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Eternal Monuments Among the Stars

Yesterday’s post looked at SETI and its assumptions, using the lens of a new paper on how the discipline might be enlarged. The paper’s authors, Robert Bradbury, Milan Ćirković and George Dvorsky, are not looking to supplant older SETI methods, but rather to broaden their scope by bringing into play what we are learning about astrobiology and artificial intelligence. It is perilous, obviously, to speculate on how an alien civilization might behave, yet to some extent we’re forced to do it in choosing SETI targets, and that being the case, why not add into the mix methods that go beyond our current radio and optical searches, methods that may have a better chance of success?

The Engima of Contact

A key to extending SETI’s reach is to question the very idea of contact. One assumption many of SETI’s pioneers had in common was that there was an inherent need to communicate with other species, and that this need would take the form of intentional radio beacons or optical messages. What Bradbury, Ćirković and Dvorsky are calling ‘Dysonian SETI’ makes no such assumption, and actually gains strength from the fact that it does not. Acknowledging that we have not yet found an undisputed detection signature, Dysonian SETI says that intention is not necessary. A civilization may be detectable through its artifacts. A Dyson sphere, for example, should show an infrared signature that is distinguishable from the normal spectra of stars.

Once in place, a Dyson shell should be durable enough to potentially outlive its creators, ‘Ingrafted in eternal monuments/Of Glory,’ to cite the verses from Lucretius the authors use to illustrate their point. Thus we get around a significant problem noted by many SETI writers — the ‘window of opportunity’ for radio SETI is short, a mere flicker in the span of our own civilization, much less the span of our planet’s existence. Even if you posit a stunningly optimistic figure of 106 technologically advanced civilizations in the galaxy, it is clear that these cultures will exist at different levels of development. What are the odds that two will be at precisely that stage of technical evolution to enable back and forth radio communications?

Image: NGC 6744, a spiral galaxy some 30 million light-years away in the southern constellation of Pavo (The Peacock), as captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope. If tens of thousands of civilizations co-exist in such a galaxy, how many will be close enough to each other in terms of technological development to make radio or optical contact likely? Credit: ESO.

Dysonian SETI would surmount this problem because enormous astro-engineering projects could exist as archaeological survivals no matter what the fate of their parent civilization. The idea seems plausible and does not foreclose the ongoing SETI effort in radio and optical wavelengths. But the authors point out that our assumptions about artifacts themselves also need to be adjusted. If civilizations move toward a ‘singularity’ in which artificial intelligence leads to a kind of postbiological evolution, then searching for Dyson spheres takes a twist.

Why? Because so far we have assumed a Dyson shell roughly the size of Earth’s orbit, one with a working temperature that would sustain our kind of biological life on the surface of the shell. These parameters hardly fit the needs of postbiological intelligence. From the paper:

…from a postbiological perspective, this looks to be quite wasteful, since computers operating at room temperature (or somewhat lower) are limited by a higher kT ln 2 Brillouin limit, compared to those in contact with heat reservoir on lower temperature T

I think what the authors are referring to above is also called the Landauer limit, which defines the minimum amount of energy needed to alter one bit of information — here k is the Boltzmann constant while T is the temperature of the circuit (K) and ln 2 is the natural log of 2. In any case, cooler is better. The paper continues:

Although it is not realistic to expect that efficiency can be increased by cooling to the cosmological limit of 3 K in the realistic model of the Galaxy, still it is considerable difference in practical observational terms whether one expects a Dyson shell to be close to a blackbody at 50 K, as contrasted to a blackbody at 300 K. This lowering of the external shell temperature is also in agreement with the study of Badescu and Cathcart… on the efficiency of extracting work from the stellar radiation energy. In this sense, the Dysonian approach needs to be even more radical than the published intuitions of Dyson himself.

Beyond the Dyson Shell

Widening the theoretical background of ongoing searches (the authors point to SETI@Home as one example of widely distributed processing) means taking such new perspectives into consideration, and the paper goes on to flag other possible signatures of an extraterrestrial civilization:

  • Unusual chemical signatures in stellar spectra, which could indicate a technological culture trying to be noticed by distant astronomers
  • Gamma-ray signatures created by antimatter burning in the activities of an extraterrestrial civilization
  • Recognizable transits of large artificial objects
  • Analysis of extragalactic astronomical data, which could reveal the presence of large-scale structures and Kardashev Type III astro-engineering

Interestingly enough, all of the above have been the subject of initial studies, and the bibliography of the paper (see yesterday’s citation) is laden with these and other references. These investigations have been regarded as little more than curiosities, but the impact of the discovery of clearly artificial objects would have such a quickening effect on human self-awareness that they are clearly worth the limited funds thus far spent on them.

