameras are worse that pointing a film camera at an aerial object? That a “hovering” object cannot be captured on a cellphone camera? What about a spaceship that has landed? Current cellphones can compensate for lightlevels and capture objects in low light conditions, and there are cellphone video of unidentified lights in the sky.

                  As for Norad, it was my understanding that Norad can track objects in orbit as small as about 10cm. If that is the case, then there should be no difficulty recording meteroid entry into Earth’s atmosphere. They have to be able to distinguish between missiles and natural objects. Granted that there are now better public facilities for tracking meteroids to estimate where they hit the ground.

                  But let’s take your argument as correct, that the military cannot record good quality images or video of moving objects. That is why they are unidentified. There should be no reason to jump to the conclusion that they could be, or are, alien spacecraft, as you appear to do.

                  • Michael Fidler March 25, 2022, 10:07

                    A 10cm object as it passes directly overhead, the NORAD Radar Fence only picks up objects in orbit around the earth. There are versions of this in Australia and several other places around the globe. As for pictures there are thousands of UFO pictures including many cell phone images. You and your blinders cause you to be lead around without seeing. I dare you to research UFOs seriously for one year and see what find out, I’m not talking about the internet but the many technical papers on effects such as EM and how they may work. There is a lot of information out there but you have to be smart enough to find it. You are like the Titanic.

                    • Alex Tolley March 25, 2022, 12:54

                      As for pictures there are thousands of UFO pictures including many cell phone images.

                      Then why did you state that cellphone cameras are of no use unless they are mounted on tripods? Doesn’t the same apply to film cameras…and naval airplane-mounted cameras?
                      AFAIK, Norad doesn’t just track orbital objects, but also missiles reentering the Earth’s atmosphere presumably potentially to hit targets. Even if that isn’t the case, there are so many other military installations that track missiles and aircraft flying at speeds ranging from teh subsonic to hypersonic that one might think that there just might be enough information to determine if an object was under control or just on a ballistic trajectory, like a missile or meteor.
                      As with the naval aviator videos, despite the resources to track and chase objects, we still get poor quality, ambiguous evidence. If the military continues to be so awful at this, why do we keep spending so much on them? WWII camera technology was good enough to identify V-1s and V-2s, yet 3/4 of a century later, with far more surveillance from the ground and in orbit, we still cannot get any definitive evidence.

                      Is ET so good it is like watching Catwoman stealing jewels after balletic moves to evade a dense criss-cross of IR beams surrounding the plinth? In this day and age, a Terminator cannot materialize in a near-empty alley, or Picard beams down to a 2024 empty alley in LA without a surveillance camera picking up the event. Stealth gets ever more difficult, and yet…

                      As regards papers on UFO technology. I well recall an absurd explanation of potholes in soil being formed by anti-gravity beams. This was in connection to crop circles, now known to be hoaxes. Ufology brings out the cranks. If there is any signal in the junk, the signal to noise ratio is minuscule.

                    • Michael Fidler March 25, 2022, 21:10

                      Ok enough said, but I leave you with two good news on the subject;

                      Obama’s Presidential Library Has Thousands of Files on UFOs.


                      “Chance of Impact 100%” – Fifth Asteroid Ever Discovered Before Impact.


                      Flyeye telescope.




                      This should have a good chance of picking up any object coming in from deep space. With the large number of wide field nightly surveys coming into existence and the Galileo Project’s effert to build there own AI system there should be some firm evidence coming in. Hopefully in the not to distant future! :-)

  • Alex Tolley March 18, 2022, 13:04

    Reading through the Wright et al paper, there are obvious biases to push Lt > Lb, and techno-signature strength and unambiguity >= biosignatures. I think there is a relatively easy case to write a rebuttal paper showing the reverse.

