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Rethinking SETI’s Targets

Have you ever given any thought to intergalactic SETI? On the face of it, the idea seems absurd — we have been doing SETI in one form or another since the days of Project Ozma and without result. If we can’t pick up radio signals from nearby stars that tell us of extraterrestrial civilizations, how could we expect to do so at distances like M31’s 2.573 million light years, not to mention even the closest galaxies beyond? Herein lies a tale, for what intergalactic SETI exposes us to is the baldness of our assumptions about the overall SETI attempt, that it is most likely to succeed using radio wavelengths, and that it may open up two-way communications with extraterrestrials. It’s the nature of these assumptions that we need to explore today.

The Visibility of a Galactic Culture

Let’s suppose, for example, that Nikolai Kardashev’s thoughts about types of civilizations are compelling enough to put to the test. A Kardashev Type III civilization is one that is able to exploit the energy resources not just of its home star but of its entire galaxy. So unimaginably beyond our present capabilities is a Kardashev Type III that we scarcely know how to describe it, but it is within the realm of reason that signs of astro-engineering on this scale might be detectable in at least nearby galaxies if such a civilization had gone to work on them. And indeed, James Annis has made such a study, concluding that neither our Milky Way nor M31 or M33, our two large, neighboring galaxies, has been transformed by the work of a Type III civilization.

Image: M33, the Triangulum Galaxy. We’ve only begun to investigate whether nearby galaxies like this one might show signs of astro-engineering on a gigantic scale. Civilizations a billion years or more older than our own might be capable of feats detectable from great distance. Credit: Adam Block/NOAO/AURA/NSF.

It should hardly be necessary to point out how preliminary such results are, and how rare such studies have been. What’s striking about Annis (and related work by Richard Carrigan and P.S. Wesson) is that these scientists are pursuing ideas that are well outside the SETI mainstream. There is a new paradigm here, one that operates without any notion of ‘contact’ and subsequent exchange of ideas between civilizations. It is a search for artifacts, for artificial structure and signs of engineering. It is all about discovery. And just as we can have no two-way conversation with Mycenaean Greece as we dig for information about the era of Agammemnon, we may with this stellar archaeology discover something just as unreachable but likewise well worth the study.

Toward a Dysonian SETI

In a recent paper, Robert Bradbury, Milan Ćirković (Astronomical Observatory, Belgrade) and George Dvorsky (Institute for Ethics and Emerging Technologies) consider whether intergalactic SETI may be an example of what they call a ‘Dysonian’ approach to SETI, one that is a ‘middle ground’ between the traditional radio-centric view (with contact implications) and the hostile reaction of SETI detractors who see no value in the enterprise whatsoever and think the money better spent elsewhere. The nod to Freeman Dyson is based on the latter’s conjecture that a truly developed society would surmount the limits of planetary living space and energy by building a Dyson shell, capturing most or all of the energy from the star near which it lived.

A Dyson sphere immediately changes the terms of SETI because it is in principle detectable, but unlike nearby radio signals (either from a beacon or as unintentional ‘leakage’ from a civilization’s activities), a Dyson shell might be spotted at great astronomical distances through its infrared signature. Carl Sagan was one of the first to pick up on the idea and ponder its implications. Dyson was much in favor of attacking the question in a disciplined way, using our astronomical tools, as he once wrote, “…to transpose the dreams of a frustrated engineer into a framework of respectable astronomy.” And here again, we have seen attempts, especially by the aforementioned Richard Carrigan, to study infrared data for signs of such Dyson constructs.

The new direction in SETI that the three authors of the new paper champion is one that employs a broader set of tools. Rather than limiting itself to radio dishes or dedicated optical facilities, it broadens our workspace for extraterrestrial civilizations to include astronomical data that can be gathered in tandem with other research projects, scanning a far wider and deeper field. In the authors’ view, Dysonian SETI also takes into account new developments in astrobiology and even extends into computer science and the possibility of post-biological intelligence. They advocate a Dysonian SETI drawing on four basic strategies to supplement older methods:

  • The search for technological products, artifacts, and signatures of advanced technological civilizations.
  • The study of postbiological and artificially super-intelligent evolutionary trajectories, as well as other relevant fields of future studies.
  • The expansion of admissible SETI target spectrum.
  • The achievement of tighter interdisciplinary contact with related astrobiological subfields (studies of Galactic habitability, biogenesis, etc.) as well as related magisteria (computer science, artificial life, evolutionary biology, philosophy of mind, etc.)

The expansion of SETI into these areas would not replace ongoing SETI methods but would significantly expand the overall process in line with the great goal of learning whether other intelligent beings share the galaxy and the nearby universe with us. The paper offers more fruitful speculation than I can fit into a single entry, so we’ll be looking at these ideas over the course of the next few days. If there really is a Great Silence, to use David Brin’s phrase, these authors argue it’s one that we can only ponder usefully if we broaden our search toward the potentially observable achievements of cultures far more advanced than our own. That study has only recently begun.

