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Why SETI Keeps Looking

How do you feel about a universe that shows no signs of intelligent life? Let’s suppose that we pursue various forms of SETI for the next century or two and at the end of that time, find no evidence whatsoever for extraterrestrial civilizations. Would scientists of that era be disappointed or simply perplexed? Would they, for that matter, keep on looking?

I suspect the latter is the case, not because extraterrestrial civilizations would demonstrate that we’re not alone, but because in matters of great scientific interest, it’s the truth we’re after, not just the results we want to see. In my view, learning that there was no other civilization within our galaxy — at least, not one we can detect — would be a profoundly interesting result. It might imply that life itself is rare, or even more to the point, that any civilizations that do arise are short-lived. This is that tricky term in the Drake equation that refers to the lifespan of a technological civilization, and if that lifetime is short, then our own position is tenuous.

The anomalous light curve in the Kepler data from KIC 8462852 focuses this issue because on the one hand I’m hearing from critics that SETI researchers simply want to see extraterrestrials in their data, and thus misinterpret natural phenomena. An equally vocal group asks why people like me are so keen on looking for natural explanations when the laws of physics do not rule out other civilizations. All I can say is that we need to be dispassionate in the SETI search, looking for interesting signals (or objects) while learning how to distinguish their probable causes.

In other words, I don’t have a horse in this race. The universe is what it is, and the great quest is to learn as much as we can about it. I am not going to lose sleep if we discover a natural cause for the KIC 8462852 light curves because whatever is going on there is astrophysically interesting, and will help us as we deepen our transit studies of other stars. The recent paper from Wright et al. discusses how transiting megastructures could be distinguished from exoplanets, and goes on to describe the natural sources that could produce such signatures. The ongoing discussion is fascinating in its own right and sharpens our observational skills.


Image: The Kepler field of view, containing portions of the constellations Cygnus, Lyra, and Draco. Credit: NASA.

Yesterday’s post looked at ‘gravity darkening’ as a possible explanation for what we see at KIC 8462852, with reference to conversations we’ve been having in the comments section here. Gravity darkening appears in the Wright paper, though not with reference to KIC 8462852, and is also under study in other systems, particularly the one called PTFO 8-8695. But its prospects seem to be dimming when it comes to KIC 8462852, as Wright explained in a tweet.

He went on to elaborate in yesterday’s comments section:

Gravity darkening might be a small part of the puzzle, but it does not explain the features of this star. Tabby’s star does not rotate fast enough to experience significant gravity darkening. That post also suggests that planets could be responsible, but planets are not large enough to produce the observed events, and there are too many events to explain with planets or stars.

The Wright paper lists nine natural causes of anomalous light curves in addition to gravity darkening, including planet/planet interactions, ring systems and debris fields, and starspots. Exomoons, the subject of continuing work by David Kipping and colleagues at the Hunt for Exomoons with Kepler project, also can play a role, with a sufficiently large moon producing its own transit events and leaving a signature in transit timing and duration variations.

We have examples of objects whose anomalies have been investigated and found to be natural, including the interesting CoRoT-29b, in which gravity darkening is likewise rejected. From the paper:

CoRoT-29b shows an unexplained, persistent, asymmetric transit — the amount of oblateness and gravity darkening required to explain the asymmetry appears to be inconsistent with the measured rotational velocity of the star (Cabrera et al. 2015). Cabrera et al. explore each of the natural confounders in Table 2.3 for such an anomaly, and find that none of them is satisfactory. Except for the radial velocity measurements of this system, which are consistent with CoRoT-29b having planetary mass, CoRoT-29b would be a fascinating candidate for an alien megastructure.

We can also assign a natural explanation to KIC 1255b, an interesting find because its transit depths vary widely even between consecutive transits, and its transit light curves show an asymmetry between ingress and egress. What we are apparently looking at here is a small planet that is disintegrating, creating a thick, comet-like coma and tail that is producing the asymmetries in the transit light curves. This is an intriguing situation, as the Wright paper notes, with the planet likely pared of 70 percent of its mass and reduced to an iron-nickel core.