Widening the Search Space

A Dysonian SETI would evolve along the lines suggested by Freeman Dyson himself when discussing the supposed willingness of alien civilizations to communicate with each other, and their implied benevolence when it comes to greeting new members to the ‘galactic club.’ Dyson would have none of it, saying “…I do not wish to presume any spirit of benevolence or community of interest among alien societies.” Why indeed do so, when a search for Dysonian artifacts like Dyson shells would make no such assumptions, while allowing us to bring to bear what we are learning about nanotechnology, artificial intelligence and astrobiology?

Why not widen the search space, then, adding to the already impressive and groundbreaking work of SETI’s pioneers by bringing into play recent findings like those of Charles Lineweaver, whose work shows that Earth-like planets in the habitable zone of the galaxy (itself a relatively new concept) are on average 1.8 billion years older than our planet? Assume civilizations not just millions but potentially a billion or more years older than our own and you play down the importance of contact (it is hard to imagine the advantages of such to the alien culture) but leave open the prospect of discovering the works they have built and possibly left behind.

Let me close with another quote from this vigorous paper re SETI old and new:

…the two approaches are at present compatible and should be pursued in parallel at least until there is better theoretical insight into the preconditions for emergence of technological civilizations in the Galaxy. The ability to extract information from the interstellar environment increases dramatically with each passing year. As the resolution of the data increases, so does the ability to process and infer its nature. This process will deeply challenge conceptions of the Universe and what we think we know about it. It will also challenge the way in which we see ourselves and our potential as an intelligent civilization.

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Comments on this entry are closed.

  • James D. Stilwell January 24, 2012, 14:34

    WHAT LAW SAYS ALIEN LIFE FORMS HAVE TO LIVE IN ARTIFICAL STRUCTURES. WOULD NOT SPACE ITSELF AND A STAR BE ENOUGH FOR A MILLION YEAR OLD RACE?
    LEAVE THE BIOLOGY OF FLESH ALONE FOR A DAY. J D STILWELL

  • Dirk Bruere January 24, 2012, 14:46

    If the FTL neutrino results hold up, the current SETI projects looking for radio communications becomes close to pointless. It would be a strong indicator that there may well be far better communication mechanisms than light speed limited ones

  • Nick January 24, 2012, 15:52

    “computers operating at room temperature (or somewhat lower) are limited by a higher kT ln 2 Brillouin limit, compared to those in contact with heat reservoir on lower temperature T…it is considerable difference in practical observational terms whether one expects a Dyson shell to be close to a blackbody at 50 K, as contrasted to a blackbody at 300 K. ”

    This is an interesting insight. It’s also interesting to compare this to the range of Carrigan’s Dyson surface search, which as Doug M. reported in the last thread ranged from 80K to several hundred K.

    However there is an opposite imperative: hotter radiators are far more efficient than colder ones. Indeed the efficiency increases with the fourth power of the temperature difference between the radiator and the typical 3K background to which it will usually be pointing. So a radiator at 200K can dump about 16 times more heat per square meter than a radiator at 100K. Unless computational efficiency improves even faster than the inverse fourth power of temperature, hotter Dyson spheres will probably be better. (This physics of radiators is also important to starship design, per a previous thread).

    It wouldn’t hurt to expand the search in both hotter and colder directions.

  • Adam January 24, 2012, 16:37

    Nick makes a good point if areal/mass efficiency were the issue, but a Dyson shell is radiating the waste heat of a spherically enclosed habitat and thus can’t be hotter than the habitat within from basic thermodynamic considerations. Paul’s point – derived from the work of Bradbury and Cirkovic on so-called Matrioshka Brains and the like – is that all the useful work extracted from a star’s output would require a very much larger radiating area for a much lower radiating temperature, closer to the equilibrium temperature of the larger Galaxy.

    James Stilwell’s point implies a willingness to let stellar output go to waste, spilling out undammed to try to raise the temperature of the CMB. While such profligacy might appeal for a time, as the numbers of the space adapted grow, so will their collective energy requirements, eventually blocking a significant fraction of a star’s light.

  • Alex Tolley January 24, 2012, 17:40

    One idea about the lack of contact is that civilizations stay quiet and hidden to avoid predatory ones. In which case, there would be no artifacts to draw attention to them. Would the predator civilizations leave artifacts, or would they also be hidden, much like predators and prey of terrestrial biology?

    Certainly it may be worth looking, if only to rule out this line of thinking. But I can’t help thinking that we might not recognize signs of a very advanced civilizations if it was staring us in the face.

  • Nick January 24, 2012, 17:58

    So Adam, are you (or those you cite) claiming that the energy efficiency of computation increases faster than the inverse fourth power of temperature? If not, then the habitat would not “require” a lower radiating temperature at all — it would rather benefit from a higher one. The drawbacks of running the computer at a higher temperatures would be outweighed by the benefits of running the radiator at higher temperatures.

    Perhaps such an extreme improvement of computation at lower temperatures is possible, but I’d like to see the argument.

