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Looking for ‘Technosignatures’

We speculated yesterday that categorizing civilizations on the basis of their power use may not be a given, though it is the basis of the familiar Kardashev types. It seems natural to a rapidly changing technological society like ours that the trend is always upward, a clear path toward harnessing the energies of the home planet, then the Sun, then the galaxy.

That this may not be the case seems to go against the grain of ‘Dysonian SETI,’ which looks for, among other things, artifacts as large as Dyson spheres and other astro-engineering projects on massive scales. Or maybe not, for some engineering involving adjustments to planetary environments may well produce observables. We just have to be aware of the range of possibilities here, and recognize our own limitations in trying to figure them out.

For we’ve learned something else from technology, and that is that its components grow ever smaller. Working at nanotech scales to create things from the ground up isn’t beyond the imagination, and engineering that recedes into the background so as not to be visibly apparent is even now gaining traction. The kind of voice recognition and rudimentary intelligence built into my Google Pixel hides its complexities in a small package. I speak into the air and tap the resources of computer clusters that are located who knows where.

What would a stable, space-faring civilization that has gone through its own version of the Anthropocene and reached a societal maturity look like when viewed from afar? Working these themes in Earth in Human Hands (Grand Central, 2016), David Grinspoon is anxious to reconcile our human activities through technology with the long-term survival of the planet, an outcome he believes, with a refreshing optimism, is likely to occur.

As we’ll see, it’s also an outcome made possible by going off-planet, for we cannot turn our back on the technologies that have the power to transform and heal our world. These invariably involve studying our globe with new space-based tools and analyzing other planets to understand what can go wrong and right about planetary evolution. So the question becomes, how does a civilization get through its early stages to harmonize its technologies with the planet that gave it birth, becoming a ‘planetary intelligence’? And from the SETI perspective, how would we go about finding a civilization that had succeeded?

A Different Kind of Biosignature

We’re entering the era when space-based resources will be able to analyze the atmospheres of exoplanets, looking for the kind of imbalances that suggest constant replenishment in a life cycle of some kind. The same technologies allow us to look for what we can call ‘technosignatures,’ which are signs not just of life but of a civilization. One way to look at this is through terraforming, the adaptation of a planet to make it hospitable for living beings. Grinspoon believes that we will eventually be terraforming our own world, in the sense that we will acknowledge the need to engineer and reverse ecological damage and emissions.


Image: Can we detect not just biosignatures but signs of technological civilizations through analysis of an exoplanet’s atmosphere? Credit: IAU/L. Calçada

One thought is to look for signs of imbalance suggestive of technologies like ours, producing air pollution that can be measured by spectroscopic analysis. Because we don’t know what we may eventually stumble across, it makes sense to study the potential signatures of a planet in transition. I can point you, for example, to Henry Lin (Harvard), who in collaboration with Gonzalo Gonzalez Abad and Abraham Loeb has produced “Detecting industrial pollution in the atmospheres of earth-like exoplanets,” a paper published in the Astrophysical Journal Letters (Volume 792, Number 1 — preprint here).

The authors of the Lin paper are interested in anthropogenic pollution as a technosignature (though they don’t use the term), a marker of intelligent life and technology. It turns out that the James Webb Space Telescope will be capable of picking up atmospheric tetrafluoromethane and trichlorofluoromethane, which are the easiest to detect chlorofluorocarbons produced by industrial activities. But Lin et al. are talking about detections involving Earth-like planets transiting white dwarfs and levels of pollution ten times as strong as Earth’s.

Even so, this gets intriguing. One thought is that a civilization in a highly polluted environment is transitory — it is either going to solve its contamination problems or else go under, and this must occur in a tiny window on the scales of astronomical time. But perhaps there is another possibility, as the paper argues:

Coupled with the fact that the half-life of CF4 in the atmosphere is ∼ 50, 000 years, it is not inconceivable that an alien civilization which industrialized many millennia ago might have detectable levels of CF4. A more optimistic possibility is that the alien civilization is deliberately emitting molecules with high GWP [global warming potential] to terraform a planet on the outer edge of the habitable zone, or to keep their planet warm as the white dwarf slowly cools.

