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All Quiet Around Gliese 581

When you’re looking for signs of an extraterrestrial civilization, you can take two basic approaches. Think back to Frank Drake’s initial SETI experiment at Green Bank in 1960, when because of limited resources and time he chose specific targets: Epsilon Eridani and Tau Ceti. The choice made sense at the time because both were nearby stars and SETI, fresh off the classic paper “Searching for Interstellar Communications” by Philip Morrison and Giuseppe Cocconi, was just beginning to define a methodology. Drake studied his targets near the 1.420 GHz frequency — the 21 centimeter hydrogen line — that the authors had suggested.

Of course, sky surveys are also possible, of which SETI@home may be the most widely known. Here the idea is to make no assumptions whatever about the location of a SETI signal and observe the entire sky. SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is an attempt, for example, to analyze radio telescope data obtained while astronomers are using the telescope for other purposes. The SERENDIP V.v spectrometer installed at Arecibo in 2009 is the most recently deployed instrument involved in this strategy.

The Closest Habitable World?

We’ve been considering the possibilities growing out of the Square Kilometer Array for SETI purposes, prompting a number of readers, Adam Crowl being the first, to send along a new paper on using Very Long Baseline Interferometry in a targeted SETI search. Hayden Rampadarath and colleagues at the International Centre for Radio Astronomy Research (Perth, Australia) intend the paper to be a foundational document for the use of VLBI in future SETI projects including those at the SKA. The results show great promise for the technique.

With VLBI, combining signals from multiple telescopes allows us to emulate a single instrument the size of the maximum separation between the telescopes, which could be hundreds to thousands of kilometers. Interestingly, there has been little application of VLBI techniques in SETI, although the SETI-Italia project using the VLBI Medicina telescope is active and the SETI Institute has been studying interferometric techniques at frequencies between 1200 and 1750 MHz. What Rampadarath and colleagues have done is to target the widely studied red dwarf Gliese 581, using observations at 1230-1544 MHz made with the Australian Long Baseline Array, which includes three radio telescopes spaced widely in New South Wales.

Image: The Mt. Pleasant radio telescope. southernmost dish used in Australia’s Long Baseline Array. Credit: Wikimedia Commons.

It’s a good choice of target because Gliese 581 is a multi-planet system with at least one planet that looks to be on the edge of the habitable zone. With Kepler’s investigations of thousands of planetary candidates ongoing, we’re beginning to pick out high-value targets like this, defined as planets where liquid water could exist on the surface and life might arise. Gl 581 is not one of the Kepler worlds, but it does present us in the form of Gl581d with a super-Earth with an orbital period of 83 days that according to at least one recent study may offer habitable conditions. The existence of another possible habitable zone planet, Gl581g, now appears unlikely.

VLBI and Its Benefits

The Perth team observed Gl581 for eight hours using the stations of the Long Baseline Array. The result: 200 narrow-band and 22 broadband candidate signals were examined, most or all of which are thought to have been caused by Australian space to Earth geostationary satellites. No evidence for signals from the region of Gl581 emerges. The result is hardly a surprise, but the good news is that this pilot study demonstrates that Very Long Baseline Interferometry makes what the authors call ‘an ideal technique for targeted SETI.’ It also shows us how to proceed:

Since this was a proof-of-concept observation, two differences between this experiment and a typical VLBI observation should be noted. Firstly the baseline lengths in this experiment were short by VLBI standards. Baselines one or even two orders of magnitude longer would significantly reduce the amount of correlated RFI [radio frequency interference].

That’s helpful indeed. Affecting this study were the Australian Optus’ Mobilesat and the INMARSAT geostationary satellite systems, which operate in a range between 1525-1559 MHz, a close match with the candidate signals detected in the observation run. Longer baselines should reduce such problems because they widen the distance between the source of interference and different parts of the array. But there’s more:

Secondly, most VLBI observations are carried out using more than three telescopes. Increasing the number of baselines to four or more constrains both the phase and amplitude closure relations, drastically increasing the quality of calibration. This would also provide the opportunity for image plane searching. However, it would likely be computationally expensive as a technique for searching over very wide frequency ranges. Relaxing the single baseline five times median limit could enhance the sensitivity beyond that of the weakest baseline.

