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SETI: Rummaging in the Data

Astronomy is moving at a clip that sees more data accumulated than can possibly be examined at the time they’re collected. We’re creating vast storehouses of information that can be approached from various angles of study. Now ponder how we might use these data for purposes beyond what they were collected for. In a new paper submitted to the Astronomical Journal, Ermanno Borra (Université Laval, Québec) looks at how standard astronomical spectra — including those already taken — can be used as part of SETI, the Search for Extraterrestrial Intelligence.

Here’s the idea: Suppose somewhere out there a civilization decides to reveal its existence to the rest of the galaxy. These extraterrestrials reason from their own experience of science that an advanced civilization will study the sky and take spectra of astronomical objects. These spectra become the medium upon which the senders impose their signal. At our end, spectroscopic surveys of vast numbers of stars allow us to accumulate data that may contain evidence of an unusual signal, a spectrum deliberately crafted to be so striking that it calls attention to itself.

How to create the signal? Through modulating the spectrum by sending short bursts of laser light, an idea Borra addressed in a 2010 paper, as discussed again in this one:

Borra (2010) shows that periodic time variations of the intensity signal originating from a pulsating source modulate its frequency spectrum with periodic structures. Periodic time variations of the intensity signal originating from a pulsating source with periods between 10-10 and 10-15 seconds would modulate its spectrum with periodic structures detectable in standard astronomical spectra. Periods shorter than 10-10 seconds could be detected in high-resolution spectra. Note that the modulation is rigorously periodic in the frequency units spectrum but not in the wavelength units spectrum.

Image: A panoramic image of the Milky Way. Could we use spectroscopic data from surveys already conducted to find evidence of other civilizations? Credit: Photopic Sky Survey.

You can see the beauty of this proposition. We already have mountains of spectroscopic data acquired for other studies, data that can be analyzed visually or through Fourier transform software. Borra wants to make astronomers aware of this potential use for such data as a complement to existing optical SETI work carried out at sites like the Wyeth Telescope (Harvard/Smithsonian Oak Ridge Observatory) and the SERENDIP instrument at UC-Berkeley. The latter are cutting-edge projects, but with some limitations, the biggest being that they can observe only one object at a time. They also require either dedicated instruments or telescope time on standard telescopes, a limitation that a database hunt of earlier work surmounts.

Borra finds that the energy needed to generate the needed signals is feasible even for a civilization like ours — he analyzes it in terms of current equipment by referencing diode-pumped laser technology similar to the Helios laser designed at Lawrence Livermore National Laboratory for inertial confinement fusion studies. The result: An isolated signal transmitted at 1000 light years (a sphere within which there are roughly a million stars) would be detectable with today’s instruments. A spectroscopic survey like the Sloan Digital Sky Survey could find it.

By ‘isolated’ signal, Borra means a signal sent from a place distant enough from the home star so that the signal would not be directly superimposed on the spectrum of the star itself. The other case is a signal sent from the home planet, one that would therefore mix with the stellar spectrum. Now the signal becomes harder to detect because it is considerably weaker than the total energy of the stellar spectrum, requiring the extraterrestrial senders to resort to more powerful sources. Here Borra references the 2004 paper from which he drew the Helios comparisons:

… we can assume that, considering the Moore’s law of laser technology, a more advanced civilization should have no trouble increasing the laser power by 2 to 3 orders magnitude making the signal readily detectable. For a solar-type star at 1000 ly the signal would then be comparable to the stellar background and thus easily detectable… The Moore law suggestion is intuitively justified by simply imagining how Howard et al. (2004) and the present article would have been received before the invention of the laser 60 years ago, when the signal would have had to be generated with light bulbs!

A Kardashev Type I civilization should be able to manage the power output to make its superimposed signal observable at nearby stars, but a Type II would be capable of harnessing all the energies available from its home star, making the production of such signals feasible for vast numbers of potential recipients. Because, as Jill Tarter has often commented, civilizations trying to contact us are likely to be more advanced technologically than we are, the possibility of finding such Type II civilization signals in astronomical spectra becomes an intriguing issue.

What’s appealing about Borra’s approach is its sheer simplicity. The database-mining idea for SETI has a history in the literature going back to papers in 1977 (Zbigniew Paprotny) and 1980 (Daniel Whitmire and David Wright), who suggested searching for anomalous spectral lines originating from radioactive fissile waste material. Geoff Marcy and Amy Reines have carried out a search of 577 nearby stars looking for emission lines too narrow to be natural. Signal-finding algorithms incorporated into existing software can be used with present and future spectroscopic data to continue this hunt, all achieved, as Borra says, with a few lines of code.

Is a SETI signal to be found in our databases? The paper is Borra, “Searching for extraterrestrial intelligence signals in astronomical spectra, including existing data,” accepted for publication by the Astronomical Journal (preprint). Thanks to Antonio Tavani for first calling this one to my attention, and several other readers who also sent in the link.

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Comments on this entry are closed.

  • lurscher October 26, 2012, 10:23

    “we can assume that, considering the Moore’s law of laser technology, a more advanced civilization should have no trouble increasing the laser power by 2 to 3 orders magnitude making the signal readily detectable.”

    Totally wrong analysis. signal power decays as the square of distance to source, so increasing power by brute force just adds a constant to the decay. If you are broadcasting, you want your signal to spread in all directions, which involves more energy expenditure. We can easily presume that as civilizations connect ‘socially’ to the neighbours they discover, they might settle into directional channels with less energy expenditure and invest less in broadcasting. The window of time where a civilization might invest in doing broadcast might be sparse, over the length of their history.

    Other, more sensible possibility for what an alien technical civilization might attempt (asssuming broadcasting their presence is their goal) is that they will try to send such signals in a region of the spectrum where their sun spectra is weak. So smart listeners will realize that they see two different signals overlapped

  • GaryChurch October 26, 2012, 13:31

    We may be too stupid to survive. Intelligent beings would never consider sending out invitations to possibly hostile alien civilizations. Stephen Hawking said as much to the world.
    It may be a common occurence in this galaxy that goldilocks planets with existing ecosystems are bombarded with comets from invaders still centuries away. This faster first wave would seek to sterilize the planet as much as possible and then introduce their own organisms to prepare for colonists. Several centuries later when the starships arrive they would find a world ready for them.
    Hoping that other civilizations are enlightened and not seeking lebensraum is a pretty risky policy. Actually advertising your planet as being a great place to live might be considered suicidal. Or just stupid.