We may well find a natural explanation that takes care of KIC 8462852 as well, and the large scope of the challenge will ensure that the object remains under intense scrutiny. Both CoRoT-29b and KIC 1255b are useful case studies because they show us how unusual transit signatures can be identified and explained. We also have to keep in mind that such signatures may not be immediately found because Kepler data assessment techniques are not tuned for them, as the paper notes:

…in some cases of highly non-standard transit signatures, it may be that only a model-free approach — such as a human-based, star-by-star light curve examination — would turn them up. Indeed, KIC 8462852 was discovered in exactly this manner. KIC 8462852 shows transit signatures consistent with a swarm of artificial objects, and we strongly encourage intense SETI efforts on it, in addition to conventional astronomical efforts to find more such objects (since, if it is natural, it is both very interesting in its own right and unlikely to be unique).

Thus we leave the KIC 8462852 story for now, although I would encourage anyone interested in Dysonian SETI to read through the Wright paper to get a sense of the range of transiting signatures that draw SETI interest. The paper is Wright et al., “The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures,” submitted to The Astrophysical Journal (preprint).


Comments on this entry are closed.

  • Harry R Ray October 29, 2015, 9:46

    ljk AND randomengineer: I have made several comments in the past about this signal. This signal should ONLY receive TOP PRIORITY if(and ONLY if) you make a BASIC ASSUMPTION derived by NON-SCIENTIFIC means, BOT; based on a VERY LOGICAL PREMISE: That et’s will broadcast their presence by the MOST FRUGAL MEANS AVAILABLE! This signal could very well be a product of COMBINING TWO INDEPENDENT ENTERPRESES! ONE: A REPETING but NON-PERIODIC Benford Beacon, and TWO: Lightsail transport of goods between two planets with microwave beam assistance. In his blog regarding detection of lightsail leakage, Jame Benford mentioned the possibility of attaching a beacon to the lightsail apparatus and turn it on ONLY when the microwave power beam and the lightsail are both in alaignment with a target star, MINIMALIZING the TOTAL POWER OUTPUT! In this case, the DURATION of BOTH the “lightsail leakage” signal AND the Benford Beacon signal would be IDENTICAL! In his blog James Benford mentioned that the duration would be about ten seconds, which WAS the duration of the “Benford Beacon” CANDIDATE signal! HOWEVER, the corresponding “Lightsail leakage” CANDIDATE signal was NOT detected. WHAT I DO NOT KNOW is whether they were even SET UP to LISTEN to signals in the 68 GHz RANGE or not! If ANY reader of this website knows the COMPLETE FREQUENCY RANGE of SETI@Home,plese post it in a comment to THIS blog! If it turns out that ARECIBO was NOT TUNED TO 68GHz at that time, then TYC1220-91-1 SHOULD DEFINITELY be put on the TOP PRIORITY list

  • Marshall Eubanks October 29, 2015, 10:24

    By the way, KIC 8462852 is a 14th magnitude star, and a 20% drop in luminosity should be easily detectable from the ground. There needs to be a campaign set up to keep this star under continual observation for further transits.

    This could even be done (or started) by amateurs – many amateurs in the asteroid community routinely go 18th magnitude or even fainter. The important this is to start monitoring, and set up an alert system so that transit events can be confirmed by others.

  • Mark Zambelli October 30, 2015, 8:50

    @Harry R Ray
    I’ve trawled for some frequency ranges that the SETI@Home crunches through but I’ve not found a detailed write-up… I have however found some tidbits that seem to be telling…
    http://www.seti.org/seti-institute/project/details/seti-observations … this links to the SETI Institutes ATA pages where a chart shows that the “Terrestrial Microwave Window” of our atmosphere ranges from 1GHz to 10GHz.

    http://setiathome.berkeley.edu/sah_about.php this links to the SETI@Home site and while I haven’t found your info there are numerous frequency charts centred around 1.42GHz. Infact, the Crab Pulsar chart ranges from 1.34GHz to 1.50GHz.

    It looks like SETI has been selecting the water-hole frequency ranges (with channels that cover from 0.075Hz to around 1Hz depending) that give us the easiest task ie looking for ETI-METI attempts at directed and intentional contact with us. What this implies for signals out around 68GHz as you’ve stated I don’t know but I’d hazard a guess and say that SETI@Home wasn’t tuned to that frequency at that time.

  • Mark Zambelli October 30, 2015, 9:00

    Sorry, forgot to add that the Crab Pulsar frequency chart appearred in a pdf on that site entitled “New SETI Sky Surveys for Radio Pulses” by Siemiom et al. 2008. IIRC it was referencing the newer ‘Astropulse’ method adopted around that time after moving from the ‘classic’ to ‘advanced’ modes.