Now we’re hunting a terraforming signature, an environment being deliberately manipulated. David Grinspoon points to this kind of signature as a more enduring observable:

If we find an exoplanet with a strange climate that is being controlled by unexpected atmospheric compounds such as chlorofluorocarbons, that should get our attention. Or if we find a world with a suspiciously unusual pattern of albedo (reflectivity) or day/night pattern of brightness, we might suspect planetary engineering with mirrors or surface alteration. We should take notice if such a world seems to be in a climate state that preserves or extends an early evolutionary stage, stabilizing against the aging of its star.

Global engineering on a scale that would ward off, say, a runaway greenhouse should throw a signature; it’s our job to figure out what it would be, on the off chance that we someday see it. It’s clear enough, and Grinspoon makes the point repeatedly, that we can’t anticipate what advanced alien societies are going to do, so maybe the best approach is to be on the lookout for what we can call ‘unnatural’ planetary states that tip us to some kind of management. This theme — that we have to avoid being doctrinaire because we are bringing all too human judgments into matters that involve aliens, about whom we know nothing at all — is significant not just for analyzing our SETI observables but for extending SETI into other arenas.

Signaling to the Stars

There is a photo in Earth in Human Hands that shows author David Grinspoon standing with Alexander Zaitsev, who was chief scientist at the Russian Academy of Science’s Institute of Radio Engineering and Electronics, and whose name has become synonymous with broadcasting to the stars. Zaitsev has, in fact, been the driver behind several messages beamed from Earth as a deliberate attempt to raise the interest of any nearby civilizations. In 1999, the first Cosmic Call message was transmitted to four different stars, with a second Cosmic Call sent out in 2003 to five Sun-like stars between 30 and 45 light years away.

Long-time Centauri Dreams readers know that Dr. Zaitsev was a frequent contributor to the comments in these pages as the discussion over so-called METI (Messaging to Extraterrestrial Intelligence), also known as Active SETI, flared into life. And I do mean ‘flared’ — nothing polarizes people more than the question of whether or not we should deliberately brighten our radio signature with such targeted messages, given that we know absolutely nothing about what kind of alien civilizations may exist. It’s ‘shouting into the dark,’ at a time when we don’t have a clue what may be out there.

David Brin was also a frequent participant in those discussions, which often referred to the 1983 Brin paper “The Great Silence” and speculated on reasons why advanced civilizations might want to keep a low profile. While METI proponents argue that reaching out to announce our presence is a means of exploration, and one that is necessary because if all civilizations are listeners, there will be nothing to receive, the Brin contingent argues that inclusive international discussions are needed so that we make this decision by consensus.


Image: At the heart of the Messier 13 globular cluster in Hercules, toward which a simple pictorial message was sent from Arecibo in 1974. Credit: Credit: ESA/Hubble and NASA.

This is a serious debate with a history that I don’t have time to get into this morning other than to say that Grinspoon’s book presents the background. There is plenty to talk about — the development of guidelines for Earth broadcasts at Valencia in 2006, a strong editorial response in Nature, the resignation of Michael Michaud and John Billingham from an IAA SETI study group because of changes to the Second SETI Protocol, the AAAS session in San Jose in 2015 — and the often acrimonious debate continues to flourish.

Brin has often held up the ‘Asilomar process’ as a model. The reference is to the agreements within the DNA research community to work out voluntary guidelines for experiments and containment procedures, while banning particularly dangerous experiments involving hard to contain pathogens. The Asilomar guidelines became incorporated into laboratory practices as the field of biotechnology began its growth. It was a form of self-policing that effectively kept research alive while minimizing associated risks. Can we adapt such a process to METI?

METI is filled with arguments and counter-arguments, most of which have been rehearsed in these pages many times over. But I found Grinspoon’s take on the matter refreshing because he’s one of the few involved in the debate who have actually changed sides over time. Beginning with a position not so far from Alexander Zaitsev’s, that SETI demanded both a listening and a sending component, Grinspoon now says he is swayed by those who advocate caution and a moratorium on broadcasts until the matter can be fully assessed.