VLBI allows us to search for SETI signals over a wide range of frequencies and with high sensitivity. But there’s also this: The VLBI technology is moving from older data recording systems to real-time network connections, which means these techniques will become available for quick follow-ups on transient radio sources. Thus the detection of a possible SETI signal with VLBI techniques becomes possible. Gliese 581 thus stands in relation to VLBI techniques the same way Epsilon Eridani and Tau Ceti stood to early radio SETI, an initial target that began a series of systematic experiments that the Square Kilometer Array will continue.

What we can conclusively say about Gl581 at this point is that, during the time of observation, no powerful radio signals were beamed at us. I like what co-author Steven Tingay (Curtin University) told ABC Science in a recent story: “We would have seen a signal brighter than 7 megawatts per hertz, but that is a pretty strong signal. Who knows, maybe it was a public holiday on that planet or something and we missed out.” Hope reigns eternal…

The paper is Rampadarath et al., “The First Very Long Baseline Interferometric SETI Experiment,” accepted for publication in The Astronomical Journal (preprint).


Comments on this entry are closed.

  • Gerry June 1, 2012, 15:38

    Hi, long time reader here…I posed this question in an older thread where it probably won’t be seen, but it’s relevant here, too. Briefly, even if interstellar travel is very difficult and therefore rare, it seems possible that interplanetary travel might be relatively less so. If a civilization was employing Daedalus-style pulse-propulsion, or some other high-energy method, to move about their solar system, might this create a signal detectable by us, using some of these new arrays? There are a lot of assumptions behind the question, sure, but this could conceivably be another source of radiation-leakage with an artificial signature. Ditto with atomic detonations from other sources, perhaps used to move or mine asteroids…

  • Ron S June 1, 2012, 16:52

    “VLBI allows us to search for SETI signals over a wide range of frequencies and with high sensitivity.”

    This is a bit misleading in the article. The application here is not interferometry, but rather achieving an increased SNR and the reduction of false positives (as noted in one of the quotes) through the use of multiple antennas and having them widely separated, respectively. So, they’re using a VLBI system for a non-VLBI application. I’m also not sure how the frequency range enters into this, which is more a function of antenna electronics and reflector area and curvature accuracy.

  • ljk June 1, 2012, 17:37

    If an ETI has colonies in their solar system, they may have to use radar to track all planetoids, meteoroids, and other celestial debris. Just as on Earth when we use Arecibo to ping a passing planetoid or the military uses their powerful radar to detect enemy objects, those would be fairly strong, if random, signals into the galaxy.

    Regarding the radio scan of the Gliese 581 system, maybe the residents there are using lasers for interstellar communication instead:


  • d.m.falk June 1, 2012, 19:22

    Because of the age of the Gliese 581 system, (Something like 6-7Gy), I think this, if any civilisation has been there at all, it’s now probably post-civilisational, with the then-dominant species in some post-evolutionary/de-evolutionary phase, if that species has survived, if anyone has been there. The fortunate part is if life is there at all, it may have gone and will go through several cycles of advanced (technology-capable) species over the course of this system’s incredibly long lifetime.


  • Interstellar Bill June 1, 2012, 21:52

    If there’s a radio-powerful civilization close enough to talk to, then there must be billions in the Galaxy. And every last one of them stayed home in a stasis of population and technological-development? No Type-II systems bursting out to take over every nearby star? Not even one?

    Hearing sentient signals from so close would indeed be extremely unsettling, unbearably amplifying the Fermi Paradox.

  • John A. Karr June 2, 2012, 11:18

    Such a hit and miss proposition, trying to find evidence of life via signal frequencies. The enormity of distance and the timing of some other civilization’s technological capabilities boggles the mind. Still, it is important to try.