  • NS October 26, 2012, 15:22

    re optical SETI, there is currently an all-sky survey underway at Harvard:

    http://seti.harvard.edu/oseti/allsky/

    http://www.planetary.org/blogs/bruce-betts/20120830-seti-update.html

  • GaryChurch October 26, 2012, 15:42

    Sorry, I put that rather poorly. It may be common for goldilocks planets to be bombarded with comets directed by an advance force to prepare a new ecosystem for colonists still centuries away. I believe we have been conditioned by speculative fiction that aliens will possess advanced technology. This is not necessarily so. We actually lack only one technology for star travels; cryopreservation. Freezing and reviving a human being is not a very complex problem and is mostly about keeping ice crystals from forming and causing damage. I suspect a civilization that has evolved along different lines may be decades behind us technologically but all the same on their way here to destroy us and convert this planet into a second version of their own. If technological civilizations mostly self-destruct at around our stage of development it is not such a stretch to suppose that of the very few that survive, some of them may be invasive and aggressive and already embarked on missions to conquer other worlds……like ours.

    I would like to be able to say we could defeat such an invasion force with our more advanced Atomic Spaceships but of course, we are more interested in shareholder checks than staying extant vs. extinct.

  • Kwan October 26, 2012, 16:50

    My first thought when thinking about ETI is what kind of weaponry could we detect. I’d look for signs of unusual flows of gamma radiation. Why? Fusion and M/AM annihilation produces gamma rays if I’m not mistaken. Assuming that the ET’s are indeed technologically more advanced than us and they’ve mastered the two, would it be possible to somehow make a distinction between gamma rays produced naturally and those produced by something man-made? I’m guessing that depends on if said ET’s are type I or II. A type II civilization should definitely be able to modify the Gamma ray emissions from it’s parent star considering they should in theory interact with it on a very large scale. Could someone maybe shed some light on this for me? I’m only 21 with a year and half of college so there’s a good chance my understanding of the above is flawed.

  • Wojciech October 26, 2012, 17:09

    “If you are broadcasting, you want your signal to spread in all directions”
    No need to. If you are Kardashev 1 civilization you already know position of all the habitable planets-if you wish of course(and within certain limits, but these limits probably are within the range of the signal you can send)

    “Intelligent beings would never consider sending out invitations to possibly hostile alien civilizations”
    Too late. Our biosphere already send its invitation billions of years ago.
    Our civilization? Well, it depends on what potential aliens could see. But within 7,000 years ago when agriculture and cities were started to around late XIX century when cities started using widespread street lights(or around 1000 AD if you count first large scale uses).

  • Astronist October 26, 2012, 19:21

    An interesting idea, but suffers from the same weakness as traditional radio SETI: we have no reasonable expectation that any alien civilisation is trying to attract our attention (because they cannot know of our existence, and because it is improbable that their development is so closely synchronised with our own).

    Gary Church, I’m not sure I follow your logic, or that of Stephen Hawking. Earth has been detectable as a living planet (thru the oxygen in its spectrum) from interstellar distances for several billion years, and the invaders don’t seem to have arrived yet. (Unless there’s a major coverup going on…).

    Stephen

  • Astronist October 26, 2012, 19:46

    @GaryChurch
    “Freezing and reviving a human being is not a very complex problem and is mostly about keeping ice crystals from forming and causing damage.” — This sounds interesting. My own researches so far have only uncovered cases where a person was accidentally frozen in snow or water for a few hours, and then resuscitated. I would be fascinated to hear what references you have for clinical trials of cryopreservation of human subjects for time periods which might be relevant to interstellar travel.

    “I suspect a civilization that has evolved along different lines may be decades behind us technologically but all the same on their way here to destroy us and convert this planet into a second version of their own.” — A strange idea indeed! If they are decades behind us technologically, then they can neither travel here, nor destroy us when they do. If you try to imagine countries on Earth trying to invade a hypothetical Earth-analog exoplanet, I think you will see what I mean.

  • roger richardson October 26, 2012, 20:52

    The ultimate question is finding ET by their intentional efforts or signal leakage.
    Intentional efforts might be in the expected RF or lasers.
    Signal leakage would be much harder to find perhaps.. But it depends on what kind of leakage we look for. If there is a large amount of local interplanetory travel by ET what kind of emissions could be seen? Could propulsion efforts be seen at interstellar distances? There could be occasional random spikes as they move within the system. The expectations are they would have to do some communications between the active craft. Again just occasional random spikes with no real content.
    How could SETI plan to isolate this type of unintentional communication?
    Questions by the uninformed to the experts.

  • Eniac October 26, 2012, 21:09

    My own researches so far have only uncovered cases where a person was accidentally frozen in snow or water for a few hours, and then resuscitated. I would be fascinated to hear what references you have for clinical trials of cryopreservation of human subjects for time periods which might be relevant to interstellar travel.

    If the first part of this was really true as written, than we would be pretty much there. Once we can freeze a body solid for a few hours and revive it after, the rest is just cooling it down some more to extend the stasis to arbitrarily long periods.

    I haven’t heard that this has been done for humans, but there are some animals that can do it naturally. So, I have to agree with Gary here, the problem does not seem unsurmountable.

  • GaryChurch October 27, 2012, 1:13

    “Earth has been detectable as a living planet (thru the oxygen in its spectrum) from interstellar distances for several billion years,”
    “— A strange idea indeed! If they are decades behind us technologically, then they can neither travel here, nor destroy us when they do.”

    It is difficult to get people to think outside the box; I found this out during my unhappy years in military intelligence. I wrote that the only technology we lack is cryopreservation and so if a civilization with a technology like we had in the 1960’s had invested resources in freezing organisms, they very well may have solved the problem and been able to launch a military expedition using bomb propulsion. Our technology in the 60’s was not able to even detect exoplanets. Saying they would not have been capable of starflight is tunnel vision; they do not have to be like us or develop exactly like us. Let me restate as clearly as I can without writing a book;

    1. We have been radiating signals for a century. Aliens may have detected us as early as 30 or 40 years ago if they are in a nearby starsystem.

    2. With technology no more advanced that nuclear weapons they could have used pulse propulsion to launch an expedition. The only technology we lack is cryopreservation and they may know how to do it or be sending generation ships.

    3. They would probably send much faster starships centuries ahead of their colonists to divert comets toward our planet to sterilize it as much as possible so they can introduce their own ecosystem.
    So the question is when is that fast first wave going to arrive?