I’m taken with the fact that the author stresses how much we don’t know. It’s easy to use our human experience to generalize about what aliens might do, something that occurs all the time in discussions on METI. How likely is it that an alien culture would see us as a threat? How reasonable is it to assume that an advanced civilization will have given up war? Shouldn’t we expect a species more advanced than us scientifically to be morally advanced as well? Wouldn’t they, in fact, be inclined to help us elevate our own society to their level?

Grinspoon has been down this road, and he goes through these are other reasons why broadcasting to the stars could be beneficial. But the reasons simply aren’t enough:

Still, I must also admit that these are just my opinions, semi-informed at best. We absolutely can’t know any of this. Maybe it’s all wishful thinking. There certainly are logically valid arguments for the possibility of great dangers. So how do we proceed, if the risks seem absurdly low, but the cost of being wrong is everything we have, everything we love?

Which means that the author remains in favor of active SETI but only with appropriate precautions, and supports a voluntary moratorium. His thinking ties in with the long-term perspective — a millennial outlook — that informs his discussion of geoengineering. We have vast amounts to learn, in other words, about climate before we ever think of active terraforming, either here or somewhere else. Similarly, we need global buy-in to a project like METI that, to be successful, will doubtless also need to operate on long timeframes.

…I would submit that lack of self-knowledge is an existential risk. It may well be that the greatest value of METI will come not from anything we learn in response to a message we send, but from what we learn about ourselves in the process of attempting to reach some common ground and find our global voice. If we decide to send a message to possible extraterrestrials, we are also sending a message to our descendants. We are gifting them with possibilities of both benefit and harm. Such an endeavor requires us to form an alliance with future generations, to enter into a common project with them. That is clearly something we need to learn how to do. So, then, starting the conversation about whether to broadcast, the effort to have a globally inclusive process, becomes a worthwhile goal in itself.

Tomorrow I’ll wrap up this discussion of Earth in Human Hands with the question of sustainability in the context of space. Is a civilization that is working long-term in ways that are hard to spot by our SETI methods one that is invariably planet bound? The answer is no, and we’ll talk about this in terms of interstellar travel. Also in coming days, I want to look at Caleb Scharf’s thoughts on how alien life may prove indistinguishable from physics. More anon.


Comments on this entry are closed.

  • Coacervate November 22, 2016, 15:13

    If “they” can analyse our atmosphere then METI is moot. The message is already out there.

    • Matt November 22, 2016, 21:17

      If ET discovers us by analyzing our atmosphere, it might be polite to say hello before they actually arrive.

      Personally I would rather stay silent until we have some idea who or what we are talking to.

  • RobFlores November 22, 2016, 17:40

    I think truly advanced civilization have 5 options.

    1) Introspection (leave the care of the world and flee to the garden
    of VR) They would have pick unassailable places for their non-virtual
    self) at any rate Doctrinally Radio Silent.

    2) Active research. Infinite curiosity. Insatiable appetite for new
    discoveries. This does not mean Interference, just study of all species
    of the universe. Radio Silent.

    3) Interference and Prothelize about their path. Looks for ways to push lower species into so they develop into “entities like us”. Very careful
    engagement. No direct Radio communication.

    4) Other sentience is forbidden in doctrine. None can exist and their presense contradict/offend.
    Radio Silence as an offensive tactic

    5) Haphazzard changing policy on radio silence.
    How long is this going to our doctrine?

  • ljk November 22, 2016, 19:00

    Speaking of physical signs of extraterrestrial life:


    • Coacervate November 22, 2016, 22:32

      Is NASA afraid to “fail” after Viking missed? Or we misinterpreted the data (except Levin). I can’t understand why there wasn’t a follow up to Beagle 2 by now.

      • ljk November 23, 2016, 10:33

        The ambiguities of the Viking data did indeed make NASA gun shy about life on Mars: That is one reason why there wasn’t another Mars landing mission until almost two decades after Viking with the Mars Pathfinder/Sojourner expedition.