    If donations to SETI and VBLI are not tax deductible, they should be. Anything to help further our efforts into space-related matters advances our civilization.

    And since propulsion was mentioned … advances in nuclear propulsion seems to be the only viable way we’re going to move on the next level in manned space missions. That, and using the moon as a base to build spacecraft and LARGE Space Stations with their own propulsion systems.

    One can dream.

  • VL Teofilo June 2, 2012, 13:38

    Paul- you discussed this 2 yrs ago[https://centauri-dreams.org/?p=5868]. Did you ever do the analysis of the probability of receiving an RF ETI signal based upon Maccone’s ETI spacing ~1340 ly [http://uavarese.altervista.org/0_Statistical_Drake_Equation.pdf] ?
    Horvat has done such a calc and the probability for searching for 500 yrs is < 0.01 [http://arxiv.org/abs/0707.0011 ] .

  • stef June 2, 2012, 13:38

    what if there is life… but they are in the middle age… or in the prehistoric step…

  • Paul Gilster June 2, 2012, 13:44

    VL Teofilo writes:

    VL Teofilo June 2, 2012 at 13:38 [edit]
    Paul- you discussed this 2 yrs ago[https://centauri-dreams.org/?p=5868]. Did you ever do the analysis of the probability of receiving an RF ETI signal based upon Maccone’s ETI spacing ~1340 ly [http://uavarese.altervista.org/0_Statistical_Drake_Equation.pdf] ?

    Haven’t done this but I’m sure Dr. Maccone has worked it out. I’ll ask him next time we talk. Thanks for the link re Horvat, too.

  • ljk June 2, 2012, 14:27

    Interstellar Bill said on June 1, 2012 at 21:52:

    “Hearing sentient signals from so close would indeed be extremely unsettling, unbearably amplifying the Fermi Paradox.”

    Why would discovering ETI be unsettling, from any distance?

    Then stef said on June 2, 2012 at 13:38:

    “what if there is life… but they are in the middle age… or in the prehistoric step…”

    Why do we assume that ALIEN beings will evolve and develop culturally just like us? Especially if they evolved in a very different environment from us.

    This is one reason why SETI has not found anyone yet, because we keep assuming they will be like the aliens we find on Star Trek – basically humanoids with a few odd features.

    And who knows, maybe the ETI keep looking for beings who look and act like themselves and thereby missing creatures like us.

  • ljk June 2, 2012, 14:34


    SETI’s search for alien life is in trouble

    By Tom Foremski | May 31, 2012, 3:43pm PDT

    Summary: SETI might be forced to sharply curtail its search for alien life if it can’t plug large losses in funding.

    Jill Tarter ponders the uncertain future for Alien search project SETI.

    Wednesday evening I was at a great local salon organized by Taylor Milsal and Christine Mason McCaull, which featured guest speaker Jill Tarter, Director of the Center for SETI Research for 35 years.

    Last week, Ms Tarter announced her retirement from SETI, but that was not by choice. She resigned so that SETI could continue with its work amidst big cuts that threaten to shutter the project. Her former salary will be used for operations while she tries to raise funds large enough to plug large losses in funding due to the state of California’s budget cuts, and from other sources.

    She gave a great talk and I spoke with her afterwards. Here are some of my notes:

    – SETI needs about $2 million a year to keep going. She resigned so that her salary would not be a drain on the organization.

    – The search for intelligent life in the universe is entering an exciting era where advances in the technology of telescopes, and in the analysis of massive amounts of data, mean that more of the sky can be searched for alien signals, than ever before. But, we are still very far from any form of comprehensive search. We have only examined the equivalent of a glass of water pulled from the earth’s oceans.

    – SETI introduced the first distributed computing network when volunteers agreed to let SETI crunch data during the bits of time they weren’t directly using their computers, SETI software took advantage of the idle cycles in a PC’s microprocessor, the basis for peer-to-peer computing architectures that are now very common in many applications.

    – There are army of SETI volunteers look for patterns in data in a massive “crowd sourcing” project that takes advantage of the brain’s “spare cycles.”