    One example is that Lb on Earth is limited due to the increasing luminosity of the sun. The assumption that plants will fail as photosynthesis becomes impossible due to low CO2 partial pressures and thence all heterotrophic life will also disappear is true only in so far as we have a dryland mentality to life. CO2 will still be abundant in the oceans and therefore Earth may come to resemble its pre-continental colonization state, with life confined to the oceans. Even as the planets heat further, and the oceans evaporate, microbial life will continue to exist in the crust, and conditions more like the Archaean will reappear.
    Yes, those biosignatures will be harder to detect, but the lifetime of life will not be stopped until the planet is heated to beyond tolerance in the crust, like Venus. But after 6 – 8 bn years, will Lt really be greater than Lb for any given world?

    The other obvious bias is that technology will be primarily used to create new technology seeds/bases on other worlds. We cannot know this. It may be just as likely that seeding biospheres is more common than maintaining technological worlds. Life can be expected to continue for gigayears once established, but we have no idea how long technological biological/post-biological civilizations and/or artifacts can last. Suggesting otherwise is just biased techno-optimism.

    As PG writes in the post:

    Nor can we rule out the possibility that the Earth could develop other species beyond our own in the future that can produce a technological society following humanity’s extinction. For that matter, are we so sure about our past?

    If there was a technological civilization in Earth’s past, we have been unable so far to find any techno-signature associated with that civilization. That would argue against Lt being long-lived, whether extant as a civilization or artifacts. Better to assume we are the first Hitech civilization and our longevity is an unknown, and even if it continues for another 4 bn years, Lb > Lt will remain that case.

    • Ron S. March 18, 2022, 20:26

      I haven’t read the paper, so I am solely relying on what I read here. My understanding of Lt and Lb is that it is a comparison between apples and oranges. It appears to assume that detection is “passive”. That is, we detect most biological life by it affect on biospheres and other radiation sources (e.g. star light filtered by an atmosphere).

      Technological life certainly has passive characteristics, however I doubt that is the important metric. Technological civilizations are active signalers as well, and that may be the dominant mode for detection, whether the signals are incidental or directed (at us).

      Unfortunately, the latter is impossible to estimate since it requires a raft of assumptions. That is what makes SETI so fraught. But we can’t ignore the active mode of detection when comparing Lt and Lb, nor can we solve for the probabilities due to the lack of data.

      Passive detection, at least, requires fewer assumptions. You decide what to look for and gather the data. For active detection we can probably do little better than to wait and wait, and then wait some more.

    • Henry Cordova March 18, 2022, 23:17

      Could there have been an earlier technical civilization than ours on Earth in the distant past? Could there be another to pick up after us if we are wiped out? Will they find evidence of us? Granted, all of our artifacts may eventually be erased (even plastics eventually decompose) or buried by plate tectonics, ice ages, vulcanism or sedimentary deposition and sea level changes. But we also know even delicate plant and and animal tissues have been preserved as fossils for millions of years.

      • Alex Tolley March 19, 2022, 10:46

        Supposedly the Anthropocene will leave material evidence in the rocks, most notably concrete. There will be other, more subtle evidence that we will detect, from changes in atmospheric gases, ecosystem changes, refined metals that avoided slow oxidation, etc, etc. For a future civilization that has space travel, the artifacts that still survive in space and on the Moon will be clear evidence.

        But AFAIK, there is absolutely no evidence of any sort that there was a prior civilization. Of course, such a civilization may have been simple, spatially limited, and therefore hard to find.

        I see no reason why another civilization couldn’t emerge after ours. It could be a rebirth of human civilization after an interregnum, or a new species of ape after many millions of years of evolution that drives them into the cognitive trick we received. They might have to develop very different technologies, and they may not ever develop a science-based technological society, but be stuck at a simpler level like the many pre-industrial civilizations/cultures that have come before us.

        • Henry Cordova March 20, 2022, 15:46

          When they were putting in the railroads in Florida about a century ago, there was a lack of local stone suitable for the railroad beds.

          The railroads imported crushed granite from Georgia (the same stuff Stone Mountain is made of), broke it up into fist-sized lumps, and laid the tracks and ties on top of that.

