Intelligent Design Science

Are We Alone? Identifying Intelligence with SETI

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Eric Anderson of just sent me an interesting essay I’m sure UD readers will enjoy, so I reproduce it below. Eric is a regular commenter at UD, and he is a very insightful fellow who writes extraordinarily well. (Since I design computational algorithms as both a profession and a hobby I particularly enjoyed his essay Bits, Bytes and Biology: What Evolutionary Algorithms (Don’t) Teach Us About Biology, concerning the Avida program, and I highly recommend it to UD readers.)


Are We Alone? Identifying Intelligence with SETI

Eric Anderson

I just got back from a presentation this morning by Dr. Seth Shostak, Senior Astronomer at the SETI Institute, on the topic: “Are We Alone?”

By way of background, I had an email exchange with Dr. Shostak some time ago regarding Guillermo Gonzales, so I was somewhat guarded about what to expect from his presentation.(1) I was hoping to have the opportunity to perhaps ask a question or two from the floor, but in fact was able to do much more than that. Dr. Shostak not only took my main question from the floor, but was kind enough to spend several minutes with a few of us afterwards, taking additional questions and providing follow up.

General impressions

Dr. Shostak is a master at public outreach. Although I would have preferred a bit more meat, his presentation was definitely at the right level for the general, well-educated public. He was thoughtful, provocative, and most importantly, funny. Not once, but numerous times, he had the audience laughing – either from a witty turn of phrase or from a parody about the public’s impressions of SETI’s work, such as some fun he had with Roswell (“Why bother looking in the far reaches of space for aliens? They’re already here!”). I am confident he has given the same presentation numerous times, but he nevertheless delivered it with a great deal of energy and a genuine sense of enthusiasm about the work he is involved in. His demeanor was not reserved for the prepared presentation either – with the small group afterwards he exuded the same charm and enthusiasm.

Identifying Intelligence

My question from the floor was essentially as follows: “How do you distinguish between an artifact of intelligence – a signal produced by an intelligent being – and a naturally-occurring phenomenon? And how confident can you be in your assessment?”

Dr. Shostak’s answer was essentially that you look around to see if you can identify other similar signals from various places in the galaxy, and if so, you have probably confirmed that the first signal was just a naturally-occurring phenomenon. This was certainly not the answer I was expecting nor even the direction, as I had anticipated he would respond by referring to information content, probability calculations, etc. Indeed, his response suggested essentially a negative filter: if it doesn’t appear to be a naturally-occurring phenomenon, then it might be an intelligent signal. I concluded that Dr. Shostak had either (i) misunderstood my question, or (ii) only partially answered, focusing on the negative side of the filter, rather than the positive identification characteristics used to detect a signal produced by an intelligent source.

Digging Deeper

After the presentation I fortunately had the chance to dig deeper. I indicated to Dr. Shostak that while he had provided an example of the kinds of things that might be done to determine whether a particular signal is naturally-occurring, I was really interested in the positive side of the equation by detecting design in the signal itself. Dr. Shostak responded by offering another specific situation: You see a radio wave coming from the location of a sun-like star; you know that type of star doesn’t produce that kind of signal, so that increases your confidence that it is probably coming from a planet around that star.

That again seems to be a purely negative filter. He did, however, add something that I think looks more like a positive indicator: namely, you check the periodicity of the signal to see if it exhibits some of the characteristics you would expect from a planetary origin, specifically, Doppler effects related to both the planet’s rotation and orbit.

I still wasn’t satisfied. Following a few more questions, I circled back to my central query: Isn’t there something in the signal itself that would allow you to determine that it is produced by an alien intelligence? The answer, in short, was no.

How Can We Resolve This?

