≡ Menu

Another Search for Kardashev Type III

I have no idea whether we would be able to recognize a Kardashev Type III civilization if we saw one, but the search is necessary as we rule out some possibilities and examine others. As we saw yesterday, the Glimpsing Heat from Alien Technologies project at Penn State has examined data on 100,000 galaxies, finding 93 with mid-infrared readings that merit further study. One thing that we, operating with what we know about physics, would expect from a super-civilization is the production of waste heat, in the temperature range between 100 and 600 K, and that’s why previous searches for Dyson spheres have gone looking for such signatures.

But Kardashev Type III is an extreme reach. We’re talking about a civilization capable of using the energies not just of its own star but of its entire galaxy, and just how this would be done is a question about which we can only speculate. As Erik Zackrisson (Uppsala University) and colleagues do in a new paper that balances nicely against Michael Garrett’s recent study. The Zackrisson paper posits Dyson spheres as one way to harvest radiation energies, and takes as its inspiration a 1999 study by James Annis that considers this method in relation to detecting a galaxy-spanning civilization.

A Dyson sphere would partially shroud a star or, in its extreme form, completely surround it, making vast amounts of radiant energy available for the purposes of its builders. Annis wondered how a civilization building Dyson spheres throughout a galaxy would affect the light output of the galaxy. To study the matter, he suggested using the so-called Tully-Fisher relation, the correlation (in spiral galaxies) between galactic luminosity and rate of rotation.

Tully-Fisher_relation

Zackrisson follows Annis’ lead, knowing that if you can determine a galactic rotation velocity, you can use the Tully Fisher relation to come up with its intrinsic brightness. since the optical brightness of a galaxy shows a consistent relation to the maximum rotation velocity and radius of the galaxy. Annis, using a sample of 137 galaxies, looked for candidates that were darker than they should be, finding no outliers in his admittedly limited dataset. Michael Garrett also used a useful relation, in his case between the mid-infrared output of a galaxy and its radio emissions, one that has been shown to hold over a wide range of luminosity and redshifts, to look for cases where the relation failed.

Image: The Tully-Fisher relation shows that rotation curves can be correlated with luminosity. The higher the luminosity, the higher the maximum rotational velocity.

If there is a Kardashev Type III civilization building Dyson spheres on a galactic scale, its astroengineering projects should not affect the gravitational potential of the galaxy, but they should decrease the total optical luminosity, thus making the galaxy an outlier that would appear less luminous than it should. Zackrisson used Tully-Fisher on a sample of 1359 spiral galaxies drawn from a catalog of galaxies produced in 2007 by Christopher Springob and colleagues. The criterion for KIII candidate galaxies was the one used by Annis, that candidates should be ≥ 1.5 magnitudes below what would be expected from Tully-Fisher (the reasons for the choice have to do with limiting spurious detections and are explained at some length in the paper).

As with Michael Garrett’s study, we find little evidence of Kardashev Type III in the results. The conservative upper limit on the fraction of local disks that meet the criteria for a candidate KIII galaxy is ≲ 3%. But we need to drill down into this. Let me quote from the paper:

In this sample, a total of 11 objects are found to be significantly under-luminous (by a factor of 4 in the I-band) compared to the Tully-Fisher relation, and therefore qualify as Kardashev type III host galaxy candidates according to this test. However, by scrutinizing the optical morphologies and WISE 3.4–22 µm infrared fluxes of these objects, we find nothing that strongly supports the astroengineering interpretation of their unusually low optical luminosities.

So we do have a few anomalous galaxies that evidently owe their peculiarities to astrophysical causes not related to astroengineering on a K-III scale. The paper continues:

Hence, we conclude that their apparent positions in the Tully-Fisher diagram likely have mundane causes, with underestimated distances being the most probable explanation for most of the candidates. Under the assumption that none of them are bona fide KIII objects, we set a tentative upper limit of ≲ 0.3% on the fraction of disk galaxies harbouring KIII civilizations.

Hubble_view_of_barred_spiral_galaxy_Messier_83

Image: This Hubble image shows the scatterings of bright stars and thick dust that make up spiral galaxy Messier 83, otherwise known as the Southern Pinwheel Galaxy. One of the largest and closest barred spirals to us, this galaxy has hosted a large number of supernova explosions, and appears to have a double nucleus lurking at its core. What we have yet to find in galaxies like these is any sign of KIII civilizations. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgement: William Blair (Johns Hopkins University).