  • Nick January 24, 2012, 18:53

    Alex Tolley: “civilizations stay quiet and hidden to avoid predatory ones.”

    The dominant organization in a galaxy doesn’t need to hide from anybody. Furthermore, wars are at least as likely to produce very high energy, very visible outputs as stealthy ones. If this occurs in even a few out of the hundreds of billions of known galaxies, we will likely soon see it.

    Struggle produces competing imperatives. Plants would love to hide from herbivores, but they can’t, because they have an even more important need for sunlight, and thus pursue the Malthus/Darwin imperative of capturing as much sunlight as they can. As a result our planet produces very distinctive and large-scale emission and reflection spectra. An advanced civilization will similarly need large surfaces to capture and radiate energy, following the Malthus/Darwin imperative to use as much power as possible, and many of them will also benefit from illuminating these surfaces in order to work or play around them or to try to capture each others’ attention. (BTW, an argument along these lines was Dyson’s original argument for the Dyson sphere — it’s about universal physical constraints and likely widespread motivations of life, especially the Malthus/Darwin imperative, not about the design of particular structures, which would likely be far more advanced than we can imagine).

    Similar effects can be seen in human wars, with competing imperatives for both highly energetic (and thus necessarily highly visible) and stealthy modes of combat. Furthermore war stealth competes with peaceful imperatives (e.g. advertising, which motivates radio stations that enemies can use as beacons). It’s quite implausible that stealth is a universal imperative that always trumps motivations to act in highly visible ways, just as it’s implausible that we haven’t found those dwarves in the mines yet because they are all so always shy.

    (Shyness and skill at hiding seem to be universal traits of mythological creatures. Paging Karl Popper!)

  • Rob Henry January 24, 2012, 19:06

    Alex Tolley, it has been pointed out many times before on these pages that hiding as a general strategy make no sense. That leaves hiding as a specific strategy in the case of Sol. Perhaps we are in a forbidden zone, or perhaps our home world resembles the typical haunt of a particularly nasty type of ETI in our galaxy, or perhaps they are afraid of our type but are yet to decide among themselves who gets the job of pest extermination.

  • andy January 24, 2012, 19:29

    I don’t find Dyson spheres particularly plausible, either from considerations of constructions or of maintenance. I suspect they’d be very vulnerable to Kessler syndrome. Of course this latter process might also be detectable at long range, but the possibility of the Dyson sphere collapsing in such a fashion may cause builders to think twice before embarking on such a huge engineering project.

  • Khan January 24, 2012, 19:33

    I’m certain this has been mentioned in the past discussions of science fiction — but Accelerando by Charles Stross is the most believable singularity/astro-engineering scenario I’ve ever read, and has several concepts useful to this discussion…

    Post-singularity civilizations are posited to extract all power from their star via nested Dyson swarms (Matrioshka brains, as Adam mentioned), using the harvested power to run massive computations — either for simulated reality, or for vast post-human intelligences.

    Extend that thought, and you also get a neat solution to the Fermi Paradox: advanced civilizations would think and evolve so fast, light-speed communication with other stars would be even less relevant than paleontology. Worse, physically leaving the home system would require taking your brain with you — but if your brain had the mass of a small planet, you’d likely drop the idea.

  • Dirk Bruere January 24, 2012, 20:31

    A Dyson sphere around a black hole makes more sense.
    It’s smaller and a black hole can convert mass to energy more efficiently than a star. Additionally there might be the possibility of using a BH for hypercomputation

  • Brett Bellmore January 24, 2012, 21:50

    “but a Dyson shell is radiating the waste heat of a spherically enclosed habitat and thus can’t be hotter than the habitat within from basic thermodynamic considerations.”

    This assumes that the habitat IS inside the Dyson shell. It strikes me that, for power conversion reasons, you want a small shell at high temperature, (Insulation on the inside of the shell will cause the stellar surface to rise in temperature with no practical limit; If materials permitted, the shell could be sized to emit radiation at the normal temperature of a star, and still have access to high enough temperatures to run at high Carnot efficiency.) while you want your habitat to be far from the star, and dispersed, so as to avoid their radiators heating each other, and allow passive radiation at low temperature.

    So you get a small Dyson shell sending power beams to a cloud of habitats dispersed at great distance, all radiating at tens of Kelvins, not hundreds.

    You’re looking for clouds radiating at efficient temperatures for computation, not life, centered around oddly cool, large stars. And leakage from efficient power transmission beams.

  • Eniac January 24, 2012, 22:23

    Extend that thought, and you also get a neat solution to the Fermi Paradox: advanced civilizations would think and evolve so fast, light-speed communication with other stars would be even less relevant than paleontology.

    Paleontology is found plenty interesting by many. If our Deep Thought descendants have any curiosity about the real world left, they will send out probes to all corners of the universe, even if the benefits are far in the future. Fresh data from never before observed places should be among the most precious commodities for such beings. Of course, I could be wrong and they’ll be content doing their version of TV or facebook 100% of the time.