        They played it real safe with the MERs Spirit and Opportunity, having them just look for signs of past water, which they found plenty of. From the start there were also some very interesting indications of possible Martian fossils, but they were either dismissed or not addressed at all. Looks like it only took 12 years after they landed to finally get some serious research into the matter.

        When Mars Polar Lander arrived in 2008 and soon showed signs of liquid water droplets on its metal legs, it took NASA quite a while to acknowledge what any school kid could tell you just by looking at the images.

        So yes, NASA went in all gung-ho for life on Mars, at least the microbial kind, back with Viking and its amazingly compact $60 million biolab, without fully understanding what the planet’s surface was composed of. But they were so bent on finding life that when the results came in unclear, many almost declared Viking a failure, which was a mistake on so many levels. Curiosity was originally declared to be searching for life, but NASA pared back that description as well.

        Hopefully someone else will be brave enough to find out what’s really going on at the Red Planet. After centuries of rampant speculation about Martians up and down the scale, we deserve a final answer one way or the other and not coy political words.

        • ljk November 23, 2016, 12:32

          Not far from Viking 2’s landing site in Utopia Planitia, a lot of water ice has been found under the planet’s surface:


          • ljk December 14, 2016, 15:02

            December 13, 2016 12:19 PM ET

            Curiosity Finds Mars May Be Covered in Organic Materials

            More study is needed to determine where the organics came from and how they managed to survive in the Red Planet’s harsh environment.

            BY IRENE KLOTZ

            New analysis from NASA’s Mars Curiosity rover shows that the red planet is likely flush with organics.

            “I am convinced that organics are all over Mars,” said Jennifer Eigenbrode, a biogeochemist and geologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

            “They’re all over the surface and they’re probably through the rock record. What that means is something we’ll have to talk about,” Eigenbrode said last week during a National Academy of Sciences workshop about the search for life beyond Earth.

            Scientists on Tuesday will present additional findings from Curiosity, which four years ago landed on Mars, the planet most like Earth in the solar system, to explore a mountain of sediments rising from the center of a 96-mile wide impact crater.

            The rover quickly accomplished the primary goal of its mission, which was to determine if Mars ever had the chemical ingredients and suitable environments to support microbial life.

            Full article here:


            To quote:

            A key part of the search focused on organics, a quest that has led to the surprising discovery that organic matter may be widely distributed on Mars.

            “To me this is the biggest take-home message. Four years ago, we would never have said this,” Eigenbrode said.

            Scientists don’t know the source of the organics, nor how the material has managed to survive in the harsh radioactive environment on Mars. It was found in samples drilled out from rocks and chemically analyzed.

            Whether biological or geologic in origin, a rich supply of organics has implications not only in the search for past life, but also in supporting future endeavors, such as farming.

            “That organic matter could be really important,” Eigenbrode said. “The door is really open here to an expanded habitability potential.”

            In related research, California Institute of Technology geologist John Grotzinger, said Curiosity, which has been slowly making its way up Mount Sharp, has found multiple examples of primary igneous minerals being altered.

            “What this is telling us is that that sedimentary basin is a chemical reactor, that those primary igneous minerals are being converted under different chemical circumstances into different minerals,” Grotzinger said during the National Academy of Sciences workshop. “We’re not sure what all this means, but it’s pretty exciting for habitability.”

            The Curiosity team also has made progress on locating potential types of rocks that could preserve evidence of past life. The most promising find, according to Grotzinger, has been a silica-rich rock which is chemically similar to early rocks on Earth that have been found to contain fossil cells.

            “Silica is the great material on Earth that survives everything,” Grotzinger said. “If you have it precipitate early on, it is capable of preserving the things you’re most interested in and apparently Mars is making this stuff.”

            • ljk December 14, 2016, 17:59

              We’re Searching For Life on Mars All Wrong

              James Grebey

              December 14, 2016

              Experts agree that Mars was habitable at one point in history. The thing is, searching for habitable environments is a far cry from actually searching for signs of past or present life. To do that, a scientist at SETI explains, we need to get much more specific and look for actual habitats.