  • ljk October 30, 2015, 9:35

    Adam said on October 29, 2015 at 6:27:

    “On the question of visibility, as raised by randomengineer, one response to the “Killing Star” scenario (i.e. the frightful preemptive strategy of ‘blast others with relativistic missiles before they can get you’) is that very energetic weapons have very visible effects and are pretty obvious in origin. Thus good neighbors refrain from smashing planets or boiling oceans with a Nicoll/Dyson laser.”

    If you can build a Nicoll-Dyson laser you probably don’t worry about any celestial neighbors too much, unless they can build them too. In that event you make sure you build yours first, search for the competition (or potential competition) and make sure it does not become a competitor or other form of threat to your existence.

    As often as the public thinks aliens want to conquer Earth and therefore us, many others go to the other extreme and think advanced beings automatically mean enlightened, peaceful entities who gave up war and other allegedly primitive vices long ago.

    It is ironic, because many of these same members of the public also believe in angels and similar such supernatural beings and as the stories say, despite being second only to God, some of them went rouge and engage in a massive war for domination of the Cosmos. Just sayin’. So being smarter, old, and more powerful perhaps does not equal better ethically and morally. Everyone living in this Universe has to survive somehow to exist here, no matter how advanced and wise you may be, right?

    I wondered aloud before since Kepler detected KIC 8675309 in such a narrow exploration range of sky, does that mean we just got very lucky with this discovery or that many stars are being frequently eclipsed in this manner? Whether it is due to natural phenomenon or there is a massive galactic reconstruction effort underway, either idea is “a mighty soberin’ thought” as Pogo once said regarding alien minds. And if it is the latter, will we be asked to move or treated like ants at a construction site? Because as well-meaning as the Prime Directive of Star Trek is, I have my doubts that the fictional gesture extends to the reality of the wider Milky Way.

  • ljk October 30, 2015, 9:39

    Time to bring up again this very useful introduction to various concepts of alien life here:


    The Killing Star stuff starts here:


    To quote:

    As near as we can tell, there is no inhibition against killing another species simply because it displays a high intelligence. So, as much as we love him, Carl Sagan’s theory that if a species makes it to the top and does not blow itself apart, then it will be nice to other intelligent species is probably wrong. Once you admit interstellar species will not necessarily be nice to one another simply by virtue of having survived, then you open up this whole nightmare of relativistic civilizations exterminating one another.

    It’s an entirely new situation, emerging from the physical possibilities that will face any species that can overcome the natural interstellar quarantine of its solar system. The choices seem unforgiving, and the mind struggles to imagine circumstances under which an interstellar species might make contact without triggering the realization that it can’t afford to be proven wrong in its fears.

    Got that? We can’t afford to wait to be proven wrong.

    They won’t come to get our resources or our knowledge or our women or even because they’re just mean and want power over us. They’ll come to destroy us to insure their survival, even if we’re no apparent threat, because species death is just too much to risk, however remote the risk.

  • Mark Zambelli October 30, 2015, 10:18

    I promise I’ll go away in a minute :D

    Sky and Telescope ran an article in 2009 saying…
    “Of the entire radio spectrum, the band of frequencies from about 0.5 to 60 gigahertz has the least natural background interference in space. Any alien radio astronomers should realize this too — and perhaps they would build interstellar transmitters accordingly. Our atmosphere generally limits us to frequencies below about 12 gigahertz, but maybe other civilizations would have reason to choose the low end of the frequency range too….”

    It’s here…

  • Mark Zambelli October 30, 2015, 10:48

    (At the risk of being banned for consecutive posting, sorry, I’ve been under-the-gun today, sheesh…)
    That S&T article is chock full of juicy details covering 50yrs of SETI searches, their frequency ranges and number of channels etc… very informative and well worth a look.

  • ljk October 30, 2015, 12:34

    SETI has been flawed since it began “officially” in 1960 (or 1959 if you count the famous Nature paper on the subject) and not just because of technological limitations.

    See here for an excellent online history of SETI that you won’t find in most other sources:


  • Michael October 30, 2015, 15:55

    @Mark Zambelli October 30, 2015 at 10:18

    “Of the entire radio spectrum, the band of frequencies from about 0.5 to 60 gigahertz has the least natural background interference in space. Any alien radio astronomers should realize this too — and perhaps they would build interstellar transmitters accordingly. Our atmosphere generally limits us to frequencies below about 12 gigahertz, but maybe other civilizations would have reason to choose the low end of the frequency range too….”