    As for clinical trials of freezing people- that is just sarcastic bullying. I know I am the new guy here but don’t attack me for having vision.
    I said it is a matter of stopping ice crystals from forming; http://www.sciencedaily.com/releases/2006/12/061213104104.htm
    http://www.sciencedaily.com/releases/2006/06/060620171022.htm

  • coolstar October 27, 2012, 4:28

    Interesting idea. Borra is a bright guy; he originated the modern version of a liquid mirror telescope using mercury as the liquid. I suspect Howard et al. in the 2004 paper actually underestimated the number of stars within 1000 light years by an order of magnitude or a bit more since they apparently didn’t include M dwarfs.

  • James Jason Wentworth October 27, 2012, 4:55

    One way to optically “broadcast” an anomalous signal in all directions (the anomaly being a sure sign of artificiality) would be to “label” one’s sun by dumping into its atmosphere artificial elements that do not occur in nature (or do not show in stellar spectra in abundance). In his 1968 non-fiction book “The Promise of Space,” Arthur C. Clarke wrote that in some cases, the required amount of material would be a few hundred thousand tons, which a sufficiently advanced (no Clarkean pun intended) civilization could manage. Also:

    If/when humanity develops nuclear fusion (maybe helium-3/deuterium fusion), perhaps the then-superfluous uranium and plutonium could be electromagnetically shot into the Sun from the Moon, after first being lifted to geosynchronous orbit (to be loaded aboard waiting inter-orbital space tugs) by a space elevator?

  • dav_daddy October 27, 2012, 8:13

    I think to give an analogy what GaryChurch is trying to say in essence is. What if Hitler had won WWII?

    Given that not unfeasible a scenario I could easily see Hitler Jr mobilizing the planets resources to mount an invasion.

    This rather on point to his question where the aliens are slightly behind us in overall technology yet have mastered intergalactic travel.

    Gains in both energy production & propulsion are among the most common advances to come about as a result of weapons research. Dictatorships while stifling many areas of research are very well suited to putting new technology to use (even to the detriment of the populous) once breakthroughs have been made.

  • Mark Wakely October 27, 2012, 13:02

    I have to agree with Gary Church to some degree regarding the dangers of broadcasting our existence. While our biosphere and its oxygen content have indeed been “broadcast” for billions of years, that doesn’t necessarily translate into a habitable world. It wouldn’t tell them if we have constant hurricane winds, or if plate tectonics are so active that severe earthquakes are a common occurrence around the world, or if massive ocean tides regularly sweep across the continents. Should they have the ability to observe details on our planet they would know our ancient conditions, but not conditions on our planet in the here and now. Depending on how far away they were observing, the view they would have of Earth would vary considerably. Some far away civilizations would see a snowball Earth during one of our many ice ages; others would see an Earth in decline after one of the great die-offs that have occurred throughout history. You have to wonder if advanced civilizations know it’s a fool’s errand to rush to a planet that looks ripe for the taking, only to arrive and find it’s now woefully inhospitable due to any number of disasters, natural or otherwise, that occurred during the long journey. (FTL travel would allow them to see the disaster unfold rapidly. About all they could do then is turn back and head home.) They might also know that any planet capable of broadcasting a deliberate signal across the void might also be perfectly capable of defending itself if attacked; is it worth the effort to invade if the “reward” is utter defeat, and even perhaps a counter-invasion? Then again, if they thought the signal was primitive by their standards and they could arrive here quickly enough, they might gamble that we’re no match for their invasion force and come full speed ahead. I think given all the variables, the safest conclusion for an advanced civilization would be to sit tight and search for signals while maintaining as much anonymity as possible. But then again, a warrior race of beings might never play it safe if conquest rules their genes.

  • GaryChurch October 27, 2012, 15:05

    “While our biosphere and its oxygen content have indeed been “broadcast” for billions of years, that doesn’t necessarily translate into a habitable world.”

    Mark Wakely also points out that change is the natural condition of the universe and civilization like ours might find itself doomed due to any number of causes both external and internal. What would they do if they detected signals from a thriving world? Decide not to go extinct and prepare to transplant their ecosystem to a new home- or just die?

  • Rob Henry October 27, 2012, 16:40

    Garychurch
    Your referenced methods for cryopreservation sound rather unpromising in its application to preserving humans over interstellar distance. In the first method, we can’t add concentrated sulphuric acid to human tissue, and, in the second, that glass would eventually crystallise.

    Fear not, here would be my desperate attempt… I would also cool the body rapidly once it got close to freezing point, but, in this instance, to stop too many reactions occurring at the new altered chemical potential. This is because I would have increased the pressure to a few hundred at exactly that point.

    If the problem is really as simple as all the researches seem to believe, and freezing expansion is the sole cause of the damage, then only ice I need be excluded, and under those conditions it would not be able to form.

    To me, it seems that only a few minor issues have to be addressed before I can collect the Noble for my contribution, foe example… The chemical potential of 50 – 100 atmospheres O2 looks explosively dangerous so we would first want to flush every nook and cranny with N2. I can not think of any air internal body airspaces that could not also be rapidly pressurised, but that should also be looked into.

  • Adam Crowl October 27, 2012, 17:36

    Gary Church’s paranoid speculations would be interesting if it wasn’t for the fact that we’re (probably) being observed covertly and (could) have been so observed for millennia. Clearly the ETIs don’t want to bomb us out of existence. Just what they do want is anyone’s guess – plenty of room for paranoid speculation!

    As for “Orion”, sorry, doesn’t work. The interstellar version that everyone references didn’t & doesn’t exist because it requires high burn-up fraction pure nuclear fusion devices – which don’t exist. If we could make such, then no doubt we’d have heard about it by now. Fission “Orion” is a massive under performer for interstellar missions. Even the fusion boosted version might get – at most – about 1,200-1,500 km/s exhaust velocity. Not really enough to get to other stars in less than millennia.

    Of course perhaps 1,000 year voyages are acceptable for ETIs, but with such patience for crossing the gulfs of space, they don’t seem likely to be in a hurry to invade.

  • Wojciech October 27, 2012, 17:43

    “While our biosphere and its oxygen content have indeed been “broadcast” for billions of years, that doesn’t necessarily translate into a habitable world. It wouldn’t tell them if we have constant hurricane winds, or if plate tectonics are so active that severe earthquakes are a common occurrence around the world, or if massive ocean tides regularly sweep across the continents”
    If they have telescopes who are able to take images of our planets with decent resolution-they would have this information. And since even our civilization is capable in principle of designing and creating such telescopes in foreseeable future, then a Kardashev I civilization would probably be able to have even better ones.
    Here is an interesting SF idea(which even doesn’t take into account such options as gravity lensing):
    Galactic Life Imager
    http://disc.yourwebapps.com/discussion.cgi?disc=159729;article=102431

    If you are seriously thinking that alien civilizations would eradicate others, then optimal strategy would be to destroy all possible alien habitable worlds. Meaning that such a civilization would already destroyed life on our Earth eons ago.
    Anyway, such idea doesn’t seem to likely considering that we exist.

