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SETI Beacons and Altruistic Aliens

by James and Gregory Benford

Interstellar beacons continue to draw discussion, and the Benford brothers now return with further thoughts on the matter in response to reader comments here. How to distinguish a beacon from a natural source, and why consider it in terms of cost? The answer is below, as is an interesting twist on the Fermi paradox.

We proposed making cost a useful, perhaps universal, standard because it is a quantitative constraint. Our aim is to help observers look for plausible beacons that may exist. Using transient events seen by observers is an economic way to ask these next, exploratory questions. Speculations always yield to data, and at its 50th anniversary SETI needs a vital data point: first detection.

In our latest work, we point out that researchers should be aware of the likely properties of beacons. In particular, beacons may mimic pulsars in repetition rate. But they would distinguish themselves in some way, such as amplitude modulation, varying pulse interval, frequency modulation, etc. And they may provide ‘enough’ pulses on a given target area for their artificial origin to be noticed.

While discussions of many social issues, particularly motivations, do provoke – they seldom illuminate. Are aliens beyond economic arguments? We call this the Altruistic Alien argument — that aliens of great ability, near-infinite resources and benign intent will transmit to us without taking any consideration to the cost (which would be very high in our terms, especially for long range). They will make everything easy for us. And an omni-directional Beacon, radiating at the entire galactic plane, for example, would have to be enormously powerful and so very expensive.

On this site, several comments speak of robot manufacture, future economic miracles, etc. – but forget that the idea of exponentially falling costs in future technologies has an observable test: If vastly rich aliens can easily afford beacons of the sort we seek – microwave or IR or even visible – then where are they? If there are Altruistic Aliens, where is the evidence? They certainly haven’t made beacons that are apparent in our sky. So, the rich aliens argument fails the test.

This Fermi question limits useful speculations. Whether alien motivations will resemble ours we’ve dealt with, but think secondary – all motivations meet constraints, and biological evolutionary theory suggests that cost (economic cost, environmental, etc.) is a universal constraint.

We think that, if they are social beings interested in a SETI conversation or passing on their heritage, they will know about tradeoffs between social goods, and thus, in whatever guise it takes, cost. But what if we suppose, for example, that aliens have very low cost labor in the form of automata? With a finite number of automata, i.e., slaves, you can use them to do a finite number of tasks. And so you pick and choose by assigning value to the tasks, balancing the equivalent value of the labor used to prosecute those tasks. So choices are still made on the basis of available labor. The only case where labor has no value is where labor has no limit. One might think that might be if aliens have limitless armies of self-replicating automata, but such labor costs something, because resources, materials and energy, are not free.

Our point is that all SETI search strategies must assume something about the beacon builder, and that cost may be a near-universal driver for alien attempts at interstellar communication.

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Comments on this entry are closed.

  • Eniac April 12, 2010, 10:10

    On this site, several comments speak of robot manufacture, future economic miracles, etc. – but forget that the idea of exponentially falling costs in future technologies has an observable test: If vastly rich aliens can easily afford beacons of the sort we seek – microwave or IR or even visible – then where are they? If there are Altruistic Aliens, where is the evidence? They certainly haven’t made beacons that are apparent in our sky. So, the rich aliens argument fails the test.

    I think it is a bit twisted to take the absence of alien communications to mean that technology costs will not fall exponentially (did I misunderstand the argument?). There are, after all, other explanations, such as there being no aliens or they not wanting to communicate. Thus, this is a very bad “test” of the idea of falling costs.

    So far, many technology costs have fallen exponentially (price for a transistor, anyone?), and there is every reason to think that they will continue to do so. The advent of self-replicating automata and the utilization of space will do the same thing for energy and raw materials, at least until we get to the stage where we can process a significant fraction of all matter in our solar system.

    On the other hand, no matter how far costs fall, it is always good to do more with less (I think this is the universal truth at the bottom of this), so the core of Benford’s arguments remains standing.

  • Eric April 12, 2010, 12:42

    Maybe of interest:
    http://web.archive.org/web/20040207175652/http://www.transhumanist.com/Kansa-Fermi.htm

    This was a fun paper, but never got around to properly exploring the math (which is probably quite wrong and needs a much more expert hand), nevertheless, some of the argument can be useful here.