    If they, the Aliens, see the same ‘windows’ and see us they would naturally move towards us even if at a great distance. I still think it better to remain silent, listen and then judge than shout to out loud and be judged by others that may not listen before judging. We have all seen what we have done to other creatures and ourselves, they may be no different and that worries me, life wants to survive and at any cost such is life.

  • Eniac November 1, 2015, 13:06

    If civilizations go interstellar, ever, at all, then the first one in the galaxy to do so will likely be the only one. This is not because of frightful “killing-star” scenarios. It is simply because of the extreme unlikelihood of two civilizations going through technological development at the same time. As far as we can estimate from our vantage point, it takes at most a millenium or so to go from first radio emissions to interstellar expansion. It takes a few billion years to get to the radio phase in the first place.

    So, unless we are willing to believe that all civilizations are content to stay around their own, single star forever, yet willing to launch interstellar missiles at others as soon as they are detected, the “killing star” scenario is nonsense. Rather, all civilizations in the galaxy will be descendents of the first to travel, and they will all be in communication and familiar with each other.

    Since we do not have a history of colonization, we must be the first, all others will be descending from us. Ergo, no aliens, at this time. Sorry.

    Just wait a few millenia, though!

  • Harry R Ray November 1, 2015, 14:33

    Mark Zambelli: Thanks for the info! I was Previously aware of the 10GHz UPPER LIMIT in the SETI@Home package. I should have mentioned in my(WAY TOO LONG) previous comment, that SETI@Home PIGGYBACKS on Arecebo when it is making OTHER OBSERVATIONS! I guess it all boils down to: What KIND of observation was Arecebo making at the EXACT TIME of the TYC1220-91-1 signal detection? Did the operators RECORD background noise UP TO 60GHz? Is that recording STILL ON FILE? Special thanks for the 60GHz upper limit info! That FORCED me to go back and read the ENTIRE “Lightsail leakage” paper. I found that 68GHx was just used as an EXAMPLE, and that a RANGE of “tens of GHz” would be the optimal frequency RANGE to propell a lightsail. Obviously, if any et’s would want us to detect BOTH SIGNALS(NECESSARY FOR CONFIRMATION), they would NOT use 68GHz! This complicates matters GREATLY, because Aricebo would have to be scanning the ENTIRE FREQUENCY RANGE from 1 to 60 GHz to pick up BOTH signals!

  • Eniac November 1, 2015, 22:09

    Look at it this way: In the extreme, let’s assume that every single star has a planet suitable for life, and that every single one of them develops life in a similar manner as on Earth. Even under such extremely lively conditions, the nearest civilization at our rough stage of development, between the radio and the interstellar ages, would be ~500 ly away from us. (cube root of the age of the Earth divided by the time between radio and interstellar stages, times the average distance between stars).

    Worse, though, half of all nearby stars would have had civilizations on them that passed into the interstellar stage long ago, yet none of them ever thought of coming here to open a branch office? Not very likely, I think. After all, settling other systems is the only effective way to ensure long-term survival for the race.

    The zoo hypothesis does not work, since for most of it’s 4 billion years this particular zoo had scum in it, at best, and was no more worthy of preservation than any other.

    The conclusion has to be that once the first civilization reaches the interstellar stage, the next one will, with overwhelming probability, be a colony rather than independently developed. And the next, and the next, until the galaxy is populated down to the last system. And if we are going to go interstellar, as most of us would suppose, we will be that first civilization.

  • Alex Tolley November 2, 2015, 10:54

    @Eniac – If that colonization is only carried out at the simple cellular level that we would call panspermia, then we are a descendant colony.
    Assuming that star flight is doable, and I see no reason why it shouldn’t for a least one species, then I agree with your conclusion. So we answer the Fermi paradox with the galaxy being empty of star faring civilizations (probably any civilization) and we are going to be the first. If so, then SETI will remain a study without any positive results, and METI is quite safe to do.

  • ljk November 2, 2015, 15:05

    Would an aliens species that can make a Dyson Shell be using radio and have it somehow aimed our way? Hmmmm….


  • Hiro November 2, 2015, 17:46

    There is a scenario whose colonies send relativistic spaceships to each other, after several hundred or thousand years of misunderstandings, it would happen with high probability.

    The zoo hypothesis never worked in the first place, when was the last time any of us trying to communicate with earthworms in their own backyards? Does anyone remember doing this?