Here is the reason for that surprising answer: in most cases(2) the resolution of signals across interstellar distances is not sufficient to identify the message itself, only the kind of signal. As Dr. Shostak explained it, SETI is doing the equivalent of a long-term exposure, and the signal is just too faint to tease out individual components. Thus, SETI can identify the location and type of signal, but not a message itself.(3)

Think of it this way (my example, so any failure of analogy is mine, not Dr. Shostak’s): In long exposure astrophotography, you leave the shutter open for a lengthy period of time, and in many cases you then further stack multiple exposures to obtain a useful image. The signal is so far away and so weak by the time it reaches Earth, that long-term exposure is needed just to obtain the faint signal. This works relatively well for astrophotography because the objects that are being photographed are typically stable over minutes, hours, days or even years. In other words, the same picture or “message” is being transmitted continuously – the equivalent of a galactic still life.

However, think what would happen if instead of a still life the interstellar “picture” you were photographing changed many times per second, like a high speed slide show or individual frames of a video. At the end of the long exposure you would have definite evidence of a signal – of type x, from location y, with average strength z – but the entire picture would be washed out and utterly useless from a standpoint of trying to determine what any individual frame of the show looked like. Similarly, with radio signals the message is encoded in small changes to the signal that vary many hundreds or thousands of times per second. As a result, if you can only “see” the signal by staring at it for an hour, you certainly will not be in a position to identify individual pieces of a message encoded in bits that vary thousands of times per second. Any message that may have been contained in the signal will be completely washed out from the long-term exposure required to see the signal itself.

If I am correct in my understanding of the above, this means that, barring some unusual circumstance, SETI is not able, and does not expect to be able, to read a message from an alien civilization.

Thus, it is not so much that Dr. Shostak misunderstood my original question about what kinds of artifacts need to be present in a signal to allow us to identify intelligence. Rather, my question rested on a misconception that SETI has the ability to receive a “message,” when in fact it only has the ability to identify the general parameters of a signal. SETI then uses what is largely a negative filter, albeit perhaps with some positive parameters in particular instances, to decide whether the signal is a naturally-occurring phenomenon. If it is not, then that increases the confidence that they have detected an intelligently-produced signal.

Meaning in the Message

There are a couple of implications flowing from the foregoing.

First, one oft-leveled charge against Dembski’s explanatory filter is that it is just a negative filter. I believe this assessment is not completely accurate, but even if the filter is negative, SETI gives us an example of how a negative filter can, if not provide a definitive conclusion, then at least guide tentative assessments of the artifact we are examining. (I suspect we could find other examples in archeology and forensics of purely negative filters being put to good use.) Thus, if someone takes the position that the work SETI is doing is scientific in nature – not necessarily the underlying assumptions about the likelihood of intelligent extraterrestrial life, mind you, but the actual signal detection and analysis work itself – then it seems one must also be willing to grant that use of a negative filter can be a valuable scientific tool. At the very least, use of a negative filter as one of the tools does not invalidate the entire enterprise.

Second, the relationship between the work SETI is doing and design detection in other areas is slightly different and more nuanced than what is typically perceived. Specifically, although Dembski refers to the movie Contact by analogy, and to SETI specifically, as examples of design detection, in fact SETI does not expect in most instances to be able to tease out a message. In biological terms, this situation might be likened to the initial discoveries of DNA’s existence and structure, coupled with the then-still-unproven hypothesis that DNA might contain some useful information. Thus, SETI is helpful in terms of setting a lower bound of confidence for what is needed to infer intelligent activity: a signal with the same general characteristics as would be produced by an intelligent agent, together with the absence of a natural explanation. This is a much lower threshold than Dembski’s probability bound, and it seems design detection, as applied to biology, can take a much stronger position in terms of its confidence in asserting design. SETI’s receipt of a signal across space, even without resolution of the underlying message, may be sufficient in some cases to detect intelligent activity. To pursue the analogy, the very existence of the DNA molecule, while an important signal across time, has now been resolved to the level of the underlying message. And with DNA and the other complex specified information found in biology, therein lies the much stronger positive case for an intelligent source.