    Essentially, the argument goes like this. In some situations, competition may lead to costly displays (pyramids, peacock feathers, excesses of the French nobility). “Wasting” resources (energy, labor, materials) on expensive displays may be an important competitive strategy. This kind of thing may not work in all circumstances, but it seems to have evolved commonly enough in all sorts of ecological settings, suggesting that it may likely be a feature even in alien ecologies and societies.

    So, wasting energy on beacons may be motivated by more than altruism, and may even sometimes signal some types of intense competition.

  • kurt9 April 12, 2010, 14:05

    Forget about beacons and other signals. It make more sense to me to look for artifact, past and present. Are there “funny-looking” stars and other astronomical phenomenon that cannot be explained by natural causes?

    Perhaps aliens existed a long time ago, but disappeared (presumably went post-physical). Unexplained nuclear waste or metallurgical products either on Earth or in other parts of the solar system. What about those “natural” nuclear reactors in Africa, the ones that are 1.6 billion years old? Perhaps these are the left overs of nuclear power plants that were abandoned when the aliens left. Does the asteroid belt or outer plants appear to be “harvested”? Perhaps there is a 1 billion year old derelict space probe in the outer solar system or kuiper belt. What about the moon? Aliens visiting Earth a billion years ago would have left something on the moon, even if its nothing more than some kind of telemetry device.

    It seems to me that these are the things SETI should be looking for, rather than transmission signals. Maybe the aliens no longer use electromagnetic waves for communication. Maybe they use HFGW or some other technology instead.

  • Adam April 12, 2010, 15:32

    Hi kurt9
    The Oklo ‘reactors’ really are just uranium chemistry in action, nothing artificial about them at all. Self-limiting because every time they got too hot the water vanished and the ‘reactors’ lost their moderator.

    One thought about technological ‘end-points’ that occurred to me is that ETIs at the level of Matrioshka brains would be able to easily monitor all stars in the galaxy via gravity lens observatories, thus they’d KNOW if there was Someone worth talking to across the Galaxy. No need for beacons then.

    Similarly a self-replicating technology enables a Galaxy-spanning Web of monitoring Bracewell probes that can spy and report at leisure – again using gravity lensing for signal strength. If Charles Lineweaver’s now venerable study about the average age of habitable planets is correct then the Galaxy is well covered already by ETI Webs and Brains – we’re in the ‘Post-SETI Era’ after Everyone has beaconed and explored.

  • Bounty April 12, 2010, 18:56

    “So far, many technology costs have fallen exponentially (price for a transistor, anyone?), and there is every reason to think that they will continue to do so.” -Eniac

    Many computer experts predict that the costs to produce smaller features are rising faster than the processes are shrinking (end of Moore’s law.) Many costs have not gone down exponentially. I think predicting that there are no aliens or that all aliens that could build beacons choose not to, is as much of a random guess as predicting the economies of those aliens (or us in 500 years.)

  • Duncan Ivry April 12, 2010, 18:58

    Again a very interesting article by the Benfords — I really like it, thank you.

    An economic constraint we should consider is the law of diminishing marginal returns: “We will get less and less extra output when we add additional doses of an input while holding other inputs fixed.” (just from Wikipedia; but I have economic literature about it.) As far as I know, it’s an open question, whether, why, where etc. this law is true for our economy on earth, but there is a lot of evidence supporting it. The condition “while holding other inputs fixed” complicates considerations, but in spite of that, the following is plausible.

    If the above law is true for an alien economy, it could very well limit the production of interstellar beacons.

    After having produced a certain amount of beacons and after having refined them to a certain degree, the existing producers of interstellar beacons — and the potential new producers watching the interstellar beacon market — will find, that for the next new and/or more refined interstellar beacon total investment increases but total return on investment decreases. Because of this at some point in time they will not produce more interstellar beacons and no new producer will enter the interstellar beacon market. The number of interstellar beacons the alien economy uses will remain constant, and there will only be production of replacement parts. Because, as I assume, the law of diminishing marginal returns is true for the production of replacement parts too, this will also end some day, and then …

    By the way, the same could be true for those legendary self-replicating, interstellar probes which have swamped our galaxy already. Perhaps they haven’t been produced in such large quantities.