  • Rob Henry October 27, 2012, 19:08

    Above, I wrote “a few hundred” when I meant “a few hundred atmospheres”.

  • James Jason Wentworth October 28, 2012, 0:24

    Mark Wakely wrote (in part):

    “I think given all the variables, the safest conclusion for an advanced civilization would be to sit tight and search for signals while maintaining as much anonymity as possible. But then again, a warrior race of beings might never play it safe if conquest rules their genes.”

    Yes, that is a possibility that many astronomers and SETI enthusiasts have discounted (‘We need *never* fear visitors from the stars because if they’re technologically advanced enough to come here, they will also be equally advanced socially and morally, and they will have learned to live in peace, etc.’), but I have always considered that to be a naïve assumption. Intelligent beings could come to Earth to wipe out humanity for any number of reasons, reasons which might even be unfathomable to humans for the simple reason that the aliens will not be human and cannot be presumed to think like–or be motivated by the same things as–humans.

  • GaryChurch October 28, 2012, 16:00

    “If we could make such, then no doubt we’d have heard about it by now.”

    No. We would not have heard about it. That would be classified- just like all the star wars weapons development. We do not even know how much money they have spent on this stuff. You seem pretty ignorant about much of what you claim to be fact. C,mon Adam!

  • Curt Wohleber October 28, 2012, 16:33

    The pre-emptive strike already happened. Long ago, aliens engineered an organism that emitted a lethal toxin: oxygen. There were unexpected consequences.

  • Joe G October 28, 2012, 18:03

    What if everyone is listening and no one is talking?

    Scenario: advanced space faring civiliztion with regular transportation to systems within say 10 to 50 light years.

    Would these guys necessarily need to be broadcasting (either omni-directionally or narrow beam) all the time? Look at the way airlines work – they have short bursts of local radio traffic when they leave an airport and when the arrive… they might be using passive navigational aids like GPS, but usually voice communications are pretty few and far in between during the ride. (I know they broadcast identifiers for air traffic control but forget about that for a minute)

    I sometimes wonder if there are alien SETI’s listening and saying, hmmm… we’ve been listening for 100 years, why aren’t we hearing anything by now?

    Maybe WE need to break the ice and start broadcasting very powerful, continuous, obviously artificial signals that even a 12 year old Ham radio operator would recognize. Something like a simple repeating signal, like a beacon. Who knows, in 5 or 10 or 20 years we might hear something back.

  • Astronist October 28, 2012, 22:15

    @GaryChurch
    Thank you. I am not attacking you for having vision, but for trivialising the immense difficulties, both of interstellar travel and of adapting biological life to survival in space. (Your references on cryopreservation seem to suggest that we are still nowhere near clinical trials on living people.)

    The reason I say that a civilisation at or below our own level is incapable of interstellar flight is because of its enormous energy demands, amounting to a multiple of current global annual world production even for a crossing time measured in centuries, plus the extreme reliability demanded of systems, plus (for a manned or inhabited vehicle) the difficulties of developing small-scale self-contained biospheres.

    Your alien invasion scenario invites the question as to why they should observe Earth for periods on the order of hundreds of millions of years, but do nothing until they pick up weak artificial radio signals. For surely you would agree that the probability of two civilisations evolving completely independently within a few tens of light-years of one another so that their development was synchronised to less than a thousand years within the ten billion years or so of the existence of Earth-analog planets so far would be vanishingly unlikely?

  • A. A. Jackson October 29, 2012, 9:48

    I like the drift of this paper.
    I have always thought Dyson and Kardashev technologies a great talking point.
    Problem I always saw was that there , a lot, not all, followers like the BULL IN THE CHINA SHOP signature.
    A paper like this points out there can be, should be , maybe ways that advanced civilizations finesse their presence either overtly or inadvertently.
    I have always thought “what if Dyson civilizations or Kardashev civilizations really possess the command of an instrumentality to harness the potential of a star or a galaxy or galaxies…. yet proceed with an ingenuousness that does not stick out like a sore thumb!
    More intellectual insight should be expended upon this problem.

  • ljk October 29, 2012, 10:47

    Adam Crowl said on October 27, 2012 at 17:36:

    “Gary Church’s paranoid speculations would be interesting if it wasn’t for the fact that we’re (probably) being observed covertly and (could) have been so observed for millennia. Clearly the ETIs don’t want to bomb us out of existence. Just what they do want is anyone’s guess – plenty of room for paranoid speculation!”

    LJK replies:

    I would go so far as to say that if there are advanced ETI in the Milky Way galaxy, they may not even know we exist. Our electromagnetic “footprint” on the celestial scale is a sphere less than 200 light years across in a galaxy 100,000 light years wide encompassing 400 billion star systems.

    Carl Sagan once estimated that if there were one million technological civilizations in the galaxy, then the nearest one should be about 200 light years from Earth on average. So obviously such an ETI would have to wait another century or so to be able to detect humanity in this manner. This naturally assumes they are even conducting such a sky survey with very sensitive detectors and a host of other factors to discover our existence.

    Most of our signals are fairly weak and not meant for interstellar detection, so that footprint is even less prominent than many imagine it to be. Even our sun fades into the background of all those other stars after moving just a few dozen light years away from it.

    Assuming only the current methods we employ to find exoplanets, an ETI might be able to find Jupiter and Saturn. Their astronomers would note that our largest Jovians are not very close to Sol, which would apparently mean they did not come plowing through our system and knocking out the smaller Earthlike worlds along the way. How long would it take them to find Earth, however?

    I suppose for an advanced setup that even if the ETI did not notice our transmissions, they could eventually detect Earth as a planet (after sifting through 400 billion star systems) and measure the contents of our atmosphere. Powerful telescopes in space could even see our oceans and continents, perhaps more?