Does this mean that galaxy-spanning civilizations do not exist? The answer is no: The paper examines a specific scenario, that such civilizations would construct myriad Dyson spheres to harvest radiation energy, and that the waste heat of these constructions would be observable. We are a species whose experience of technology is negligible compared to a KIII culture, so we cannot know what kind of options they would have available after millions of years of technological development. All we can say for sure based on a study like this is that there is no evidence of massive deployment of Dyson spheres in any of the galaxies studied.

I don’t say this to in any way minimize the value of such work. We can’t know if something is there unless we look for it. We keep looking, then, while trying to imagine what civilizations far in advance of our own might do to use the maximum energy available to them. Ruling out one scenario is cause for a re-calibration of our assumptions and a continuing search.

The paper is Zackrisson et al., “Extragalactic SETI: The Tully-Fisher Relation as a Probe of Dysonian Astroengineering in Disk Galaxies,” in press at The Astrophysical Journal (preprint). The Annis paper is “Placing a limit on star-fed Kardashev type III civilisations,” JBIS 52, pp.33-36 (1999).

tzf_img_post

Comments on this entry are closed.

  • ljk September 24, 2015, 9:44

    Another award-winning scientist says there are likely no aliens in the Milky Way galaxy, so he must be correct:

    http://www.scmp.com/news/hong-kong/health-environment/article/1860781/no-ones-out-there-shaw-prize-astronomy-winner-says

    With all due respect, I do not care how smart this guy is in other areas of astronomy and science, his views on SETI are not terribly sophisticated. Why haven’t we detected a signal? Well, let us start with the history of SETI itself, which has only been going on since 1960. Most searches have been in the radio realm, are short in duration, small in scope, and in many cases were token efforts.

    Then we have the Milky Way galaxy itself, which is composed of 400 billion star systems across 100,000 light years. Human civilization has only been “leaking” electromagnetic radiation into the Milky Way for just over a century and most of those signals are weak. The few serious METI efforts are either probe-based and those are just barely past the Sol system planetary boundaries or they were radio messages aimed at specific star systems and will take decades to millennial to reach their targets, forget whether anyone is there to detect and respond to them. So I would say it is way too early to determine if we are alone in the Universe or not, even though some folks still seem to think humanity is the focus of existence and everyone wants to signal us or visit.

    Boruki’s thoughts remind me of Stephen Hawking’s views on visiting ETI, which are a scenario right out of the 1996 film Independence Day. Both gentlemen are smart, it is just that when it comes to speculating on alien life and minds they are on the same playing field as just about everyone else. Even Albert Einstein was a product of his era: He thought there were intelligent beings on Mars and considered signalling them with optical messages back in 1937.

  • James Stilwell September 24, 2015, 10:25

    Judgements made regarding M 83 are from 14.7 million years ago…
    We know that life undergoes radical change in as little as 3 million years…
    The main constant is the unchanging dance of the atoms…
    Max Planck is attributed to saying in a lecture that was given in Florence that,
    “As a physicist, that is, a man who has devoted his whole life to a wholly prosaic science, the exploration of matter, no one would surely suspect me of being a fanatic. And so, having studied the atom, I am telling you that there is no matter as such. All matter arises and persists only due to a force that causes the atomic particles to vibrate, holding them together in the tiniest of solar systems, the atom. Yet in the whole of the universe there is no force that is either intelligent or eternal, and we must therefore assume that behind this force there is a conscious, intelligent mind or spirit. This is the very origin of all matter.”
    Source of this quote is supposedly from Wolfgang Pauli
    It is possible that KIIIs will move on into the multiverse…
    And we are left with nothing to observe…
    Looking back in time 14.7 million years ago M-83 KIIIs may have left our universe long ago…
    Clarke suggests this will happen to us in his book, The City and the Stars…

  • Brian McConnell September 24, 2015, 10:25

    I’ve been following the news about the KIII surveys like GHAT. An obvious explanation for the lack of them is that they don’t build dyson spheres, but rather structures that are more diffuse.

    The assumption around KI-KIIIs is that they are on an exponential growth curve. OTOH, if they are content to live of a tiny fraction of the energy of each star, which is still a huge amount, they would effectively be invisible, with no measurable decrease in lumosity or IR excess.