              According to Nathalie Cabrol, a senior research scientist and director of the Carl Sagan Center, our current level of observation and astrobiological focus is only geared towards broad questions of potential habitability. That’s not good enough.

              In a marquee lecture at the American Geophysical Union in San Francisco on Wednesday, Cabrol explained how we need to take a more subtle, gradual view of the way the planet changed over time, rather than just categorizing them into three geological periods — the Noachian, Hesperian, and Amazonian periods.

              “It’s a gross caricature of what happened,” Cabrol said. “You don’t understand how one went to the next.”

              Full article here:


              Cabrol explained that looking at Earth can be helpful, so long as we don’t get too much of our terrestrial norms. “We’re seeking guidance, not truth,” she said. Different areas in and around the Andes mountains, including the Atacama desert and Altiplano, can be used as decent stand-ins for Mars over time, a technique Cabrol called “space for time substitution.” By observing how lakes deal with high levels of radiation, evaporation, and geological change, it colors how scientists need to look for Martian habitats on the micro level.

              “We need to think about habitat fragmentation when we are looking for life on Mars,” she explained, noting that all these lakes likely divided into basins as they dried up over the ages. For the best chance of finding signs of life, scientists need to find “the last oasis that will last the longest.”

              “We are just seeing tipping points, we are not seeing what happens on the subtle transitional level,” she said.


              “We need to adopt the tool to the exploration, not the exploration to the tools,” she said, adding that explorers need to have specific places of interest identified years in advance before they land for a more thorough examination.

              [Her comment above could equally apply to the history of SETI, which has done a lot more focus on the tools than the kinds of beings that may exist beyond Earth.]

    • Securis November 26, 2016, 8:03

      Let us assume those are actual signs of extraterrestrials life. Wouldn’t that be “by far the worst news ever printed on a newspaper cover” as Nick Bostrom put it since it would mean the Great Filter is ahead of us?

      • ljk November 28, 2016, 10:21

        If one buys into the Great Pumpkin – I mean Filter.

        Just as we like to assume that aliens will not contact us until we are “ready” (think the Prime Directive ala Star Trek), or that ETI will either be altruistic scientists explorers or marauding conquerors, I would prefer to see the discovery of ETI as a positive sign for humanity. Finding alien microbes, even fossils, would also be of major benefit to science over any fears.

        We worry about alien contact because of the history of life on this planet. However it is one thing to have to deal with creatures who live in proximity on the same world and yet quite another to deal with beings many light years away, or even interplanetary distances in the event we find native organisms in our Sol system.

        Again, they could be threats, but I think it is time to look at other possibilities since the aliens as conquerors theme has been done so many times over already. I think it actually clouds the other possibilities and does not treat alien minds as being actually alien, just versions of ourselves. I also have similar issues with ETI being our direct saviors as well. I think it may actually be somewhere in between the two extremes, as existence often is.

        • Alex Tolley November 28, 2016, 13:05

          Our depiction of aliens is mostly projection. They are unlikely to be as we currently think of them, neither savior or enemy, but something else entirely. Stanislaw Lem’s stories are more apropos, as well as Fred Hoyle’s “Black Cloud”., to name just two authors.

  • Douglas Dwyer November 22, 2016, 19:17

    We can be judged by what we discard hardware from our space station or emissions from our planet.
    Incidently what was the value of the energy used to place all of it in orbit.
    if standardised parts were used they could have been ressembled in orbit as something else .

    • ljk November 28, 2016, 10:24

      The items that are discarded from the International Space Station (ISS) end up burning up in Earth’s atmosphere, so you may want a different example. Besides, it makes for an efficient way to get rid of the station’s trash, which would overwhelm the facility if left aboard.

      • Douglas Dwyer November 28, 2016, 13:06

        Items burnt up in the atmosplere are a double waste,
        A carefully designed throw away could be fitted to its companions to build a useful item already in orbit
        Putting unnecessary items in orbit is a catastophic wste of energy if there is an alterative, mining such waste would be more efficient than mining asteroids.