          I’ve often wondered, in the far distant future, how the geologists of whatever species replaces us will explain these long linear igneous features embedded in the ancient sedimentary marine deposits of the state. The rails and spikes will have rusted away, and the ties will have long rotted and crumbled to dust. All that will remain is crushed granitic cobbles arranged in long, narrow ribbons criss-crossing the state for hundreds of miles.

          No doubt our successors will devise elegant geological theories to explain these anomalies.

          • Alex Tolley March 21, 2022, 11:57

            I love that example. I suspect there are many, from regularly cut stone to stone that was transported a long distance that was not due to glaciation, like the “bluestones” at Stonehenge.

            Concrete, of course, is an unnatural mix of materials, especially if it is mixed with plastic fibers for strength. Plastic fibers in concrete might be as distinctive as the iridium layer from the KT impact.

            Even if all the metals corrode, I cannot help but think that strange lines of iron, aluminum, or copper oxides in the rocks might be intriguing to geologists in the deep future. Similarly, if they come across spent nuclear fuels that were stored in mines that long since collapsed and were crushed.

            What would paleontologists think of huge numbers of bovine and chicken bones in the fossil beds that appear and disappear rapidly? Highly successful species that populated the planet before going extinct? Would any DNA fragments be recoverable that show linkage to evolved animals and birds in the future? As all these pieces of evidence would be planet-wide, despite the continents being separated, would be possible evidence of a prior civilization. Every so often a manufactured artifact would be recovered that would dispel any doubt that a previous global industrial civilization had been extant in the deep past.

      • NS March 21, 2022, 3:54

        One argument against an earlier widespread technical civilization is that when our own developed, there were easily available deposits of coal, iron, petroleum etc. An earlier civilization like ours would have used these up. For the same reason, a technical civilization subsequent to ours might have a much more difficult time developing than we did, because we have used up the easily available resources that helped us get started.

        • Alex Tolley March 21, 2022, 11:40

          Prior pre-industrial civilizations did not use fossil fuels. We should not define civilizations as having to be industrial/scientific, but rather just having a culture and reasonable geographic range, and building cities (the origin of the term). So think of Egypt, Minoan, Greek, Persian, Rome, Maya, etc. Greece could have eventually powered its civilization with solar thermal power, they were playing with the parts. Windmills, used by several cultures, could have eventually been developed into wind turbines. They would eventually have reached a stage where we are headed after decarbonizing our energy systems. There is certainly enough thorium for nuclear reactors, and if fusion is possible, then there is no shortage of deuterium.

          So a future civilization could arise that is technological, bust not based on taking the initial steps using fossil fuels as we did.

  • Adam Crowl March 18, 2022, 22:18

    Hi Paul
    On the Galactic Technosignature question, I think the lack of evident changes to natural process might indicate that Intelligences universally find a compelling reason to abandon the Milky Way for greener pastures. The inexorable dispersal of the Galaxies via Dark Energy makes our Local Group the cosmic Boondocks. We should be looking for departing “Starships” making the long trek to Virgo or similar large Galactic Clusters. To achieve the right speed, I think compact binaries thrown around the Galactic Core Black Hole (GCBH) for a Dyson boost will be the means of choice, so sufficient resources are available for a multi-billion year journey. White dwarf stars would be able to get very close to the GCBH, being immune to the tidal stresses around a 4.3 million solar mass BH. Whether hyper-velocity White Dwarfs are visible to our present instruments, I’m not sure, but they’re definitely worth looking for.

  • Robin Datta March 18, 2022, 23:57

    And David Kipping’s thoughts on related matters:
    The Problem With “The Rare Earth Hypothesis”

    • Alex Tolley March 19, 2022, 11:25

      A very good video. The importance of evidence is key. The only thing I disagree with is that he seems to conflate beliefs (i.e. evidence-free firm ideas) with speculation (evidence-free play of ideas). While these need not be binary, the first is hard to change, while the latter tends to be more flexible in the face of evidence. But more importantly, speculation helps refine how we search for evidence. In the case of the Rare Earth Hypothesis, if we look for rocky worlds like ours with and without large moons, there should be some statistical difference in the presence of life between the 2 cases. Similarly with the other factors. So extensive biosignature evidence (“stamp collecting”) should help us in our search for life and intelligence. Of course, we still only have observable data that we can use, so if life exists in subsurface oceans of icy moons, we cannot observe that in other star systems with the technology we currently use. [Maybe one day we can “feel the force! ;) ]