Closing Thoughts

I hope to follow up at some point with Dr. Shostak or other SETI personnel to make sure that my understanding of the SETI approach as briefly outlined above it is accurate, specifically in terms of the general inability to obtain the resolution necessary to resolve a message, and also in terms of the extent to which the inference to intelligent activity is based on a negative, as opposed to positive, filter.

This post is already too long, but at some later date I might perhaps also offer a few thoughts on the aspects of Dr. Shostak’s presentation that were less strong, such as the ideas about artificial intelligence and some of the underlying assumptions, including evolutionary assumptions, that get included in the Drake equation variables.

In any event, I hope the above provides a better understanding of SETI’s approach and its broader implications for detecting the artifacts of intelligence, both across the reaches of space and closer to home.


(1) As an aside, regarding other SETI impressions, I keep on my desk an article from late 2004 by Dr. Emma Bakes, Principal Investigator at the SETI Institute, that astoundingly states: “Additional experiments performed by Sagan and Khare showed that adding water to Titan haze analogs produced amino acids, so that one form of life based on these types of hydrocarbons could spawn another similar to terrestrial life. For the transformation of organic hydrocarbon chemistry to terrestrial life, ‘just add water.’” (Emphasis added).

(2) Barring, I suspect, a relatively proximate alien civilization that has produced a massively-boosted signal for the express purpose of interstellar communication, and which also happens to be pointing Earthward.

(3) Again, let me suggest that if there were an alien civilization bent on sending out a signal in order to be heard they could potentially overcome this limitation. Dr. Shostak’s practical point, however, is that if you are eavesdropping on an intelligent civilization that doesn’t have as its purpose to be heard, the kinds of signals it produces would likely not have the resolution required for transmission of a message across interstellar space.

11 Replies to “Are We Alone? Identifying Intelligence with SETI

  1. 1
    DaveScot says:

    I don’t think Shostak was being candid in this:

    Isn’t there something in the signal itself that would allow you to determine that it is produced by an alien intelligence? The answer, in short, was no.

    I’m sure he’s wary of being trapped into supporting design inferences based on the content of the signal and is thus well practiced in how to avoid the trap. But really SETI has to do just that. Interesting signals that sometimes show up in the data are of human origin that manage to creep into the receiver electronics in various ways. In order to rule out false positives, which would be hideously embarrassing if released to the public, they have to check and recheck and check again for possible local, manmade sources of the signal.

    I think he’s being less than candid about the method in which ambiguous signals of definite extra terrestrial origin are checked out. By now any signals that fall through all the tests for known phenomenon are going to be exceedingly rare. They’re needle in a haystack kinds of things and you don’t go about searching all the other haystacks to see if the needle is unique because that search is intractibly long.

    I think Shostak could have been cornered by simply asking whether the movie “Contact” is correct in that a carrier signal modulated with a repeating prime number sequence, once terrestrial sources of the signal have been ruled out, would be taken as positive evidence of intelligent origin. Sagan, the author of “Contact”, was one of the most informed scientists in the world when it comes to SETI and astrophysics in general. Shostak would be stuck between a rock and a hard place. He’d either have to try saying that the most recognized astrophysicist and SETI enthusiast in the world had no idea what he was talking about (ludicrous) or he’d have to admit that modulation alone can be sufficient for a design inference.

  2. 2
    Patrick says:

    What someone should do is come up with classes of cases in which the filter…will fail.

    1. False negatives.

    2. Cases where an unknown law is involved.

    3. In the minds of Darwinists…

  3. 3
    DaveScot says:

    I think Dr. Shostak was being sincere.

    Personal impressions aside we can find that out by looking at the facts on the ground.

    We were talking about the specific signals they typically monitor and what they would expect to see.