    – She spoke about the advanced telescopes that are so sensitive they can detect the passage of planets as they cross in front of distant suns, which has led to the discovery of 69 planets, and an additional possible 2321 solar systems. She estimates that there could be as many as half-a-billion habitable planets in our galaxy alone.

    – If there are advanced extraterrestrial civilizations discovered they will have to be in existence for a reasonably long time, for us to detect them. That would be a very good sign that a technological society, such as ours, is able to survive its challenges.

    – The job is difficult because the search is for “leakage” of electromagnetic signals, which would be very low power and are focused on tiny spaces, within a vast universe. Our own signal leakage is small, the largest Earth signal that could be seen by alien civilizations, would be a radar telescope in Puerto Rico, which uses a very powerful beam that can reach deep into the universe, but you would have to be directly in the path of that beam.

    – Ms Tarter announced her retirement on May 22, but she isn’t giving up her work, just her salary. Her goal is to stabilize SETI funding for the next five years at about $2m a year, which would pay operating costs for the telescopes, and for a handful of researchers.

    – By joining SETI and taking part in the hunt for alien life, Ms Tarter believes we will learn what it is to be “Earthlings” and that realization has the potential to make a big difference in the world, uniting us and trivializing any differences between peoples.

    Foremski’s Take: I was shocked to hear how California State’s budget cuts, loss of funding in other areas, and the lack of NASA support, has endangered the 50 year history of searching for extraterrestrial life. A $2 million a year budget is tiny — it’s something that a Google, Intel, or an IBM could easily fund, and hundreds of other companies could, too.

    SETI’s funders would gain a lot of goodwill, especially in engineering circles — the production line workers who are making our future.

    Recruiting the best engineers requires more than a good paycheck, or free lunches. These days it’s the organizations that spark the imagination, that show a desire to dream big, and to tackle some of the most difficult challenges around, that win in the jobs market. There’s few larger challenges than discovering the signals of alien civilizations. (Alien Life…brought to you by YourNameHere Corp.)

    The search for alien life is embedded deep within our culture, it has inspired many generations with countless stories, books, and movies. It would be a tragedy if SETI were to cease its work, especially with such modest needs.

    – Come on $GOOG, you are using the NASA airfields for your luxury jets, and you are interested in space exploration, plus the Google Foundation is sitting on cash — kick in some dollars for SETI!

    There are tremendous opportunities for marketing slogans. Here are a few I came up with (send me yours via Twitter @tomforemski.)

    “Google Search knows no limits.” or “SETI Search – powered by Google.”

    – And here’s one for Intel:

    “From bunny suits to space suits – wherever you find Intelligent Life you’ll find Intel.”

    – Here’s one for Facebook:

    “If there are alien civilizations out there, we’ll be the first to find them, friend them, and let them use our phone.”

    (’ll post more slogans later…)

    – – –

    Also: SETI’s conference is coming up on June 22-24 in Santa Clara.

    Ms Tarter will be celebrated at a gala event on Saturday evening, June 23. Speakers include astronaut Mae Jemison, astronomer and “Drake Equation” author Frank Drake, and “Star Trek” actor Robert Picardo.

    A message from Ms. Tarter:

    SETI research experiments are funded by private donations, limiting how quickly we can search these newly discovered planets for intelligent life.

    The best reason to support SETI research is because it is an investment in our own future. The scientist Phil Morrison said that ‘SETI is the archeology of the future.’ Think about it. If we detect a signal, we could learn about THEIR past (because of the time their signal took to reach us) and the possibility of OUR future.

    Successful detection means that, on average, technologies last for a long time. That’s the only way another technological civilization can overlap with us in time and space. Understanding that it is possible to find solutions to our terrestrial problems and to become a very old civilization, because someone else has managed to do just that, is hugely important!

    Knowing that there can be a future may motivate us to achieve it.

    There’s additional information here and an opportunity to make a donation: SETI Institute

    Become a member of TeamSETI for $50.