    If this sounds crazy — there have been considerations, that the law of diminishing marginal returns even can be applied to technical progress in total. Then at some time in the future technical progress will slow down and eventually stop. So there will be no warp drive just because of this!? Shudder!

  • Duncan Ivry April 12, 2010, 20:32

    Regarding the development of costs or prices over time …

    Eniac: “So far, many technology costs have fallen exponentially (price for a transistor, anyone?), and there is every reason to think that they will continue to do so.”

    Is this really true? (Transistors are out, as far as I know.)

    The first problem is how to measure. Costs — or better: prices — are nothing absolute, but can only be measured relative to something else. A usual approach is asking how long a, say average, member of the economy has to do payed work until he/she can buy a certain good, e.g. a bred, a shirt, a car, a computer, or an interstellar beacon. By the way, doing it this way, inflation (a rise in the general level of prices of goods and services) is a minor problem — but no non-problem.

    What are the facts? Sorry, I do not have the time to wade through literature and databases. But, as far as I have seen in publications here and there over the years, in western societies prices of many products, especially technical ones, have indeed fallen for some considerable time now, say: after World War II, if measured with the approach from above. But “exponentially”? It’s difficult to decide.

    Let us take something which, with respect to sophistication, may be the present-day equivalent of a future interstellar beacon: a particle accelerator. The large hadron collider could only be built because several nations threw there money together, whereas in the past one nation alone has been able to build an accelerator. It’s difficult to decide whether the price for a really sophisticated high-tech product class like “particle accelerators” did rise or fall. Yes, we get more accelerator for more money, but I don’t know where to get “real” numbers from. Again: “exponentially” is questionable.

    There is an interesting long range example. About 2000 years ago a certain guy got thirty pieces of silver, for which he could buy a donkey at the time. Today, according to historians and economists, these pieces would be, over all economical ups and downs, just the money to buy a small car — the modern equivalent of a donkey. So the “real” price of this technical equipment may — may! — not have changed much over 2000 years.

    Is the exponential drop of tech-prices something like an urban legend?

  • Lionel W April 12, 2010, 20:42

    Life as we know it, is more likely to leave interstellar graffiti, than any kind of beacon.

    Upon pondering the form that such graffiti would take, I remembered the ‘knobula’ from Amanda Bauer’s Dirt Space News

    http://2.bp.blogspot.com/_YtxGNf8GgRA/S5ouOMMxFiI/AAAAAAAAEmE/TIgKC5epJuo/s1600-h/cone_nebula_cheeky.jpg

    That, ladies and gentlemen, is our beacon!

  • Eniac April 13, 2010, 0:14

    the modern equivalent of a donkey. So the “real” price of this technical equipment may — may! — not have changed much over 2000 years.

    You are pricing apples and oranges here, or rather donkeys and cars. These are different items, and a car has quite a lot more value, obviously (I give you either this donkey, or this Porsche. Which one are you going to take home today?). Silver, furthermore, has less value today than it used to, and cars were literally priceless 2000 years ago.

    As things get less expensive, and we still work all day, of course we need to buy more things, or more valuable things. 20 years ago a cell phone would have been a priceless treasure, now we are throwing them away after a year or two of use. Go back a little further, the same goes for watches. Family heirloom to $5 Rolex on Canal Street, in less than a hundred years.

    And all that is still without substantial super-automation, i.e. before the advent of self-replicating machinery. The future is going to be very exciting.

  • tesh April 13, 2010, 3:05

    Is it that the “cost” of tech, that are falling or that the rate at which tech is “improving” that are falling? I think that there is confusion here between the two.