        • ljk November 28, 2016, 13:59

          In the case of the ISS I am talking pure trash here, items that cannot be reused. It is not like the station is a manufacturing facility and they are dumping scrap metal overboard.

  • Alex Tolley November 22, 2016, 22:01

    As has been argued in other threads, any ETIs are likely to be millions of years ahead of us unless their civs have short life spans. If they are technologically advanced, they probably have very sophisticated instruments to monitor the cosmos. Staying silent is probably as useless a strategy as an animal staying still and silent to avoid human predators. Coacervate makes that point with a technology that is close to our level of development.

    At this point, we can just hope that light is a fundamental, unbreakable speed limit, making interstellar journeys time consuming. However, that doesn’t mean they won’t be undertaken, and we know that theoretically, von Neumann replicators can fill the galaxy within a million years, so nearby monitoring devices could already be present, as well as with capabilities that could harm us too.

    The precautionary principle sounds very smart, but the Asilomar Declaration was based on the knowledge that DNA technologies were being developed and that there were people and nations who could and would use them. We have no knowledge that ETI is out there, nor what their intentions are even if they are. Their capabilities are likely to be far more advanced than ours. So warning about shouting “yahoo in the jungle” as Dr. Brin likes to say, isn’t all that logical to me, even though I understand where the concern lies. In prcatice, the research needed before we can do METI might take a millennium, by which time we will be [hopefully] out in the solar system, have sent out swarms of interstellar probes many of which will have reported back on their target star systems, and just maybe already on our way out to the stars by some means and in some form.

  • Dmitry Novoseltsev November 22, 2016, 23:31

    Not only radio, optical METI at the speed of light. Possible low-speed “hard” METI to deep future also.
    This minimizes the risks of receiving messages unfriendly recipients.
    Also necessary to search for such artifacts.

  • Steve Muise November 23, 2016, 12:29

    Interestingly enough, if we could get the resolution high enough to detect changes in the percentage of these chemicals in the atmosphere of the exoplanet we could determine changes in their industrial technology…or, for that matter, if the levels didn’t change at all, whether or not they had gone extinct.

  • Bob Steinke November 23, 2016, 12:47

    “The kind of voice recognition and rudimentary intelligence built into my Google Pixel hides its complexities in a small package. I speak into the air and tap the resources of computer clusters that are located who knows where.”

    Yeah, but those computer clusters are still out there consuming gobs of power. Just because the user interface gets more unobtrusive doesn’t mean that the system as a whole becomes less power hungry.

  • DJ Kaplan November 23, 2016, 13:24

    If we are looking for signs of spacefaring civilizations, we can assume that in order to get any significant distance in space, you’ve got to dump lots of energy in the opposite direction. Would there be a shower of gamma rays in the opposite direction of Zog’s ship? What would that look like from Earth?

  • Robert November 23, 2016, 18:13

    Kardashev Type 0.7 ? More like Kardashian Type 1.0. Any truly intelligent species would stay away. :)

  • Avi Loeb November 23, 2016, 20:34


    Just a brief note to let you know that Henry Lin is a Harvard undergraduate student to whom I assigned my idea of calculating the signature of industrial pollution in planetary atmosphere. I usually let my students be first authors on collaborative papers, but it is not accurate to describe the authors on the paper as “Lin’s team at Harvard”.

    With kind regards,
    Avi Loeb

    • Paul Gilster November 23, 2016, 22:44

      Sorry for that, Dr. Loeb, and thank you for pointing out the error. I’ve corrected the text.

  • Ivan Vuletich November 23, 2016, 21:00

    Talk of atmospheric technosignatures puts me in mind of the 1970’s Niven & Pournelle novel “The Mote in God’s Eye”. In the book, the Motie home planet had excess helium in its atmosphere due to long term use of fusion power.

    Could excess helium in the atmosphere of an Earth-like planet be detected? Is there any natural mechanism that could produce a helium excess?