  • Ole Burde June 2, 2012, 14:47

    Sucses is often a matter of staying focussed on the path of least resistance , and letting it take you whereever it wants to go . If we want to find life outside the solar system , or to find a clear indication that no such life exiets in the galactic nabourhood , the path of least resistance does not seem to be at radiowave frequency . The path of least resistance must involve carefull planning of how to build on the sucses of the Kepler telescope , not in order to do a little bit more of the same , but in order to make the the next step in that direction a breakthrough in new capability .
    A thousand good explanations has been made , why no ETI radiosignals has been detected . Even if they were all true , none of them would prevent us from detecting the chemical signatures of bacterial life inside the same galactic nabourhood .
    Exept for one single case : the case where no life exists .

  • Stan June 3, 2012, 16:31

    I expect you’ve seed this: Mars-One colony announcement.


  • Rob Henry June 3, 2012, 19:22

    Ron S comment looks correct but started me thinking. Perhaps one of the most diagnostic feature of an ETI signal is that it is emitted from and area that still resolves as a point at very high resolution. Its implied power per area must be fantastic compared to natural and unfocused sources. Could it be that VLBI is needed to show this??

  • Astronist June 3, 2012, 20:06

    Sorry, but Jill Tarter’s “best reason to support SETI research” is not logical. If “knowing that there can be a future” because someone else has had a future is of decisive influence in motivating a civilisation to survive, then the first civilisation to arise does not have that advantage and so collapses. Not knowing of their prior existence (or even knowing of it), the second civilisation also collapses, and so does every subsequent one. The first civilisation to achieve long-term sustainability does so without being helped by the example of any alien civilisations. One should in any case question the relevance of long-term survival of one industrial species for the survival of another, living in very different circumstances with a very different biological heritage.

    Her argument is based on the assumption that a detection will be made very soon. Change that assumption — a detection will not be made for thousands of years yet — and we are thrown back onto our own resources to sink or swim as best we can. She is entitled to her own view, of course, but my point is that it conflicts with such observational data as we have (a.k.a. the Fermi paradox). It is more reasonable to assume that aliens will not help us out, through the example of their existence, with our problems of development over the next few decades.

    Oxford, UK

  • Ron S June 3, 2012, 22:14

    Rob, it depends on what you are attempting. To detect a signal at all, VLBI is not useful. Most sources both natural and artificial are effectively point sources from our perspective. Further, it adds nothing to achieving the initial detection since the location would be, of course, unknown.

    VLBI might come in handy once a signal is detected to narrow down its location since the beamwidths of radio antennas are generally too broad to isolate the source to, say, one star in the field of view. Even so the resolution possible with VLBI will still leave some doubt, and will certainly not be able to resolve down to an area within a stellar system, such as a known exoplanet, except perhaps for the nearest systems. This can be calculated if you’re interested, but not by me!

  • Mark June 3, 2012, 23:59

    I can’t help thinking that the reason we don’t hear from any ETI using radio or lightwave communication is because they have some advanced physics that makes EM communications laughable at these mind-boggling distances. For example some theories of the universe say that there are actually 10 or 11 dimensions, way beyond the 4 of ordinary spacetime. What if along one of these dimensions, for the sake of argument, say dimension #6, every particle in the universe is occupying the exact same “when” and the exact same “where?” All one needs then to contact or observe any other civilization is a device (let’s call it a 6D radio) to “tune in” to this dimension. This shared dimension could also possibly explain puzzlers like quantum entanglement and ESP.

    Now I have no idea how any of this could come to be, because it’s science beyond our own, but it seems to me that SETI researchers looking for EM signals from ET civilizations is a bit like primitive earth tribes looking for smoke signals from other tribes halfway around the world. In short, they’ll never see those signals because they don’t comprehend the distances involved and how inappropriate their communications scheme is to the task at hand. Now once the primitive tribes are shown the radio, this is beyond smoke signals and there’s a whole lot of communications and broadcasts going on there the whole time, AM, FM, cellular, etc., they just don’t have the science for it yet.