  • Ronald April 13, 2010, 6:34

    Interesting view on Fermi. However, I tend to believe that a much more likely reason for Fermi’s paradox is answered by Occam. With reference to our recent thread on estimated number of habitable earthlike planets in our MW galaxy (Habitable Planets: Working the Odds, https://centauri-dreams.org/?p=11625&cpage=1#comments): if the total number of (potentially) habitable earthlike planets in our galactic disk/Galactic Habitable Zone is on the order of some 50 – 100 million and 10 – 20% of these possess complex (higher, multi-cellular, specialized organs) life, then that is very nice from a purely astro-biological point of view as well as from the point of view of (future) available real estate combined with minimal competition, but actually very meager with regard to prospects for advanced technological civilization.

    It is becoming a sobering mantra, but advanced technological civilizations must be exceedingly rare in our galaxy.

    Now, the Andromeda galaxy is entirely different story altogether, of course. Andromeda is so habitable and full of main sequence sunlike stars, that it is commonly accepted by now that that galaxy is most probably swarming with advanced civilizations. The only problem is that they are rather galacto-chauvinistic and look down upon us backward Milky Wayans to the extent that they actually take utmost care to block any communication leakage in our direction ;-)

  • Eniac April 13, 2010, 9:30

    Is it that the “cost” of tech, that are falling or that the rate at which tech is “improving” that are falling? I think that there is confusion here between the two.

    It is both. That heirloom watch that once cost someone a year’s wages needs to be wound every day and loses a few minutes each day. The $5 watch you buy at Walmart runs for a year and keeps time within seconds in that period. So, you pay less, and get more. Not just a little bit, but orders of magnitude, each. It is a pretty good deal.

    With most things we buy today, it is even better, because they didn’t exist at all a few decades ago. You can get a Terabyte of disk space for less than $100 today. 5 years ago, you’d have to have a roomful of very expensive machines. 20 years ago, you would have gotten blank stares at the mention of it: “Terabyte? Ummmh, let’s see, kilo-, mega-, ….?”. 50 years ago: “Disk space? Is that a shed for sports equipment?”

    And the trend is definitely accelerating. Will it keep going forever? Probably not. But it can keep going for quite a while, and accelerate further. I suspect that after whatever stops it, “cost” is going to be an antiquated and irrelevant concept.

  • Duncan Ivry April 13, 2010, 15:04

    Eniac: “You are pricing apples and oranges here, or rather donkeys and cars. These are different items, and a car has quite a lot more value, obviously (I give you either this donkey, or this Porsche. …)”

    I quote those historians and economists, who invested quite a lot of sophistication in researching this. Above that, the modern equivalent — more exactly the functional equivalent — for the donkey, they said, is a *small* car. A Porsche is definitely not a small car.

    “Silver, furthermore, has less value today than it used to …”
    The historians and economists *did* consider all the ups and downs of economy over 2000 years, and, based on this, they carefully calculated time series about prices, and they asked carefully what somebody could buy for thirty pieces of silver 2000 years ago and what someone can buy today. Here the pieces of silver are not just metal, they are money, as a dollar note is, which is not only a cheap piece of paper. The dollar note has *not* lost value because paper is cheaper.

  • tesh April 13, 2010, 15:16

    I agree. Eventually we will have move away from the concept of money. We will either out live it or it will consume us.

  • Duncan Ivry April 13, 2010, 16:30

    tesh: “Is it that the “cost” of tech, that are falling or that the rate at which tech is “improving” that are falling?”

    We observe different developments of prices and different developments of technical progress for different technical products. Some examples …

    The technical progress of the functionality of computer chips grows at a rate, which is remarkably constant over several decades including the most recent past — this is a modern version of Moore’s law. Still nobody knows, whether it will be possible to continue. And a constant rate of improvement implies an exponential function of time.

    Some peripheral computer components do not show this picture, e.g. hard drives — yes, hard drives, because capacity is not the whole picture –, keyboards, printers, projectors. Here technical progress has been and still is slower, i.e. below exponential, a falling rate. But below exponential doesn’t have to be bad.

    Well, and a rising growth rate of technical progress, i.e. above exponential? I have never heard about something like that, and if we don’t get it with all the effort and cleverness going into computer chips, I think, we don’t get it anywhere else.

    Now prices of technical products … which, as you remember, can only be measured relative to something else.