The paper is Bradbury, Ćirković and Dvorsky, “Dysonian Approach to SETI: A Fruitful Middle Ground?” JBIS Vol. 64 (2011), pp. 156-165.


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  • ljk March 14, 2012, 23:22


    March 12, 2012

    BOK Globules –Leading Scientists Ask: “Could They be Prime Habitats of Advanced Machine-Based Civilizations?” (Today’s Most Popular)

    If AI-powered machines evolved, we would be more likely to spot signals from them than from the “biological” life that invented them.

    “But having now looked for signals for 50 years, we are going through a process of realizing the way our technology is advancing is probably a good indicator of how other civilizations – if they’re out there – would’ve progressed. Certainly what we’re looking at out there is an evolutionary moving target,” according to SETI Chief Astroniomer, Seth Shostak.

    Shostak believes that artificially intelligent alien life would be likely to migrate to places where both matter and energy – the only things he says would be of interest to the machines – would be in plentiful supply. That means the Seti hunt may need to focus its attentions near hot, young stars or even near the centers of galaxies.

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

    Data centers like this generate a lot of heat, and keeping them cool is a major challenge for modern computing. Intelligent computers would likely seek out a low-temperature habitat. Bok globules (image at top of page) are another search target for sentient machines. These dense regions of dust and gas are notorious for producing multiple-star systems. At around negative 441 degrees Fahrenheit, they are about 160 degrees F colder than most of interstellar space.

    This climate could be a major draw because thermodynamics implies that machinery will be more efficient in cool regions that can function as a large “heat sink”.

    A Bok globule’s super-cooled environment might represent the Goldilocks Zone for the AI powered machines, says Shostak. But because black holes and Bok globules are not hospitable to life as we know it, they are not on SETI’s prime target list.

    “Machines have different needs,” he says. “They have no obvious limits to the length of their existence, and consequently could easily dominate the intelligence of the cosmos. In particular, since they can evolve on timescales far, far shorter than biological evolution, it could very well be that the first machines on the scene thoroughly dominate the intelligence in the galaxy. It’s a “winner take all” scenario.”

    According to the British physicist Stephen Wolfram, intelligent life is inevitable. But there is a hitch. Although intelligent life is inevitable, we will never find it -at least not by looking out in the Milky Way. As evidence Wolfram points out In order to compress more and more information into our communication signals – be they mobile phone conversations or computer- we remove all redundancy or pattern. If anything in a signal repeats, then clearly it can be excised. But this process of removing any pattern from a signal make it look more and more random – in fact, pretty much like the random radio “noise” that rains down on Earth coming from stars and interstellar gas clouds.

    According to Wolfram, if someone beamed our own 21st-century communication signals at us from space we would be hard pressed determining whether they were artificial or natural. So what chance do we have of distinguishing an ET communication from the general background radio static of the cosmos?

    ET artifacts coordinated by computers would look far more like a natural artifact. It is easy to distinguish a technological artifact such as a car from a natural object such as a tree. The tree is far more complicated.

    But, says Wolfram,”this is simply because our technological artifacts are primitive. As they become more complex – with computer processors enabling them to make a moment-by-moment decisions – they will begin to look just as complex as trees and people and stars.” We have slim chance, he suggests, of distinguishing an ET artifact from a natural celestial object.

    If Wolfram is right and ETs are out there but we will not be able to recognize them – either in their communications or their artifacts – then of course they could be here in the Solar System and we would not have noticed.

    Wolfram thinks ETs will not want to travel to Earth – or anywhere else for that matter. In Wolfram’s view, everything in the Universe is the product of a computer program. In fact, he imagines an abstract cyber-universe of all conceivable computer programs, all the way from the simplest up to the most complex. This “computational universe” contains everything from the Apple Macintosh operating system to a programme for creating a faster-than-light starship

    Wolfram believes he has found nature’s big secret – how it generates the complexity of the world, everything from a rhododendron to a tree to a barred spiral galaxy by applying simple rules over and over again as a simple computer programs. Wolfram came to this remarkable conclusion in the early 1980s when he discovered that the simplest kind of computer program – known as a cellular automaton – can generate infinite complexity if its output is repeatedly fed back in as its input.

    Wolfram has found evidence that the kind of computer program that produces endless complexity can be implemented “not just systems of biological molecules but in all sorts of physical systems – chaotic gas clouds, systems of subatomic particles and so on. He concludes that all over the Universe life – though definitely not life as we know it – will spring up spontaneously. It is a fundamental feature of matter.”

    The existence of this computational universe is the crucial thing. But the reality is it would be it easier and more efficient for an ET civilization to stay at home and use a computer to search the computational universe for useful programs rather than try to get the same information by hunting for ETs to talk to among the 200 billion or so stars in the Milky Way. “It’s a simple numbers game,” says Wolfram.

    Everything is generated by computer program,”and that includes you and me,” says Wolfram. “Someone halfway across the Galaxy could have found the computer program for you and conversing with you at this very moment.”

    The Daily Galaxy via SETI and wolframscience.com