  • Eniac January 24, 2012, 22:36

    All the discussion about war, predator/prey, off-limits areas etc. ignores the simple fact that light speed limitations will make interstellar coordination extremely difficult. Law or treaty enforcement are pretty much moot. No interstellar government, nor war. There will be no galaxy wide threats, no ferocious predator race waiting to pounce 50 light years at a the source of an ill-conceived beacon…. Just a large number of inhabited systems, their number growing inexorably through colonization events (nearest star hops, all). Strife and politics will be confined locally on those systems.

  • Alex Tolley January 24, 2012, 23:51

    @Nick The dominant organization in a galaxy doesn’t need to hide from anybody. Furthermore, wars are at least as likely to produce very high energy, very visible outputs as stealthy ones. If this occurs in even a few out of the hundreds of billions of known galaxies, we will likely soon see it.

    And that logic leads you right slap bang into the Fermi paradox. Which leads to discussions about whay we aren’t seeing what should logically be, so we invent ever more ideas to explain why civilizations are “hiding in plain sight”.

  • Dave Moore January 25, 2012, 0:16

    Commenting on this and the previous post Paul made, I would say that too much attention is being paid to Dyson Spheres. Physically, they are extremely difficult to construct and they are unstable. Even Freeman Dyson didn’t really believe in them. He was using them more as a metaphorical point. Civilizations build themselves up step by step, so something like a Dyson swarm is far more likely. An advanced civilization may occupy a swarm of warm bodies in the inner system, or take advantage of the thermodynamic efficiencies of the cometary belt, but it is unlikely to manifest itself as an actual glowing IR sphere.

    Another assumption underlying the Dyson Sphere is that you want to capture your civilization’s energy from your central star. Star’s are rather inefficient devices for fusing Hydrogen to produce energy. It may be a lot easier and more efficient to fuse your own Hydrogen, and there is plenty of Hydrogen available in any system with giant planets.

    The underlying weakness of looking for Dyson Spheres is that you are looking for just one type of artifact, and a fairly improbable one at that.

    Because we cannot be sure how an advanced energy intensive civilization would manifest itself, I would just assume it is going to radiate waste heat. Looking for older stars with an IR excess for their spectral type or planetary rings would be a good starting point. Planetary rings and an IR excess are considered signs of planetary system formation and youth, and while there are some natural explanations for such things in older systems, it is abnormal.

    The big problem for detecting exosolar technological civilizations maybe that their power consumption per star system could be only a small fraction’s of their star’s, thereby making them difficult to detect, particularly if we are doing extragalactic searches.

  • Gregory Benford January 25, 2012, 0:59

    I like these ideas, but the discussion passes over the troubles of detecting Dyson structures, whether 50 K or 300K: infrared spectra tell you little unless you have a model (as we do for stars). Maybe such objects show silicon and iron lines, but…it will be hard to distinguish them. The WISE satellite found innumerable IR sources and only a good stellar model for the M and lower mass stars allows them to distinguish stars from the many IR molecular clouds etc. Indeed, the 50 K Dysonian sources will be hard to tell from molecular clouds.
    In our economic SETI analysis we referred to all signals from extinct yet still robotically radiating sources as Ozymandias signals. In this sense Dyson structures testify to their builders, though passively.

  • Interstellar Bill January 25, 2012, 2:04

    I say again to not forget launch lasers or masers in the signature list.

    I also reiterate that subluminous galaxies should be scrutinized:
    after all, don’t we expect a Type III civilization to be sucking up starlight?

    We should also expect that a Type III would have accelerated local star formation until all its galaxy’s gas and dust was made into stars.
    Aren’t subluminous galaxies mostly dust-free?

    As for hiding, if you’re a Type II around a large star you already have more population and energy than anyone for hundreds of light years, so you have nothing to fear and no reason to hide, as if you could hide a trillion habitats anyway.

  • henk January 25, 2012, 8:41

    there are no other civilizations in this galaxie. We are the only one. That is almost a fact. I think that 1 of the 10 million spiral galaxies have maybe 1 advanced civilization. I think complex life is very common, but intelligent life is extremely rare. I maybe even go as far that we are the only one.

  • Andy January 25, 2012, 9:51

    Regarding Fermi paradox and the lack of contact so far I’d like to point out one thing I don’t see being mentioned that often.

    In a sufficiently advanced economy comprised of free subjects all that might be needed to send a ship to another star is a bunch of enthusiast with perhaps one typical well-to-do like-minded sponsor. In a prosperous enough world contacting another civilization doesn’t have to be a major international matter so we can say that they aren’t there because it’s irrelevant for a very advanced civilization as a whole. Nor does it have to be an undertaking achievable only by a big and powerful corporation so we can say that they aren’t there because interstellar travel makes no business (economic) sense.