    • Abelard Lindsey March 20, 2022, 11:59

      The one thing I think the Rare Earth theory does get right is the need for plate tectonics. Planets lacking plate tectonics cannot form biospheres. The open question is if the moon-forming giant impact modified the Earth such that plate tectonics could happen, whereas if that impact had not happened there would be no plate tectonics and no us. This question should be answered.

      • Alex Tolley March 20, 2022, 16:34

        Does that imply that we can definitely rule out subsurface ocean biospheres in icy moons? If so, could we reduce the funding for such a search and redirect it to more interesting targets?

        • Andrei March 22, 2022, 6:22

          Abelard’s reasoning is correct for terrestrial planets, Europa most likely got quite a bit of recycling from geologic processes – while those be a degree less dramatic than on Io it might be enough to return the material to the potential biosphere there. On Titan some compounds are constantly renewed as they’re made in the atmosphere. Which provide another loophole. But this is also the reason I am more skeptical to the idea of life on worlds like Enceladus, and even more so for other moons and worlds, even though they seem to have a shell of water around the core. For the latter ones, we might indeed spend our resources on more interesting targets. Even on Europa, that possible life might only be found in oases near vents providing nutrients and heat. While the rest of the ocean, only contain spores or any counterpart which might be hard to distinguish from just a presence of organic chemistry with the instruments we one day will send there.

  • Afterthought March 19, 2022, 0:33

    The amazing thing about technosignatures and biosignatures is their complete and total absence.

    We havent looked everywhere, but we’ve looked enough to know that the universe isn’t “fine tuned” for life.

    • Alex Tolley March 19, 2022, 10:52

      “fine tuned for life” may be a necessary, but insufficient condition for life. We cannot exist without these constants, but they are not the only conditions needed for life to emerge.

    • Adam J Crowl March 19, 2022, 19:41

      Biosignatures are yet to be observable in other star systems so we don’t yet have any data one way or the other. As for technosignatures, see above.

  • Thomas R Mazanec March 19, 2022, 9:23

    If we launch a self-replicating probe only every 500,000 years, we nonetheless set up a process of such crossings that fills a large percentage of stellar systems in the galaxy within a time frame of tens of thousands of years

    Tens of thousands of years? The galaxy is larger than that in terms of light years.

  • Joe H. March 19, 2022, 11:00

    “humanity is the first species on Earth that can prevent its own extinction with technology.” Yes, but other species have prevented extinction with just plain old reproduction. Cock roaches come to mind.

  • Abelard Lindsey March 19, 2022, 15:08

    Garden worlds such as our own are special. Of course any advanced civilization will seek to expand into space via some variant of the O’neill scenario, Over time the bulk of industrial activity will be space-based simply because the space-based resources of any given solar system will be many magnitudes of order greater than that of a single garden world, and any such civilization would want to preserve their garden world in a relatively natural state.

    It is silly to believe that any advanced civilization would remain confined to their home planet.

  • GeordieTwo March 20, 2022, 16:31

    With UFO’s, aerial sightings of unidentified phenomena just aren’t enough. We need physical, tangible evidence. Now I know many will say we already have such evidence but it’s all hidden away by various governments. To me this is just too convenient. Again let’s see the extraordinary evidence.

  • Michael Fidler March 21, 2022, 4:49

    Lightsail technology billows into the future.

    Alpha Centauri seems almost within grasp as promising research soars into reality.
    By Samantha Hill | Published: Thursday, March 17, 2022

    Progress with Breakthrough Starshot
    The Starshot Initiative is still in the very early stages of development. But since the project got off the ground in 2016, Avi Loeb — chairman of Starshot’s advisory committee and professor of astronomy and cosmology at Harvard University — doesn’t think they’ve encountered any dealbreaker technological challenges, or what he likes to call “showstoppers.”