    Steady state economies will also be stable long-term, whereas those predicated on continuous expansion are not (and are prone to catastrophic crashes when they hit resource bottlenecks).

    Personally I think KIIIs are rare or non-existent, but if they do exist, they won’t necessarily be observable at the macro scale.

  • Michael Michaud September 24, 2015, 12:20

    Do all Centauri Dreams readers buy the argument that more technologically advanced societies will relentlessly expand their use of energy and radiate colossal amounts of waste heat? This sounds like another example of the fallacy of relentless, uninterrupted trends.

  • CharlesJQuarra September 24, 2015, 12:51

    I’m utterly unconvinced by the discrimination capability of the 3.4–22 µm mid-infrared region.

    Landauer’s principle suggests that optimal energy efficiency of computation occurs as close as possible to cosmic background temperature. So the really interesting regions of the spectra lie precisely between 50 µm and microwaves, which is the far-infrared, or THz region of the spectra

    This region of the spectra is nearly invisible from Earth’s atmosphere: the thermal radiation of the atmosphere peaks precisely in this region. The only observatory is located in Antartica and doesn’t have enough size to resolve individual galaxies

    WISE and Spitzer also come short on these regions of the spectra. It is no exaggeration to say that we are nearly blind at the moment in the THz region, which is precisely the region of the spectra that is most interesting for KIII civilizations

  • Alex Tolley September 24, 2015, 13:22

    In some respects, this result is encouraging. It suggests that IF there are KIII civs out there, they no longer need to expand up to the limit of their galaxy’s energy production then have to try to transition to a no growth civilization. They must have found another way, which is encouraging, unless that other way is to return to nature and live without economic growth.

    The other encouraging thought is that we may indeed be alone, or at least not facing a universe of unbelievably large and powerful civilizations. This might allow us to expand into our galaxy without encountering any predatory species. We would then be responsible for greening the galaxy, at least on habitable worlds without existing life.

    But as ljk says, we really don’t have enough data to make pronouncement about ETIs. Unless we get a lucky hit from SETI, we may have to wait until far in the future when our advanced telescopes and interstellar probes have explored at least our region of the galaxy and reported home.

  • Alex Tolley September 24, 2015, 14:06

    @Michael Michaud – obviously not, and for a variety of reasons. The more interesting question is when do civs generally stop expanding in size and energy consumption? We have talked about creating Dyson swarms around sol as we expand our economy. But will we in practice? Is there some scientific or technological issue that occurs long before that happens that heads us off from doing that?

  • Jeff Sheets September 24, 2015, 14:15

    Seems to me that by definition a KIII civilization has technology that we don’t understand or even recognize. Their system would likely be designed to conserve or use whatever energy is available. Why would they allow waste heat? They are most likely turning it into some other type of energy and wasting very little; making it very difficult to identify them. I agree with CharlesJQuarra in that we should be looking for something that is in the same freq range as cosmic background radiation. Possibly the “only” radiation would be communications. Shouldn’t we be looking at dark matter and dark energy? What if a KIII civ is only identified by a distinct lack of emissions?

  • galacsi September 24, 2015, 14:48

    I do not want to be too negative, but I can not help but point out that these Kardashev’s stories run on solar energy and ignore nuclear energy and specifically nuclear fusion.Or any other unknown way of powering civilized life.

    These K civilisations can only harvest energy and cannot produce it ! And their unique purpose in existence seems to multiply like rabbits !

    So IMO this is bad Sf and a loss of time.

  • Dave Moore September 24, 2015, 15:23

    I would point out that there is a big difference between a galaxy spanning civilization outputting KIII levels of energy, as say vast numbers of KII civilizations, and harnessing KIII levels of energy. The only way this would be practical would be with faster than light travel. Otherwise, you are looking at project lead times of thousands of years.

  • Michael September 24, 2015, 15:26

    If we look at all these galaxies we are looking into the past, so all we can say at the moment is that there are no advanced societies, KIII’s, out there that we detect with our current capacities. And as we go further into the past are the materials such as sufficient carbon, our type of life for now, available through star formation and destruction in these galaxies.