    Looking at us, I believe that say 10,000 years from now there would be all sorts private ships outfitted by individuals flying in all possible directions even if humanity becomes all that post-biological and isn’t bound to a (habitable) planet anymore. And even with the most stringent rules and enforcement measures (for whatever reasons) I doubt it would be possible to prevent some of the people from contacting discovered alien civilizations on their own – once the discovery is made some form of contact would simply be inevitable.

  • Leon January 25, 2012, 12:23

    Maybe Kepler can help us with the “Recognizable transits of large artificial objects” ?

  • A. A. Jackson January 25, 2012, 12:38

    “Whether we are alone or not needs to rest on experimental search, not on a string of evolutionary inferences.”

    “A curious view has grown up, which I may call Malthuian. It is something like the assumption of Malthus, that human society or its counterpart will sustain indefinite growth in numbers and capability, so that we will be pressed to travel and swell among the stars, filling the Galaxy in a geological epoch or less. But a simple look at the Galaxy, which shows no signs of intense colonization, strongly suggests that we here must be the first.”

    “Where is everybody?” is a question already more than thirty years old. Even this argument is more plausible than the opposite one, which I might attribute to Aristotle, that our planet is the single little blue footstool in all the universe, and no other place can harbor mind-and radio telescopes. But it seems to me neither position is as persuasive as the Copernican view taken in our 1959 letter, which suggests that we are finite beings, with finite capabilities, growing but limited, who are by no means sure either of becoming universal or remaining alone. Perhaps we can find out, and that is what we ought to try to do. ”
    Philip Morrison 1997
    (About the Morrison and Giuseppe Cocconi paper published in 1959)

  • James D. Stilwell January 25, 2012, 13:45

    Adam’s comment may imply that the spectral image surrounding a space adapted race occupying an entire solar system would likely become visibly remarkable….Perhaps the color green would be the main clue to look for surrounding an distant star whose living progeny wouldn’t any longer even remember the territorial imperative….Clarke imagined such a race would seem magical to humanity. May they become our future patrons.
    James D. Stilwell

  • jkittle January 25, 2012, 13:57

    I have to say that I usually dismiss most SETI discussions because they fail the Sherlock Holmes Test. “No Data”. However, I think the Dyson sphere around a black hole makes a whole lot more sense than one around a star… ( call it a “Black Sphere” Thus I learned something from this discussion.
    To Henke’s point: Henke is is either OBVIOUSLY right or ridiculously wrong. Time may tell… or not, depending on our own fate..
    Right now we are in the position of the inhabitants of Hawaii before the arrival of Captan Cooke . They would have had a hard time imagining European culture, history and technology, and right minded individuals woudl even dopubt the existance of other ( great ) civilizations. Now in fact, in that the differences in technology levels between us and a hypothetical star fareing interstellar race are probably even greater, given we are a young culture and likely age of interstellar beings. Even demonstrating an iPAD to the Hawaiian king would be more understandable. -fun to think about-. But for now, we are apparently on our own in our quest to reach the stars. I will predict we will not detect any alien civilizations until we are among them and at least begin to approach their level of development/evolution.
    Personally I have maybe 20 years of useful work. Without an alzheimers cure , probably thirty years of life ( my family seems to get this around age 80) . with life extensions I may see 100, but my children should see that mark easily. I have a grandbaby on the way, hopefully the first of many, he may see 150 years, so my practical reach is out out the year 2160. If Jesus or the Singularity does not come before then, one of my grandchild may see the first attempts at interstellar travel in his lifetime and may observe the first colonization ship leave bound for a nearby brown dwarf , from his comfortable home on Mars or even Ceres.

  • tesh January 25, 2012, 14:31

    Consider the move towards singularity and the factors that are involved in getting there.

    What would be the time scale for such a transition?
    Is it the same for all civilisations?
    Will there be opposition along the way?

    These three questions have a whole host sub questions that need to be answered to begin to formulate a response to them.

  • Nick January 25, 2012, 14:55

    “And that logic leads you right slap bang into the Fermi paradox. ”

    It’s only a paradox if you believe sci-fi showing a galaxy full of aliens is non-fiction. Other people call it evidence against.

  • Bob January 25, 2012, 15:50

    Is anyone suggesting that dark matter may be partially accounted for by low temperature Dyson Spheres, in other words, life?

  • FrankH January 25, 2012, 16:08

    Geoffrey A. Landis has a good (as good as any…) explanation for the Fermi Paradox:
    The Fermi Paradox: An Approach Based on Percolation Theory
    http://www.geoffreylandis.com/percolation.htp

    Dyson spheres don’t make a lot of sense, but ring worlds (at least in the form of Iain Bank’s “orbitals” and not Niven ring worlds) might be detectable by Kepler; a 3 million km ring should produce an interesting signal as it wobbles in its orbit.