    The prices of computers did fall, if you take the prices nominally as you read them on the price tag. Today you can buy computers, even improved ones, for nominally less money. If we go from nominal prices to prices indexed by the time we have to work for a certain, constant amount of money, the above statement remains true.

    Is the same true for really sophisticated, big, high-tech products like particle accelerators (or interstellar beacons)? More and more countries have to put their money together in order to produce more and more sophisticated devices. More and more people have to do payed work in order to achieve this. So, it may very well be, that real prices did rise — and did rise about the same way functionality grows.

  • Ron S April 13, 2010, 19:37

    Then: labor cheap; things expensive.
    Now: labor expensive; things cheap.

    Then: most (currently existing) things didn’t exist.
    Now: lots of new things; and while the old things mostly still exist, their utility is entirely different, e.g. a donkey is more likely to be a pet than a beast of burden.

    A better measure is quality of life. We live longer, we have more leisure time, and there are more choices of what to do and where to go. In none of this do monetary units matter, which is unsurprising since they are no more than representations of transferable wealth whose context is constrained to a specific time and place.

    There’s a reason why economics is called the dismal science.

  • Eniac April 13, 2010, 20:25

    Duncan:

    Here the pieces of silver are not just metal, they are money, as a dollar note is, which is not only a cheap piece of paper. The dollar note has *not* lost value because paper is cheaper.

    For cost comparisons across time, denominations of money are absolutely useless, and things like silver and gold only slightly less so. Food and energy are a little better, because they have enduring, non-fictional value. The best measure, as has been said, is the duration of work needed for the average worker to “earn” the thing you are trying to cost.

    The other thing that has to be considered is the intrinsic value, or “usefulness” of the goods. A car is MUCH more useful than a donkey, even a small one. Try to commute to work on a donkey, and you will realize that. Thus, a car is more valuable than a donkey. Yes, the car is the “equivalent” of a donkey at different times, but that does not detract from its objective superiority. You can always determine relative value by giving people a choice of gift. The thing chosen by more people is the more valuable one, practically by definition.

    If you can show me that 2000 years ago you could buy a donkey for 2 months wages, I will concede you are right. How much silver you need to buy one is really not relevant. Neither are the credentials of the historians and economists who came up with this donkey story. My guess is, 2000 years ago, a donkey constituted quite a bit of wealth, costing much more than 2 months of average wage.

  • Eniac April 13, 2010, 20:49

    Some peripheral computer components do not show this picture, e.g. hard drives — yes, hard drives, because capacity is not the whole picture –

    I do not follow this. Hard drives have been exponentially rising in capacity twice as fast as Moore’s law, AFAIR. What do you mean by “not the whole picture”? Higher capacity is already good enough, other things add even more value, such as better access times and higher data throughput.

    If something goes for transistors, disk space, cars (or donkeys) and watches, I think it is pretty universal, economically speaking. Consider that most of the things that do not get better fast, such as food, have shrunk to a very small share of the economy.

  • Duncan Ivry April 13, 2010, 21:27

    Ron S: “Now: … e.g. a donkey is more likely to be a pet than a beast of burden.”
    Eniac: “A car is MUCH more useful than a donkey, even a small one.”

    Don’t be so sure! I assume you both are inhabitants of the first world. In the second and third world — i.e. for most people on earth — things are still different. Donkeys are tools. People are in urgent need of donkeys and certain other animals in order to be able to survive. Those animals are still “quite a bit of wealth”.

    There are many terrains where donkeys (or mules) are more useful than cars. There are terrains where cars are not at all useful, but only donkeys (or mules) are. “Try to commute to work on a donkey” in the mountains of Peru or Afghanistan “and you will realize that.”

    Seeing donkeys and other animals as pets, friends, brothers and sisters, related souls, and the like is historically a more recent development. For many people on the world this still would be luxury — and dangerous.

    Well, I started my comments with economic considerations relevant for aliens and beacons, but with the donkey-technology — which was an argument of minor importance — we got a bit off topic, I think. As far as I’m concerned, I will not continue. Thank you for participating.