    Advanced societies may have tapped their galaxies central black hole for energy as more viable than tapping every star they come across as the problem with processing waste heat is that it might just not be worth it beyond a point. After all control the central black hole and you have enormous potential not only as a weapon but to see almost everywhere and have the ability to travel between galaxies.

    They could also use the Dyson sphere concept to increase the life span of their stars, if a significant amount of the stars light or waste heat is reflected back it would cause the stars outer layers to expand placing less pressure on the core and regulate the stars fuel consumption and therefore lifespan.

    @Jeff Sheets

    ‘I agree with CharlesJQuarra in that we should be looking for something that is in the same freq range as cosmic background radiation. Possibly the “only” radiation would be communications. Shouldn’t we be looking at dark matter and dark energy? What if a KIII civ is only identified by a distinct lack of emissions?’

    There are two problems here that I can see, one trying to separate the CBR noise from the ‘signal’ would nigh on be impossible. And the second is that dark matter and energy are exactly that ‘dark’ we currently can’t detect it visually but only through the interaction via gravity.

    @Michael Michaud

    ‘Do all Centauri Dreams readers buy the argument that more technologically advanced societies will relentlessly expand their use of energy and radiate colossal amounts of waste heat? This sounds like another example of the fallacy of relentless, uninterrupted trends.’

    I doubt a civilisation will expand at such a great unrestricted rate, infighting has occurred on a regular basis amongst humans for as long as we have been around, they may be predatorily based just like us.

  • Harold Daughety September 24, 2015, 15:35

    @Michael Michaud – I do not for many often stated objections. The only reason to do so that I have seen is human hubris, and there are no humans out there.

    I fear that science fiction is misleading: It is fiction, and all of humanity’s stories are about humanity. All sci-fi intelligent creatures, as presented in rational human stories, mirror humanity in a narrow slice of good an evil.
    We cannot imagine intelligence different from ours. I doubt we ever will be, and thus we will not recognize an ET if we ever meet one.

    The arguments I have most often heard elsewhere that denies intelligent life elsewhere in the galaxy are religious, that Man is the ultimate creation. My long- dead father summed up the folly of the effort: “Everybody knowns if you ever went there you would fall off.” But he was an old country farmer, limited in education and very sure of himself. That brings up a bit of wisdom written nearly 20 millennia in the past: “When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put the ways of childhood behind me.” Hey y’all, let’s do science and not fiction.

  • ljk September 24, 2015, 16:36

    Whenever someone says there are no or very few (and far away) ETI, I often assume a deeper agenda beyond the mere statement of no scientific evidence for their existence. Often it is a religious reason, such as God only made one planet with life in the entire Universe and we are it.

    Or as in the case of Dr. Boruki with this following news item linked below, the lack of communicating aliens is an object lesson for humanity, as the perceived cosmic silence must mean a lot of dead worlds because they didn’t know how to or care enough to take care of their home planets:

    http://www.huffingtonpost.com/entry/nasa-borucki-climate-change_56036125e4b0fde8b0d14588?utm_hp_ref=tw

    So, according to Dr. Boruki, the negative results of humanity’s SETI efforts mean a lot of failed societies throughout the Milky Way galaxy because they did not properly respect their versions of Mother Nature. Oh, and he also says humanity will probably never achieve interstellar travel. So we better take care of Earth because there is nowhere else to go and no one else to visit.

    It may be an agenda with noble intent, but it is still an agenda with only one data point for science.

  • Brian McConnell September 24, 2015, 17:16

    The main thing these studies do is put constraints on the existence of civilizations that consume truly prodigious amounts of energy. However, consider a KIII civilization that, on average, only captures 10^-9 of each star’s energy output. This still works out to 10^17 Watts per sun-like star, and about 10^28 Watts across a galaxy. The luminosity of the star and IR excess would barely be affected, so even highly advanced and energy intensive civilizations would be invisible to these surveys unless they are intentionally transmitting signals.

    Related to Alex’s point, we’re already figuring out how to produce more economic output with less material and energy input. If you can dematerialize an economy at a rate of 5% per year, for example, that’s effectively the same thing as growing inputs at a similar rate (without the ecological implications of exponentially growing material and energy inputs). So I think we’re overestimating the energy requirements for advanced civilizations by a wide margin.