    I bet you there is a ton of interstellar communications going on right now, we just don’t have the right gear to tune in to it.

  • jkittle June 4, 2012, 9:46

    Mark- ‘Smoke signals”… I like that, and I susupect that is the best explanation for Dr Fermi’s delimma.
    But ET might see our ” smoke signals” if they are studying the universe.
    I just went back and looked at the posts over the past few weeks. I conclude (again) that we are for all practical purposes, on our own and we need to build out our solar system for colonization in any case. I just pulled some old walnut boards out of my fathers barn ( stored for 30 years) and am building a desk . For last Christmas I made a table with a nice rough textured ” restoration” finish. 2 inch think solid walnut ( from the same stash).
    One Key theme that runs though much ( but not all) Sci Fi is that we build our own future, for better or worse.
    Now that at least one company can launch materials into orbit it is time to start building . NASA’s well intentioned but lately counter productive monopoly on US space development is ending. Even if you do not want to build rockets, some individuals of personal wealth can buy/build their own space vessels to tour lunar orbit, or lounge in an orbital habitat. Perhaps mars is on the rise as well. For me, I build solid beautifully rough furniture, teach chemistry and design Bacteria with commercially interesting functions. And I follow C.D. , writing notes here and when it suits my fancy , and – sometimes- i even write a bit of doggerel verse . Maybe one of these activities will help prepare mankind for the stars. My New Grandson sure seems ready to try!

  • Raffaele Antonio Tavani June 4, 2012, 11:43

    Le considerazioni che fa “Mark” sono indubbiamente assai sensate, ma la spiegazione di questo “silenzio” potrebbero essere assai più tragiche.

    Cioè che le civiltà tecnologiche, abbiano una durata assai limitata, e non riescano a superare il “collo di bottiglia” rappresentato dall’ecessivo uso delle risorse ambientali dei loro pianeti, finendo i loro giorni, in qualche catastrofe ambientale come quella che si paventa da parte di alcuni scienziati(c’è un articolo in questo senso apparso su “Scientificamerican.com” del 23 Maggio 2012)che toccherà il culmine verso la fine di questo secolo.

    Saluti da Antonio Tavani

    Via Google Translate:

    The considerations that is “Mark” is certainly a very sensible, but the explanation of this “silence” may be far more tragic. Namely, that technological civilizations, have a very limited duration, and fail to overcome the “bottleneck” represented dall’ecessivo use of environmental resources of their planet, ending their days in some environmental catastrophe like that which are likely to emerge from some scientists (in this sense there is an article that appeared in “Scientificamerican.com” of May 23, 2012) that will reach the summit towards the end of this century. Greetings from Antonio Tavani

  • jkittle June 4, 2012, 13:56

    By the way some exciting news on the the NRO-1 telescopes being made available for NASA to use in dark matter/ planetary systems studies. These would be great to look for ET signatures, surveying the cosmos. If you want to have some fun, try searching for information about the NRO-1 telescopes.. Talk about ” dark matter” apparently these things did not exist until the Defense department decided to give them to NASA. Even wikipedia does not have an entry. Google and Bing Searches only turn up the most recent news stories. – well, some things are better kept secret, I suppose. These would be even better than Wfirst ( bigger mirror ), provided they have the infrared capabilities, which I imagine is a real strong capability for them. It would be best if they also have multi-megapixel cameras. ( a weakness of Spitzer). Now, how do we get a 96 inch mirror scope into geosynchronous orbit?

  • VL Teofilo June 4, 2012, 17:39

    Gees guys- simply do the calc. or Ref . Maccone’s paper I cited in my last comment. He calculated ~ 1340 l-yrs between technological civilizations with only about 1000 in our Galaxy. And since we are a middle age star one can assume that 500 of these civilization are more advanced then we are being 1-2 billon years older if still extant. That explains why we don’t hear their radio waves not to mention the hugh average distance between civilized planets. In fact Horvat has done such a calc and the probability detecting an RF signal by searching for 500 yrs is < 0.01 . The simple reason is those 500 more advanced civilization have stopped using RF and those behind us have not developed the use of carrier pigeons . We need to be searching for something we have developed yet, e.g., Mach gravity waves or quantum entangled messages or something we won't imagine for 1 Myrs!