  • Eniac November 3, 2015, 1:13


    If that colonization is only carried out at the simple cellular level that we would call panspermia, then we are a descendant colony.

    In a way, yes. However, panspermia is the spreading of life without intelligence, and a completely different beast. You can have panspermia without interstellar travel, and vice versa, so the two do not really inform each other. Also, panspermia is purely speculative (to avoid the word fantastic), much more so than purposeful interstellar travel, in my opinion.

    The dependent colonies that I am talking about are ones where there is a clear, historical connection, where the descendant colonies have at their disposal all of the achievements and cultural heritage of those that came before them. They would also be in light-speed contact with sister colonies, probably in the form of a galactic store-and-forward communications network.

    On second thought, there is one connection with panspermia: If you believe in interstellar panspermia, it would be much more difficult to explain why we might be the first. Being first is very similar to being alone. The former follows from the latter, of course, but the latter also strongly implies the former, statistically. Think about all the times you found yourself first at a party or meeting. Chances are, most of those times you misunderstood the arrangements and nobody else showed up, even after a long wait.

    Panspermia would rob us of the easiest explanation of why we might be alone, and thus first: Because life is incredibly hard to start from scratch.

  • Eniac November 3, 2015, 1:23

    Ah, tripped over my own logic, there. That sentence should have been “The former follows from the latter, of course, but the former also strongly implies the latter, statistically.” Yes, awkward, I know.

  • ljk November 3, 2015, 11:19
  • Alex Tolley November 3, 2015, 14:25

    @Eniac – I was thinking more of directed panspermia. I could imagine that we will be able to detect habitable but lifeless worlds and send life to them in small packages with the hope of greening the galaxy. This may be an altruistic gesture, or it may be to pave the way for distant descendants to find suitable living worlds to colonize. Clarke suggested that ETIs might seed the galaxy and monitor their progress, aiming to create intelligence as their ultimate goal.

    This makes sense if you are the first or only intelligence and are looking for company in deep time.

  • Alex Tolley November 3, 2015, 14:34

    @ljk – Walker has an interesting idea, but IMO it seems based more on reductio ad absurdum and used to account for the Fermi paradox observation, rather than a logical argument. A “Just So” story, in effect.

  • Jim Strom November 3, 2015, 16:23

    @Alex Tolley, Nov. 3 14:34:

    Agreed. The Walker paper is kind of silly. Predicting population habits of a hypothetical ETI is pure imagination. The best we can probably say about an ETI is that, as a product of evolution, an ETI would at least initially have expansionist tendencies, since evolution favors lifeforms that expand into new habitats; expansion is a favorable survival trait. Whether that carries forward to advanced civilization is another question.

    Also, it’s impossible to conclude, from currently available observation data, that ETIs are sparse or non-existent. We can conclude nothing, since the search space is almost vast, and we’ve hardly even begun to look in earnest.

  • Eniac November 4, 2015, 0:06

    LJK: The Walker article is nonsense. He repeats the tired argument that exponential growth can not last forever (which is trivial), but then fails to say how it follows that expansion through space will stop (because it doesn’t follow). Then he argues ETIs must have stopped expanding because we don’t see any (Duh.. what if they don’t exist?). He does not even try to come up with a mechanism of stopping expansion (because that would be extremely difficult).

    Does anyone really believe that hundreds of civilizations spread over tens of light years of space could put a stop to further colonization? How? By edict? By perfect consensus? How else, and why? If you think about it just a bit, the idea is ludicrous on its face.

  • Eniac November 4, 2015, 0:21

    We can conclude nothing, since the search space is almost vast, and we’ve hardly even begun to look in earnest.

    Another tired argument. There are quite a few things that can be concluded from little or no observation, much less “covering the search space”. Einstein’s theory of relativity is a pretty good example. When he concluded it, the “search space” was practically untouched. The Fermi paradox is another such example: The fact that there are no ETI here tells us a lot, even before we carefully search the entire galaxy. What exactly it tells us we may argue about, but it is not nothing.

    If you postulate that ETI exist, you must allow this theory to be falsifiable. If you require sending a probe to every star in the galaxy before you conclude you were wrong, then the theory is unfalsifiable in practice and therefore not scientifically meaningful.

  • Eniac November 4, 2015, 0:32

    Alex: Ah, I did not realize you were talking about directed panspermia. That is indeed another way for ETI to spread, but it would be exceedingly slow. Billions of years until another ETI may arise out of whatever organism you are seeding. Even the slightest tendency for direct propagation would obliterate any effect that such efforts would have. Your seeds may arrive first, but they would soon be trampled on by colonists, or shoved aside by self-replicating machines interested in the ores below. Much too soon to have time for any significant amount of natural evolution.