  • Joseph Voros September 24, 2015, 17:38

    If we look for cases of Dysonian macro-engineering, then we need not assume energy-wasteful activities, merely “artificial” ones, which would most likely be energy-efficient and perhaps even frugal, given long time frames for the activities. I continue to think that PGC54559 Hoag’s Object has such an unusual structure that it merits asking the question: “Is Hoag’s Object an artefact, i.e., an example of Galaxy-scale macro-engineering?”

    Several scenarios for how it came to have its morphology can be imagined. But, more importantly, there are several empirical observations which can be carried out (at least in principle) that would bear on this intriguing question. The rationale and suggested observations are examined here: http://arxiv.org/abs/1412.4011

    I really wish the SKA or the Breakthrough Listen initiatives would take a seriously closer look! It couldn’t hurt ;-)

    JV

  • Colin Wernham September 24, 2015, 17:48

    A KIII civilisation could easily (!) allocate resources to transmit bright signals directed at each local galaxy. They have nothing better to do…

  • DCM September 25, 2015, 4:33

    Spend less energy looking for such a civilization and more on becoming one.

  • NS September 25, 2015, 5:07

    To Harold Daughety, what you say of SF is largely true, but stories like “Solaris” and “Roadside Picnic” do recognize the limitations you point out. They focus on human reactions to the incomprehensibly alien, rather than trying to imagine what the aliens themselves might be.

  • Cambias September 25, 2015, 9:37

    It’s a conundrum. Most of the arguments advanced for why alien civilizations might not engage in large-scale engineering eventually turn into special pleading — assuming that whatever reason being put forth somehow has to apply to all civilizations in thousands of galaxies. Sure, most of them might, for example, prefer environmental conservation or virtual reality, but it only takes one for us to be able to see the results. The same applies to the self-destruction arguments.

    And yet, we don’t see them. This leads to three possibilities, of which two are disturbing or depressing. Either 1) we really are the first or only technological civilization — not just in our galaxy but in all the universe we can observe; 2) there is some kind of absolutely inevitable and deadly “Great Filter” in our future; or 3) we’re missing something.

    Option 3 is the only optimistic one: evidence for alien civilizations is out there plain to see and we’re just attributing it to natural processes. As I’ve asked before, why do They like to arrange the stars in their galaxies into spiral patterns? Or perhaps irregular galaxies are the work of intelligent operations.

    What other “natural” things could actually be signs of intelligence?

  • ljk September 25, 2015, 11:15

    Harold Daughety said on September 24, 2015 at 15:35:

    “I fear that science fiction is misleading: It is fiction, and all of humanity’s stories are about humanity. All sci-fi intelligent creatures, as presented in rational human stories, mirror humanity in a narrow slice of good an evil.
    We cannot imagine intelligence different from ours. I doubt we ever will be, and thus we will not recognize an ET if we ever meet one.”

    I reply:

    This is so very true. That is why the Polish science fiction author Stanislaw Lem was not a fan of Western SF, which for him was rather pedestrian and seldom took advantage of the potential power of the genre. That is also why the aliens in his stories such as Solaris and His Master’s Voice are atypical to SF and definitely not humanoid either in appearance or actions.

    Science fiction of course does have its place in the understanding of ETI. We still know so little that perhaps even the hoary old tropes of off-kilter looking humanoid aliens bent on conquering Earth and us are possible. All the more reason to ramp up SETI and start sending out interstellar probes.

    Speaking of being unable to imagine real alien life, a point was made by Rafael E. Nunez, a cognitive scientist from the University of California at San Diego who served as a consultant for the 2012 METI project known as The Last Pictures, where 100 images were placed on a silicon wafer and attached to the EchoStar 16 comsat in geosynchronous orbit. He told project head and artist Trevor Paglen that all aliens were the product of human imagination and therefore (to quote from my Centauri Dreams article on The Last Pictures):

    As the art project was under development, several people protested this method of talking to unknown intelligences in the far future. Prominent among them was Rafael E. Nunez, a cognitive scientist from the University of California at San Diego. Nunez sees all mathematics as subjective: Any mathematics on the Artifact cover would be as useless for proper interpretation as a pattern of random scratch marks to an alien species and even humans from a different culture.