  • Eniac April 13, 2010, 21:59

    Ron S:

    In none of this do monetary units matter, which is unsurprising since they are no more than representations of transferable wealth whose context is constrained to a specific time and place.

    Quite right, except for the mention of “place” at the end. It is the very purpose of money to provide a measure of value that is transferable from one place to another, and it works well for that.

    Transfer through time is different. It works within limits, which leads to the concept of interest. After a decade or two, though, the transferability breaks down, because of the unpredictability of inflation.

  • Matt April 14, 2010, 12:28

    “On this site, several comments speak of robot manufacture, future economic miracles, etc. – but forget that the idea of exponentially falling costs in future technologies has an observable test: If vastly rich aliens can easily afford beacons of the sort we seek – microwave or IR or even visible – then where are they? If there are Altruistic Aliens, where is the evidence? They certainly haven’t made beacons that are apparent in our sky. So, the rich aliens argument fails the test.”

    This kind of argumentation has always infuriated me because it implies instant gratification.

    Certain elements not produced through stellar thermonuclear fusion seem to be needed for complex life, which limits how far back a planet that could support complex life could form. Then the life has to evolve over a billion or so years to the point where there are intelligent life forms with large scale social organization. Then they have to develop technology and industry and actually get to the point where they are capable of transforming a star into a beacon. Then, they have to get to the star, which is probably thousands of lightyears away because pulsars cause property deppreciation like nothing else.

    On Earth, human civilization is approximately 6000 years old and industrialization only began about 300 years ago. Right now we can barely put crewed spacecraft into deep orbit. So an alien civilization capable of turning a star into a beacon would probably have to last several thousand more years and the journey to the star would take thousands of years.

    Taking all this together seems to me to be good reason to believe that the closer an older alien civilization gets to being able to turn a star into a beacon, the closer in time they would be getting to be contemporanious with us, meaning that we wouldn’t be able to see a beacon yet if one did exist.

  • Ron S April 14, 2010, 15:45

    Duncan: “Don’t be so sure! I assume you both are inhabitants of the first world. In the second and third world — i.e. for most people on earth — things are still different.”

    Eniac: “Quite right, except for the mention of “place” at the end.”

    Well, there you go. That is exactly the reason why I mentioned place, which Duncan chose to avoid in order to lecture me on the obvious. Duncan, I am not blind; I know very well the state of the world. Your retort fails to counter my argument.

  • Duncan Ivry April 14, 2010, 16:44

    Now we are back to interstellar beacons.

    Matt: “This kind of argumentation has always infuriated me because it implies instant gratification.”

    I don’t see why the quoted argumentation implies *instant* gratification. Please explain.

    Matt: “they” (the aliens) “are capable of transforming a star into a beacon … they have to get to the star, which is probably thousands of lightyears away …”

    As far as I can see, the Benfords and others did not necessarily consider turning a *star*, especially a pulsar, into a beacon, but in the first place they meant an artificial device orbiting the alien’s planet or sun. This should be easier, and the aliens don’t have to travel thousands of lightyears.

  • Eniac April 14, 2010, 19:27

    Don’t be so sure! I assume you both are inhabitants of the first world. In the second and third world — i.e. for most people on earth — things are still different. Donkeys are tools. People are in urgent need of donkeys and certain other animals in order to be able to survive. Those animals are still “quite a bit of wealth”.

    That some areas and people have unfortunately not benefited much from the mind-boggling technological/economic progress we are talking about does not mean it doesn’t exist.

    That said, in those places you mention, if you were to really go there, you would see plenty of motorcycles, laptops and cell phones there. Donkeys too, but that is just because there wasn’t enough money for roads, yet. Probably because guns and bigger houses for corrupt politicians had priority. And guess what, those motorcycles and cell phones would fetch roughly the same amount of dollars as they do in more developed areas, give or take some transportation costs (on the back of donkeys, perhaps). Because dollars have the same value everywhere.

    The mountains of Peru and Afghanistan are no more rugged than the Rockies or the Alps, yet you can cross the latter several orders of magnitude faster. This is because there are roads, viaducts, tunnels and cars. Another example of the enormous, and completely objective, economic advances that have been created by technology in just the last century.