    • Mark Zambelli December 5, 2016, 13:25

      As to He4 detection, I’m not sure the JWST would be up to the task. But He would be transitory in any Earthlike planets atmosphere as 1 G isn’t enough to hold onto it and it escapes to space (thankfully or Earth may’ve become a gas giant). There’s the rub for our own predicament… He4 is a mined-resource (it comes from underground caverns when alpha particles get trapped in rock, pick up electrons, drift along cracks and fissures and collect in large quantities) and once we fill our party balloons with it, rather than run our physics/medical equipment, we can say goodbye to the stuff. Can’t imagine any natural process that would create an excess, it’s a noble gas after all.

  • Joe November 24, 2016, 0:36

    The idea to pursue METI after a “globally inclusive process” sounds nice, but it’s superficial. What we in the West call “inclusive” really means scientists and political leaders in North America, Europe, Russia, China, Japan and a few other first world nations. None of the 450 million subsistence farmers in India are going to be consulted. Same for sub-Saharan Africa. Nobody in America’s urban slums or Appalachian hollows are going to be consulted either. Let’s hope the Vatican isn’t asked their opinion. (The latest issue of “Vanity Fair” magazine has an article about how priests are still doing exorcisms in 2016.) Instead this is going to be an elitist decision, although there’s nothing really wrong with that. Most important decisions in history have been made by elitists. I’m just pointing out that “inclusive” is a relative term, and in the case of METI, the decision makers representing 7.4 billion humans will all fit into a mid size auditorium.

  • Emre November 24, 2016, 7:41

    The reason aliens stay silent (as should we) is because civilisation maturity models predict that.

    As a civilization, we are much more forward thinking, patient, reserved than we were in 1492, than we were in 480AD, than we were in 1250BC.

    As civilizations mature they start to act like adults instead of children.

    The truth is that, for all of us, human and alien alike, this is a Universe of entropy. Everything naturally goes from a higher to a lower energy state before it loses its energy to the environment and dissipates.

    Of the trillions of potential civilizations out there, a very high percentage are likely to want to use (destroy) whatever they come across in the Universe to increase/conserve their energy state rather than hold hands with it and die together.

    Mature alien civilizations know this and stay silent.

    Would you voluntarily take part in an arbitrary action where the chance of your death is 10%? No.

    What if it was 99.999%?

    • Michael November 25, 2016, 17:42

      ‘Would you voluntarily take part in an arbitrary action where the chance of your death is 10%? No.

      What if it was 99.999%?’

      Depends on the reward, and of course ones predisposition to the game of chance…now to immortality what percentage would you or I chance?

    • ljk November 28, 2016, 10:28

      Or their silence simply means that we have nothing they would want. Or that we just aren’t very noticeable yet on a galactic scale of 400 billion star systems 100,000 light years across and our electromagnetic transmissions have barely spread 200 light years, most of them quite weak.

      • ljk November 28, 2016, 11:25

        Or that when one is studying a less advanced species, it only makes sense to remain quiet and out of sight so as not to disrupt the specimens in their natural habitats and thus skew the data.

      • Alex Tolley November 28, 2016, 13:48

        Or they are simply not there. We may be the only extant technological species in the galaxy. Possibly even the first.

        • ljk November 29, 2016, 14:36

          Either way, it’s a mighty soberin’ thought, quoting Pogo.

          • Alex Tolley November 29, 2016, 19:09

            Clarke made a similar comment.

    • Alex Tolley November 29, 2016, 19:14

      Of the trillions of potential civilizations out there, a very high percentage are likely to want to use (destroy) whatever they come across in the Universe to increase/conserve their energy state rather than hold hands with it and die together.

      OTOH, joining other civs might offer better ways to conserve energy and extend it with technology.

      If there are no other civs, then we are just being afraid of non-existant bogeymen in te dark. If there other civs and some are predators and some prey, it makes sense to make alliances to better resist the predators, just as humans have done for eons.

      So I call your argument into question.