    All that being said, would this be enough to compel an ETI to take further steps with Earth and humanity? I have to wonder the following: Are there many Earthlike worlds in the galaxy? If so, would that diminish us as a target of interest? Then you have to ask if an ETI would even be interested in worlds like ours anyway? We are interested in Earthlike exoplanets because that is the kind of place we come from. An ETI from a very different environment may think otherwise, or perhaps not even bother with places like Earth other than to record them for consistency. Really advanced ETI who would not be bound to any one planet might not be terribly interested in such commonplace rocks and the creatures who still cling to them.

    Adam then said:

    “As for “Orion”, sorry, doesn’t work. The interstellar version that everyone references didn’t & doesn’t exist because it requires high burn-up fraction pure nuclear fusion devices – which don’t exist. If we could make such, then no doubt we’d have heard about it by now. Fission “Orion” is a massive under performer for interstellar missions. Even the fusion boosted version might get – at most – about 1,200-1,500 km/s exhaust velocity. Not really enough to get to other stars in less than millennia.”

    LJK replies:

    Adam, I have long respected your knowledge and opinions on this subject. If Orion cannot get us to even the nearest stars in anything shorter than a millennium or so, then that is unfortunate for the current state of our species. Of course Orion might still work for getting around the Sol system, assuming we can get past our fears of anything nuclear powered.

    I have always liked Orion primarily because it has a method of propulsion that exists now in reality. Even sustained fusion is having problems becoming a reality despite such setups as the National Ignition Facility throwing years and billions of dollars at the goal. Other methods are even more expensive and in certain cases outright fantasy.

    While I admire the laser-powered light sail concept both for its possibilities and its aesthetics, my concern is largely with the method of propulsion. If you think getting folks to approve of nuclear bombs in space is difficult, imagine the reaction to a giant space laser. Even if a space agency was given the funding and resources to build such a device, there would be more than a little paranoia about the laser being used as a weapon. Whether that could ever actually happen or not is not the point; the fear and resistance to a big space-based laser system alone is likely to keep it from happening any time soon. All of this brings us right back to square one and another forty years of more papers and talking about sending a star probe to Alpha Centauri.

    Adam then said:

    “Of course perhaps 1,000 year voyages are acceptable for ETIs, but with such patience for crossing the gulfs of space, they don’t seem likely to be in a hurry to invade.”

    LJK replies:

    If starships are operated by Artilects (which would effectively make the entire ship an Artilect), taking thousands of years to move around a galaxy that is ten billion years old may not phase such beings. It would not surprise me at all if the first alien star vessel we do encounter is fully artificial, or that most of our interstellar ships are also essentially Artilects.

    I know this isn’t quite the same scale as a thousand years or more, but look at how our two Voyager probes are still functioning in deep space over 35 years after their launches. They were only supposed to last as long as their encounters with Jupiter and Saturn through 1981, with anything after that being a bonus. Could a human crew have kept functioning mentally and physically this long in space, especially knowing that they would never be coming back to Earth or encounter anything else in their lifetimes? Not to mention how much more complex and expensive their ships would have had to been in order to maintain a human crew for decades. As a final plus for a fully artificial mission, the Voyagers themselves are conservatively estimated to survive in their structural if not functional form for at least one billion years in interstellar space.

  • GaryChurch October 29, 2012, 13:25

    “Your alien invasion scenario invites the question as to why they should observe Earth for periods on the order of hundreds of millions of years, but do nothing until they pick up weak artificial radio signals.”

    Hundreds of millions of years? Any technological civilization that has existed for hundreds of millions of years will not be within our ability to comprehend. Your scenario invites the question as to why you think you can.

  • GaryChurch October 29, 2012, 13:28

    “If you are seriously thinking that alien civilizations would eradicate others, then optimal strategy would be to destroy all possible alien habitable worlds. Meaning that such a civilization would already destroyed life on our Earth eons ago.”

    Your “optimal strategy” is not thinking seriously. What you are saying is that we are here so there is nothing to worry about. Really?

  • Christopher Doll October 29, 2012, 14:44

    When I consider what sentient extraterrestrial life might really be like, I tend towards the Carl Sagan CONTACT model as opposed to Independence Day. Obviously some caution should be taken when reaching out to our interstellar neighbors (whoever they may be), but not the extent of Terran isolationism – which is where I take issue with Hawkings and others who’ve exhibited a surprising level of paranoia on the matter.

    I believe we have more to gain by reaching out as much as possible, to push our culture towards thinking about our existence on a galactic scale. There is admittedly, a curious side-effect to considering the case of the malevolent alien attackers – it’s exactly the sort of topic that gets the public aroused. The bad guys, if they exist, will roll us easily, and we’ve already broadcast our existence in multiple ways (most noted already in previous comments). Perhaps a wider dialog on how to protect ourselves, will make it more imperative to expand our space exploration and colonization efforts.

    But let’s not go with the assumption that any, and all extraterrestrial species are malevolent.

  • NS October 29, 2012, 15:54

    As I’ve said before, it may not matter whether ET is malevolent or not. The mere fact of contact may have consequences that neither it nor we can anticipate. Most New World populations were destroyed by diseases accidentally introduced by the first European visitors, before the conquistadors/settlers/missionaries/whoever with good or bad intentions even met them. Hopefully an advanced ET is well aware of the biological dangers of contact. But who knows if there are other aspects of their technology/culture/whatever that might be unthought of but equally destructive.

  • GaryChurch October 29, 2012, 15:54

    “let’s not go with the assumption that any, and all extraterrestrial species are malevolent.”

    I am not. I am going with the assumption that we are at that point in our history where it is most likely we will destroy ourselves. A civilization that has survived this phase is assumed to be beneficient. Why? Because we like to think of ourselves surviving and being such a race of enlightened star travelers.
    A civilization could just as easily be not especially advanced technologically and looking for a new home or to expand. They detect signals from a planet like ours and decide that this is their chance.
    They know they will most likely survive if they destroy what is here as much as possible and replace it with their own native ecosystem.
    They send an advance force to ethnically and biologically cleanse their target centuries ahead of their colonists.
    It is not malevolence, it is simply natural selection.

  • GaryChurch October 29, 2012, 16:05

    “I have always liked Orion primarily because it has a method of propulsion that exists now in reality. Even sustained fusion is having problems becoming a reality-”

    I am of the opinion the only two places fusion will ever work as advertised is in a star or a bomb. Bombs work quite well.

  • Eniac October 29, 2012, 20:35

    Carl Sagan once estimated that if there were one million technological civilizations in the galaxy, then the nearest one should be about 200 light years from Earth on average. So obviously such an ETI would have to wait another century or so to be able to detect humanity in this manner.