    In fact, Loeb said the lightsail’s development has seen the most progress, while developing the communication aspects of the mission has been far more challenging. He explained that the transmission of information becomes much dimmer over light-year-scale distances, not to mention it would take a touch over four years for the signal to reach Earth.

    More than $100 million has been allocated to the Breakthrough Starshot project for the next decade, or more, of research. However, Loeb believes the investigation could take at least another couple of decades, and possibly be one of the most expensive space endeavors we have ever seen.

    But for him it’s a worthy investment. Not only will the technological advancements produced by the Breakthrough Starshot project ripple out through the real world here on Earth, Loeb believes knowing what is outside of our solar system is important for future generations.

    “We want to see that we aren’t the smartest kids on the cosmic block,” Loeb said.


  • ljk March 21, 2022, 12:31

    What if the same spacecraft studied mysterious icy bodies and the cosmos as well?

    By Meghan Bartels published about 7 hours ago

    What can a spacecraft armed with cubesats and an astronomical telescope accomplish?


  • Michael Fidler March 22, 2022, 0:09

    Aliens, UFOs and government files: Meet the Harvard astronomer who says aliens have already visited us.


    “Human history is very often driven by a group of people feeling superior to another group of people. If we find that we are not the smartest kid on the cosmic block, it will give us a different perspective. All the differences between humans will become irrelevant.”

    Prof Loeb believes he will find proof of extraterrestrial life in his lifetime.

    “The reason I look for intelligence in space is because it’s hard to find on Earth.”

  • Michael Fidler March 22, 2022, 5:20

    These 4 signs of alien technology could lead us to extraterrestrial life.

    “Pioneering scientists think we should start looking for extraterrestrials in a whole new way: by seeking out alien technology.”

    I like the last one especially the last paragraph!

    Wormhole transport systems.

    “A sufficiently advanced civilisation might be able to manipulate space-time itself to create wormholes. These shortcuts through space-time – which are permitted to exist by Einstein’s theory of gravity – could enable a galaxy to be crossed in the blink of an eye.

    Intrinsically unstable, a wormhole would need ‘stuff’ with repulsive gravity to hold open each mouth, and the energy equivalent to that emitted by an appreciable fraction of the stars in a Galaxy. We know such stuff exists because it is speeding up the expansion of the Universe in the guise of dark energy, though its gravity is too weak to prop open a wormhole.

    If ETs have created a network of wormholes, it might be detectable by gravitational microlensing. This occurs when a celestial object passes between us and a distant star and its gravity briefly magnifies the light of the star.

    If the object is a wormhole, the pattern of brightening and fading of the star is distinctly different, according to Prof Fumio Abe of Nagoya University in Japan. “If the wormholes have throat radii between 100 and 10 million kilometres, are bound to our Galaxy, and are as common as ordinary stars, detection might be achieved by reanalysing past data,” he says.”


    Gravitational Microlensing by the Ellis Wormhole.
    F. Abe

    Good visualization in Fig. 4 of microlensing of a wormhole compared to regular star.

    Some thoughts on the subject;

    Can a Wormhole Generate its Own Magnetic Field?
    What about large scale wormholes?


    What about Magnetars could they be the opening for a wormhole since they are close to black hole mass.

    Could a double wormhole be formed from a binary magnetar?

    Would there be advantages to binary wormholes with slowly rotating magnetic fields?

    Remember, Extraterrestrial civilizations would have studied the process of stellar collapse from neutron stars and magnetars to wormholes in great detail…

  • Michael Fidler March 23, 2022, 9:17

    Cosmic Collisions Yield Clues about Exoplanet Formation.

    Low levels of bombardment reveal that the TRAPPIST-1 system probably grew quickly.


    An upper limit on late accretion and water delivery in the TRAPPIST-1 exoplanet system.