  • Mike January 25, 2012, 16:47

    @henk
    How can henk be so sure of his/her conclusions? Did God tell him/her?
    Seriously, considering the lack of data how can anyone be sure of these conclusions?

  • Nick January 25, 2012, 16:57

    “Is anyone suggesting that dark matter may be partially accounted for by low temperature Dyson Spheres, in other words, life?”

    No, Dyson surfaces would emit large amounts waste heat radiation (e.g. infrared or microwave) and dark matter emits nothing detectable by even the most sensitive instruments. Furthermore, various physical considerations have ruled out most of the dark matter being explainable by matter that interacts via the strong or electromagnetic forces. All or at least the vast majority of dark matter must be “ghost matter” like neutrinos (but more massive) that interacts only via the weak and gravity forces.

  • Eniac January 25, 2012, 17:06

    It’s only a paradox if you believe sci-fi showing a galaxy full of aliens is non-fiction. Other people call it evidence against.

    Right. It is a conditional paradox, aka reductio ad absurdum. You make an assumption (i.e. “aliens exist”) and then you go and show that it leads to contradiction. Normally, you then go on to discredit the original assumption, but too many people are not ready for this. They find comfort in calling the absurdum a paradox, as if there was not an easy way to resolve it.

  • Mike January 25, 2012, 17:07

    The Fermi Paradox.
    There is nobody else out there. Or…………
    We are qurantined. Or…………….
    We are ignored………….
    Other suggestions?
    We belong to somebodys domain.

  • Ole Burde January 25, 2012, 17:18

    “Is anyone suggesting that dark matter may be partially accounted for by low temperature Dyson Spheres, in other words, life?”
    Yes , Bob … YOU are , Way to go !

  • Bob January 25, 2012, 17:44

    Geoffrey A. Landis wrote (1998) “Tipler argues that a extraterrestrial technical civilization will fill the galaxy with self-reproducing probes, which will not be subject to a distance horizon. Since we have not yet learned to design such machines, it is difficult to critique this reasoning in depth. ”

    I think we do have the knowledge to build such systems if pressed. See Advanced Automation for Space Missions (NASA, 1980).

    But I want to add that we may not be able to recognize the existence of an advanced civilization. If such a civilization is highly efficient and “green”, it may be likely that they have an imperative to make an extremely light impact on the universe no matter how far they spread themselves. So much so that we may have severe difficulties detecting them.

  • A. A. Jackson January 25, 2012, 19:24

    @Mike
    The Fermi Paradox.
    Fermi’s genius was to recognize , in 1950!, that all the engineering physics problems of interstellar flight could be solved.
    We have some solutions in hand, more to come.
    There is a hidden assumption, I think Fermi had much bigger fish to fry and so never returned to the question to examine it.
    The Fermi Paradox implies then that we are looking for ourselves.
    One cannot say squat about advanced civilizations that are not anything like us, no data.
    Some say this is ok, because ‘history repeats itself’ and we can predict what our philosophy will be when we become star faring.
    So many civilizations so much time , one civilization , like us , is out there,
    presto, they should have traipsed about the Galaxy over it’s lifetime.
    I have read no analysis or seen any model that can take the current technological society we have today and project it the hundreds of years into the future when we have just self replication robot probes headed for the stars.
    (It is sobering that we can project that climate change or a bio engineered disease or some such techno thing may wipe out human civilization before the attainment of star faring. By the by ,one of the answers to the Fermi paradox.)
    Star faring for a civilization means a planet wide marshaling of social economic and political entities within an advanced technological context that past history give no guidance to predict.
    Fermi’s paradox is really a question with no way (right now) as to how to answer it.

  • Mindrust January 25, 2012, 20:26

    As more time goes on and we continue to find nothing (particularly the fact that we have not been contacted), I actually do not get pessimistic about the possibility of advanced civilizations as one might assume, but I actually become more convinced of the Zoo hypothesis and its related variants. I know it’s not a very popular hypothesis because it is untestable, but it certainly solves the Fermi paradox and it fits with our assumption that there should be a pretty fair amount of advanced civilizations in our galaxy.

    The second major objection against the Zoo hypothesis is that it would only take one individual to breakthrough the cage to expose the Zoo keepers. That’s a legitimate criticism, but what if the there is a hegemonic power in the galaxy? A hegemony in a crowded galaxy would make this idea at least a bit more plausible, since there would likely be a universal cultural/legal policy in such a setting.

    The neat thing about the Zoo hypothesis and related hypothesis (interdict hypothesis, simulation argument, planetarium hypothesis) is that there is wiggle room for technology that according to our current understanding of physics, seem implausible or far-fetched, i.e. wormholes, warp drives and artificial baby universes. Wormholes or warp drives would pretty much ensure that a hegemony could not collapse, making the Zoo hypothesis even stronger. Perhaps we’re getting a glimmer of these exotic possibilities with the recent CERN result (of course, the results have not been confirmed by an independent party yet so I won’t hold my breath). For the moment, these are very contentious and speculative topics, since we do not have a quantum theory of gravity to determine the reality of such things, but it’s not a bad idea to keep our minds open to the possibility.