    This is assuming that not one of the one million decides to spread outwards from their world of origin, as we one day hope to. If only one of them had done so, they would have encountered and dealt with all the others and be surrounding us from all sides, with no satisfying explanation for why they have held off our system for billions of years.

  • Wojciech October 29, 2012, 20:39

    “”NS October 29, 2012 at 15:54

    As I’ve said before, it may not matter whether ET is malevolent or not. The mere fact of contact may have consequences that neither it nor we can anticipate.”
    Spot on. That and the time and distance involved is probably the best explanation of no contact.

    “GaryChurch
    A civilization could just as easily be not especially advanced technologically and looking for a new home or to expand. They detect signals from a planet like ours and decide that this is their chance.”
    We won’t be able to live on any other biosphere unless we change either ourselves or the planet in question. And if a civilization has such technological know how, it no longer needs to take other planets with other biospheres.
    Also Earth has been sending signals for billions of years, humanity since thousands. If they are there and can go here, they would already be here if they wanted.

  • ljk October 30, 2012, 9:11

    In 2010 I wrote a two-part article on Centauri Dreams about why an alien invasion is unlikely, but that if it did happen we probably would not stand a chance of emerging from the rubble.

    Part One:

    https://centauri-dreams.org/?p=14703

    Part Two:

    https://centauri-dreams.org/?p=14754

    I just figured it was easier to point folks to these pieces rather than reiterate what I had already said.

  • GaryChurch October 30, 2012, 12:21

    “We won’t be able to live on any other biosphere unless we change either ourselves or the planet in question. And if a civilization has such technological know how, it no longer needs to take other planets with other biospheres.”

    Incinerate the surface and bombard the oceans by deflecting asteroids and comets and you kill the megafauna and a good deal of everything else. Then you seed your own micro organisms, plants, and invasive species. Centuries later the colonists arrive.
    That kind of “technological know how” does not remove the need for a goldilocks planet.

  • ljk October 31, 2012, 10:13

    Eniac said on October 29, 2012 at 20:35:

    “[LJK] Carl Sagan once estimated that if there were one million technological civilizations in the galaxy, then the nearest one should be about 200 light years from Earth on average. So obviously such an ETI would have to wait another century or so to be able to detect humanity in this manner.”

    “This is assuming that not one of the one million decides to spread outwards from their world of origin, as we one day hope to. If only one of them had done so, they would have encountered and dealt with all the others and be surrounding us from all sides, with no satisfying explanation for why they have held off our system for billions of years.”

    LJK replies:

    You and others say it only takes one intelligent species to spread across the galaxy. Well what if such a task is too much for any one species? If ETI share more essential traits in common with humanity than we may realize, colonizing the Milky Way in such a manner that even we might pick up on it could be quite difficult if not impossible to sustain over many millions of years.

    In addition to the time and effort it would take to establish a colony in an alien solar system and then move on to the next (remember you have 400 billion star systems to cover and not all of them are going to meet the requirements for your alien colonists), we also have to consider whether the ETI will have any recognition or desire to even explore space let alone colonize it, then if they do start settling space, will they have the self-ability and/or support from the home world to keep it going?

    Maybe there are species which can be so consistent across millions of years and millions of systems, but honestly I cannot see humanity in its current state doing such a thing. We dropped Apollo after a few years and NASA at least won’t be sending any astronauts anywhere above LEO for decades more.

    As for finding their remains if any, if they arrived millions of years ago, what would be left of their presence for any archaeologist to find? And please don’t tell me any professional archaeologist would be willing to risk their career by announcing to their peers and the general public that they found an alien artifact. Eric von Daniken took care of that scenario for ages to come.

    So in summation, I think expecting one species to cover the galaxy in and for millions of years or more is probably pushing the envelope for just about any species, especially an organic one. Like humanity on a daily basis for generations, most of the members of our species are quite focused on themselves and their one little planet or wherever else they might dwell.

    This is why starships and space exploration in general is so underfunded and still looked upon as fiction by the majority of society. Could that be the case with most other organic species throughout the Milky Way and beyond?

  • Nicolas Uribe October 31, 2012, 21:28

    So many comments regarding cryogenics, long space voyages and propulsion systems. Such mundane concerns will soon be irrelevant. How long before we are able to achieve immortality by scanning our brains and uploading our minds onto computers? Maybe 500 years? Or maybe a lot sooner. At that point, we can live forever in a “second life” website of our own design. But even then, while living in a cyber paradise, we might still be curious as to what’s out there in the rest of the galaxy. No problem – just send out robot missions in all directions. So they’ll take millions of years to cover the galaxy – no problem when you’re immortal. And once they find something interesting, they can radio back their findings. Should we wish to visit (what on earth for??) we can have ourselves sent by radio waves, to inhabit the hard drive of the receiver at the other end. After all, what are we but a long string of 0’s and 1’s????

  • Rob Henry November 1, 2012, 7:13

    Do my eyes deceive me or did ljk really write “[Eniac] and others say it only takes one intelligent species to spread across the galaxy. Well what if such a task is too much for any one species?”

    And I am puzzled as to how anyone could think this, other than in a momentary lapse. To make logical sense of this we would have to use something akin to racial memory, and make it universal, somewhat along the following lines…

    A group of us mentioned starting another colony, but as we started thinking along these lines the racial memory of previous waves of colonisation flooded our minds to such an extent that we had to change topics.

  • ljk November 1, 2012, 9:43

    Rob Henry said on November 1, 2012 at 7:13:

    “Do my eyes deceive me or did ljk really write “[Eniac] and others say it only takes one intelligent species to spread across the galaxy. Well what if such a task is too much for any one species?”

    “And I am puzzled as to how anyone could think this, other than in a momentary lapse. To make logical sense of this we would have to use something akin to racial memory, and make it universal, somewhat along the following lines…”

    Yes I did say that. Is there a problem here?

    Does anyone here think that colonizing an entire galaxy like the Milky Way will be a piece of cake, especially for an organic species like humanity? Have visions of another Star Wars film courtesy of Disney and their $4.05 billion buyout got people thinking again that creating an interstellar empire is just around the corner?

    I can see a species colonizing parts of a galaxy, even keeping things running for a long time. But an entire stellar island of hundreds of billions of stars for millions of years? Maybe an Artilect species could do this, but I am trying to stick with what we know and that one data point is us.

    I can see people bringing up the idea of numerous ETI cooperating and working together to form some kind of galactic federation or empire, but since we have no knowledge of any other intelligences beyond Earth and have no idea if they would ever actually cooperate with each other or even be able to relate and understand one another, I am not going to count on this scenario.