    “We wanted to figure out how much space junk—meaning, leftover asteroids and comets—could have bombarded the TRAPPIST-1 planets. A key piece of our study was to calculate exactly how fragile the system’s orbital resonances are. It turns out the resonances are extremely easy to break. When an asteroid or comet collides with a planet, or even just passes close by, the planet’s orbit shifts a little. Add up a few of these shifts and the orbits of neighboring planets are spread apart enough far enough to lose their resonance. From that point onward, they can never realign again.”

    The paper makes a point of ‘resonance’ would be broken by a large impacter and therefore the asteroids, comets, moons must have all been eaten up by the planets from the initial gaseous planet-forming disk. Sounds hard to believe and a major flaw is the system does not exist in a vaccum but goes thru the arms of the milky way and its numerous clouds, rouge planets, interstellar comets and asteroids. A system 5 to 10 billion years old, this would a good place to look for a ancient exterestrial civilazation for that is the only way this system could be that stable for that many years… ;-}

  • ljk March 23, 2022, 13:57


    [Submitted on 18 Mar 2022]

    Setigen: Simulating Radio Technosignatures for SETI

    Bryan Brzycki, Andrew P. V. Siemion, Imke de Pater, Steve Croft, John Hoang, Cherry Ng, Danny C. Price, Sofia Z. Sheikh, Zihe Zheng

    The goal of the search for extraterrestrial intelligence (SETI) is the detection of non-human technosignatures, such as technology-produced emission in radio observations. While many have speculated about the character of such technosignatures, radio SETI fundamentally involves searching for signals that not only have never been detected, but also have a vast range of potential morphologies.

    Given that we have not yet detected a radio SETI signal, we must make assumptions about their form to develop search algorithms. The lack of positive detections also makes it difficult to test these algorithms’ inherent efficacy.

    To address these challenges, we present Setigen, a Python-based, open-source library for heuristic-based signal synthesis and injection for both spectrograms (dynamic spectra) and raw voltage data.

    Setigen facilitates the production of synthetic radio observations, interfaces with standard data products used extensively by the Breakthrough Listen project (BL), and focuses on providing a physically-motivated synthesis framework compatible with real observational data and associated search methods.

    We discuss the core routines of Setigen and present existing and future use cases in the development and evaluation of SETI search algorithms.

    Comments: 14 pages, 3 figures. Accepted for publication in AJ

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:2203.09668 [astro-ph.IM]
    (or arXiv:2203.09668v1 [astro-ph.IM] for this version)


    Submission history
    From: Bryan Brzycki [view email]
    [v1] Fri, 18 Mar 2022 00:31:02 UTC (1,246 KB)


  • ljk March 23, 2022, 13:59


    [Submitted on 16 Mar 2022]

    Opportunities for Technosignature Science in the Astro2020 Report

    Jacob Haqq-Misra, Sofia Sheikh, Manasvi Lingam, Ravi Kopparapu, Adam Frank, Jason Wright, Eric Mamajek, Nick Siegler, Daniel Price, the NExSS Working Group on Technosignatures

    The Astro2020 report outlines numerous recommendations that could significantly advance technosignature science. Technosignatures refer to any observable manifestations of extraterrestrial technology, and the search for technosignatures is part of the continuum of the astrobiological search for biosignatures.

    The search for technosignatures is directly relevant to the “World and Suns in Context” theme and “Pathways to Habitable Worlds” program in the Astro2020 report.

    The relevance of technosignatures was explicitly mentioned in “E1 Report of the Panel on Exoplanets, Astrobiology, and the Solar System,” which stated that “life’s global impacts on a planet’s atmosphere, surface, and temporal behavior may therefore manifest as potentially detectable exoplanet biosignatures, or technosignatures” and that potential technosignatures, much like biosignatures, must be carefully analyzed to mitigate false positives.

    The connection of technosignatures to this high-level theme and program can be emphasized, as the report makes clear the purpose is to address the question “Are we alone?” This question is also presented in the Explore Science 2020-2024 plan as a driver of NASA’s mission.