  • Douglas Dwyer November 26, 2016, 12:15

    The technosignature may be an absorbtion line thats missing.
    Similarly radio frequency noise that is replaced by a deeply coded pseudo noise spectrum.

  • ljk December 14, 2016, 15:08

    Find Cosmic-Blast Shields, Find the Aliens

    Astronomers say they could detect signs of advanced civilizations by searching for their defense mechanisms.

    Marina Koren

    December 14, 2016, 4:55 AM ET

    For decades, the search for intelligent extraterrestrial life has used giant radio telescopes on the ground to scan the skies, hoping to detect alien broadcasts from somewhere in the Milky Way. (No luck so far.) But the rise of powerful space telescopes capable of observing hundreds of Earth-like planets orbiting distant stars, like the Kepler telescope launched in 2009, changed the game. The right technology, astronomers say, could someday allow humans to see optical evidence of extraterrestrial life.

    So, what can astronomers look for? The most popular suggestions are structures built by civilizations, far more advanced than our own. In 1960, Freeman Dyson hypothesized spheres or swarms constructed to harness and harvest the energy of a parent star. In 2005, Luc Arnold proposed artificial objects inserted into a planet’s orbit to serve as a signal of existence to other civilizations. Now, a pair of astronomers suggest looking for shields constructed to protect against deadly cosmic explosions.

    Milan Cirkovic and Branislav Vukotic suggest, in a report published this month in the journal Acta Astronautica, that advanced civilizations could lasso objects within their solar system to engineer shields that would dampen the dangerous effects of exploding stars or gamma-ray bursts. After all, no one wants to be wiped out by a supernova—and a sophisticated, space-faring society with enough technological prowess could actually do something to protect itself. Back on Earth, telescopes like Kepler could spot these shields as they transit their stars, creating the dimming effect the spacecraft is built to observe. Powerful infrared telescopes could also detect the shields by the heat they emit.

    “We should certainly look for these, as well as all conceivable forms of astro-engineering within the SETI framework,” Cirkovic wrote in an email, referring to the search of extraterrestrial intelligence by its acronym. “The orthodox SETI is narrowly conceived and unlikely to succeed as long as it relies on intentional radio emissions.”

    Full article here:


    The report online here:


  • ljk December 16, 2016, 16:59

    Astronomers observe mysterious dimming of a young nearby star

    December 16, 2016

    by Tomasz Nowakowski

    (Phys.org)—Astronomers have spotted transient, transit-like dimming events of a young star named RIK-210 located some 472 light years away in the Upper Scorpius OB association. However, what puzzles the scientists is the mystery behind this dimming as it can not be caused by an eclipsing stellar or brown dwarf companion. They describe their search for plausible explanations in a paper published Dec. 12 on the arXiv pre-print server.


    RIK-210 is around five to 10 million years old, about half as massive as the sun and has a radius of approximately 1.24 solar radii. The star has been recently observed by NASA’s prolonged Kepler mission, known as K2, during its Campaign 2, lasting from Aug. 22 to Nov. 11, 2014. A team of researchers led by Trevor David of the California Institute of Technology (Caltech) has analyzed the data provided by K2.

    “We find transient, transit-like dimming events within the K2 time series photometry of the young star RIK-210 in the Upper Scorpius OB association. These dimming events are variable in depth, duration, and morphology,” the scientists wrote in the paper.

    Full article here:


    To quote:

    The team found that these dimming events occur approximately every 5.67 days, in phase with the stellar rotation, noting that they are deep (sometimes greater than 15 percent) and short in duration relative to the rotational period. Moreover, the morphology of the dimmings is variable throughout the whole observational campaign, while the starspot modulation pattern remains stable over this period of time.

    While such variable dimmings have been documented around mature stars and stellar remnants, it has not been previously observed around a young star lacking a protoplanetary disk, as in the case of RIK-210.

    In the search for possible explanations of the observed transient, transit-like dimming events, the researchers at first excluded the possibility that they can be caused by an eclipsing stellar or brown dwarf companion. This hypothesis was ruled out as it is inconsistent with radial velocity measurements as well as with archival and follow-up photometry data.