  • Rob Henry January 25, 2012, 22:27

    FrankH, the most devastating problem to Geoffrey Landis’ model is that it simply seems to collapse when the movement of stars in a galaxy is accounted for. It would now seem then this method could only delay colonisation from reaching completion for a few extra tens of millions of years at most. At least I see that he tried to attack this problem, but it seems that he has had as little success at answering it as anyone else. In that link you give he writes:

    “In addition to these assumptions, the model ignores stellar drift. The time scale for star positions to change is on the order of a million years. It is impossible to project the sociology of extraterrestrial civilizations for time scales on this order. It is reasonable to suggest that a civilization that has existed for millions of years without colonizing would be likely to have evolved into a stable civilization that has no imperative to do so.”

    So his only answer it that his model can still would is ALL colonies give up colonisation FOREVER.

  • Rob Henry January 25, 2012, 22:46

    To me the Fermi paradox is that IF we hope to be able to contact ETIs, THEN me must admit that they are already here (thus it is a true paradox). If Mindrust was really speaking to that with his take on the zoo hypothesis, it would not be sufficient.

    For the zoo hypothesis to solve the Fermi paradox we also need the keepers to allow free communication between the kept civilisations.

  • Eniac January 25, 2012, 23:34

    A.A.:

    I have read no analysis or seen any model that can take the current technological society we have today and project it the hundreds of years into the future when we have just self replication robot probes headed for the stars.

    Right, because that is not possible. However, the Fermi paradox is based only on a very general assumption: There is a possibility that an intelligent civilization can spread among the stars. No models or predictions of any sort are called for. All that is needed is the possibility of self-replication of “life” (original or artificial) across interstellar distances. Autonomous self replication implies expansion into all available living space. Bacteria do it, trees do it, people do it too. If you know of a mechanism by which this rule could be broken, or an example of it being broken in experience, please name it.

  • Mephane January 26, 2012, 4:24

    there are no other civilizations in this galaxie. We are the only one. That is almost a fact. I think that 1 of the 10 million spiral galaxies have maybe 1 advanced civilization. I think complex life is very common, but intelligent life is extremely rare. I maybe even go as far that we are the only one.

    Just as a heads up, your number of galaxies is several orders of magnitudes low. We are talking about billions of galaxies consisting of billions of stars each. In the end, all power goes to the numbers. Ironically, that could mean, depending on the definition of “rare”, civilizations could be both rare and common at the same time. Rare in terms of how many civilizations exist per N number of stars, but common in terms of how many civilizations exist within a galaxy, or even the entire universe.

  • Avatar2.0 January 26, 2012, 8:01

    The Fermi Paradox is one side of the coin – it essentially tells us that there are no technological civilisations in the local cluster of galaxies.

    The other side of the coin is the sheer complexity of the simplest molecule that can replicate itself even halfway reliably (I’m NOT talking about the simplest cell, etc). In order to come into being, this simplest molecule requires hundreds of chemical steps to occur in just the right order – which is insanely improbable.
    This improbability of life arising explains why the the Milky Way galaxy – and the other galaxies from the local cluster – are untouched by intelligence, shaped only by the laws of physics, thus explaining the Fermi Paradox.

    All other explanations of the Fermi Paradox I’ve heard, at the very least badly fail Occam’s razor.

  • ljk January 26, 2012, 12:42

    If you and your species live long enough, you can tour the galaxy without ever leaving your home star system. Just let the natural interstellar movements of your sun do the work.

    If you are really ambitious yet you still don’t want to leave your home star system, Fritz Zwicky once envisioned using a sun like a rocket (causing one side of the star to flare up and aim in the direction you want to go) to propel your entire solar system at a decent rate across the galaxy. Talk about your fusion propulsion!

    Have we found any stars zipping through the Milky Way at rather unusual speeds?

    If nothing else, if we can at least imagine these things, imagine what a much older and smarter intelligence who really appreciates the cosmic perspective might be able to do.

  • philw1776 January 26, 2012, 13:14

    The contrived “explanations” for the Fermi Paradox show our unwillingness to accept the Occam’s Razor answer, there aren’t any. Of course since any halfway scientific answer requires at minimum an attempt at falsification, is why I support modest and creative SETI searches.

    Those citing the law of large numbers, hundreds of billions of galaxies with hundreds of billions of stars in each (total say 10 exp 23), as evidence that there MUST be tech civilizations elsewhere forget that we have yet to have any scientific proof of any life however simple elsewhere. Our biological and astronomical ignorance must allow consideration of the possibility that life itself might be a 10 exp – 25 or worse improbability. Or that the multiplicative improbability of a technical civilization P(life) x P(complex animals) x P (intelligence) x P (technology) and other factors might yield a similar or worse number. The “galaxy must have lots of alien societies” mantra is an act of faith, not science. The only evidence we have should provide some skepticism for this extraordinary claim.