    This white paper summarizes the potential technosignature opportunities within the recommendations of the Astro2020 report, should they be implemented by funding agencies. The objective of this paper is to demonstrate the relevance of technosignature science to a wide range of missions and urge the scientific community to include the search for technosignatures as part of the stated science justifications for the large and medium programs that include the Infrared/Optical/Ultraviolet space telescope, Extremely Large Telescopes, probe-class far-infrared and X-ray missions, and various facilities in radio astronomy.

    Comments: Unsolicited white paper by the NExSS Working Group on Technosignatures, 11 pages

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

    Cite as: arXiv:2203.08968 [astro-ph.IM]
    (or arXiv:2203.08968v1 [astro-ph.IM] for this version)


    Submission history
    From: Jacob Haqq-Misra [view email]
    [v1] Wed, 16 Mar 2022 22:18:52 UTC (163 KB)


  • ljk March 24, 2022, 18:14

    MARCH 24, 2022

    Next-generation telescopes could search for intelligent civilizations directly

    by Evan Gough, Universe Today


    To quote:

    Deeper into the white paper, things get a little murky. X-ray probes could detect technosignatures, but the authors say the topic warrants further investigation. They say X-rays are “… not a promising ‘messenger’ for artificial signals from ETIs since the latter are conventionally associated with radio (and optical) wavelengths.” But X-rays are still intriguing because of the novel ways an advanced civilization could use them to create signals.

    “If a km-sized rock were to be hurled onto the surface of a neutron star, it may result in an intense X-ray pulse of ~1029 W that might be detectable throughout the Milky Way.” That might sound far-fetched, but who knows? They also say that an advanced civilization could use their technology to modulate existing X-ray sources like X-ray binaries to send signals.

    • Michael Fidler March 25, 2022, 1:37

      There is a very good reason X-rays for interstellar communications;



      X-rays might be a better way to communicate in space.


      Interstellar communication. VI. Searching X-ray spectra for narrowband communication.

      We have previously argued that targeted interstellar communication has a physical optimum at narrowband X-ray wavelengths λ≈1nm, limited by the surface roughness of focusing devices at the atomic level (arXiv:1711.05761). We search 24,247 archival X-ray spectra (of 6,454 unique objects) for such features and present 19 sources with monochromatic signals. Close examination reveals that these are most likely of natural origin. The ratio of artificial to natural sources must be <0.01%. This first limit can be improved in future X-ray surveys.


  • ljk March 25, 2022, 15:43

    Dropping a big rock on a neutron star might be problematic if such beings as the Cheela really exist:



  • ljk March 30, 2022, 10:27

    Astronomers Come up With a New Message to let the Aliens Know we’re Here

    On Nov. 16th, 1974, the most powerful signal ever beamed into space was broadcast from the Arecibo Radio Telescope in Puerto Rico. Designed by famed SETI researcher Frank Drake (creator of the Drake Equation) and famed science communicator Carl Sagan, the broadcast was intended to demonstrate humanity’s level of technological achievement. Forty-eight years later, the Arecibo Message remains the most well-known attempt to Message Extraterrestrial Intelligence (METI).

    To mark the occasion, an international team made of researchers led by Jonathan H. Jiang of NASA’s Jet Propulsion Laboratory has come up with a new signal! Known as The Beacon in the Galaxy (BITG) message, this updated signal combines aspects of the original Arecibo Message with every METI attempt made to date – like the Pioneer Plaques, the Voyager Golden Records, and the Evpatoria Transmission Messages (ETMs).

    Full article here:


    The Beacon in the Galaxy paper:


    To quote:

    “The main part of the beacon in the Galaxy (BITG) Message contains a new combination of graphical information in the form of images and special “alphabets” to represent numbers, elements, DNA, land, ocean, human, etc., similar to the 1999/2003 Cosmic Call by Stephane Dumas and Yvan Dutil,” said Jiang. As Li added, the Beacon relies on the same mathematical language as Arecibo:

    “The BITG message starts and ends with a prime number set (2, 3, 5, 7, 11…) to let itself stand out from the EM waves that can be easily picked up by extraterrestrial intelligent (ETI) civilizations. A new mechanism in message design may help ETI to decode our message: the Row Length Indicator (RLI), which is a repetition of a designated number of zeros and ones. The original Arecibo message is a rectangular block with the same number of elements per row. With RLI, the message can be made of several matrices of zeros and ones in different sizes that enable more flexibility to the content design and decode by ETIs.”