  • Eniac June 4, 2012, 21:12

    Mark- ‘Smoke signals”… I like that, and I susupect that is the best explanation for Dr Fermi’s delimma.

    I like the smoke signal analogy, too, but I am not convinced it explains the Fermi paradox. While indeed those smoke signals would not be seen across the world, they would be seen quite well from neighboring villages, passing airplanes, and even Earth observation satellites. Even if none of those were to draw attention to our signaling tribe, chances are the tribe themselves have already seen airplanes, riverboats, roads, anthropologists, ATV tracks, coke bottles, and Lord knows what other signs that would clue them in they are not alone. Long before the first cell-phone salespeople arrive (drawn by the smoke signals, of course).

    This is the Fermi Paradox: Why are they not around us, in plain sight. Or at least, their infrastructure or their garbage. It has little to do with means of communication, advanced or not. Not distances, either, space or time. It is the lack of presence in the here and now that is hard to explain. Except in two ways: Like them, we are doomed, or else, nobody here but us.

  • Stan June 5, 2012, 0:23

    @Teofilo…. I agree with your idea, except that I think you’re actually being far too conservative in it. You say, “And since we are a middle age star one can assume that 500 of these civilization are more advanced then we are being 1-2 billon years older if still extant.” But actually it’s not the age of the star that’s the determining factor so much as the age of civilization, which is a mere few thousand years. In other words, it’s not half of the 1000 civilizations that are older than us, but nearly all of them, if not all. That few thousand years is an insignificantly small percentage of the possible age of those civilizations that are extant at the present moment.

  • John A. Karr June 5, 2012, 15:35

    Given all of the above shortcomings of radio frequency detection, then searching for KEPLAR Goldilox worlds does seem a better bet. Find worlds with atmospheres somewhat capable of sustaining life as we know it, then some ultra-sensitive carbon / methane searches? THEN target those planets for chemical signatures / plasma / whatever else we can think of ….

    Then there’s the question of Life vs. Advanced Life. A planet might have bacteria, and that would solve one major question, but wouldn’t we need to have some form of mechanical sound from ET to indicate a degree of Advanced Civilization?

  • Rob Henry June 9, 2012, 23:48

    Whoa Eniac. Now you’re going too far the other way in your confidence in the ability of a low L value on its own to answer Fermi. That is still and abysmal attempt at solution, even if we acknowledge the power of the doomsday argument.

    The doomsday argument forces acknowledgement that it is likely that low L civilisations are fantastically more common than those immune from any sort of premature destruction. If we then start loading up galaxies with these we should at least find their Bracewell probes. Indeed, if they are so common as to number 500 per large galaxy, and just one in a million ETI’s have the right characteristics to escape disaster, then one in every 2000 such galaxies should host a stage III civilisation – and that should be conspicuously obvious.

    I do not claim any good solution, but I do claim that the following is better…

    The zoo hypothesis is correct, and most keeper civilisations allow or encourage many new kept civilisations to develop to at least our stage before they arrest them. It would make sense that the psychology that allows zookeeper civilisations also makes them inconspicuous, and, IF abiogenesis is rare, our existence would make more sense in terms of our planet being sown with life by a keeping civilisation that may well represent the only life in the observable universe.

  • ljk June 10, 2012, 11:04


    Why SETI Counts

    by Morris Jones

    Sydney, Australia (SPX) Jun 04, 2012

    The SETI Institute needs support now, more than ever. It’s worth exploring the Web site to see how much is going on, generally out of the mainstream media. It’s more than just a worthy cause. It’s great fun!