    Quite generally, evolution is finished. It has been replaced by intelligent design. It is not coming back, because the latter works a billion times faster.

  • Harry R Ray November 4, 2015, 13:23

    Jason Wright: ANOTHER BIZARRE KEPLER LIGHT CURVE FOR YOU TO INVESTIGATE! Please read the PDF: Characterization of KEPLER 91b and the investigation of a Potential Trojan Companion using EXONEST. By Ben Placek, Kevin H Knuth, Daniel Angerhausen, Jon Jenkins. They posit that, despite the baysian analysis strongly FAVORING the two planet model over the one planet model, the potential trojan planet is most likely to be the product of a false-positive due to the fact that the secondary eclipse of the trojan candidate produces a MUCH DEEPER DROP IN THE LIGHT CURVE than the transit does. My problem with this is that you would ALSO have to summarily REGECT the transit light curve as being a false-positive ALSO! To have TWO FALSE POSITIVES at precicely the L2 or L3 point seems very strange to me! In the paper, they stated that there might be an UNKNOWN MECHANISM that can heat a planet’s surface to make it HOTTER than the surface if its parent star. My question to you, is; could a swarm of MIRRORS in orbit around the trojan planet candidate pointed directly at the star ALSO produce the candidate secondary eclipse flux?

  • Harry R Ray November 4, 2015, 13:24

    hould the ABOVE MENTIONED light curve BE worthy of FURTHER INVESTIGATION by Spitzer. I invision THREE POSSIBLE OUTCOMES! ONE: Spitzer does not detect either the transit or the secondary eclipse of the trojan planet candidate, meaning that BOTH Kepler light curvea ARE false positives. TWO: Spitzer DOES detect BOTH transits ALD secondary eclipses, indicating a planet whose surface IS hotter than the surface of its parent star, most likely as a result of ohmic dissipation generated by the magnetic fields of the trojan, hot jupiter, and parent star. THREE: Spitzer Does detect the trojan candidate’s TRANSITS, but does NOT detect the seconfary eclipes, favoring my “mirror hypothesis”.

  • Alex Tolley November 4, 2015, 14:23

    @Eniac. I agree. Times scales are very ong, and it seems rather pointless to send even single cell eukaryotes to colonize planets as gigayears will be needed for them to evolve. It only makes sense if colonists, ETI or robotic won’t be following. A large ship full of dormant plant sores/seeds etc would work better, perhaps withing a few kilo years to do useful terraforming.

    It is also possible that ETIs might engineer biology to be very efficient and rapid at terraforming, reducing the needed time. More like robotic directed terraforming.

    However, in general I agree with your point. Colonization by ETIs will be more rapid than any slow directed panspermia, or even pre-colonization terraforming.

    But be aware that speciation is occurring on Earth right now. You may have heard of the recent Coyote/Dog/Wolf hybrids that are doing very well as we urbanize. It can be quite rapid in some instances if evolution doesn’t have to be recapitulated.

  • Marshall Eubanks November 5, 2015, 0:35

    Evolution is like thermodynamics – intelligence can’t get you out of the game. “Intelligent design” (what a loaded phrase choice) is also subject to evolution. If we are replaced by machines, they will be subject to evolution. If designed genomes (or super-intelligent machines) tend not to be evolutionarily fit, we will not find many in the cosmos.

    And, any truly galactic civilization will have long time constants. I would have a very hard time saying that a 10 billion year old civilization would necessarily shy away from multi-billion year gardening projects, and thus would find any sort of panspermia too slow.

  • Alex Tolley November 5, 2015, 11:18

    @Marshall Eubanks
    Biological evolution will affect civs too. Species last on average about 1 megayear, so a 10 gigayear civ seems unlikely, although it could be an ongoing process, replacing species as they come and go. But I don’t see how it could be a homogenous, single species over 10 gigayears.

    If we assume some form of directed panspemia, theortically the galaxy could be seeded in around 50 kilo years starting from the core. Self replicating machines have been suggested as taking 1 megayerar to fully reach every star.

    We know that landscapes recolonize in less than 10 kiloyears after a glacial retreat, so a robotic gardener might terraform a planet in a very short time.