    Pretty limited expectations if an unmodulated carrier is all they hope to find. What ET would go to the trouble of constructing a transmitter and not use it for anything more than the moral equivalent of “Kilroy wuz here”?Makes no sense at all. Surely they’d encode some message on the carrier, which is something that is easy to do – the carrier is the hard part – with at least something like “No Tresspassing”, “Viewing by Appointment Only”, “Watch for Falling Asteroids” or something of that nature for Pete’s sake. Even the earth natives thousands of years ago modulated smoke signals with messages.

    What he’s describing to is what it takes for a signal to fall through the automated signal filters and raise a flag for a human to have a closer look at it.

    His response was in that context. He does, and did in fact, acknowledge to me that if they could read the actual signal it would be easier to detect intelligence. His specific example was, “if we saw a picture, that would be easy.”

    If you saw a lot of things it would be easy. A short prime number sequence is enough to be unmistakable.

    My purpose was not to press him into any discussion or admission about ID.

    It sure read like a good portion of the questions and responses sounded like you were asking for what criteria SETI uses to arrive at a design inference. That’s ID. Saying it isn’t ID won’t change that. You can call a tail a leg but it doesn’t change the fact that a dog doesn’t have 5 legs.

    I already know that he thinks identifying artifacts of intelligence is perfectly valid and acceptable in SETI and similar kinds of endeavours. And I already know (I think) that he views ID as non-science.

    He must be confused about what ID is. Examining patterns for signs of intelligence either is or isn’t science. No double standards.

    My impression is that Dr. Shostak is like a number of scientists who admit that there is something called intelligence, that it can be identified in certain areas (such as SETI, archeology, forensics), but that design detection does not apply to biology.

    Arbitrary and unjustifiable to exclude biology.

  4. 4
    j says:

    Carl Sagan and Frank Drake, “The Search for Extraterrestrial Intelligence,” Scientific American (1975):

    How could we be sure that a particular radio signal was deliberately sent by an intelligent being? It is easy to design a message that is unambiguously artificial. The first 30 prime numbers, for example, would be difficult to ascribe to some natural astrophysical phenomenon. A simple message of this kind might be a beacon or announcement signal. A subsequent informative message could have many forms and could consist of an enormous number of bits.

  5. 5
    Portishead says:

    Patrick (5),

    “2. Cases where an unknown law is involved.”

    Yes, but how can you ever use the filter if if fails because there may be an unknown law involved? At the point where you apply the filter – i.e. at the point where you are using the filter to decide whether an article has been designed or not – then if you get a positive result you would have to say it’s either designed or not. If there is an unknown law then by definition you can’t take it into account at that time. Unless, of course, applying the filter gives a conditional response of “it’s been designed UNLESS there is an unknown law involved”, but that makes the filter a rather weak tool.

  6. 6
    DaveScot says:


    The reality is that SETI enthusiasts have lost hope of ever finding ET. It’s not 1975 anymore. It’s over 30 years later and SETI didn’t even hear the sound of crickets chirping. As hope wanes so too does funding. There’s no chance that a carrier can be detected in a scan without being able to detect modulation when determined focus is applied to the carrier. Signal strength sufficient to be detectable in a scan can be amplified tremendously by bringing more instruments to bear on it over a longer period of time. There’s also no chance of detecting anything by eavesdropping. Signal strength in normal communications just aren’t designed to go far past their intended recipients. The attenuation across the vast gulf of interstellar space is just too great.

    So here’s what you can bet your bottom dollar has become of SETI. In order to justify the cost of keeping the gear and staff running at some minimal level they’re leveraging the ability to pick up anomalous signals that have never been observed before. Rather than any of these being potential ETs the value is that the anomalies will reveal heretofore unknown natural processes.

  7. 7
    magnan says:

    It seems to me there is a plausible argument that the failure so far of SETI to find anything is most likely because they just aren’t out there, at least in this galaxy. Not because they are out there but signals from even the nearest ones are so attenuated they can’t be detected. SETI hopes that very many other civilizations have developed somewhere in the galaxy at various times during its lifetime so far of 10 billion years or so, assumes they are isolated by the vast distances, but also hopes that there are enough existing now that they can detect the signals of the closest ones.