    I am also not going to fall into the easy trap of saying that some day our descendants or some visiting aliens will figure out how to do FTL propulsion or that a cosmic wormhole transport network will suddenly be available to us. It may make me look too conservative in the long run, but if we are having trouble coming up with STL interstellar drives that can get us to Alpha Centauri in under one century, invoking FTL capabilities without any real substance behind them is more than useless.

    If you differ on this and have examples, please share them with us. I have no problem being enlightened.

  • Rob Henry November 1, 2012, 17:44

    Larry, thinking of a species as if it were an individual is a such a wonderful poetic devise that you may be forgiven for retaining that mistake during your initial brainstorming. As we go further to the analysing phase we reach problems, the biggest of which is the more star colonies (humanity) has the higher its potential for forming more colonies. To prevent this, you are in need of a realistic devise that for the phase that we have N colonies makes each colony less that 1/N times as likely to create a new one over the next given time period.

    Even worse, it seems that you think that we might get to the phase of several thousand colonies before our motive peters, so it seems that you believe that this factor can effect the mindset towards colonisation of each and every colony by several orders of magnitude.

  • GaryChurch November 1, 2012, 18:06

    “-invoking FTL capabilities without any real substance behind them is more than useless.”

    I despise FTL as a really crummy trick on the part of sci-fi writers and the entertainment industry to get us to think inside the box. Except it is not really thinking- it is fantasizing. It follows that oft-repeated line alluding to space being an ocean. It’s not. It has nothing in common with an ocean and fools people into applying terrestrial scale to something……..larger.

    The same with time travel- what a waste of special effects. I will not watch a time travel movie. It is an insult to the human intelligence. But that is backwards time travel- forward in time is just going close to the speed of light (but not faster- that’s impossible).

    Freeze and revive technology and H-bombs are all we need for star travel. The first we are neglecting to research and the second we keep for destroying each other. Are we really intelligent beings?

  • Eniac November 2, 2012, 0:36

    @LJK: You are making your usual three mistakes:

    1) You overlook the fact that colonization is local, i.e. both the effort and the motivation take place in a single star system. Collaboration with others (which are way too far away, anyway) or, God forbid, the Mother World, is neither necessary nor possible. Nor does the size of the effort or the need for motivation depend on the number of worlds that have previously been colonized, except for an accumulation of history, which almost certainly favors further colonization after the first few successful attempts. It simply becomes easier if you know that and how your ancestors managed to do it.

    2) You keep citing the unlikelihood of remains to be found or recognized, without specifying why a civilization would have to vanish in the first place. In our experience, life holds on for billions of years wherever it takes root, and that would be no different for life that was spread by galactic colonization. So, we would not have to rely on “remains”. We would expect to find thriving civilizations, everywhere. Even if systems mysteriously reverted to non-civilization, by whatever means, that would simply make them inviting targets for recolonization by any one of their many neighbors.

    3) You say that our (or any) system might not be “suitable” for colonization. While this is the most sensible of the three assertions, it does not really square with the expectation that any colonizers will have learned to live away from planets using asteroidal resources and sunlight alone, well before they go and head to the stars. It will be the rare star system that does not provide these two things to make it suitable. And, in the interior, away from the frontier, unsettled systems will quickly be too few to be picky about them.

  • Wojciech November 2, 2012, 18:01

    Eniac-no civilization that will be able to colonize galaxy, will have the need to do so, as its technological level automatically makes need for “lebensraum” obsolete.
    You are also not taking into consideration possibility as good as any other-that the first civilization that existed is conservative and actively prohibiting contact or colonization.

    Anyway-the need for colonization is in the past, even our civilization no longer seeks colonies, and in fact our settlements have often retreated from fertile islands like in New Zealand islands. The trend is to centralize and conserve, not to expand.

  • Eniac November 3, 2012, 13:09

    Wojciech:

    Eniac-no civilization that will be able to colonize galaxy, will have the need to do so, as its technological level automatically makes need for “lebensraum” obsolete.

    Colonization was never about Lebensraum, it is about getting away from the Powers That Be. I don’t see that ever becoming obsolete, but you are welcome to disagree.

    You are also not taking into consideration possibility as good as any other-that the first civilization that existed is conservative and actively prohibiting contact or colonization.

    I have often said that I believe the first to spread will prohibit contact or colonization by others. The very existence of others, in fact. However, by then it will be too late, because those first will already be everywhere. How else would they have the power to stop others?

    Anyway-the need for colonization is in the past, even our civilization no longer seeks colonies, and in fact our settlements have often retreated from fertile islands like in New Zealand islands. The trend is to centralize and conserve, not to expand.

    This is an interesting hypothesis, but I do not subscribe to it, and I do not see the evidence. Settlements in Antarctica and the ISS are evidence to the contrary. So is the recent widespread fighting in Asia about tiny islands nobody ever cared for before, and the rapidly increasing use of the oceans for resource development.

    In my opinion, it is not the need for colonization that is in the past, but the opportunity. The Earth is filled, and it will be a long time until we have the capability to do the same for the galaxy. I am optimistic that we will acquire that capability one day, and after that it will be simply a matter of time. Of which there will be plenty.

  • ljk November 5, 2012, 1:17

    November 04, 2012

    “Biological Intelligence is a Fleeting Phase in the Evolution of the Universe” (Weekend Feature)

    During an epoch of dramatic climate change 200,000 years ago, Homo sapiens (modern humans) evolved in Africa. Several leading scientists are asking: Is the human species entering a new evolutionary, post-biological inflection point?

    Paul Davies, a British-born theoretical physicist, cosmologist, astrobiologist and Director of the Beyond Center for Fundamental Concepts in Science and Co-Director of the Cosmology Initiative at Arizona State University, says in his new book The Eerie Silence that any aliens exploring the universe will be AI-empowered machines. Not only are machines better able to endure extended exposure to the conditions of space, but they have the potential to develop intelligence far beyond the capacity of the human brain.

    “I think it very likely – in fact inevitable – that biological intelligence is only a transitory phenomenon, a fleeting phase in the evolution of the universe,” Davies writes. “If we ever encounter extraterrestrial intelligence, I believe it is overwhelmingly likely to be post-biological in nature.”

    In the current search for advanced extraterrestrial life SETI experts say the odds favor detecting alien AI rather than biological life because the time between aliens developing radio technology and artificial intelligence would be brief.