    So for me, the question is whether terraforming in advance of colonization makes sense or not, given the likely lifetime of the technological species? I think that this terraforming might be considered altruistic by civs, as a way to propagate advanced life forms irrespective of the survival of the civ species.

    The potential horror story might be that civs develop the ST “genesis” device, allowing destruction and recreation of new life forms at will. Each new civ could therefore transform the galaxy to its liking within a million years. The good news is that there is no evidence that this has happened on Earth, so this isn’t a likely prospect.

  • Jonathan Quinn November 5, 2015, 19:39

    Any guesses on what the SETI Institute’s planned announcement will be about at 17:00 PST today? https://twitter.com/setiinstitute/status/662329838724886528

  • Alex Tolley November 5, 2015, 21:47

    Looks like SETI found nothing at the frequencies they looked at. Hardly unexpected.

  • Eniac November 5, 2015, 23:54

    Alex, Marshall: I understand Evolution to be the combination of random mutation and natural selection. As you note, natural selection will still be around, but random mutation will cease to be a factor in the face of deliberate engineering (tried a new wording so we do not attract nutcases to this blog). Traditional evolution will be relegated to niches that are too remote or uninteresting for us or any of our intelligent descendants to mess with in millions of years. I doubt there will be a lot of those.

    I intentionally avoid talking about long-lived civilizations. The lifetime of civilizations (as in Greek, Roman, Modern, etc.) tends to be a few centuries at most. They tend to get replaced by other civilizations. What remains eternal is the line of descendancy. Using genetics, we can trace our ancestry back for billions of years, up to the so-called “universal common ancestor”. We know, even though we cannot study it, that the line extends further back, to the very origin of life. There is no reason to think that this line will not also continue indefinitely into the future, especially if it gets to spread through galactic space. Even if machines take over one day, the line will not be broken, because being designed and built by us entitles future mechanical lifeforms to be called our descendants.

    We have kind of a special situation at this time. It used to be the Earth was big enough to hold many civilizations, in different regions and continents. Nowadays, electronic communication and jet travel have made the world too small to hold more than one civilization, really. In the future though, after the first interstellar colonies have been created, there will be multiple, truly independent civilizations, again. The light-speed communications limit ensures this. The beginning of the interstellar age will mark our passage from being a slightly endangered species on a single planet to having the ultimate safety in numbers across the galaxy. If we ever get our act together, that is….

  • Eniac November 6, 2015, 0:07

    Marshall Eubanks:

    Evolution is like thermodynamics – intelligence can’t get you out of the game.

    I would respectfully disagree here, evolution is nothing like thermodynamics.

    Also, far from getting you out of the game, intelligence overcomes the enormous roadblock that makes evolution so time-consuming: waiting for random mutations to accumulate and be selected until they constitute meaningful change. Intelligent design achieves in years what takes millions the old-fashioned way. You may call this new paradigm evolution still, but I wouldn’t. It is totally different, more akin to revolution.

  • Eniac November 6, 2015, 0:19

    Alex, I agree that it might be useful to seed organisms for terraforming, but with people (or whatever our descendants may be) likely being used to live in space, anyway, I doubt everyone will want to wait for the process to finish before disembarking.

  • Harry R Ray November 6, 2015, 10:59

    Jonathan Quinn: ATA has ruled out ANY narrow-band signals(I would have been FLABBERGASTED if they had found any)of order of 1Hz in width, and; any broadband signals that would be due to beamed propulsion(i.e., lightsail leakage) between 1 and 10GHz. In light of the fact that a recent paper on lightsail leakage indicates that the OPTIMAL transmission frequencies are in the “tens of GHz” range, this is not an ENTIRELY null result. In fact, if a frequency of GREATER THAN 69GHz were used, we may not be able to detect them due to atmospheric interference. SO: it looks like we will have to wait for the results from Dr Wright’s Green Bank observations or from the JVLA run in January of nest year to COMPLETELY RULE OUT any kind of lightsail leakage DETECTABLE FROM THE GROUND, and a space-based radio recever to COMPLETELY ELIMINATE this possibility.

  • Marshall Eubanks November 6, 2015, 12:54

    Eniac, I don’t think you understand my point. Assume that you are correct, and “Intelligent design achieves in years what takes millions the old-fashioned way.”

    OK, wait 50 million years, and what do you have? Is this ID system still around? Has it been overcome by some other ID system? Or are silicon based machines superior? Or has something else supplanted them all? Or have they all gone extinct while the old fashioned biology continues to putter along?