    Even present technology projected a century or so with no breakthroughs in physics would enable humanity to launch relatively very slow sublight velocity probes to the nearer stars. Moderately projected current technology with no physics breakthroughs would seem to allow the development of multi-generation (or suspended animation technology) sublight velocity ships carrying human beings to the nearer stars with travel times of centuries to thousands of years. This projection doesn’t seem to require any ridiculous science fiction, just extension of current science and technology with no fundamental breakthroughs.

    If life compatible worlds exist in the local Galactic neighborhood it would seem that even humanity has at least the potential to explore the closest planetary systems, colonize, and in turn eventually send out more ships to colonize out further into the Galaxy. Calculations show that this process shouldn’t take more than a couple of million years to eventually spread over all of it.

    If the SETI enthusiasts are right about the prevalence of life in the universe, over the lifetime of the Galaxy there should have been countless emerging intelligent races, and by now at least one of them should have colonized the Galaxy as outlined above. But there doesn’t seem to be anyone around. Unless you consider UFOs, and let’s not get into that argument.

  8. 8
    DaveScot says:

    I think you’re a bit more pessimistic about the effort than most SETI enthusiasts are.

    Probably because most of them have yet to experience 40 years of “nothing yet”. Most of today’s enthusiasts are probably SETI@home volunteers who were decades away from being born when I was watching Mercury astronauts live on black & white broadcast television.

  9. 9
    Rude says:

    Interesting subject and comments. B D Knight … you’re not suggesting that “the precession of Mercury about its orbit” would have provided a false positive. This was—unless I misunderstand—a regularity not predicted by Newton’s laws. Maybe we have there a good example of where the unexplained does not give rise to a “god of the gaps”.

    But maybe also there is a sense in which contingent regularities can provide evidence for design. The laws and constants of physics taken as a whole, for example, if they are contingent and if they have an “anthropic” specification, then don’t they point to a designer? Oddly enough ID’s adversaries are more ready to accept design on that level than in biology (E Anderson: “(iv) they have an underlying philosophical aversion to the idea of design in biology”) where absolute front loading just might not be what the doctor ordered. Somehow if the Designer’s involvement can be pushed back to the “first three minutes” or so it’s not so heretical as getting him involved down the line. Wonder why that is?

    Dave’s right to say it’s arbitrary and unjustifiable to exclude biology.

    By the way—whether or not there is intelligent life out there depends on different factors for materialists and ID. Materialists have to show that chance and necessity are up to the task, ID is neutral because it can’t see into the mind of the Designer.

  10. 10
    es58 says:

    This month’s IEEE spectrum says that Paul Allen of Microsoft gave SETI $25M to build an array of satellite dishes. As can easily be determined by examining the web debates, or any popular MSM newspaper or mag, every “true” scientist (similar to true scotsmen?) knows that intelligent design == creationism == religion. The moment a scientist suggests ID is possible, he is instantly converted into a former (and we always suspected he never really was a) scientist. So that must imply that Allen is religious? Or, alternatively, is legitimacy as a scientist determined by *who* you are, are who you associate with, rather than what you hold? (eg: You’re from discovery instititute? You’re illegitimate by definition regardless of your resume/qualifications)

  11. 11
    Patrick says:

    Partly because it is easy for me to imagine the evolution of things like the flagellum.

    Really? Then you must have access to better information than Bob Ohara, who ignored my direct challenge of “name the functional intermediates in the indirect pathway.” (Of course, he did the same thing earlier when F2XL asked, “Give me what you think is a realistic pathway for an E. coli population to obtain a flagellum.”) No details on mechanisms, relevant statistics, etc….just make up a story we could have analyzed.

    Here is that recent conversation on UD where the hypothetical indirect pathway of the bacterial flagellum was discussed:

    The end of this conversation puts the problem in perspective:

    Other major points:

    Now who is doing the “wriggling”?

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