    “If we build a machine with the intellectual capability of one human, then within 5 years, its successor is more intelligent than all humanity combined,” says Seth Shostak, SETI chief astronomer. “Once any society invents the technology that could put them in touch with the cosmos, they are at most only a few hundred years away from changing their own paradigm of sentience to artificial intelligence,” he says.

    ET machines would be infinitely more intelligent and durable than the biological intelligence that created them. Intelligent machines would be immortal, and would not need to exist in the carbon-friendly “Goldilocks Zones” current SETI searches focus on. An AI could self-direct its own evolution, each “upgrade” would be created with the sum total of its predecessor’s knowledge preloaded.

    “I think we could spend at least a few percent of our time… looking in the directions that are maybe not the most attractive in terms of biological intelligence but maybe where sentient machines are hanging out.” Shostak thinks SETI ought to consider expanding its search to the energy- and matter-rich neighborhoods of hot stars, black holes and neutron stars.

    Full article here:

    http://www.dailygalaxy.com/my_weblog/2012/11/the-human-species-is-at-an-evolutionary-inflection-point-weekend-feature.html

  • ljk November 5, 2012, 10:38

    Rob Henry said on November 1, 2012 at 17:44:

    “Larry, thinking of a species as if it were an individual is a such a wonderful poetic devise that you may be forgiven for retaining that mistake during your initial brainstorming.”

    LJK replies:

    Oh, I think the human species is more of an individual entity than most people either realize or want to accept. The vast majority of human societies act like a body, with a centralized area for gathering information and issuing orders, organs for gathering fuel to run the society/body and a waste management system to discard of the waste. You get the picture. Think of the animated film Osmosis Jones for even more analogies.

    Just like a body, while the parts may seem different, they all have to work together or else the whole system eventually fails. And the whole purpose of most of these parts is to keep the system functioning and pass on its genetic plans to stay alive in one form or another. There is no real room or toleration for individuality within the system, despite grandiose claims to the contrary. Though it is often hoped, there is no guarantee that the copy or copies of the body/society that carry on from the parent system will be like the original, especially if they enbd up dwelling in new locations and are affected by these alien environments accordingly.

    This past weekend I heard a story on NPR about a guy who lived in a small Sothern town who was secretly a Democrat and kept this knowledge from the rest of the overtly Republican/Liberatian community for fear of how they might react to his true views. Yet it is claimed in the United States of America that every individual may act and think as they please so long as they are not willfully harming others. This is guaranteed by our Constitution and other legal documents. Yet in reality, from the schoolyard to businesses to government, and especially in small communities, standing out as an individual from the rest of the group is often detrimental to that individual, despite noble claims to the contrary. The society/body sees people/cells which start acting independently of what they are expected to be as a cancer and treated accordingly, either through direct actions or more subtle methods which fly under the radar but still achieve the same purpose. We are really still very small tribal in nature, but we get distracted by this fact from all our shiny new toys that seem oh so sophisticated.

    So, yes, I do see humanity as an individual and now you know my reasons why. Whether you agree with them or not is up to you. It will not be up to me, a virtual cell, but the entire body/society which ultimately decides whether or not your viewpoint will work for the whole.

    Rob Henry then said:

    “Even worse, it seems that you think that we might get to the phase of several thousand colonies before our motive peters, so it seems that you believe that this factor can effect the mindset towards colonisation of each and every colony by several orders of magnitude.”

    LJK replies:

    Please note I do not want to see space colonization fail, especially since I think it is what will save our current species from stagnation and extinction. I am merely working with our one data point, which shows that even mighty civilizations going back thousands of years have ultimately either failed or just faded into something far less than mighty for a number of factors. These include not thinking far enough ahead or grasping the reality that there is much, much more to reality than the one pale blue dot we have occupied for the vast majority of our existence.

    I don’t think human nature is suddenly going to change just because we start occupying other worlds or giant habitats in space, unless humans themselves are radically changed via technology or bioengineering. Then we will become a different species of humanity and how they will behave depends on the modifications and their purposes.

    If our children remain essentially the same over the next few centuries or more, the only big difference I predict with a space colony over an Earthly empire is that if the former fails, extinction will be more likely and not long in coming.

    Assuming that most ETI will have started out as organic beings (I am skipping over creatures evolved from silicon or born as plasma inside a sun for the moment, for sanity’s sake), they too will go through a number of stages in their biological and social evolution, including making fatal mistakes along the way which hopefully for them do not bring down the entire species.

    So while it is only logical to agree that the more colonies the better chances of survival and spreading out across the galaxy, that presumed fact that the beings conducting these enterprises will be imperfect mean that unless they can somehow muster the resources and will to send out many colonies at once, the chances are that time and events will see colonies fail, especially as they get further apart from each other in what is after all a very big galaxy. And I am also not presuming that everyone will have access to FTL drives or a conveniently located cosmic wormhole.

  • Rob Henry November 6, 2012, 19:14

    Ljk, I continue having difficulty in fitting your points into any model that retains both coherence and some semblance of analytic value.

    I am not an American, but I imagine that being a Democrat is not seen as being repugnantly immoral anywhere, so your example is that of the high desire to retain individuality even when the need to fit in place as part of a functioning community is extreme. When the separation is light years, individuality must win out by default, irrespective of the desire.

    Actually we can go much further than this. Let’s assume the every species of ETI without exception is composed of individuals who act as automatons and that the advances necessary for their civilisation to become technological derive only from intelligence displayed in some sort of collective association. You may believe that your qualitative argument has some purchase then. Not so.

    Even in such a limited case we run in to the difficulty that we would have no reason to believe that the natural selection by which these bizarre coherences evolved worked when such large time delays are involved, and even less to believe that in every case where colonisation mode was switched on it would later just switch itself off.

    Try this exercise: fit your argument into any toy model of a class of colonising expansions you can. I think that you will also be drawn to the conclusion that your current line of argument is nonsensical.

  • Eniac November 7, 2012, 1:44

    @LJK:

    Oh, I think the human species is more of an individual entity than most people either realize or want to accept. The vast majority of human societies act like a body, with a centralized area for gathering information and issuing orders, organs for gathering fuel to run the society/body and a waste management system to discard of the waste. You get the picture. Think of the animated film Osmosis Jones for even more analogies.

    This may be so on Earth, where we can instantly communicate around the globe. There is no chance that this model can be extended over interstellar distances. We will be dealing with many independent civilizations, at least one per star system. Thus, once colonization starts, there is no way for it to stop until it runs out of “fuel”, i.e. unsettled star systems.