  • ljk April 5, 2022, 13:36


    COSMIC: All Antennas at the Very Large Array Ready to Stream Data for Technosignature Research

    Source: SETI Institute

    Posted April 4, 2022 11:24 PM

    COSMIC SETI (the Commensal Open-Source Multimode Interferometer Cluster Search for Extraterrestrial Intelligence) took a big step towards using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) for 24/7 SETI observations.

    Fiber optic amplifiers and splitters are now installed for all 27 VLA antennas, giving COSMIC access to a complete and independent copy of the data streams from the entire VLA. In addition, the COSMIC system has used these links to successfully acquire VLA data, and the primary focus now is on developing the high-performance GPU (Graphical Processing Unit) code for analyzing data for the possible presence of technosignatures.

    COSMIC is a collaboration between the SETI Institute and the National Radio Astronomy Observatory (NRAO), which operates the VLA, to bring a state-of-the-art search for extraterrestrial intelligence to the VLA for the first time. As the VLA conducts observations, COSMIC will enable SETI Institute scientists to access that data to analyze for evidence of technosignatures, signs of technology not caused by natural phenomena.

    “Having all the VLA digital signals available to the COSMIC system is a major milestone, involving close collaboration with the NRAO VLA engineering team to ensure that the addition of the COSMIC hardware doesn’t in any way adversely affect existing VLA infrastructure,” said Jack Hickish, Digital Instrumentation Lead for COSMIC at the SETI Institute. “It is fantastic to have overcome the challenges of prototyping, testing, procurement, and installation – all conducted during both a global pandemic and semiconductor shortage – and we are excited to be able to move on to the next task of processing the many Tb/s of data to which we now have access.”

    There are several advantages to conducting SETI research with the VLA:

    The size of the VLA: Each of the VLA’s 27 antennas is 25 meters in diameter, spread over 22 miles

    The VLA has a combined collecting area equivalent to a single-dish antenna of 130 meters across

    Each VLA antenna has 8 cryogenically cooled receivers covering the radio spectrum continuously from 1 to 50 GHz

    Some receivers can operate below 1 GHz down to 54 MHz, a band used on Earth for television broadcasting

    Once up and running, it is estimated that COSMIC SETI will observe about 40 million galactic star systems in two years. It will be the most comprehensive SETI observing program undertaken in the Northern Hemisphere, with high sensitivity and a huge target list.

    “I am excited by the ability of COSMIC to conduct the most comprehensive technosignature search ever in the Northern Hemisphere,” said Cherry Ng, SETI Institute COSMIC Project Scientist. “We will be able to monitor millions of stars with a sensitivity high enough to detect an Arecibo-like transmitter out to a distance of 25 parsecs (81 light-years), covering an observing frequency range from 230 MHz to 50 GHz, which includes many parts of the spectrum that have not yet been explored for ETI signals.”

    The system should be fully operational by early 2023 and will conduct its first major observational campaign in parallel with the ongoing VLA Sky Survey (VLASS).

    “We look forward to partnering with the SETI Institute on this exciting initiative and are pleased to see this important milestone in the technical work that will make this new science possible,” said NRAO Director Tony Beasley.

    About the SETI Institute

    Founded in 1984, the SETI Institute is a non-profit, multi-disciplinary research and education organization whose mission is to lead humanity’s quest to understand the origins and prevalence of life and intelligence in the Universe and to share that knowledge with the world. Our research encompasses the physical and biological sciences and leverages expertise in data analytics, machine learning and advanced signal detection technologies. The SETI Institute is a distinguished research partner for industry, academia and government agencies, including NASA and NSF.

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