  • Bob January 26, 2012, 13:24

    Avatar2.0, I have to disagree with your assessment. Both Occam’s razor and the improbability of life arguments rest on unprovable assumptions on our part based on our ignorance of nature.

    I could as well argue that if life emerges anywhere in the galaxy, known mechanisms allow at least microbial life to propagate through space and potentially be able to seed every hospitable world in the galaxy in only a few tens or hundreds of millions of years. That would allow similar DNA based life to begin to evolve on countless worlds.

    If we eventually find evidence of microbes in the solar system, say in comets,
    we could assume that life is common in the galaxy which certainly impacts the Drake equation.

  • Alex Tolley January 26, 2012, 14:47

    Avatar 2.0. That is a creationist argument and exposes a complete lack of understanding of how evolution works, even at the the chemical level.

  • Nick January 26, 2012, 14:49

    “To me the Fermi paradox is that IF we hope to be able to contact ETIs, THEN me must admit that they are already here (thus it is a true paradox).”

    Yes, and the Tolkien Paradox is that IF we hope to be able to contact hobbits, THEN we have to lump daydreams into the same category as logic and fact.

  • Nick January 26, 2012, 15:27

    Avatar2.0: “…the sheer complexity of the simplest molecule that can replicate itself even halfway reliably (I’m NOT talking about the simplest cell, etc). In order to come into being, this simplest molecule requires hundreds of chemical steps to occur in just the right order – which is insanely improbable.”

    It’s actually worse than this — abiogenesis requires the coming into being not just of a single molecule, nor even of just a single organism (i.e. any set of molecules capable of sustained replication) but of a closed ecosystem. Not only are all known examples of single organisms of astronomically improbable complexity, but all known examples of closed ecosystems involve _several_ such organisms. If a single living organism of any species (e.g. just a single species of bacteria) popped into being it would soon die due to lack of nutrients. Each additional organism required to create an actually closed ecosystem makes the event exponentially less probable.

    Of course, some of this complexity may have been created by Darwinian evolution from a previous simpler but now extinct set of organisms forming a simpler closed ecosystem. But after decades of trying we are nowhere near being able to figure out how to recreate such a simple closed ecosystem. Just a lot of rampant speculation, wishful thinking, and experiments that require very artificial (and thus also astronomically improbable in nature) conditions.

    The odds of abiogenesis will soon be put to the test. I predict we will within the next few decades discover earth-sized planets perfectly located in the middle of habitable zones, full of liquid water oceans, continents, lakes, rivers, and tidal zones, with climates even milder than earth, and completely sterile. We will not discover any other independently originated life in our galaxy (and panspermia is also unlikely).

  • ljk January 26, 2012, 15:39

    Type III Dyson Sphere of Highly Advanced Civilizations around a Super Massive Black Hole

    Authors: Makoto Inoue, Hiromitsu Yokoo

    (Submitted on 23 Dec 2011)

    Abstract: We describe a new system for a society of highly advanced civilizations around a super massive black hole (SMBH), as an advanced Type III “Dyson Sphere”, pointing out an efficient usage of energy for the advanced civilizations.

    SMBH also works as a sink for waste materials. Here we assume that Type III civilisations of Kardashev classification [1] form a galactic club [2] in a galaxy, and the energy from the SMBH will be delivered to the club members, forming an energy control system similar to power grids in our present society.

    The energy is probably transmitted by a sharp beam with coherent electro-magnetic waves, which provide a new concept for the search for extraterrestrial intelligence (SETI) via detection of such energy transmission signals.

    This expands the search window for other intelligences within the Universe.

    Comments: 4 pages, 1 color page

    Subjects: General Physics (physics.gen-ph)

    Journal reference: Journal of British Interplanetary Society, Vol. 64, pp.58-62, 2011

    Cite as: arXiv:1112.5519v1 [physics.gen-ph]

    Submission history

    From: Makoto Inoue [view email]

    [v1] Fri, 23 Dec 2011 06:09:53 GMT (5350kb)

    http://arxiv.org/abs/1112.5519

  • ljk January 26, 2012, 15:57

    Forget Dyson Shells as habitats for organics or even homes for vast Artilect minds – imagine them as a megaweapon:

    http://www.orionsarm.com/eg-article/48fe49fe47202

    The birth of the rocket and for most of its long history was not as an instrument to explore the Universe, but as a weapon. So too a powerful being or beings bent on either self-preservation or oppression or both might construct a Dyson Shell to take out the galactic competition at all levels.

  • Bob January 26, 2012, 16:31

    Alex, it’s not a Creationist argument. Creationists do not rely on improbability, but on design. Improbability has been the standard view among scientists for most of the 20th century.