    Nunez even gets to state his case in Chapter 4 of the book, mocking the statement made by the character of SETI scientist Ellie Arroway about “mathematics [being] the only truly universal language” in the 1997 film version of Carl Sagan’s only science fiction novel, Contact, (the ETI who contact humanity in Sagan’s work use the first one hundred prime numbers, which are digits divisible only by themselves and one, to get our attention, as no known natural phenomenon makes such a signal). Nunez goes further to say that aliens themselves, because “no actual forms of extraterrestrial aliens – dead or alive – have ever been documented empirically, such beings are, scientifically, nonentities…. Aliens, as we know them, are the product of human imagination.” The professor sums up his essay in the companion book that “if we want to believe that talking mathematics to aliens makes sense, we must humbly accept that we are anthropomorphizing, big time.”

    Full article here:

    https://www.centauri-dreams.org/?p=26171

    Harold then said:

    “The arguments I have most often heard elsewhere that denies intelligent life elsewhere in the galaxy are religious, that Man is the ultimate creation.”

    Speaking of religion, that could be one reason ETI may want to contact and/or visit humanity. Among the real reasons Europeans came to North and South America was to convert the natives to Christianity, to save their souls. And of course cheap labor for the nations taking over the New World.

  • ljk September 25, 2015, 11:18

    DCM said on September 25, 2015 at 4:33:

    “Spend less energy looking for such a civilization and more on becoming one.”

    Very little time and money are spent on searching for ETI. In fact far too little, which is why we haven’t found any alien intelligences yet, or any kind of alien life for that matter.

    Yes that Russian billionaire has given 100 million dollars to the effort. That is nothing short of a miracle for SETI, which has spent most of its existence scraping by and begging for time from professional astronomical observatories. And Americans spend far more than that on chewing gum each year – two billion dollars annually, to be exact.

  • CharlesJQuarra September 25, 2015, 13:58

    @Michael

    “There are two problems here that I can see, one trying to separate the CBR noise from the ‘signal’ would nigh on be impossible. And the second is that dark matter and energy are exactly that ‘dark’ we currently can’t detect it visually but only through the interaction via gravity. ”

    THz heat radiation signatures are several factors shorter/warmer than CBR. We still have to assume that even KIII abide to the 2nd Law. A sure telltale sign of a KII or KIII would be a heat signature in the THz range emitting an amount of waste heat comparable to that of a nearby star, which would imply that such power is being consumed at a fair distance from the star, presumably being beamed from a Dyson swarm sitting next to the star.

    See, the problem with these searches is that they’ve focused on finding Dyson shells (which look like a pure-IR signature, i.e: a single IR heat peak) but, at least to my understanding of their paper, they haven’t looked at Dyson swarms (which look like a star with a dual hot and a cold spectral peak)

  • Michael September 26, 2015, 9:10

    @CharlesJQuarra September 25, 2015 at 13:58

    ‘THz heat radiation signatures are several factors shorter/warmer than CBR. We still have to assume that even KIII abide to the 2nd Law. A sure telltale sign of a KII or KIII would be a heat signature in the THz range emitting an amount of waste heat comparable to that of a nearby star, which would imply that such power is being consumed at a fair distance from the star, presumably being beamed from a Dyson swarm sitting next to the star.’

    The average frequency of the CBR is around 150 GHz, but there are other frequencies in there which would make it noisy even in the THz range.

    http://map.gsfc.nasa.gov/media/ContentMedia/990015b.jpg

    ‘See, the problem with these searches is that they’ve focused on finding Dyson shells (which look like a pure-IR signature, i.e: a single IR heat peak) but, at least to my understanding of their paper, they haven’t looked at Dyson swarms (which look like a star with a dual hot and a cold spectral peak)’

    If they are true KII or III civilisations they would use all the energy of a star and a Dyson swarm with thin collectors around each swarm member would be better at collecting as much of the light as possible and therefore they would radiate more diffusely in infrared rather than a hot and cold spectrum emission. Either way to pick up such faint signals will be no mean feat.

    If was a member of a KIII civ I would go to the heart of the Galaxy as soon as possible and use the Black hole there, much more efficient for energy collection.

  • StanErickson September 30, 2015, 9:14

    Pardon me, but an alien civilization may not be just like a developed nation on Earth expanded in some dimension, such as energy consumption. Everything else in the civilization would have advanced as well, such as philosophy, and they would have decided on what purpose to accept during their continued existence. Examples:
    http://stanericksonsblog.blogspot.com