    This is all still evolution. Evolution is like thermodynamics in that you cannot get out of the game. Any choice you make is an evolutionary choice, and what matters in the long wrong is not what is more intelligent, but what survives. ID may speed things up, but it doesn’t get you out of the game.

    This is why I say silicon based von Neumann machines (if such can really be created and developed to the point of being autonomous) will be a form of life (that may require carbon based life to create it). It (they) will evolve too, because silicon based life can’t get out of the game either.

  • Marshall Eubanks November 6, 2015, 13:07

    Harry R Ray – ALMA, 5000 meters up on the dry Atacama plateau, looks through atmospheric windows up to 865 GigaHz (350 microns), so it would be possible to detect lightsail leakage well about 69 GHz. (There are only a few sites in the world that could support ground based observations at these frequencies – Mauna Kea is one and the Himalayan Plateau is possibly another.)

  • Eniac November 7, 2015, 1:47

    OK, wait 50 million years, and what do you have? Is this ID system still around? Has it been overcome by some other ID system? Or are silicon based machines superior? Or has something else supplanted them all? Or have they all gone extinct while the old fashioned biology continues to putter along?

    Good questions. I do not know the answer to them. What I do know, though, is that the world will look vastly different in 1000 years, and traditional evolution will have nothing to do with it. What sense does it make to ask about 50 million years in the face of this?

    Unless you are using evolution in an extended sense where it does not imply random mutation as the mechanism of (slow) change. I suspect you are, in which case you are right, and our differences are largely semantic. I am pretty sure, though, that in common understanding of the word slowness is part of its definition, with revolution as an opposite.

    Self-replicating machines can be designed to replicate exactly or not at all, excluding random mutation completely. All you have to do is cryptographically sign the “genome”, with a hash code, such that any changes will invalidate it.

    At some point in the future, it may be possible to build self-replicating machines that can intelligently improve their own design. This would give rise to very rapid change (c.f. singularity), and, at least in my dictionary, this is not to be called “evolution” by any means.

    And again, as a physicist and geneticist, I can tell you that thermodynamics and evolution are as different from each other as theories get.

  • Hiro November 7, 2015, 15:17

    In 3000 A.D. one of these 3 possibilities will happen:

    1) Quantum AI

    2) Idiots throw rocks at other idiots during wars.

    3) Rats become the next overlords on this planet.

    @ Eniac: If we fail to solve our problems on this planet, interstellar colonies won’t be stable for a long period of time. At least I guess extremists from different religions or organizations sending relativistic spaceships to other fractions and maybe even the Earth itself as Christmas gifts will happen with high probability.

  • Rob Henry November 9, 2015, 2:35

    @Alex Tolley, Francis Crick pointed out that directed panspermia can always go further. If normal intergalactic travel is impossible, directed panspermia may not be. What if an Andromeda wide civilisation began seeding our galaxy 2 billion years (at about the time of the first indisputable microfossils), then planted seeds of the Cambrian throughout the Milky Way only 600 billion years ago? If so the very highest forms might have started appearing at around the same time, with the oldest less than a hundred million years ahead of us.

    Okay, that all seems unlikely, but it shows that you were right to bring up the utility of directed panspermia in this context. It is one of the few ways in which the presence of a K2 1400 light years away could be explained in the absence of evidence for ETI presence on Sol.

  • ljk November 10, 2015, 12:57

    They are playing funding games with Arecibo. The loser is going to be science.


    $12 million – that’s pocket change for most branches of government and the military. People are going to start scrambling for that bigger and newer dish in China, but how open they will be to access and data remains to be seen. And it is far more remote than Arecibo.

  • Eniac November 12, 2015, 0:04

    I agree with Rob. Directed panspermia would be the most likely explanation should we find that there are more (seemingly) independent civilizations at similar levels of development than expected by chance.

    Of course, our current observations do not call for such an explanation, leaving panspermia (even directed) firmly planted in fantasy land.

  • ljk November 23, 2015, 10:36

    Yes a collection of primitive primates who still act like tribes of chimpanzees living in the rain forest would be comforted with a Universe where there are no competitors that can outsmart and dominate or destroy them. Because that is the main focus of social animals 24/7, where they stand in the pecking order.

    Here is more comfort food, humanity, because yes you are special because a big magical father figure in the sky made all this just for you:


    I am sure no one else in the Cosmos with a mind that can conceive past its next meal or mating opportunity ever thinks that way, either.