    Are we alone in the universe? It’s probably the greatest question posed by space exploration. It fascinates scientists and the general public. It’s important and deeply compelling. We want to know, and we have ways of finding out. It doesn’t cost much to operate a SETI (Search for Extraterrestrial Intelligence) program. Some space missions cost billions of dollars. Most cost hundreds of millions.

    The US-based SETI Institute, by contrast, needs only a couple of million dollars a year to perform its cutting-edge work.

    In tough economic times, it’s more important than ever to get value for money from investments in scientific research. SETI is probably a model of economy. The investment required is minimal, and the issues confronted are profound.

    Although we have yet to find evidence of life beyond Earth, the program has been highly successful. It has carried out its surveys of the galaxy with care and efficiency.

    It has helped us to put the existence of an inhabited Earth into a greater perspective, by showing that our immediate neighbourhood in space seems to be devoid of more advanced civilizations. It has educated and inspired millions of people in the fields of space science.

    It is therefore shocking to see that SETI is starved for funds. Money is wasted on so many pointless and harmless activities, yet this profound quest is struggling to survive. Without a boost in funding, the venerable SETI Institute may be forced to cease its search for new civilizations in the future.

    Because it only requires relatively small amounts of funding, a small contribution to SETI goes a long way. It makes a real difference, and every contributor becomes a stakeholder in this great endeavour.

    Spaceflight enthusiasts who are tired of the lack of progress in larger space programs can break their frustrations by embracing SETI. They can do something themselves.

    They can advance our knowledge of the universe. They will become stakeholders in the search. And when we make the ultimate discovery, they can proudly state that they were a part of it.

    The SETI Institute needs support now, more than ever. It’s worth exploring the Web site to see how much is going on, generally out of the mainstream media. It’s more than just a worthy cause. It’s great fun!

    Dr Morris Jones is an Australian space analyst and writer.

  • andy June 11, 2012, 14:55

    The zoo hypothesis always struck me as fairly ridiculous. One problem is maintaining the radio silence given the limits imposed by the speed of light.

    See also Spatio-temporal Constraints on the Zoo Hypothesis, and the Breakdown of Total Hegemony

  • Eniac June 11, 2012, 22:29

    @andy: I agree with the conclusions, but the paper you cite makes the equally ridiculous assumption of interstellar “hegemonies”. This is absurd, unless faster-than-light communication were allowed. Under the physical laws we know, intergalactic civilization is bound to be a collection of independent stellar civilizations, linked only by a common history and the exchange of non-actionable, stale-by-decades information. No legal contracts, no financial transactions, and no administrative directions could reasonably survive the time lag.

    Make no mistake, though, the settled part of space will grow nonetheless. Just as fast and more surely, as an uncoordinated conglomerate rather than an organized unit.

  • Rob Henry June 12, 2012, 18:59

    Careful here, my commonsense also tells me that the zoo hypothesis is wrong – but it also tells me other lies such as there are fewer even numbers and primes than whole numbers. That paper you cite Andy, assumes that if any *zookeeper regime* was set up it must have been by dint of the hegemony of one or a group of ETI’s, And I would agree that that does not make sense. More likely to me is that it is a side result of a common legislative framework that was set up as the result of protracted earlier conflicts.

    More likely still is that Drake f(l) is so low as to only allow one ETI per galaxy, and others only appear as the result of a seeding by that first (potential keeper) civilisation. That would help with Eniac’s problem of integrating different stellar populations. In this second scenario, keeper-type civilisations might only form from the subgroup of ETI’s that can retain continuity over interstellar distances. We might even have been seeded by a renegade group (who happen to own the Sol system as well as the one the live on), and the others will become furious as our presence gradually announces itself.

  • Eniac June 13, 2012, 0:30

    We might even have been seeded by a renegade group (who happen to own the Sol system as well as the one the live on), and the others will become furious as our presence gradually announces itself.

    Do I hear you postulate petty politics sustained over billions of years? Please….

  • ljk July 20, 2012, 16:22

    Gliese 581g is back as the number one known exoplanet for having the potential to harbor life: